gastrointestinal tract Flashcards
how are carbohydrates dealt with?
broken first down by enzymes
amylase in saliva
then further down into simpler foms such as disaccharides
maltose is broken down by…
maltase
sucrose broken down by…
sucrose
how are proteins broken down?
peptidase
into amino acids
how are lipids broken down
lipase
fatty acids removed from glycerol back bone
how is food energy measured?
how much every can be derived from it
calories
what is BMI
weight relative to height
what should BMI be coupled with to make it more representative
skin fold measurements
upper arm circumference
ketones in urine
nitrogen balance
high BMI =
higher risk of comorbidity
steps of the digestive process
ingestion propulson mechanical and chemical igestion apsorption defecation
what is propulsion
swallowing, oesphagus, peristalsis
pushing of food through the tract
histological features of the digestive tract
outside to in serosa muscularis exerna submucosa mucosal layer
what is the serosa
connective tissue and epithelial layer
cntinuous with outer
forms visceral layer
what is the muscularis externa
longitudinal muscle outer
circular muscle inner
sandwiched between the muscles is the nerves/plexus
what is the mucosal layer
layer of epithelial celss that protect the gut from abrastion
features of the mucosal layer
gastric gland here secretes enzyemes
enteroendocrine cells release hormomes
absrbs material into capillaries
what is the lamina propria
part of the mucosa
connective tissue
contains: capillaries, lymph vesles, lymphoid folicles
features of the submucosa
contains blood and lymph vessels
deep within is the sensory neurones: plezus
features of the muscularis exerna
smooth muslce is longlitudinal
circular muscle inside
can produce waves of contraction
myenteric plexus found here
what forms the ENS
network of neurones connected t the submucosal plexus
what two tyes of contraction can the muscularis externa help with
peristalsis or segmentation
what is the function of the mouth
reduced food sie
prepares it for swallowing
starting point for chemical breakdown
what is the tongue
skeletal muscle
upper surface is keratinised stratified squamous epthelium
bottom is non-keratinised mucus membrane
what is saliva pH
pH7
hypotonic
mainly water
what are the three salivary glands
paratoid
submanidubular
sublingual
what is the paratoid salivary gland
serous cells
mainly watery
contains enzymes, electrolytes and mucin
what are the submandibular and sublingual salivary glands
serous and mucosal cells
thicker saliva
functions of saliva
protection temp control acid neutralisation defence taste lubrication digestion enzymes
function of the osephagus
moves bolus to to stomach
delivery shute
features of osephagus
secretes mucus
strited muscle at top for voluntary functions
smooth at bottom for involuntary
what is peristalsis
propulsion of food along the tract
circular and longitudinal muscles have waves of contraction and relaxation moving the bolus
function of the stomach
strores the food
digests it chemically
digests it physically using grinding
what are rugae
foldings on the inner lining of the stomach
allow it to expand
anatomy of the stomach, name the parts
cardia
fundus
bod
pyloric region
which parts of the stomach expand?
fundus and body
what is the function of the pyloric region
chruning and empying flood
strong contractions needed here and thick mucles
describe the passage of food in the stomach
food in and stored mixed with water mucus and gastric secretory products grinding food into pylorus passes to duodenum
what affects the rate of stomach emptying
volume of food in stomach and its contents
more food means stronger contractions
what slows down digestion
but fat and acidic foods result it less stronger cntractions as these need longer to be digested and neutralised
what are gastric pits
the lead to gastric glands in the surface of the stomach
what is released from gastric glands
mucus
HCL
intrinsic factors
hormones
what are exocrine gland cell
secrete into ducts and the stomach lumen gastric juice
examples of exocine things secreted into he stomach
mucus
pepsinogen
HCL
intrinsic factors
endocrine
secrete into the blood system
pyloric regions
paracrine
secretions acting on neighbouring cels
histamine
stomatastin
what does a parietal cell release
HCL gastric juice and intrinsic factor
what do chief cells release
pepsinogen and gastric juice lipase
what do G cells release
hormone gastrin which stimulates gastric acid secretion
what do paracrine cells do
stimulate gastric juice secretion
what do D cells do
secrete stomatostain which inhibits gastric acid secretion
what secreted HCL
parietal cells
fundus and body
functions of HCL
breakdown of connective tissue and muscle fibres of ingested meat
activate pepsinogens
kills microorganisms
how is HCL made in the stomach?
CO2 transprted into parietal cells carbonic acid dissociates bicarbonate to bloo exchange for chloride into the lumen H into gastric gland in exchange for K K into blood blood more alkaline due to bicarbonate there H= with chloride forms HCL released into stomach
what is pepsinogen
made by chief cells
an enzyme in gastric cells
a group of proteolytic proenzymes
hydrolyses peptide bond
what is pepsin
protease
hydrolyses peptide bond within proteins
how does the stomach not digest itself
mucus is key
outer layer is physical protection
water layer acts as buffer for neutralisation
causes of gastric ulcers
coffee
nicotine
asprin
low bicarbonate
how does helicobacter pylori cause
swims to mucus layer, gets into epthelium enzyme urease released neutralises gastric acid, ammonia breaks down musuc layer pylori breaches layer inflamation of the cells
why is vitamin B12 needed?
maintanence of CNS and metabolism and maturation of RBC
lack can lead to anaemia
how is vitamin B12 absorbed
intrinsic factor
describe the process of vitami B12 beng absorbed
cobalmin is bound to proteins in food
acid pH ad pepsin release colbalamin from protein
gastric glands ecrete molecule to bind with this calalamn
gastric parietal cells secrete intrinsic factor
pancrease secretes proteases and alkaline
cobalamin is released after the degredation of the molecule
name the three stages of gastri secretion
cephalic
gastric
intestinal
what is the cephalic stage of digestion
CNS stimulated through sight and smell
signal the submucosa plexus to release Ach
mucus, pepsinogen and HCL secreted, gastrin also secreted
what is the gastric phase of digestion?
food into th stomach stretch receptors stimulated message to submucosal and myenetic plexus mucus, pepsinogen and HCL stimulated waves of contraction gastin stimulated too food broken down stomatastin produced things shut down ready for next stage
what happens in the intestinal stage of digestion
food moved to duodemun plexus inhibited stomach less stretched lesss grnding cell secretion inhibited chyme is acidic, CCK, secretein stimuated peristalis stopped everything slowed down and stopped
