Gastrointestinal system

Where is the esophagus located

runs from the pharynx to the stomach

What are the 2 sphincters of the esophagus

upper and lower

What is the upper sphincter

pharyngo-esophageal

What is the lower sphincter

gastro-esophageal

What are the two orifices of the stomach

cardiac and pyloric

What is the cardiac orifice

opening for the esophagus

What is the pyloric orifice

beginning of the duodenum

What are the components of the stomach

fundus, body, pyloric

What is the fundus

superior part above the cardiac orifice

What is the body of the stomach

above the notch in the lesser curvature, below the fundus

What is the pyloric

junction with the duodenum

What are the components of the pyloric

pyloric antrum, pyloric canal, pyloric sphincter

Where does the small intestine extend from

the pylorus of the stomach to the cecum

What are the pieces of the duodenum

superior, descending, horizontal and ascending portions: almost circular

What does large intestine extend from

from the ileum to the anus

What is a portion of the large intestines

the colon

What are the 3 regions of the colon

ascending, transverse, and descending

The colon has right and left

colic flexures

What is the tenia coli

three bands of smooth muscle on outside of colon

What is produced by tenia coli

haustra; sacculated

What is the largest gland in the body

liver

What is the vasculature of the liver

highly vascularized

What is the liver attached to

by ligaments to the under surface of the diaphragm, anterior wall of he abdomen, and the lesser curvature of the stomach to the duodenum

What is the blood supply of the liver

25% hepatic artery

75% portal vein

What forms the common hepatic duct

the left and right hepatic ducts

What does the common hepatic duct join from the gall bladder to form the common bile duct

cystic duct

The common bile duct combines with what before entering the duodenum

pancreatic duct

What membrane does the peritoneum have

serous membrane; single layer of mesothelium over a delicate layer of connective tissue

What does the parietal peritoneum do

lines inferior surface of diaphragm and the abdominal and pelvic walls

What is the peritoneal cavity

potential space between the parietal and visceral peritoneum

What does the visceral peritoneum cover

the organs

What is the parasympathetic innervation

vagus nerve, pelvic splanchnic nerves and inferior hypogastric plexus (S2 and S4)

What does the vagus nerve innervate

liver, bladder, cardiac plexus, stomach, pancreas, large intestine, and small intestine

What does S2 and S4 innervate

rectum, urinary bladder and ureters, and genitalia

Where does sympathetic innervation come from

thoracic and lumbar region

Nerves synapse at what for the digestive system, adrenal gland, and kidney

celiac ganglion

Where do nerves for the urinary and reproductive system synapse

inferior mesenteric ganglion

What is the lining of the GI system

mucosa or mucous membrane

submucosa

muscularis

serosa

What makes up the mucosa or mucous membrane

epithelium, lamina propria, and muscularis mucosa

What does the lamina propria contain

loose connective tissue, blood and lymphatic vessels, smooth muscle, lymphocytes, macrophages, and small glands

What is the muscularis mucosa

smooth muscle separating the mucosa from the submucosa

What makes up the submucosa

submucosal plexus of autonomic nerves (Meissner’s), glands, and lymphoid tissue

What is the muscularis

thick layer or sublayers of smooth muscle

internal sublayer of circular muscle

Connective tissue layer with blood and lymphatic vessels and a myenteric plexus

what is the myenteric plexus

plexus of intrinsic autonomic nerves aggregated into ganglia

What does the connective layer with the myenteric plexus do

supplies motor innervation to muscles

What is the muscularis the external sublayer of

longitudinal smooth muscle

What is the muscularis involved in

peristalsis or wave-like contractions; propels food

What is the serosa

thin layer of connective tissue, blood and lymphatic vessels, and adipose tissue

What covers the serosa

covered by mesothelium, simple squamous epithelium

visceral peritoneum

What is the epithelia of the esophagus

nonkeratinized stratified squamous epithelium

What do the esophageal glands do

submucosal, mucin and fluid secretion, and provide lubrication

What are rugae in the stomach

folds in mucosa and submucosa when stomach is empty

What are the layers of the stomach (mucosa)

epithelium, gastric pits, gastric glands, gastric gland cells

What is the epithelium or surface mucus cells, what does it do

deeply invaginated simple columnar epithelium

secrete thick, adherent and highly viscous mucous layer

What are the gastric pits

form from tubular invaginations of epithelium, each with an opening to the lumen of the stomach, lead to long branching tubular glands

What forms the gastric glands

simple branching of gastric pits

What are the gastric gland cells

mucous neck cells and parietal or oxyntic cells

What does the small intestine do

increase surface area for absorption

What are the 4 degrees of folding in small intestines

plicae circularis 3x

villi 10x

microvilli on enterocytes 20x

intestinal glands or crypts

What is found in the mucosa of the small intestine

plicae circulares and villi

What are plicae circulares

circular or semilunar folds of the mucosa; evaginations of mucosa and submucosa that project into lumen

What are the villi

short mucosal outgrowths on plicae circularis

What do villi contain

covered by simple columnar epithelium and goblet cells (long microvilli)

core of loose connective tissue from lamina propria

fenestrated capillaries and associated lymphatic vessels or lacteal

What are the cells of the mucosa

enterocytes and goblet cells

What are enterocytes

tall, simple columnar epithelium

striated or brush border of microvilli with a glycocalyx (absorption)

What do enterocytes do

discharge chylomicrons to be taken up by lacteals

What do goblet cells do

secrete mucin which is hydrated to mucus

What does the lamina propria in the mucosa of the small intestine do

penetrates core of each villi

What is the lacteal

lymphatic vessels in villi that absorb chylomicrons

What does the submucosa have

Duodenal glands (Brunner’s), alkaline mucus; neutralizes acidic chyme from stomach

What does the ileum have

GALT in the lamina propria and submucosa; Nodules in Preyer’s patches

What is the mucosa in the large intestine

flat with no plicae circularis or villi

What does the mucosa of the LI have

intestinal glands, simple columnar cells, enteroendocrine cells, epithelial stem cells, lamina propria, and mucosa muscularis

What makes the intestinal glands

short, straight simple tubular glands

What are the simple columnar cells

colonocytes, microvilli that are absorptive

What is the lamina propria of LI have

rich in lymphoid cells and nodules- GALT

What are hepatic lobules

hexagonal blocks of tissue

What forms hepatic lobules

hepatocytes that form hundreds of irregular anastomosing plates radiating toward a small central vein

What does each hepatic lobe have

3-6 portal areas each of which contains a portal triad and some lymphatic vessels and nerves

What forms the portal triad

venule of portal veins rich in nutrients with low O2 levels

arterioles of hepatic artery rich in O2

one-two small bile ductules of cuboidal epithelium

What are between the anastomosing plates of hepatic lobules

vascular sinusoids

What do sinusoids emerge from

peripheral branches of the portal vein and hepatic artery

What do sinusoids do

cover central vein

place where venous and arterial blood mix

What do sinusoids have

thin discontinuous lining of fenestrated endothelia surrounded by a sparse basal lamina and reticular fibers; allows plasma to fill perisinusoidal space

What is the space of Disse

Perisinusoidal; subendothelial space between hepatocytes and sinusoids

What fills the space of disse

plasma and bathes the irregular microvilli of hepatocytes; direct contact between plasma and the basal surface of hepatocytes

What occurs at the space of disse

site of exchange of material between blood and hepatocytes

What is the hepatic blood supply

hepatic artery and portal vein both flow into the central vein

What does the hepatic artery do

20-20%; carries well oxygenated blood from aorta

What does the portal vein do

70-80%; carries poorly oxygenated but nutrient rich blood form GI tract and spleen to the sinusoids of the liver

What is the flow of blood

blood always flows from the periphery to the center of each hepatic lobule

What faces the sinusoid

base of hepatocyte; secretes plasma proteins into sinusoid (endocrine function)

What is the flow of bile

opposite of blood from central to the portal triad region

What does the apex of hepatocyte form

the bile duct canaliculi into which it secretes bile (exocrine function)