Histology Flashcards
oral cavity, oropharynx and laryngopharynx
stratified squamous epithelium which is generally not kertainised
nasal cavity and nasopharynx
respiratory epithelium
anterior 2/3 of tongue
stratified squamous epithelium
thin on ventral surface
thick and pipillae on the dorsal surface
posterior 1/3 tongue
smooth stratified squamous epithelium which except for the circumvallate papillae, lacks papillae but does have substantial lymphoid aggregates in the submucosa
entrance to the oropharynx
the pharynx has a ring of lymphoid tissue composed of the tonsils
there are deep crypts lined with stratified squamous epithelium and lymphoid folicles
digestive tract layers
mucosa
submucosa
muscularis externa
serosa or adeventitia
mucosa
epithelium- sits on a basal lamina
lamina propria- loose connective tissue
muscularis mucosae- thin layer of smooth muscle
submucosa
loose connective tissue
muscularis externa
two thick layers of smooth mmuscle, an inner circular layer and an outer longitudinal layer
serosa or adventitia
outer layer of connective tissue that either suspends the digestive tract or attaches it to other organs
location of submucosal glands
oesophagus
gastro-oesophageal junction
abrupt transition from stratified squamous epithelium of the oesophagus to the simple columnar epithelium of the cardia of the stomach
specialty of the stomach lining
gastric pits which have 1-7 gastric glands at the bottom
lining of gastric pits
surface mucuous cells
cells of gastric glands
not evenly distributed
isthmus- parietal and stem cells
neck- mucuous and parietal cells
fundus (base)- chief cells with a few parietal and enteroendocrine cells
chief cells
digestive enzyme secreting cell
parietal cell
hydrocholric acid producing cell
cardia
deep gastric pits that branch into loosely packed tortuous glands
body
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
muscularis externa of the stomach
contains an extra layer which is oblique to the usual circular and longitudinal muscle layers
internal to the circular layer
it aids the churning of the stomach
gastroduodenal junction
there is an abrupt transition from stomach mucosa to duodenal mucosa
the inner, circular layer of smooth muscle is markedly thickened to form the pyloric sphincter
components of the small intestine
duodenum
jejunum
ileum
small intestinal epithelium
villi
crypts of lieberkuhn
pits drilling downwards between adjacent villi
duodenum
contains brunner’s glands in the submucosa
brunner’s glands
when stimulated by the presence of chyme, they roduce a thin, alkaline mucuous to neutralise the chyme
jejunum
tallest villi, located on permanent circular folds of the mucosa and the submucosa
lymphoid follicles infrequent
ileum
short villi
peyer’s patches found in the submucosa and often into the lamina propria
peyer’s patches
aggregations of lymphoid follicles
enterocytes
the most numerous cells
tall columnar cells with a brush border
principle absorptive cell
goblet cells
produce mucin to protect epithelium and lubricate passage of material
paneth cells
found at the base of the crypts of lieberkuhn
defensive function
a role in regulating bacterial flora
secrete lysozyme and defesins
enteroendocrine cells
produce hormones that contribute to the control of secretion and motility
eg gastrin, cholecystokinin, VIP
stem cells
found at the base of the crypts of lieberkuhn
they divide to replenish epithelim
cells found in the small intestin
enterocytes goblet cells paneth cells enteroendocrine cells stem cells
cells in the large intestine
absorptive cells
goblet cells
arranged in straight, tubular, glands, referred to as crypts, that extend down to the muscularis mucosae
absorptive cells in the large intestine
for removal of salts and thereby water
appendix
crypts are far less abundant
typically circular arrangement of lymphoid tissue in the submucosa and often lamina propria
the lymphoid tissue tends to decline with age
rectoanal junction
distinct junction between the mucosa of the rectum and the anal canal
anal canal
continuous with kertinised stratified epithelium of the surrounding skin
myenteric plexus location
between the muscle layers of the muscularis externa
submucosal plexus location
in the submucosa
myenteric plexus role
controls gut motility
submucosal plexus role
controls the muscle of the muscularis mucosae
helps regulate secretion in the epithelium
ganglion
groups of neurons living outside the brain and spinal cord
tonsils
palatine tonsils, lingual tonsils, tubal tonsils and pharyngeal tonsils
development of the liver and the pancreas
as an outgrowth of the gut
the parenchyma of the liver and the pancreas
glandular epithelial cells
liver capsule
covered by a collangenous tissue capsule which is covered by a layer of mesothelial cells derived from the peritoneum
structure of the liver
made up of segments called lobules
lobules
each is approx hexagonal and has a branch of the hepatic vein called the centrolobular vein at its centre and portal triads at each corner
portal tracts
branches of hepatic portal vein, hepatic artery, bile ductule
lymphatic vessels
lining of portal tract
squamous cuboidal cells called cholangiocytes
hepatocytes
the main cells of the liver
polyhedral epithelial cells form plates or sheets of cells with spaces in between for blood to flow through
sinusoids
blood channels lined by endothelial cells and there is a narrow lining between these and the hepatocytes
space of disse
space between lining cells (sinusoids) and hepatocytes
microvilli of the liver
project into the space of disse
endothelium of sinusoids
fenestrated so the liquid component of blood generally has free access to the hepatocytes but the blood cells do not
support of the liver
the portal tracts are accompanied by collagenous connective tissue
parenchyma has reticular fibres (type III collagen) along with some type I collagen that is found in the space of disse
hepatic stellate cells (Ito)
found scattered in the space of disse
modified fibroblasts and make connective tissue
they also store vit A within fat droplets in their cytoplasm
kupffer cells
resisdent macrophages of sinusoids
remove particulate matter from the blood and help remove worn out RBCs
bile definition
alkaline solution containing water, ions, phosphlipids, bilirubin and bile salts
bilirubin
a pigment which results from the breakdown of haemoglobin in the spleen and when excreted in bile is the principal cause of the brown colour of faeces
bile salts
necessary for the emulsification of fats in the digestive tract
primary bile
produced by hepatocytes
modified in several ways eg additions of bicarbonate ions and water by the cholangiocytes
cholangiocytes
cells that line the biliary tree
movement of bile
bile flows via bile canaliculi toward the bile ducts in the portal tracts and then to the hepatic ducts
bile canaliculi
small channels formed by tight junctions in the cell membranes of adjacent hepatocytes
the gall bladder definition
a muscular sac which stores bile and modifies the bile stored within it
lining of the gall bladder
tall columnar epithelial cells with a brush border
lamina propria of loose connective tissue rich in blood vessels and lymphatic vessels, a coat of smooth muscle and an outer collagenous layer of adventitia
mucosa of the gall bladder
has folded mucosa when empty- this flattens when distended
what happens to the majority of the bile arriving from the liver?
it is removed by the gall bladder
process by which the gall bladder removes bile
is actively pumps Na+ and Cl- ions from the bile into the spaces between adjacent epithelial cells
water then follows due to the increase in osmotic pressure in these spaces, which become distended with fluid when the gall bladder is actively concentrating bile
how is the water removed from the gall bladder?
it is carried away, largely by the lymphatic vessels of the lamina propria
process by which bile is removed from the gall bladder
it is stimulated to contract and deliver bile to the duodenum, both under nervous control (chiefly vagal) and via release of CCK
why is the pancreas unusual?
both an endocrine and an exocrine duct
role of the exocrine pancreas
produces about a litre of digestive juices containing proteases to break down proteins, lipases to break down lipids, nucleases to breakdown DNA/RNA and amylase to breakdown starch etc
where do digestive juices from the pancreas go?
they enter the duodenum via the pancreatic duct
endocrine pancreas
consists of small, scattered islands of tissue called islets of langerhans which produce a number of hormones including insulin and glucagon
exocrine pancreas components
numerous serous acini and ducts
cells of the basal part of the exocrine pancreas
very basophilic because they contain large amounts of RER
cells of the apical part of the exocrine pancreas
very eosinophilic due to the presence of zymogen granules
what happens when the pancreatic secretion arrives in the duodenum?
an enteropeptidase converts the inactive proteolytic enzyme trypsinogen into the active form, trypsin
this begins a cascade that results in the activation of other enzymes
exocrine pancreas lining
thin connective tissue capsule that is continuous with connective tissue septa that divide the gland into lobules
intercalated ducts of the pancreas
the smallest ducts
do not start where the acinus ends but rather extend into it
centroacinar cells
duct cells within the acini
their nuclei and cytoplasm do not stain as intensly as the secretory cells
hepatopancreatic ampulla (of vater)
where the main pancreatic duct joins the common bile duct and opens into the duodenum on a papillae
