Digestive system Flashcards
What are the 4 layers of the gut wall?
The mucosa
The sub-mucosa
The muscular externae
The serousa
What part of the gut in not intra-peritoneal?
The transverse colon- its retro-peritoneal
Anything superior to the diaphragm also.
Name the layers of the mucosa.
Epithelium
Lamina Propria
Muscularis Internae
What glandular secretion arises from the mucosa?
Mucous
What is the submucosa?
A layer of connective tissue that holds glands, arteries, veins and nerves.
What is the muscle arrangement in the muscularis externae?
Inner circular layer
Outer longtitudinal
What is the peritoneum?
The serousa that in invaginated by the gut. It consists of a connective tissue layer and simple squamous mesothelial cells.
What are the functions of the GI tract?
- Port of entry for food
- Mechanically disrupt food
- Temporarily store food
- Chemically digest food
- Kill pathogens
- Move food through it
- Absorb nutrients
- Eliminate watse
What things must we absorb from the GI tract?
Sugars Fatty acids Amino acids Minerals Vitamins
What is the role of the mouth?
Starts chemical digestion with amylases and lipase
physically disrupts with chewing.
What does saliva do?
Salvia is bacteriostatic , protects teeth, helps swallowing, protects the mouth and is alkaline. It is the first step in chemical disruption of our food.
Where are the fastest transit points in the GI system?
Oesophagus and rectum/ anus
Describe the muscularity though out the oesophagus.
Upper end is under voluntary control and contains skeletal muscle.
Lower down its smooth muscle which operates involunatrily.
This gives rapid peristaltic forces moving a food bolus to the stomach in 8-9 seconds even if upside down.
Describe the neural innervation of the oesophagus?
Sub-mucosal plexus
Myenteric plexus
What epithelium is normally found in the oesophagus?
Stratified squamous non-keratinised.
The oesophagus is not surrounded by serousa so what likes outside of the muscular externa?
Tunica adventitia.
Describe the chemical sorption of food in the stomach.
HCl gives pH of
Enzymes like pepsin break up food.
What roles does the stomach have?
Food store Receptive relaxation Rhythmic contraction Secretion of acid and enzymes Protection from self digestion - mucous secretion Make hypertonic chyme Control delivery of Chyme to duodenum
What are the macroscopic folds in the stomach called?
Rugae
How many layers of muscle are seen in the stomach’s muscularis externa?
3 layers of smooth muscle
Where do you find gastric pits?
Stomach
Whats the role of goblet cells in the stomach?
Secrete mucous to protect stomach from enzymatic degradation and pH damage. The mucous contains HCO3- to neutralise the H+.
Mucous is released in response to stretch, acidity and enzyme presence.
Alcohol and aspirin can harm these cells.