Human Nutrition (chpt. 28) Flashcards
Nutrition
The way an organism obtains and uses its food
Functions of nutrition
Energy source
Growth
Repair
Reproduction
Formation of new substances
Defence
Autotrophs
An organism that makes its own food e.g. green plants
Heterotrophs
An organism that cannot make its own food and must take in ready-made food e.g. humans
Herbivore
Eats plants only e.g. rabbits
Carnivore
Eats animals only e.g. fox
Omnivore
Eats plants & animals e.g, hedgehogs, humans
Parasite
An organism that gets its food from a live source e.g. disease-causing bacteria
Saprophyte
An organism that gets its food from a dead source e.g. bread mould fungus
Stages of human nutrition
- Ingestion (taking in food)
- Digestion (breaking up food)
- Absorption (transfer of digested food into bloodstream & lymphatic system)
- Assimilation (use of digested food in body)
- Egestion (getting rid of undigested food)
Chemical digestion
The breaking up of food into smaller parts through the use of enzymes
Mechanical digestion
The physical breakdown of food into smaller parts e.g. using teeth
Name the 4 teeth and functions
Incisor - cutting and biting
Canine - tearing
Premolar - crushing and grinding
Molar - crushing and grinding
Human dental formula
2(I 2/2 C1/1 P2/2 M3/3)
Chemical digestion in the mouth
Salivary amylase
Produced by salivary glands
Saliva - water, salts, mucin, amylase, lysozyme
Soften and dissolve food
pH 7-9
Peristalsis
The rhythmic contraction and relaxation of the muscles in the gut wall to push food down to the stomach
What is the stomach?
A muscular, expandable, bag
Physical digestion in stomach
By peristalsis
Physically churns the food turning it into chyme
Role of HCl in stomach
pH of 1-2
Converts pepsinogen to pepsin
Sterilises food (by killing microorganisms)
Denatures salivary amylase
Role of pepsin / protease in stomach
pH 1-2
Some absorption occurs in stomach
Breaks down proteins into amino acids (smallest unit of a protein)
Name a substance stored in the liver
Vitamins A D E K
Glycogen
Iron
Copper
Pancreas
Produces insulin and digestive enzymes
Pancreatic juices: sodium hydrogencarbonate , amylase , lipase
Functions of the liver
Produces bile
Detoxification of poisonous substances e.g. drugs
Produces heat to warm blood & body
Deamination (removal of amino acids)
Storing vitamins e.g. vitamin D
Storing minerals e.g. iron, copper, zinc
What is bile
Formed from dead and broken down red blood cells
Green / yellow alkaline liquid
Produced in liver
Stored in gall bladder
Acts in liver and dudodenum
Made up of water, bile salts and bile pigments
Emulsifies fats
Function of duodenum
Digestion
Function of ileum
Absorption
Function of villi
Increase surface area for absorption
What is absorbed in the ileum
Glucose
Amino acids
Water-soluble vitamins and minerals
How has the small intestine adapted for increased absorption
Villi and microvilli
Walls are one cell thick which allows rapid movement (by diffusion)
Rich blood capillary network to carry soluble nutrients to the liver
Functions of large intestine
Water reabsorption
Elimination of faeces
Vestigial organ
No longer needed / used
E.g. caecum , appendix
Colon
Reabsorbs water and mineral salts to prevent dehydration
Diarrhoea occurs when material moves too quickly through colon
Constipation occurs from a lack of water or fibre
Rectum
Stores semi-solid waste
Anus
Waste removed as faeces (EGESTION)
What does the hepatic portal vein connect
Liver to the ileum
Benefits of symbiotic intestinal bacteria
Make vitamins B K
Protect us against pathogenic bacteria
Symbiotic
2 organisms living together (beneficial to both)
Sources of fibre
Cereal grains
Vegetables
Fruit
Role of fibre
Stimulates peristalsis
Prevents constipation
Soaks up cholesterol and toxic chemicals
Encourages the growth of symbiotic intestinal bacteria
Role of hepatic portal vein in digestive system
Brings nutrients and amino acids from intestine to the liver
Hepatic artery
Brings oxygen and lipids from the heart to the liver
Adaptations of the small intestine for absorption
Villi and microvilli increase surface area for absorption
Walls are one cell thick which allows for rapid movement of substances through them by diffusion
Rich blood capillary network
What type of waste is removed by egestion
Un absorbed food
Functions of HCl in stomach
- Activate pepsin
- Denature amylase
- Destroy microorganisms
Which stage of nutrition takes place predominantly in the duodenum
Digestion
Waste product of deamination
Urea
Which part of the alimentary canal has an endocrine function
Pancreas
DRAW the digestive system
DRAW the relationship between the alimentary canal and the liver and pancreas
DRAW longitudinal section of a villi
