Small Intestine Structure and Function Flashcards Preview

07. Year 2: Alimentary System > Small Intestine Structure and Function > Flashcards

Flashcards in Small Intestine Structure and Function Deck (49)
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1

What is the length of the small intestine?

About 6m

2

What does the small intestine consist of?

Duodenum

Jejunum

Ileum

3

How long is the duodenum?

25cm long

4

What are some functions of the duodenum?

Gastric acid neutralisation

Digestion

Iron absorption

5

How long is the jejunum?

2.5m long (2/5 of total length)

6

What are some functions of the jejunum?

Nutrient absorption

7

What percentage of nutrient absorption occurs in the jejunum?

95%

8

How long is the ileum?

3.5m (3/5 total length)

9

What is the function of the ileum?

NaCl/H2O absorption

10

What is the absorptive surface of the small intestine enhanced by?

Folds, villi and microvilli

11

What are the circular folds of the small intestine called?

Plicae

12

What is the relative surface area increase of the small intestine due to plicae?

3

13

What is the relative surface area increase of the small intestine due to villi?

30

14

What is the relative surface area increase of the small intestine due to microvilli?

600

15

What is the classification of the epithelium in the small intestine?

Simple columnar

16

What does villus cells absorb?

NaCl

Monosaccharides

Amino acids

Peptides

Fats

Vitamins

Minerals

Water

17

What are the functions of crypt cells?

Secrete Cl and water

18

How much water does the small intestine secrete everyday?

1500ml

19

Where does the water that the small intestine secretes come from?

Epithelial cells lining the crypts of Lieberkuhn

20

How does the small intestine secrete water passively?

Osmotically as a consequence of secreting Cl into the lumen of the gut

21

Why is H2O secretion important for normal digestive processes?

Maintains luminal contents in liquid state

Promotes mixing of nutrients with digestive enzymes

Aids nutrient presentation to absorbing surface

Dilutes and washes away potentially injurious substances

22

What happens to H2O secreted by crypts?

Normally reabsorbed by villi

23

What are the 2 distinct kinds of movements that makes up intestinal motility?

Segmentation

Perstalsis

24

What is segmentation?

Contraction of the circular muscles in the digestive tract

25

What is perstalsis?

Contraction of the longitudinal muscles in the digestive tract

26

When is segmentation most common?

During a meal

27

What is the function of segmentation?

Alterations between contraction and relaxation of short intestinal segments moves chyme up and down into adjacent areas of relaxation

Provides thorough mixing of contents with digestive enzymes

Brings chyme into contact with absorbing surface

28

How long does each cycle of segmentation last?

A few seconds

29

Explain the mechanism of segmentation contractions?

1) Initiated by depolarisation generated by pacemaker cells in longitudinal muscle layer

2) Intestinal basic rhythm (BER) produces oscillations in membrane potential

3) Reaches threshold which generates an action potential

4) Causes contraction

30

What is BER?

Basic electrical rhythm