Histology Flashcards
oral cavity, oropharynx and laryngopharynx
covered by stratified squamous epithelium which is keratinised
nasal cavity and nasopharynx
covered by respiratory epithelium
oral cavity/tongue anterior 2/3 vs posterior 1/3
anterior - stratified squamous epithelium (thin on ventral surface, thick and with papillae on the dorsal surface
posterior - covered by smooth stratified squamous epithelium which, except for the circumvallate papillae, lacks papillae but does have substantial lymphoid aggregates in the submucosa
what are the 4 major layers to the GI tract from lumen out
- mucosa (epithelium sits on basal lamina, lamina propria- loose connective tissue, muscularis mucosae - thin layer of smooth muscle)
- submucosa: dense irregular connective tissue
- muscularis externa (two thick layers of smooth muscle - inner circular, out longitudinal)
- serosa or adventitia (outer layer of connective tissue - attaches to other organs or suspends GI tract)
does the GI tract go from smooth muscle at top (proximal oesophagus) to skeletal at the bottom
NO
other way round
histology of oesophagus
non-keratinised stratified squamous epithelium
stomach histology
simple columnar epithelium inc chief cells, parietal cells and enteroendocrine cells
what do parietal cells produce
HCl
what do chief cells produce
enzyme granules in apical cytoplasm and secreting digestive enzymes into lumen
how to does the histology of the stomach differ in the different sections
cardia - (just after LOS) - deep gastric pits that branch into loosely packed, tortuous glands
body - shallow gastric pits with long staight gastric glands
pylorus- deep gastric pits with branched, coiled gastric glands at a higher density than in the cardia
what are the gaps in between the villus also referred to as?
crypts of lieberkuhn
how long is the duodenum/jejeunum/ileum
D - 25 cm
J - 2m
I - 2.75m
what is in the submucosa of the duodenum
brunners glands
describe the jejunum histology
tallest villi, located on permanent circular folds of the mucosa and submucosa, the plicae circularis. lymphoid follicles infrequent
ileum histology
shorter villi
aggregations of lymphoid follices called peyers patches found in the submucosa and often extending into the lamina propria
the most numerous cells, they are tall columnar cells with a brush border and are the absorptive cell
enterocytes
produce mucin to protect epithelium and lubricate passage of material
goblet cells
found at the base of the crypts of Leiberkhun, they have defensive unction and have regulating bacterial flora - secrete lysozyme and defensins
paneth cells
produce hormones that contribute to the control of secretion and motility (eg gastrin, chylecystokinin (CCK), vasoactive intestinal peptide (VIP))
neuroendocrine cells
found at the base of the crypts of lieberkhun, divide to replenish epithelium
stem cells
what are brunner’s glands stimulated by and what do they do
stimulated by the presence of chyme.
they produce a thin, alkaline mucous to neutralise the chyme
what does bile enter the 2nd part of the duodenum via
ampulla of vater
what cells are for the removal of salts and water
absorptive cells
secretion of mucus to lubricate the colon
goblet cells
what are the 3 muscular strips of longitudinal muscle on the large intestine called
teniae coli
anal canal
keratinised stratified squamous epithelium of the surrounding skin
where is the myenteric plexus found and what does it control
between the muscle layers of the muscularis externa
controls gut motility
what controls the musclaris mucosae and helps regulate secretion in the epithelium
submucosal plexus
what does the exocrine pancreas produce in the GI system and where does it enter via the pancreatic duct
produces about a litre of digestive juice containing proteases (to break down proteins)
lipases (to break down lipids) nucleases (to breakdown DNA/RNA)
amylase (to breakdown starch, etc, each day.)
These enter the duodenum via the pancreatic duct
what does the endocrine pancreas consist of?
small, scattered islands of tissue called islets of Langerhans, which produce a number of hormones including insulin and glucagon. Islets make up about 1%-2% of the pancreas
what are the enzyme produced by the exocrine pancreas
inactive proenzymes
what happens when the pancreatic secretion enters the duodenum
enteropeptidase converts the inactive proteolytic enzyme trypsinogen into the active form, typsin
this begins a cascade that results in the activation of the other enzymes
what are the islets of Langerhans
groups of pancreatic cells secreting insulin and glucagon
why is the apical part of the pancreatic acinus often very eosinophilic
due to the presence of zymogen (pre-enzyme) granules
why are the basal part of cells of the pancreatic acinus typically basophilic
due to extensive RER
what is the gallbladder lined by
tall simple columnar epithelium backed by a lamina propria of loose connective tissue rich in blood vessels and lymphatic vessels a coat of smooth muscle and outer collagenous layer of adventitia (brush border)
under what control does the gallbladder deliver bile to the duodenum
vagal and via release of the hormone cholecystokinin by endocrine cells of the duodenum when fatty food enters it
