Changing Function Through The GI Tract

Question 1

Phases of the GI tract

Answer 1

Ingestion
Fragmentation
Digestion
Absorption
Elimination

Question 2

Basic layout and organisation of the GI tract

Answer 2

Hollow tube with regional, histological, functional differences

Mucosa
Submucosa
Muscularis propria (externa)
Adventitious/Serosa

Question 3

Describe the mucosal layers

Answer 3

Specialised surface epithelium
On basal lamina

Lamina propria
-Loose connective tissue w blood and lymph vessels, nerve fibres and smooth muscle

Muscularis mucosae

• Thin double layer of smooth muscle
• Separates mucosa from submucosa

Question 4

Describe the epithelium of the mucosa throughout the GI tract

Answer 4

Protective, squamous stratified
Secretory, columnar simple
Absorptive, brush border, columnar simple
Protective at the end

Question 5

Describe the submucosa

Answer 5

Consists of loose connective tissue w

• Blood vessels
• Submucosal/Meissners plexus
• Leukocytes
• Varying amounts of adipocytes

Question 6

Smooth muscle function

Muscularis mucosa

Answer 6

Local control of mucosa, to accommodate changes in the lumen contents
Gentle movements of mucosa to help expel contents of glands and agitation of luminal content

Question 7

Smooth muscle function

Muscularis externa

Answer 7

Peristalsis along and out of GI tract

Inner circular layer, outer longitudinal layer

Question 8

Smooth muscle function

Adventitia/serosa

Answer 8

Thin connective tissue layer continuous w surrounding organs

Serosa if more mobile
Bound by mesothelium (simple squamous)

Question 9

Describe the epithelium found at the oesophagus

Answer 9

Stratified squamous
Physical protection, subject to mechanical abrasion
Kept moist by glandular secretions

Question 10

Describe the function and the structure of the stomach

Answer 10

Mechanical, biological, chemical breakdown

3 muscularis externa layers, inner oblique, circular, longitudinal

Pepsin, HCl initiates biological/chemical breakdown
Simple columnar epithelial layer of mucous secreting cells

Invagination form gastric pits

Question 11

Describe the structure of the gastric pits

Answer 11

Simple tubular glands
Insthmus, parietal cells
Neck, mucous cells, stem cells, parietal cells
Base, peptic, parietal, mucous, neuroendocrine cells found here

Question 12

Secretions from the gastric pits and glands

Answer 12

Mucous
Pepsin
HCl
IF
Gastric

Question 13

Function of stomach cells

Surface mucous cells

Answer 13

Mucous and HCO3-

-Protection from acidic, enzymatic properties of gastric juices and ingested foods

Question 14

Function of stomach cells

Mucous neck cells

Answer 14

Line upper parts of gastric pits and secrete mucous

Question 15

Function of the stomach cells

Stem cell

Answer 15

Divide every 3 days to regenerate cells

Question 16

Function of the stomach cells

Chief cells/peptic/zymogenic cells

Answer 16

Lower regions of gastric glands
Release zymogen granules
Acidic environment activates pepsin

Question 17

Function of the stomach cells

Parietal

Answer 17

Secrete HCl, IF

Has a central nucleus

Question 18

Composition of the stomach mucosa in the pylorus

Answer 18

Deep pits, branching, filed
Mucous secreting
Gastrin secreting

Question 19

Composition of the mucosa in the cardiac region of the stomach

Answer 19

Mainly mucous producing

Sparse

Question 20

Composition of the mucosa in the body of the stomach

Answer 20

Gastric juices (acid+enzymes)
Densely packed

Question 21

Small intestine mucosa adaptations to increase SA for absorption

Answer 21

Site of terminal food digestion
Plicae cirularis, covered in villi
Epithelium, simple columnar w brush border
Lacteals take away chylomicrons

T and B cells in connective tissue, IgA secretion

Question 22

Describe the structure of microvilli

Answer 22

Shape maintained by actin filaments, anchored to cell membrane via IF
Glycocalyx, glycoprotein, glycolipid projects from plasma membrane, protects from auto digestion

Question 23

Types of epithelial cells found in the small intestine

Answer 23

Enter oysters
Goblet, mucous secreting
Paneth, release digestive enzymes, immunoglobulins, lysozomes
Endocrine, hormone secretion
Stem cells

Question 24

Characteristic features of the duodenum

Answer 24

Characterised by submucosal mucus secreting Bruner glands

Question 25

Characteristic features of the jejunum

Answer 25

Tallest villi, no Brunner glands, few lymphoid follicles

Question 26

Characteristic features of the ileum

Answer 26

Aggregation of Peyer’s patches

Question 27

Describe the mucosa found at the appendix

Answer 27

Mucosa heavily infiltrated with lymphocytes

Large colony of gut bacteria, restore gut flora

Question 28

Describe the mucosa found at the colon

Answer 28

No villi
Columnar with microvilli and goblet cells
Goblet cells in mucosa
Outer longitudinal layer in 3 teniae coli

Question 29

Describe the epithelium and the mucosa found at the anorectal junction

Answer 29

Sudden transition from simple columnar to stratified squamous
Branched, tubular anal glands, mucus secreting onto anal surface

Internal anal sphincter, smooth muscle
External anal sphincter, skeletal muscle

Question 30

Describe the structure of the anal canal

Answer 30

Inner circular muscle thickens into the internal anal sphincter
Apocrine circumanal glands open onto skin around orifice