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1、皮膚的構造與功能,高榮皮膚科主治醫師 陳雅惠,Look at your skin,More than a covering A vital organ, complex structure Develop from the same tissues as the brain,Skin facts,Surface area: about 2500 cm in a newborn baby, 18000 cm in an adult. About 6-16% of body weight: average 3 kg in a woman, perhaps 5 kg in a man. thickn
2、ess: varies on sites. thinnest on the eyelids and thickest on the palms and the soles.,Three layers: epidermis, dermis, subcutaneous fat,Epidermis-2,All keratinocytes originate from basal layer Move upward,change shape and loss nucleus, produce skin protein (keratin) and fat (sphigolipid, ceramide)
3、Corneocytes: dead Resist to injury keep water,Epidermis-2,Desquamation (squames) Renew cycle: about 30 days Psoriasis: 4-7 times faster Speed up: sunburn, peel aging,Epidermis-3,A model of “bricks and mortar” Corneocytes, desmosomes, natural fat up to 15% of the stratum corneum consists of water. TE
4、WL (transepidermal water loss),Dermis,3000 m thick, keep resilience and supple Contain blood vessels, nerves, hair roots and sweat glands Fibroblasts make collagen and elastin Ground substance: glycoprotein (hyaluronic acid, chrondroitin sulfate), maintain water,Dermis-2,Collagen: 75% Elastic fibers
5、: Elastin, 5% Stretch marks Wound repair Across lines, deep, large Granulation tissue Hypertrophic scar Keloid,Subcutaneous fat layer,Adipocytes, larger vessels and nerves Depth differs from site and individual Cushing, conserve body heat store fat: women (buttocks and thighs), men (abdominal wall)
6、cellulite,Sebaceous glands,Part of hair follicles in every part except palm and sole Sebum: pH= 4.2-5.6, protect skin and lubricate hair shaft Mixture of sebum and sweat: natural oil-in-water emulsion, kill some fungi Influence by male hormone most sensitive at puberty on face and trunk,Eccrine glan
7、ds,Empty directly on to the skin in every part except lips and glans penis Produce sweat: mixture of water and salts Regulate the body temperature Remove waste,Apocrine glands,In axillary and genital area, breast Decapitation secretion Dependent on sex hormone Germs grow in moist area produce body o
8、dor,Hairs,Vellus hairs: most skin, attached to tiny muscles in the dermis, “goose bumps” Terminal hairs: scalp, eyelids, eyebrows, Beard, chest, arm and leg: due to male hormone Cuticle, cortex, medulla,Blood vessels,Supply the skin and appendages Regulate body temperature Sympathetic nerve make it
9、constriction; parasym. nerve, dilatation.,Nerves,Autonomic nerves: vessels, sweat glands, smooth muscles Sensory nerves Subepidermal plexus Merckel plexus,Functions of the epidermis,protecting the body from the environment, particularly the sun preventing excessive water loss from the body protectin
10、g the body from infection.,Functions of the epidermis-1,ultraviolet radiation create free radicals protecting the nuclei of the cells in the epidermis and the collagen of the dermis Part is reflected by the stratum corneum at the skin surface part is absorbed by the melanin in the epidermal cells so
11、me is scattered within the skin,Functions of the epidermis-2,Water: 70-75% of the weight of the basal layer, but only 10-15% of the stratum corneum. If below 10%, it becomes dry, less flexible and prone to damage, breakdown and infection. The epidermis as a whole is about 35m thick when dry, swell t
12、o 48 m on full hydration.,Functions of the epidermis-3,Hydration components of Stratum component 1. Keratin 2. a cornified envelope of corneocytes 3. Lipids Linoleic acid (diet), ceramides 4. natural moisturising factors (NMF) Amino acids (40%), pyrrolidone carboxylic acid (12%), lactic acid (12%),
13、urea (8%), salts (18%), unidetified compounds (10%) 5. desmosomes 6. enzymes,Functions of the epidermis-4,Three level against invasion by microorganism Natural layer of oil-in-water emulsion on skin Stratum corneum White blood cells in skin Defense concerns chemicals Langerhans cells semipermeable,F
14、unctions of the dermis,protection to the body from bumps and knocks provide oxygen and nutrients remove waste products of metabolism from the epidermis, which are also carried away in the blood provide shape and form to the body, by holding all its structures together contributing to skin color, particularly in people with little melanin in the epidermis Organs in the dermis have special functions of their own: regulation of body temperature through control of blood flow and sweating skin sensations of touch, pain, heat and cold,
