The Abdomen

Surface Anatomy, Vessels, Muscles, and Peritoneum

Abdominopelvic Cavity

• Ventral body cavity– Thoracic– Abdominopelvic

• Abdominopelvic– Abdominal

• Liver• Stomach• Kidneys

– Pelvic cavity• Bladder• Some reproductive

organs• Rectum

Abdominopelvic Cavity

• Surrounded by the abdominal walls and pelvic girdle

• The two cavities are continuous

• Most organs surrounded by a peritoneal cavity– Visceral peritoneum– Serous peritoneum– Peritoneal cavity

pg 242

Abdominal Quadrants

• 9 regions • 4 quadrants

– Draw “line” through navel

– Right upper quadrant

– Left upper quadrant

– Left lower quadrant– Right lower

quadrant

pg 242

Surface Anatomy• Anterior abdominal wall

extends from costal margin to inferior boundaries:– Iliac crest– Anterior superior iliac

spine– Inguinal ligament– Pubic crest

• Superior boundary– Diaphragm

• Central landmark– Umbilicus

• Linea alba (white line)– Tendinous line– Extends from xiphoid

process to pubic symphysis

pg 345

Muscles• Function:

– Help contain abdominal organs

– Move trunk– Forced breathing– Increase intra-abdominal

pressure• Abdominal wall

– Anterior (4)• Innervated by intercostal

nerves• Continuous with layers of

intercostal muscles• Fibers of layers run in

different directions for strength

• Ends in aponeurosis which contains rectus abdominis muscle

– Posterior (3)

pg 250

Anterior Abdominal Wall Muscles

Rectus Abdominis – Origin

• Pubic crest, symphysis– Insertion

• Xiphoid process, costal cartilages of ribs 5-7

– Function • Flex, rotate trunk, fix and depress

ribs, stabilize pelvis, compress abdomen

• Internal oblique – Origin

• Lumbar fascia, iliac crest, inguinal ligament

– Insertion • Linea alba, pubic crest, last 3-4

ribs, costal margin– Function

• Same for external obliques

pg 250, 251

Anterior Abdominal Wall

• External oblique– Origin

• Lower 8 ribs– Insertion

• Aponeurosis to linea alba, pubic and iliac crest

– Function • Flex trunk, compress abdominal

wall (together), Rotate trunk (separate sides)

• Transversus abdominis– Origin

• Inguinal ligament, lumbar fascia, cartilage of last 6 ribs, iliac crest

– Insertion• Linea alba, pubic crest

– Function• Compress abdominal contents

pg 249

Posterior Abdominal Wall• Iliopsoas

– Psoas major• Origin

– Lumbar vertebrae, T12

• Insertion– Lesser trochanter of femur via iliopsoas

tendon• Function

– Thigh flexion, trunk flexion, lateral flexion• Innervation

– Ventral rami L1-L3

– Iliacus• Origin

– Iliac fossa, ala of sacrum• Insertion

– Lesser trochanter of femur via iliopsoas tendon

• Function– Thigh flexion, trunk flexion

• Innervation– Femoral nerve (L2 and L3)

– Psoas minor – variable (40-60% do not have)

pg 316

Posterior Abdominal Wall

• Quadratus lumborum– Origin

• Iliac crest and lumbar fascia

– Insertion• Transverse process of

upper lumbar vertebrae, lower margin of rib 12

– Function• Flex vertebral column,

maintains upright posture, assists in inspiration

– Innervation:• T12 and upper lumbar

spinal nerves (ventral rami)

pg 316

Peritoneum

• Mesenteries – Double layer of peritoneum (2 serous membranes

fused together)– Extend to the digestive organs from the body wall– Function:

• Hold organs in place• Sites of fat storage• Provide a route for vessels and nerves

– Dorsal mesenteries:• Lesser omentum and Falciform ligament

– Ventral mesenteries:• Greater omentum, Transverse mesocolon, Mesentary,

and Sigmoid mesocolon

Dorsal Mesenteries

pg 269 pg 291

Ventral Mesenteries

pg 269

pg 271

Peritoneum• Peritoneal

– Remains surrounded by peritoneal cavity– Liver, stomach, ileum and jejunum

• Retroperitoneal– Some organs lay behind/outside peritoneum

• Primarily retroperitoneal– Organs NEVER within the cavity– Kidneys, bladder, ureter

• Secondarily retroperitoneal– Organs once suspended within the abdominal cavity by

mesentery– Migrate posterior to the peritoneum during the course of

embryogenesis to become retroperitoneal – Lack mesenteries – Duodenum, ascending and descending colon, rectum,

pancreas

pg 226

Organs of the Abdomen

Urinary and Digestive Systems

Urinary System

Urinary System

• Kidney (2)– Purify blood

• Ureter (2)– Drains urine from

kidney to bladder

• Urinary Bladder– Stores urine

• Urethra– Drains urine from

bladder to outside body

pg 314

Kidneys

• Filter waste from blood– Water, toxins, urea, uric acid,

creatinine, metabolic waste, ions

• Excretion of waste• Homeostasis

– Acid-base balance– Blood pressure– Plasma volume

Kidneys: Gross Anatomy

• Lie in retroperitoneal, superior lumbar region

• Extend from T11 or T12 to L3

• Laterally convex, medially concave

• Hilus– Where blood vessels,

ureters, and nerves enter and leave kidney

• Adrenal gland– On superior portion

pg 325

Kidney: Gross Anatomy

• Separated into lobes• Blood supply

– Renal artery and vein

– ¼ heart’s systematic output reaches the kidney

• Innervation– Branches of renal

plexuspg 323

Kidney: Gross Anatomy

• Supportive tissue– Renal capsule

• DCT• Adheres directly to

kidney surface• Maintains shape and

forms barrier– Adipose capsule

• Perirenal fat• Cushions kidney• Keeps kidney in place

– Renal fascia – Pararenal fat

• Cushions kidney • Keeps kidney in place

Internal

External

pg 322

Kidney: Internal Gross Anatomy

• Cortex– Superficial – Lighter zone– Functional portion

• Medulla– Deep– Darker zone– Pyramid shaped– Contains collecting

tubules

pg 323

Kidney: Internal Gross Anatomy

• Medullary pyramid– Makes up the medulla– Base: against cortex– Apex: inward

• Papilla = tip• Drips urine into minor calyx

• Calices– Collect urine draining from

papillae and empty into renal pelvis

– Major calices • Branching extensions of

renal pelvis– Minor calices

• Divisions of major calices• Surround papilla of pyramids• Collect urine from papilla

• Renal pelvis– Expanded superior part of

ureter

pg 323

Kidney: Internal Vasculature

• Renal arteries• Segmental arteries

– Enter through the hilus

– Branch into:• Lobar arteries• Interlobar arteries• Arcuate arteries

– At border of cortex and medulla

• Interlobular arteries

pg 323

Kidney: Microscopic Anatomy

• Uriniferous tubules– Produces urine through filtration,

reabsorption, and secretion– 2 major part:

• Nephron• Collecting duct

Ureters• Carry urine from the

kidneys to the bladder• Begins superiorly at L2 as

a continuation of renal pelvis

• Opens into the bladder• Retroperitoneal• Enters the bladder at an

oblique angle– This prevents backflow into

the ureters• Increased pressure in

bladder lead to the distal end of ureter closing– Not only gravity at work

here!!pg 325

Ureters: Microscopic Anatomy

• Another tubular organ!!• Mucosa

– Lamina epithelialis• Transitional epithelium• Stretches when ureters

are full– Lamina propria

• Muscularis– Inner longitudinal– Outer circular– External longitudinal layer

(inferior third)– Function in peristalsis

• Adventitia – CT

Urinary Bladder• Stores and expels urine• Posterolateral angle

receives the ureter• Inferior angle drains into

the urethra• Located:

– Inferior to peritoneal cavity

– On pelvic floor– Posterior to pubic

symphysis– Male:

• Anterior to rectum– Female:

• Anterior to vagina and uterus

pg 400

Urinary Bladder

• Full bladder expands into abdominal cavity

• Empty bladder lies within pelvic cavity

• Vasculature:– Internal iliac branches

of arteries and veins

• Innervation:– Branches of the

hypogastric plexus

pg 399

Urinary Bladder: Internal Anatomy

• Tubular organ!!!!! • Trigone area• 3 layers:

– Mucosa• Transitional epithelium• Lamina propria

– Muscular layer• Detrusor muscle (smooth);

3 layers:– Inner and outer

longitudinal, middle circular

– Adventitia• Fibrous CT• Parietal peritoneum on

superior surfacepg 400

Urethra

• Drains urine from bladder to outside of body

• Female:– Short tube

• Male– 3 regions

• Prostatic urethra• Membranous urethra• Spongy/penile urethra

– Opens at the external urethral orifice

– Also carries ejaculating semen

pg 400

Urethra Landmarks

• Internal urethral sphincter– At bladder/urethral junction– Thickening of detrusor muscle– Involuntary; keeps urethra closed when urine is not being

passed– Prevents dribbling!

• External urethral sphincter– Surrounds urethra within the urogenital diaphragm– Inhibits voluntary urination until ready

• External urethral orifice– Males:

• End of the penile urethra– Females:

• Anterior to vaginal opening and posterior to clitoris

Males versus Females:

pg 403

Micturition = Urination

• Contraction of the detrusor muscle to raise intra-abdominal pressure

• Controlled by the brain• Urine accumulation leads to distention of the

bladder– Activates stretch receptors – Send sensory impulses to micturition center (MC) in

the pons

• MC sends signals to parasympathetic neurons– Stimulate detrusor muscle to contract (involuntary)– Internal urinary sphincter opens (also inhibits

sympathetic pathways that would prevent urination)

Micturition = Urination

• Other brain receptors (pons, cerebral cortex) can inhibit urination – Relaxing of the detrusor, keeping

external urinary sphincter closed

• Voluntary contraction of abdominal wall muscles increases abdominal pressure

• Voluntary relaxation of external urethral sphincter

Digestive System

Digestive System

• Alimentary Canal– Mouth– Pharynx– Esophagus– Stomach– Small Intestine– Large Intestine

• Accessory Organs– Teeth, Tongue– Salivary Glands– Gallbladder– Liver– Pancreas

pg 222

Digestive Processes – 6 Steps

• Ingestion– Taking food into the mouth

• Propulsion– Movement of food through GI tract

• Swallowing and peristalsis

• Mechanical digestion– Prepares food for chemical digestion– Chewing, churning, segmentation

• Chemical digestion– Enzymes break down complex food

molecules• Absorption

– Digested end products from lumen to blood

• Defecation– Elimination of indigestible substances

Alimentary Canal Wall

• ANOTHER tubular organ!• Layers:

– Mucosa• Epithelium• Lamina propria (MALT)• Lamina muscularis mucosa

– Submucosa• CT with elastic fibers,

nerves, vessels

– Muscularis• Inner circular• Outer longitudinal• Creates sphincters

– Serosa / Adventitia

pg 313

Peristalsis vs Segmentation

• Peristalsis – Propulsion– Adjacent segments of the alimentary

canal contract and relax– Moves food distally along the canal

• Segmentation– Part of mechanical breakdown– Food-mixing process– Nonadjacent segments of the

intestine alternatively contract and relax

– Moves food on and back– Mixes rather than propels

Innervation

• Nerve plexuses– Occur within wall of alimentary canal– Parasympathetic, Sympathetic, Visceral

Sensory fibers– 2 types:

• Myenteric nerve plexus– Between 2 muscle layers of the tunica muscularis– Controls segmentation and peristalsis

• Submucosal nerve plexus– Between submucosa and muscularis mucosa– Signals glands to secrete and LMM to contract

pg 313

Innervtion

• Enteric Nervous System (ENS)– Internal neurons in wall of canal (100

million!!)– Within the above plexuses– Form independent arcs of sensory, intrinsic,

and motor neurons– Controls glandular secretion, peristalsis,

segmentation– Autonomic Nervous System speeds up or

slows activity controlled by enteric system• Allows the CNS to influence it

Stomach• J-shaped• Temporary storage tank• Regions:

– Cardiac• Cardiac orifice• Junction of esophagus

– Fundus• Under diaphragm

– Body• Large midportion

– Pyloric• Ends at the stomach• Pyloric sphincter

– Greater curvature– Lesser curvature pg 272

Stomach – Internal Anatomy

• Mucosa– Epithelium

• Simple columnar– Rugae

• Folds that allow for volume changes

– Intrinsic glands• Goblet cells• Gastric glands

– Submucosa • Muscularis

– Oblique layer– Circular layer

• Pyloric sphincter– Longitudinal layer

• Serosa

Stomach Function

• Storage of chyme– Food paste

• Breakdown of food proteins– Done by pepsin

• Protein-digestion under acidic conditions

• Absorption of nutrients– H2O, electrolytes– Alcohol, other drugs

• Food remains for about 4 hours• Holds from 1.5 to 4 liters

Small Intestine

• Longest portion of GI tract• Site of most enzymatic digestion and

absorption of nutrients– Bile: emulsifier (gallbladder, liver)– Enzymes (pancreas)

• Undergoes segmentation– Allows for an increase contact with intestinal

walls

• Peristalsis propels chyme through in about 3 to 6 hours

• 2.6 to 6 meters long!!

Small Intestine

• Location:– From pyloric

sphincter to first part of the large intestine

• Regions:– Duodenum (5%)

• Proximal

– Jejunum (almost 40%)

• Middle

– Ileum (almost 60%)• Distal

pg 274

Small Intestine • Duodenum

– C – shaped – Short, straight– Mostly retroperitoneal– Receives:

• Digestive enzymes from pancreas via main pancreatic duct

• Bile from liver via the bile duct

• Ileum and jejunum– Highly coiled– Fewer modifications– Hang by mesentery in

peritoneal cavity– Mesentery Arcades

• Arteries + veins• Nerves• Store fat

pg 283

Small Intestine Internal Anatomy

• Intestinal flora– produces vitamin K

• Epithelium:– Simple columnar

epithelium with many modifications for absorption

• Lymph tissue in submucosa• Muscularis externa has 2

layers• Innervation:

– Some parasympathetic innervation from vagus

• Arterial supply: – Superior mesenteric – Rt (cranial)

pancreaticoduodenalpg 283

SI Absorption Modifications• Length

– More length, more area for absorption!

• Circular folds– Plicae circulares– Transverse ridges of mucosa– Increase surface area– Force chyme to slow down

• Villi– Move chyme and increase contact– Contain lacteals

• Remove fat

• Microvilli – More increasing of the surfcae

area

Modifications decrease distally

Large Intestine

• Regions:– Cecum– Vermiform appendix– Colon

• Ascending• Transverse• Descending• Sigmoid

– Rectum– Anal Canal

pg 279

Large Intestine

• Functions:– Absorbs remaining

nutrients• Most material largely

digested

– Absorbs water and electrolytes

– Forms, stores and expels feces from body

• Propulsion is slow and weak through LI except for mass peristaltic movements

pg 283

LI: Internal Features

• Intestinal flora • No intestinal villi or modifications for

absorption• Many goblet cells• Simple columnar epithelium except lower

half of anal canal• Significant lymph tissue in mucosa and

submucosa• Muscularis mucosae has 2 layers• Some parasympathetic innervation from

vagus

LI Special Features

• Teniae coli– 3 Longitudinal strips– Thickenings of

longitudinal muscle layer

– Maintain muscle tone– Cause LI to pucker into

sacs…….

• Haustra– Saclike divisions

• Epiploic appendages– Fat-filled pouches of

visceral peritoneum– Hang from the intestine

pg 279

Cecum and Vermiform Appendix

• Cecum– Sac-like pouch (blind pouch)– Ileocecal valve

• 2 raised edges of the mucosa• Sphincter keeps closed until

food in stomach• Prevents reflux of feces from

cecum to ileum

• Vermiform Appendix– Blind tube– Opens into cecum– Contains large masses of

lymphoid tissue

pg 276

Colon Segments• Ascending

– Right side of posterior abdominal wall

– Makes right angle turn• Right colic / hepatic

flexure

• Transverse– Extends left across the

peritoneal cavity– Bends downward at the

spleen• Left colic / splenic flexure

• Descending– Left side

• Sigmoid– S-shaped– “True pelvis”

pg 279

Colon Functions

• Absorb H2O and electrolytes

• Some digestion by bacteria• Mass Peristaltic Movements (2-3x

day)• Moves through in 12-24 hours• 1.5 meters

Rectum

• Joins with the sigmoid colon

• Descends into the pelvis

• Complete and well-developed longitudinal muscle layer

• Rectal valves– 3 transverse folds– Prevent feces from being

passed along with gas

pg 283

Anal Canal

• Begins where rectum passes through the levator ani muscle

• Releases mucus to lubricate feces

• Internal anal sphincter– Made of smooth muscle– Involuntary

• External anal sphincter– Made of skeletal muscle– Voluntary– Toilet training!!!

• Stratified squamous epithelium at lower half

pg 398

Defecation

• Stretching of rectal wall initiates defecation reflex

• Mediated by the spinal cord– Parasympathetic reflex signals walls of sigmoid

colon and rectum to contract and anal sphincters to relax

– Involuntary

• If not ready, reflective contraction ends and rectum relaxes– Reflex initiated again until you actually defecate

• Contraction of diaphragm, levator ani and abdominal muscles assist– Voluntary

Accessory Digestive Organs

Liver

• Largest gland in the body!– Weighs about 3 pounds

• Highly vascular• Location:

– Inferior to diaphragm– In right superior part of

abdominal cavity– Mostly upper rib cage

• Functions: (Over 500!)– Produce bile– Pick up glucose– Detoxify poison, drugs– Produce blood proteins

pg 242

Liver Gross Anatomy

• 2 surfaces:– Diaphragmatic– Visceral

• Lobes:– Right lobe– Left lobe

• Divided by:– Falciform ligament on

diaphragmatic surface– Fissure on the visceral

surface

– Quadrate lobe– Caudate lobe

• Both part of left lobe and visceral surface

pg 285

pg 287

Liver – Visceral Surface

• Hepatic Vein (into inferior vena cava)

• Porta Hepatis– Hepatic Artery (from

abdominal aorta )– Hepatic Portal Vein

• Carries nutrient-rich blood from stomach and intestines to liver

• Hepatic portal system = 2 capillary beds!

– Hepatic Ducts (carry bile)

pg 286

Gallbladder • Muscular sac• Rests in depression of

right liver lobe• Has many ducts

associated with it• Stores and

concentrates bile– Breaks down fats– Emulsification – Produced in liver– Stored in gallbladder– Secreted in duodenum

pg 285

pg 287

Gallbladder

• Mucosa– Simple columnar

epithelium – Lamina propria– Expandable mucosal

folds

• Smooth muscle layer

• Thick connective tissue– Covered by serosa

in placespg 287

Bile Ducts

• Hepatic duct– Carries bile from

liver

• Cystic duct– Joins hepatic duct

from liver to form the bile duct

– Carries bile from gallbladder

• Common Bile duct– Empties into the

duodenum

pg 289

pg 290

Movement of Bile

• Bile secreted by liver continuously• Hepatopancreatic (Vater) ampulla

– common bile + main pancreatic duct meet and enter duodenum

– Sphincter of Oddi around it– closed when bile not needed for digestion

• Bile then backs up into gallbladder via cystic duct

• When needed gallbladder contracts, sphincters open

Pancreas• Both exocrine and

endocrine gland• Exocrine

– Produce enzymes that digest food

• Endocrine– Produce hormones that

regulate blood sugar (insulin and glucagon)

• Secondarily retroperitoneal

• Location:– Curve of duodenum– Extends to spleen

pg 288

Pancreatic Ducts• Main pancreatic duct

– Extends length of pancreas– Joins bile duct to form the hepatopancreatic ampulla– Empties into duodenum

• Accessory pancreatic duct– Lies in head of pancreas– Drains into the main duct– Enters duodenum also

pg 289

Spleen

• Largest lymphoid organ• Location:

– Left superior quadrant of abdominal cavity

– Posterior to stomach

• Highly vascular• Function:

– Removes blood-borne antigens

– Removes and destructs aged blood cells

– Site of hematopoiesis in fetus

– Stores blood plateletspg 297

Arterial Blood Supply to Abdominal Viscera

• All branches of Abdominal Aorta• Anastomoses

– Left + Middle colic– Left + Right gastric– Left + Right gastroepiploic– Cranial + Caudal pancreaticoduodenal– Deep Iliac Circumflex + Adrenolumbar

• Remember your zoological roots: YOU MUST KNOW WHAT SUPPLIES WHAT!!

Names give hints!

• Hepato = liver• Pancreatico =

pancreas• Cystic =

gallbladder• Gastro = stomach• Splenic = spleen• Adreno = adrenal gl• Lumbar = lumbar

region

• Epiploic = membrane-covered

• Mesenteric = mesentery

• Duodenal = duodenum

• Ileo = ileum• Colic = colon• Rectal = rectum