Lecture 22: THE SMALL INTESTINE

Question 1

What are the regions of the small intestine (in order)?

Answer 1

Duodenum, jejunum and ileum

Question 2

What is the largest region of the small intestine?

Answer 2

Ileum

Question 3

What is the total length of the small intestine?

Answer 3

About 6m

Question 4

Where is the initial segment of the small intestine?

Answer 4

Retroperitoneal

Question 5

What is the small intestine held in place by?

Answer 5

Mesentery

Question 6

What does the mesentery allow?

Answer 6

Movement, but prevents the small intestine from getting tangled

Question 7

What does the mesentery contain?

Answer 7

Arteries, veins, nerves and lymphatics

Question 8

What is delivered to the small intestine?

Answer 8

Chyme which is acidic

Question 9

What is needed because of chyme being acidic?

Answer 9

Protect the epithelium and neutralise pH

Question 10

How is the epithelium protected?

Answer 10

By mucous secreting cells and glands in the submucosa (specifically in the duodenum)

Question 11

How is pH neutralised?

Answer 11

By bicarbonate (HCO3-) from the pancreas

Question 12

What are plicae circulares?

Answer 12

Permanent folds of the small intestined

Question 13

What is the structure of plicae circulares?

Answer 13

Core of submucosa with overlying mucosa

Question 14

Where are villi found?

Answer 14

On the surface of the plicae circulares

Question 15

What does the muscularis mucosae allow?

Answer 15

Villi to wiggle back and forth

Question 16

What are villi?

Answer 16

Folds of the mucosa

Question 17

What is the core of each villus?

Answer 17

FCT (lamina propria)

Question 18

What do villi contain?

Answer 18

Vessels

Question 19

What vessels do villi contain?

Answer 19

Lymph lacteal and capillary network

Question 20

What is drained into the lymph lacteal?

Answer 20

Products of fat digestion

Question 21

What is drained into the capillary network?

Answer 21

Products of protein and carbohydrate digestion

Question 22

What enters the mesenteric veins?

Answer 22

Nutrient rich, deoxygenated blood absorbed in the small intestine

Question 23

What do mesenteric veins drain into?

Answer 23

Hepatic (liver) portal vein

Question 24

What do lymph lacteals drain into?

Answer 24

The cisterna chyli, thoracic duct and then left subclavian vein

Question 25

What is the epithelium of the small intestine?

Answer 25

Simple columnar

Question 26

What is on the apical surface of the small intestine cells?

Answer 26

Microvilli to increase the surface area further

Question 27

What do microvilli form?

Answer 27

A brush border

Question 28

What is glycocalyx?

Answer 28

A network of glycoproteins and branched filaments

Question 29

What does the glycocalyx do?

Answer 29

Tether enzymes

Question 30

What does contact digestion involve?

Answer 30

Enzymes attached to the brush border

Question 31

What is the plasma membrane?

Answer 31

A barrier which is selectively permeable (lipid soluble things can travel through it)

Question 32

What does the plasma membrane have?

Answer 32

Proteins (channels and transporters)

Question 33

How are tight junctions described?

Answer 33

Very tight

Question 34

What junctions are between small intestine epithelial cells?

Answer 34

Tight junctions

Question 35

What may diffuse through tight junctions?

Answer 35

Small molecules (down a concentration gradient)

Question 36

What are the cells of the small intestine epithelium?

Answer 36

Enterocytes, goblet, stem, paneth and endocrine

Question 37

What are enterocytes?

Answer 37

Absorptive cells which have a microvilli brush border

Question 38

What do goblet cells do?

Answer 38

Secrete mucous for protection

Question 39

What do stem cells do?

Answer 39

Make all cell types

Question 40

What do paneth cells secrete?

Answer 40

Granules and antibacterial enzymes

Question 41

What do endocrine cells do?

Answer 41

Secrete hormones

Question 42

What is found in an intestinal crypt?

Answer 42

Paneth cells at the base, stem cells above and epithelial cells further above