VITAMIN A IN GENERAL

                                      Vitamin A

Vitamins are organic compounds required in tiny amounts for essential metabolic reactions in a living organism. Absence or deficiency of vitamins causes various biological disorders.

VitaminA comes under category of Fat Soluble Vitamin which are stored in natural body fat reservoir .

Functions of vitaminA

1. Synthesis of glycoprotein to maintain structure of epithelial cells
2. In bone formation synthesis of mucopolysacharides
3. Synthesis of the visual pigment Rhodopsin
4. Retinol and retinoic acid (RA) are essential for embryonic development during fetal development.

Symptoms show due to deficiency of Vitamin A are: 

Mild vitamin A deficiency may result in changes in the conjunctiva (corner of the eye) called Bitot's spots.

Severe or prolonged vitamin A deficiency causes a condition called xerophthalmia (dry eye)

Xerophthalmia is characterized by changes in the cells of the cornea that ultimately result in corneal opacity, keratinization of the cornea, corneal ulcers, scarring, and blindness

Vitamin A is needed for bone formation.
If vitamin A is deficient optic foramen is not formed properly.

Small size optic foramen leads to the constriction of optic nerve.
Vitamin A is involved in the formation and protection of epithelial cells.
Damage to epithelial cells can cause easy entry of pathogenic microbes leading to infection.
So infection of gastrointestinal tract, respiratory tract, urogenital tract and skin is common in Vitamin A deficiency

As vitamin A helps to prevent these infections it is called anti infective vitamin.

Vitamin A is commonly known as the anti-infective vitamin, because it is required for normal functioning of the immune system.
The skin and mucosal cells (cells that line the airways, digestive tract, and urinary tract) function as a barrier and form the body's first line of defense against infection

Vitamin A is essential for normal bone formation as it is involved in the synthesis of mucopolysacharides needed for laying down of the bone matrix.Hence a deficiency of vitamin A can lead to developmental bone deformities.

Normal levels of vitamin A are required for sperm production.

Similarly, normal reproductive cycles in females require adequate

availability of vitamin A.

deficiency of vitamin A can lead to infertility or sterility in male.

deficiency of vitamin A can lead to vaginitis, abnormal menstrual cycle, early embryonic mortality, abortion and defective formation of foetus in females.

One of the initial effects of vitamin A deficiency is elevated cerebrospinal fluid (CSF) pressure.

The mechanism whereby the increase in CSF pressure is brought by thickened duramater leading to under absorptions of CSF.

Toxicity of VitaminA

The condition caused by vitamin A toxicity is called

hypervitaminosis A.

It is caused by over consumption of vitamin A.

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Symptoms include nausea, headache, fatigue, loss of appetite, dizziness, and dry skin.