Histology Flashcards
what 4 layers make up the basis of the GI tract?
Mucosa
Submucosa
Muscularis externa
Serosa/Adventitia
what is the mucosa made up of?
Mucous membrane
Lamina propria
Muscularis mucosae
describe what the submucosa generally contains.
CT, larger blood and lymph vessels, glands and submucosal plexus
describe what the mucosa generally contains.
Mucous membrane containing epithelium and maybe gland cells
Lamina propria containing loose CT, capillaries, enteric neurons and lymphoid tissue
Muscularis mucosae which is a thin layer of smooth muscle
describe what the muscularis externa generally contains.
Circular muscle, longitudinal muscle with the myenteric plexus inbetween
describe what the serosa generally contains.
CT which either suspends or attaches the organ to other organs
what are the varying functions of the mucosa throughout the GIT?
Proctective, secretory, absorptive
what type of epithelium it the oral cavity, pharynx, oesophagus and anal canal lined with?
Non-keratinised stratified squamous
what type of epithelium lines the stomach?
simple columnar epithelium with extensive tubular glands
which type of epithelium lines the small intestine?
simple columnar epithelium with villi and tubular glands
which type of epithelium lines the large intestine?
simple columnar epithelium with tubular glands
what is the sulcus terminalis?
a v-shaped depression separating the anterior and posterior parts of the tongue
what are the differences in the histology of the anterior 2/3 and posterior 1/3 of the tongue?
Anterior is thick with papillae on the dorsal surface
Posterior is smooth and lacks papillae (except circumvallate) BUT has lots of lymphoid aggregates in the submucosa
what are the 4 types of papillae found on the tongue?
Filiform
Fungiform
Circumvallate
Foliate
describe structure of filiform papillae.
conical, elongated projections of CT covered with highly keratinised stratified squamous epithelium
Which papillae is the smallest and most frequent?
filiform
describe the structure of the fungiform papillae.
mushroom shaped projections scattered amongst the filiform papillae
where are fungiform papillae located?
all over the anterior tongue but mostly at the tip
where are the filiform papillae located?
all over the anterior tongue
describe the structure of the circumvallate papillae.
large, dome-shaped structures surrounded by moat-like invaginations, which contain numerous taste buds.
where are circumvallate papilae located?
just anterior to the sulcus terminalis
how many circumvallate papillae are there?
8-12
where are foliate papillae located?
on the posterior lateral edges of the tongue
describe the structure of the foliate papillae
parallel low ridges separated by deep mucosal clefts aligned at right angles to the long axis of the tongue
which papillae have taste buds?
fungiform, foliate and circumvallate
which type of papillae become less frequent with time?
Foliate papillae
what surrounds the entrance to the oesophagus?
a ring of lymphoid tissue made up of palatine, lingual, tubal and pharyngeal tonsils
what causes the lumen of the oesophagus to appear branches?
the longitudinal folds in the mucosa
what distinguished the oesophagus histologically from other parts of the GIT?
it has submucosal glands
what type of muscle makes up the upper 1/3 and lower 1/3 of the oesophagus?
upper 1/3 = striated muscle (continuation from pharynx)
lower 1/3 = smooth muscle
what innervates the upper and lower parts of the oesophagus?
Upper: somatic motor neurons of vagus
Lower: visceral motor neurons of vagus
what change is seen at the gastro-oesophageal junction in the mucosa?
epithelium changes from stratified squamous to simple columnar epithelium.
what are the rugae of the stomach composed of?
mucosa and submuscosa
what lines the surface of the stomach and the gastric pits?
surface mucous cells (epithelial cells with mucous granules in a cup at the apical end)
how do prostaglandins protect and repair the mucosa of the stomach?
by stimulating secretion of bicarbonate and increasing the thickness of the mucosa causing vasodilation of the lamina propria to improve nutrient delivery to the damaged area, optimising repair
what effect does aspirin have in the stomach?
it supresses the production of prostaglandins and if it gets in direct contact with the stomach wall it interferes with hydrophobic properties of the gastric mucosa
Into which layer do the gastric glands extend down into?
the muscularis mucosae
the cells of the gastric glands create gastric juice, what does this contain?
HCl
Pepsin
Mucous
Intrinsic factor
what do chief cells in the gastric glands secrete?
pepsinogen
what is the intrinsic factor produced by parietal cells in the gastric glands?
a glycoprotein which binds to B12 allowing its absorption
what do enteroendocrine cells produce and what is their function?
Gastrin and other hormones which are secreted into the lamina propria where they enter circulation and act locally on other gastric cells
how do the gastric pits and glands differ in the different parts of the stomach?
Cardia = deep gastric pits branching into loosely packed torturous glands Fundas = shallow gastric pits with long straight gastric glands Pylorus = deep gastric pits with branched, coiled gastric glands at a higher density than in the cardia
which part of the GIT has an additional muscle (to the circular and longitudinal) layer and why?
stomach, to aid in the churning action
