Microanatomy of GIT Flashcards
What is the Gastrointestinal tract responsible for?
( hint: 2 reasons )
1- The mechanical and chemical breakdown of food
2- absorption of nutrients
How long is the GI tract ?
9m
What are the 6 parts of the GI tract?
1- Oral cavity
2- Pharynx
3- Oesophagus
4- Stomach
5- Small intestine
6- Large intestine
What are the 4 layers of the Gut wall? ( inside to outside )
1- Mucosa
2- Submucosa
3- Muscularis externa
4- Serosa / Adventitia
What are the three layers of Mucosa and what are their characteristics and functions ?
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
What is the Submucosa , what does it contain and what is its function?
- 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
What is the Muscularis Externa , what does it contain and what is its function?
- 2 layers of smooth muscle ( inner circular & outer longitudinal )
- contains myenteric nerve plexus ( auerbach’s)
- preforms peristaltic movements in gut
What is Serosa / Adventitia , and what is the difference between them?
- loose CT , adipose tissue & blood vessels
- Serosa: suspended by mesentery and covered by peritoneum
- Adventitia : retroperitoneal , no mesentery
Label
1-
Name the 5 parts making up the Oral Cavity
1- Hard palate
2- Tongue
3- Gums ( Gingiva )
4- Soft palate
5- Cheeks
Describe the Hard palate
Anterior 2/3 of palate
lined with epithelium
has underlying bone
Describe the Tongue
Dorsum specialised epithelium ( contain taste buds )
Ventrum
Describe the Gum
SSK epithelium
Describe the Soft palate
- movable posterior 1/3 of palate
- lined with SSNK
- no bony skeleton
Describe microanatomy of the Cheeks
SSNK
What is the function of the Oesophagus
transport masticated material from pharynx to stomach
Label
Describe
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
What are the functions of the stomach ( 3) ?
Describe how they’re followed out ?
1- storage for ingested food :
2- chemical breakdown of food
3- mechanical breakdown of food
List the 4 anatomical regions of the Stomach
1- Cardia
2- Fundus
3- Body
4- Pylorus
Label & Describe
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
Describe the 4 cells pointed by arrows
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)
What are the functions the Small Intestine ( 2)
1- Completes digestion and absorbs nutrients
2- Large surface area to maximise absorption ( 250m^2)
What are Plicae Circulares in SM
circular ridges projecting into gut lumen
What are Villi
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
what are Microvilli in SM
Microscopic structures projecting from apical surface of enterocytes in Villi
What is the Duodenum , what is its function and what does it contain ?
- 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
What is the Jejunum , what is its function and what does it contain
- portion of the SM
- always found empty when dissected ( fasting gut )
- majority of nutrient absorption occurs in jejunum
- contains plicae circulares and tallest villi
What is the Ileum , what is its function and what does it contian
- longest segment of SM
- contains lymphoid follicles in submucosa
- functions as immune surveillance of intestinal lume
Label
Label
v: villus
C: crypts of leiberkuhn
L: lamina propria
MM: muscularis mucosae
box: microvilli
What are the function of the Large Intestine ( 4)
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
What are Crypts of Lieberkuhn
- tubular glands located on villi bases
- epithelial cell factories
- produce enterocytes, goblet , paneth and enteroendocrine cells
Describe Taenia coli
3 longitudinal strips of smooth muscles that contract the colon independently
What are Colonic Crypts / Glands
simple tubular gland in Large intestine containing goblet cells , colonocytes and enteroendocrine cells
