GI histology

Question 1

what are the layers of gut tube?

Answer 1

Mucosa
Epithelium
Lamina Propria
Muscularis mucosae

Submucosa

Muscularis externa
Inner circular
Outer longitudinal

Adventitia /Serosa

Question 2

what are characteristics of the layers in the oesophagus?

Answer 2

Stratified squamous non-keratinised epithelium

Submucosa shows mucous glands

Muscular layer – upper 1/3 skeletal, middle 1/3 – smooth+ skeletal, lower 1/3 - smooth

Question 3

what do parietal cells secrete?

Answer 3

HCL

Question 4

what do chief cells secrete?

Answer 4

pepsinogen

Question 5

what are characteristics of the layers in the small intestines

Answer 5

Villi

Crypts of Leiberkuhn

Lymphoid aggregations in mucosa - Peyer’s patches

Question 6

what are characteristics of the layers in ileum?

Answer 6

Villi +

Peyer’s patches

Question 7

what are characteristics of the layers in the large intestine?

Answer 7

Thick mucosa, crypts, mucous secreting cells. No villi.

Question 8

what are the glands in the GI?

Answer 8

Salivary glands (in head/neck block)
Pancreas
Liver (very elaborate gland!)

Question 9

what are Secretory (acinar component) – roundish structure with columnar cells and nuclei at the base

Answer 9

Ducts

Question 10

characteristics of the pancreas?

Answer 10

Islet of Langerhans – endocrine part – no acini

2 – exocrine part – pancreatic acini

3 – pancreatic duct ( for exocrine part)

Question 11

what are the regions of the stomach?

Answer 11

cardia
fundus
body
pylorus

Question 12

functions of the stomach

Answer 12

Food starts to be digested and absorbed in the stomach.
Food is broken down chemically, by gastric juice, and mechanically, by contraction of the three layers of smooth muscle in the muscular externa layer. The broken up food at the end of this process is called chyme.

Question 13

what are rugae?

Answer 13

folds found on the interior layer of the stomach and aid in breaking down food when the stomach contracts.

Question 14

what are gastric pits?

Answer 14

are indentations in the stomach epithelium which denote entrances to the tubular shaped gastric glands. The human stomach has several million of these pits which dot the surface of the lining epithelium

Question 15

what are the three types of gland?

Answer 15

cardiac – secrete mucus;
fundic – secrete HCl and intrinsic factor;
pyloric – secrete gastrin

Question 16

what are the gastric glands responsible for?

Answer 16

synthesis and secretion of the gastric juice.

Question 17

what is the lining epithelium of the stomach and gastric pits made up of?

Answer 17

mucus secreting simple columnar epithelium.

Question 18

where are parietal cells found?

Answer 18

concentrated in the isthmus region, but also found in the base and neck of the glands. These are large pale pink staining cells with a central spherical nucleus thus having a ‘fried egg’ appearance

Question 19

where are cheif cells found?

Answer 19

found in the bases of gastric glands. They have a stongly basophilic granular cytoplasm, as they have lots of rER for production of peptin, which is secreted (as precursor pepsinogen), and basally located nuclei.

Question 20

where are endocrine cells found?

Answer 20

cells in the bases of the glands secrete gastrin and other hormone

Question 21

function of mucous cells

Answer 21

Secrete mucus to protect epithelial cells

from enzymes & acid

Question 22

histological features of the small intestine

Answer 22

. It has large circular mucosal folds
called plicae circulares

2. Projecting from the plicae are
   smaller folds called villi, which
   are finger like mucosal projections,
   about 1mm long.
3. The lining columnar epithelial cells
   have fine projections on their apical
   surfaces called microvilli (“brush border”

Between the villi there are crypts, called crypts of Lieberkuhn/intestinal glands, which extend down to the muscularis mucosae. These crypts are short glands

5. The lamina propria which underlies the epithelium has a rich vascular and lymphatic network, which absorbs the digestive products.
   The lymphatic capillaries are called lacteals, and absorb lipids.

The vascular capillaries are fenestrated to aid absorption.

Question 23

what do crypts contain?

Answer 23

Paneth cells
Endocrine cells
Stem cells
Intraepithelial lymphocytes

Question 24

function of paneth cells

Answer 24

they have a defensive function, and stain intensely eosinophilic.
Secrete antimicrobial peptides.

Question 25

function of endocrine cells

Answer 25

which produce secretin, somatostatin, enteroglucagon and serotonin.

Question 26

function of stem cells

Answer 26

found at the base of the crypts, which divide continuously to replace enterocytes (every 2-3 days), goblet cells, paneth cells and neuroendocrine cells

Question 27

where are lymphoid aggregations commonly found?

Answer 27

found in the sub-mucosa of the small intestine, an you can see one here. The larger aggregations of lymphoid tissue are known as Peyer’s Patches.

Question 28

what does the muscularis externa contain?

Answer 28

contains two layers of smooth muscle, an inner circular and outer longitudinal, for continuous peristaltic activity of the small intestine

Question 29

comparisons between duodenum and small intestine?

Answer 29

The villi are broader

Peyer’s Patches are less common

One unique feature: Brunner’s glands, which are found in the sub-mucosa.

Question 30

comparison between jejunum and ileum

Answer 30

The villi of the jejunum are tall and cylindrical, while they are very short and cylindrical/non-existent in the ileum.

Crypts are more extensive in the mucosa of the jejunum, and contain Paneth cells.

Peyer’s Patches found in the submucosa of the ileum, but not the jejunum.

Question 31

function comparison of small intestine and large intestine

Answer 31

SI
principle site for digestion of food and absorption of the products of digestion

LI
reabsorption of water and elimination of undigested and waste