Histology

Question 1

oral cavity, oropharynx and laryngopharynx

Answer 1

covered by stratified squamous epithelium which is keratinised

Question 2

nasal cavity and nasopharynx

Answer 2

covered by respiratory epithelium

Question 3

oral cavity/tongue anterior 2/3 vs posterior 1/3

Answer 3

anterior - stratified squamous epithelium (thin on ventral surface, thick and with papillae on the dorsal surface

posterior - covered by smooth stratified squamous epithelium which, except for the circumvallate papillae, lacks papillae but does have substantial lymphoid aggregates in the submucosa

Question 4

what are the 4 major layers to the GI tract from lumen out

Answer 4

1. mucosa (epithelium sits on basal lamina, lamina propria- loose connective tissue, muscularis mucosae - thin layer of smooth muscle)
2. submucosa: dense irregular connective tissue
3. muscularis externa (two thick layers of smooth muscle - inner circular, out longitudinal)
4. serosa or adventitia (outer layer of connective tissue - attaches to other organs or suspends GI tract)

Question 5

does the GI tract go from smooth muscle at top (proximal oesophagus) to skeletal at the bottom

Answer 5

NO

other way round

Question 6

histology of oesophagus

Answer 6

non-keratinised stratified squamous epithelium

Question 7

stomach histology

Answer 7

simple columnar epithelium inc chief cells, parietal cells and enteroendocrine cells

Question 8

what do parietal cells produce

Answer 8

HCl

Question 9

what do chief cells produce

Answer 9

enzyme granules in apical cytoplasm and secreting digestive enzymes into lumen

Question 10

how to does the histology of the stomach differ in the different sections

Answer 10

cardia - (just after LOS) - deep gastric pits that branch into loosely packed, tortuous glands
body - shallow gastric pits with long staight gastric glands
pylorus- deep gastric pits with branched, coiled gastric glands at a higher density than in the cardia

Question 11

what are the gaps in between the villus also referred to as?

Answer 11

crypts of lieberkuhn

Question 12

how long is the duodenum/jejeunum/ileum

Answer 12

D - 25 cm
J - 2m
I - 2.75m

Question 13

what is in the submucosa of the duodenum

Answer 13

brunners glands

Question 14

describe the jejunum histology

Answer 14

tallest villi, located on permanent circular folds of the mucosa and submucosa, the plicae circularis. lymphoid follicles infrequent

Question 15

ileum histology

Answer 15

shorter villi
aggregations of lymphoid follices called peyers patches found in the submucosa and often extending into the lamina propria

Question 16

the most numerous cells, they are tall columnar cells with a brush border and are the absorptive cell

Answer 16

enterocytes

Question 17

produce mucin to protect epithelium and lubricate passage of material

Answer 17

goblet cells

Question 18

found at the base of the crypts of Leiberkhun, they have defensive unction and have regulating bacterial flora - secrete lysozyme and defensins

Answer 18

paneth cells

Question 19

produce hormones that contribute to the control of secretion and motility (eg gastrin, chylecystokinin (CCK), vasoactive intestinal peptide (VIP))

Answer 19

neuroendocrine cells

Question 20

found at the base of the crypts of lieberkhun, divide to replenish epithelium

Answer 20

stem cells

Question 21

what are brunner’s glands stimulated by and what do they do

Answer 21

stimulated by the presence of chyme.

they produce a thin, alkaline mucous to neutralise the chyme

Question 22

what does bile enter the 2nd part of the duodenum via

Answer 22

ampulla of vater

Question 23

what cells are for the removal of salts and water

Answer 23

absorptive cells

Question 24

secretion of mucus to lubricate the colon

Answer 24

goblet cells

Question 25

what are the 3 muscular strips of longitudinal muscle on the large intestine called

Answer 25

teniae coli

Question 26

anal canal

Answer 26

keratinised stratified squamous epithelium of the surrounding skin

Question 27

where is the myenteric plexus found and what does it control

Answer 27

between the muscle layers of the muscularis externa | controls gut motility

Question 28

what controls the musclaris mucosae and helps regulate secretion in the epithelium

Answer 28

submucosal plexus

Question 29

what does the exocrine pancreas produce in the GI system and where does it enter via the pancreatic duct

Answer 29

produces about a litre of digestive juice containing proteases (to break down proteins) lipases (to break down lipids) nucleases (to breakdown DNA/RNA) amylase (to breakdown starch, etc, each day.) These enter the duodenum via the pancreatic duct

Question 30

what does the endocrine pancreas consist of?

Answer 30

small, scattered islands of tissue called islets of Langerhans, which produce a number of hormones including insulin and glucagon. Islets make up about 1%-2% of the pancreas

Question 31

what are the enzyme produced by the exocrine pancreas

Answer 31

inactive proenzymes

Question 32

what happens when the pancreatic secretion enters the duodenum

Answer 32

enteropeptidase converts the inactive proteolytic enzyme trypsinogen into the active form, typsin this begins a cascade that results in the activation of the other enzymes

Question 33

what are the islets of Langerhans

Answer 33

groups of pancreatic cells secreting insulin and glucagon

Question 34

why is the apical part of the pancreatic acinus often very eosinophilic

Answer 34

due to the presence of zymogen (pre-enzyme) granules

Question 35

why are the basal part of cells of the pancreatic acinus typically basophilic

Answer 35

due to extensive RER

Question 36

what is the gallbladder lined by

Answer 36

tall simple columnar epithelium backed by a lamina propria of loose connective tissue rich in blood vessels and lymphatic vessels a coat of smooth muscle and outer collagenous layer of adventitia (brush border)

Question 37

under what control does the gallbladder deliver bile to the duodenum

Answer 37

vagal and via release of the hormone cholecystokinin by endocrine cells of the duodenum when fatty food enters it