Human Nutrition Flashcards
Nutrition
The way an organism obtains and uses food
Autotrophic (eg)
Organism that makes its own food (e.g. plants - photosynthesis)
Heterotrophic (eg)
Organism that can’t make its own food
Digestion
The physical and chemical breakdown of food
need for digestion
Breakdown large food particles until they’re small enough to pass into body cells
need for digestive system
digest food in single location, individual cells don’t have to contain full range of digestive enzymes
main stages of digestion
ingestion
digestion
absorption
egestion
ingestion
Food taken into alimentary canal
digestion
Food broken down into smaller soluble pieces
absorption
Movement of digested food from alimentary canal into blood system
egestion
Removal of unabsorbed material as faeces
methods for mechanical breakdown of food
teeth
contractions in stomach wall
peristalsis
peristalsis
waves of muscular action in walls of alimentary canal moving contents along
what stimulates peristalsis
fibre
teeth & use
incisors - cutting
canines - tearing
pre molars & molars - crushing/grinding
dental formula
2(I 2/2 - C 1/1 - PM 2/2 - M 3/3)
amount of teeth in child and adult
adult - 32
child - 20
length of oesophagus
muscular tube 25cm long
location of oesophagus
connects pharynx to stomach
Function of oesophagus
Food moves down the oesophagus by peristalsis
Stomach shape
J shape muscular bag
Functions of stomach
-Stores food for about four hours -churns and mixes food with gastric juice forming chyme
-digests food
Mechanical digestion in the stomach
peristalsis
Chemical digestion in the stomach
Use of gastric juice containing: mucus, HCL & pepsinogen
Mucus
Lines and protects stomach wall
Hydrochloric acid
-Kills bacteria
-activates pepsinogen (i.e. pepsin)
Pepsinogen
-activates enzyme pepsin due to hydrochloric acid
-pepsin converts proteins into peptides
Cardiac sphincter muscle
Circular muscle which contracts to close entry from oesophagus to stomach
Pyloric sphincter muscle
Circular muscle which contracts to close entry from stomach to duodenum
length of small intestine
5 - 6m long
Function of small intestine
digestion & absorption
Parts of small intestine
duodenum, jejunum, ileum
length of duodenum
25cm
Function of duodenum
digestion
Function of jejunum and ileum
absorb nutrients
adaptations for absorption
Long tube = gives time for absorption
Villi = Increase surface area available for absorption of digested food
Villi
Infoldings in lining of small intestine
Functions of large intestine
-Reabsorbs water
-produces B group vitamins
-digest cellulose
How are functions in large intestine carried out?
by symbiotic bacteria
Symbiosis
Relationship between two organisms where at least one organism benefits
Mutualistic symbiosis
Relationship between organisms where both benefit
Symbiotic bacteria
Obtain food and place to live from humans
Functions of symbiotic bacteria in humans
Produce vitamin B and digest cellulose
Functions of caecum and appendix
Unknown in humans
Rectum
Stores faeces
Functions of the liver (5)
-Produces bile
-detoxifies body (alcohol and drugs)
-breaks down dead red blood cells
-stores vitamins
-produces heat to warm blood (respiration)
Bile (colour)
yellow-green liquid
bile (location)
-stored in gall bladder
-enters duodenum through bile duct
Bile consists of
- water
- bile salts
- bile pigments
Functions of bile
-Neutralises acidic chyme from stomach
-Emulsifies fats (increases the surface area of fat droplets)
Functions of the pancreas (ie)
-Produces insulin (regulates blood sugar level)
-Production of enzymes (i.e. amylase lipase)
Benefits of dietary fibre
-Stimulates peristalsis in colon
-Prevents constipation
Constipation
When undigested material passes through colon too quickly
Enzymes involved in digestion
-amylase
-pepsin
-lipase
Role of salivary amylase
Digest starch
Production site of salivary amylase
Salivary glands
Where does salivary amylase act?
Mouth
PH of salivary amylase in the mouth
8 (alkaline)
Digestion product of salivary amylase
Maltose
Role of pepsin
Digest protein
Production site of pepsin
Gastric glands in stomach wall
Where does pepsin act?
Stomach
PH of pepsin in mouth
2 (acidic)
Digestion products of pepsin
Peptides
Role of lipase
Digest fat
Production site of lipase
Pancreas
Where does lipase act?
duodenum
PH of lipase in mouth
8 (alkaline)
Digestion products of lipase
Fatty acids and glycerol
Features of a balanced diet
-Must contain all necessary food types in correct proportions
-food types must be eaten in moderation
Food type is necessary for a balanced diet (7)
Water, vitamins, protein, carbohydrates, minerals, lipid, fibre
Factors that affect food intake
-Age
-gender
-activity levels
