Organs of Abdomen lecture presentation

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
• Parietal peritoneum
• Peritoneal cavity

Abdominal Quadrants

• 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

 
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

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)

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

Anterior Abdominal Wall

• Transversus Abdominis
• 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, T 12
• 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)
• 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)

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:
• Lesser omentum and Falciform ligament
• Dorsal mesenteries:
• 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
• 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
• 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

Kidney: Gross Anatomy
Internal

Extcernal

• 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

Kidney: Internal Gross Anatomy

• Cortex
• Superficial
• Lighter zone
• Functional portion
• Medulla
• 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

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

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!!

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

• 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

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 surface

Urethra

• Drains urine from bladder to outside of body
• Opens at the external urethral orifice
• Female:
• Short tube
• Male
• 3 regions
• Prostatic urethra
• Membranous urethra
• Spongy/penile urethra
• Also carries ejaculating semen
• 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

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

• Alimentary Canal
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine
• Accessory Organs
• Teeth, Tongue
• Salivary Glands
• Gallbladder
• Liver
• Pancreas

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
• 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

www.answers.com
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

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
• Greater curvature
• Lesser curvature

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
• H 2O, 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

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

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:
• Superior mesenteric
• Rt (cranial) pancreaticoduodenal

SI Absorption Modifications

• 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

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

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

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
• 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”

Colon Functions

• Absorb H 2O 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

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

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

Liver – Visceral Surface

• 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

• 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

Gallbladder

• Mucosa
• Simple columnar epithelium
• Lamina propria
• Expandable mucosal folds
• Smooth muscle layer
• Thick connective tissue
• Covered by serosa in places

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

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 (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

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

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