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Definition for process of digestion
A group of organ concerned with conversion of food and liquids into basic nutrients which the body tissues require.
3 main components of the digestive system
Build and repair the body 

Fuel to produce heat and energy

Provide raw materials for body's chemical activities
Four stages of digestive process
What is peristalsis?
Rhythmic muscular contraction of the walls of the tract which pushes food through in one direction. Involuntary smooth muscle action.
Describe the mouth in relation to digestion
Contains tongue, teeth and 3 salivary glands.

Food mixed with saliva to produce bolus.

Enzyme in saliva breaks down starches.
Describe pharynx in relation to digestion
Bolus pushed into the pharynx by the tongue.

Epiglottis prevents food entering the trachea.

Describe oesophagus in relation to digestion
Soft muscular tube 25cm in length.

Smooth muscle and elastic connective tissues.

Lined with mucous membrane.

Passes through diaphragm to stomach.

Cardiac sphincter sits at the bottom at the entrance to the stomach and stops regurgitation.
Describe the stomach
J shaped muscular bag.

3 muscle layers, mucous membrane lining.

Food is mixed with gastric juice (pancreatic juice) which begins digestion of proteins and produces chyme.

2-6hours food passes through the pyloric sphincter into the duodenum. 

Describe the duodenum
25cm in length and curves round the head of pancreas.

Bile duct from the liver and the pancreatic duct from the pancreas open into the duodenum.

Pancreatic juice digests proteins, fats & carbs.

Pancreatic juice is strongly alkaline to neutralise acidity of chyme.
What does pancreatic juice contain?
Hydrochloric acid
Mineral salts
Describe the small intestine
Muscular tube lined with mucous membrane.

 6 metres in length.

Chemical digestion of food completed.

Broken down into carbs, fats & proteins.

Absorbed via diffusion and osmosis into blood stream.

Absorbed nutrients go to liver via hepatic portal vein.

Small intestine empties at ileo-caecal junction.
Describe the large intestine
1.5metres long, has 4 layers. 

The appendix is attached below the junction. 

Water and salts are further absorbed from faeces.

Produce bacteria vit K & folic acid

Passes waste products to rectum
Describe the rectum
13cm long

Passes faeces to anus 
Describe the anus
4cm long

Two sphincters:
Internal smooth muscle (involuntary)
External skeletal muscle  (voluntary)

Control elimination of faeces.
Acessory organs are...
Liver - largest gland exocrine and endocrine 

Pancreas - endocrine and exocrine gland.

 Peritoneum - serous membrane covering abdominal organs.

Gall bladder - adds mucous to bile, stores & concentrates it.
Other abdominal and pelvic organs..
Spleen - endocrine gland makes white blood cells (lymohocytes) breaks down red.

Kidneys - filter blood, regulate salt & water balance, excrete urine

Ureters - 25-30cm long

Bladder - muscular bag for urine 300ml full

Urethra - canal to outside of body
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