Physiology Flashcards
functions of the digestive system
absorption
digestion
secretion
motility
where do nutrients primarily enter the circulatory system
small intestine
how many salivary glands are there
3 pairs (6)
what occurs in the mouth
foodstuffs broken down by chewing: saliva added as lubricant
what is oesophagus
muscular conduit between stomach and mouth
what happens in stomach
- digestion of proteins:
- foodstuffs reduced to liquid form
- storage
- sterilisation
what can be found in the pancreas
digestive enzymes for digestion of fats, carbohydrates and proteins
what can be found in liver
bile salts for digestion/ absorption of fats in the small intestine
what happens in large intestine
- water absorption,
- bacterial fermentation
- formation of faeces
what are essential for fat digestion
bile salts in the liver
how long from oesophagus to rectum
8m ish
4 distinctive layers of alimentary canal
- mucosa
- submucosa
- muscularis externa
- serosa
2 layers of musculaisr externa
longitudinal
circular
function of muscularis externa
provide motility
type of epithelium in mouth, oesophagus and anal canal
stratified squamous
type of epithelium in stomach, small and large intestine
simple columnar
functions (3) of epithelium in GI tract
- barrier separating lumen of alimentary canal from body
- synthesis and secretion of digestive enzymes, hormones, mucus
- absorbs products of digestion
components of mucosa
- epithelium
- lamina propria
- muscularis mucosae
what is lamina propria
loose connective tissue (glands, blood/lymph vessels)
what is muscularis mucosae
thin, smooth muscle layer
what is submucosa
thick, irregular connective tissue
function of submucosa
support mucosa
what is contained in submucosa
neurons, blood and lymphatic vessels
where are submucosal glands found
- oesophagus
- duodenum
what is the function of neurones in submucosa
form extensive network - the submucosal plexus (parasympathetic)
what is serosa/ adventitia
connective tissue outer layer of alimentary canal
function of serosa outside peritoneal cavity
adventitia attaches oesophagus and rectum to surrounding structures
function of serosa inside peritoneal cavity
serosa surrounds stomach, small intestine and large intestine
what is muscularis externa composed of
- two thick layers of muscle
Inner = circular Outer = longitudinal
where is myenteric plexus located
between circular and longitudinal layers of muscularis externa
What makes up the enteric nervous system?
submucosal and myenteric plexuses
function of enteric nervous system
indépendant control of gut function
what enables independent control of gut function
enteric nervous system
what is meant by a long reflex in alimentary system
gut - CNS
what is meant by a short reflex in alimentary system
just in gut (gut control)
Parasympathetic nerve innervation of alimentary system
vagus nerve
sympathetic nerve innervation of alimentary system
splanchnic nerve
effect of parasympathetic nervous system
stimulatory
increases secretion and motility
effect of sympathetic nervous system
inhibitory (reduces secretion and motility)
exception to stimulatory/ inhibitory rule for alimentary tract
salivation (no effect)
autonomic control
automatic control
you cannot influence it
long vs short reflexes in the gut
long: goes to CNS
short: remains in the gut
foregut contents
- abdominal part of oesophagus
- liver
- pancreas
- spleen
- upper part of duodenum
- stomach
- gall bladder
midgut contents
- ileum
- jeudenum
- lower part of duodenum
- large intestine
- proximal 2/3 transverse colon
- appendix
- ascending colon
- caecum
hindgut structures
- distal 1/3 transverse colon
- descening colon
- sigmoid colon
- rectum
- upper anal canal
- urogenital sinus
blood supply to foregut
coeliac trunk
blood supply to midgut
superior mesenteric artery
blood supply to hindgut
inferior mesenteric artery
venous drainage of stomach
gastric veins
venous drainage of pancreas
splenic veins
venous drainage of midgut structures:
- small intestine
- caecum
- ascending colon
- transverse colon
superior mesenteric vein
venous drainage of hindgut structures:
- descending colon
- sigmoid colon
- rectum
inferior mesenteric vein
name the components of the hepatic portal vein:
- splenic vein
- inferior mesenteric artery
- superior mesenteric artery
- gastric veins
where does blood go after leaving GI organs (pathway)
- portal vein tributaries
- hepatic portal vein (goes through liver)
- hepatic vein
- inferior vena cava
what organ does all blood go through before leaving the gut
liver
purpose of all blood going to the liver after leaving the gut
liver screens/ purifies blood to prevent any toxins absorbed from food from entering the circulatory system
principle dietary constituents
- carbohydrates
- protein
- fat
- vitamins
- minerals
- water
monosaccharide examples:
Hexose sugars (6c)
- glucose
- galactose
- fructose
description disaccharides
two monosaccharides linked together by glycosidic bonds
how are disaccharides broken down
brush border enzymes in small intestine break them down to monosaccharides
what is lactose broken down to
glucose and galactose
what breaks down lactose
lactase
what is sucrose broken down to
glucose and fructose
what breaks down sucrose
sucrase
what is maltose broken down to
glucose x2
what breaks maltose down
maltase
2 forms of starch
- a-amylose
- amylopectin
what is a-amylose
glucose linked in straight chains
what is amylopectin
highly branched glucose chains
what type of bonds link glucose monomers in starch
a-1,4-glycosidic bonds
what type of reaction breaks down starch
hydrolyse
what enzyme is used to break down starch
amylase
why can vertebrates not break down cellulose by themselves
brecause they/ we don’t have the enzyme cellulase which is required to break down B-1,4-glycosidic bonds
what is celluloses function in humans
dietary fibre
glycogen function
animal storage form of glucose
glycogen structure
glucose monomers linked by a a-1,4-glycosidic bonds
what are people who are lactose intolerant not have
lactase enzyme
texture of villi in small intestine
velvety when it doesn’t have mucus
2 membrane types of epithelium
- apical (facing outside e.g. vein)
- basolateral (facing inside e.g. other cells)
what does a brush border look like
bart simpsons hair
transcellular pathway
goes through the cell
paracellular pathway
- goes between cells through tight junctions
how many transporter proteins are needed to pass a molecule through a cell
at least 2 - one at apical and one at basolateral membranes respectively
what transporter protein is used for getting glucose into a cell
SGLT1
what needs to be present for getting glucose into a cell
Na, Glucose, SGLT1
what transporter protein gets glucose out of a cell (down the concentration gradient)
GLUT-2
what is a normalise blood glucose
5 mmol/l
what transporter protein gets fructose into a cell
GLUT-5
what transporter protein gets fructose out of a cell
GLUT-2
why does fructose transport into a cell not require any energy?
because there is no blood fructose concentration
what other molecules are involved in fructose transportation
NONE ahahahah fooled ya ;)
who is awesome
you are
what is a protein
polymer of amino acids linked together by peptide bonds
what are described as natures lego and why
proteins
infinitely variable
what are enzymes that hydrolyse peptide bonds and reduce proteins/ peptides to amino acids called?
- proteases
- peptidases
function of proteases and peptidases
break down proteins and peptides to form amino acids
endopeptidases
breaks down internal amino acids
exopeptidase
breaks down terminal end of amino acid (snipping at the end making it 1 shorter everytime)
aminopeptidases
work on amino end of protein
carboxypeptideases
work on carboxyl end of protein
how do most amino acids enter a cell
the same way as glucose; with a transporter and Na
how do amino acids leave a cell
using specific transporters to cross basolateral membrane
PepT1
protein transporter that can carry virtually any di/tripeptides into a cell using H
where does H come for transporting amino acids across apical membranes into a cell
acid microclimate around the surface
what form are almost all ingested fats found in
triglycerol
what enzyme digests fats in the small intestine
pancreatic lipase
definition of a ‘lipase’
water-soluble enzyme
emulsification
dividing large lipid droplets into smaller droplets
what is required for emulsification of fats to take place?
- mechanical disruption
- emulsifying agent
ampiphatic
has polar and non polar components (like phospholipid membrane)
how does mechanical disruption of fats in the stomach take place
muscularis externa contraction grinds and mixes lumen contents.
function of micelles
‘vehicles’ for emulsion droplets to get to the cell surface for absorption
components of a micelle
bile salt + monoglycerides + fatty acids + phospholipids
fate of micelles when they have released the fatty acid inside onto the surface of the cell
they are reused, going back to pick up more fatty acids to transport
how does micelle release fatty acid at cell surface
micelle destabilises in the extreme acidic microclimate immediate to the cell, releasing the fatty acids onto cell surface
what happens to fatty acids when they enter the cell
- they enter the smooth endoplasmic reticulum,
- where they are resythesised by enzymes to for triacylglycerols,
- emulsified with amphipathic protein found in sER
- processed through Golgi apparatus
- exotysed into extracellular fluid at serial membrane
difference smooth and rough endoplasmic reticulum
smooth - no ribosomes
rough - ribosomes
chylomicron
extracellular fat droplet
extracellular fat droplet
chylomicron
where do chylomicrons go
pass into lacteals between epithelial cells (cannot pass through capillary basement membrane0
where does fat go after leaving a cell
into lymphatic system, then circulatory system via thoracic duct/ vena cava
what are the 2 classes of vitamins
- fat soluble
- water soluble
which vitamins are fat soluble
A,D,E,K
which vitamins are water soluble
B, C, Folic Acid
how are fat soluble vitamins absorbed
same pathway as fat
how are water soluble vitamins absorbed
- passive diffusion
or - carrier mediated transport (like micelle for fat)
how is vitamin B12 absorbed
it binds to an intrinsic factor in the stomach to form complex which is absorbed via a specific transport mechanism in the distal ileum
what can occur as a result of B12 deficiency
pernicious anaemia
what is pernicious anaemia?
failure of red blood cell maturation
what causes pernicious anaemia?
B12 deficiency
how much of daily iron intake is absorbed into the blood?
10%
how is iron stored
incorporated into ferritin
what does iron in blood bind to
transferrin
what is the only nutrient that has controlled absorption?
iron