5.7.1. Overview of the Small Intestines - Structure and Function

Question 1

What are the 3 parts of the Small Intestines?

Answer 1

1. The Duodenum
2. The Jejunum
3. The Ileum

Question 2

What is the rough total length of the Small Intestines?

Answer 2

About 6 meters

dependent on the Size and Sex of the Person

Question 3

What is the rough length of the Duodenum?

Answer 3

About 25cm

Question 4

What is the rough length of the Jejunum?

Answer 4

About 2.5 meters (2/5 of the Small Intestines)

Question 5

What is the rough length of the Ileum?

Answer 5

About 3.5 meters (3/5 of the Small Intestines)

Question 6

What is the Function of the Duodenum?

Answer 6

1. Gastric Acid Neutralization
2. Digestion
3. Iron Absorption

Question 7

What is the Function of the Jejunum?

Answer 7

Nutrient Absorption - About 95% of Nutrients are absorbed here

Question 8

What is the Function of the Ileum?

Answer 8

1. NaCl and Water Re-absorption for Chyme Dehydration
2. Absorption of the Vitamin B12-Intrinsic Factor Complex
3. Absorption of Bile Salts for Enterohepatic Circulation (Recycling)

Question 9

What is the Absorptive Surface of the Small Intestines increased by?

Answer 9

1. Circular Folds (3 x area increase)
2. Villi (30 x area increase)
3. Microvilli (600 x area increase)

Question 10

Where does the Absorption of nutrients in the small intestine surface take place?

Answer 10

At the Villi

Question 11

What is Absrobed at the Villi?

Answer 11

1. NaCl
2. Monosaccharides
3. Amino-Acids
4. Peptides
5. Fats
6. Vitamins
7. Minerals
8. Water

Question 12

What is the Transporter protein that is found in the epithelial cell which absorbs Nutrients across the Lumen of the Jejunum?

Answer 12

The Sodium Coupled Secondary Active Transport Protein

Question 13

What is absorbed via a Sodium Coupled Secondary Active Transport Protein?

in other words what is COUPLEd with the sodium-coupled secondary active transport protein? We know Na, what is the other thing….

Answer 13

1. Sodium Ions
2. Monosaccharides
3. Amino-Acids
4. Nucleosides

Question 14

What transports Sodium Ions out of the Jejunum into the Blood?

Answer 14

The NaKATPase Transport Protein

Question 15

What, other than transporting Sodium Ions out of the Jejunal Cells into the Blood, does the NaKATPase Transport Protein do?

Answer 15

Transports Potassium Ions from the Capillary Lumen into the Jejunal Cell

Question 16

What allows Potassium to leave the Jejunal Cell, back into the Capillary Lumen?

Answer 16

Leaky Potassium Channels

Question 17

What transports everything other than Sodium from the Jejunal Cell into the Capillary?

Answer 17

A Transport Protein

Question 18

How is water secreted into the Alimentary Lumen?

Answer 18

Passively

Question 19

How does the Passive secretion of water into the Alimentary Lumen occur?

Answer 19

The Active Secretion of Chloride Ions out of the Epithelial Cells at the Crypts of Lieberkuhn.

Question 20

What area does the Active Chloride Ion secretion occur in?

Answer 20

The Crypts of Leiberkuhn

Question 21

What is important about the secretion of water into the Lumen from the Crypts of Leiberkuhn?

Answer 21

1. It maintains the Luminal Contents in a Liquid State
2. It promotes the Mixing of Nutrients with Digestive Enzymes
3. It Aids with Nutrient Presentation to the Absorbing Surface
4. It Dilutes and Washes away potentially injurious substances

Question 22

Where is the Water, secreted by the Crypts of Leiberkuhn, reabsorbed?

Answer 22

The Adjacent Villi