digestive system Flashcards
major components of food
carbs,proteins, fats and water
what are the macronutrients
carbs,lipids, proteins
the proximate principles of food
micronutrients
protective principles of food,help to keep us away fom diseases
vitamins and minerals
macroelements
21 minerals(na,k,ca,s,p,mg,cl) essentional from humans
microelements
(Fe,I,Zn,mn,co,cu,mo) with 20 vitamins are required in very small amounts
what does the digestive system consist of
alimentary canal and the associated glands
where does the alimentary canal start and end
mouth(anterior) and anus(posterior) respectively
no. of teeth in the buccal cavity
32 permanent teeth
describe the human teeth
diphyodont, thecodont, heterodont,bunodont
arrangement of permanent teeth in each half of a jaw
2123(I C PM M)
arrangement of teeth in kids
2120
the monophyodont teeth in a human
premolars and last molar
in a 2-year-old, what teeth would be missing
premolars
the hardest substance of the human body and its role
enamel, helps in protecting the dentine and mastication of food
where are enamel secreted from
ameloblast cells of ectodermal origin
parts of a tooth
crown, neck, root
crown remains capped with hard enamel made of calcium phosphate and format chewing substance of the tooth
the crown and root both have the dentine, underlying the enamel. secreted by mesodermal odontoblast cells
inside the dentine a pulp cavity is present which has nerves and blood supply
what attaches the tooth to the socket
the periodontal ligament attaches the tooth to the bony socket
type of tooth the elephant’s tusk is
modified incisors
type of tooth the walrus tusk is
canine
type of teeth in birds, spiny anteaters, scaly anteater, some whales is
lol they have no teeth
teeth of sloth and armadillos
no enamel
classification of teeth on position
- acrodont: attached to the free surface or summit of the jaw bone
in fish, amphibians and reptiles - pleurodont: lateral surface of jaw ridge eg: fangs of snakes
3.thecodont: embedded in sockets and have well-developed roots(mammals and crocodiles)
classification of teeth on the arrangement of enamel and dentine
- bunodont: small blunt round cusp, humans
- lophodont: intricate folding of enamel and dentine and transverse ridges called lophos connect cusps, elephant
- selenodont: crescent-shaped enamel with soft dentine in sheep and cattle
- secodont: pointed cusps like in carnivores
the tongue description
voluntary muscle and glandular structure occupying the floor of the mouth
what is the tongue attached the mouth’s floor by
frenulum fold
parts of the tongue
inverted V-shaped furrow called sulcus terminalis which divides the upper surface of the tongue into the anterior oral part and posterior pharyngeal part
the different PAPILLAE of tongue
- filiform: smallest most abundant and no taste buds
- fungiform: appear as red dots on the tongue and no taste buds
- foliate :absent in man
- circumvallate: largest in size and knob-like and have taste buds
the different taste buds
tip:sweet
tips and sides:salt
sides:sour
base:bitter
no taste buds for spice,just pain receptors
tongue of dogs
sweat glands
pharynx
oral cavity leads to pharynx,commaon passage for food and air
tonsils
lymphoid tissues of pharynx
the different tissues of tonsil
nasopharyngeal tonsils tubal tonsils palatine tonsils lingual tonsils they are arranged in a ring like manner called waldeyer's ring
oesophagus
the pharynx leads to oesophagus, a tube that is very resistant and connects to the stomach
opening of the windpipe
glottis
flap covering the glottis
epiglottis
the flap that stops food from entering the nasal cavity while swallowing
uvula
the sphincter between the stomach and oesophagus
gastro-oesophageal sphincter
what is the stomach
a j shaped sac in the upper left corner of the abdominal cavity
parts of the stomach
the fundus, cardiac(where the oesophagus enters) and the pyloric region
stomach of ruminants
compound stomach, 4 chambers
the chambers of compound stomach
- rumen (largest):for the storage of food
- reticulum
- omasum(absent in camel and deer and water cells eject from rumen)
- abomasum: the true stomach secreting gastric juices
rumen and reticulum harbour large amount of anaerobic bacteria digesting cellulose into fatty acids by fermentation like rumenococcus and protozoans and cellulolytic bacteria.
parts of the small intestine
duodenum(C shaped)
Jejunum(long and coiled middle portion)
ileum(highly coiled longest portion
sphincter between stomach and small intestine
pyloric
walls of the intestine
thin layers of longitudinal and circular muscles
plicae circulares
folds of the mucosa of the small intestine
(folds of kerching or valvulae conniventes)
the mucosa also has columnar epithelial cells modified into villi towards the inner side which further have microvilli
crypts of lieberkuhn
interstitial cells(b/w villi) of the small intestine they have epithelial cells secreting mucus, paneth cells secreting enzymes and argentaffin cells secreting hormones in the duodenum brunner's glands are also present in the submucosa secreting mucus the lymphoid tissues present through out the small intestine and aggregated in the ileum as peyer's patches
the different parts of the large intestine
- caecum:small blind sac which hosts some symbiotic microorganisms. it has the vermiform appendix at one end and opens into the colon at the other
2.colon: ascending, transverse and descending
ascending is the smallest and lacks mesentery
descending colon opens into the rectum
3.rectum: it is the last part of the alimentary canal and storage site for faecal matter. it opens outside through the anus.
walls of the colon
- has a sac like haustra
- 3 bands of longitudinal muscles called taenia coli
- the surface has a presence of fat filled projections called epiploic appendages
largest intesines in
herbivores
histology of alimentary canal
mainly four layers
- serosa: thin mesothelium with some connective tissues. it is absent in the upper part of the oesophagus
- muscularis layer: smooth muscles. outer longitudinal and inner circular. an oblique muscle is found in the stomach b/w these two
- sub-mucosa:loose connective tissues,containing nerves,blood and lymph vessels. In the duodenum, glands are also present
- mucosa: innermost layer with irregular folds called rugae in the stomach and fingerlike projection villi in small intestine.
what does mucosal epithelium have
goblet cells releasing mucus
mucosa of stomach
gastric glands
the two categories of plexus in the alimentary canal
myentric plexus/plexus of auerbach
meissner plexus/submucosal plexus
myentric plexus/plexus of auerbach
fibres from both autonomic divisions
b/w longitudinal and circular muscles of the muscular coat
controls peristalsis
meissner plexus/submucosal plexus
between the muscular coat and mucosa
secretion of different kinds of digestive glands.
function of villi
increase the surface area for absorption and keep the food longer in the small intestine for maximum absorption.
the digestive associated glands
salivary glands
pancreas
liver
the three pairs of salivary glands
parotids: cheek, largest salivary glands, open through stensons duct
sub-maxillary/sub-mandibular: lower jaw, opens through Wharton’s duct
sub-linguals: below the tongue and are the smallest opens through rivinus duct
saliva
1.5L,6.7 pH
the enzymes of saliva
salivary amylase(ptyalin) lysozyme
effect of the nervous system on the salivary glands
parasympathetic: stimulated to secrete
sympathetic: dry mouth, no saliva
what do salivary amylase need to be activated
cl- ions
mumps
infection of salivary glands, mainly paratoid
the largest gland in the body
liver
origin of the liver
endoderm
weight of the liver
1.2 to 1.5 kg
position of the liver
in the abdominal cavity,just below the diaphragram two lobes(right and left)
structural and functional units of the liver
hepatic lobules
contains hepatic cells arranged in form of cords
Glisson’s capsule
connective tissue sheath covering each lobule
its the characteristic feature of the mammalian liver
kupffer cells
phagocytic cells eating worn out RBC, WBC, bacteria
the gall bladder is absent in
adult lamprey,grain-eating birds, rat, whale, all members of Perissodactyla and some Artiodactyla
where is bile secreted and stored till concentrated
hepatic cells of the liver and stored in the gall bladder
the capacity of gall bladder
30 to 50ml
ducts from the liver to gall bladder
hepatic ducts
ducts of gall bladder
cystic ducts
cystic ducts and hepatic ducts
common bile duct
the bile duct and pancreatic duct opening into the duodenum
common hepatopancreatic duct
common hepatopancreatic duct sphincter
sphincter of oddi
a heterocrine gland
pancreas, from endoderm
position of the pancreas
elongated organ situated between the limbs of the c shaped duodenum
the exocrine portion of the pancreas and its secretion
acini
alkaline solution-pancreatic juice
ducts of the pancreas
- duct of Santorini( accessory non-functional), opening directly into the duodenum
- duct of wirsung(functional and combines with bile duct to form the common hepatopancreatic duct
digestion of food in the mouth
mastication of food
lubricating the food and with the tongue making it into a round ball called the bolus
the saliva contains electrolytes like na,k, cl,hco3.lysozyme and PTYALIN
ptyalin converts 30% of starch into maltose
where all is salivary amylase missing
in most mammals like cows buffalos and carnivores like tigers and lions
but present in pigs
gastric glands in the stomach
mucus neck cells secreting mucus and hco3
peptic or chief cells secreting proenzyme pepsinogen
parietal or oxyntic cells which secrete HCl and intrinsic factor(factor important for the absorption of vitamin B12 in intestines.)
no secretion of HCl in stomach
achlorhydria
digestion in stomach
it stores the food for 4-5 hours
the proenzyme pepsinogen gets converted to pepsin with exposure to HCl
it digests proteins to proteases and peptones
HCl provides an acidic environment of 1.8 which converts ferric to ferrous ions which help make the absorption of iron possible
rennin a proteolytic enzyme found in infants which helps in digestion of milk proteins
lipases are also secreted
what is digested material leaving the stomach
chyme
the pancreatic juice contains
inactive enzymes like trypsinogen, chymotrypsinogen, procarboxypeptidases, amylases, lipases, nucleases
what does bile contain
no enzymes bile pigments: bilirubin and biliverdin bile salts: sodium bicarb, sodium glycocholate, sodium taurocholate cholesterol phospholipids ACTIVATES LIPASES AND EMULSIFIES FATS
intestinal juices/succus entericus
secretions of the mucosa of the intestine(crypts of lieberkuhn) along with secretions of goblet cells.
maltases,sucrases,lactases, dipeptidases, lipases, nucleosidases, enterokinases, erepsin
crypts of lieberkuhn provides a pH of 7.6 for sufficient enzyme activity
digestion in the small intestine(pancreatic juice)
enterokinases activate inactive trypsinogen to active trypsin which then activates all the other pancreatic enzymes
trypsin converts proteins and proteoses to peptones, peptides
carboxypeptidases convert peptides to dipeptides
chymotrypsin hydrolysis casein into para caseinate and then coagulates to form calcium para caseinate.
amylopsin(amylase) converts carbohydrates and starch into disaccharides and maltose
lipases(steapsin) converts fats to diglycerides and monoglycerides
nucleases converts RNA DNA to nucleotides
digestion by the intestinal juice
erepsin converts peptides to dipeptides and amino acids
dipeptidases converts dipeptides to amino acids
lipases convert fats and monoglycerides, diglycerides to glycerol and fatty acids
maltase acts on maltose to give 2 glucose
lactase on lactose to give glucose and galactose
sucrase on sucrose to give glucose and fructose
nucleotidases on nucleotides to give nucleoside
nucleosidases on nucleosides yo give free bases and sugar
trypsin in predatory animals
hydrolyse fibrinogen of blood into fibrin to form coagulation
why can’t old people digest milk but yes to curd
they don’t have enough lactase to digest the lactose. this causes fermentation of lactose and hence gases and diarrhoea
in curd, the lactose is converted to lactic acid, therefore, no lactase required to digest it
galactosemia
absence of enzyme uridyl transferase
as a result galactose will accumulate leading to mental retardation
can be prevented by giving them milk free diet
part of the small intestine where the breakdown occurs
duodenum
parts where absorption takes place in the small intestine
a bit in jejunum an in the ileum
does digestion occur in the large intestine
no
where does absorption of digested food take place
small intestine
by what methods does absorption take place
active, passive or facilitated transport
what all is absorbed into the blood by simple diffusion
glucose,amino acids, electrolytes like chloride ions
what is absorbed by facilitated transport
fructose, amino acids are absorbed with the help of carrier proteins and carrier ions like Na+
what all is absorbed by active transport
amino acids, monosaccharides like glucose, electrolytes like Na+
what all are insoluble to be absorbed by the blood
fatty acids and glycerol, as they are insoluble in water
how are fatty acids and glycerol absorbed
they are first incorporated into small droplets called micelles which then move into the intestinal mucosa. they are formed into small protein-coated fat globules
called chylomicrons which are then transported into the lymph vessels(lacteals of villi) they are absorbed into a fluid called chyle
they then are released into the blood stream
what all is absorbed in the mouth
drugs coming in contact with the mucosa of the mouth and lower side of the tongue
eg: cardio drugs for immediate effect
absorption in stomach
water, simple sugars, alcohol
absorption in the large intestine
water, some drugs and minerals
role of the large intestine
absorption of water
secretion of mucus which helps to adhere waste particles together
what prevents the faecal matter from backwards entering the small intestine
ileo-caecal valve
what temporary stores faeces
rectum
what happens when eating raw fish
beriberi
the fish has an enzyme which breaks down thiamine which then further causes paralysis due to the deficiency of Vit B1
what happens when drinking seawater
the seawater contains magnesium ions.
these ions are absorbed very slowly and the osmotic effect of these ions causes water to not be absorbed into the intestinal lumen
on the contrary, the ions absorb water from the blood
there is a large loss of water and fluidity of faeces
how much chyme passes through the large intestine on a daily basis
1500 ml
what does the colon do
absorbs most of the water electrolytes and ions by the active pumping of sodium and water by osmosis from the chyme
excretion of excess salts from the blood
population of E coli bacteria which produces vit B12. K,Thiamine and Ribaflavin
what produces the brown colour in poop
breakdown of bile pigments to stercobilin pigment
the foul smell of poop
microbial gases and skatole(3-methyl-indole)
dark green mucaliganious material in the intestine of a full-term foetus
meconium
due to swallowed amniotic fluid and residues of excretory products from the intestinal mucosa
what stimulates the secretion of saliva
sight smell or presence of food in the oral cavity
by which nervous system is the muscular wall of alimentary canal stimulated
central nervous system
strongest lipase
steapsin
cholagogues
substances that cause the contraction of gall bladder
the capacity of a human stomach
1.5-1.7 L
