nutrition in humans Flashcards
ingestion
food is taken into the body
digestion
large, insoluble, complex food molecules are broken down into simpler smaller soluble molecules that can be absorbed into the body cells
assimilation
some of the absorbed food are converted into new protoplasm and to release energy
abosrption
digested food substances are absorbed into the body cells
egestion
removal of undigested matter from body
mouth processes
phys digestion: chewing-> phys breaks down food particles into smaller particles -> increase SA to volume ratio of particles for faster rate of chemical digestion
chemi digestion: fod is chemically digested through action of salivary amylase -> hydrolyses starch into maltose
salivary amylase in saliva is secreted by slivary glands
oesophagus func
transport food particles from mouth to stomach cia peristalsis
peristalsis def + muscles involved
def: rhythmic wavelike contractions of muscles of gut
circular muscles: inner wall
longitudeinal muscles: outer wall
circ mus contract, long mus relax, lumen of gut narrow, gut lobnger, food pushed froward
circ mus relax, long mus con, lumen of gut wider, gut shorter, food enters
stomach process
when bolus enters stomach, gastric glands on walls of stomach is stimulated to secrete gastric juices
what do gastric juice scontain
HCL and pepsin
func of HCL (4)
- converts inactive pepsinogen into active pepsin
- kills hamrful microorganisms in food
- provides optimum PH for actin of enzymes
- denatures salivary amylase
func of pepsin
chemically digests proteins by hydrolysis into polypeptide (partial digestion)
what happens after everything in stomach
liquefied food is called chyme after partial dogestiom
pancreas
- produces and secretes pancreatic juices itno duodenum via pancreatic duct
- a organ or gland
pancreatic juices
- pancreatic amylase (starch -> maltose)
- pancreatic lipase (fats -> fatty acids and glycerol)
- pancreatic protease (protein -> polypeptides)
liver and gall bladder
- liver produces bile
- bile is stored in gall bladder
- bile is secreted into duodenum via bile duct by gall bladder
characteristics of bile
greenish yellow liquid
alkaline
not a enzyme -> not affected by temp or PH
contains bile pigments and salts
func of bile
- creates optimal alkaline environemtn for action of enzymes
- emulsifies fats into tiny fat droplets that increase surface area to volume ratio of fats for faster rate of digestion of fats by hydrolysis into fatty acids and glycerol by lipase
- reduces acidity of chyme from stomach
digestion in teh intestine
Intestinal maltase
Maltose -> glucose
Pancreatic amylase
Starch -> maltose
Intestinal sucrase, lactase
Digestion of disaccharides
Intestinal protease
Polypeptides -> amino acids
Pancreatic protease
Protein -> polypeptides
Intestinal lipase
Fats -> fatty acids + glycerol
Pancreatic lipase
Fats -> fatty acids + glycerol
adaptations o fSI
- Inner walls of SI is highly folded
Numerous villi present on the folds
Numerous microvilli present on epithelial cells of villi
Increase SA of SI for faster rate of absorption of digested nutrients - Epithelium of villus is one cell thick
Decrease diffusion distance between lumen of small intestine and capillary/lacteal in villus
Faster absorption of digested nutrients from lumen of SI into villus - Dense blood capillary network in villus
To continuously transport digested nutrients away from SI quickly
To maintain steep concentration gradient of digested nutrients between lumen of SI and blood capillaries in villus
Faster absorption of digested nutrients into villi of SI - long
Aloow for sufficient time to absorb the digested nutrients into the villus - Epithelial cells have numerous mitochondria
increase rate of respiration to release more energy for active transport of nutrients into the villi
duodenum
Where juices are stimulated to be secreted into once bolus enters SI
Has more epithelial cells in duodenum walls than ileum and jejunum bc digestion mainly occurs in the SI hence the need for intestinal juices to be produced by epithelial cells in walls of the duodenum
Lower concentration of villi than in ileum and jejunum bc absorption mainly occurs in jejunum and ileum
ileum
- highly coiled
- where most of the absorption of nutrients occur
large intestine
- remianing matter enter - cellulose, bacteria, dead cells lining the intestine walls, water
- reabsorption of water back into bloodstream
- undigested matter stored in rectum
- absorption of ions and vitamins
rectum and anus
when rectum full, muscles of rectal wall contract to expel the faeces out of body
transpoartation of amino acids and glucose out of SI
- by diffusion and active transport
- absrobed into the capillary of villus
- blood capillaries form the hepatic portal vein
- carries glucose and aa to liver
transportstio of fats out of SI
- diffuse
- into epithelium
- recombien to form minute fat droplets
- enter the lacteal
- lacteal form larger lymphatic blood vessel
- rech thoracic duct
- fat globules are released into the bloodstream
assimilation of glucose
- oxidiesed during cellular respiration to release energy
- excess glucose -> return to the liver -> converted into fats
assimilatiom of fats
- sufficient glucose -> protoplasm
- insufficient glucose -> broken down to provode energy
- excess fats -> stored in adipose tissues as shocker absorbers around vital organs
assimilation of amino acids
- protoplasm for grwotha nd repair of worn out parts of body
- form proteins
- synthetise of enzymes and some hormones
liver functions (6)
- regulation of BGC
- when BGC xxx, islets of pancreas are stimulated to release glucagon/insulin that stimulates the liver cells to convert xxx to xxx, bringing BGC back to norm - deamination of excess aa
- amino group in aa is broken down and ammonia is formed
- ammonia is converted into urea that leaves body in teh form of urine
- carbon residue is cobverted into glucose and oxidised to release energy
- converted into glycogne if in excess - detoxification
- alcohol is broken down into acetaldehyde by alcohol dehydrogenase
- acetaldehyde is further broken down into acetic acid by alcohol dehydrogenase
- acetic acid is further broken down to releasee energy or converted into glucose for respirationto release energy for cellular activities - production of bile
- provides optimal alkaline envt fr action of enzymes in SI
- emulsifies fats into smaller fat droplets to increase SA to vol ratio such that digestion of fats by hydrolysis to fatty acids and glycerol by lipase increases - protein synthesis
- converts aa into fibrinogen or prothrombin - storage of iron/breaking down of rbc
- worn out rbc is destroyed in spleen
- haemoglobin is released
- haemolglobin in broken down by liver and iron is released
iron stored in liver
bile pigments are also produced
effects of excessive alcohol consumption (3)
- digestive system issues
- stimulatesacid secretion in stomach -> increased risk of getting gastric ulcers
- prolong abuse -> liver cirrhosis -> liver cells are destroyed and replaced with fibrous tissues - nervous systme issues
- depressant
- slows down brain functions
reduced self control
social lierties they regret doing - effects n reaction times
- poor muscle coordination and poor vision
- underestimate speed + judgement deteriorates
- traffic accidents
