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
www.templejc.edu
Abdominopelvic
Cavity
• Surrounded by the abdominal walls and
pelvic girdle
• The two cavities are continuous
• Most organs surrounded by a peritoneal
cavity
– Visceral peritoneum
– Parietal peritoneum
– Peritoneal cavity
pg 254
Abdominal Quadrants
• 9 regions
• 4 quadrants
– Draw “line” through
navel
– Right upper quadrant
– Left upper quadrant
– Left lower quadrant
– Right lower quadrant
pg 268
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 383
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 276
Anterior Abdominal Wall Muscles
• 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)
• 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 276, 277
Anterior Abdominal Wall pg 276
• Transversus Abdominis
pg 275
– Origin
• Inguinal ligament, lumbar fascia, cartilage of last 6 ribs, iliac crest
– Insertion
• Linea alba, pubic crest
– Function
• Compress abdominal contents
 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
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 350
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 350
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
• Ventral mesenteries:
pg 296
pg 324
– Lesser omentum and Falciform ligament
• Dorsal mesenteries:
pg 295, 297
– Greater omentum, Transverse mesocolon,
Mesentery proper, and Sigmoid mesocolon
Peritoneum
• Intraperitoneal
– Organs remain surrounded by peritoneal cavity
– Liver, stomach, ileum and jejunum, transverse colon
• 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
Urinary System
• Kidney (2)
– Purify blood
• Ureter (2)
– Drains urine from kidney to bladder
• Urinary Bladder
– Stores urine
• Urethra
pg 341
– Drains urine from bladder to outside body
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
Hilum
– Where blood vessels, ureters, and nerves enter and leave kidney
• Adrenal gland
– On superior portion
– Endocrine
• Cortisol
• Aldosterone
• Adrenaline
pg 360
Kidney: Gross Anatomy
Internal
• 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
pg 357
• Cushions kidney
• Keeps kidney in place
External
Kidney: Internal Gross Anatomy
• Cortex
– Superficial
– Lighter zone
– Functional portion
• Medulla
–
–
–
–
pg 358
Deep
Darker zone
Pyramid shaped
Contains collecting tubules
Kidney: Gross Anatomy
• Separated into lobes
– Medulla pyramid & associated cortex
• Blood supply
– Renal artery and vein
• Innervation
– Branches of renal plexus
pg 358
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
– Minor calices
• Collect urine from papilla
• Surround papilla of pyramids
• Empty into major calices
– Major calices
• Receive urine from several minor calices
• Empty into renal pelvis
• Renal pelvis
– Funnel-shaped
– Empties urine into ureter
pg 358
Kidney: Microscopic Anatomy
• Uriniferous tubules
– Produces urine through filtration, reabsorption, and
secretion
– 2 major part:
• Nephron
• Collecting duct
www.uptodate.com
www.incostress.com
•
•
•
•
•
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 360
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
faculty.une.edu
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 442
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 441
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
pg 442
• Fibrous CT
• Parietal peritoneum on superior surface
Urethra
• Drains urine from bladder to outside of
body
• Opens at the external urethral orifice
• Female:
– Short tube
• Male
– 3 regions
pg 442
• Prostatic urethra
• Membranous urethra
• Spongy/penile urethra
– Also carries ejaculating semen
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
pg 445
Micturition = Urination
• Contraction of the detrusor muscle to raise intraabdominal 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
• Alimentary Canal
–
–
–
–
–
–
Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
• Accessory Organs
–
–
–
–
–
Teeth, Tongue
Salivary Glands
Gallbladder
Liver
Pancreas
pg 248
Digestive Processes – 6 Steps
• Ingestion
– Taking food into the mouth
• Mechanical digestion
– Prepares food for chemical digestion
– Chewing, churning, segmentation
• Propulsion
– Movement of food through GI tract
• Swallowing and peristalsis
• 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
pg 347
– Serosa / Adventitia
Peristalsis vs
Segmentation
• Peristalsis
www.answers.com
– 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
www.3dscience.com
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
Innervation
• 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
pg 313
Stomach
• J-shaped, Temporary storage tank
• Intraperitoneal
• Regions:
– Cardiac
• Cardiac orifice
• Junction of esophagus
– Fundus
• Under diaphragm
– Body
• Large midportion
– Pyloric
• Ends at the stomach
• Pyloric sphincter
pg 299
– Greater curvature
– Lesser curvature
www.acm.uiuc.edu
Stomach – Internal Anatomy
• Mucosa
– Epithelium
• Simple columnar
– Rugae
• Folds that allow for volume changes
– Intrinsic glands
• Goblet cells
• Gastric glands
– Parietal cells
– Enteroendocrine cells
– Chief cells
• 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!!
www.nlm.nih.gov
Small Intestine
• Location:
– From pyloric sphincter to first part of the large
intestine
• Regions:
– Duodenum (5%)
• Proximal
– Jejunum (almost 40%)
• Middle
– Ileum (almost 55%)
• Distal
pg 300
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
– Duodenal glands:
• Neutralize acid from stomach
• Jejunum and ileum
–
–
–
–
–
Highly coiled
Intraperitoneal
Fewer modifications
Hang by mesentery in peritoneal cavity
Mesentery Arcades
• Arteries + veins
• Nerves
• Store fat
www.si.mahidol.ac.th
Small Intestine Internal Anatomy
• Intestinal flora
– produces vitamin K
• Epithelium:
– Simple columnar epithelium with many modifications
for absorption
– Goblet cells
– Enteroendocrine cells
• Lymph tissue in submucosa
• Muscularis externa has 2 layers
• Innervation:
– Some parasympathetic innervation from vagus
• Arterial supply:
pg 311
– Superior mesenteric
– Rt (cranial) pancreaticoduodenal
SI Absorption Modifications
www.siumed.edu
www.cartage.org.lb
• Length
– More length, more area for absorption!
• Plicae Circulares
– Transverse ridges of mucosa
– Increase surface area
– Force chyme to slow down
• Villi
– Evagination of plicae circulares
– Move chyme and increase contact
– Contain lacteals
• Remove fat
• Microvilli
– Further increasing of the surface area
Modifications decrease distally
Large Intestine
• Regions:
– Cecum
– Vermiform appendix
– Colon
• Ascending
• Transverse
• Descending
• Sigmoid
– Rectum
– Anal Canal
pg 311
Large Intestine
• Overall 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
Cecum and
Vermiform Appendix
• Cecum
– Sac-like pouch (blind pouch)
– Intraperitoneal
– Ileocecal valve
• 2 raised edges of the mucosa
• Prevents reflux of feces from cecum to ileum
• Vermiform Appendix
– Tubular pouch
– Opens into cecum
– Contains large masses of lymphoid tissue
assets.aarp.org
pg 302
Colon 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
pg 279
– Fat-filled pouches of visceral peritoneum
– Hang from the intestine
Colon Segments
• Ascending
– Retroperitoneal
– Right side of posterior abdominal wall
– Makes right angle turn
• Right colic / hepatic flexure
• Transverse
– Intraperitoneal
– Extends left across the peritoneal cavity
– Bends downward at the spleen
• Left colic / splenic flexure
• Descending
– Retroperitoneal
– Left side
• Sigmoid
– Intraperitoneal
– S-shaped
– “False pelvis”
pg 311
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
Retroperitoneal
Complete and well-developed longitudinal
muscle layer
• Rectal valves
– 3 transverse folds
– Prevent feces from being passed along with gas
pg 312
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 440
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 sphincter 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
Liver
• Largest gland in the body!
– Weighs about 3 pounds
• Highly vascular
• Location:
– Inferior to diaphragm
– In right superior part of abdominal cavity
– Mostly under rib cage
• Functions: (Over 500!)
–
–
–
–
Produce bile
Pick up glucose
Detoxify poison, drugs
Produce blood proteins
pg 268
pg 317
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
pg 318
Liver – Visceral Surface
pg 318
• Hepatic Vein (into inferior vena cava)
• Porta Hepatis
– Common Hepatic Artery (from celiac trunk)
– Hepatic Portal Vein
• Carries nutrient-rich blood from stomach and
intestines to liver
• Hepatic portal system = 2 capillary beds!
– Hepatic Ducts (carry bile)
Gallbladder
pg 317
•
•
•
•
Muscular sac
Rests in depression of right liver lobe
Has many ducts associated with it
Stores and concentrates bile
–
–
–
–
Emulsification
Produced in liver
Stored in gallbladder
Released into the duodenum
pg 319
Gallbladder
• Mucosa
– Simple columnar epithelium
– Lamina propria
– Expandable mucosal folds
• Smooth muscle layer
• Thick connective tissue
– Covered by serosa in places
pg 319
pg 321
Bile Ducts
pg 323
• 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
Movement of
Bile
pg 321
• 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
pg 320
• Both exocrine and endocrine gland
• Exocrine
– Produce enzymes that digest food
• Endocrine
– Produce hormones that regulate blood sugar
(insulin and glucagon)
• Secondarily retroperitoneal (mostly)
• Location:
– Curve of duodenum
– Extends to spleen
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
pg 321
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 platelets
pg 331
Arterial Blood Supply to
Abdominal Viscera
• All branches of Abdominal Aorta
• Anastomoses
–
–
–
–
Left + Middle colic
Left + Right gastric
Left + Right gastroepiploic
Cranial + Caudal pancreaticoduodenal
• 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