Microanatomy of Small intestine and pancreas

Question 1

State the main functions of the small intestine

Answer 1

• DIgestion, absoprtion, production of hormones

Question 2

The musocsa has many folds (at various “levels” of the muocsa - to aid on digestion and absorption by massively increasing surface area.

Large circular folds called ???????????, are seen at eye level, and are most numerous in the upper intestine.

The mucosal surface is made up of numerous finger-like projections called ????

Each of the ????? has thousands of ????? on the columnar eipthelium.

Answer 2

Plicae circulaes or valves of Kerkring - which are particularly numorous in the jejunum, but not in the duodenum or ileum. .

Villus - finger like projections

Vllli - which massively increase surface area

Question 3

Invaginations of epithelial cells can be seen flanking the vilus projections. What is their name

Answer 3

Crypts of Lieberkuhn

Question 4

In the mucosa of a villus, there are bundles of lymphatic and blood vessels. What is the lymphatic vessel called?

Answer 4

Lacteal

Question 5

What type of cells would you expect to see in the epithelium of the villus? State their functoin

Answer 5

• Entercoytes - tall columnar cells for absorption
• Goblet cells - produce mucin for lubrication of intestinal contents and also protect the epithelium
• Paneth cells are found in base of crypts and are distinguished by eosinophillic granules - have defensive role. Secrete lysozymes.
• Neuroendocrine cells produce locally acting hormones that regulate gastrointestinal motility
• Stem cellls found at base of crypts
• Intraepithelial lymphocyts -immune defense

Question 6

Give example of products you would expect neuronendroine duodenal cells to produce, and what their function is

Answer 6

• Cholecystokinin
  
  • stimulates the production and secretion of pancreatic enzymes
• Secretin
  
  • Stimulates production and secretion of bicarbonate in the pancreas

Question 7

Lamina propria of mucosa extends between the cripts and into the core of each illus, and contains a rich vascular and lymphatic network. What structure would you expect to find below the lamina propria?

Answer 7

Muscularis Mucosae

Question 8

The submucosa of the duodenum has a specical type of submucosal gland, What is this called, and what is it’s function?

Answer 8

Brunner’s gland - secretes bicarbonate to neutralise chyme

Question 9

Brunner’s glands are found mainly in the mainly submucosa. The duct of the gland passes through the muscularis mucosae to open into the ??????? between the mucosal villi.

Answer 9

Crypts

(B) is brunners gland

Question 10

Lamina propria of the ileum mucosa has specialised masses of lymphoid tissue. What are these called

Answer 10

Peyers patches

Question 11

Villi tend to be longest at the ???? and shorter at the ?????.

Lymphoid tissues are most prominent in the????

Plicae circulares are most prominent in the ?????? and proximal ?????, and generally absent from the duodenum and distal illeum.

Answer 11

• Duodenum, Illeum
• Ileum
• Jejunum and proximal illeum,

Question 13

Pancreatic structure consists of lobules. Lobules consists of many tini branches of the pancreatic duct, which end in special blind pockets called ??????. Each pancreatic acini is lined with a simple ???????? epithelium.

Answer 13

Pancreatic Acini

Cuboidal

Question 14

Pancreatic islets are scattered amongst pancreatic acini. The islets account for about 1% of all cells. State the subtypes of cells in the islets and what they do

Answer 14

Question 15

What cells produce bicarbonate in the pancreas?

Answer 15

Pancreatic duct cells

Question 16

State the pancreatic enzymes produced by the exocrine cells of the pancreatic acini

Answer 16

• Pancreatic alpha amylase
  
  • breaks down carbohdyrates
• Pancreatic lipase
• Nucleases - break down RNA and DNA
• proteolytic enzymes (secreted as inactivated zymogens)
  
  • Trypsinogen
  • Chymotrypsinogen
  • Carboxypeptidase
  • Proelastase
  • Kallikreinogen
  • Pro-Colipase
  • Pro-phospholipase

Question 17

What type of bonds does pancreatic amylase act on?

Answer 17

• Alpha 1,4 glycosidic bonds

Question 18

What are the main products of pancreatic amylase?

Answer 18

• The main one is Maltose
  
  • Maltriose is another - just 3 glucose together, so is a trisaccharide
  • Dextrins - basically seems to be anything between the number of glucose molecules in maltose and starch?
  • Can also be Lactose, frucotse or Sucrose

Question 19

Substances excreted by acinal cells and the ductal cells collectively are known as what?

Answer 19

Pancreatic juice.

Question 20

Secretion of trypsin inhibitor ensures proteolytic enzymes of the pancreatic juice do not become activated either inside the cells that produce them, or in the pancreatic acini or the ducts of the pancreas. If this did not occur, what could happen?

Answer 20

• Pancreas itself could be digested
  
  • can lead to pancreatitis

Question 21

When the pancreas becomes severely damaged or when a duct becomes blocked, large amounts of pancreatic secretion become pooled in damaged areas of the pancreas. Under these conditions, the effect of trypsin inhibitor, is often overwhelemd, in which case the pancreatic secretion soften become activated, and can literally digest the pancreas. Can give rise to pancreatitis.

Question 22

List the 3 major substances that initiate pancreatic secretion in response to chyme entering the duodenum.

Answer 22

• Ach from vagus nerve
• Secretin
• Cholecystokinin

Question 23

Aside from bicarbonate, what other important component of pancreatic juice is produced by the duct lining cells of the pancreas?

Answer 23

Water

Question 24

• Ach is released by mainly vagus nerve endings during the cephalic, gastric and intestinal phases of pancreatic secretion - stimulates the ????? of the pancreas, producing ????????
• Cholecystokinin - is secreted by ???????? and ?????? mucosa when food enters the small intestine. It also primarily stimulates the ????? cells of the pancreas, producing ???????
• Secretin - secreted by ??????? and ?? mucosa when food enters the small intestine. Unlike the other two, stimulates secretion of mainly ????? by the ductal epithelium. This is important for washing the enzymes into the duodenum.

Answer 24

• acinar cells, proteolytic enzymes
• duodenum and upper jejunum, acinar, protelytic enzymes
• duodenum and jejunum, water

Question 25

How much pancreatic juice is made per day?

Answer 25

1L

Question 26

When chyme enters the duodenum, what enzyme produced from the small intestine has a critical role in triggering trypsinogen activation?

Answer 26

Enteropeptidase