human nutrition Flashcards
:D
what’s a balanced diet
- diet containing all the required nutrients
- in suitable proportions
- and the right amount of energy
state causes of scurvy and rickets
scurvy - lack of vit c
rickets - lack of vit d
main organs of the digestive system
alimentary canal and associated organs.
Alimentary canal
Mouth, oesophagus, stomach, small intestine, large intestine
Associated organs
Salivary glands, pancreas, liver
Describe the function of the organs in the alimentary canal
Mouth
Mouth
* inital site for ingestion using teeth, lips, tongue.
* Teeth bite and grind into food into smaller pieces, increasing S.A
* Begins physical digestion
* Tongue mixes food w saliva.
Describe the function of the organs in the alimentary canal
Oesophagus
Oesophagus
* 2 tubes leading down from back of mouth, the one in front is trachea.
* Behind trachea is oesophagus; takes food down to stomach.
- Hole in centre of oesophagus, down which food can pass = lumen.
- Entrance to stomach from oesophagus is closed by a sphincter muscle. Muscle relaxes to let food pass into stomach. Contracts to close entrance.
Describe the function of the organs in the alimentary canal
Stomach
Stomach
* Strong muscular walls, which contract & relax to mix the food with enzymes and mucus.
* Contains goblet cells = secrete mucus.
* Enzymes produced = proteases (by stomach walls) = pepsin = optimum pH 2 = chemical digestion
* Hydrochloric acid (produced by stomach walls) = pH 2 = kills harmful microorganisms in food = provides acidic pH for optimum enzyme activity
How long does the stomach store food? How does it let food pass into small intestine?
- 1-2 hours
- Spinchter muscle relaxes, lets partly digested food move into duodenum
Describe the function of the organs in the alimentary canal
Small intestine - Duodenum
Duodenum
* Pancreatic duct leads from pancreas into duodenum into which pancreatic juice flows into duodenum. Chemical digestion continues in duodenum.
- Liver secreted bile, stored in gall bladder.
- When food enters duodenum, the bile flows along bile duct and is mixed with food in duodenum.
What is the role of bile? Does it do physical/chemical digestion?
- emulsifying fats and oils
- to increase the surface area
- for chemical
digestion
Describe the function of the organs in the alimentary canal
Small intestine - Ileum
Ileum
* where all digested nutrients are absorbed into blood
* water is also absorbed into blood.
Describe the function of the organs in the alimentary canal
Large intestine - Colon, Rectum, Anus
Colon
* Absorbs water that still remains in food.
Rectum
* Stores undigested food as faeces.
* These are egested from body through the Anus
Describe the function of the associated organs in digestive system
Salivary glands
Salivary glands
* Secrete saliva, mixture of water, mucus, amylase.
* Water helps dissolve substances in food, allows taste.
* Mucus helps chewed food bind together to form a bolus, lubricates it so it easily slides down oesophagus.
* Amylase digests starch.
Describe the function of the associated organs in digestive system
Pancreas
Pancreas
* Secretes pancreatic juice that flows down pancreatic duct into duodenum.
* Pancreatic juice contains enzymes that help with chemical digestion of food in duodenum.
* It is an alkaline mixture.
Describe the function of the associated organs in digestive system
Liver
Liver
* Secretes bile; yellowish green, watery.
* Alkaline.
* Bile emulsifies fats and oils to increase the S.A for chemical digestion. Which is physical digestion.
* Neutralizes the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action.
Describe the function of the associated organs in digestive system
Gall bladder!
Gall bladder
* where bile is stored
* when food enters duodenum, flows along bile duct; mixed with food in duodenum.
define ingestion, digestion, absorption, assimilation, egestion
Ingestion
* taking in of substances e.g food or drink into body.
Digestion
* breakdown of food
Absorption
* movement of nutrients from intestines into blood
Assimilation
* uptake and use of nutrients by cells
Egestion
* removal of undigested food from body as faeces
define physical digestion
- the breakdown of food into smaller pieces
- without chemical change
- to the food molecules
Why is physical digestion useful
increases the surface area of food
* for the action of enzymes in
chemical digestion
Describe the functions of the types of human
teeth in physical digestion of food
Incisors
* sharp edged, chisel shaped at front of mouth
* used for biting and cutting food
Canines
* pointed teeth at either side of incisors
* used for gripping and teaar food
premolars
* broad, ridged surfaces, found between canines and molars
* grinding food to increase S.A
molars
* similar to premolars; larger, with broad ridged surfaces found towards back of mouth
* grinding food to increase S.A
stucture of human teeth:
enamel; function
Enamel
* hardest subtance made by animals. covers surface of a tooth
* difficult to break or chip. can be dissolved by acids
stucture of human teeth:
dentine; function
Dentine
* Under enamel is layer of dentine
* it is a living tissue; has channels in it which contain living cytoplasm
stucture of human teeth:
pulp; function
Pulp
* in the middle of tooth, there’s nerve and blood vessels.
* blood vessels supply cytoplasm in dentine with nutrients and oxygen.
stucture of human teeth:
nerves and blood vessels; function
Nerves
* allow teeth to sense pressure and pain
Blood vessels
* supply cytoplasm in dentine with nutrients and oxygen
stucture of human teeth:
cement; function
cement
* part of tooth thats embedded in gum is covered with cement.
* has fibres growing out of it.
* fibres attach tooth to bone in jaw, allow it to move slightly during mastication.
define chemical digestion
- breakdown of large insoluble molecules
- into small soluble molecules
role of chemical digestion
- producing small soluble molecules that can be absorbed
function of enzymes
amylase
protease
lipase
Amylase
* breaks down starch to simple reducing sugars
Protease
* breaks down proteins to amino acids.
Lipase
* breaks down fats and oils to fatty acids and glycerol.
state where in the digestive system these are secreted and where they act:
Amylase
Protease
Lipase
Amylase
* Salivary glands; acts in mouth
* Pancreas; acts in duodenum
Protease
* Walls of stomach; acts in stomach
* Pancreas; acts in duodenum
Lipase
* Pancreas; acts in duodenum
Describe the digestion of starch in the digestive system:
amylase, maltase
Amylase
* breaks down maltose to maltase
Maltase
* breaks down maltose to glucose on the epithelium lining the small intestine.
Describe the digestion of protein in the digestive system:
proteases
Pepsin
* breaks down protein in acidic conditions of the stomach
Trypsin
* breaks down protein in the alkaline conditions of small intestine.
In what region are the nutrients absorbed?
Small intestine
Where is most water absorbed?
- small intestine
- but some also absorbed from colon
describe structure of villi
location
- inner wall of small intestine
- cell membrane on each villus folded to form many tiny microvilli.
- it is on these membrnaes that maltase acts, breaking down maltose into glucose molecules.
function of villi and microvilli
- absorb digested nutrients into blood
- they increase the internal surface area for absorption which increases rate at which nutrients can be absorbed
what is the function of lacteal in villus/villi
- absorbs fatty acids and glycerol
function of capillaries in villus
- Glucose, amino acids, fatty acids, glycerol, vitamins, mineral ions and water are absorbed.
- These substances pass into blood capillaries inside the villus.
- The blood capillaries from all villi link up to join a vein called the hepatic portal vein. it takes all these substances to the liver.
