How do saliva, pancreas and liver help in the digestion of food in man.

Draw a diagram of digestive system to show the position of pancreas

and liver.

Saliva

• Saliva is produced by glands.• These are called salivary glands• There are of 3 kinds and are in 3 pairs

Sublingual gland

• They are found below the tongue

Ingredients in saliva

• 1/ water and mucous• 2/ NaHCO3 and salts• 3/amylase (ptyalin) which digests CHO

1/ water and mucous

• Together they form slimy liquid which moistens and lubricates the food.

• This is how food can be chewed efficiently and can pass down food pipe easily.

2/ NaHCO3 and salts

• They are slightly antiseptic but theirmain function is to stabilize pH of food.

3/amylase (ptyalin) which digests CHO

• It digests starch and glycogen to maltose.

pancreas• It is a large gland.• Its exocrine tissue secretes a juice.

Glands

• Glands in the human body are classified as exocrine or endocrine. The secretions of exocrine glands are released through ducts onto an organ's surface, while those of endocrine glands are released directly into the blood.

Pancreatic enzymes and other ingredients

• Amylase• Lipase• Trypsin

other ingredientsNaHCO3

• Pancreatic juice flows from pancreatic duct into duodenum.

• Enzymes in pancreatic juice digest CHO,f ats and proteins.

Amylase

• Also called amylopsin .• It digests starch in to maltose.

starch• It is the most common carbohydrate in the

human diet and is contained in large amounts in such staple foods as potatoes, wheat, maize (corn), rice.

Lipase

• It digests fat.• It hydrolyses a small percentage of fats into

fatty acids and glycerol.

Glycerol• It is a colorless, odorless, viscous liquid that is

widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids known as triglycerides. Glycerol is sweet-tasting and of low toxicity.

Trypsin

• IT is secreted as inactive form called trypsinogen.

• It is activated by enterokinase.• IT splits proteins in to peptones and

polypeptides.

Enterokinase.

• Is secreted by lining of duodenum

NaHCO3

• It partly neutralizes chyme coming from stomach.

• It is necessary because enzymes of pancreas do not work well in acid conditions.

Liver

• It secretes bile.• Bile is temporarily stored in gallbladder.• Bile is released in to duodenum through bile

duct.• Bile is green in colour and is a watery fluid.

• It has no enzymes.• Bile’s green colour is due to bile pigments.• Bile also has bile salts.

How are bile pigments formed

• They are formed by breakdown of Haemoglobin in the liver.

• If bile pigments cant leave digestive tract they get accumulated in blood and cause

jaundice.Gallstones can stop bile pigments from leaving the digestive tract / block release of bile.

Bile salts

• They act on fats and emulsify them.• Emulsification means break them up in to

small globules which are then easily digested by lipase.

Gallstones

• When cholesterol precipitates in gall bladder , it forms gall stones.

• Cholesterol is produced by liver.

Functions of liver

• Liver converts toxic (dangerous to human health)substances to less toxic compounds.

• Ammonia is converted to urea.• Urea leaves body through kidneys.