Anatomy 4.2 GIT Gross_Elevazo

Anatomy 4.2 Nov.9, 2011

Upper and Lower GIT-Gross Dr. Elevazo

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OUTLINE

1. UPPER GASTROINTESTINAL TRACT I. Oral cavity

A. Lips B.Vestibule C. Mouth Proper D. Temporomandibular Joint (TMJ) E. Palate F. Palate G. Tongue H. Salivary Glands

II. Pharynx III. Esophagus IV. Gastroesophageal joint V. Stomach

2. LOWER GASTROINTESTINAL TRACT I. Small Intestine

A. Duodenum B. Jejenum C. Ileum

II. Large Intestine A. Cecum B. Appendix C. Acending Colon D. Transverse Colon E. Descending Colon F. Sigmoid Colon G. Rectum H. Anal Canal III. Blood Supply IV. Venous Drainage V. Lymphatic Drainage

UPPER GASTROINTESTINAL TRACT

I. ORAL CAVITY

Beginning or commencement of GIT The GIT communicates to the outside through the oral cavity

From the oral fissures to the oropharyngeal isthmus (entrance to

the pharynx; formed on each side by the palatoglossal fold)

Consists of the lips, teeth, tongue, glands and muscles of mastication

A.LIPS

2 fleshy folds that surround the oral orifice

Covered on the outside by skin and lined on the inside by mucous membrane

Substance is made up by the orbicularis oris ms & muscles that radiate from the lips into the face, and contains labial blood vessels and nerves, CT and salivary glands o philtrum Shallow vertical grove seen in the midline on the

outer surface of upper lip o labial frenula Median folds of mucous membrane that

connect inner surface of the lips to the gums; cause problems in the fitting of artificial dentures

Food is chewed by the teeth and saliva from salivary glands facilitates the formation of bolus o Deglutition (swallowing) is voluntarily initiated

Figure 1. Oral cavity, hard palate, etc

Divided into two by teeth and maxilla

B.VESTIBULE

A slit-like space that communicates with the exterior thru the oral fissure when mouth is open and communicates with mouth proper behind 3

rd molar on each side when jaws are closed

o Lies between lips and cheeks (externally) o Lies between gums and teeth (internally)

Limited above and below by the reflection of the mucous membrane from the lips and cheeks to the gums

Lateral wall: cheek made up by the buccinator muscle and is lined with mucous membrane o Duct of the parotid salivary gland opens on a small papilla into

the vestibule opposite the upper 2nd molar tooth

C.MOUTH PROPER

When mouth is open you see the following: o Teeth o Palate o Tongue

Space posterior and medial to the upper and lower dental arches in front of the oropharyngeal isthmus

Borders: o Roof: hard palate (anterior) & soft palate (behind) o Floor: anterior 2/3 of the tongue and the reflection of the

mucous membrane from the sides of the tongue to the gum of the mandible (snell)

o Posterior/side: sublingual caruncle o Apex: opening of whartons duct o Posterior/lateral: sublingual fold o Laterally and anteriorly bounded by the maxillary and

mandibular alveolar arches housing the teeth Ducts of the submandibular and sublingual glands open onto

the floor of the mouth on either side of the frenulum

Muscles on the floor of the mouth

Table1. Muscles on the floor of the mouth

MUSCLE NERVE SUPPLY

Infrahyoids depresses the mandible

Geniohyoid C1 and C2 (ansa cervicalis)

mylohyoid, (R) & (L) Inferior Alveolar nerve (branch of mandibular division of trigeminal n.)

digastric, anterior belly mylohyoid branch of mandibular division of trigeminal n.

digastric, posterior belly facial nerve

Suprahyoid elevates the mandible

Stylohyoid facial nerve

Note: Action of muscle is always towards the origin of the muscle

Figure2. TMJ and its parts

The vestibule and oral cavity proper are separated by teeth and alveolar processes of mandible and maxilla

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D. TEMPOROMANDIBULAR JOINT (TMJ)

Lower oral cavity

Modified hinge type of synovial joint

Divided into upper and lower cavities by the articular disc o Composed of/articulation of the articular tubercle &

mandibular fossa of the temporal bone and the head or condyloid process of the mandible

o Upper joint is for gliding movements (retraction and protraction)

o Lower joint is for hinge movement (elevation, and depression) Mandible

- U-shaped with flat ramus (R & L) - Transmits vessels (arteries, veins and nerves) - Not fused in children 2 y/o - Mandibular foramen (inner) found in medial aspect which

contains inferior alveolar vessels and nerve to exit the mental foramen as mental vessels and nerves (anterior/outer)

o Covered with fibrocartilage o Nerve supply: auricular temporal and masseteric branches of

mandibular nerve o Movements that occur at the tmj: Retraction and protrusion (gliding joint):superior

compartment Elevation and depression (hinge joint): inferior compartment

LIGAMENTS OF THE TEMPOROMANDIBULAR JOINT o Lateral temporomandibular ligament Thickening of fibrous capsule Prevents TMJ from extending posteriorly

(normal: expect an anterior movement) o Sphenomandibular ligament Medial side of TMJ; primary passive support of tonus Provides primary support to TMJ Prevent jaws from falling down

o Stylomandibular ligament Behind and medial to TMJ; does not strengthen joint Thickening of fibrous capsule of parotid gland

Lateral temporomandibular ligament is intrinsic ligament, while the latter two, sphenomandibular and stylomandibular, are extrinsic ligaments

Muscles of Mastication o All are innervated by mandibular branch of CNV and all crosses

the TMJ Temporalis Elevates (anterior fibers) & retracts (posterior

fibers) mandible Masseter Elevates mandible Medial pterygoid Elevates mandible Lateral pterygoid Depresses and protracts mandible

o Buccinator muscle is an accessory muscle of mastication o Muscles that protract the mandible: Pterygoids (internal and external) Masseter Temporalis (anterior fibers)

o Muscles that retract the mandible: Temporalis (posterior fibers)

CLINICAL CORRELATON Excessive contraction of lateral pterygoid muscles can

dislocate the jaw anteriorly (most of the time, because head is in front of anterior tubercle) due to the intrinsic ligament and glenoid tubercle

In surgical correction, facial nerve and auriculotemproal branch of mandibular nerve are prone to damage

E.PALATE

Forms roof of the mouth; floor of nasal cavity

Separates oral cavity from nasal cavity and nasopharynx

Divided into two: o Hard Palate o Soft Palate

HARD PALATE o Anterior palate; continuous behind with the soft palate Formed by palatine process of maxillae and horizontal plates of palatine bones; bounded by alveolar arches

o Covered with mucous membrane o Space filled with the tongue when it is at rest o Foramina: Areas where dentist injects anesthesia o Incisive fossa: Slight depression post. To the central incisor

teeth o Incisive canals and foramina that open into the fossa contain

nasopalatine nerves o 2 openings found in the postero-lateral end: Greater palatine foramen (pl, foramina)

- Medial to the 3rd molar tooth; pierces the lateral border of the bony palate from which greater palatine vessels and nerve emerge

Lesser palatine foramen (pl, foramina) - Transmit lesser palatine nerves and vessels - Posterior to the greater palatine foramen, pierces the

pyramidal process of the palatine bone o Undersurface is covered by: mucoperiosteum, and possess

median ridge Has palatine raphe and transverse palatine folds

o Mucous membrane covered by stratified squamous epithelium (at posterior, possess many mucous glands)

Figure3. Palate and its parts

SOFT PALATE o A mobile fold attached at posterior of hard palate o Closes the nasopharynx o Covered on its upper and lower surfaces by mucous membrane o Contains aponeurosis, muscle fibers, lymphoid tissue, glands,

vessels and nerves o Laterally continuous with the wall of the pharynx Joined to the tongue by the palatoglossal arch and to the

pharynx by the palatopharyngeal arch Palatine tonsils masses of lymphoid tissue, one on each

side of the oropharynx; each lies in a tonsillar sinus (fossa), bounded by the palatoglossal and palatopharyngeal arches and the tongue

Uvula conical projection at its free posterior border in the midline


Table 2. Muscles of Soft Palate Muscle Main Action Innervation

Tensor veli palatini Tenses soft palate and opens the pharyngotympanic tube during swallowing and yawning

Medial pterygoid nerve (a branch of mandibular nerve CN V3)

Levator veli palatini Elevates soft palate during swallowing and yawning

Pharyngeal branch of vagus nerve (CN X) via

pharyngeal plexus

Palatoglossus Elevates posterior part of tongue and draws soft palate onto tongue

Palatopharyngeus Tenses soft palate and pulls walls of pharynx during swallowing

Musculus uvulae Shortens uvula and pulls it superiorly

F. TEETH

Functions: o incise, reduce, mix with saliva, and grind during mastication o support and protect the oral cavity articulation(speech)

There are two sets of teeth o Deciduous teeth (temporary) / milk teeth o Permanent teeth

DECIDOUS TEETH OR MILK TEETH o Begin to erupt about 6 months after birth o Completely erupted by the end of second year Central incisors (6-8 mos) Lateral incisors (8-10 mos) First molars (1 yr) Canines (18 mos) Second molars (2 yrs)

o There are 20 in number (5 on each side of the jaw) 4 incisors 2 canines 4 molars in each jaw

Teeth on the lower jaw usually appear before those on upper jaw Lower central incisor first to erupt (temporary set) around 6 months PERMANENT TEETH

o Begin to erupt at 6th year o LAST tooth to erupt is the 3rd molar (17-30th yr) o There are 32 in number First molars (upper-6 yr) Central incisor (7 yr) Lateral incisor (8 yr) First premolars (9 yr) Second premolars (12 yr) Third molars wisdom teeth (17-30 yr)

o Completed by age of 12yo Teeth on the lower jaw usually appear before those on upper jaw Lower first molar first to erupt (permanent set) It is connected to the bone via special type of fibrous joint called

GOMPHOSIS or Dento-alveolar syndesmosis

PARTS OF A TOOTH

o Crown part that protects beyond the gums (it is above the gum/gingival)

o Neck constricted portion between crown and root o Root embedded in maxilla and mandible (alveolar

periosteum); attached to alveolar process of mandible or maxilla

o Root canal transmits nerves and vessels to and from the pulp cavity through the apical foramen

o Apical foramen transmits blood vessels, lymph and nerves. It is the opening at each root

o Pulp cavity internal tooth portion Odontoblast, a single layer of cells, surround the dentin layer Surrounded by dentin (the most sensitive part of the teeth) Contains blood vessels, lymph and nerves Protected by enamel at area of crown Protected by cementum at area of root

o Alveolar periosteum - anchors the teeth

Figure 4. Parts of the teeth

Note: - The only sensation transmitted in the teeth is pain - Incisors have sharp a sharp edge for biting; Molars and Premolars are

for grinding; Canines have rounded edge for tearing and for cosmetic purposes (they maintain the shape of the face of an individual)

- Tongue (medially) and cheeks (laterally) help keep the food in between teeth

G. TONGUE

Mobile mass of voluntary striated muscles covered with mucous membrane

Anterior two thirds lies at mouth

Posterior lies at pharynx

Muscles; attach it to styloid process and soft palate above, and to mandible and hyoid bone below

Also used in phonation

Arises from floor of mouth PARTS OF THE TONGUE

Roof inferior, relatively fixed part attached to the hyoid and mandible and in proximity to the geniohyoid and mylohyoid muscles; it is the pharyngeal portion of the tongue

Body remaining part: anterior 2/3

Apex pointed anterior part of the body

Dorsum posterosuperior surface of the tongue, which includes a v-shaped groove(terminal sulcus), the apex of which points posterior to the foramen cecum

Upper surface of the tongue o Fibrous septum divides tongue in left and right halves o Sulcus terminalis divides mucous membrane of the upper

surface of tongue into posterior thirds (pharyngeal part) and anterior 2/3 (oral part); apex directed posteriorly

o Foramen Cecum a small pit that marks the apex of the sulcus projecting backward; remnant of thyroglossal duct (where fetal thyroid starts to develop)

Anterior 2/3 of the tongue (upper surface) o Papillae increase the area of contact between the surface of

the tongue and the contents of the oral cavity; for proper handling of food


o Filiform papillae with tapered ends, most abundant, forms small conical projections and are whitish in color due to thickness of cornified epithelium (keratinized, no taste buds)

o Fungiform papillae less numerous, scattered on sides and apex of tongue, mushroom-shaped, reddish tinge due to vascular connective tissue core; contain taste buds

o Circumvallate or vallate papillae 8-12 in number, situated in a row in front sulcus terminalis; surrounded by circular furrow, where taste buds lie; surrounded by deep moat-like trenches, into which the ducts of serous lingual glands of von Ebner open; epithelium rich in tastebuds

o Foliate papillae found at the posterior end of the margin of the anterior 2/3 of tongue, underdeveloped in humans; well-developed in rodents

Figure5. Taste buds

Posterior third of the tongue o Devoid of papillae BUT contains lingual tonsil (small nodules of

lymphoid tissue) which makes the mucosa covering the pharyngeal surface of the tongue irregular in contour

o Vallecula depression of tongue where foreign bodies such as fish bones may lodge

Inferior portion of the tongue (when tongue is up and back) o Lingual Frenulum a fold of mucous membrane that connects

undersurface of tongue to floor of mouth o Plica fimbriata fringe fold formed by mucous membrane,

lateral to deep lingual vein. o Deep lingual veins found in between the fimbriated fold and

frenulum, seen thru mucous membrane; responsible for rapid absorption of drugs taken sublingually e.g nitroglycerine for MI.

o Sublingual caruncle papilla on each side of the lingual frenulum marking the opening of the submandibular gland or Whartons duct

o Sublingual fold (or plica sublingularis) low fold mucous membrane beneath the tongue which marks the site of the sublingual gland

Figure 6. Floor of Mouth and Vestibule

CLINICAL CORRELATON

If there is lesion in the peripheral nerve, when you stick out your

tongue you expect it to go to the direction of the lesion

Table3. Muscles of the Tongue MUSCLE ACTION NERVE SUPPLY

Extrinsic

Genioglossus fan-shaped

acting bilaterally: depress central part of tongue, acting unilaterally:

deviate tongue toward contralateral side

Hypoglossal nerve

Hyoglossus thin, quadrilateral muscle

depresses tongue, pulling its sides inferiorly, aids in retrusion

(retraction)

Styloglossus small short muscle

retrudes the tongue and curls its sides, acting with genioglossus

creates a trough during swallowing

Palatoglossus primarily pharyngeal

elevates tongue, pulls down soft palate

Pharyngeal plexus

Intrinsic muscles not attached to bone

Superior longitudinal muscle thin layer

deep to mucous membrane on dorsum

of tongue

curls apex of tongue, makes dorsum of tongue concave longitudinally

Hypoglossal nerve

Inferior longitudinal muscle narrow bands

close to inferior surface

curls apex of tongue inferiorly, makes dorsum of tongue convex

superior and inferior makes tongue short and thick in retracting

the protruded tongue

Transverse muscle lie deep to superior longitudinal muscle

narrows and increase the height of tongue

Vertical muscle runs inferolaterally from dorsum of tongue

flattens and broadens the tongue

transverse and vertical makes tongue long and narrow

Figure 7. Muscles of the Tongue

Note: - ALL muscles of tongue are supplied by hypoglossal nerve EXCEPT the

palatoglossus ms, which is supplied by the pharyngeal plexus - The pharyngeal plexus is from vagus n., glossopharyngeal n., and

sympathetic n.

Table 4. Taste Buds

GENERAL SENSATION TASTE

Anterior 2/3 Lingual n. (mandibular

br. of trigeminal n)

Chorda tympani (facial n.) EXCEPT vallate

papillae

Posterior 1/3 Glossopharyngeal n.

posteromedial aspect partly innervated by Vagus nerve

Taste buds of the circumvallate or vallate papillae receive innervation from nerves that supply posterior 1/3 of the tongue (CN IX)


Arterial Supply of Tongue o Dorsal lingual arteries posterior part (root) of the tongue

& send tonsillar branch to the palatine tonsil o Deep lingual artery anterior part of the tongue;

communicates with the dorsal a. Near the apex of the tongue o Sublingual artery sublingual gland & floor of the mouth

Venous Drainage of Tongue o Dorsal lingual veins accompany the lingual a. o Deep lingual veins begin at the apex of the tongue & run posteriorly beside the lingual frenulum to join the sublingual vein All lingual veins terminate, directly or indirectly, in the IJV

(continuation of sigmoid sinus)

Lymphatic Drainage AT the posterior 1/3 and the medial anterior 2/3 of the

tongue, the lymphatic vessels criss cross to the other side

o Superior deep cervical lymph nodes posterior 1/3 o Inferior deep cervical lymph nodes medial anterior 2/3 o Submandibular lymph nodes lateral anterior 2/3 o Submental lymph nodes apex of the tongue & frenulum o ALL eventually drain into the deep cervical lymph node

Clinical Correlation

Carcinomatosis involving the poeterior 1/3 of the tongue, metastasis to tboth side is very early because of the criss crossing of the lymphatic vessels.

H. SALIVARY GLANDS

Secrete saliva, which keeps mucous membrane of mouth moist, lubricates food during masctication, begins digestion of starches, serves as an intrinsic mouthwash, & plays role in prevention of tooth decay & in the ability to taste

Named according to where it is found o Mucosa of cheek- Buccal glands o Mucosa of Lips- Libel gland

Table 5. Salivary Glands

SALIVARY GLAND LOCATION ARTERIAL SUPPLY;

VENOUS DRAINAGE

Parotid glands - largest of the major

salivary glands - duct is called Stensens duct

gap between ramus of mandible & styloid & mastoid processes

of temporal bone

external carotid a. & superficial temporal a.; retromandibular

veins.

Submandibular gland along body of

mandible submental a.; submental v.

Sublingual gland - smallest & most

deeply situated

floor of the mouth between mandible &

genioglossus ms.

sublingual a. & submental a.

Figure 8.1 Salivary Glands

Figures 8.2 Salivary glands

II. PHARYNX

From base of skull to lower cricoid cartilage (C6 level) Behind the nasal cavities, the mouth and the larynx

A musculomembranous tube

Funnel-shaped; common passage of food and air

Upper, wide-end lie under the skull Lower, narrow end becomes continuous with esophagus opposite

C6.

Has musculomembranous walls, which is deficient anteriorly (replaced by posterior nasal apertures, oropharyngeal isthmus and inlet to larynx)

Pharynx connects with 7 cavities anteriorly o (R) & (L) nasal cavities (choanae/nares) o (R) & (L) eustachian tube (lateral) o Oral cavity (front) o Laryngeal cavity o Esophagus (below)

A.MUCOUS MEMBRANE

Continuous with the nasal cavity, mouth and the larynx

Continuous with the tympanic cavity thru the auditory tube

Upper part, pseudostratified ciliated columnar epithelium Lower part, stratified squamous epithelium

Transitional zone where the two areas come together

B. FIBROUS LAYER

Pharyngobasilar fascia strong internal fascial lining of the constrictor muscles o Between the mucous membrane and the muscle layer o Thicker above, strongly connected to the base of the skull o Becomes continuous with the submucous coat of the

esophagus Buccopharyngeal fascia thin external fascial lining of the

pharyngeal muscles Pharyngeal aponeurosis: covers the the pharyngeal muscle which

if extends to esophagus, will be the muscularis mucosa of esophagus


C. MUSCULAR LAYER

Table 6. Pharyngeal Muscles

MUSCLE ACTION NERVE SUPPLY

External circular

Super constrictor aids soft palate in closing off nasal pharynx, propels bolus downward

Pharyngeal plexus

Middle constrictor propels bolus downward

Inferior constrictor

Cricopharyngeus sphincter at lower end of pharynx; prevents the swallowing of air

Internal longitudinal

Stylopharyngeus elevates larynx during swallowing

CN IX

Salpingopharyngeus elevates pharynx Pharyngeal plexus Palatopharyngeus elevates wall of pharynx, pulls

palatopharyngeal arch medially

ALL pharyngeal ms are innervated by pharyngeal plexus EXCEPT stylopharyngeus, which is innervated by the glossopharyngeal n

Muscularis externa is always made up of inner circular and outer longitudinal muscle layer but the pharynx is made up of inner longitudinal and outer circular muscle layer

The posterior fiber of the superior constrictor muscles works hand-in-hand with the soft palate in closing the nasopharynx when swallowing

D.PARTS OF PHARYNX

NASOPHARYNX or EPIPHARYNX o Posterior to nasal cavity/chonae o Purely respiratory in function; only allows passage of air o Mucosa lined with respiratory epitheleum o Anterior: choanae/posterior nares o Posterior: base of skull (c1/atlas) o Roof : supported by the sphenoid and occipital bone; where

pharyngeal tonsils can be seen o Floor: upper surface of soft palate; opening is called pharyngeal

isthmus o Lateral wall : contains opening of the Eustachian/

pharyngotympanic tube and mucosal elevations and folds covering the tube and the adjacent muscles Salpingopharyngeal fold desends from the tubal elevation

and overlies salpingopharyngeus muscle Torus levatorius broad elevation emerging from under the

tube; overlies levator veli palitini muscle Tubal tonsil (important structure of the nasopharynx from

Dr. Elevazo) - lymphoid tissue around opening of the tube; should atrophy during puberty

Sensory nerve supply (nasopharynx): maxillary nerve (V2)


Pharyngeal tonsils, when enlarged, are called adenoids which

can block the Eustachian tube opening

Tubal tonsil may cause otitis media when it blocks the opening of the Eustachian tube

OROPHARYNX o Digestive function; stratified squamous epithelium o Behind the soft palate to hyoid between laryngeal inlet and soft

palate Superiorly: bounded by soft palate Inferiorly: base of the tongue Laterally: palatoglossal and palatopharyngeal arches

o Waldeyers ring = pharyngeal + palatine + lingual tonsils + tubal tonsils Lingual tonsils anteroinferior part of ring Palatine tonsils (important structure of the oropharynx

from Dr. Elevazo) most frequently infected; together with tubal tonsils are found on the lateral wall of the oropharynx

Pharyngeal tonsils posterior part of ring; hypertrophic in children but atrophies in puberty

o Valecula depression or space between posterior 1/3 of tongue and epiglottis where fish bone may lodge

o Median glossoepiglottic fold: fold in midline of base of the tongue

o Oropharyngeal isthmus: interval between palatoglossal arches Sensory nerve supply (orophraynx): glossopharyngeal nerve

LARYNGOPHARYNX OR HYPOPHARYNX o Behind laryngeal inlet o Posterior to the larynx, from superior border of epiglottis and

the pharyngoepiglottic folds to the inferior border of the cricoid cartilage, where it narrows and becomes continuous with the esophagus

o Cricopharyngeus muscle acts as a sphincter that prevents the air to pass in esophagus Posteriorly, related to bodies of C4 thru C6 vertebrae Behind the laryngeal inlet or aditus (formed by epiglottis:

aryepiglottoc fold and interarytenoid notch) o Piriform fossa groove in the mucous membrane on each side

of laryngeal inlet, behind the cuneiform and corniculate tubercles and between cricoid and thyroid cartilage lamina

Where foreign bodies such as fish bone may lodge when fish bone is not found at the valecula

Sensory nerve supply (laryngopharynx): internal laryngeal branch of the vagus nerve

E.ARTERIAL SUPPLY

Upper part o Ascending pharyngeal a. o Ascending palatine and tonsillar branches of facial artery o Maxillary artery o Lingual artery

Lower part (including cricopharyngeus ms) o Superior thyroid artery

Figure 9. Blood Supply of Pharynx


Figure 10. Parts of Pharynx

E. VENOUS DRAINAGE

External palatine vein (paratonsillar vein) Retromandibular v. union of superficial temporal and maxillary

veins o Drain into pharyngeal venous plexus into internal jugular v.

E. LYMPHATIC DRAINAGE

Directly into superior cervical group of nodes (runs along IJV)

Indirectly into retropharyngeal or paratracheal nodes then into deep cervical nodes

All eventually drain into deep cervical lymph nodes

Figure 11. Venous and lymph drainage of pharynx

III. ESOPHAGUS Extends From Lower border of cricoids cartilage (C6) to are where

it inserts at cardia of stomach at level of (T11) Goes down and enters the super and inferior mediastinum of

thorax

Enters esophageal hiatus(T10) to enter cardia of stomach (T11)

Conduct food from the pharynx into the stomach

A muscular collapsible tube 10 in. (25 cm) long

Joins pharynx to stomach

Greater part lies within the thorax Covered anteriorly and laterally by peritoneum

Anteriorly : related to posterior of LEFT lobe of liver

Posteriorly : related to LEFT crux of diaphragm

Divided into 3 parts: cervical, thoracic and abdominal Enters the abdomen via right crux of diaphragm

A. THREE PORTIONS OF ESOPHAGUS

Cervical o Anterior: trachea o Posterior: cervical vertebrae o Lateral: thyroid gland, carotid sheath o In groove between trachea and esophagus: recurrent laryngeal

nerves

Thoracic (thorax)

o Anterior: trachea, (L) recurrent laryngeal nerve, (L) principal bronchus (T5) & pericardium Left atrium(below thoracic bifurcation)

o Posterior: bodies of upper thoracic vertebrae, thoracic duct, azygos veins,hemiazygous vein, (R) posterior intercostals arteries, descending thoracic aorta

o Laterally on Right: mediastinal pleura ,terminal branch of azygos vein (T4) and parietal pleaura

o Left: above tracheal bifurcation: ascending portion of left subclavian artery, aortic arch (T4), thoracic duct, parietal pleura

o Below tracheal bifurcation: descending aorta o T8: descending aorta lies beneath esophagus

Abdominal

o Anterior: inferior surface of (L) lobe of liver o Posterior: (L) crus of diaphragm

B. COURSE OF ESOPHAGUS

In the neck, lies in the midline

In the thorax, it is to the left, passing thru superior then posterior mediastinum

At the level of sternal angle (T4-T5), aorta pushes esophagus back to midline

At t10, passes on opening of right crux of the diaphragm, then after course, joins stomach at right side 7th left costal cartilage and T11

Note: - (L) vagus n. Anterior to esophagus, (R) vagus nerve Posterior to

esophagus [L.A.R.P.] - Peristalsis wave-like contraction of the muscular coat, propels

the food onward - Phrenicoesophageal ligament: attach esophagus to margins of

esophageal hiatus in diaphragm

C. FOUR CONSTRICTION AREAS

Where foreign bodies may lodge

Offer resistance in passageway 1. C6 : caused by cricopharyngeus (superior esophageal sphincter)

/ cricopharyngeal constriction -at junction between pharynx and esophagus -When it contracts- prevents entry of air when swallowing

2. T4 : arch of the aorta / bronchoaortic constriction 3. T5 : level of (L) main bronchus / bronchoaortic constriction (2 and 3)- 4. T10 : esophageal hiatus of diaphragm / diaphragmatic

constriction /inferior esophageal sphincter


If you ingest acid, these constriction areas will obtain the most damage

During endoscopy, these areas are most common sites of injury


Figure12. Location of Esophagus

D. MUSCULAR LAYER OF ESOPHAGUS

Upper 3rd: Skeletal

Middle 3rd: Mixed

Lower 3rd:Smooth o Inner circular o Outer longitudinal

Note: - Trachea (trachealis) ms and anterior esophagus forms the

common party wall (above and below isthmus of thyroid) - In children, trachea is pencil size; esophagus is prone to damage

during a tracheostomy

E. BLOOD SUPPLY

Cervical part: inferior thyroid a. (r & l thyrocervical, sca)- branches of thyrocervical trunk from subclavian artery

Thoracic part : esophageal arteries (branches of descending aorta) & branches of bronchial arteries (2 on left 1 on right), right posterior intercostal arteries

Abdominal part :comes mainly from left gastric a. (br. Of celiac a.) And recurrent branch from left inferior phrenic a.

+++may also come from short gastric artery from splenic artery that supplies fundus of stomach

F. VENOUS DRAINAGE

Drain into the left gastric vein, tributary into the left gastric nodes o Cervical part: (R) & (L) inferior thyroid veins to (R) & (L)

brachiocephalic veins o Thoracic part: azygos and hemiazygos v. o Abdominal part:primarily to portal venous system via left

gastric vein (portocaval anastomoses) on lower 1/3 of esophagus

o +++submucosal venous plexus penetrate entire wall of esophagus forming peri-esophageal venous plexuses


Liver cirrhosis progressive destruction of hepatocytes, which are replaced by fibrous tissue; fibrous tissue surrounds intrahepatic vessels, impeding the circulation of blood; there is then retrograde flow of blood; submucosal plexuses becomes dilated and tortuous causing varices which are prone to hemorrhage-> bleeding esophageal plexuses. ++obstruction of portal vein because of alcoholic cirrhosis of liver will cause retrograde flow of blood back from portal vein, left gastric vein, peri-esophageal sinuses and back to submucosal venous plexuses producing esophageal varices> liver cirrhosis

G. PORTAL-SYSTEMIC OR PORTO-CAVAL ANASTOMOSES

Communication between the portal and systemic systems; become important when direct route (hepatic veins to IVC) becomes blocked

Table 7. Portal System

PORTAL SYSTEM SYSTEMIC SYSTEM

A

esophageal branches of (L) gastric vein

esophageal branches of azygos veins

when abnormally dilated: esophageal varices

B

superior rectal veins continuing as the inferior mesenteric veins

inferior and middle rectal veins

when abnormally dilated: hemorrhoids

C

paraumbilical veins connected to the (L) branch of the portal vein

superficial epigastric veins

when dilated: caput medusae

D twigs of colic veins (veins of

descending & ascending colon, duodenum & pancreas)

retroperitoneal veins (renal, lumbar & phrenic veins)

Figure 13. Portal-system

H. LYMPH DRAINAGE

Follows arteries into the left gastric nodes Starts below the tracheal bifurcation

Cervical: inferior deep cervical nodes in lower portion of IJV

Thoracic: o Above carina: o Anterior: paratracheal and superior and inferior

tracheobronchial nodes o Posterior: posterior mediastinal & intercostal nodes,

collectively called posterior parietal nodes o Below carina: superior phrenic nodes

Abdominal: left epigastric and celiac nodes draining to cisterna chyli then to thoracic duct


Summary of lymphatic drainage( Dr. Elevazo):

Cervical portion: nodes on lower portion of Internal jugular vein

and find its way on thoracic duct (left) and Right lymphatic duct

(right)

Abdominal: lymphatic channels emptying on left gastric nodes>

efferent on left gastric nodes empty on ciliac nodes> efferent on

ciliac nodes empty on intestinal trunk( major tributary of cysterna

chylli/thoracic duct together with aorta at level of T12/ L1)

Thoracic: Landmark is tracheal bifurcation:

o Above: ant wall: tracheobronchial and paratracheal nodes

o Posterior wall: both above and below: post mediastinal

bifurcation

o Below tracheal bifurcation: phrenic nodes

o Right: right lymphatic duct

o Left: thoracic duct

I. NERVE SUPPLY

Anterior and posterior epigastric nerves (vagi)

Sympathetic branches of the thoracic part of the sympathetic trunk(S4-S6)

Postganglionic sympathetic: follow branchings of blood vessels of cervical, thoracic and abdominal portions

Parasympathetic : vagus nerve o Cervical (R) & (L) vagus nerves and (R) & (L) recurrent

laryngeal nerves o Thoracic - Above tracheal bifurcation: (R) & (L) vagus nerves

and (L) recurrent laryngeal nerve - (R) recurrent hooks around the subclavian artery and does

not get in contact with the esophagus - Below tracheal bifurcation: esophageal plexus: 1-2 cm above

esophageal hiatus unite to form: (L vagus) anterior & (R vagus) posterior vagal trunks (LARP) + sympathetic nerves

Abdominal anterior and posterior vagal trunks

IV. GASTROESOPHAGEAL JUNCTION Also known as cardia, Z-line or esophagogastric junction lies in

left of T11 and left 7th

costal cartilage

Transition from stratified squamous to simple columnar epith.at area of cardia of stomach

Has specialized smooth mucles fibers at esophagogastric vestibule which is a thickening of lower portion of esophagus to cardia, about 2cm above esophageal hiatus and with thickened smooth muscle

Contain inferior or lower esophageal sphincter (LES) o Angulation o Rosette arrangement o Sphincteric effect of contraction of diaphragm o Prevents regurgitation of food from stomach to esophagus

Netter: 1-2 cm above esophageal hiatus at area of cardia> muscle thickening called esophagogastric vestibule which contains specialized smooth muscle fiber called inferior esophageal sphincter

Moore: contraction of diaphragm prevents regurgitation of food from stomach into esophagus

A. GASTROESOPHAGEAL SPHINCTER

NOT an anatomic sphincter BUT a physiologic sphincter because of circular layer of smooth muscle

Its tonic contraction prevents regurgitation of stomach contents into esophagus

Closure of this is under vagal control

o Gastrin augment closure and dilatation o Secretin, cholecystokinin, and glucagons reduce response

Note: - No anatomical sphincter exists at lower end of esophagus

Clinical Correlation: if this area does not contract well, the patient will experience reflux esophagitis

Other factors that prevent regurgitation of food: 1. Angle of junction between esophagus and stomach 2. Rosette arrangement 3. Sphincteric effect of diaphragm

V. STOMACH

Expanded part of the digestive tract between the esophagus and small intestine.

Acts as a food blender and reservoir

Its main function is Enzymatic Digestion

Can hold 2-3 liters of food

Gastric juice converts food into a semi-liquid mixture, chime Position and Shape o Size shape and position can vary markedly in persons of

different body types. o Found in left hypochondrium and epigastric area and may

extend to area of umbilicus o In supne position, it commonly lies in the upper right and left

quadrants o J shaped, and vertical (in tall,thin person) o Fixed at both ends, but mobile in between

Figure14. Parts of the Stomach

A. Parts of the Stomach

Cardia part that surrounds the cardial or cardiac orifice, the superior opening or inlet of the stomach o Receives distal end of esophagus o Posterior to 6th (L) costal cartilage, 2.4cm from the median

plane at the level of T11 vertebra

Fundus of the stomach o Dome-shaped; usually full of gas o Related to the left dome of the diaphragm o The Cardial Notch is between the esophagus and the fundus o Projects upward and to left of cardiac orifice o In supine position, fundus usually lies posterior to the L 6th rib

in the plane of MCL


Body of the Stomach o Extends from level of cardiac orifice to level of inciscura

angularis o Largest region of the stomach o No definite bifurcation from body to pylorus o Incisura angularis (angular inscisure) constant notch in lower

part of the lesser curvature; (L) of the midline; junction of body and pyloric part of stomach

Pyloric Part funnel-shaped region; lies at the transplyoric plane o Pyloric antrum wide part; extends from incisura angularis to

the pylorus; narrows to form the pyloric canal o Pyloric canal narrow part; ends at pyloric sphincter o Pylorus sphincteric region Thickening of inner circular muscle Tubular part of stomach containing pyloric sphincter, thick

muscular wall of pylorus which controls the rate of discharge of stomach contents into duodenum

Recognized externally as slight constriction on stomach Lies on (r) side

o Pyloric orifice outlet of the stomach

B. Openings of the Stomach

Cardiac o Where esophagus enters stomach o Has physiologic sphincter only

Pyloric o Formed by pyloric canal o Thicker muscular coat (circular) o With both anatomic and physiologic sphincter

C. Curvatures of the Stomach

Greater curvature o From left of cardiac orifice, over dome of fundus, to pylorus and

along left border of the stomach to the pylorus o Much longer than lesser curvature o It passes inferiorly to the left from the junction of the 5th ICS

and MCL, then curves to the right, passing deep to the 9th or 10th left cartilageas it continues medially to reach the pyloric antrum

Lesser curvature o Shorter, concave, right border of stomach o From cardiac orifice to pylorus o Angular Incisure most inferior part of the curvature, indicates

the junction of the body and pyloric part of the stomach o Suspended from liver by lesser omentum

D. Omenta

Mobile Could adhere to possible infection

Temporarily prevents spread of infection (not useful in children below 2yo since their omenta is not yet well developed)

Greater omentum from greater curvature of the stomach to other viscera; has 3 parts: o Gastrocolic ligament colon o Gastrosplenic ligament spleen o Gastrophrenic ligament diaphragm

Lesser Omentum suspends the lesser curvature os the stomach from the fissure of the ligamentum venosum and the porta hepatic on the undersurface of the liver: o Hepatogastric or Gastrohepatic ligament connects lesser

curvature of the stomach to the liver; membranous portion of lesser omentum; proximal part ; thicker

o Hepatoduodenal ligament connects the proximal part of the duodenum to the liver; thickened free edge of the lesser omentum; conducts the portal triad: portal vein, hepatic artery and bile duct; distal part; narrower

Stomach bed on which stomach rests when person is in supine position, is formed by the structures forming the posterior wall of the omental bursa o from superior to inferior: Left dome of diaphragm Spleen Left kidney and suprarenal gland Splenic artery Pancreas Transverse mesocolon

E. Blood Supply

From branches of celiac artery/trunk

Left gastric artery o Directly from celiac artery o Supplies lower 1/3 of esophagus and upper right (lesser

curvature) of stomach

Right gastric artery o From hepatic a., a branch of celiac trunk o Supplies right portion of thelesser curvature of stomach

Short gastric artery o From splenic a., a branch of celiac trunk o Supplies fundus

Left gastroepiploc (gastro-omental) artery o From splenic artery o Supplies stomach along the left portion of the greater

curvature

Right gastroepiploc (gastro-omental) artery o From gastroduodenal branch of the common hepatic artery o Supplies right portion of the greater curvature

Figure 15. Blood Supply of stomach

F. Venous Drainage

Right and Left Gastric veins o Drain directly into hepatic portal vein (at neck of pancreas, L1,

L2)

Short gastric and Left gastroepiploic or gastro-omental veins o Join splenic vein, which drains into the superior mesenteric vein

(SMV) to form the hepatic portal vein

Right gastroepiploic or gastro-omental vein o Drains into the superior mesenteric vein

Note: - Portal vein is formed by the union of superior mesenteric vein

and splenic vein. - Prepyloric vein: ascends over pylorus to drain to right gastric

vein; being use by surgeons to identify the pylorus


Figure 16. Venous drainage of stomach

G. Lymph Drainage

Gastric Lymphatic Vessels follow the arteries along the greater and lesser curvatures to: o Left and right gastric nodes o Left and right gastroepiploic nodes o Short gastric nodes All lymph from stomach eventually passes toceliac

nodeslocated around root of celiac artery on posterior abdominal wall

Celiac node cysterna chili thoracic duct Clinical Correlation

In carcinoma of the stomach, the spread of cancer is hard to contain because lymph nodes are shared

H. Nerve Supply

Parasympathetic vagus nerve o Secretory nerve fibers to glands and muscles o Anterior vagal trunk anterior surface of stomach, pyloric

branch to pylorus (Left) o Posterior vagal trunk posterior (main) and anterior surface

of stomach (Right)

Sympathetic celiac plexus / thoracic splanchnic nerves o Pain transmitting nerve fiber o Greater splanchnic T6-T9 o Lesser splanchnic T10-T11 o Least splanchnic T11

H. Histology of the Stomach

Mucous membrane o Thick and vascular o Rugae numerous folds of the mucous membrane of stomach,

longitudinal in direction o Magenstrasse Pliable, linear rugal folds or groove of the gastric mucosa

along the lesser curvature that is the route food and liquids tend to take in moving toward the pylorus

Has no oblique muscles Bounded externally by the gastrohepatic ligament Frequent site of most spontaneous gastric rupture (peptic

ulcer formation), due to the lesser curvature's lower distensibility

Muscular walls o Oblique innermost coat, loop over fundus and pass down

along anterior and posterior walls, parallel with lesser curvature; not seen in curvatures

o Inner circular encircle body of stomach, thickened at pylorus, few in the fundus, forms the pyloric sphincter (middle circular muscle layer) which regulates flow of chime from stomach to first part of duodenum

o Outer longitudinal most superficial, concentrated along curvatures

Visceral peritoneum o completely surrounds the stomach o leaves lesser curvature as lesser omentum o leaves greater curvature as gastrosplenic omentum and greater

omentum

LOWER GASTROINTESTINAL TRACT

II. SMALL INTESTINE

Greatest surface area (22 ft. long)

From the pylorus of the stomach to the ileocecal junction where the ileum joins the cecum (first part of the large intestine)

Pyloric part empties in duodenum and pylorus regulates duodenal admission

Where the greater part of digestion and food absorption takes place

Figure 17 . Three Parts of small intestine: Duodenum, Jejunum, Ileum

A.DUODENUM

First part of the small intestine and the shortest one

10 in. (25 cm) long

Also the widest and most fixed part

C-shaped tube that course around the pancreas and joins the stomach to the jejunum

Runs from pylorus on right side to the duodenojejunal junction /flexure (an acute angle) on the left

Junction occurs at the level of the L2 vertebra, 2-3 cm to the left of the midline

Receives the openings of the bile and pancreatic ducts

Situated in the epigastric and umbilical regions

First part is smooth; remainder is thrown into circular folds called theplicae circulars

Most of the duodenum is fixed by peritoneum to structures on the posterior abdominal wall and is considered partiallyretroperitoneal except the 1st inch that is intraperitoneum

Parts of the Duodenum o SUPERIOR: FIRST PART 2 inches (5 cm) long ,Lined by smooth mucous membrane Ascends from the pylorus and is overlapped by the liver and

gallbladder runs upward and backward on the right side of the first

lumbar vertebra (L1) Lies on thetranspyloric plane


Anterior aspect covered by peritoneum but posterior part is bare, except for the ampulla

Proximal part has thehepatoduodenal ligament attached superiorly and the greater omentum attached inferiorly

Note: - AMPULLA or DUODENAL BULB - it is the only portion of

the duodenum that is mobile since it is suspended by a mesentery. The rest of the duodenum is retroperitoneal, applies to the first inch of the duodenum

Table7 . Boundaries of superior duodenum

Anterior quadrate lobe of the liver and gallbladder

Posterior lesser sac, gastroduodenal artery, bile duct portal vein, IVC

Superior epiploic foramen

Inferior head of the pancreas

o DESCENDING: SECOND PART Longer than superior part 7- 10 cm long and descends along

the right sides of L1 L3 vertebra Runs vertically downward in front of the hilum of the right

kidney at the right side of L2 and L3 Appearance ofplicaecirculares or valves of Kerckring,Entirely

retroperitoneal Peritoneum reflects from its middle third to form the double

layered mesentery of the transverse colon, the transverse mesocolon

Plicaecirculares or Valves of Kerckring: Increase the surface area of small intestine for absorption

Hepatopancreatic ampulla or Ampulla of Vater: Formed where the bile duct and pancreatic duct enter the posteromedial part of the second duodenum, opening into the duodenal papilla

Major duodenal papilla: Small, rounded elevation where the bile duct and the main pancreatic duct pierce the medial wall of the duodenum

Minor duodenal papilla: Where the accessory pancreatic duct opens. This part of the duodenum is not present if the pancreatic duct has no accessory part

Table 8. Boundaries of superior duodenum

Anterior fundus of the gallbladder, right lobe of the liver, transverse colon, SI

Posterior hilum of the right kidney, right ureter

Lateral ascending colon, right colic flexure, right lobe of the liver

Medial head of the pancreas, bile duct, main pancreatic duct

o INFERIOR/ HORIZONTAL: THIRD PART 3 in (8 cm) long Runs transversely to the left, passing over the IVC, aorta, and

L3 vertebra Runs horizontally to the left on the subcostal plane Crossed by the superior mesenteric artery and vein and the

root of the mesentery of the jejunum and ileum Anterior surface is covered by peritoneum except where it is

crossed by the superior mesenteric vessels and the root of the mesentery

Table 9. Boundaries of inferior duodenum

Anterior root of the mesentery of SI, superior mesenteric vessels, jejunum

Posterior separated from the vertebral column by the right psoas major, IVC, aorta, and right testicular or ovarian vessels

Superior head of the pancreas and its uncinate process

Inferior jejunum

o ASCENDING: FOURTH PART curves anteriorly to join the jejunum at duodenojejunal

flexure supported by the suspensory muscle of duodenum (suspensory ligament of Treitz)

2 in. (5 cm) long Begins at the left of the L3 vertebra and rises superiorly as far

as the superior border of the L2 vertebra Runs upward and to the left to the duodenojejunal flexure Suspensory ligament of Treitz

-peritoneal fold which holds the duodenojejunal flexure in place, attaching to the right crus of the diaphragm -composed of a slip of skeletal muscle from the diaphragm and a fibromuscular band of smooth muscle from the third and fourth parts of the duodenum -contractions of the muscle widens the angle of the duodenojejunal fixture, facilitating movement of the intestinal contents -passes posteriorly through the pancreas and splenic vein and anterior to left renal vein

Table10 . Boundaries of ascending duodenum

Anterior beginning of the root of the mesentery, coils of jejunum

Posterior left margin of the aorta, medial border of the left psoas muscle.

B .JEJENUM and ILEUM

Figure 18. Jejenum and ileum

has no clear line of separation and together, is 6-7 m long

Runs from the duodenojejunal junction to the ileocecal junction

Its coils are freely mobile

Attached to the posterior abdominal wall by a fan-shaped fold of peritoneum known as mesentery of the small intestine

Mesentery a fan-shaped fold of peritoneum that attaches the jejunum and ileum to post. Abdominal wall

Root of the mesentery o (approx. 15 cm long) attached to posterior abdominal wall from

L2 to the right sacroiliac joint. It conveys nerves and blood vessels

o between the two layers of mesentery are superior mesenteric vessels, lymph nodes, variable amount of fat, autonomic nerves

Peyer's patches: aggregated lymphoid nodules that could be used to distinguish the ileum from the duodenum and jejunum.

JEJENUM o second part of small intestine and begins at duodenal flexure

where digestive tract resumes an interperitoneal course o 8 feet long Forms the upper 2/5 of the interperitoneal section

(jejunuileum) o double layer of peritoneum o mostly lies in left upper quadrant of infracolic compartment


ILEUM o third part of small intestine and ends at ileocecal junction

(union of the terminal ileum and cecum) o 12 feet long o Forms the lower 3/5 of the jejunuileum, o Ends at ileocecal junction o mostly lies at right lower quadrant

CLINICAL CORRELATON Meckel's diverticulum

Congenital anomaly.

Persistent vitellointestinal duct

Small bulge or malformation found in the terminal 2 ft. of the ileum

Usually asymptomatic, but can sometimes form an intestinal obstruction

May develop inflammation that can be confused with appendicitis (Meckel's Diverticulitis), mimicking its signs and symptoms

In distinguishing the jejunum from the ileum in radiographs, note that the JEJUNUM has a feathery

appearance while the ILEUM has a solid appearance.

Table 11. Summary of the differences between jejunum and ileum

II. LARGE INTESTINE

Extend from the ileocecal junction to the anus

Primary function: absorption of water and electrolytes; storage of undigested material until it can be expelled from the body as feces

Parts: cecum, ascending colon , transverse colon, descending colon, sigmoid colon, rectum and anal canal

Figure 19. Terminal ileum and large intestine

Can be distinguished from the small intestine by: o Omentum appendices: small, fatty, omentum-like projections o Teniae coli: 3 distinct longitudinal thickened bands of smooth

muscle Mesocolic tenia to which the transverse and sigmoid

mesocolon attach Omental tenia to which the omental appendices attach Free tenia to which neither mesocolons nor omental

appendices are attached. o Haustra: sacculations of the wall of the colon between teniae

These are formed due to teniae coli being shorter than the entire length of the large intestine

o A much greater calibre (internal diameter) Teniae, haustra, and fatty omentum appendices characteristic of

the colon are not associated with the rectum

A.CECUM

Blind intestinal pouch at the iliac fossa of the right lower quadrant abdomen (lies within 2.5 cm of the inguinal ligament)

Approx 7.5 cm in both length and breadth

Palpable through the anterolateral abdominal wall if distended with feces and gas

Devoid of mesentery and it is freely movable

completely covered with peritoneum Bound to the lateral wall by cecal folds of peritoneum o Ileal orifice - the opening at the junction of the ileum and

cecum. It has two lips, one above and one below called the ileocolic lips.

o Ileocecal valve two folds or lips that project around the orifice of ileum; rudimentary structure usually mistaken as the structure responsible for preventing the reflux of food back into the ileum, when it is actually the ileocecal sphincter that does the job.

o Frenulum a fold that runs from the ileocecal valve along o the wall at the junction of the cecum and ascending colon


Table12 . Boundaries of cecum

Anterior Small intestine, greater omentum, anterior abdominal wall in the right iliac region

Posterior Psoas and iliacus major, femoral n., lateral cutanoues nerve of the thigh

Medial Appendix

B. APPENDIX

Blind intestinal diverticulum (6-10cm) that contains masses of lymphoid tissue

Arises from the posteromedial aspect of the cecum inferior to the ileocecal junction

Attached to lower layer of the mesentery of SI by a short mesentery of its own called mesoappendix

Usually retrocecal but variations may occur In relation to the anterior abdominal wall, its base is situated 1/3

of the way up the line joining the RIGHT ASIS to the umbilicus (McBurneys point)

Anatomical position of the appendix will determine the site of muscular spasm and tenderness in appendicitis

C. ASCENDING COLON

Location: o lies in the right lower quadrant; o Extends upward from the cecum to the inferior surface right

lobe of the liver Turns to the left at the right colic flexure /hepatic flexure (lies

deep to the 9th and 10th rib) and becomes continuous with the transverse colon.

Retroperitoneal Greater omentum separates the ascending colon from the

anterolateral abdominal wall

Right paracolic gutter deep vertical groove lined with parietal peritoneum that lies between the lateral aspect of the ascending colon and the adjacent abdominal wall (see Figure 2.49 page 245 of Moore)

Narrower than cecum

Table13 . Boundaries of ascending colon

Anterior SI, greater omentum, anterior abdominal wall

Posterior Iliacus, iliac crest, quadrates lumborum, origin of tranversus abdominis muscle and right kidney. Iliohypogastric & ilioinguinal nerves cross behind it

C. TRANSVERSE COLON

Longest and most mobile part of the large intestine

Location: o crosses the abdomen from right colic flexure left colic

flexure o hanging to the level of the umbilicus (L3)

-in tall, thin people, it may extend in to the pelvis

left colic flexure/ splenic flexure o more superior, more acute and less mobile than the right colic

flexure o anterior to the inferior part of the left kidney

phrenicocolic ligament suspends the splenic flexure from the diaphragm

transverse mesocolon mesentery of the transverse colon, suspends the transverse colon from the pancreas

root of the transverse mesocolon along the inferior border of the pancreas and continuous with the parietal peritoneum posteriorly

Table14 . Boundaries of transverse colon

Anterior Greater omentum, anterior abdominal wall

Posterior 2nd

part of duodenum, head of pancreas, coils of duodenum and ileum

D. DESCENDING COLON

Location: o Lies in the left upper and lower quadrants o extends downward from the left colic flexure left iliac fossa

or pelvic brim

Retroperitoneal

Has a left paracolic gutter on its lateral aspect Covered anteriorly and laterally and attached to the posterior wall

by the peritoneum

Table15 . Boundaries of descending colon Anterior SI, greater omentum, anterior abdominal wall

Posterior Lateral border of left kidney, origin of tranversus abdominis ms, quadrates lumborum, iliac crest, iliacus and left psoas. Iliohypogastric, ilioinguinal, lateral cutaneous of the thigh and femoral nerve

E. SIGMOID COLON

S-shaped loop, links descending colon and rectum

Location: extends from iliac fossa S3, where it joins the rectum Rectosigmoid junction termination of teniae coli, approx 15cm

from anus

Sigmoid mesocolon long mesentery of sigmoid colon; attaches the sigmoid colon to the posterior pelvic wall

Root of the sigmoid mesocolon inverted V-shaped attachment, extending first medially and superiorly along the external iliac vessels and then medially and inferiorly from the bifurcation of the common iliac vessels to the anterior aspect of the sacrum.

Distinguising characteristics o Teniae coli disappears and then come together to form a broad

band of longitudinal fibers in the walls of the rectum o Omental appendices are long

Table 16. Boundaries of sigmoid colon Anterior Urinary bladder (males), poetrior surface of the uterus

and upper part of vagina (females)

Posterior Rectum, sacrum, lower coils of the terminal ileum

F.RECTUM

pelvic part of digestive tract, 5 in. (13cm) long follows the curvature of the cecum

extends from S3 up to the area where it pierces the levator ani muscle

peritoneum covers the anterior and lateral surfaces of the upper 1/3 of the rectum and only the anterior surface of the middle 1/3, leaving the lower 1/3 devoid of peritoneum because it is subperitonium

is S-shaped when viewed laterally

has NO mesentery, sacculations (haustra of the colon), taenia coli, appendices epiploicae

continuous proximally with the sigmoid colon, distally with the anal canal.

lying anterior to the S3 vertebra is the rectosigmoid junction, where (a.) teniae of the sigmoid colon spreads forming a continuous outer longitudinal layer of smooth muscle, and (b.) fatty omental appendices are discontinued


lies posteriorly against the inferior three sacral vertebrae and the coccyx, anococcygeal ligament, median sacral vessels, inferior ends of the sympathetic trunks and sacral plexuses

Rectal valves- support the weight of the feces and prevent over-distention of rectal ampulla (2 on the left namely the superior and inferior rectal valves and 1 on the right called the middle rectal valve)

Rectal ampulla distal dilated portion above the levator ani muscle; NOT covered by peritoneum (proximal third is covered anteriorly and laterally by pelvic peritoneum, the middle third is covered ONLY ON ITS ANTERIOR aspect by the peritoneum)

In Males: the peritoneum that covers the rectum goes down and covers the posterior aspect of the urinary bladder forming the floor of rectovesical pouch o rectum is related anterorly to the fundus of the urinary

bladder,terminal parts of the ureters, ductus deferentes, seminal glands and prostate

For Females: the peritoneum that covers the proximal 2/3 of the rectum covers the posterior fornix of the vagina to form the rectouterine pouch (Pouch of Douglas)

Pararectal fossae o (one in the right and one in the left) formed in the lateral

reflections of the peritoneum from the superior third of the rectum (in BOTH sexes); permit the rectum to distend as it fills with feces

o follows the curve of the sacrum and coccyx forming the sacral flexure of the rectum

o ends anteroinferior to the tip of the coccyx that perforates the pelvic diaphragm, immediately before the sharp posteroinferior angle of the anorectal flexure of the anal canal (an important mechanism for fecal continence)

o apparent anteriorly are the three sharp lateral flexures of the rectum (superior and inferior-on the left side, intermediate-if right)

o flexures are formed in relation to three internal infoldings (transverse rectal folds/valves of Houston): two on the left, one on the right;

Transverse rectal folds o overlie thickened parts of the circular muscle layer of the rectal

wall o support the weight of fecal matter to prevent its urging toward

the anus o superior to and supported by the pelvic diaphragm (levator ani)

and anococcygeal ligament o receives and holds fecal mass until it is expelled during

defecation o ability to relax to accommodate initial and subsequent arrival

of fecal material is important in maintaining fecal continence

G. ANAL CANAL

1.5 in. (4cm) long

extends from the superior aspect of levator ani muscleor pelvic diaphragm down to the anal orifice (anal verge) outlet of the alimentary canal

begins where the rectal ampulla abruptly narrows at the level of the U-shaped sling formed by the puborectalis muscle

lateral walls are kept in apposition by the levatores ani muscles and the anal sphincters except during defecation

Dendate line- lower border of anal column joined by anal valves;important landmark (derivative if ABOVE: HIND GUT, if BELOW: ECTODERM)

surrounded externally by internal and external anal sphincter (internal anal sphincter in the proximal 2/3 is made up of smooth muscles; thickened distal portion of the inner circular muscle layer of the anus)

Conjoined longitudinal muscle distal end of the outer longitudinal muscle layer that separates the internal from external anal sphincter

External anal sphincter is voluntary, supplied by inferior rectal nerve; internal anal sphincter is involuntary (visceral innervations)

Anal column-proximal third are ridges that contain the terminal branches of the superior rectal muscle

in the submucosa of the proximal third of anus, the internal venous plexuses are found

superior end of anal column corresponds to the anorectal line (where the lining epithelium from simple columnar epith. with goblet cells of the rectum changes to stratified squamous epith. In the anal canal)

lining epithelium DOES NOT change at the area of dendate line

Anal Valves- connect the inferior end of anal column Anal Crypts- spaces or depressions superior to anal valves into

which the secretion of perianal gland are emptied (important in BRONCHOTITIS and formation of FISTULA EDEMA)

White Line of Hilton- corresponds to the area where the conjoined longitudinal muscle attaches to the mucous membrane of the anal canal

Anal pecten the transitional zone between the skin and the mucous membrane; between the pectinate line and the anal verge

Surgical anal canal from anocutaneous line to the anal verge

Anatomical anal canal portion from dendate line (pectinate line/anatomic anorectal line) down to the anal verge

Table17 . Difference between small and large intestine

Small Intestine (SI) Large Intestine

EXTERNAL

Mobile (except duodenum) Ascending and descending are fixed

Located centrally Located in the periphery

Smaller calibre Larger caliber

Mesentery (except duodenum) Mesocolon (transverse, mesocolon, mesoappendix, mesosigmoid)

Continous layer of longitudinal muscles

Longitudinal muscle is collected into 3 bands, the teniae coli (except in the appendix, where the longitudinal ms are continous, teniae are absent in the rectum

Wall is smooth Haustra or sacculations bet the teniae are present

No fatty tags attached to its wall Appendices epiploicae/omentum appendices (fatty tags) are present

INTERNAL

Plicae circularis (valve of Kerckring)-permanent infoldings of the mucous membrane

Plicae circulars are absent, has semilunar folds called anal valve at the anal canal

Has villi in the mucosa No villi

Peyers patches (aggregations of lymphoid tissue) are present in the mucosa

No Peyers patches, appendix contains lymphoid tissue

III. BLOOD SUPPLY

first paired branch of the abdominal aorta is the right and left phrenic artery

1cm below the take off of the right and left inferior phrenic artery is the celiac trunk


A.CELIAC TRUNK

Artery of the foregut supplies GIT from lower of esophagus to middle 2nd part of duodenum

Arises from Abdominal aorta T12 Branches:

1. Left Gastric A. o Goes all the way up to provide branches to the abdominal

portion of the esophagus and occupies the upper lesser curvature of the stomach

o Anastomose with Right Gastric A. 2. Splenic A. o Going to the spleen via behind the stomach and upper

border of pancreas o Gives rise to Left Gastroepiploic A- supply the greater curvature; Short Gastric A - supply the fundus and greater curvature; some branches to pancreas including the dorsal

pancreatic artery 3. Common Hepatic A.

o Runs to the right along the upper border of pancreas o Gives rise to Right Gastric A., - supply the other part of lesser curvature

and pyrolus of stomach Proper Hepatic A., that enters the portal triad, and Gastroduodenal A.

B.SUPERIOR MESENTERIC ARTERY

Supplies the GIT from the 2nd part of duodenum to distal 1/3 of Transverse colon

Artery of the midgut that arise infront of Abdominal Aorta below Celiac Trunk

Branches: 1. Inferior pancreaticoduodenal A. o supply the pancreas and inferior half of duodenum

2. Middle Colic A o supply the proximal 2/3 of the transverse colon and divides

into right and left branches 3. Right Colic A. o often a branch of Ileocolic A. that supply the ascending colon

and further divide into ascending and descending 4. Ileocolic A. o The inferior branch is further divided into Anterior cecal a.

and posterior cecal artery that supply the Cecum o The appendicular a. supply the appendix is arises from the

posterior cecal artery. 5. Intestinal A. o Jejunal and Ileal branches: series of arcades in the small

intestines particularly jejunum and ileum

C. INFERIOR MESENTERIC ARTERY

Artery of the hindgut

distributes to the distal 1/3 of transverse colon to halfway down

of anal canal

Also a abdominal aorta branch that crosses the left common iliac artery.

Branches: 1. Left Colic A. o supply the distal 1/3 of transverse colon, left colic flexure,

and proximal half of descending colon 2. Sigmoid A o supply the distal of the descending colon and sigmoid

colon 3. Superior Rectal A o supplies the superior part of the rectum o Anastomose with middle and inferior rectal artery o Termination of inferior mesenteric artery

Note: MARGINAL ARTERIES of DRUMMOND anastomoses between superior and inferior mesenteric artery D. RECTAL ARTERY

Middle Rectal A o Supply the middle and inferior rectum o Arises from the inferior vesical (male) or uterine (female)

arteries, both are branches of internal iliac artery. Superior Rectal Artery o continuation of inferior mesenteric artery that supplies the

rectum and the upper half of anal canal

Inferior Rectal Artery o Supply the anorectal junction and anal canal o Arises from the internal pudendal artery ( a branch of internal

iliac A.)

IV. VENOUS DRAINAGE

Note: Veins follow the arterial blood vessels, even the names. They eventually drain into superior and inferior mesenteric veins, then to hepatic portal vein.

Through the portal vein (which is formed by the splenic and superior mesenteric veins, behind the neck of the pancreas at L2) liver sinusoids hepatic v. inferior vena cava

Superior mesenteric and inf. Mesenteric v.: follows the corresponding arteries

Sup. mesenteric and inf. mesenteric veins drain to the hepatic portal vein portal systemic anastomosis

Portal - systemic anastomoses o Esophageal branches of the left gastric vein (portal)

esophageal draining middle third of the esophagus into azygos v (systemic)

o Paraumbilical v (portal) superficial v. of anterior abdominal wall (systemic)

o Superior rectal v. (portal tributary) middle and inferior rectal v. (systemic)

o Retroperitoneal v. of ascending, descending colon, pancreas and liver (portal) renal, lumbar and phrenic v, (systemic)

above the pectinate line, all the lymph will find its way into your intestinal trunk which is one of the tributaries of thoracic duct


V. LYMPHATIC DRAINAGE

Follows the arterial vessel mesenteric nodesceliac

nodesmesenteric duct Lumbar nodes: drains lymph from rectum, descending colon

Superficial inguinal nodes and ext. iliac nodes: below the pectinate line, anal canal

Internal iliac nodes: upper canal (drains into inf. mesenteric nodes)

Lacteals - specialized lymphatic vessels in the intestinal villi that absorb fat that empty milk-like fluid to lymphatic plexuses in the walls of jejunum and ileum

o lacteals mesentery lymph passes through 3 groups of nodes: Juxta-intestinal (close to intestinal wall), Mesenteric lymph nodes (scattered among arterial arcades) and superior central nodes (located along proximal part of superior

mesenteric artery) superior mesenteric lymph node lymphatic vessels from terminal ileum follow ileal branch of

ileocolic artery to the ileocolic lymph nodes

VI. NERVE SUPPLY

Parasympathetic o From VAGUS nerve o From SACRAL PLEXUS, S2 to S4 o The vagus nerves supply preganglionic parasympathetic

innervation up to the splenic flexure and then the sacral parasympathetic nerves (S2-S4) take over

o Postganglionic neurons are located within the walls of the organs (Meissners and Auerbachs plexus) where postganglionic fibers are given off

Sympathetic o From pelvic splanchnic nerves o Sympathetic innervation is provided by the preganglionic

greater (T5-T9), lesser (T10-T11) and least (T12) splanchnic nerves pass through the diaphragm and synapse at the prevertebral ganglia (celiac, superior and inferior mesenteric) and postganglionic fibers follow the branching of the arteries.

o Additional preganglionic sympathetic fibers from the lumbar splanchnic (L1-L2-L3) synapse at the postganglionic neurons inferior mesenteric ganglion to supply postganglionic fibers to the lower digestive tract and the pelvic organs

Plexuses formed by the Parasympathetic and Sympathetic Nerve Fibers in Walls of Intestines are: o Auerbachs plexus Located between inner circular and outer longitudinal layers

of muscle Regulates peristalsis

o Meissners plexus Innermost, in the submucosa Regulates glands of mucosa and smooth muscles of

muscularis mucosae

Anatomy 4.2 GIT Gross_Elevazo

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