14. Anat, Phys, and Path of Small Intestine Part 2

Question 1

14.4 Once chylomicrons enter the lymphatic circulation, what ducts and veins do they travel through to enter the venous circulation?

Answer 1

They are transported upward through the thoracic duct and emptied into the venous circulation at the juncture of the jugular and subclavian veins

Question 2

14.4 After eating a fatty meal, a high concentration of emulsified fat can be found in blood. What do you call this state?

How long does it take for plasma to return to its normal concentration?

Answer 2

Lipemia

The plasma usually becomes clear within a few hours since chlyomicrons have a short half life (

Question 3

14.6 What are the five classes of lipoproteins?

Answer 3

1. Chlyomicrons
2. Very low density lipoproteins
3. Intermediate density lipoproteins
4. Low density lipoproteins
5. High density lipoproteins

Question 4

14.7 What two cells synthesize the five classes of lipoproteins?

Answer 4

Enterocytes of small intestine -> chlyomicrons

Liver hepatocytes -> VLDL, IDL, LDL, and HDL

Question 5

14.8 What composition of TGs and cholesterols/phospholipids do VLDL’s have?

Answer 5

High TGs / moderate cholesterol and phospholipids

Question 6

14.8 What composition of TGs and cholesterols/phospholipids do LDL’s have?

Answer 6

Low TGs / high cholesterol and phospholipids

Question 7

14.8 What composition of TGs and cholesterols/phospholipids do HDL’s have?

Answer 7

Low TGs, cholesterol, and phospholipids

Question 8

14.8 What phospholipids are monitored and used to screen for atherosclerosis, MI & stroke risk, and heart disease?

Answer 8

LDL-C and HDL-C

Question 9

14.8 What role do LDLs serve?

Answer 9

They transport cholesterol and other lipids from the liver to the peripheral tissue, making them available (via receptor mediated endocytosis) for membrane or steroid hormone synthesis

Question 10

14.8 What role do HDL’s serve?

Answer 10

They transport excess cholesterol from peripheral tissues to the liver, where it is broken down and becomes part of the bile

Question 11

14.9 H2O absorption in the small intestine is active or passive transport?

What transporter mechanisms stimulate lots of water absorption?

Answer 11

Passive

Na/glucose and Na/amino acid cotransporter mechanisms stimulate lots of water absorption

Question 12

14.9 By what process is K absorbed?

Answer 12

Most K is absorbed passively when luminal [K} rises because of water absorption (solvent drag)

Question 13

14. 10 Where does calcium absorption occur?

- What primarily regulates calcium absorption?

Answer 13

Calcium absorption occurs in the duodenum and jejunum

Primarily regulated by Vitamin D3 (1,25-dihydroxycholecalciferol), which stimulates synthesis of Ca-binding proteins called calbindins in enterocytes

Question 14

14. 11 Which water-soluble vitamin requires intrinsic factor for normal absorption?
    - Atrophy of the gastric mucosa can affect this how?

Answer 14

Vitamin B12 (cobalamin)

Atrophy can result in deficiency of IF and acid secretion causing vitamin B12 uptake deficiency

Question 15

14.11 Where do peristaltic contractions occur?

Answer 15

Esophagus, stomach, and small intestine

Question 16

14.11 How are peristalsis and segmentation regulated by the nervous and endocrine system?

Answer 16

Both controlled by the autonomic nervous system - sympathetic nerves generally inhibit and parasymphathetic nerves generally excite muscular activity