Week 7 & 8: Histology of Lower Digestive system

Question 1

Common featues of GIT - inside to outside

Answer 1

Mucosa, submucosa, Muscularis externa, serosa or adventitia

Question 2

What dos mucosa of GIT have?

Answer 2

Epithelium, LP, muscularis mucosae

Question 3

What does submucosa of GIT have?

Answer 3

connective tissue
+/- glands, lymph nodules
large vessels
nerve plexi

Question 4

Muscularis externa of Oesophagus

Answer 4

Striated in upper 1/3, striated and smooth in middle 1/3, Smooth in lower 1/3

Question 5

Gastro-oesophageal junction

Answer 5

Stratified squamous epithelium – simple columnar epithelium

Question 6

Stomach distinguishing histological features

Answer 6

1. simple columnar epithelium creating gastric pits.
2. Gastric glands
3. three layers of smooth muscle in muscularis externa
4. Rugae

Question 7

Where is Meissner’s nerve plexus?

Answer 7

Submucosa of Stomach

Question 8

Where us myenteric /auerbachs plexus?

Answer 8

Muscularis excterna of stomach - inbetween alyers

Question 9

Enteroendocrine cells

Answer 9

Hormone secreting, Gastrin .. Small cells, +- short microvilli

Question 10

Mucous cells (stomache)

Answer 10

Between epithelial cells, most abundant in NECK - nucelus at base fof cell, apical fuilled with mucus

Question 11

Parietal cells

Answer 11

secrete HCl and intrinsic factor (help absorb VB12), LArge cells, trianglualr, Bright pink with H+E, lots microvilli ++ mitochondria

Question 12

Chief cells

Answer 12

Deep in gland - base. SEcrete (pepsinogen) rER , zymogen granules.

Question 13

Small intestine - modifcations to increase surface area

Answer 13

1. Plicase circularis, ridge of submucosa & mucosa. Seen in longitudinal sections, greatest number in duodenum. 2. Villi - projections of mucosa. 3. Striated (brush) border - microvilli on apical surface

Question 14

Small intestine distinguishing features

Answer 14

1. plicae circularis & villi. 2. Paneth cells (antibacterial & phagocytic). 3. Brunner’s glands in submucosa of duo. 4. Peyer’s patches in ilium

Question 15

Epithelium of Small int

Answer 15

Enterocytes + goblet cells ( on basemement membrane). Paneth, enteroendocrine

Question 16

Paneth cells

Answer 16

Secrete lysosome. Located at base or krptt>

Question 17

What secretions are brunners g;ands

Answer 17

Mucus-serous

Question 18

Colon mucosa

Answer 18

• NO villi
• Numerous simple tubular glands = crypts of Lieberkuhn
which extend thru full thickness of the mucosa
• Stem cells in bottom of crypts divide to produce all epithelial cells

Question 19

Colon epithelium

Answer 19

Enterocytes – simple columnar epithelial cells
• Goblet cells abundant, 4:1 in colon to 1:1 in rectum
and secreting mucus continuously
• Enteroendocrine cells
• Intraepithelial lymphocytes common

Question 20

Anal canal distinguishing histological geatures

Answer 20

Upper region.
Simple columnar epithelium
Numerous glands & goblet cells.

Lower region.
Stratified squamous epithelium
Numerous glands..

Anal columns
Vertical folds of mucosa & submucosa
Allow stretch
Contain rectal arteries & veins

Question 21

What is at the centre of a liver lobule?

Answer 21

Central vein

Question 22

What lies at the periphery of liver lobules?

Answer 22

Portal triads

Question 23

Where are kupffer cells?

Answer 23

Phagocytes - rest on apical curface of enothelial cells in sinusoid lumen,. Liver

Question 24

Blood entering liver?

Answer 24

75% portal vein. 25% Hepatic artery. mixess in hepatic sinusoids

Question 25

Liver functions

Answer 25

``` Degradation and conjugation of toxins so they can be released from the body • Storage and/or metabolism of nutrients received from the GIT • Vitamin storage, activation, usage • Hormone activation • Production of blood proteins • Production of bile ```

Question 26

Liver detoxification - alcohol

Answer 26

In hepatocyte peroxisomes: Alcohol - metabolised to acetaldehyde then acetate. Excess can cause fatty liver.

Question 27

Where is Vitamin a stored?

Answer 27

Hepatic stellate cells

Question 28

What hormone doesliver activate?

Answer 28

Thyroxine

Question 29

What is located in Space of Disse

Answer 29

Hepatocyte microvilli project. | • Stellate cells

Question 30

Stellate cells

Answer 30

Store vit A. Actiated in Liver diseases to secrete collafen = fibrotic cirrhosis. locaed in Space of Disse

Question 31

Gallbladder function

Answer 31

Stores, concetrates & adds mucus to BILE. 2. Bile released in response to fatty foods in duodenum

Question 32

What happens when u eat dietary fast

Answer 32

Cholecystokini hormone relesead by enterocytes in duo. SM contraction in gallbladder - bile discharged in duo.

Question 33

Gallbladder epithelium

Answer 33

Cholangeocytes = simple columnr

Question 34

Gallbladder features

Answer 34

- No muscularis mucosae or submucosa. - Rokitansky-Aschoff sinuses.

Question 35

Exocrine pancreas

Answer 35

Acini - Secretions conotain over 20 digestive enzymes (inactive) = zymogens. Pancreatic ducts add bicarbonate ions. Enteroeptidases released from duodenal mucoas - activates them

Question 36

Acini (pancreas)

Answer 36

Secretory cells - triangular, basal nucleus, eosinophillic granules. Centroacinar cells - pale nucleus & cytoplasm

Question 37

Islets of langerhans

Answer 37

alpha = glucagon and delta (somatostatin) (purple) . Beta cells (insulin) - yelow