Digestive system Flashcards
Type of cells in salivary gland
- Acinar cells (volume)
- duct cells (composition of saliva)
parts of stomach
- cardia
- fundus
- body
- antrum
- pyloric
parts of small intestine
- duodenum
- jejunum
- ileum
secretion of pancreatic juices takes place in
duodenum
parts of large intestine
- ascending colon
- transverse colon
- descending colon
part where small intestine opens in large intestine
caecum
sphincter between esophagus and stomach
gastroesophageal sphincter
explain diphyodont
condition where milk teeth are replaced by permanent teeth
explain thecodont
teeth embedded in the socket of jaw
types of teeth with their function
4 types of teeth (heterodont)
1. incisor ( front, for cutting)
2. canine (sharp pointed teeth)
3. pre-molar ( known as cheap teeth, used for grinding and crushing)
4. molar (same as above)
teeth formula
2123 - adult
2103 - child (premolar absent)
types of salivary gland
- parotid (largest gland, 20% contribute, 1 in pair)
- submandibular (starts 4m lower jaw to 2nd molar, 70% contribute)
- sublingual (below tongue, 5% contribute)
saliva pH
6.7 (acidic)
amount of saliva secreted everyday
1 - 1.5 liters
components present in saliva
- mucus (s Ig A) mucin protein (protect the lining of stomach)
- chloride ion (initiates fluid secretion process)
- lysozyme (antibacterial)
- lactoferrin (proline rich, protect teeth, binds with Fe, bacteriostatic)
- Ptyalin (also known as salivary alpha amylase)
- lingual lipase
about ptyalin
- breaks alpha 1,4 bond of carbohydrate
eg: starch, glycogen - But can’t break alpha 1,6 bond of carbohydrate
eg: sucrose - needs chloride ion , ph 6.5 for proper functioning
movement of food in gut is known as
peristaltic movement, where both longitudinal and circular muscles moves together to move food
histology of gut
- serosa (outermost)
- muscularis
- submucosa
- mucosa (innermost)
- lumen
sphincter between pyloric and duodenum
pyloric sphincter
components of mucosa
- epithelial cells
- basement membrane
- lamina propria (connective tissue where blood vessels are present)
components of submucosa
Meissner’s nerve plexus (controls glandular secretions, alters electrolyte and water transport, and regulates local blood flow)
components of muscularis
- circular muscles
- longitudinal muscles
- myenteric plexus/ Auerbach’s plexus (responsible for the peristaltic movement of the bowels)
cells present in fundus of stomach
mucus cells/ goblet cells (secrets mucus)
cells present in the ‘body’ of stomach
- oxyntic cells
- chief cells/parietal cells
- G cells/ goblet cells (present very less)
cells present in the antrum of stomach
- G cells/goblet cells (releases gastrin) (more in no.)
- oxyntic cells and chief cells present less in no.
secretion of oxyntic cell and chief cell
oxyntic cell - hcl + intrinsic factor
chief cell - pepsinogen (inactive form of enzyme)
function of intrinsic factor
helps in absorption of vitamin B-12.
Why is Vit B -12 required?
- helps in RBC maturation
- helps in lymphocyte maturation
function of HCl
- Helps in the absorption of Fe
- kills bacteria
- provides acidic medium for the activation of enzymes
where are gastric glands located
in the lining of the stomach
what are ECLs?
- ECL are enterochromaffin like cells present in the form of patches in the g cells of Gastric gland
- neuroendocrine cells
- releases Histamine upon the action of gastrin which is released from g cells
inhibitors of proton pump
omeprazole
pantoprazole
explain the release of histamine in detail
- gastrin binds to the “G protein coupled receptor”
- which releases adenyl cyclase
- which releases cAMP
- Which in turn releases protein kinase A (PKA)
- which releases histamine
what is the role of histamine released in humans
regulates the acid secretion by oxyntic cells in the stomach
explain the process of acid secretion controlled by histamine
- histamine released from ECL binds to H2R (histamine receptor)
- which leads to the release of adenyl cyclase to cAMP to PKA
- This leads to the OPENING of proton pump and conversion of H2O and CO2 into H2CO3 then to hydrogen ion and hydrogen carbonate ion in the presence of carbonic anhydrase.
- hydrogen ion so released leaves the chief cell and potassium ion enters in its place through proton pump which were opened
- HCO3- ion leaves the cell via band III and chloride ion enters in its place.
- Cl - ion leaves the chief cell and forms HCl in the lumen
what is band 3
major integral protein which helps in the ion transport and maintenance of protein-protein interactions.
pH of empty stomach and pH of stomach when full
empty - pH 5
Full - 1.5
reasons for ulcers in stomach
- barrier destroy
- alcohol consumption
- NSID (non steroidal inflammatory drug)
- infection (helicobacter pylori)
layers of barriers of stomach
- Mucus (mucin protein)
- Trefoil peptide
- H2CO3 (weak acid)
lengths of parts of small intestine in their descending order
ileum> jejunum>Duodenum
cells found in duodenum in the crypts of Lieberkühn
i cell (secrets cholecystokinin/ CCK, Pancreozymine (Pz) ]
S cell - (secretin)
Paneth cells (secrets defensin, lysozyme; both of which are antimicrobial peptide)
Brunner’s gland - mucus rich in bicarbonate and
enterokinase (enzyme)
name the component present in ileum and its function
Payer’s Patches (which secrets B lymphocyte, T lymphocyte and phagocytic cells)
bile is released from which duct
hepatopancreatic duct (common passage for left and right lobe of liver)
cystic duct brings bile secretion from which organ?
gall bladder
components of bile
- cholesterol
- Bile pigments
- bile salts
- enzymes absent
- pale yellow in colour
- 500 ml production in a day
bile pigments
bilirubin and biliverdin
full form of GERD
Gastroesophageal reflux disorder (backward movement of food from stomach to esophagus)
examples of bile salts
taurocholic acid and Glycocholic acid and taurochenodeoxycholic acid and glycochenodeoxycholic acid
facts about bile
continuously formed, excess bile stored in gall bladder, bile from liver contains 30% water whereas bile from gall bladder contains 10% water.
functions at pH 8
Functions of bile
- Reduces surface tension
- increases surface area for fat absorption
- Helps in emulsification of fat
- Amphiphatic in nature.
secretion of pancreatic juice in a day and pH
1-1.5 liters a day at pH 8
enzymes of pancreas
- pancreatic alpha amylase
- proteases
- Lipases
- DNAse
- RNAse
types of proteases present in pancreatic juice
- trypsinogen
- chymotrypsinogen
- pro- elastase
- Procarboxypeptidase
All the proteases secreted are present in inactive form called zymogens
action on chyme after being released from stomach
- acidic food enters duodenum
- acidity sensed by I cells
- activates CCK and Pz (at low conc.) from Brunner’s gland
- which in turn activates gall bladder via IP3 (2ndry messenger) and S cells
- which activates bile (pH 8)
- S cells secretes secretin
- secretin activates pancreas via cAMP (2 messenger)
- Pancreas activates f cells and release bicarbonates
condition when CCK AND PZ are released more in amount
- CCK AND PZ stimulates pancreas
- which secrets pancreatic juice
enzyme which helps in the digestion of collagen
pepsin from chief cells
collagen is a major constituent of meat
action of trypsin
act on the basic amino acid
action of Chymotrypsin
act on the C terminal of aromatic amino acid
action of elastase
act on the C terminal of aliphatic amino acid
action of carboxypeptidase
carboxypeptidase A acts on the aromatic amino acid
carboxypeptidase B acts on the Basic amino acid
how is trypsin activated?
- enterokinase from crypts of Lieberkühn is released
- acts on trypsinogen
- Active form trypsin is generated
which enzyme activates all the inactive zymogens?
trypsin
who all does the digestion of carbohydrate
- salivary alpha amylase
- pancreatic secretion
- Intestinal enzyme (memrane bound enzymes)
After digestion of glycogen and starch by pancreatic alpha amylase converts into
In duodenum
1. sucrose
2. Maltose
3. Dextrin
4. Lactose
name of intestinal enzymes which acts on the chyme in duodenum
- Sucrase
- Maltase
- Alpha Dextrinase
- Lactase
final products after action of intestinal enzymes
- sucrase into glucose and fructose
- Maltase into glucose
- Dextrinase into glucose
- Lactase into Glucose and galactose
where does digestion of proteins occurs?
jejunum
enzyme that acts on proteins and peptones
intestinal enzyme
after digestion proteins and peptones are converted into what
proteins into amino acid and peptones into dipeptides and tripeptides
where does maximum digestion takes place?
Duodenum
where does maximum Absorption takes place?
Jejunum
Where does digestion of fats takes place?
duodenum
triglycerides of fats are converted into what
1 monoglycerides and 2 molecules of fatty acid
name of the enzyme that acts on the fats
Lipases
Where does the absorption of different components of food takes place
enterocytes of intestine which is supplied by villi which is then followed by microvilli present on the apical surface of jejunum
What is SGLT 2
Sodium Glucose Co transporter 2 is a secondary active transporter which transports sodium and glucose or galactose
explain the absorption of carbohydrate
sodium glucose and galactose are transported by SGLT 2 and fructose is transported by GLUT 5 from lumen of intestine into basal side of cell i.e. into the blood circulation.
fructose is transported by facilitated diffusion whereas SGLT is an active transporter
fructose comes in by GLUT 5 and goes by GLUT 2 into blood circulation
1 SGLT 2 can transport how many molecules
1 glucose
1 galactose
2 sodium ions
what happen to sodium transported by SGLT 2
3 sodium ions move out and 2 potassium ions enter via Na/K ATPase
which carbohydrate will transport in the absence of energy
fructose (transported by facilitated diffusion)
ion channels through which protein uptake occurs in enterocytes
- sodium amino acid co transporter ( 5 types) [ transport Na+ and amino acid]
- Chlorine amino acid co transporter (2 types) [transport chlorine and amino acid]
- NHE (sodium hydrogen exchange) [ transport 1 Na+ in exchange of 1 H+]
- Pept-1 (symporter) [ transports H+, Di, tri peptide]
Action on Di and tri peptide
Di and Tri peptide are acted upon by dipeptidase and tri peptidase converting them into amino acid
These amino acid are transported out from the enterocytes by facilitated diffusion
