Microanatomy of GIT

Question 1

What is the Gastrointestinal tract responsible for?

( hint: 2 reasons )

Answer 1

1- The mechanical and chemical breakdown of food
2- absorption of nutrients

Question 2

How long is the GI tract ?

Answer 2

9m

Question 3

What are the 6 parts of the GI tract?

Answer 3

1- Oral cavity
2- Pharynx
3- Oesophagus
4- Stomach
5- Small intestine
6- Large intestine

Question 4

What are the 4 layers of the Gut wall? ( inside to outside )

Answer 4

1- Mucosa
2- Submucosa
3- Muscularis externa
4- Serosa / Adventitia

Question 5

What are the three layers of Mucosa and what are their characteristics and functions ?

Answer 5

1- Epithelium : secretion, absorption, protection, characteristics differ depending on location
2- Lamina Propria : loose fibrous CT, Blood vessels & lymphoid tissue , contains most gut glands
3- Muscalris Mucosae : 2 thin layers of smooth muscle, responsible for independent movement of mucosa

Question 6

What is the Submucosa , what does it contain and what is its function?

Answer 6

• Collagenous & elastic CT
• Contains small blood vessels , nerve plexus ( Messiner’s) and glands
• Blood vessels supply mucosa , nerves control motility, secretion rate and blood flow

Question 7

What is the Muscularis Externa , what does it contain and what is its function?

Answer 7

• 2 layers of smooth muscle ( inner circular & outer longitudinal )
• contains myenteric nerve plexus ( auerbach’s)
• preforms peristaltic movements in gut

Question 8

What is Serosa / Adventitia , and what is the difference between them?

Answer 8

• loose CT , adipose tissue & blood vessels
• Serosa: suspended by mesentery and covered by peritoneum
• Adventitia : retroperitoneal , no mesentery

Question 9

Label

Answer 9

1-

Question 10

Name the 5 parts making up the Oral Cavity

Answer 10

1- Hard palate

2- Tongue

3- Gums ( Gingiva )

4- Soft palate

5- Cheeks

Question 11

Describe the Hard palate

Answer 11

Anterior 2/3 of palate

lined with epithelium

has underlying bone

Question 12

Describe the Tongue

Answer 12

Dorsum specialised epithelium ( contain taste buds )

Ventrum

Question 13

Describe the Gum

Answer 13

SSK epithelium

Question 14

Describe the Soft palate

Answer 14

• movable posterior 1/3 of palate
• lined with SSNK
• no bony skeleton

Question 15

Describe microanatomy of the Cheeks

Answer 15

SSNK

Question 16

What is the function of the Oesophagus

Answer 16

transport masticated material from pharynx to stomach

Question 17

Label

Answer 17

Question 18

Describe

Answer 18

M- mucosa

E- SSNK epithelium

MM- devloped muscularis mucosae

SM- submucosa with mucous glands

IC/OL - inner circular and outer longitudinal muscularis externa

upper third of ME : skeletal muscle

Middle third of ME: mixed

lower third of ME: smooth muscle

Question 19

What are the functions of the stomach ( 3) ?

Describe how they’re followed out ?

Answer 19

1- storage for ingested food :

2- chemical breakdown of food

3- mechanical breakdown of food

Question 20

List the 4 anatomical regions of the Stomach

Answer 20

1- Cardia

2- Fundus

3- Body

4- Pylorus

Question 21

Label & Describe

Answer 21

R- rugae

M- mucosa : simple columnar epithelium arranged downward , branched tubular glans ( gastric pits ) and glands

MM- muscularic mucosa

SM- submucosa

ME- only part of GI to contain 3 layers of smooth muscle

Question 22

Describe the 4 cells pointed by arrows

Answer 22

1- Mucous cell : protects stomach wall , lubricates

2- Parietal cell: produces hydrochloric acid, stains pink

3- Enteroendocrine cell : produces gastrin

4- Chief cell : granules contain pepsinogen , stains blue + dots ( rER)

Question 23

What are the functions the Small Intestine ( 2)

Answer 23

1- Completes digestion and absorbs nutrients

2- Large surface area to maximise absorption ( 250m^2)

Question 24

What are Plicae Circulares in SM

Answer 24

circular ridges projecting into gut lumen

Question 25

What are Villi

Answer 25

structures projecting from plicae circulares

lined with simple columnar epithelium

contains crypts of lieberkuhn at base

made of enterocytes, goblet cells, paneth cells and enteroendocrine cells

Question 26

what are Microvilli in SM

Answer 26

Microscopic structures projecting from apical surface of enterocytes in Villi

Question 27

What is the Duodenum , what is its function and what does it contain ?

Answer 27

• shortest portion of SM
• recieves bile from gallbladder and digestive enzymes from pancreas
• contains Brunner’s glands in the submucosa which secrete alkaline mucous to counter the acidity fo chyme

Question 28

What is the Jejunum , what is its function and what does it contain

Answer 28

• portion of the SM
• always found empty when dissected ( fasting gut )
• majority of nutrient absorption occurs in jejunum
• contains plicae circulares and tallest villi

Question 29

What is the Ileum , what is its function and what does it contian

Answer 29

• longest segment of SM
• contains lymphoid follicles in submucosa
• functions as immune surveillance of intestinal lume

Question 30

Label

Answer 30

Question 31

Label

Answer 31

v: villus

C: crypts of leiberkuhn

L: lamina propria

MM: muscularis mucosae

box: microvilli

Question 32

What are the function of the Large Intestine ( 4)

Answer 32

1- reabsorption of water and electrolytes ( dehydrating luminal contents )

2- abroption of vitamins

3- compaction of chyme into faeces

4- producing mucus to facilitate passage of faeces

Question 33

What are Crypts of Lieberkuhn

Answer 33

• tubular glands located on villi bases
• epithelial cell factories
• produce enterocytes, goblet , paneth and enteroendocrine cells

Question 34

Describe Taenia coli

Answer 34

3 longitudinal strips of smooth muscles that contract the colon independently

Question 35

What are Colonic Crypts / Glands

Answer 35

simple tubular gland in Large intestine containing goblet cells , colonocytes and enteroendocrine cells