Skin Structure and Function II PDF

SKIN STRUCTURE AND FUNCTION II Dr. P. De Gabriele MD MMCFD DipWH(ICGP) SKIN COLOUR Melanin – the amount and kind of melanin (yellow, reddish brown or black) in the epidermis Carotene – This is deposited in the stratum corneum and subcutaneous tissue. Oxygen-rich...

SKIN STRUCTURE AND FUNCTION II Dr. P. De Gabriele MD MMCFD DipWH(ICGP) SKIN COLOUR Melanin – the amount and kind of melanin (yellow, reddish brown or black) in the epidermis Carotene – This is deposited in the stratum corneum and subcutaneous tissue. Oxygen-rich Haemoglobin in dermal blood vessels SKIN APPENDAGES They arise from the epidermis. They include: – Cutaneous glands – Hair and hair follicles – Nails - Cutaneous Glands All exocrine glands Formed by the cells of the stratum basale and then push into the deeper skin regions. They ultimately reside almost entirely into the dermis. 2 types of cutaneous glands – Sebaceous glands – Sweat glands - Cutaneous Glands  Sebaceous Glands Found all over the skin, except on the palms of the hands and the soles of the feet Ducts usually empty into a hair follicle but some open directly onto the skin surface. The product of the sebaceous glands is sebum. – When the duct of a sebaceous gland is blocked by sebum, a whitehead is formed. – If accumulated material oxidizes and dries, it darkens and forms a blackhead. Sebum A mixture of oily substances and fragmented cells. It lubricates the skin. It keeps the skin soft and moist. It prevents the hair from becoming brittle. It kills bacteria through chemicals that are present in it.  Sweat Glands Widely distributed in the skin There are 2 types of sweat glands – Eccrine glands – Apocrine glands. - Eccrine Glands Far more numerous than apocrine glands Found all over the body An important part of the body’s heat- regulating equipment. They produce sweat. Sweat An acidic (pH 4 to 6) clear secretion that inhibits bacterial growth It is made up of: – Water – Some salts especially sodium chloride – Vitamin C – Traces of metabolic wastes – ammonia, urea and uric acid – Lactic acid - Apocrine Glands Largely confined to the axillary and genital areas of the body Larger than eccrine glands Not involved in heat regulation Activated by nerve fibres during pain and stress and during sexual foreplay. Their ducts empty onto the hair follicles. They secrete sweat as well as fatty acids and proteins. Secretion – Has a milky or yellowish colour – Is odorless but when the bacteria present on the surface of the skin use its proteins and fats, it takes on a musky unpleasant odour. These glands start to function in puberty under the influence of androgens.  Hair A flexible epithelial structure A hair is formed by the stratum basale epithelial cells in the matrix of the hair bulb at the inferior end of the follicle. The bulk of the hair shaft is dead material and almost entirely protein.  Hair Structure The hair is divided into 2 parts: – Root – the part of the hair enclosed in the follicle – Shaft – the part of the hair projecting from the surface of the scalp or skin Each hair consists of – the medulla – a bulky cortex layer – a cuticle formed by a single layer of cells that overlap one another. Cuticle The cuticle has several functions: – It helps keep the hairs apart and keeps them from matting. – It provides strength to the inner hair layers keeping them tightly compacted. – It is exposed to wear and tear.  Hair Follicles An inner epidermal sheath made up of epithelial tissue and forms hair An outer dermal sheath that is actually dermal connective tissue that supplies blood vessels to the epidermal portion and reinforces it.  Arrector pili - Small bands of smooth muscle cells connect each side of the hair follicle to the dermal tissue When these muscles contract, the hair is pulled upright, dimpling the skin surface with ‘goose bumps’.  Nails A modification of the epidermis It has a free edge, a body and a root. The borders of the nail are overlapped by skin folds called nail folds.