FA GI Anatomy and Physiology JWM

Medicine Step1 with Mr.boards at University of Chapel Hill

About this deck

By: John Meyer
Created: 2012-03-10
Size: 73 flashcards
Views: 13

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Retroperitoneal Structures

SAD PUCKER

S = Suprarenal (adrenal glands), A = Aorta and IVC, D = Duodenum(all but the 1st part), P = Pancreas, U = Ureters, C = Colon, K = Kidneys, E = Esophagus, R = Rectum (upper 2/3)
GI structures that lack a mesentery and non-GI structures. Injuries can cause blood or gas accumulation in retroperitoneal space

Falciform ligament

Connects liver to anterior abdominal wall.

contains ligamentum teres
Derivative of fetal umbilical vein

Hepatoduodenal

Connects liver to duodenum.

Contains the portal triad: hepatic artery, portal vein, common bile duct
May be compressed between thumb and index finger placed in omental foramen (epiploic foramen of Winslow) to control bleeding
Connects greater and lesser sacs

Gastrohepatic

Connects liver to lesser curvature of stomach.

contains gastric arteries
Separates right greater and lesser sacs
May be cut during surgery to access lesser sac

Gastrocolic

Connects greater curvature of stomach and transverse colon

Contains the gastroepiploic arteries
Part of greater omentum

Gastrosplenic

Connects greater curvature and spleen.

Contains the short gastrics
Separates left greater and lesser sacs

Splenorenal ligament

Connects spleen to posterior abdominal wall

Contains the splenic artery and vein

Layers of gut wall (inside to outside)

1. Mucosa - epithelium (absorption), lamina propria (support), muscularis mucosa (motility)
2. Submucosa - includes Submucosal nerve (Meissner's)
3. Muscularis externa - includes Myenteric nerve plexus (Auerbach's)
4. Serosa/adventitia
So it goes MSMS, mucosa first

Histo, esophagus

nonkeratinized stratified squamous epithelium

Stomach histo

Gastric glands

Duodenum

Villi and microvilli increase absorptive surface.

Brunner's glands (submucosa) and crypts of Lieberkuhn

Jejunum

Has the largest number of goblet cells in the small intestine. Plicae circulares and crypts of Lieberkuhn

Ileum

Peyer's patches (lamina propria, submucosa), plicae circulares (proximal ileum), and crypts of Lieberkuhn

Colon

Crypts but NO villi

Abdominal aorta and which branches go to GI structures

Arteries supplying GI structures branch anteriorly (while those supplying non-GI structures branch laterally)

Celiac trunk, SMA and IMA go to GI structures

Blood supply and innervation, foregut

Celiac artery
Vagus (Parasymp innerv)
T12/L1
Supplies stomach to proximal duodenum; liver, gallbladder, pancreas, spleen (mesoderm)

Blood supply and innervation, midgut

SMA
Vagus (parasymp innerv)
L1
Supplies distal duodenum to proximal 2/3 of transverse colon

Blood supply/innerv, Hindgut

IMA
Pelvic nerve (parasymp innerv)
L3
Supplies distal 1/3 of transverse colon to upper portion of rectum; splenic flexure is watershed region

Branches of celiac trunk

1. Common hepatic 2. splenic 3. left gastric

these constitute the main blood supply of the stomach

Anastomoses of short gastrics, gastrics and gastroepiploics, which are strong and which aren't?

Strong anastomoses between Left and Right gastroepiploics and Left and Right Gastrics
Poor anastomoses (if splenic artery is blocked) between short gastrics

Collateral circulation if abdominal aorta is blocked. The arteries in ( ) are the origin points.

Superior epigastric (internal thoracic/mamary) connect with inferior epigastric (external iliac)
Superior pancreaticoduodenal (celiac trunk) connects to inferior pancreaticoduodenal (SMA)
Middle colic (SMA) connects with left colic (IMA)
Superior rectal (IMA) connects with middle rectal (internal iliac)

Portosystemic anastomoses

1) Left gastric+esophageal vein (esophageal varices)

2) Paraumbilical+superficial and inferior epigastric (caput medusae)

3)Superior rectal+ Middle and inferior rectal (internal hemorrhoids)

Pectinate (dentate) line

Formed where endoderm (hindgut) meets ectoderm

Above pectinate line

Internal hemorrhoids, adenocarcinoma. Arterial supply from superior rectal artery (branch of IMA).

venous drainage is to superior rectal vein to inferior mesenteric vein and then into the portal system

Internal hemorrhoids vs external hemorrhoids

Internal: not painful b/c of visceral innervation; can be a sign of portal htn

External: painful b/c of somatic innervation; inferior rectal artery (off the internal pudendal)

Below the pectinate line

External hemorrhoids, squamous cell carcinoma. Arterial supply from inferior rectal artery (branch of internal pudendal artery).

Venous drainage to inferior rectal vein to internal pudendal vein to internal iliac vein into the IVC

Zones of hepatocytes

Zone I: periportal zone(closest to incoming blood). Affected 1st by viral hepatitis
Zone II: Intermediate zone
Zone III: Pericentral vein (centrilobular) zone: affected 1st by ischemia, contains P450 system, most sensitive to toxic injury, alcoholic hepatitis

Apical/basolateral surfaces of hepatocytes, what they face

Apical surface faces bile canaliculi. Just think AB
Basolateral surface faces sinusoids

Tumor of the head of the pancreas, affect on biliary structures

Since this is near the duodenum, these tumors can cause obstruction of the common bile duct.

How both bile and pancreatic ducts could be blocked

If a gallstone reaches the common channel at ampulla of Vater, it can block both ducts

Mnemonic to organize femoral region

"You go from lateral to medial to find your NAVEL"

Nerve, Artery, Vein, Empty space, Lymphatics

Femoral triangle, and good mnemonic to remember it

"Venous near the penis aka medial"

femoral triangle contains femoral vein, artery, and nerve

Femoral sheath

Fascial tube 3-4 cm below the inguinal ligament.

Contains femoral vein, artery, and canal (deep inguinal lymph nodes) but NOT femoral nerve

Diaphragmatic hernia

Abdominal structures enter the thorax, may occur in infants as a result of defective development of pleuroperitoneal membrane. Most commonly a hiatal hernia, in which stomach herniates upward through the esophageal hiatus of the diaphragm

Sliding hiatal hernia

Most common type of diaphragmatic hernia. GE junction is displaced: "hourglass stomach"

Paraesophageal hernia

GE junction is normal. Cardia moves into the thorax

a type of diaphragmatic hernia

Indirect inguinal hernia

Goes through the INternal (deep) inguinal ring, external (superficial) inguinal ring, and INto the scrotum. Enters internal inguinal ring lateral to inferior epigastric artery. Occurs in INfants owing to failure of processus vaginalis to close (can form hydrocele). Much more common in males.

follows the path of descent of the testes. Covered by all 3 layers of spermatic fascia

Direct inguinal hernia

Protrudes through the inguinal (Hesselbach's) triangle. Bulges directly through abdominal wall medial to inferior epigastric artery. Goes through the external (superficial) inguinal ring only. Covered by external spermatic fascia. Usually in older men.

Direct vs Indirect hernias

"MDs don't LIe"

Medial to inferior epigastric artery = Direct hernia
Lateral to inferior epigastric artery = Indirect hernia

Femoral hernia

Protrudes below inguinal ligament through femoral canal below and lateral to pubic tubercle. More common in women.

Leading cause of bowel incarceration

Gastrin

G cells (antrum of stomach)

Increases gastric H+ secretion, growth of gastric mucosa, and gastric motility
Increased secretion by stomach distention/alkalinization, amino acids, peptides, vagal stimulation. Decreased by stomach pH < 1.5

When you see really high gastrin levels

Zollinger-Ellison syndrome. Phenylalanine and tryptophan are also potent stimulators

Cholecystokinin

Made in I cells of the duodenum and jejunum

Increases pancreatic secretion and gallbladder contraction. Decreases gastric emptying, sphincter of Oddi relaxation
Increased secretion by fatty acids and amino acids
Acts on neural muscarinic pathways to cause pancreatic secretion

Secretin

Made in S cells of duodenum

Increases pancreatic HCO3- secretion and bile secretion. Decreases gastric acid secretion
Increased secretion stimulated by acid, fatty acids in lumen of duodenum
the increased HCO3- it leads to neutralizes gastric acid in duodenum, allowing pancreatic enzymes to function

Somatostatin

Made in D cells(of pancreatic islets, GI mucosa)

DECREASES gastric acid and pepsinogen secretion, pancreatic and small intestine fluid secretion, gallbladder contraction, insulin and glucagon release
Increased amt by acid. Decreased amt by vagal stimulation

General note on Somatostatin, general role

An inhibitory hormone.

Antigrowth hormone effects(digestion and absorption of substances needed for growth

Glucose-dependent insulinotropic peptide (aka gastric inhibitory peptide or GIP)

Made in K cells of duodenum and jejunum

Exocrine function = decrease gastric H+ secretion
Endocrine function = increase insulin release
Increased by fatty acids, amino acids, oral glucose
note that an oral glucose load is used more rapidly than the equivalent given by IV

Vasoactive intestinal polypeptide (VIP)

Made in parasympathetic ganglia in sphincters, gallbladder, small intestine

Inreases intestinal water and electrolyte secretion, relaxation of intestinal smooth muscle and sphincters
Increased amts by distention and vagal stimulation. Decreased amts by adrener input
VIPoma = non-alpha/ beta islet cell pancreatic tumor, Copious diarrhea

Nitric oxide

Increases smooth muscle relaxation, including lower esophageal sphincter
Loss of NO secretion is implicated in increased lower esophageal tone of achalasia

Motilin

Made in small intestine

Produces migrating motor complexes (MMCs)
Increased amts in fasting state
Motilin receptor agonists are used to stimulate intestinal peristalsis

Intrinsic factor

made by parietal cells (stomach)

VitB12 binding protein (required for B12 uptake in terminal ileum)
Autoimmune destruction of parietal cells leads to chronic gastritis and pernicious anemia

Gastric acid

Made in Parietal cells (stomach)

Decreases stomach pH
Increased by histamine, ACh, gastrin. Decreased by somatostatin, GIP, prostaglandin, secretin
A Gastrinoma is a gastrin-secreting tumor that causes continuous high levels of acid secretion and ulcers

Pepsin

Made in chief cells (stomach)

Protein digestion
Increased by vagal stimulation and local acid
Inactive pepsinogen is activated by acidic environment to become pepsin

HCO3-

Made in mucosal cells (stomach, duodenum, salivary glands, pancreas) and Brunner's glands (duodenum)

Neutralizes acid
Increased by pancreatic and biliary secretion with secretin
HCO3- is trapped in mucus that covers the gastric epithelium

Saliva

Secretion from parotid, submandibular, and sublingual glands stimulated by sympathetic and parasympathetic activity. Amylase digests starch, HCO3- neutralizes bacterial acids, mucins lubricate food.

normally hypotonic due to absorption but more isotonic with higher flow rates (less time for absorption)

What cells gastrin works through

remember gastrin is made by G cells in antrum of stomach
It increases acid secretion primarily through its effects on ECL cells (leading to histamine release) rather than through its direct effect on parietal cells
Lots of details on pg. 348, diagrams to review

Brunner's glands

Secrete alkaline mucus to neutralize acid contents entering the duodenum from the stomach.

Located in duodenal submucosa (the only GI submucosal glands).
Hypertrophy of these glands is seen in peptic ulcer disease

Pancreatic secretions

Isotonic fluid;

low flow = high Cl-,

high flow = high HCO3-

Enzymes in pancreatic secretions

alpha-amylase: starch digestion, secreted in active form
Lipase, phospholipase A, colipase: fat digestion
Proteases (trypsin, chymotrypsin, elastases, carboxypeptidases): protein digestion, secreted as proenzymes aka zymogens

Trypsinogen

converted to active enzyme trypsin by enterokinase/enteropeptidase, an enzyme secreted from duodenal mucosa. Trypsin activates other proenzymes and more trypsinogen (positive feedback loop)

Carb digestion, 3 main enzymes

Salivary amylase - starts digestion, hydrolyzes alpha-1,4 linkages to yield disaccharides (maltose and alpha-limit dextrins)
Pancreatic amylase - Highest conc. in duodenal lumen, hydrolyzes starch to oligosaccharides and disaccharides
Oligosaccharide hydrolases = brush border, rate-limiting step, produce monosaccharides

Carb absorption

Only monosaccharides (glucose, galactose, fructose) are absorbed by enterocytes.

Glucose and galactose are taken up by SGLTI (Na+ dependent). Fructose is taken up by facilitated diffusion by GLUT-5.

All are transported to blood by GLUT-2

D-xylose absorption test

Distinguishes GI mucosal damage from other causes of malabsorption

Where and as what is Iron absorbed

Absorbed as Fe++ in duodenum

Where is folate absorbed

In jejunum

Where is vitB12 absorbed and what does it require

Absorbed in ileum along with bile acids. Requires intrinsic factor for its absorption.

Peyer's Patches, where is it and what special cells does it have(nothing about IgA in this card)

Unencapsulated lymphoid tissue found in lamina propria and submucosa of small intestine. Contains specialized M cells that take up antigen.

Peyer's Patches and relation with immunoglobulins

B cells stimulated in germinal centers of Peyer's patches differentiate into IgA-secreting plasma cells, which ultimately reside in lamina propria. IgA receives protective secretory component and is then transported across epithelium to gut to deal with intraluminal antigen.

think of IgA as the Intra-gut Antibody. And always say "secretory IgA"

Bile, composition

Composed of bile salts (bile acids conjugated to glycine or taurine, making them water soluble), phospholipids, cholesterol, bilirubin, water and ions.

Bile, functions

Digestion and absorption of lipids and fat-soluble vitamins
Cholesterol excretion (body's only means of eliminating cholesterol)
Antimicrobial activity (via membrane disruption)

Bilirubin

Product of heme metabolism. Bilirubin is removed from blood by liver, conjugated with glucoronate, and excreted in bile. The enzyme uridine glucuronyl transferase is what catalyzes the conjugation(and it is in the liver)

Direct bilirubin = conjugated with glucuronic acid; water soluble
Indirect bilirubin = unconjugated; water insoluble

Bilirubin in macrophages and bloodstream

Spleen macrophages filter blood. RBCs to heme to unconj bilirubin
unconj bilirubin goes around in blood, and slpenic vein feeds it into portal vein. Every pass, 20% is taken up by hepatocytes and converted to conjugated bilirubin
Only source of conjugated bilirubin in blood is small normal reflux from hepatocytes

Bilirubin in liver and gut

Conjugated bilirubin (or direct bilirubin) is water soluble and made in liver thanks to uridine glucoronyl transferase.

gut bacteria turn it into Urobilinogen. 20% goes back, and 90% of that 20% re-enters enterohepatic circulation and 10% excreted in urine as urobilin
80% of all Urobilinogen is excreted in feces as stercobilin

About this deck

By: John Meyer
Created: 2012-03-10
Size: 73 flashcards
Views: 13

About StudyBlue

“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis