Autotroph photosynthesis

Nutrition

Herbivores

Carnivores

Omnivores

Heterotroph

Nutrition Balanced diet includes all 7 components

Carbohydrate-Protein – Fats-

4.5 calories/g 4.5 calories/g 9 calories/g

Obesity

New Food Pyramid 2005

- emphasise importance of controlling weight and physical activity

- dietary fats – limit saturated fats20-35% or less of energy should come from fats, healthiest are monounsaturated and polyunsaturated

Energy content of food measured in

kilocalories

The average teen-ager needs

Approximately 2200 calories for girls

2800 calories for boys

-limit sugar intake-stress benefits of wholegrains

Mouth-mechanical digestion (mastication) = teeth, tongue-chemical digestion = saliva (amylase, lysozyme)

Trachea - windpipe

Uvula – prevents food entering the nose

Epiglottis – safety hatch. A flap of cartilage prevents food from entering the trachea

Alimentary canal2 main functions:•Digesting and absorbing nutrients•Protecting from invasion

Oesophagus-transfers food to stomach by peristalsis

http://library.thinkquest.org/11226/main/c03txt.htm

Cardiac sphincter

-opens to allow food oesophagus stomach

-heartburn –acid escapes stomach oesaphagus

http://35.9.122.184/images/41-AnimalNutrition/41-16-Duodenum-L.gif

StomachShort term storage reservoir (1L for up to 4h)

Digestion = chemical (HCl and enzymes) - proteins

= mechanical - liquefication of food

Slowly releases food into intestine

chyme

Cardiac sphincter

Pyloric sphincter

Acid (HCl) – parietal cells

Hormone (gastrin) – G cells

Mucous – goblet cells

Enzymes (pepsinogen) – chief cells

Stomach epithelial cells are some of the fastest growing cells in the body, typically replacing themselves about every 3 days

Stomach Epithelium

Ulcers (stomach, duodenum) – peptic ulcers. Most commonly caused by H. pylori

Prevents self-digestion

pH 1-2Kills bacteriaLoosens fibrous foodsActivates pepsinogenDenatures salivary amylase

Activated to pepsinConverts proteins peptides

Controls gastric motility and acid secretion

Small IntestineAround 6m in an adultFood takes 1-6 h to pass through2 main tasks = digestion, absorption

3 partsDuodenum JejenumIleum

Pancreas –pancreatic juice= NaHCO3, enzymes (insulin, glucagon) pH of duodenum = 7-8 Amylase, lipase, trypsinogen, chymotrypsinogen

Liver – bile made in liver, stored in gall bladder = Water, salts, bile saltsNeutralise HCl Digestion and absorption of fats and fat soluble vitamins (emulsification)Waste products eliminated by secretion into bile and elimination in feces

(e.g. bilirubin, biliverdin)

Duodenum = digestion = 25cm long

LiverWeighs about 1.5kgHolds about 13% of total bloodLiver cell = hepatocyteUnique ability to regenerate – average life = 150 days

http://www.britishlivertrust.org.uk/content/liver/about.asp

Right lobeLeft lobe

Blood rich in food from ileum

The liver performs over 500 jobs. Some of these are:•Makes bile (600mls/day)•Detoxifies body (alcohol, drugs etc)•Breaks down excess amino acids urea (deamination) kidney•Converts glucose glycogen for storage (source of quick energy)•Converts excess carbohydrates fat•Stores vitamins - A, D, E and K •Stores minerals – Fe, Cu, Zn•Makes plasma proteins e.g. fibrinogen – blood clotting•Makes cholesterol – needed to form many hormones•Produces heat to warm blood •Clears blood of particles, including bacteria•Fights infections –half the body’s macrophages -destroy bacteria •Produces hormones, including the sex hormones

Jejenum – digestion/ absorption. 2.5m long

Ileum – absorption. 4m long

Walls only one cell thickVilli, microvilli – increase surface area for absorptionRich blood supply – capillaries absorb water and soluble nutrients (glucose, amino acids, vitamins, minerals) and the blood carries the nutrients to the liver, which stores nutrients and releases them as required

Lacteal – contains lymph. Fatty acids and glycerol are absorbed by the epithelial cells where they reform into fats. They become coated in protein (chylomicrons) and pass into the lymph in the lacteals. It takes around 18h for lymph to rejoin the blood, the protein coat dissolves and fats are absorbed into cells

Small Intestine cont.

Large Intestine

1.5m long, 6cm diameter

Food stays 10h to a few days

ColonReabsorbs water – so waste is converted to semi-solid = faeces – egestedDiarrhoea, constipation (fibre helps stimulate peristalsis)

Caecum

Appendix

Function unknown – in herbivores they contain bacteria that help digest cellulose