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Chapter Three The Nail and the Hair The nail is an appendage of the skin. It forms a protective covering for the ends of fingers and toes. A healthy nail is pink in colour with smooth, slightly curved surface and clear of any marks or defects. If the nail matrix is damaged, a deformed nail may grow. The technical term for the nail is onyx. Nail Structure 1. Nail root/matrix - the living part of the nail situated below the cuticle. Mitosis occurs here to produce new nail cells. New cells are pushed forward to form the nail plate. They receive nourishment from blood supply and undergoing mitosis. As they dry out and become keratinised, they push towards the nail plate. 2. Nail plate - Stratum lucidium and corneum. These cells are fully keratinised and dead. There is no blood supply or nerves. It protects the nail bed. It is the visible portion of the nail and terminates at the free edge. 3. Nail bed - Stratum germinativum / spinosum / granulosum. It is a continuation of the root. It is to nourish and protect the nail structure. It has a blood supply and nerve supply. The nail bed has parallel ridges which ‘slot in’ with corresponding ridges on the under surface of the nail plate. 4. Lanula - point where the matrix and the nail bed meet. It is the ‘half moon’ at the base of the nail. Here, cells are so closely packed together that the blood supply below cannot be seen. That is why it is white in colour. 5. Free edge - extension of the nail plate which overlaps the hyponychium. 6. Hyponychium - a portion of skin at the end of the finger underneath the free edge. 7. Cuticle - overlapping epidermis surrounding the nail. It protects the matrix from invasion of bacteria and other damage. Eponychium is the cuticle at the base of the nail. Perionychium is the cuticle at the sides of the nail. 8. Nail walls - folds of skin that overlap the side of the nails. Nail Growth 1. Cells divide in the matrix. 2. Nail grows forward over the nail bed. 3. Translucent and soft cells are present at first 4. As they grow towards the free edge, they become harder and flatter. 5. The top 2 layers of the epidermis form the nail plate. 6. The bottom 3 layers form the nail bed. 7. Interlocking grooves found on surface of nail bed and under surface of nail plate allow the nail to grow in correct direction. 8. It takes approximately 6 months for a finger nail to grow and 12 months for a toe nail to grow from matrix to free edge. www.goldeneggholistic.com Anatomy, Physiology and Pathology notes 20 Hair Structure Hairs are dead structures composed of keratinised cells that are cemented together. They grow out of hair follicles. It has 2 main portions - the Hair Root and the Hair Shaft. The Root 1 Found below the surface of the skin. 2 It includes the hair bulb /matrix, which is an enlarged area of cell division. 3 It includes the dermal papilla, which is an elevation at the hair root providing blood supply through capillaries. It provides nourishment to the dividing hair matrix. 4 Inner root sheath - single layer of keratinised cells that grows up with the hair from the papilla up to the level of the sebaceous gland. It connects with the cuticle cells. 5 Outer root sheath - this forms the follicle wall and does not grow up with the hair. It is a continuation of the basal layer of the epidermis. It is a permanent layer of growth and renewal. 6 Connective sheath - surrounds the follicle and sebaceous gland. It provides the blood and nerve supply to the hair. The Shaft Extends beyond the surface of the skin. It is made up of 3 parts: 1. Cuticle - layer of scales pointing towards the hair tip. Scales are translucent and free of colour. Cuticle cells interlock with the inner root sheath in the follicle. This anchors the hair. It protects the underlying cortex of the hair. 2. Cortex - Bulk of the hair. Many layers of cells with keratin. The pigment melanin is here giving hair its colour. 3. Medulla - inner core of the hair made of soft keratin and pigment. No medulla is present in very fine hair. www.goldeneggholistic.com Anatomy, Physiology and Pathology notes 21 Hair Types Lanugo - Fine soft hair with no medulla. It has no colour. Present in foetus from 3rd - 8th month. Replaced later by vellus hair. Eyelashes and eyebrows and scalp hair is replaced by terminal hair. Vellus - Fine soft hair with no colour. Found on the face and body. It can become terminal hair with hormonal changes. Terminal - Long coarse hair. Coloured and has varying thickness. It has deep follicles and strong bulb. Hair Growth Hair grows in 3 stages of a cycle: Anagen - This is the active stage of hair growth. The follicle forms afresh and the hair bulb develops around the dermal papilla. Hair grows up from the matrix. This stage ends when the dermal papilla stops nourishing the hair. Catagen - The hair separates from the dermal papilla and is carried upwards by the inner root sheath to the level of the sebaceous gland. Hair stays here until it falls out or is pushed out by a new hair. Telogen - This is resting stage of hair growth. At this stage all that is left at the end of the follicle is a thread of germ hair cells that will reconnect to the dermal papilla and start a new hair growth cycle. Hair Shape Determined by the hair follicle Angled or bent follicle will produce an oval (wavy) or flat (curly) hair. Straight follicle will produce a round hair (straight). N. B. During waxing, curly hairs break off easier than straight hairs. www.goldeneggholistic.com Anatomy, Physiology and Pathology notes 22.
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