1. Vitamins

2. Doesn't metabolize to yield energy .
-vital to life .
-group of substance turned out to have the particular metabolic activity .
- nitrogen –containing chemical substance called an amine { vital amine }.

3. *definition of vitamins :
-vital organic dietary substance that is not an energy producing CHO,fat ,protein ,needed in very small quantities to perform a particular metabolic function .
It cant be manufactured by the body & therefore must be supplied in food .

4. ** classification of vitamins :
Fat soluble vitamins :
A,D,E,K
- they can be stored .
-associated with lipid .
2- water soluble vitamins :
-B complex family ,C
-they cannot be stored .
-vitamins B act as co-enzyme in cell metabolism .
-vita mine C is vital structural agent .

5. Fat soluble vitamins ** vitamin A :
has specific function in the retina of the eye .
found only in animal food sources .
deposited in the liver ,kidneys ,lungs , & fat tissue .
found in egg yolk ,liver ,pigment of carrots .

6. absorption of vit A under assistance of :
bile salts so obstruction of bile duct , infectious hepatitis & liver cirrhosis = decrease the absorption of vit A .
pancreatic lipase .
Dietary fat stimulate bile release for effective absorption of vitamin A .
absorption of vitamin A through small intestine to blood stream then to the lymphatic system then to liver 90% stored at liver

7. functions of vitamin A :
has role in visual adaptation to light & dark .
has role in covering epithelial tissue .
reproductive function .
vitamin A deficiency lead to night blindness ,this condition usually cured in about 30 minutes by an injection of vitamin A .
vitamin A is necessary to build & maintain healthy epithelial tissue & act as barrier to infections .
the epithelium include not only the outer skin , but also the inner mucous membrane .

8. without vitamin A the epithelial cells become dry & flat , then gradually harden to form keratin .
keratin is a protein that forms dry scale like tissue , normal in the nail & hair , but abnormal in the skin & mucous membrane .

9. ** deficiency of vitamin A lead to :
eye : cornea dries , blindness .
respiratory tract : dryness of epithelium & cracked of salivary glands .
gastro intestinal system : decrease of mucous membrane secretion affect on digestion & absorption .
genitourinary tract : vaginal infection & dryness of vaginal mucosa ,urinary tract infection ,stone formation .
integmentary function : skin become dry & scaly

10. tooth formation : decrease development of teeth
** N. B : vitamin A is essential for bone growth .
Vitamin A is necessary to support normal sexual maturation during adolescence period .
-sever deficiency of vitamin A lead to sterility

11. ** vitamin A deficiency due to
in-adequate dietary intake .
poor absorption due to lack of bile .
disease of the liver or intestine that obstruct its metabolism & absorption

12. ** hyper vitaminosis: joint pain thickening of long bone loss of hair
jaundice
liver affection ,portal hyper tension & ascites
** source of vitamin A : animal source [ liver ,kidney ,butter egg yolk ]
plant source : green vegetables ,fruit