8. GI Tract

Question 1

Describe epithelium of mouth

Answer 1

Mucosal covering (stratified squamous non-keratinising) abruptly turns into skin (stratified squamous keratinised)

Question 2

Epithelial sits on.. in mouth

Answer 2

• Submucosa containing collagen
• Elastic fibres + skeletal muscles to change shape
• Many small blood vessels, glands and fluid to keep moist

Question 3

Describe tongue

Answer 3

Stratified squamous but only keratinised on dorsal side (abrasion).

Question 4

Tongue features

Answer 4

Many sero-mucous glands + lymph nodes. Skeletal muscle insert onto lower jaw /fibrous connective tissue.

Question 5

What are papillae?

Answer 5

Tall, pointed folds that cover anterior 2/3 of tongue. (Fewer mushroom shaped fungi form papillae on tip and lateral sides)
Dome shaped circumvallate papillae separate posterior 1/3 of tongue.

Question 6

3 salivary glands

Answer 6

Parotid = serous (round pink acini cells)
Submandibular = mixed
Sublingual = mucous (branched, oval, purple)

Question 7

Describe acini cell structure

Answer 7

Pyramidal cell with spherical nuclei lined by is pale cuboidal become stratified. Drains into ducts

Question 8

Describe mucous secreting cells

Answer 8

Pale staining, mucous granules and oval shaped nucleus squashed to base of cell

Question 9

Epiglottis epithelium

Answer 9

Posterior = respiratory
Anterior = stratified squamous

Question 10

4 layers of HI tract

Answer 10

Innermost mucosa = lining epithelium + connective tissue
Underlying submucosa = loose connective tissue + meisseners plexus
External muscle coat = 2 layers of smooth muscle + nerves
Sedona = simple squamous

Question 11

Oesophageal epithelium

Answer 11

Thin lamina proprietor and muscularis mucosa Lined by non-keratinised stratified squamous with sero-mucous glands.
Dismally becomes simple columnar and outer smooth muscle

Question 12

Describe stomach lining

Answer 12

Simple columnar punctuated by gastric pits
Muscularis proprietor has 3 layers and rugae

Question 13

Parietal vs chief cells

Answer 13

Parietal = close to gastric pits, globular, many mitochondria and stains dark
Chief = pyramidal with blue secretion granules

Question 14

Cardia + pylorus

Answer 14

Have shorter and more coiled gastric pits than body + fundus

Question 15

2 main cell types in small intestine

Answer 15

Enterocytes = many microvilli for absorption
(Goblet cells)
Panettone cells = bright pink-staining granules secrete lysosymes

Question 16

What are crypts of Lieberkuhn?

Answer 16

Stem cells replace villi enterocytes

Question 17

Duodenum

Answer 17

Few plicae ciruclaris
Few goblet cells
Brunner’s glands!! (Secret alkali to neutralise)
Interstitial cells of cajal
Leaf like villi

Question 18

Jejunum vs Ileum

Answer 18

J = long villi, plicae circularis, goblet cells
I = short plicae curcularis, more goblet cells, Peyers patches

Question 19

Appendix epithelium

Answer 19

Simple columnar, goblet cells, few crypts, no villi

Question 20

Colon and rectum

Answer 20

Many close crypts, abundant goblet cells and Brunners glands

Question 21

Anus

Answer 21

Stratified squamous becomes keratinised distally
Fat and plexus of veins = varicosities
Sphincters

Question 22

Stomach vs gut tube

Answer 22

Has an extra innermost oblique muscle layer