Flashcards in GI - Gross Anatomy Deck (58):
4 layers of the gut
mucosa, submucosa, circular muscle, longtiudinal muscle
Where is pain initially felt for the gut tube?
Where does perfusion arise for the gut?
Describe the aortic branches
unpaired and emerge anteriorally from the gut tube
What are the three aortic branches?
celiac trunk, superior mesenteric, inferior mesenteric
Lateral boundary of the abdominal cavity?
iliacus, transversus abdominus
Superior boundary of the abdominal cavity?
Posterior boundary of the abdominal cavity?
vertebral column and associated muscles
Inferior boundary of the abdominal cavity?
What do you know about the peritoneal cavity?
(couldn't think of a good question!)
(1) Peritoneal cavity is wholly contained with the abdominal cavity. Occupies a smaller space
(2) Everything in the peritoneal cavity is by default in the abdominal cavity
(3) Organs within the abdominal cavity can be inside or outside the peritoneal cavity
What is the serosa?
loose connective tissue, beneath the muscularis, serous fluid and mesothelium (in that order)
Organs in the abdominal cavity can be: (three options)
intraperitoneal (within the peritoneal - stomach), retroperitoneal (behind the peritoneum - kidney), infraperitoneal (below the peritoneum - bladder)
What are the secondary retroperitoneal organs?
duodenum, pancreas, and colon
Where do secondary retroperitoneal organs drain?
Start intraperitoneal so drain via the portal system
Why aren't intraperitoneal organs bouncing around untethered?
Intraperitoneal organs are connected by mesentery to the parietal peritoneum
Function of mesentery?
serves as a conduit to deliver vessels and nerves to the suspended organs; also allows necessary movement but not complete freedom
Embryology of intraperitoneal organs?
Intraperitoneal organs form within an infolding of the peritoneal membrane. Form one continuous membrane of parietal peritoeum and mesentery
How do organs become secondary retroperitoneal organs?
Entire colon starts out with a mesentery (intraperitoneal). During development the ascending and descending portions get pressed against the parietal peritoneum - mesentery resorbed. These portions become secondarily retroperitoneal (now covered by the parietal peritoneum) while transverse and sigmoid colons remain intraperitoneal (covered by the visceral peritoneum)
Example in class given if intraperitoneal organs are non-fixed
Non-fixed cecum herniated through the epiploic foramen. Now residing posterior to the stomach. Whoops.
** Main point: seemingly inconsequential events during development can have serious effects if they don't take place **
Which part of the digestive tract is the exception to the rule that digestive 'tube' is comprised of 4 layers?
Stomach; has an additional oblique muscle layer
Functions of the digestive tract?
digestion and elimination
Is the digestive tract uniform?
Diameter and function of the tube changes tremedously as move from esophagus through the rectum
Does digestion occur in the esophagus?
What tissue type is the mucosa of the esophagus?
stratified squamous (resist abrasion from food bolus)
Two fun facts about the esophagus (one involves a hiatus, the other the vagus nerve)
(1) esophagus passes from the thorax to abdomen thru esophageal hiatus in diaphragm
(2) vagus nerve hitces a ride on the esophagus to cross the thorax into the abdomen
What are rugaes?
transient folds in the stomach
Purpose of rugaes?
allow the stomach to expand without damaging
Purpose of the pyloric sphincter?
guards entry into the intestine
Mucosa lining the lumen of the stomach?
100% mucus-secreting; mucosa invaginates in the form of gastric pits
Base of the gastric pits?
Base of the pits is continuous with the gastric glands
Opening of the gastric pits?
Continuous with mucosa
What do gastric glands do?
responsible for the secretion of acid and digestive enzymes
What does the gastric pit do?
protective function; mucus-secreting (prevents stomach from self digestion)
What is unique about the duodenum?
Duodenum assumes a C-shaped course with intraperitoneal and secondary retroperitoneal segments (marks the junction of foregut and midgut)
What are crypts?
invaginations of mucosa (I wasn't sure what this meant but basically villi project into the lumen, while crypts project away fro the lumen)
What are villi?
evaginations of mucosa
Epithelium of the small intestine?
enterocytes - simple columnar with microvilli (digestion/absorption), goblet cells (lubrication)
Function of the small intestine?
responsible for digestion and nutrient absorption
Purpose of villi and crypts?
increase the surface area of the small intestine
Are the jejunum and ileum secondary retroperitoneal?
No. The jejunum and ileum are 100% intraperitoneal
Distinguishing characteristic of the proximal duodenum?
submucosal glands deep to the villi and crypst (called brunner's glands); combat the acidity of chyme entering from the stomach
Distinguishing characteristic of the distal ileum?
prominent and numerous lymphoid nodules called peyer's patches
Goal of the large intestine?
absorb H2O and vitamins
Name for pouches of large intestine?
What causes haustra?
Taenia Coli (3 bands of longitudinal smooth muscle) which are shorter in length than the intestine
Distinguishing characteristics of the large intestine?
no villi; maybe goblet cells (increase as move distally)
Where do accessory organs come from?
All of the accessory glands are born as an outgrowth of the forming digestive tract
What does the proximal portion of accessory organs become?
What does the distal portion of accessory organs become?
How do ducts terminate their growth in the development of the pancreas?
The ducts terminate by generating a balloon-like appendage at their distal extent. These balloons are acini (round clusters of cells) that produce digestive enzymes of the salivary glands and pancreas
(the liver develops in a similar fashion but the terminal balloons are replaced with a cord-like arrangement of hepatocytes)
What do acini do?
Acini make digestive enzymes that are carried to the intestinal lumen via ducts
How do the Islet of Langerhan form?
Some acini lose their ductal connection. These cell clusters become the Islets of Langerhan and depend on the circulatory syste to disperse their products (insulin, glucagon)
Bile duct, portal veins, hepatic artery (encased in CT coat)
Caval system drains which structures?
primary retropeitoneal structures (originally retrioperitoneal)
Hepatic portal drains which structure?
intraperitoneal and secondary retroperitoneal (original intraperitoneal organs)
stopped at slide 45
also skipped liver formation
What are varices?
Varices are dilated blood vessels in the esophagus or stomach caused by portal hypertension. (superior - esophageal varices, inferior - anorectal varices, anterior - caput medusae)