Histology Flashcards
Columnar and cuboidal cells are involved in ————–
secretion and obsorption
Functions of epithelium
stratified → ————-
Squamous → ——————
Keratinised → —————
stratified → protective (lots of layers)
Squamous → thin for diffusion (squashed cells
Keratinised → skin (mechanical stress)
Ends of epithelial cells
apical end = ———————-
basal end = ———————–
Ends of epithelial cells
apical end = upper end (exposed to outside of body, or internal cavity)
basal end = attached to basement membrane, anchored to connective tissue
——— are the absorptive cells of the intestine
enterocytes
GALT
Gut Associated Lymphoid Tissue = lymphocytes in the GI tract wall, part of the immune system
Myenteric plexus location
Between the two muscle layers of the muscularis externa
Layers of GI tract wall
M,S,M,S
Mucosa»_space; epithelium (enterocytes), lamina propria (loose connective tissue + GALT), muscularis mucosae (thin SM)
Submucosa»_space; loose connective tissue, submucous plexus (part of ENS)
Muscularis externa»_space; inner circular layer, myenteric plexus (part of ENS), outer longitudinal layer
Serosa/adventitia»_space; connective tissue
The enteric nervous system has two nervous plexuses in the GI tract wall. They are ———-
1) Submucous plexus (in submucosa) - controls LOCAL intestinal secretion, absorption and contraction of submucosal muscle
2) Myenteric plexus (between muscle layers) - increased muscle tone, increased rhythmic contractions, increased conduction velocity of slow wave activity
In the mouth and pharynx, stratified squamous epithelium covers the ———— and respiratory epithelium covers ————–
In the mouth and pharynx, stratified squamous epithelium covers the oral cavity, oropharynx, laryngopharynx, and tongue, and respiratory epithelium covers the nasopharynx and nasal cavity.
———- papillae cover most of the dorsal surface of the tongue
Filiform papillae (no taste buds)
The pharynx houses the tonsils (4) =
1) Pharyngeal tonsils (adenoids)
2) Palatine tonsil (tonsils)
3) Lingual tonsil
4) Tubal tonsil (leads to ear - covered in ENT)
Tonsils are ——– tissue
Lymphoid tissue (part of the immune system)
Stratified squamous epithelium covers the mouth because ——–
it comes into contact with food which may abrase the surface of these structures so needs a protective function (also these cells are easily replaced)
There is —— AND ——– epithelium present in the nasal cavity.
Olfactory AND respiratory
Gastro-oesophageal junction: ——— epithelium»_space; ——– epithelium
stratified squamous epithelium»_space; simple columnar epithelium (of the stomach)
Mucosa of stomach - key differentiators
Gastric pits → mucus cells (produce mucus + bicarbonate to protect against the acidic environment)
Gastric glands → stomach secretions
Isthmus → the point where the pit becomes the gland
Cells in the gastric glands of the stomach
Parietal cells → HCl
Stem cells → make more cells
Chief cells → secrete digestive enzymes
Enteroendocrine cells → produce hormones to control secretions and motility
In Barrett’s oesophagus ——– epithelium of the oesophagus changes to ———- epithelium because ——–
This can predispose to ———
In Barrett’s oesophagus the stratified squamous epithelium changes of the oesophagus changes to the simple columnar epithelium in order to protect the oesophagus from increased exposure to gastric acid. This change in cell type can predispose to cancer development.
The gastroduodenal junction is marked by the —–sphincter
pyloric sphinctor
Mucosa of small intestine - key differentiators
Villi (projections)
Crypts of Lieberkuhn (pits)
Small intestine - cell functions
Enterocytes →
Goblet cells →
Paneth cells →
Enterocytes → absorptive cells, covered in microvili
Goblet cells → mucus for lubrication and protection
Paneth cells → antibacterial products to keep bacterial flora in check
Small intestine parts - key differentiators
Duodenum = Brunners’s glands (alkaline mucus to protect from acidic chime) Jejunum = tallest villi in small intestine (located on plicae circularis) Ileum = Peyer’s patches (GALT)
Large intestine parts - key differentiators
Arranged into crypts (tubular glands which extend down to the muscularis mucosae)
No villi
Taeniae coli: outer longitudinal muscle (of muscularis externa) is in 3 strips instead of being continuous - creates haustra
The outer longitudinal muscle of the large intestine is in —– strips instead of being continuous - these are called ————– and create pouches called ————
The outer longitudinal muscle of the large intestine is in 3 strips instead of being continuous - these are called taeniae coli and create pouches called haustra.
The appendix has a large amount of ————— tissue
lymphoid tissue
Hexagonal lobules of the liver have a ———- in the centre and ———— at each corner.
Hexagonal lobules of the liver have a central vein in the centre (branch of the hepatic vein) and portal triads at each corner (portal vein, hepatic artery, bile duct).
Sinusoids in the liver lobules
gaps between hepatocytes that blood flows through (take blood from the hepatic artery and portal vein to the central vein)
Kupffer cells
macrophages in the sinusoids
Perisinusoidal space (space of Disse)
Between hepatocytes and sinusoid
Porta hepatis
opening where vessels enter at the liver hilum
Hepatic stellate cells
Fibroblasts (make connective tissue) in the perisinusoidal space (space of Disse) - make scar tissue in liver disease
Liver blood supply
Hepatic artery → supplies liver with oxygenated blood
Portal vein → carries deoxygenated, nutrient rich blood from spleen, stomach and intestines
Hepatic vein → takes deoxygenated blood from the liver to the IVC
Bile is produced by hepatocytes and flows via bile canaliculi to the bile ducts
Bile is produced by hepatocytes and flows via ———— to —————-
———— are the cells lining the biliary tree
Cholangiocytes
Gallbladder = ———– epithelium
simple columnar
What causes gallbladder contraction?
Nervous → vagal (via vagus nerve)
Hormonal → cholecystokinin release in the duodenum when fatty food enters it
The majority of the function of the pancreas is {endocrine/exocrine}
exocrine (important for GI)
Pancreas - exocrine function
producing digestive pancreatic enzymes
The enzymes produced by the exocrine pancreas are inactive proenzymes and become activated when ————–
they arrive in the duodenum (trypsinogen is converted into trypsin which activates other enzymes)
Acinus
small cavity surrounded by secretory cells (acinar cells) in the exocrine pancreas.
Acinar cells
functional unit of the exocrine pancreas. Produce, store and secrete digestive enzymes.
Intercalated duct
collects secretions from acinar cells in the exocrine pancreas.
Centroacinar cells
extension of intercalated duct cells into the acinus of the exocrine pancreas
Zymogen granules
organelle responsible for sorting, packaging, and regulation of secretion of digestive enzymes (within acinar cells of the exocrine pancreas)
endocrine cells of pancreas
Islets of Langerhans
In the pancreas, the intercalated duct extends into the ——- because —————–
In the pancreas, the intercalated duct extends into the acinus because the pancreas must be protected from the harmful enzymes produced.
