24. Human Nutrition Flashcards
(37 cards)
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.
