VITAMIN A VITAMINS AN INTRODUCTION 13 Vitamins are

VITAMIN - A

VITAMINS – AN INTRODUCTION. • 13 Vitamins are necessary for health. • 4 of them – A, D, E, K are fatsoluble. • The remaining are watersoluble [ B, C ]. • Fat – soluble vitamins are more readily stored in the body but

VITAMIN - A • Group of fat- soluble compounds , that include RETINOL , RETINAL and RETINOIC ACID. RETINOL: Transport form and Storage form (Retinol ester)

SOURCES ANIMAL SOURCES PLANT SOURCES CAROTENOIDS

METABOLISM Bile and pancreatic enzymes. PERISINUSOIDAL STELLATE CELLS.

FUNCTIONS. • Maintaining normal vision in dim light. • Differentiation of specialized epithelial cells , mainly mucus secreting cells. • Enhancing immunity. • Photoprotective and Antioxidant agents.

1. Visual process: Retina Rods and Dim light Rhodopsin most light sensitive. Cones. Bright light Vit. A containing pigme nts. 3 iodopsins each sensitive to a specific colour.

Synthesis: Retinol all – trans- retinal 11 - cis- retinal Produces a visual signal. Rhodopsin Photon of light Nerve impulse is generated and transmitted by neurons.

2. Differentiation of mucus secreting epithelium:

3. Host-resistance to infections: • Stimulates the immune system by unknown mechanism. • Diarrhoea Maintenance and restoration of the integrity of the Gut epithelium. • Pre school children with measles Decreases mortality and complications like eye damage and blindness.

DEFICIENCY STATES. POOR NUTRITION OR FAT MALABSORPTION. (Celiac disease, colitis) 1. Ocular lesions 2. Cutaneous lesions 3. Other lesions.

v. Ocular lesions: 1. NIGHT BLINDNESS (impaired vision in reduced light).

2. XEROPTHALMIA (dry eye) – 1. xerosis conjunctivae : squamous keratinized epithelium

2. Bitot spots: build up of keratin debris in small opaque plaques.

3. Keratomalacia softening and destruction of cornea 4. Total blindness

v. Cutaneous lesions: Papular lesions giving toad-like appearance. (XERODERMA).

v. Other lesions. Replacement of epithelium in upper respiratory tract and urinary tract. Loss of mucociliary epithelium Pulmonary infections. Keratin debris Renal and bladder Stones. v IMMUNE DEFECIENCY higher mortality for measles, pneumonia and infectious diarrhoea.

VITAMIN-A TOXICITY • ACUTE: Gerrit de Ver in the Arctic - polar bear liver

Signs and symptoms: • • Headche Dizziness Vomitting Blurred vision. Like brain tumour.

Chronic toxicity • • • Weight loss Anorexia Nausea and vomitting Bone and joint pain. Increased osteoclasts------high risk of fractures. Synthetic retinoids – treatment of acne – TERATOGENIC.

October 9 , 2017. THANK YOU