Embryology of Abd Wall and Cavity Lecture
The Ventral Mesentery is derived from the Septum Transversum and gives rise to the
ligaments of the liver
GI tract formed from endoderm
intraperitoneal–completely covered with visceral peritoneum
liver, stomach, proximal ⅓ duodenum, tail of pancreas, jejunum, ileum, transverse colon
retroperitoneal–partially covered with parietal peritoneum
SAD PUCKER→suprarenal gland, aorta/IVC, distal duodenum, pancreas head and body,
ureters, colon (ascending and descending), kidneys, esophagus, rectum
Foregut–celiac artery, CN10
Midgut–superior mesenteric artery, CN10
Hindgut–inferior mesenteric artery, sacral spinal cord segments S2-4
RUQ
R lobe of the liver
Gallbladder
Pylorus of the stomach
Duodenum
Pancreas head
R kidney
R adrenal gland
Hepatic flexure
Distal portion of the R half of transverse colon
Superior portion of the ascending colon
LUQ
L lobe of the liver
L half of transverse colon
Splenic flexure
Spleen
Stomach
L kidney
L adrenal gland
Pancreas body and tail
Superior descending colon
RLQ
Ileum
Cecum
Appendix
inferior portion of the ascending colon
R ovary
R uterine tube
R ureter
R spermatic cord
Uterus–is enlarged
Bladder–if full
LLQ
Descending colon
Sigmoid colon
Rectum
L ovary
L uterine tube
L ureter
L spermatic cord
Uterus–is enlarged
Bladder–if full
Carbs(the enemy)→simple sugars
Fats→triglycerides
proteins→AA
Digestive Tract and Abdominal Viscera Lecture
Digestive tract MAJOR process→elimination
Enteric nervous system largely fxns independently from the CNS BUT CNS sends parasymp
control via CN 10 and sacral segments S2-4
MOUTH:
● Teeth
○ Incisors–cut
○ Canines–pierce, tear, and rip
○ Premolars, molars–grind and crush
●
Salivary Glands–produce saliva (serous fluid→mostly water and proteins→resembles
serum)
●
○
Submandibular gland→serous and mucus (CN7)
○
Sublingual gland→serous and mucus (CN7)
○
Parotid gland→serous (CN9)
Salivary Amylase and Lingual Lipase separate from pancreatic enzymes
ESOPHAGUS:
● The oropharynx and esophagus convey food, fluids, and oral secretions to the
stomach via? Deglutition
●
Stroke of vertebrobasilar artery→dysphagia
●
Upper ⅓ lined with skeletal muscle→voluntary control
●
Lower ⅔ lined with smooth muscle→ENS control→involuntary control
●
EsophagoGastric Jxn
○
Z-line→jagged line demarcating the abrupt transition from esophageal to gastric
mucosa
DIAPHRAGM:
● Hiatuses (I 8 10 EGGs AT 12)--holes in diaphragm thru which certain structures go thru
and their vertebral levels
○
T8→IVC
○
T10→Esophagus and Vagus
○
T12→Aorta, Azygos and Thoracic Duct
STOMACH:
●
Which of the following areas of the GI tract includes an additional muscular layer?
○
stomach → longitudinal, circular, oblique
●
Parietal cells–oxynitic cells
○ Secrete HCl and intrinsic factor (extrinsic factor absorption)
●
Chief cells–pepsinogen→pepsin with acid
●
Enteroendocrine cells
○
G cells→ON SWITCH
■
○
Gastrin→stimulate parietal cells
D cells→OFF SWITCH
■
Somatostatin→inhibit parietal cells
INTESTINES:
● Meissner’s Plexus (Submucosal–Sensory)
● Auerbach’s Plexus (Myenteric–Motor)
●
Plica Circularis→increase surface area/volume ratio
●
Peyer’s patches aka GALT aggregation of lymphoid tissue found throughout GI tract
●
●
●
●
●
EXCEPT STOMACH
○ Most prominent in the ileum and large intestine
Muscular layer of the intestine
○ Inner circular layer
○ Myenteric plexus–Auerbach
○ Outer longitudinal layer
Duodenum
○ Brunner’s glands AKA Duodenal glands
○ Panneth cells–secrete antimicrobial peptides
Jejunum
○ Plica circularis most prominent in the jejunum
○
Ileum
○ Peyer's patches
Large intestine
○ Peyer’s patches
○ Goblet cells
PANCREAS:
● Exocrine and endocrine fxns
● Head
○ RUQ
○ Retroperitoneal
○ Uncinate process
● Neck
○ R/LUQ
○ Retroperitoneal
● Body
○ LUQ
○ Retroperitoneal
● Tail
○ LUQ
○ Intraperitoneal–fully covered by visceral peritoneum
SPLEEN:
● LUQ
● Left hypochondriac below costal cartilage
LIVER:
● Second largest organ
● Skin the largest organ
● Porta hepatis contains the portal triad
○ Bile duct
○ Hepatic portal vein
○ Hepatic artery
● 4 anatomical/structural lobes
○ R and L
○ Caudate and Quadrate
● 2 fxnal lobes
●
●
●
○
R lobe→supplied by R hepatic artery
○
L lobe–including caudate and quadrate→supplied by L hepatic artery
True ligaments are remnants of fetal vessels:
○ Ligamentum teres aka round ligament used to be umbilical vein
○ Ligamentum venosum used to be ductus venosus
False ligaments:
○
Falciform→attaches liver to anterior abdominal wall
○
○
R and L triangular
Ant and Post Coronary
Superior aspect of the liver→bare area–not covered by peritoneal lining
●
Liver sinusoids
○ Kuppfer cells–macrophages
■ Remove expired RBCs
■ Fight infection
PORTAL SYSTEM:
● Portal vein is formed by the Splenic and Superior Mesenteric Veins & gastric veins
JEJUNUM:
●
Microvilli→brush border
●
Plica circularis
ILEUM:
● Peyer’s patches
ASCENDING COLON/PROXIMAL ⅔ of TRANSVERSE COLON:
● Peyer’s patches
● Haustra
● Taenia coli
○ Mesocolic
○ Omental
○ Free
DISTAL ⅓ of TRANSVERSE COLON/DESCENDING COLON/SIGMOID
COLON/RECTUM/ANAL CANAL:
●
Internal anal sphincter→involuntary
●
External anal sphincter→voluntary
Referred pain from and to
●
Foregut structures→Epigastric
●
Midgut structures→Umbilical
●
Hindgut structures→Hypogastrium
Innervation of Abdomen Lecture
Although considered efferent, sympathetic and parasympathetic fibers CAN and DO
carry afferent/sensory signals
ANS
●
Sympathetic–Splanchnic nerves
○ Pre ganglionic cells located in Lateral horns T5-L2
○ Post ganglionic cells located in
■ Paravertebral ganglia
● Sympathetic chain ganglia
■ Prevertebral ganglia
○
●
●
Superior cervical ganglia→esophagus
●
Celiac ganglia→foregut
●
Superior mesenteric ganglia→midgut
●
Inferior mesenteric ganglia→hindgut
Neurotransmitters
■ NE
■ Neuropeptide Y
■ enkephalins
○ Fxn
■ Decrease blood flow
■ Inhibit glandular secretion and GI motility
Parasympathetic
○ Pre-gg cells in dorsal motor nucleus of CN 10 and nucleus Ambiguus
■ Exit thru jugular foramen
○ Post-gg cells located near target organs/tissues
○
○
Neurotransmitters
■ Ach
■ Substance P
■ Gastrin-releasing peptide
■ Vasoactive intestinal peptide
Fxn
■ Increase GI blood flow, glandular secretion, and motility
Enteric NS
● Nerve cell bodies in small ganglia within Meissner’s (Submucosal–Sensory) and
Auerbach’s (Myenteric–Motor) Plexuses
● Meissner’s (Submucosal–Sensory)
○ Monitor wall tension, wall integrity, pH/osmolality/nutrient levels of
intestinal contents
● Auerbach’s (Myenteric–Motor)
○ Vasoconstriction/dilation of blood vessels
○ Control of circular and longitudinal smooth muscle, secretory glands, endocrine
cells, and absorptive epithelium
○ Peristalsis
●
■
Bolus→chyme in the stomach
■
Retrograde-peristalsis→vomitting
○ GI motility
○ Sphincter control
Enteric glial cells that support ENS neurons are analogous to which cells of the
CNS?
○ Astrocytes
**Memorize tables x 3***
GI Neurotransmitters and Neuromodulators
Parasympathetic/Enteric–GI TRACT ON SWITCH
Ach
Contracts wall muscle
Relaxes sphincters
Increases salivary, intestinal, and pancreatic secretions
Vasoactive
Intestinal Peptide
Relaxes sphincters
Increases salivary, intestinal, and pancreatic secretions
Gastrin-Releasing
Peptide
Increases gastrin secretion
Stimulates mucosal hypertrophy
Substance P
Contracts wall muscle
Increases salivary secretions
Sympathetic/Enteric–GI TRACT OFF SWITCH
NE
Relaxes wall muscle
Constricts sphincters
Decreases secretions
Neuropeptide Y
Relaxes wall muscle
Decreases secretions
Enkephalins
Constricts sphincters
Decreases secretions
GI Hormones
Hormone
Secretory Cell
Fxn
GI TRACT ON SWITCH
CCK
I cells in duodenum and
jejunum
Inc enzyme secretion,
contract GB, inc gastric
emptying
Gastrin
G cells in antrum
Increase acid secretion
(from the parietal cells)
Motilin
M cells in upper GI tract
Increase GI motility
Secretin
S cells in SI
Release bicarb and pepsin
GI TRACT OFF SWITCH
Glucose-dep Insulinotropic
Peptide
K cells in duodenum and
jejunum
Release insulin, inhibit acid
secretion
Somatostatin
D cells in stomach,
duodenum, and pancreas
Inhibits gastric acid
secretion
GI Paracrines–GI TRACT ON SWITCH
Paracrine
Secretory Cell
Fxn
Histamine
enterochromaffin-like cells
and mast cells
increase gastric acid
secretion
PGs
cells lining GI tract
increase mucus secretion,
bicarb secretion, and blood
flow
Digestion and Absorption Lecture
Stomach
● Body:
○ Parietal cells
○
■
HCl→activates pepsinogen to pepsin
■
Intrinsic Factor→needed to absorb Extrinsic Factor is B12
Chief cells
■
●
Pepsinogen→pepsin via acid
Antrum:
○ D cells
■
○
Somatostatin→inhibits GI tract and secretions via inhib. of parietal cell
G cells
■
Gastrin→stimulates GI tract and secretion via stim. of parietal cells
Exocrine fxns of the pancreas
Intercalated ducts→interlobular ducts→accessory and main pancreatic ducts
●
Acinar cells→synthesize and secrete digestive enzymes that break down different
macromolecules and nucleic acids:
○
○
○
○
Carbs
■ Amylase
Lipids
■ Lipase
■ Phospholipase
■ Phospholipase A2
Proteins
■ All of the following enzymes digest proteins except?
■
Chymotrypsinogen→chymotrypsin
■
Trypsinogen→trypsin
■ Procarboxypeptidase A & B
■ Proelastase
Nucleic Acids
■
deoxyribonuclease→DNA
■
ribonuclease→RNA
●
Ductal cells→secrete bicarb with the help of carbonic anhydrase
●
Intercalated ducts→lined with ductal cells; empty into interlobular ducts
●
Interlobular ducts→empty into pancreatic and accessory pancreatic ducts
●
Pancreatic duct→joined by the common bile duct at the Ampulla of Vater that empties
into the major duodenal papilla (accessory pancreatic duct empties into the minor
duodenal papilla)
Liver
●
●
Bile acid recycling via the enterohepatic circulation
○ Unconj bile acids reabsorbed passively in the terminal ileum and large intestine
Metabolism
○
Carbs→gluconeogenesis (generation of glucose) and glycogenolysis (breakdown
glycogen into glucose)
○
Lipids→converts AA and carbs into lipids; mobilizes FAs thru lipolysis for release
into circulation to be used for energy
○
Proteins→breakdown of protein into AA and synthesis of plasma proteins such as
albumin
■
Albumin–transport and maintain colloid osmotic pressure
●
●
Storage of fat soluble vitamins and minerals
○ ADEK; iron, copper, magnesium
Detox
○
●
●
Ammonia→urea via urea cycle
○ Alcohol metabolized via alcohol dehydrogenase
Drug biotransformation
○ Phase 1–oxidation
■ Used to activate ACE-I
○ Phase 2–conjugation and elimination
Immune fxns
○ Kuppfer cells are specialized macrophages that engulf and remove intestinal
bacteria and RBC fragments from spleen
Small Intestine
● Secretions
○ Enteroendocrine cells secrete:
■
CCK→contracts GB, increase GI secretions, promote gastric emptying
■
Secretin→releases bicarb and pepsin
■
Glucose-dependent Insulinotropic Peptide→inhibits acid secretion,
releases insulin
●
Digestion and absorption
○ Carbs:
■ 4kcal/g
■ broken down by amylase (salivary and pancreatic)
■
○
○
Absorption into the portal system→active transport EXCEPT fructose,
which is via facilitated diffusion
Proteins:
■ 4kcal/g
■ Absorption across epithelial lining of SI via CoTransport; into the
portal system via facilitated diffusion
Lipids
■ 9kcal/g
■
TriAcylGlycerols (TAGs)→Free FAs→Small, Medium, and Long Chain FA
●
■
Small and medium chains are water soluble and can therefore
cross epithelium via diffusion
● LCFAs are less soluble and form micelles
○ Once in the portal system they are assembled into
chylomicrons and exocytosed into the lymphatic
system
Emulsification–process whereby fats/lipids are mechanically broken
down into smaller droplets
■
■
■
Pancreatic lipase is the primary enzyme for digesting TAGs
Cholesterol esterase digest cholesterol
Phospholipase A2 targets glycerophospholipids such as
phosphatidylcholine
Large Intestine
●
GastroColic Reflex→IleoCecal valve opening in response to Gastrin and CCK when food
is present in the stomach/duodenum
●
Water/electrolyte reabsorption
○ Proximal colon via Na/H exchanger
○ Distal colon via Na channels regulated by aldosterone
Endocrine Glands Lecture
Amines→(derived from tyrosine) catecholamines and thyroid hormones
Peptide/proteins
Steroids
Catecholamines
(Amine)
Thyroid hormones
(Amine)
Synthesis
Synthesized and
stored in
secretory
vesicles
Synthesized in the ER
Synthesized and
stored in secretory
vesicles
Synthesized in the
ER
Transport
Water soluble,
unbound in
bloodstream
Largely not water
soluble, bound to
carrier proteins
Water soluble,
unbound in
bloodstream
Largely not water
soluble, bound to
carrier proteins
Mech of
Action
Bind to surface
Testosterone (lipid
Bind to surface
receptors→
soluble)→passes
receptors→hormone-
hormone-
directly thru the cell
receptor complex
receptor
membrane to bind
activates second
Passes directly thru
the cell membrane to
bind intracellular
receptors that either
activate or inhibit
transcription
complex
intracellular receptors
messenger
activates second that either activate or
system→protein
messenger
modification and
inhibit transcription
system→protein
modification and
synthesis
initiated
Other steroids bind to
surface receptors and
activate second
messenger systems
synthesis initiated
**peptide/proteins & catecholamines; steroids & thyroid hormones have the same
syn/transport/MOA
Hypothalamic-Pituitary Axis
Pituitary gland(hypophysis)
Posterior→Neurohypophysis
ADH (vasopressin)→binds to vascular smooth muscle receptors causing
vasoconstriction; released in response to hypovolemia
Oxytocin→secretion/ejection of breast milk
**prolactin signals to breastmilk production (ant. pit.)
Anterior→Adenohypophysis
Hypothalamus→embryologically derived from diencephalon
Plugs into the pituitary gland via 2 different sets of axons:
Neuroendocrine axons→posterior pituitary
Hypothalamic-Hypophyseal portal system→anterior pituitary
4 releasing, 2 inhibiting
GH releasing and inhibiting hormones
GHIH aka Somatostatin
Prolactin inhibiting hormone aka Dopamine
Adrenal glands
Cortex→from mesoderm
“GFR”
Zona Glomerulosa→mineralcorticoids (aldosterone)
Zona Fasciculata→glucocorticoids (cortisol)
Zona Reticularis→androgens (testosterone, progesterone, estrogen, DHEA)
Medulla→from neuroectoderm
catecholamines (epi, NE)
Thyroid Hormones
T3–Triiodothyronine→active form
T4–Thyroxine→produced in greater quantity compared to T3
Increase CO and vent
Increase BMR
Increase body temp
CNS maturation and maintenance
Synthesis of new proteins→work with GH to facilitate growth and maturation of the
neuro-MSK system
Thyroid hormone pathway
Thyroglobulin (TG)–very rich in Tyrosine Residues
Thyroid peroxidase (TPO) catalyzes 4 rxns:
Converts ioDIDE to ioDINE
Attaches ioDINE to Tyrosine Residue→MIT and DIT (Mono-Iodo, Di-Iodo
Tyrosine)
Couples 2 DITs→T4
Couples 1 DIT and a MIT→T3
T3 and T4 are transported to target proteins via Thyroxine-Binding Globulin
Target tissues have an enzyme that converts T4 to T3
Parathyroid
PTH is secreted by Chief Cells in response to low concentrations of Ca2+
Regulation of Ca2+, phosphate (PO43-)
Bone
● Episodic/pulsed release of PTH
○ Increase in new bone synthesis (can be used as tx for
osteoporosis)
● Prolonged release of PTH
○
Old bone resorption→releasing Ca2+, phosphate (PO43-)
Kidneys (Nephron)
● Increases Ca2+ reabsorption at the DCT
● Decreases PO43- reabsorbtion at the PCT
● Activates vitamin D
Ca2+ imp for:
blood coag cascade, muscle contraction, nerve conduction, enzyme
activation/deactivation
Phosphate imp for:
cellular metabolism (ATP), enzyme activation/deactivation
Vitamin D
Bone
● Increase new bone synthesis
● Increase old bone resorption
Kidneys (Nephron)
● Increases Ca2+ reabsorption at the DCT
● Decreases PO43- reabsorption at the PCT
Small intestine
● Increases Ca2+ and PO43- absorption
Vit D deficiency→rickets in children
Ca2+ deficiency
HYPERreflexia
Chvostek’s sign→facial nerve twitching when the facial nerve is tapped
Trousseau’s sign→involuntary hand and feet spasms when subjected to
prolonged hyperinflation of a BP cuff
Endocrine fxns of the pancreas
Islets of Langerhans (cluster of 4 different cell types):
Alpha→secrete glucagon→increase blood glucose and FA concentration
Glucagon (hormone of starvation) promotes:
Gluconeogenesis–lipids/proteins→glucose
Glyconeogenesis–lactic acid→glycogen
Glycogenolysis–glycogen→glucose
Beta→secrete insulin→decrease blood glucose, AA, FA, and K+
Insulin (hormone of excess) also released in response to incretins
Delta→secrete somatostatin
F cells