The small intestine

Question 1

What are the three mian regions of the small instestine - length + function

Answer 1

Duodenum: 25cm
- retroperitoneal, nutrilize acidic chyme (bicarbonate), protect mucus (submucosal glands + goblet cells), digestion (bile + enzymes)
Jejunum: 2.5m, absorbtion and digestion
Ileum: 3.5m, absorbtion and digestion

Question 2

What is the role of the mesentary

Answer 2

Holds the intestine in place enabling movement without entanglement of the organ
contains veins nerves + lyphatics
veins remove deoxy nutriant rich blood to the heptic portal vein via the inferior and superior mesenteric veins
lymph lacteals remove fat nutriance to the cisterna chyli

Question 3

What is the function of the SI and how is this modified by the wall of the SI

Answer 3

The small intestine primarily functions to digest and absorbe nutriance
Requires a large surface area -
length, plicae circulares, villi and microvilli increase SA

Question 4

What is a plicae circulare

Answer 4

Perminenet fold of the small intestine
- Core of sub mucosa overlayed with mucosa

Question 5

What is a villi

Answer 5

Protrusion of the epithelium with a core os lamina propria
Contains lacteal + capilary network -> remove fats, carbohydrates + protein
movement controled by muscularis mucosae -> promote absorbtion

Question 6

What is a microvilli

Answer 6

Microvilli = brush boarder are protusions of plasma membrane of a cell increase surface area on enterocytes (absorbtion cells)
- contact digestion -> enzymes teathered by glycocalyx around the microvilli do final digestion before absorbtion

Question 7

What type of epithelial cells are located in the small intestine + location and funciton

Answer 7

Enterocytes - absorbtion, villi (most common)
endocrine cells - hormone release, villi
Paneth cells - antibacterial enzymes, intestinal crypt
stem cells - regenerate cells, intestineal crypt
gobet cells - mucus, villi

intestinal crypt (below/between the villi)

Question 8

How does nutriance enter the cell

Answer 8

passive diffusion -> lipid solubles via the plasma membrane
channels and transporters through plasma membrane
through tight junctions -> diffusion between cells

Question 9

How the control of matter leaving the small intestine regulated + the effects if this occurs at the wrong time

Answer 9

The ileocecal valve - leads to the cecum
to fast = insufficent digestion -> diarrhea
to slow = over digested -> constipation