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
pg 242
– Visceral peritoneum
– Serous peritoneum
– Peritoneal cavity
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)
pg 345
– Tendinous line
– Extends from xiphoid
process to pubic symphysis
Muscles
• Function:
– Help contain abdominal
organs
– Move trunk
– Forced breathing
– Increase intra-abdominal
pressure
• Abdominal wall
– Anterior (4)
pg 250
• 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)
Anterior Abdominal Wall Muscles

pg 250, 251
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
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
pg 249
• Linea alba, pubic crest
– Function
• Compress abdominal contents
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 271
pg 269
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
pg 314
– 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
• Hilus
– Where blood vessels,
ureters, and nerves enter
and leave kidney
pg 325
• Adrenal gland
– On superior portion
Kidney: Gross Anatomy
• Separated into lobes
• Blood supply
– Renal artery and vein
– ¼ heart’s systematic
output reaches the
kidney
• Innervation
pg 323
– Branches of renal
plexus
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
pg 322
– Renal fascia
– Pararenal fat
• Cushions kidney
• Keeps kidney in place
External
Kidney: Internal Gross Anatomy
• Cortex
– Superficial
– Lighter zone
– Functional portion
• Medulla
pg 323
–
–
–
–
Deep
Darker zone
Pyramid shaped
Contains collecting
tubules
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
pg 323
– Minor calices
• Divisions of major calices
• Surround papilla of pyramids
• Collect urine from papilla
• Renal pelvis
– Expanded superior part of ureter
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
pg 323
• Interlobular arteries
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:
pg 399
– Branches of the
hypogastric plexus
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 400
• Fibrous CT
• Parietal peritoneum on superior
surface
Urethra
• Drains urine from
bladder to outside of
body
• Female:
– Short tube
• Male
– 3 regions
• Prostatic urethra
• Membranous urethra
• Spongy/penile urethra
pg 400
– Opens at the external
urethral orifice
– 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
Males versus Females:
pg 403
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
Digestive System
• Alimentary Canal
–
–
–
–
–
–
Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
• Accessory Organs
–
–
–
–
–
pg 222
Teeth, Tongue
Salivary Glands
Gallbladder
Liver
Pancreas
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
pg 313
• Inner circular
• Outer longitudinal
• Creates sphincters
– Serosa / Adventitia
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
pg 272
– Greater curvature
– Lesser curvature
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
pg 283
• Arteries + veins
• Nerves
• Store fat
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:
pg 283
– Superior mesenteric
– Rt (cranial)
pancreaticoduodenal
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
pg 279
– Fat-filled pouches of
visceral peritoneum
– Hang from the intestine
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 welldeveloped 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
pg 285
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 287
pg 286
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 285
Gallbladder
• Muscular sac
• Rests in depression of
right liver lobe
• Has many ducts
associated with it
• Stores and concentrates
bile
–
–
–
–
–
pg 287
Breaks down fats
Emulsification
Produced in liver
Stored in gallbladder
Secreted in duodenum
Gallbladder
• Mucosa
– Simple columnar
epithelium
– Lamina propria
– Expandable mucosal
folds
• Smooth muscle layer
• Thick connective
tissue
– Covered by serosa in
places
pg 287
Bile Ducts
• Hepatic duct
pg 289
– 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 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
pg 288
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
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 platelets
pg 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