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Hair erector muscles

Tiny muscles which pull the hairs in the skin upright.

Subcutaneous layer

The lowest layer of the skin made up mainly of insulating fat cells.

Sebaceous gland

Glands in the skin around the hair follicles which produce oil to remove dust and bacteria and to help waterproof the skin. The gland opens onto the top of the hair follicle

Hair follicle

Pits in the epidermis of the skin which grow hairs.

Cell division

The process by which a parent cell divides into two daughter cells

Blood vessels

The tubes through which blood is carried around the body eg arteries, veins and capillaries

Sweat glands

The glands which form and release sweat to cool the body as the core temperature rises.


Very small blood vessel with walls made of a single layer of epithelial cells. Exchange of materials, such as nutrients, oxygen and carbon dioxide, takes place between the blood and the cells of the body across the capillary walls.


The outer layer of the skin. Cells in the lower epidermis divide constantly. As they move up towards the surface, the cells flatten and develop tough keratin fibres. Then they die and flake off.


The action of one surface rubbing against another.


Dark brown or black pigment found in the skin, hair and irises of the eyes. The skin produces more melanin when exposed to the sun.


A fibrous protein from which, for example, hair is made.


A layer of connective tissue containing capillaries, sensory nerve endings, lymphatic vessels, sweat glands and hair follicles.


A group of cells in an organism that are specialised to work together to carry out a particular function.


A bundle of neurones - it may be all sensory neurones, all motor neurones or a mixture of both

Skin structure and function

The structure of the skin

The skin is a very important organ. It is a waterproof barrier over the surface of your body, it keeps out infection, it protects the delicate tissues underneath and it can repair itself if it is damaged.

In homeostasis, the skin plays a very important part in maintaining the body temperature within narrow limits. It is important both for losing heat when your core temperature goes up and for conserving heat if your core temperature starts to fall. The structure of the skin is very well adapted to its function in temperature control.

Structure of the skin

The skin has three main layers - the epidermis, the dermis and the subcutaneous layer.

Layers of the skin

The epidermis is on the outside. This has a basal layer which is always forming new cells through cell division so the epidermis is made up from layers of cells. The new cells gradually move towards the surface, which takes 1-2 months. As they move up they gradually die, become flattened and develop keratin. The outermost layer of the epidermis is made of flat dead cells which are continually worn away by friction. The keratin and oil from the sebaceous glands help to make the skin waterproof.

The dermis is the middle layer. It contains

  • Connective tissue - packs and binds the other structures in the skin.
  • Elastic fibres - make the skin stretchy and resilient.
  • Capillaries - tiny blood vessels which are supplied by arterioles.
  • Hair erector muscles - to move the position of the hairs.
  • Sensory cells - these respond to sense touch, pressure, heat, cold and pain.
  • Nerve fibres - to activate muscles and glands and relay messages from the sensory cells to the brain.
  • Pigment cells which produce melanin - a very dark pigment.
  • Sweat glands which open onto the surface as pores.
  • Hair follicles - pits in the epidermis which grow hairs.
  • Sebaceous glands - produce oil to keep hair follicle free from dust and bacteria, and to help to waterproof the skin.

The subcutaneous layer is the final layer of the skin. This is a layer of fat found in the lower part of the dermis and underneath it. The thickness of this layer varies depending on the place in the body and from person to person. A store of fat is useful to the body as insulation and it can be used for energy when the intake of nutrients is insufficient.

Skin section

A simple section through the skin

Question 4

Quiz Print
Where, in the skin, are the cells which divide to form new cells?
What eventually happens to the cells of the epidermis?
Name the structures in the dermis which move the hairs?
Name the structures in the dermis which produce oil?
Name three other structures found in the dermis?