LECTURE 4 - salivary glands, oesophagus, stomach microanatomy Flashcards
where is the myenteric nerve plexus found
between the inner circular and outer longitudinal layers of muscularis externa
what movement does the myenteric nerve plexus help with
peristalsis
where is the submucosal plexus found
in the submucosa
what is the function of the submucosal plexus
helps control movement and function of the mucosa eg stimulating muscularis mucosae to contract
what are 2 types additional folds which increase the SA in the digestive system
transient eg rugae of stomach
permanent eg plicae circularis of SI
which nervous system controls the myenteric and submucosal plexuses
ENS which is controlled by the ANS
how does the eplithelium of the mucosa receive oxygen and nutrients
by diffusing from BV in the lamina propria
what are the 3 functions of the epithelium in the mucosa
protection
secretion
absorption
what are the 3 sublayers of the mucosa
epithelium
lamina propria
muscularis mucosae
what is the structure of the lamina propria
made of CT fibres and loose areolar CT
what is the function of the lamina propria
functional support- packed with bv, nerves to support teh functions of the epithelium
structural support-
what is the function of the muscularis mucosae
provides movmenent to the mucosa independent of peritalsis
= squeezes glands to move secretions
what marks the boundary between the mucosa and the submucosa
the muscularis mucosae
what is the muscularis mucoase made out of
only made up of smooth muscle
what controls the muscularis mucosae
the eneteric nervous system which is under control of teh autonomic ns
what is the function of the submucosa
same as lamina propria
what is the structure of the musclaris externa
inner circular and outer longitudinal
function of muscularis externa
coordinated contraction of these 2 generates peristalsis
where do you find serosa vs adventita
serosa- when the structure is in contact with space
adventita- when structure is next to adjacent structure
what is the serosa
visceral peritoneum
what is adventita
ct between 2 adjacent structures
what are intraperitoneal organs covered in
serosa ie visceral peritoneum- lined with a single layer of squamous mesothelium
what are retroperitoneal organs covered in
have serosa / visceral peritoneum on anterior surface only and have adventita on their posterior srface
what are the 3 main types of salivary glands
parotid
submandibular
sublingual
which salivary glands have a serous secretion
parotid
which salivary glands have a mixed secretion
submandibular
which salivary glands have a mucus secretion
sublingual
which salivary glands have a dark sttain
parotid glands- have a watery secrtion (have serous cells)
what gives these salivary glands their dark stain
zymogen granules in the cytoplasm
what do zymogen granules in the serous cells do
contain amylase which breaks down carboyhdrates
where are myoepithelial cells found
on the periphery of serous acinus and mucous acinus
what is the function of myoepithelial cells
contract and squeeze acinar secretions into the lumen and facilitate the release of secrtions
where are the nuclei located in individual serous cells
located centrally
which salivary glands have a light stain
sublingual glands (mucus cells)
why are sublingual glands paile staining
because mucus granules do’t pick up dyes
where are the nuclei in mucous acinus
peripheral and flattened due to mucus granules
what type of ducts are striated ducts
interlobular
why do striated ducts look striated>
they have mitochondria aligned in columns
function of striated ducts
extract Na+ and Cl- from secretions passing over and by metabolism generate bicarbonate HCO3- and K+ ie an exchange occurs
what is the function of HCO3-
regulates balance by neutralising acid secrtions
hierarchy starting from submandibular duct
subandibular duct- interlobular duct- intralobular duct
3 functions of saliva
lubrication, protection, digestion
function of carbohydrate rich glycoproteins (mucins) in saliva
lubrication and protection (bacterial adhesion)
function of bicarbonate ions in saliva
protect against bacterial secretions and neutralise acidic vomit
function of lysozyme in saliva
break down bacterial cell walls
function of lactoferrin in saliva
targets iron dependent bacteria
function of immunoglobulin A in saliva
fights bacteria and viruses
function of amylase in saliva
breaks down carbs
function of lipase in saliva
breaks down fats
function of haptocorrin in saliva
vitamin B12- protects Vit B12 from acidic environment of stomach
which nervous system controls salivary secretion
the autonomic nervous system (parasympathetic and sympathetic)
when does salivary secretion increase
when the parasympathetic nervous system is stimulated
sight and thought of food
nausea
when does salivary secretion decrease
when the sympathetic nervous system is stimulated fatigue sleep fear dehydration exercise
what does the Parasymp NS do to increase salivary secretion
accelerates secretion resulting in producing large amounts of watery saliva
myoepithelial cells contract
increased blood flow
what does the symp ns do to decrease salivary secretion
secretion of a small volume of viscous saliva containing high enzyme concentrations, reduced volume produces the sensation of a dry mouth
blood vessels constricted
what state is the oesophagus normally in
normally collapsed with folds of mucosa when empty and only expands when bolus or water moves through
epithelium of oesophagus
thick sacrificial stratified squamous epithelium (non- keratinised by contains a small amount of keratinohyalin granules)
how does the epithelium change when it moves into the stomach
transitions into simple columnar/cuboidal as it approaches the stomach
how is the muscularis mucosae different in the oesophagus
absent/rare near the upper oesophagus but developed near the stomach
function of the muscularis mucosae in the oesophagus
permits independent movement and folding of the mucosa aiding digestion and absorption
how does the muscularis externa of the oesophagus differ
skeletal muscle is present in the pharyngeal end
however at the gastric end there is only smooth muscle
describe the process of peristalsis
contraction of circular muscles behind bolus
contraction of longitudinal muscles ahead of bolus
contraction in circular muscle laer forces bolus forward
what are the 4 key regions of the stomach
fundus, body, pylorus, cardia
function of stomach
storage tank
digestion= sterilisation, sercretion, digestion
absorption
where in the stomach are the parietal glands found
in the body and fundus of the stomach
what do parietal glands secrete
HCl
intrinsic factor
pepsinogen
somatostatin
which areas of the stomach mainly have mucus secretions
cardia and pylorus (beginning and end)
what do pyloric glands secrete
pepsinogen
mucus
gastrin
somatostatin
how does the muscularis externus differ in the stomach
has an extra innermost oblique layer which allows churning in 3D
functional of simple columnar mucus cells
protective
what are the 4 ways in which the simple columnar mucus cells are protective
- mucus coat (secreted by mucus granules)
- secrete insoluble alkaline mucus
- phospholipid enrichment
- high turnover of cells
what do mucus neck cells secrete
soluble acidic glycoproteins
what do simple columnar mucus cells secrete
insoluble alkaline/neutral glycoproteins which form a protective mucus bicarbonate
what do parietal cells secret
intrinsic factor
hcl
what does the HCl secreted by parietal cells do to pepsinogen
acttivates it converting it to pepsinogen
which cell secretes pepsinogen
chief cells
what does pepsin do
break down proteins to amino acids
enteroendocrine 3 cells
G cells - gastrin
ECL cells- histamine
D cells - somatostatin
