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