GI 2 continued

Question 1

What is the mucosa of small intestines?

Answer 1

• involved in digestion and absorption of food.

- Lined by simple columnar epthelium for absorptive function.

Question 2

How is the surface area increased in the small intestine?

Answer 2

The pilicae circularis increase surface area by increasing transverse folds of the mucosa.

• TThe lamina propria and its underlying epithelium create flattened productions into the lumen known as villi.
• The surface of the absorptive cells contains many microvilli for absorption of food stuff

Question 3

What are crypts of lieberkuhn?

Answer 3

Intestinal glands and theyre located in the mucosa

Question 4

What cell types are found in the epithelium of the small intestines?

Answer 4

• Absorptive cells.

- Goblet cells

Question 5

What are absorptive cells?

Answer 5

The predominant cells in the epithelium.

• Simple columnar with distinct pattern or polerization
• Nucleus is always basal and apical surface is covered by aproximatly 3000 microvilli.

Question 6

What compromises striate or brush border?

Answer 6

The microvilli in absorptive cells

Question 7

What covers the striate (brush) border?

Answer 7

Glycocalyx which encloses disaccharidases and dipeptidases which are important digestive enzymes.

Question 8

What are lacteals?

Answer 8

lipid catabolisim products that are generated from absorptive sells then passed to lymphatics.

Question 9

What are goblet cells?

Answer 9

Interspersed between absorptive cells. They gradually increase in number from the duodenum to the ileum. they secrete protective mucus high in proteoglycans onto the surface epithelium

Question 10

What are the cell types in intestinal glands?

Answer 10

1. Enteroendocrine cells
2. Paneth cells
3. M Cells
4. Undefferentiated cells.

Question 11

describe enteroendocrine cells in small intestine?

Answer 11

Interesperesed between absorptive and goblet cells. They secrete many products including:
-Secretin, cholecystokinin, gastic inhibiroty peptide and motlin into the lamina propria

Question 12

Describe paneth cells in S.I

Answer 12

Found in the bas of each intestinal gland in SI. Known to secrete lyzozyme which plays a role in controlling intestinal bacteria

Question 13

describe the roll of M cells

Answer 13

M stands for membranous epithelial cells which are flattened and located over lymphoid nodules in the mucosa and lamina propria. Their apical surface have small folds instead of microvillus. Endocytose antigens from lumen then pass them to lymphoid cels in the underlying nodule to initiate immune response.

Question 14

Describe Undefferentiated cells in the SI

Answer 14

The lower 1/3 to 1/2 of intestinal glands undergo continual mitosis. Differentiate into all cell types in the epithelium, New paneth cells move to the base but other cells move to the tip of glands. Oldest cells are found on the tips of microvilli except for paneth cells. Entire epithelium renews every 3-7 days

Question 15

Describe the lamina propria of SI

Answer 15

Lacteals (Lymph vessels) are present as well as prominent muscularis mucosae. many lymphoid nodules are projecting from mucosa and lamina propria.

Question 16

What are prevalent lymphoid nodules found in SI?

Answer 16

Peyer’s patches

Question 17

Describe the submucosa of SI

Answer 17

Brunner’s glands is another name for SI submucosal glands. In duodenum they produce alkaline mucus to offset the acidity of the food entering from the pylorus.

Question 18

Describe the muscularis externa of SI

Answer 18

inner circular and outer longtitudinal muscle layers.

Question 19

Describe the serosa of SI

Answer 19

Visceral peritoneum covering small intestines; consists of connective tissue with a single layer of simple squamous epithelium.

Question 20

What is the major function of the mucosa of Large intestine?

Answer 20

Water absorption electrolytes and adding mucus to undigested material from SI.

Question 21

How does water absorption occurs in large intestines?

Answer 21

Passively across the apical surface of simple columnar cells due to the gradient produced by active transport of sodium ions into the extracellular space.

Question 22

Are you able to see villi in large intestines as well as brush border on the surface of columnar absorptive cells?

Answer 22

Nah

Question 23

Describe the mucosa of L.I

Answer 23

• two cell types dominate; goblet and simple columnar cells.
• Lamina propria and lymphoid nodules are present.

Question 24

Describe the submucosa of L.I

Answer 24

-Composed of blood vesseles, nerves and lymphatics

Question 25

describe serosa of L.I

Answer 25

The large intestine covered by visceral peritoneum or serosa

Question 26

What are the gut associated lymphoid tissues (GALT)

Answer 26

1. 1/4 of mucosa consists of lymphoid tissue in form of lymphoid nodules, lymphocyes, macrophages, eosinophiles and plasma cells in lamina propria
2. The M cells overlying peyer’s patches and other lymphoid nodules also transport antigens from the lument to surrounding lamina propria. This can simulates lymphocytes and plasma cells activity.