Hetrotrophic Nutrition (For Classes 7 and 10)
(NCERT page No 98 Class 10,Science Complete Explanation)    ---PART 2--- By P K Verma

Notes On Salivary Gland and Liver 
( For Class 7 and 10)


Explanation About Salivary Gland

NCERT Page 99 Science Class 10

                           

Saliva is a complex mixture and a hypotonic solution that is secreted continuously from the salivary glands under the control of ANS (Autonomic Nervous Suystem).

Daily secretion of saliva is about 1 to 1.5 litres and operates at 6.7 pH that is slightly acidic and almost neutral.

Secretion of saliva is a reflex action.

Saliva is formed of about 95.5% water 0.2% Minerals and 0.3% organic compounds like mucin and a starch splitting enzyme ptylin that is also called salivary amylase.

Mucin  is a glycoprotein and it helps in the lubricating the food in its passage down by giving it  slimy consistency. 

Types of Salivary Gland By Animation Video

Mucin is mainly produced by the sublingual and submaxillary gland whereas enzyme is mainly from parotids.

Liver is the largest and multi lobulated gland of about 1.5 kg weight and nearly  1 / 40  of total body weight.

Liver is differentiated into small left lobe and large right lobe separated by falciform ligament. 

In rabbit liver is made up of five lobes.

In frog liver is trilobed and liver of man is bilobed

Kupffer cells

Kupffer cells of liver acts as phagocytes which eat up  the dead cells and bacteria by phagocytosis.

Gall bladder

Gall bladder is a pear shaped yellow-green sac like structure lies on the inferior surface of the right lobe.

Gallbladder stores bile which is secreted by liver cells and collected by bile capillaries.

Bile 

Bile  produced by liver makes the media alkaline having pH 7.8 to 8.6. 

Bile  contains 92% water 6% bile salts 0.3% by pigments that is yellow coloured bilirubin and green coloured biliverdin.

Bile salts

Bile salts contain sodium chloride , sodium bicarbonate that is both are inorganic Salts and sodium glycochocolate and sodium taurocholate and both  are organic solids. 

Emulsification Of Fats 


Emulsification of fat is the breakdown of large fat globules into smaller, uniformly distributed particles. It is accomplished mainly by bile salts in the small intestine. 

Emulsification is the first preparation of fat for chemical digestion by specific enzymes. 

Emulsification greatly reduces the interfacial tension of fat and allows that fat to be broken into small particles for easier digesting by enzymes.



Gall Stones

Gallstones are formed by bile Salts and Calcium whose formation is promoted by high cholesterol level.

Heparin

Liver produces an anticoagulant called heparin which prevents blood clotting inside the blood vessel. 

Heparin Structure

Liver produces two proteins that is prothrombin and fibrinogen which helps in clot formation.