4A: Anatomy, Physiology and Path of the Small Intestine

Question 1

Describe the small intestine

Answer 1

• Constitutes the first 10-12 inches
• Begins at the pyloric valve, arcs around the pancreas and passes to the left, and ends at a sharp bend called the DUODENOJEJUNAL FLEXURE (JUNCTION)

Question 2

Where does the duodenum receive what?

Answer 2

he stomach contents, pancreatic juice and bile

Question 3

What happens in the duodenum?

Answer 3

Stomach acid is neutralized, fats are broken up by bile acids, pepsin is inactivated by the elevated pH and pancreatic enzymes take over the job chemical digestion.

Question 4

Describe the jejunum

Answer 4

-8 feet long and extends from the duodenum to the ileum

Question 5

Describe the ileum

Answer 5

About 12 feet in length and joins the large intestine at the ileocecal valve.

Question 6

What needs to happen in order for absorption of nutrients, electrolytes, and water in the small intestine to occur?

Answer 6

There needs to be a maximal surface area which is accomplished thru PLICAE CIRCULARES, VILLI, and MICROVILLI

Question 7

What does the surface absorptive cell contain?

Answer 7

A layer of closely packed microvilli, enzymes (brush border) and transporters

Question 8

What is a GOBLET CELL?

Answer 8

Mucous producers

Question 9

What is a Eneteroendocrine cell?

Answer 9

Secretes CCK, secretin, GIP (DNES cells; APUD cells..ugh)

Question 10

What do regenerative cells do?

Answer 10

Divide to replace themselves and other types of epithelial cells

Question 11

What do Paneth cells secrete?

Answer 11

Secrete the antibacterial enzymes lysozyme and other antibacterial agents

Question 12

What are some enzymes of disaccharides?

Answer 12

sucrose, lactose, and maltose

Question 13

What is sucrose made up of?

Answer 13

glucose and fructose

Question 14

What is lactose made up of?

Answer 14

Galactose and glucose

Question 15

What is maltose made up of?

Answer 15

glucose and glucose

Question 16

What are the MOST common examples of polysaccharides?

Answer 16

1) Glycogen 2) starch 3) cellulose

Question 17

What does Pancreatic amylase do?

Answer 17

degrades polysaccharides into disaccharides & oligosaccharides

Question 18

What are disaccharides degraded by?

Answer 18

A group of brush border enzymes called disaccharidases

Question 19

What breaks down starch and glycogen?

Answer 19

Salivary amylase

Question 20

Partially converted starch (and partially digested glycogen) is converted to Lactose, alpha-dextrins, maltotriose, maltose, and sucrose by what?

Answer 20

Pancreatic amylase

Question 21

What are the products of lactose digestion

Answer 21

Glucose and Galactose

Question 22

What is the product of alpha-dextrins digestion?

Answer 22

Glucose

Question 23

What is the product of Maltotriose?

Answer 23

Glucose

Question 24

What is the product of Maltose?

Answer 24

Glucose

Question 25

What is the product of Sucrose?

Answer 25

Glucose and Fructose

Question 26

Glucose and galactose are absorbed by what mechanism?

Answer 26

Via secondary active transport through a Na+ dependent cotransporter known as SGLT1

Question 27

What facilitates absorption of Glucose and Galactose against their gradients?

Answer 27

A high luminal concentration of Na+

Question 28

Fructose enters the brush border by facilitated diffusion via what?

Answer 28

Glucose transporter 5 (GLUT 5) that does not require Na+

Question 29

All monosaccharides are transported out of the enterocytes and into the capillaries by __________________
Also by what kind of diffusion ?

Answer 29

GLUT 2

**Facilitated diffusion

Question 30

What is the difference between normal lactose digestion and lactose intolerance?

Answer 30

• With normal digestion Lactase breaks down lactose and normal stool is produced.
• With lactose intolerance Bacteria ferment lactose and produce gases, organic acids, other osmotically active molecules

Question 31

The stomach does a good job denaturing proteins but is not effective at what?

Answer 31

Cleaving off individual amino acids (PEPSIN does some of this)

Question 32

Cleaving off amino acids occurs mainly at the ?

Answer 32

Brush border with amino peptidases and with the active pancreatic enzymes (proteases)

Question 33

Once the digestion of proteins is complete, most amino acids or small peptides are transported via the same co-transport mechanism utilized by?

Answer 33

Glucose

Question 34

Some amino acids do not require this sodium co-transport mechanism but instead are transported by?

Answer 34

The same way that fructose is moved, i.e by facilitated diffusion