24. Human Nutrition Flashcards
Nutrition def.
The way an organism obtains and uses its food
The two types of nutrition
Autotroph- makes own food through photosynthesis
Heterotroph- Eats other organisms for food
Digestion def.
The physical and chemical breakdown of food into soluble particles small enough to pass into the blood and to the body cells
Alimentary canal diagram
Mouth (salivary gland) Oesophagus Stomach Duodenum (Liver, gal bladder, bile duct, pancreas) ileum Appendix Caecum Colon Rectum Anus
Steps in digestion (4)
Ingestion
Digestion
Absorption
Egestion
Ingestion def. and where
def. Food is taken into the alimentary canal
where: the mouth
Digestion def. and where
Def: The physical and chemical breakdown of food into soluble particles small enough to pass into the blood and to the body cells
Where: mouth, oesophagus, stomach, small intestine
Absorption def. and where
Def: the movement of digested food into the blood.
Where: small intestine
Egestion def and where
Def: Removal of undigested, unabsorbed food as faeces
Where: Anus
Def. of peristalsis
Rhythmic muscular contraction and relaxation in the wall of the alimentary canal (oesophagus) causing the food to move along the canal and be broken down
Where does mechanical digestion take place
teeth
peristalsis (oesophagus)
Contractions in stomach wall
Mechanical Digestion in mouth
Function
Name teeth and function
Food is broken down by the teeth by chewing
this increases the surface area for the enzymes to work.
Teeth: Incisors (front- biting of a piece), Canines (side-tear), Premolars and Molars (back- chew and grind)
Dental formula
32 teeth
I (2/2), C (1/1), P (2/2), M (3/3)
upper no.=teeth on top half of one side
lower no= teeth on bottom half of same side
Structure of a tooth
Diagram in copy Crown, Root, Gums Out---> In Enamel (protect), Dentine (typical tooth structure), Pulp Cavity (contains blood vessels and provides nutrients for tooth)
Chemical digestion in the mouth enzyme role/substrate product production site action site optimum ph
Enzyme: amalyse Role/Substrate: Digests starch Product: Maltose Production site: Salivary glands (mouth) Action site: In the mouth Optimum pH: pH 7/8
Digestion in the oesophagus
Made up of a muscular tube
Role: Brings food to stomach. Food moves by peristalsis so digests the food
Digestion in the stomach
muscles that allow food to enter leave
shape
types of digestion
Food enters the stomach from the oesophagus when the cardiac sphincter muscle opens.
Is a J shaped muscular bag.
Involved in chemical and mechanical digestion
food leaves when pyloric muscle opens
Mechanical digestion in the stomach
Muscles contract which churns the food and makes chyme
Chemical Digestion
Produces gastric juice containing Mucus, HCL, Pepsinogen
Role of
- Mucus
- HCL
- Pepsinogen
- Mucus: lines and protects the stomach so it doesnt digest itself.
- HCL: Hydrochloric acid: gives a pH of 1/2-the optimum pH for the enzyme. Kills bacteria present. Activates pepsinogen (pH 1/2). Denatures Amalyse (pH 7/8)
- Pepsinogen: enzyme produced in stomach. Inactivates to prevent self digestion. Converted to active enzyme pepsin by HCL when it comes in contact with food.
Digests proteins to peptides
Pepsin Role Substrate Product Production site Action site Optimum pH
Role: Digests protein Substrate: Proteins Product: Peptides Production site: Stomach in gastric glands Action site: Stomach Optimum pH: pH 1/2
How does the stomach prevent self digestion?
Mucus lines the wall. It is an alkaline (pH 7-14) so protects against acid pH.
- Cells in wall are tightly packed together and renewed at a rapid rate
- Pepsinogen is inactive until it comes in contact with food.
Small intestine
Main Parts
pH
What happens
Main parts: Duodenum and ileum
pH 7/8 (because we left the stomach)
What happens: Chemical digestion (duodenum) Absorption (ileum)
How the duodenum digests the food
wall of duodenum: secretes intestinal juices containing different enzymes which break down food.
Pancreas and liver: produce juices that travel to the duodenum.
Role of pancreas
Produces pancreatic juices
they travel to the duodenum via the pancreatic duct. Contains enzymes lipase (fats) and amalyse (starch)
Lipase role substrate product production site action site pH
role: breaks down fats
substrate: Fats/ Lipids
product: Fatty acids and glycerol
production site: Pancreas
action site: duodenum
pH: 7/8
Amalyse role substrate product production site action site pH
role: digests starch
substrate: starch
product: maltose
production site: Pancreas/ small intestine
action site: small intestine
pH: 6.7/7
Liver functions
Makes bile Breakdown of toxic substances, Regulates heat, Break down amino acids to urea, Breakdown carbohydrates to fat, Stores minerals (iron and copper), vit D and glycerol.
Bile
consists of
functions
more functions
Consists of: Water, bile salts, bile pigment
Functions: emulsifies fats (fats easier to digest-in fat droplets) and neutralises acidic chyme
Absorption
def.
where
def. The movement of digested food into the bloodstream.
Where: The ileum
Villi
what
function
What: finger like folds in the lining of the small intestine.
Function: increases surface area for absorption of digested food.
What is absorbed by villi and where they go
Water, Glucose, Amino acids, Vitamins, Minerals- absorbed into capillaries, travel to liver via the hepatic portal vein, stored by liver, released and passed to heart via hepatic vein and then passed to body.
Fatty acids and glycerol- absorbed into lacteal and transported to the lymph vessel and up to the subclavian veins into the vena cava to the heart.
Structure of villus
Lacteal in centre which goes to lymph vessels.
Network of capillaries- goes to hepatic portal vein.
Villus on outside
Function of hepatic vein and artery
Artery: Brings blood to the liver from the heart
Vein: Brings food from the liver to the heart
How the villus are adapted for absorption:
Walls 1 cell thick
Long so increases surface area
Large capillary supply for efficient absorption
lacteal present for digested fat absorption
Parts of the large intestine and functions
Appendix, Caecum: Function unknown Colon: Reabsorbs water, Forms solid waste (faeces), Bacteria in colon produce vit. B and K, Digest cellulose Rectum: Stores faeces Anus: Egestes faeces
Benefits and importance of Fibre
Sources
Stimulates peristalsis in colon: prevent constipation
Provides bulk so prevents overeating as takes longer to digest
Provides and promotes gut bacteria
Regulates blood sugar levels
Lowers cholesterol
Sources: Wholegrain foods, Fruit and veg, Porridge
