Human Nutrition - Digestion Flashcards
nutrition
the way in which an organism obtains and uses food
autotrops
organisms that can make their own food ie. green plants, but photosynthesis
heterotrops
organisms that canot make their own food and must get it from environment
herbivores
feed only on plants
carnivores
eat other animals
omnivores
eat both plants and animals
example of herbivore
cow
example of carnivore
dogs
example of omnivore
human
stages of human nutrition
- Ingestion
- Digestion
- Absorption
- Egestion
(assimilation)
ingestion
the taking of food into the alimentary canal i.e putting it into the mouth
digestion
the mechanical or chemical breakdown of food into smaller molecules so that it can be absorbsed
absorption
soluble products of digestion can now pass through the cells lining the small intestine into the blood and lymph systems
egestion
the removal of unabsorbed and undigested material from the digestive system (through the anus)
assimilation
the absorbed food is used to make new molecules of for release of energy
7 components of a balanced diet
carbohydrates, protein, lipids, vitamins, minerals, fibre, water
what is a balanced diet
the 7 components must be present in the right amounts
factors affecting amount of food required in a person
age- growing teenagers need more food than elders
activity levels- more if you exercise a lot
frequency of sugar and alcohol
restricted intake
frequency of dairy
2-3 a day
frequency of meat/fish/protein
2-3 a day
frequency of fruit and veg
3-5 a day
frequency of starchy carbs
6-11 a day
pH of mouth
7-8
type of digestion in mouth
chemical and physical
mechanical digestion
breakdown of large pieces of food by physical or mechanical ways
mechanical digestion in the mouth
chewing action of the teeth
chemical digestion
chemical breakdown of food by enzymes
chemical digestion in mouth
amylase converts starch to maltose
human teeth types
incisors canines premolars and molars
incisor function
cutting
canine function
stabbing and tearing
premolar and molar function
chewing and grinding
dental formula for half mouth
I 22 C 11 P22 M33
how many teeth in adult whole mouth
32
herbivore teeth
broad, rigid premolars and molars
carnivore teeth
long sharp canines
salivary glands arranged in mouth
3 pairs of them
4 components of saliva
water and mucous (mucin)
salts
salivary amylase
lysozome
function of mucin in saliva
moisten and lubricate the food and make it easier to swallow
function of salts in saliva
provide neutral to slightly alkaline pH, optimum for amylase
function of salivary amylase in saliva
enzyme that converts starch to maltose
function of lysozome in saliva
helps kill microorganisms eg.bacteria
name for ball of food made in the mouth
bolus
flap of skin and cartilage in throat
epiglottis
peristalsis
involuntary muscle contractions of the gut wall which moves food
what is the stomach
a muscular bag that receives food from the oesophagus
pH of stomach
2
for how long is food stored
2-4 hours
semi-solid liquid stomach churns food into
chyme
sphincter
a ring of muscle that opens and closes
top stomach sphincter
cardiac sphincter
bottom stomach sphincter
pyloric sphincter
3 components of gastric juice
mucous (mucin) hydrochloric acid (HCl) enzyme pepsin(ogen)
function of mucous in gastric juice
protects lining of stomach from digesting itself
function of HCl in gastric juice
provides acidic environment of pH 2, optimum for pepsin enzyme and activates pepsinogen
type of pepsin in gastric juice and why
pepsinogen, inactive form so as not to digest the lining of the stomach
how is pepsinogen activated
by HCl
what type of enzyme is pepsin?
protease
3 roles of HCl in the stomach
- activates pepsinogen to pepsin
- sterilises food, kills microorganisms
- chops up starch into short sections (mechanical di)
small intestine pH
7-9
sections of small intestine
duodenum
ileum
how long is the duodenum
25cm
how long is the ileum
5.5m
function of duodenum
where digestion occurs
function of the ileum
where absorption of digested foods into blood and lymph
3 places from which the small intestine receives secretions
the liver
the pancreas
the lining of the intestine itself
where is the liver located
above the stomach
function of the liver
produces bile
what is bile
a green fluid that breaks down lipids
where is bile stored
in the gall bladder
how does the bile get from the liver to the duodenum?
through the bile duct
3 components of bile
bile salts
bile pigments
sodium hydrogen carbonate
function of bile salts in bile
emulsify fat, mechanical process, break down fat droplets to increase their surface area
what are bile pigments?
no digestive function
an excretory product of the breakdown of old blood cells
does bile contain digestive enzymes?
no
does bile contain water?
yes
where is the pancreas located?
below the stomach
what does the pancreas secrete?
pancreatic juice (and insulin)
3 things pancreatic juice consists of
sodium hydrogen carbonate
enzymes
water
function of sodium hydrogen carbonate in the pancreas
An alkaline salt that neutralises the stomach acid, allows enzymes in small intestine to work best
enzymes of pancreatic juice
pancreatic amylase
lipase
how is food absorbed
passes through the cells lining the small intestine by diffusion and active transport and into the blood and lymph systems
path glucose and amino acids take when absorbed
pass by diffusion into blood capillaries ad go into hepatic portal vein
what does hepatic portal vein
brings blood from the gut to the liver
path fatty acids and glycerol take when absorbed
absorbed into lymph lacteals, these joinand eventually empty lymph into the blood system
which nutrients go into the blood capillaries in villus
glucose amino acids vitamins minerals water salts
which nutrients go into the lymph lacteals
fatty acids
glycerol
fat soluble vitamins
why is the intestine folded into villi?
to increase the surface area of the wall
where are microvilli?
on the cells lining the villi
5 ways in which the ileum is adapted for absorption
- it’s very long (about 5.5m)
- many villi increase surface area
- wall is only 1 cell thick, products pass through quickly
- large blood supply in the villus to absorb and carry away products
- each villus has a lacteal with lymph to carry digested fats
how long is the large intestine
approx. 1.5m
diameter of small intestine
3cm
diameter of large intestine
6cm
4 parts of large intestine
caecum, appendix, colon, rectum and anus
where is the caecum in the large intestine
below the junction with the small intestine
where is the appendix found
at the end of the caecum
function of caecum and appendix
no function, vestigial organs
vestigial organs
no longer have a function
whats different about the caecum and appendix
they contain enzymes to digest cellulose
main function of colon
reabsorb water by osmosis
faeces
liquid waste turned semi-solid
colour of faeces
due to bile
diarrhoea
waste moves to fast through colon, not enough water reabsorbed
constipation
waste moves too slow through colon, too much water reabsorbed
2 functions of symbiotic bacteria in the colon
a) produce vit B & K
b) prevents growth of pathogenic bacteria
symbiosis
relationship between two different species where one or both benefit from the relationship
function of rectum
stores faeces before removal through the anus
egestion
the removal of undigested or unabsorbed materials
is faeces excreted and why
no, excretion is the removal of waste products of metabolism
6 components of faeces
undigested food bile pigments salts bacteria dead cells water
other name for fibre
roughage
how does fibre stimulate peristalsis
it bulks up the food and stimulates the contractions
how does fibre prevent obesity?
gives a feeling of fullness
what is the largest internal organ/gland in the body?
the liver
6 functions of the liver
stores energy deamination stores fat soluble vitamins makes bile stores minerals detoxifies chemicals and alcohol
how does the liver store energy
stores glucose as glycogen and breaks it back down when its needed
which fat soluble vitamin does the liver not store?
E
an example of a mineral stored in the liver
iron
Hepatic artery
carries blood from aorta to liver
Hepatic vein
carries blood to inferior vena cava
hepatic portal vein
bring blood and digested food from the gut to the liver
