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The Skin

A. melanocyte B. muscle  C. sebaceous gland  D. hair shaft  E. epidermis  F. dermis  G. subcutaneous tissue  H. fat  I. arterial blood vessel  J. sweat gland  K. hair follicle L. Pacinian corpuscle

The epidermis is constantly being renewed as new cells form underneath and are push up pushing the old ones away. Although not obvious here a thin muscle called an erector muscle is read to pull the hair erect. The hair itself is situated in the hair follicle (the hair hole), and the oil/sebaceous gland keeps the hair supple. The skin protects against disease, keeps us warm, keeps water and blood in and is sensitive to stimuli.

The thermoregulatory centre (hypothalamus) takes information from receptors in the brain on blood temperature, and also from the skin to test skin temperature.

When you re too cold – Hairs stand on end to try and trap a layer of insulating air, the blood supply to the skin closes off as vasoconstriction sets in to stop the warm blood losing heat in the cold skin. You also shiver.

When you’re too hot – Hairs lie flat, you sweat in the hope of removing heat in the energy used by sweating, the blood supply to the skin increases so heat can be lost by blood close to the surface (vasodilatation - arterials dilate).

Also See

Here are the other comprehensive GCSE Biology notes by Prometheus:

• Cells
• Breathing
• The Nervous System and the Eye
• The Digestive System
• The Skin
• The Kidneys
• The Circulatory System and Blood
• Diffusion
• Evolution and Selective Breeding
• Genetics - Variation, Mitosis and Meiosis
• Hereditary Traits, Sex Determination and Mutations
• Hormones
• Disease and Drugs
• Plant Biology
• Population Size
• The Greenhouse Effect and Pollution Problems
• The Carbon and Nitrogen Cycles

Comments

• Suitable for: GCSE Biology.
• Written by: Prometheus along with all the other notes linked to above.
• From this thread