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Nutrition & Digestion :green_apple: (Nutrition: Providing food…
Nutrition & Digestion :green_apple:
Digestion:
The breakdown of carbohydrates, proteins and fats into small soluble substances that can be absorbed into the blood
The digestive process
Absorption:
Nutrients are absorbed from digestive system into blood which carries nutrients to cells
Egestion:
Removal of waste products from digestive system
Digestion:
Food is transformed into nutrients so the body can absorb it
Ingestion:
The intake of food through the mouth
Buccal cavity:
Mastication
pH normally between 6.5-7.5
Optimal pH for salivary amylase is 6.7-7.0
Teeth assist with mastication
Tongue contains taste buds
The digestive system
Epiglottis:
switch between oesophagus and larynx to prevent food going down airway
Upper GI tract
Liver
Bile ducts:
Carry bile through liver and gall bladder
Hepatocytes:
Produce bile and monitor blood to remove potentially toxic substances
Bile:
Mixture of water, bile salts, cholesterol and bilirubin - emulsifies large masses of fats to make them easier to digest
Stores many vitamins and minerals
Oesophagus:
The conduit for food and drink from pharynx to stomach
Mucous glands produce mucus to help lubricate and protect against stomach acid
Involved in swallowing and peristalsis
Involved in vomiting reflex to void stomach of contents
Stomach:
Main food storage tank of the body
Optimal pH for pepsin is 1.5-1.6
pH normally between 1.0-2.5
Gastric pits contain exocrine cells that secrete digestive enzymes and hydrochloric acid
Mucous cells and gastric pits secrete mucus to protect stomach against own secretions
Pyloric sphincter:
Controls movement of food into the intestines
Gallbladder:
Small storage organ - holds bile until needed to digest fatty foods
Pancreas
Secretes pancreatic juice:
mixture of water, salts, bicarbonate and many different digestive enzymes - helps to complete digestion in duodenum
Omentum:
Storage for fat
Lower GI tract
Small intestine:
Absorbs about 90% of nutrients
pH normally 8.5
Optimal pH for lipase is 8.0
Duodenum
Connects to pyloric sphincter
Bile and pancreatic juice complete digestion in duodenum
Jejunum
Primary site of nutrient absorption
Ileum
Ileocecal sphincter: *Empties contents into large intestine
Completes absorption
Large intestine:
Absorbs water and vitamins and converts digestive food into faeces
Colon
Stores and compacts faeces
Absorbs water, vitamins, minerals and remaining nutrients
Utilises non-digestible fibre as carbohydrate source
Bacteria
Produces Acetate and Butyrate as waste products
Can be used by cells lining colon as nutrients
This means 10% of non-digestible fibre can be utilised by humans
Rectum:
Connects colon to anus and stores faeces until the body is ready to defecate
Anus:
Orifice that faeces passes through during defecation
Nutrition:
Providing food necessary for health and growth
Lipids
Ester bond
Broken down by lipase
Broken down into fatty acids and glycerol by lipase
Fatty acids and glycerol can be absorbed
Absorbed by cells
Excess stored as fat
Used to make membranes
Used to make hormones
Lipase produced in pancreas
Hydrolysis reaction
Proteins
Peptide bond
Broken down by peptidase
Endopeptidase
Endopeptidase breaks down proteins into polypeptides
Produced in pancreas and chief cells in stomach
Exopeptidase
Exopeptidase breaks down polypeptides into amino acids
Amino acids can be absorbed
Absorbed by cells
Used for protein synthesis
Excess deanimated
Forms urea
Carbon skeleton converted to carbohydrate
Produced in ileum
Hydrolysis reaction
Starch
Glycosidic bond
Broken down by amylase and maltase
Amylase
Produced in salivary gland and pancreas
Maltase
Produced in ileum
Broken down into maltose by amylase and then again into glucose by maltase
Glucose can be absorbed
Used for respiration
Excess stored as fat
Hydrolysis reaction:
The addition of water to break down large molecules into small molecules
Polysaccharide of alpha glucose
Fibre (particularly cellulose)
Cannot be broken down
Helps peristalsis
Peristalsis:
Moves food through the digestive system
Stored in large intestine before egestion
Carbohydrates:
Source of energy
Vitamins and Minerals
Vitamin C:
Helps heal wounds and maintain healthy connective tissue
Vitamin D:
Helps maintain healthy bones and teeth
Vitamin A:
Helps vision, healthy skin and immune system
Vitamin B12:
Keeps nerve and blood cells healthy, helps make DNA and prevents megaloblastic anaemia
Calcium:
Helps maintain healthy bones and teeth, control muscle contractions and normal blood clotting
Iron:
Needed to make haemoglobin