YR1 Lecture 1H - Anatomy of the Skin - Prof John Morley 2019 PDF

Skin Functions of skin Protection Regulation of body temperature Excretion Absorption Reception Classification of Skin Histologically classified as thick or thin Thick skin – palms, soles of feet; lacks hair and sebaceous glands Thin skin – most other parts of the body and usually contains hair (thi...

Skin Functions of skin Protection Regulation of body temperature Excretion Absorption Reception Classification of Skin Histologically classified as thick or thin Thick skin – palms, soles of feet; lacks hair and sebaceous glands Thin skin – most other parts of the body and usually contains hair (thin skin without hair occurs in parts of the genital region, lips and lateral and terminal region of fingers and toes) Regional variation in texture – skin of eyelids soft and thin with fine hair; skin of eyebrow thicker and has course hair; skin of forehead produces oily secretions, skin on chin lacks oily secretion but develops hair Epidermis Surface layer - composed of stratified squamous keratinized epithelium Composed of four cell types: Keratinocytes Langerhans cells Melanocytes Merkel cells Up to five layers: stratum germinativum (basale) stratum spinsosum stratum granulosum stratum lucidum stratum corneum Squamous cell carcinoma Squamous cell carcinoma (SCC) is one of the most common forms of skin cancer, with only basal cell carcinoma (BCC) occurring more frequently. SCC occurs mainly in Caucasians. It starts from cells in the outermost layer of the skin which start to overgrow and potentially spread. SCC is caused mainly by chronic sun exposure. SCC can also start from cells on the lips, tongue, lining of the mouth and genitals. Melanoma Melanoma is a cancer that arises in pigment cells of the skin (melanocytes). If not detected early, it has the capacity to spread through blood vessels and lymph channels to other parts of the body. Fifteen hundred Australians die from melanoma each year. Australia has the highest rates of melanoma in the world. Melanoma is the most common cancer in Australians under fifty years of age and rates continue to increase. At least one in ten men and one in 16 women will develop a melanoma. Early diagnosis is essential to enable treatment before the melanoma spreads and becomes life threatening. Amelanotic melanoma ulceration and associated scabbing https://www.skincancer.net.au/amelanotic-melanoma-pictures/ Dermis Ranges in thickness: ~0.6mm (eyelid) to ~ 3mm (palms, soles of feet) Two layers: Papillary (superficial) layer – dermal papillae, separated from epidermis by basement membrane, collagen and elastic fibres, anchoring fibres from BL of epidermis, capillary loops, Meissner corpuscle Reticular (deep) layer – bundles of collagen fibres, elastic fibres, sweat glands, sebaceous glands, hair follicles, smooth muscle fibres (arrector pili), Pacinian and Ruffini corpuscles in deeper dermis Sebaceous glands - flask shaped, packed solidly with cells - commonly empty into the upper regions of the hair shaft - most numerous on the face, scalp, forehead and upper thorax - absent from the palms and soles of the feet - secrete an oily substance termed sebum (mixture of cholesterol, triglycerides and cellular debris) – holocrine secretion - Serves to waterproof skin, soften skin, maintain hair flexibility Acne vulgaris Acne is a very common skin condition that usually begins in adolescence. The hair follicle and its associated oil (sebaceous) gland become blocked and inflamed. Whiteheads, blackheads and inflamed pus-filled spots develop on the face, neck, back and chest, where oil glands are largest and most active. Main causes acne vulgaris? Hormones. At around 8 years of age, the adrenal glands start to produce androgens (male hormone) and the amount produced gradually increases during puberty. The sebaceous glands respond to androgens by producing more sebum and sometimes whiteheads (closed comedones) may develop in young children. Sebaceous gland blockage. The skin cells lining the upper part of the hair follicle duct are not shed as normal but accumulate and form a plug (comedone). The oil is trapped behind it. Bacteria and inflammation. Increased numbers of acne bacteria (Propionibacterium acnes) accumulate in the duct and contribute to the inflammation that develops in the pimples. Genetics. Hereditary factors contribute, however it is not known exactly how this works. Stress. Adrenal glands produce more androgens when an individual is stressed. This can make acne worse. Sweat glands Sweat glands Eccrine glands: - abundant over body (especially forehead, axillae, palms and soles) - coiled tubular glands with duct that passes through the dermis and epidermis - myoepithelial cells form a margin around the secretory units - sweat initially – water, sodium and potassium ions - at surface sweat is mainly water (ions absorbed by epithelial lining) -sweat is colourless and odourless - used for thermoregulation Apocrine glands - usually empties via a duct connected with a hair follicle - numerous in the axilla, anal region and areola of nipple - embedded in deeper dermis and hypodermis - secretion is viscous, odourless with fluid broken down by bacteria at surface - secretion under influence of hormones and sympathetic nervous system Tactile Receptors in Glabrous Skin Nails