Small intestine histology, large intestine Flashcards
What layers compose the small intestine?
Mucosa
Submucosa
Muscularis
Serosa
What composes the mucosa of the small intestine?
Simple columnar epithelium, lamina propria, muscularis mucosa; villi and microvilli
What composes the submucosa of the small intestine?
CT and vessels, nerves
Where are Brunner’s glands found?
Submucosa of the duodenum
What are the layers of the muscularis? How do they change?
2 layers inner circular and outer longitudinal
Inner circular is thicker, outer longitudinal becomes thinner
The jejunum and ileum have mesentery, so their outermost layer is a ______.
serosa
How is the small intestine innervated?
PNS- Vagus (X) nerve
SNS- Prevertebral ganglion
What kinds of motility are found in the small intestine?
How long is food there?
Peristalsis and segmentation
3-5 hours
Where are brush border enzymes found?
On plasma membrane of microvilli of columnar cells
What are the three easy brush border enzymes? And their substrates?
Lactase- Substrate: lactose (milk sugar)
Maltase- Substrate: Germinating cereal grains
Sucrase- Substrate: sucrose
Which brush border enzyme splits a dipeptide into 2 amino acids?
Dipeptidase
Which 2 brush border enzymes remove aa’s from the end of a chain?
Carboxypeptidase
Aminopeptidase
What activates trypsin, a pancreatic enzyme?
Enteropeptidase (enterokinase)
What is luminal digestion vs contact digestion?
Digestion takes place in the lumen and at the surface of microvilli
The large intestine is also known as the _____. How long is it? What does it mainly absorb?
colon
5 feet
water
What does the colon manufacture?
Certain vitamins
Feces
What is the opening between the large and small intestines? What is it’s usual position?
ileocecal sphincter
Normally partially closed
What is the cecum? What attaches to it?
2.5” long, a “blind pouch” appendix is attached here
Which two colons are retroperitoneal?
Ascending and descending
Which colon has mesentery? What is it called?
Transverse
Mesocolon
The ______ colon connects to the rectum
Sigmoid
What are the names for the places where the colon turns?
Turns left at the right colic (hepatic) flexure
Turns down at the left colic (splenic) flexure
How long is the anal canal?
1 inch
How many sphincters does the anal canal have? What kind of muscle controls them?
2: an internal sphincter (smooth muscle) and an external sphincter (skeletal muscle)
Describe the mucosa of the large intestine.
4 things.
No villi or circular folds
Simple columnar epithelium with many goblet cells
Long, straight intestinal crypts, that are the full thickness of the mucosa
Lymph nodules here (no capsule
Describe the submucosa of the large intestine.
CT and vessels
What are the three layers of the muscularis of the large intestine?
Tenia coli
Haustra
Epiploic appendages
What is the tenia coli? What does it form?
Longitudinal muscle in 3 bands
Thickened, and ribbon-like
Tonic contraction forms deep pockets
What are the “pockets” of colon?
Haustra
What are the epiploic appendages? What do they do?
Club-like patty pouches of peritoneum
Unknown function, come off tenia coli
What is haustral churning?
In large intestine food moves from pouch to pouch, 3-12 times/minute
How long does food spend in the colon?
3-10 hours
