Digestive System

Dr: Azza ZakiDr: Azza Zaki


The Digestive SystemThe Digestive SystemThe digestive system is concerned with the: uptake digestion and absorption of food excretion of non-digested food.The digestive system divided into:A-A- Gastro-intestinal tractGastro-intestinal tractB-B- Digestive glands Digestive glands


Digestive tract (alimentary canal): is continuous tube with 2 openings, the mouth and the anus. it includes the following:Mouth pharynx oesophagus stomach small intestine & large intestine. Digestive glands include:Salivary glands liver & pancreas


•Most of the organs of the digestive system lie in the abdominal cavity, except: Mouth cavity, pharynx and salivary glands which lie in the head region. Oesophagus which traverses the neck and thorax.

The abdominal cavity:The abdominal cavity:

is bounded superiorly by the diaphragm which separates it from the thoracic cavity and continuous inferiorly with the pelvic cavity.


Abdominal RegionsAbdominal Regionsthe abdominal cavity is divided into 9 regions by: 2 vertical planes right & left. Each one extends from the mid-clavicular point to the mid-inguinal point. 2 horizontal planes 1. Upper horizontal plane: level of 3rd lumbar vertebra. 2. Lower horizontal plane: level of 5th lumbar vertebra.


The PeritoneumThe Peritoneum• The abdominal cavity is

lined by the Peritoneum which is the largest serous membrane in the body, and it consists of a double layer: A. Outer layer: is called the parietal peritoneum, lines the abdominal cavity.

B. Inner layer: is called the visceral peritoneum, covers the abdominal viscera.

The space between the 2 layers is a potential space and contains small amount of fluid (peritoneal cavity)


Mouth CavityMouth Cavity

• The mouth cavity is the first portion of the digestive tube.

• It extends from the lips anteriorly and opens posteriorly in the oropharynx.

• It is divided into:VestibuleMouth cavity

proper


Vestibule• is the narrow space between

the teeth and gums internally and lips and cheeks externally.

• It communicates posteriorly with the mouth cavity proper by the interval behind the last molar tooth. It receives the opening of the parotid duct opposite to the upper 2nd molar tooth.


Mouth Cavity Proper

It is bounded:•Laterally and in front: by the teeth and gums. •Above: by the hard and soft palates. •Below: by the mucous membrane, which covers the floor of mouth.

–It communicates:•Anteriorly with outside through the oral fissure.•Posteriorly with the oropharynx through the isthmus of fauces.


Palate • It separates mouth cavity from

nasal cavity & consists of:• The hard palate• The soft palate has a

downward median projection, called "uvula". During swallowing, the uvula ascends upwards to close posterior nasal apertures.

• The mouth cavity contains:

– Tongue– Teeth


The TongueThe TongueIt is a highly mobile muscular organ which is formed of striated muscle fibers and covered by mucous membrane. The mucous membrane on the dorsum of the tongue is rough, and it is covered with small projections called lingual papillae. Some of the papillae contain taste buds.


Superior Surface of the TongueTongue papillae

Filiform papillae Fungiform papillaeCircumvallate papillae

Sulcus terminalis:“V”-shaped sulcus: separates anterior 2/3 from posterior 1/3 of the tongue. Posterior 1/3 of tongue lies in oropharynx•Lymphatic follicles lie posterior to this sulus and called "lingual tonsils".


• Its under surface is covered by smooth mucosa which is connected to mouth floor by frenulum.

• Function of the tongueFunction of the tongue:

• The tongue helps in deglutition, taste and speech.


Nerve Supply Of The TongueNerve Supply Of The Tongue


Nerve Supply Of The TongueNerve Supply Of The Tongue•The tongue has motor and sensory nerve supply:

MotorMotor for most of the muscles from the hypoglossal nerve. hypoglossal nerve. Sensory: anterior ⅔ ;anterior ⅔ ; by trigeminal trigeminal nerve for general sensationgeneral sensation and facial nervefacial nerve for taste.taste.posterior ⅓;posterior ⅓; by glossopharyngealglossopharyngeal nerve for both general sensation and taste.


TeethTeeth • Deciduous (milky teeth): they are 20 teeth (4

incisors& 2 canines & 4 molars). The 1st tooth to erupt is the central incisor (6th month).

• Permanent teeth: they are 32 teeth (4 incisors & 2 canines & 4 premolars & 6 molars). The 1st to erupt is the 1st molar. The last to erupt is the 3rd molar (wisdom tooth).


The Pharynx• It is a common

pathway for digestive and respiratory systems.

• It is musculo-membranous tube that lies behind the nose, mouth and larynx.

• It is about 12 cm in length and extends from the base of skull down to the 6th cervical vertebra, where it continues as oesophagus.


• It consists of three parts:– Nasopharynx: lies behind the nasal cavity and

communicating freely with it through posterior nasal apertures. It communicates inferiorly with the oropharynx through the pharyngeal isthmus. It contains pharyngeal tonsil & auditory tube.

– Oropharynx: lies behind the oral cavity extending from the level of soft palate to the upper end of the epiglottis. It communicates with the mouth cavity through the oropharyngeal isthmus. It contains palatine tonsil.

– Laryngopharynx: lies behind the larynx communicating with it through the laryngeal inlet. It is continuous inferiorly with the oesophagus


The OesophagusThe OesophagusIt is a muscular tube about

25 cm long. It beginsbegins as the continuation

of the pharynx (level of pharynx (level of C6).C6).

It passes in the neck, then in the thorax through the mediastinum & then through the diaphragm to endend in the stomach.stomach.


Most of its course is in the middle line but deviates to the leftthe left at the level of T7 vertebra where it passes in front of descending aorta till it passes through opening of the opening of the diaphragmdiaphragm at level of T10.T10.

Through its course, it is related:PosteriorlyPosteriorly to the

cervical and thoracic vertebrae, while

Anteriorly Anteriorly it descends behind the tracheatrachea and heart heart respectively


The oesophagus

It has the following constrictions:

LevelDistance from

the incisor teeth

where it is crossed by the

aortic arch

where it is crossed by the left

bronchus

where it pierces the diaphragm

9 inches

11 inches

16 inches


The StomachThe Stomach


The StomachThe Stomach• It lies in the upper

part of the abdominal cavity, in the epigastrium and left hypochondrium.

• It is commonly J-shaped that has:– 2 orifices– 2 curvatures– 2 surfaces– 2 portions


2 curvatures

Cardiac orifice Pyloric orificeIt lies at junction with oesophagus. It lies at the junction with

duodenum.

It lies 1 inch to left of the midline. It lies ½ inch to left of the midline.

It is guarded by physiological sphincter.

It is guarded by anatomical sphincter (thick circular fibers).

Lesser curvature Greater curvature

It is the concave right border. It is the convex left border.

It gives attachment to lesser omentum.

It gives attachment to greater omentum.

It shows a depression called angular notch.

It is 4 times longer than the lesser curvature.

2 orifices


–2 surfaces:•Anterior surface: it is related mainly to the left lobe of liver.•Posterior surface: related to a group of structures called "stomach bed"stomach bed" which include: upper part of left kidney, left supra-renal gland, spleen, body of pancreas.


2 Portions2 Portions•Cardiac portion:Cardiac portion:

–Fundus: is the part that lies above and to the left of the cardiac orifice.–Body: is the part between the

fundus and an imaginary line between the angular notch and opposite point on the greater curvature.

•Pyloric portion:Pyloric portion:–Pyloric antrum: is the dilatation

following the body. –Pyloric canal: is the cylindrical

part following the antrum.–Pylorus: is the opening that is

surrounded by a muscular ring called pyloric sphincter.


Peritoneum of the stomach

• It is completely covered by peritoneum except the area on the back of the fundus.

• The lesser omentum: extends from lesser curvature to the liver.

• The greater omentum is attached to greater curvature then attached to the transverse colon &pancreas


Arterial Supply

Left gastric artery

Right gastric artery

Right gastroepiploic

Left gastroepiploic

Hepatic artery

Gastroduodendal

Splenic artery

Celiac arteryCeliac artery

Short gastric

arteries


The Small IntestineThe Small Intestine• It is 6 meters6 meters

long and takes the shape of coiled loops that fill most of the abdominal cavity.

• It consists of 3It consists of 3 divisions:

• Duodenum• Jejunum• Ileum


DuodenumDuodenumIt is the shortest and widestshortest and widest part of the small intestine (about 25 cm in length). It is “C” shaped“C” shaped and is formed of 4 parts.It is firmly attached to the posterior abdominal wall and not mobile. The head of pancreashead of pancreas lies in the “C” shaped concavity.The bile ductbile duct and main pancreatic duct unit together and open in the middle of the 2nd part.2nd part.

cancer head of pancreas leads to: obstructive jaundice intestinal obstruction


Jejunum and IleumJejunum and Ileumform the free part of the small intestine and are freely freely mobilemobile. They are attached to the posterior abdominal wall by means of mesentery.mesentery. Jejunum extends from the duodenum.The ileum ends by opening into the cecum (ileocecal valve)

JejunumJejunum IleumIleum

Extent Proximal2/5 Distal 3/5

Diameter Larger Smaller

Lymphatic follicles

Are few & small Are numerous & large (Payer’s patches

Mucosa More circular folds & larger villi

Less circular folds & smaller villi

Dr: Azza ZakiDr: Azza Zaki JejunumJejunumIleumIleum


Large Intestine (Colon)Large Intestine (Colon)It is about 1.5 meters1.5 meters in length. It extends from the end of the ileum to the anus.anus. It is larger larger in diameter than the small intestine.


The large intestine has the following features:The large intestine has the following features:

• Appendices epiploicae:Appendices epiploicae: are small peritoneal sacs filled with fatwith fat scattered on the wall of large intestine (except on cecum & appendix & rectum).

• Taenia coli:Taenia coli: the outer longitudinal musclelongitudinal muscle coat of large intestine is arranged in 3 longitudinal bands that begin at the base of appendix (they are absent in the appendix & rectum).

• Sacculations:Sacculations: the length of taenia coli is shorter than the true length of large intestine puckering of the wall.


Large Large intestineintestine

Small Small intestineintestine


Difference between small & large intestinesDifference between small & large intestines

Small intestine Large intestineLength About 6 meters About 1 ½ meter

Diameter Smaller Larger

Appendices epiploicae

Absent Present

Taenia coli Absent Present

Sacculation Absent Present

Mucosa • Permanent circular folds •Villi are present•Aggregated lymph follicles

• Circular folds disappear by distension•Villi are absent •Solitary lymph node


•The large intestine is divided into the following parts:–CecumCecum is a blind pouch which hangs down at the junction of the ileum and the colon. The Ileocecal valve lies at its medial aspect and prevents the return of the faeces from the cecum into the small intestine. The appendix arises from the cecum about 2.5 cm below the ileocecal valve. –Ascending ColonAscending Colon extends from the cecum to the under surface of the liver where it turns to the left. This bend is called right colic (hepatic) flexure.


Transverse ColonTransverse Colon crosses the upper part of abdominal cavity from right to left and then curves sharply downwards under the lower end of the spleen forming the left colic (splenic) flexure. Descending ColonDescending Colon extends from the splenic flexure to the brim of the pelvis, where it turns towards the midline to become the sigmoid colon.Sigmoid ColonSigmoid Colon extends from the descending colon at the level of pelvic brim to the rectum. It is “S” shaped.RectumRectum extends from the sigmoid colon to the anal canal. It descends along the sacrum to the tip of coccyx. Its lower part shows dilatation called "ampulla of rectum".Anal CanalAnal Canal is the terminal portion of the large intestine. It extends from the rectum to the anus and is about 4 cm in length. In the anal canal the circular muscle fibres are thickened to form internal anal sphincter. The external anal sphincter is composed of skeletal muscle, therefore under voluntary control.


Digestive GlandsDigestive Glands

•Salivary GlandsSalivary Glands

•LiverLiver

•PancreasPancreas


Salivary GlandsSalivary Glands

• There are three There are three pairs of salivary pairs of salivary glands:glands:

1.1. Parotid Parotid

2.2. SubmandibularSubmandibular

3.3. SulingualSulingual


The Parotid GlandThe Parotid Gland

Is the Is the largestlargest salivary salivary gland, which lies gland, which lies belowbelow & & in front of the ear,in front of the ear, between the mastoid process & ramus of the mandible.

It is wedge- shaped with its base directed upwards & base directed upwards & apex directed downwards.apex directed downwards.

The The parotid ductparotid duct passes passes through the buccinator muscle & opens into the through the buccinator muscle & opens into the vestibulevestibule of the mouth opposite the of the mouth opposite the upper second molarupper second molar tooth. tooth.

Its secretion is watery.Its secretion is watery.


The Submandibular GlandThe Submandibular GlandLies in contact with the Lies in contact with the

mandible.mandible. Its Its duct opensduct opens into the into the

floorfloor of the mouth. of the mouth. Its secretion is watery & Its secretion is watery &

mucousmucous• The Sublingual gland:The Sublingual gland: It is the It is the smallestsmallest

salivary gland.salivary gland. It lies under the mucous It lies under the mucous

membrane of the floor of the membrane of the floor of the mouth (mouth (under the tongueunder the tongue) it has ) it has several minute ducts, which several minute ducts, which open into the open into the floorfloor of the mouth. of the mouth.

Its secretion is mucous.Its secretion is mucous.


Liver Liver • It is the largestlargest

organ of the body.• Location:Location:• In the right right

hypochondriumhypochondrium & epigastrium.

• Surfaces:Surfaces:• It is a wedged shaped

which has: smooth convex anterior, superior, posterior & right lateral surfaces. They collectively related to the diaphragm.

The diaphragm separates the liver from the right pleura &lung, pericardium, left pleura & lung.


•Inferior surface:Inferior surface: which is concave& shows impressions of these organs:

1.Gastric impression for the stomachstomach

2.Renal impression for the rightright kidneykidney

3.Fossa of gall bladdergall bladder

4.Colic impression for the right colic flexure

5.Groove for the inferior vena cava.

6.Duodenal impression

7. Quadrate lobe.

8. Caudate lobe

9.Porta hepatis.


Porta HepatisPorta Hepatis• It is the hilum of

the liver• It lies between the

caudate & quadrate lobes.

• It gives passage gives passage to the following to the following structures:structures:

1.1.Hepatic ductsHepatic ducts: anterior in position

2.2.Hepatic artery:Hepatic artery: intermediate in position.

3.3.Portal vein:Portal vein: posterior in position


The liver has: Two main lobes, right right

and leftand left, separated by the falciformfalciform ligament.

Two small lobes: quadrate & caudatequadrate & caudate lobes. Anatomically these 2 lobes belong to the right lobe. While physiologically, they are part of the left lobe as they are supplied by left branch of the hepatic artery.

Liver covered by peritoneum except bare area posteriorly.


Blood Supply Of The LiverBlood Supply Of The Liver• The liver has

double blood supply:

1.1. Hepatic arteryHepatic artery provides 30%

2.2. Portal veinPortal vein provides 70%

The liver is drained bydrained by 2 hepatic veinshepatic veins which end in the inferior vena inferior vena cava.cava.


Biliary SystemBiliary System1-Gall bladder:1-Gall bladder:• It is a pear- shaped sac.• It has fundus, body fundus, body

and neck.and neck.• Its neckneck is continuous

with the cystic duct.cystic duct.• It is located in gall

bladder fossa on the inferior surface of the liver.


2-Right & left hepatic ducts:2-Right & left hepatic ducts:• They are coming from the

right & left lobes of the liver & unite to form common hepatic duct.

3-Common hepatic duct:3-Common hepatic duct:• It is joined joined by the cystic cystic

duct to form common bile common bile duct.duct.

4-Common bile duct:4-Common bile duct:• It descends behind the

head of pancreas, where it joins the main pancreatic joins the main pancreatic ductduct to open into the 2the 2ndnd part of the duodenumpart of the duodenum

• This opening is guarded by a valve (sphincter of oddi).


PancreasPancreas It is elongated gland that

lies across the posterior abdominal wall at the level of 2nd lumbar vertebra.

has both endocrine & both endocrine & exocrineexocrine functions:

The exocrine portion: secretes pancreatic juice.

Endocrine portion: islets of langerhans( beta cells secrete insulin & alpha cells secrete glucagon)

It is not mobile as it is retro-peritoneal retro-peritoneal structure.


Parts Of The PancreasParts Of The Pancreas Head:Head: It is the broad right end

which is enclosed within the C shaped within the C shaped curve of the curve of the duodenum.duodenum.

It sends a downward process called uncinate process.

Neck:Neck: It is the junction

between the head and body. It is related to the portal vein (union of portal vein (union of superior mesentric superior mesentric with splenic veins)with splenic veins).


• Body: Body: Is triangular in cross section with:• Anterior surface: lies behind the lesser sac• Posterior surface: is related to posterior abdominal wall.• Inferior surface: is related to small intestine.• Tail:Tail: the left narrow end which reach to the spleen.spleen.


Ducts Of The PancreasDucts Of The Pancreas 1)1) Main pancreatic duct:Main pancreatic duct:

extends through the whole length of the pancreas to unite with the common bile common bile ductduct forming the hepato-pancreatic ampulla which opens in the 22ndnd part duodenum. part duodenum.

2)2) Accessory pancreatic Accessory pancreatic duct:duct: starts in the uncinateuncinate process & ascends in front of the main duct & opens in the 2nd part duodenum.


Blood Supply Of The Gastroinestinal TractBlood Supply Of The Gastroinestinal Tract• Arterial supply:Arterial supply:• By 3 single arteries

which arise from the front of the abdominal aorta:

1.1. Coeliac trunk:Coeliac trunk: supplies the foregut:foregut:

lower part of oesophagus,

stomach, upper half of the 2nd

part duodenum, liver, pancreas & spleen)


2- Superior Superior mesentric mesentric artery:artery: supplies the midgut:midgut:

Lower half of the 2nd part duodenum

JejunumIleumCaecumAscending colonRight 2/3 of the

transverse colon.


3- Inferior Inferior mesentric mesentric artery:artery:

supplies the hindgut:hindgut:

Left 1/3 of transverse colon

Descending colon

Pelvic colonRectumUpper half of the

anal canal


Venous Drainage of GITVenous Drainage of GIT


Venous Drainage of GITVenous Drainage of GIT By tributaries corresponding

to the branches of arteries, which ultimately drained into the portal vein.portal vein.

Where and how the portal portal vein is formed?vein is formed?

The portal vein is formed behind the neck of behind the neck of pancreaspancreas by the union of superior mesentericsuperior mesenteric vein & the splenic veinsplenic vein. The portal vein goes to the liver.

From the liver, the 2 hepatic hepatic veins drain into the inferior inferior vena cava.vena cava.


References

• Clinical anatomy by systems. Snell 2007• Clinically oriented anatomy 5th ed Moore• Gray’s anatomy for students. Drake• Color atlas the human body. Faller 2004• Netter atlas

Digestive System

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