Nutrition in Humans
Nutrition
Process by which organisms obt. food & energy for growth, repair, maintenance of body
Processes
Feeding/Ingestion
Digestion
Absorption
Assimilation
Human Digestive System
Alimentary Canal
Mouth
Oesophagus
Stomach
Small intestine
Duodenum
Ileum
Large Intestine
Narrow, muscular tube tht. extends to stomach
Distensible musc. bag
Ab. 6m long in adults
Colon
Rectum
Ab 1.5m long
Liver
Gall bladder
Pancreas
Digestion
Physical
Chemical
Mechanical break up of food into smaller partic.
Eg chewing, peristalsis (in oesophagus), churning of stomach wall
Break down of large molec. in food into smaller soluble molec. tht. can b. absorbed
Involves hydrolytic reactions catalysed by digestive enzymes
Entrance to buccal cavity
Whr. digestion begins
Teeth
Tongue
Salivary glands
Saliva
Salivary amylase
Walls made up of longitudinal + circular musc.
Breaks up larger pieces of food into smaller pieces
Rolls into small, slippery, round masses/boli
Mucin
Softens food
Digests starch into maltose
Peristalsis
Gravity pushes bolus into stomach
Contraction & relaxation of musc. to push food down into stomach
Gastric glands
Gastric juice
Peristalsis/Churning of stomach wall
Mixes food w. gastric juice
Pepsin & renin
Hydrochloric acid
Acidic medium for action of pepsin & renin
Act on proteins
Kills micro-organisms in food
Release of alkaline fluids
Alkaline medium
Intestinal juice
Pancreatic juice
Bile
Neutralises acidic chyme
Pancreatic amylase
Pancreatic protease
Pancreatic lipase
Maltase
Lactase
Lipase
Site of absorption
Adaptation
Large SA:Vol
Thin separating membrane
Steep conc. gradient
Long length
Villi in inner walls incr. SA
Numerous folds in its (villi’s) inner wall incr. SA
Microvilli in epithelium of villi incr. SA
Many capillaries present to carry nutrients away quickly
Thin walls to make it easy for nutrients to pass thru. to bloodstream
Diffusion
Active transport
Glucose + AA diffuse into blood capillaries
Glycerol + fatty acids diffuse into epithelium
Combine to form minute fat globules which enter
lymphatic capillary
Glucose + AA absorbed
Anus
Faeces stored temporarily
Faeces discharged thru. here (egestion/defecation)
Nutrients
Carbohydrates
Fats
Protein
starch –(salivary amlyase)-> maltose
starch –(pancreatic amylase)-> maltose
End products
maltose –(maltase)-> glucose
lactose –(lactase)-> glucose + galactose
Simple sugars (GFG)
Bile emulsify fats
Break down fats into smaller fat droplets tht. suspend in water
fats –(pancreatic + intestinal lipase)-> fatty acids + glycerol
protein –(pepsin)-> polypeptides
polypeptides –(peptidases/pancreatic protease)-> amino acids
Assimilation
Process whereby some of absorbed food subst. converted into new protoplasm/used to provide energy
*How are nutrients transported/utilised
Blood capillaries tht. supply small intestine unite
Hepatic portal vein
Transports sugars + AA frm. small intestine to liver
Lymphatic capillaries join tgt.
Lymphatic vessels
Discharge fats into bloodstream
Hepatic vein
Liver
Remaining glucose + AA leave liver
Distributed to APOP
Excess glucose
Excess AA
Converted into glycogen
Converted into urea/deaminated
Glucose
Used for respiration to prod. energy for cellular activities
Excess fats
Stored in fat/adipose tissues
For synthesis of cell membrane
For synthesis of new protoplasm/proteins
Detoxification
Storage of Iron
Regulation of blood glucose conc.
Production of bile
Protein synthesis
Emulsifies fats
Keeps it constant
Stimulated by seceretion of insulin & glucagon (by Islets of Langerhans in pancreas) to store/release glucose
Whr. recycling of haemoglobin of worn out RBCs. take place aft. they are destroyed in spleem
Break down of haemo.
Prod. iron stored in liver
Used in synthesis of new RBCs
Prod. bile
Converts harmful subst. into harmless prod.
Harmful effects of excessive alcohol consump.
Symptoms of drunkenness
Incr. risk of stomach ulcer
Freq. intake leads to addiction
Liver cirrhosis