1 - Purpose of the Gut Flashcards
What is the function of the oesophagus?
Transfer bolus to stomach through the thorax by peristalsis. Has a UOS to stop air entering GI and LOS to stop reflux into oesophagus
What fluids make the right environment in the gut?
- Water
- Bicarbonate
- Digestive enzymes
- Acid
What are the functions of the stomach?
- Storage
- Produc chyme by physical and chemical breakdown
- Infection control (HCL)
- Release intrinsic factor to absorb Vit B12
(3 muscular layers)
What is the function of the duodenum?
- C-shaped posteriorly around head of pancreas
- Contains glands secreting HCO3 to neutralise acid chyme
- Osmotic stabilisation by allowing water in
- Liver and pancreas connect with GI at D2 via a common entrance
- Iron absorption
- Active absorption mostly here in small intestine
What is the function of the jejunum and ileum ?
J: Absorbs sugars, aa’s and fatty acids
I: Water, Bile acids, Electrolyes and B12 absorption. B12 at terminal part
Most nutrients absorbed, still a lot of water to be absorbed
What is the structure and function of the large intestine?
- Absorb water and electrolytes
- Produce mucus
- Synthesis vitamins K, B12, thiamine, riboflavin
- Store semi solid contents in colon until expulsion through rectum at certain times, e.g when stomach stretch
Why are diarraheoa and constipation so common?
Fluid balance in the gut is so delicate
How is the gut controlled by the nervous system?
- Enteric system which is both para and sympathetic
Where is the enteric system found and what does it do?
- Submucosal: secretions and blood flow
- Myenteric: motility
Enteric system also controls immune function. It can operate independently of the brain but is connected to ANS. (see previous card)
What is the structure of the gut tube?
Mucosa is selectively permeable interface between lumen to allow movement like secretion of hormomes and mucus and absorption. Lymph, blood and nerves are in deeper layers
What is the main function of the lamina propria?
- Lots of lymphoid nodules and macrophages
- IgA antibodies
What is the function of the serosa?
- Continous with mesentries
- Contains lymph, blood and adipose tissue
What is the epithelia of the gut?
- Stratified squamous non-keratinised in the oesophagus an distal anus
- Simple columnar with specialisations everywhere else
What is:
- An enterocyte
- A goblet cell
- Enterocyte: Main cell of colon and SI. Absorbs as has lymph and vessels directly below. One cell thick with microvilli brush border
- Goblet: Secrete mucus, increase in number from duodenum to colon as more bacteria in colon. Protects gut from friction, bacteria and chemical damage
What is a foveolar cell?
Mucus producing cells lining the stomach to protect it from the gastric acid. Also produces HCO3
How is the surface area in the gut increased?
- Ruggae: stomach
- PC: SI
- Haustra: colon due to contraction of longitudinal muscle
(enterocytes lining villi in the SI also increase SA)
What are intestinal crypts?
Invaginations in the small and large intestine that contain special cells like stem, paneth, enteroendocrine
What are the following cells in the intestine:
- Stem?
- Paneth?
- Enteroendocrine?
Stem: In crypts replace epithelia every 2-4 days
Paneth: At base of crypts and secrete antibacterial proteins to protect stem cells. Secretory vesicles are bright red
Enteroendocrine: Deep in crypts and glands and secrete horomones like gastrin, cholecystokinin and secretin (HCO3)
What are the main secretions into the gut?
- Mainly from the liver and pancreas
What are Brunners glands?
Compound tubular submucosal glands in the duodenum that neutralise gastric juices to protect intestinal walls
What is the difference between Endocrine, Paracrine and Neurocrine?
What are Enteroendocrine cells?
Cells that release endocrine and paracrine hormones due to detected food intake and stretch
What is Gastrin?
Released by G cells in antrum of stomach
Increases gastric acid secretion
Endocrine
