PHYSIOLOGICAL EFFECT OF ULTRA-VIOLET RADIATION

PHYSIOLOGICAL EFFECTOFULTRA-VIOLET RADIATION

Skin act as a protective layer for the body.

It absorbs most of the UV rays.

It causes damage to the intra-cellular structures.

The penetration depends on the wavelength of UV rays.

CANCER

Long exposure to UVB and UVC to the skin causes effect on DNA and cell replication.

Thus causing carcinogenesis

ERYTHEMA

Damage to the cells

Accumulation of chemical around the blood vessels

Releases histamin like substances

Causes vasodialatation

PIGMENTATIONDevelopes in two days of irradiation

Stimulates melanocytosis to produce melanin

Passed to numerous cells

Forms an umbrella like structure around the nucleus to protect the cell

Reduces penetration of UVB

THICKENING OF EPIDERMIS

The sudden over activity of basal layer of epidermis causes marked thickening of stratum corneum(upto three times). It reduces the penetration of UV.

PEELING

The increased thickness of the epidermis is lost as peeling.

This eventually lowers the skin resistance.

PRODUCTION OF VIT.DIn presence of UV rays 7-dedehydrocholestrol is converted into Vit.D in the skin.

This is important for absorption of calcium and normal growth of bones and teeth.

AGEINGNormal ageing of the skin is accelerate d by absorption of UV rays characterized by :- Thinning of skinLoss of epidermal ridgeLoss of melanocytesDryness of skinWrinking of skin

ANTIBIOTIC EFFECTUV rays helps in destroying the bacterias and other small organisms. And so can be used as to sterilize the surface.

PHOTOSENSITIZATIONThe enhanced response of the skin towards the UV rays is known as photosensitivity.This is usually caused by a chemical which absorbs the rays and transfer the energy to the adjacent molecule in form of photochemical reaction.It may be sometimes deliberately produced in the patients by application of coal tar or by ingestion of substances like psoralen

CONCLUSIONThe acute effects of UV rays are:-Sunburn(erythema)Tanning(melanogenesis)Production of Vit.DTumour formation

THANK YOU