Beauty, Hair and Holistic Therapies Anatomy and Physiology The Hair

Welcome to Online learning This slideshow will take you through an introduction to the hair. Click on the hand to begin the presentation

The Hair The hair and nails are both specialised forms of keratin. Both are produced by living cells, but the body of the nail and the shaft of the hair are dead structures. Hair varies in length, colour and thickness on different parts of the body and on different people.

an electron microscope The Hair The hair is formed by cells at the base of the hair follicle and is found all over the body except the palms of the hands and the soles of the feet. Hair is important for protecting the body against friction and preventing particles like dust entering the eyes, nose and ears. The hair seen under an electron microscope

Structure of a Hair The visible part of the hair is called the shaft, it is formed from keratin and is composed of dead tissues. The hair root is found below the surface of the skin and at its base is the hair bulb where the cells divide to make the hair grow. The hair bulb is whiter in colour and softer than the hair shaft. The hair is nourished at the base of the bulb by a clump of blood vessels called the dermal papilla. Shaft Root Bulb

Inside the hair there are three layers, the cuticle, cortex and medulla. The cuticle is the outer layer and is made up of overlapping scales. The middle layer is the cortex and is made up of keratinised cells and melanin which gives the hair its colour. The innermost medulla also contains keratinised cells, but they are not so closely packed together.

Hair in its Follicle

The Hair Follicle This is a tunnel-like segment of the epidermis that extends down into the dermis. The follicle is made up of a thin layer of cells with a bulb at the bottom. Every hair is nourished by a tiny network of blood vessels called the dermal papilla. The cells of the follicle are actually nourished by the connective tissue sheath The hair follicle also contains a sebaceous gland and an erector pili muscle. To diagram

Connective Tissue Sheath This surrounds the hair follicle and sebaceous gland. It supplies the follicle with nerves and blood and is the main source of nourishment for the follicle.

Outer Root Sheath This is continuous with the basal layer of the epidermis and is the permanent source of hair growth cells. The cells are called germ cells.

Inner Root Sheath It originates from the dermal papilla at the base of the follicle and grows upwards. The inner root sheath shapes and contours the hair and holds it firm in the hair follicle.

Hair Bulb The bulb is the enlarged part at the base of the hair root. It is responsible for the production of hair cells and contains melanocytes which will produce melanin and give the hair its colour.

Matrix This is the lower part of the hair bulb and is the area where the hair germ cells divide to produce the hair.

Dermal Papilla This is the area at the base of the bulb. It is made up of blood vessels and is the crucial source of nourishment for the hair.

Sebaceous Gland The sebaceous gland lies next to the hair follicle and is connected by a short duct. It secretes sebum into the hair follicle providing a lubricant for the skin and hair. Sebum keeps the skin pliable and the hair glossy. Sebum is also able to kill certain forms of bacteria and so has a protective function. To diagram

Arrector Pili Muscle This tiny muscle is attached to the side of the hair follicle. When a person is cold or afraid these muscles contract, making the hair stand on end and bunching the skin around the hair shaft to form what are known as goose pimples To diagram

Keratin Keratin is a tough fibrous protein found in the epidermis, hair and nails. Its strength helps to protect the hair from damage. Keratin is what makes the hair strong.

Hair Growth The hair grows from an area in the bulb called the matrix. The cells divide and are pushed upwards away from the dermal papilla and so lose their source of nutrition. The cells then die and are converted to keratin to produce a hair. These cells are amongst the most rapidly dividing of the body.

Hair Growth Cycle There are three stages of hair growth. The active growing stage is anagen where the cells divide and pass up the follicle to become a hair. The second stage is catagen, the hair cells stop dividing and the dead hair moves up the follicle ready to be shed. The final stage is telogen, here the follicle rests in preparation for a new replacement hair to begin growing. To diagram

Hair Growth Cycle

Melanin Melanin is produced in the hair bulb by specialised cells called melanocytes. These cells release the pigment into the hair. Melanin is responsible for the colour of our skin and hair and helps to protect the skin from the damaging rays of the sun.

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