GI 9 - The Intestines Flashcards
Name the cells in the intestines which secrete antibacterial enzymes ie Lyzozymes + Defensins:
Paneth cells
Approx. how many microvilli are present on each enterocyte?
~ 3000 per cell
What is the approx. total surface area of the GI tract? How much of this is the small intestine?
~ 30 m^2
Small intestines = ~ 20 m^2
How does the small intestine have such massive surface area?
- Folds of Kerckring
- Villi + Crypts of Lieberkuhn
- Microvilli
Where are plicae circulares found?
Small intestine
What type of epithelial cells are found in the intestines?
Simple columnar epithelia
Name the 2 types of starch that we can digest, the enzymes required for digestion, and the products of digestion:
Amylose -> Glucose + Maltose via Amylase
Amylopectin -> alpha-dextrins via Isomaltase
Which monosaccharides are transported by SGLT1 into the enterocyte from the GI lumen?
Glucose
Galactose
Which monosaccharides are transported by GLUT5 into the enterocyte from the GI lumen?
Fructose
How do monosaccharides move across the basolateral membrane of the enterocyte?
GLUT2
Which transporters are present on the apical membrane of the enterocyte for carbohydrate absorption?
SGLT1
GLUT5
Which enzymes to break down carbohydrates are present on the brush-border?
- Maltase
- Isomaltase
- Amylase
- Lactase
- Sucrase
Which enzymes to break down proteins are present on the brush-border?
- Trypsin
- Chemotrypsin
- Elastase
- Carboxypeptidase A + B
Which transporters can move amino acids and peptides into the enterocyte, from the GI lumen?
Na+-AA symporter
PEPT1
What causes micelles to fall apart, allowing the absorption of fats into the enterocytes?
Acidic brush-border (formed by Na+/H+ exchanger)
What are the components of a chylomicron?
- Triacylglycerides
- Cholesterol
- Phospholipids
- ApoB-48 (protein)
Where are chylomicrons formed, and what is their function?
Enterocytes
Transport dietary lipid from intestines to Liver + Adipose cells
Which electrolyte must be present for the absorption of glucose, water and other electrolytes?
Na+ - forms concentration/osmotic gradient
What is the blood supply to the small intestines?
Superior mesenteric artery
What is the function of the proximal half of the large intestine?
Absorption of minerals + H2O
What is the function of the distal half of the large intestine?
Storage and mucous secretion
What is the blood supply of the ascending colon, and proximal transverse colon?
SMA:
- Ileocolic
- Right colic
- Middle colic
What is the blood supply to the distal transverse colon, and descending colon?
IMA:
- Left colic
- Sigmoid arteries
What structures are present at the Caecum?
- Ileocaecal valve
- Appendix
The superior rectal artery is the continuation of which artery?
IMA - becomes sup. rectal when passes into pelvis
What is the taenia coli?
3 narrow bands of longitudinal muscle running the length of the large intestine
- except in rectum, anal canal and appendix
At what point does the colon stimulate the urge to defecate?
When rectum ~ 25% full
Is the internal anal sphincter controlled by the parasympathetic or sympathetic nervous system?
Parasympathetic
