BMS1058 - Gastrointestinal system Flashcards
(20 cards)
What is the 4 layered structure of the GI tract?
Mucosa - absorbative surface, flod capillaries, metabolic active part
Submucosa - learger blood vessels heading off to liver, lymphatic branches, ANS
Muscularis - double muscle layer - circular and longitudinal
Serosa - thick layer of connective tissue for separation of stomach and non-stomach
The stomach varies in size from __ml to _L. Expands to _L.
Has basolateral foldes (also known as ______, which stretch out and increase _______.
The stomach is highly adapted for muscular contraction (occurs at ______) and secreition (from ____ in the body).
75ml - 1L
2L
Rugae
surface
antrum
pits
How does the Duoedum and Jejunum compare to the ileum? parts of small intestine)
DUODENUM and JEJUNUM
- closer to the stomach
- larger lumen
- highly vascularised, appears dark red (more absorption)
- more muscular Brunners glands (mucus and bicarbonate)
- longer villi and larger surface area (increased absorbtion)
ILEUM
- smaller food volume
- Peyers patches (lymphatics) - protection from bacteria
- paler appearance
- less muscles
- shorter vili and smaller SA
_______ ________ function varies between intestinal segments.
_______ _______ proteins prevent molecules and bacteria passing through intercellular space between enterocytes. There are more of these proteins in the ________ as there is more _________.
Gut barrier function
Tight junction proteins
ileum -> more bacteria
LEAKY GUT:
Change in expression of TJ proteins Claudin and Occludin.
CHECK PANOPTO
Which organ secretes the msot hormones in the body?
The gut.
What hormones does the stomach secrete? [don’t need to know but good to learn]
Gherelin - hunger, growth hormone release
Gastrin - acid secreition
What do are most hormones released in the GI tract releated to?
Hunger and acid (in stomach)
GI function motility and appetite.
Gut-brain axis.
Most interact with hypothalamus related to food intake and hunger. Secondary switch on/off functions.
Where are Peyer’s patches located? What do they do? What are they covered by?
Located in Ileum -> lamina propria layer of mucosa adnd extending into submucosa.
Catch microorganisms and other antigens entering intestinal tract by dendritic cells, B-lyphocytes and T-lymphocytes.
They also react to dietary proteins.
Covered by a special epithelium microfold cells, giving it direct contact to lumen.
What are M (microfold) cells?
Feature of the ileum and colon.
In contact with lumen. Lack microvilli.
Part of GI-associated lymphoid tissue. Link directly to lymphatic system.
[check panopto for rest of this slide]
How is the small intestine specialised to increase surface area?
Folding, villi and microvilli
Describe the structure and function of the largen intestine (colon)
1.5m long. Large lumen. Decreases in lumen diameter.
4-layer structure. Longitudinal muscle in 3 longitudinal bands (taeniae coli). The gaps only have circular muscle
Skeletal and smooth muscle.
Function: water absorbtion plus bacterial function.
Describe Crypts in the large intestine? What do they do?
Intestinal glands.
Columnal cells with short microvilli
Absorptive cells are numerous
Muscus producing (goblet) cells for protection.
Increase surface area in colon as there is no villi.
There are different _______ of contractions in different _______ of the gut.
What is the name of the normal patter of gut contractions when the gut is empty?
What regulates gut contractions?
different types - different segments
Migrating motor complex
Neural and hormonal inputs switch on/off.
Describe the contractions of the stomach
2 different muscle layers lead to 3 different patters:
PROPULSION - construction starts in body, moves to antrum.
Circular muscle at pylorus closes with each gastric contraction. But always 1-2mm open, allowing liquids through.
GRINDING - within antrum to reduce particle size.
RETROPULSION - backwards to mix into body
Describe small intestinal motility
Up to 5-6h transit
Controlled movements from duodenum to end of ileum.
Allows absorbtion as not too slow/fast and mixed well.
FREQUENCY GRADIENT of rhythmic contractions (stronger and more frequent in the duodenum as larger food bolus).
REGIONAL MOTILITY - contractions only where food bolus is (enerby efficient). Contractions follow distention (stimulus via enteric NS).
2 types of motility - periods of segmentation and peristalsis
Describe segmentation in the small intestine
Circular mixing motion - altered by hormones, enteric NS and autonomic NS.
Contractions of circular muscle layer - breaks up bolus. Incease SA.
Alternate contraction and relaxation of segments mixes chyme with digestive secretions.
Describe peristalsis in the small intestine.
Circular muscles contract just behind mass, moving bolus forward. Pushed into receiving segments where circular muscles are relaxed.
Affected by hormones and autonomic NS.
Distension in the terminal ileium relaxes ileocaecal sphincter, pushing bolus into large intensine and prevents backflow of bacterial components.
How many segments of longitudinal muscle are in the colon?
How does peristalsis occur in the large intestine? What is it triggered by?
How long does it take to move bolus through the colon?
3 segments
Mass peristalsis: large wave 1/3 of way, so 3 mass peristalsis to move all the way.
Triggered by:
- co-ordinate reflex goverened by local distension.
- control reflex arcs (gastro-colonic) activity and hormones from stomach.
72h to move 1.5m of full colon.
How is defaecation regulated?
Neurally regulated. Autnomic (involuntary) and somatic (voluntary) pathways.
Rectal distension triggers defecation reflex. Relaxation of internal sphincter and contraction of external sphincter.
All segments of the GI tract have 2 forms of motility (______ and ________).
The main stimulus for contraction is ________ (by the ENS). This stimulus in the region of the GI tract immediately before a sphincter causes it to ______. This is known as ______ ______ contraction.
This stimulus in one segment will _____ contraction and motlity in the preceding segments. THis is known as __________ _________.
mixing and propulsion
Distension
open
feed forward contraction
inhibit
feedback inhibition.
