Histology of Digestive system Flashcards
The main function of the gastrointestinal tract
break down food for absorption into the body.
this is done in five main phases;
: Ingestion, Fragmentation, Digestion, Absorption, Elimination
There are four distinct layers of the tract:
Muscularis propria
Mucosa
Submucosa
adventitia.
Gastrointestinal system
is basically a muscular tube that is lined with a mucous membrane which is regionally specialized to serve the changing functions of the system from mouth to anus.
mucous membrane
is protective, secretory, absorptive or a combination of these
tissue that gives strength to wall of the tract and assist in moving food along.This tissue is arranged differently throughout the tract
Muscle tissue
Lymphoid tissue.
Lymphoid tissue is associated with the tract due to the system being continuous with the external environment and this being a potential entry points for pathogens.
The mucosa made up of 3 components are?
epithelium
supporting lamina propria
smooth muscle- muscularis mucosae
The mucous components produces what?
local movements and folding of mucosa.
At four points along the tract the mucosa undergoes abrupt transitions:
Gastro-oesophageal junction- Stratified squamous epithelium in the oesophagus becomes simple columnar epithelium in the stomach
Gastroduodenal junction- long pits and short, coiled glands in the pyloric stomach to villi and crypts in the duodenum
Ileocecal junction- villi with crypts in the small intestine to only crypts in the large intestine
Rectoanal junction-simple columnar epithelium in the rectum to stratified squamous epithelium in the anus- for absorption of fliud
function of crypts
allow the intestine to regenerate a new cell forming a new layer.
layer of loose collagenous tissue
SUBMUCOSA
supports mucosa
contains blood vessels and lymphatic and nerves
Mascular propria
muscular wall propria consist of smooth muscle fibers.
This is usually arranged as:
Inner circular layer
Outer longitudinal layer
Action of the two layers, which are at right angles to each other, is to contribute
to peristaltic contraction
An outer layer of loose supporting tissue
Adventitia
layer Referred to as serosa, where the gut lines the peritoneal cavity, and is lined by mesothelium.
adventitia
adventitia conducts
Conducts major vessels, and nerves and contains variable amounts of adipose tissue.
what initiates the contractile of smooth muscle
Contraction of smooth muscle is initiated by pacemaker cells known as the interstitial cells of Cajal.
Autonomic Innervation
regulation of glandular secretions and smooth muscle of the gut is mediated via the intrinsic nervous system.
This has sympathetic and par
In the submucosa there are clusters of parasympathetic ganglion cells:
Submucosal plexus- a collection of small clusters of parasympathetic ganglia which supply the mucosal glands and smooth muscle of muscularis mucosae.
Myenteric plexus- a collection of larger clusters of parasympathetic ganglia which are found between the two layers of the muscularis propria and supplies surrounding smooth muscle.
protective layers found in the oral cavity, pharynx, oesophagus, and anal canal.
stratified squamous epithelium.
Stratified mucosal lining is well suited to sites of potential frictional trauma – such as those associated with mastication, swallowing or defecation.
secretory
Only occurs in the stomach.
Has long tubular glands that are simple or branched.
These glands produce various combinations of acid and digestive enzymes to facilitate digestion and also secrete mucous to protect the mucosa from injury.
Absorptive
Typically found in the small intestine.
Mucosa is arranged into small finger-like projections known as ………………………………………i which increase the surface area of the mucosa.
Villi
Absorptive/Protective
Lines entire large intestine.
Mucosa is arranged in tightly packed straight tubular glands which have specialized cells for water absorption.
Also has mucous-secreting goblet cells to lubricate the passage of faeces.
