Protection- mechanical, chemical, bacterial Body temperature regulation Prevent water loss Metabolic- synthesize vitamin D Cutaneous Sensation Blood reservoir Excretion Prevent UV damage

An organ, cells constantly dying and being replaced Facts: Weighs 9-11 lbs s.a. = 1.5-2m 2 1 cm 2 has 70 cm blood vessels, 55 cm nerves, 100 sweat glands, 15 oil glands, 230 sensory receptors New skin produced in days

Keratinocytes (90%)- waterproofs & protects skin, nails, hair, stratum corneum Melanocytes (8%)- produce melanin Merkel Cells- slow mechanoreceptors Langerhans’ Cells- immunological defense

Stratum Corneum Stratum Lucidum Stratum Granulosum Stratum Spinosum Stratum Basale- (Germinativum)

Dermis

papillary dermis reticular dermis

a. Cellular Fibroblasts (synthesize collagen, elastin, and reticulin), histiocytes, endothelial cells, perivascular macrophages and dendritic cells, mast cells, smooth muscle, and cells of peripheral nerves and their end-organ receptors. b. Fibrous Collagen & reticulin - provide tensile strength Elastic fibers- provide for restoration of shape after a deformation c. Ground substance glycosaminoglycans: hyaluronic acid, chondroitin sulfate, and dermatan sulfate.

This layer contains adipose tissue and serves to attach the dermis to its underlying tissues. Hypodermis

Some variations in human skin color (Sub-Saharan African, Indian, Southern European, and Northwest European) Melanin Pigments: Eumelanin: Phaeomelanin > Eumelanin: Phaeomalanin- darker skin and hair color; < Eumelanin: Phaeomalanin- lighter skin and hair color Skin color due to: Melanin, Carotene & Hemoglobin

I -light skinned, burns easily, never tans II - light skinned, burns easily, tans some III - light skinned, burns occasionally, tans well IV - light skinned, tans well, rarely burns V - brown skinned (Asian, Indo-Asian, Chinese, Japanese), tans well, burns rarely, can sunburn after prolonged exposure to UVR VI - black skinned (Afro-Caribbean), deeply pigmented, can burn after prolonged exposure to UVR 25% US pop Human complexions are generally classified into six skin types:

Three layers of the hair in cross- section from inside out Hair cuticle cortex medulla Hair shaft cross-section

Structure of Hair and Follicle Color – due to pigment granules in the cells of the cortex brown and black hair high levels of eumelanin red hair – low eumelanin but a high pheomelanin blond hair intermediate amount of pheomelanin ; very little eumelanin Gray and white hair scarcity or absence of melanin in the cortex and the presence of air in the medulla Texture – related to differences in cross-sectional shape straight hair is round wavy hair is oval curly hair is relatively flat

Cyanotic Jaundice Erythema Pallor

Cyanotic Jaundice Erythema Pallor

Pigmentation levels usually increase with age. - exception: premature graying Normal pigmentation may be altered by genetic defects or by acquired diseases. -Hyperpigmentation- age spots -Hypopigmentation- vitiligo, albinism

External agents can also alter skin color. lightening agents carotene dyes Some internal compounds--such as the byproducts of hemoglobin metabolism--may color the skin. Sunless tanning

Sweat Glands Eccrine (merocrine) glands- sweat Apocrine glands- axillary & anogenital areas Ceruminous glands- ears canal Mammary glands- female reproductive glands Ceruminous glands Sweat glands

Sebaceous

Sebaceous (oil) glands Entire body except palms and soles Produce sebum by holocrine secretion Oils and lubricates

Sweat glands Entire skin surface except nipples and part of external genitalia Prevent overheating 500 cc to 12 l/day! (is mostly water) Humans most efficient (only mammals have) Produced in response to stress as well as heat

Types of sweat glands Eccrine or merocrine –Most numerous –True sweat: 99% water, some salts, traces of waste –Open through pores Apocrine –Axillary, anal and genital areas only –Ducts open into hair follices –The organic molecules in it decompose with time - odor Modified apocrine glands –Ceruminous – secrete earwax –Mammary – secrete milk

Hair shaft Hair bulb in follicle

Nail

Malignant melanoma 2% of all cancers Risks: 1.Skin type 2.Sun exposure 3.Family history 4.Age 5.Immunological status A= asymmetry B= border C= color D= diameter Normal mole Melanoma

Burns 1 st -degree (epidermis only; redness) 2 nd -degree (epidermis and dermis, with blistering) 3 rd -degree (full thickness, destroying epidermis, dermis, often part of hypodermis)

Skin replacement:

Blood vessels dilate WBC & clotting agents released Scab forms

Granulation tissue forms Capillary beds invade clot Clean up begins

Scar area has contracted Epithelium regeneration begins

1.In which lay of skin are blood vessels located? 2.Where does epithelium regeneration begin? 3.What color is a persons skin if they are cyanotic? 4.List the layer of the epidermis in order from top to bottom. 5.What is the primary tissue of the hypodermis?