The Integumentary System – Skin! Steve Bradley Machin L. Norris Poudre High School Anatomy and Physiology INTEGUMENTARY SYSTEM Structure - Epidermal layer, Dermal layer, Subcutaneous layer Functions A. Regulation of body temperature – sweat, vessels dilate for heat loss/heat retention through vessel constriction B. Protection – keeps water and other molecules in, keeps water and undesirable substances out C. Sensation – detect pain, pressure, temperature, touch D. Excretion – elimination of some nitrogenous waste, excess salt, water (sweat/perspiration E. Immunity - macrophages F. Synthesis of Vitamin D – sunlight hits skin cells, cholesterol is converted to precursor molecule that aids in absorption of Ca and P EPIDERMIS – Stratified squamous epithelium, first layer of skin Cell Types: a. KERATINOCYTES – in all five layers, more on the outside, make keratin, sealing cells b. MELANOCYTES – Produce melanin c. LANGERHANS CELLS – macrophages d. MERKEL CELLS – sensory cells First Layer of the Integumentary System Epidermis Five layers of Strata from deepest to most superficial a. Stratum Basale – (Germinativum) – deepest, single layer of cells, only layer to undergo mitosis (millions of new cells daily) receives adequate nourishment, contains few keratinocytes, melanocytes, Merkel cells, as are pushed out become more keratinized, new turnover every 35-45 days b. Stratum Spinosum contains keratinocytes, Langerhans cells arise in the bone marrow and migrate receives nourishment several layers thick does not divide c. Stratum Granulosum – 3-5 layers of flattened keratinocytes = water repellent last living layer, receives nourishment everything beyond this layer is dead d. Stratum Lucidum Few layers of dead keratinocytes Found only in thickskinned areas (pads of feet, palms of hands, calluses – no hair e. Stratum Corneum 20-30 layers thick of dead keratin-filled cells, protects against abrasion and penetration, water proof Second Layer of the Integumentary System Dermis 1. Cells of dermis – fibroblasts, macrophages, adipocytes. 2. Thick – palms, soles/Thin – scrotum, eyelids 3. Dermal Papillae – produce fingerprints, contain tactile receptors called “Meissner’s Corpusles.” These are nerve endings sensitive to touch. Dermis cont. 4. Lower Region of the Dermis a. Consists of dense, irregular connective tissue containing collagen and elastic fibers, adipose tissue, hair follicles, nerves, oil glands, and the ducts of sweat glands. b. These fibers give skin it’s strength! Extensibility – ability to stretch (ex. Neck, Elbow “chickenskin!”) Elasticity – the ability to return to it’s original shape after extension or contraction (ex. Pregnancy, Tissue swelling) c. Lamellated Corpuscles – a subcutaneous layer that is sensitive to pressure Skin Color and Pigmentation A. Pigments 1. Melanin – pigment in the epidermis 2. Carotene – pigment in the dermis 3. Hemoglobin – pigment in the RBC’s ( passes thru capillaries in the dermis) Albinisim – the inability to produce melanocytes 1. Inherited through parents via an altered copy of genes that does not allow the body to make the usual amount of a pigment called melanin. 2. Melanin is a dark compound that is called a photoprotective pigment. 3. Major role of melanin is to absorb the UV light that comes from the sun so that the skin is not damaged. * (see diagram 6 and 7 for inheritance) Albinism (cont.) 4. Common eye problems resulting from albinism a. Nystagmus – an involuntary movement of the eyes back and forth (stand up and spin, then watch eyes. diagram 1) b. Photophobia - sensitivity to light but, it does not limit albinos from going out into the sunlight! c. Strabismus – the eyes do not fixate and track together, but they do have some depth perception d. Iris color – usually blue/gray or light brown. The reddish reflection comes from the retinaon the inside of the eye. (diagram 1). e. Unusual patterns of sending nerve signals from the eye to the brain (diagram 3) Malignant Melanoma 1. Melano = dark colored; oma = tumor 2. Cancer of the Melanocytes 3. Due to the repeated exposure of ultraviolet radiation – amount of darkness of melanin increases. Tanning Beds (=) Stupid Idea!!! Accessory Organs of the Skin – develop from the embryo of the developing fetus. Hair – Protect the body Glands – help regulate the body Nails – protect the body Hair 1. Primary function is protection, guards the scalp from injury and the suns rays. a. Eyebrows and Eyelashes – protect the eyes from foreign particles. b. Nostril hair – protects against inhaling insects and foreign particles. Hair - Composition Hair is Keratinized cells, that consist of a shaft and a root. a. SHAFT – projects above the surface of the skin. b. ROOT – below the surface that penetrates into the dermis and into the subcutaneous layer. c. HAIR FOLLICLE – composed of two layers of epidermal cells : External and Internal root sheaths surrounded by a connective tissue sheath. Anatomy of the Hair Follicle: More Hair Composition!!! d. BULB – onion shaped structure, contains papilla of the hair, which have many blood vessels and provide nourishment for the hair. e. MATRIX – included in the bulb, produces new hairs by cell division when older hairs are shed. Growth cycles of the hair. a. GROWTH STAGE – Cells of matrix differentiate Keratinization Death *New cells are added at base of root making the hair grow longer. b. RESTING STAGE – Growth of the hair stops, innactive matrix and shortening of hair follicle. c. NEW GROWTH CYCLE – *New hair replaces old hair and old hair is pushed out of the growth cycle. Thought you were done…..Nope! Melanin –hair color is due to melanin (brown, black, blonde). **FYI – decreased melanin production and increased air in the hair shaft produces grey and white hairs. “Canadian” Goosebumps! – due to the contraction of the arrector pili, under stresses of froght and cold which pull hairs into a verticle position. Glands 1. Sebaceous Oil Glands – secreting portion lies in the dermis and open into the necks of hair follicles or directly onto a skin surface. *no sebaceous glands on the palms or soles a. Sebum – oily secretion that …. - Keeps hair from drying out - Prevents excessive evaporation of water from skin - Keeps skin soft - Inhibits the growth of certain bacteria Glands Again! BLACKHEADS – accumulated sebum and enlargement of sebaceous glands in face. PIMPLES – sebum acts as a nutrient to bacteria – that’s why you get the yucky puss out of them! Glands – almost……. 2. Sudoriferous (Sweat) Glands – Two types a. APOCRINE SWEAT GLANDS a. armpit, pubic region, and areolae of breasts. b. produce sticky viscous secretion b. ECCRINE SWEAT GLANDS – more watery secretion during emotional stress or “cold sweat.” a. not found in lips, nail beds, labia minora, glans penis, and eardrums. b. Palms and soles!! Bad Odor (BO) Perspiration or Sweat (comes from the eccrine) – functions to…. - Help regulate body temperature - Elimination of wastes *Antiperspirants v.s. Deodorants “The Last of the Sweat Glands” 3. Ceruminous Glands – located in the outer ear canal. a. EAR WAX = cerumen (cera = wax) *a combination of ceruminous secretions and sebaceous glands b. HAIRS + EAR WAX = provide a sticky barrier against foreign bodies. Nails 1. Structure - Plates of tightly packed, keratinized cells of the epidermis. a. NAIL BODY – visible portion of nail (PINK PART) b. FREE EDGE – part that extends past the end of the finger or toe. c. NAIL ROOT – non-visible portion d. LUNULA – thickened, whitish semilunar area Near the nail root and cuticle 2. Growth of the nails a. Occurs by transformation of superficial cells of the nail matrix into nail cells. b. Growth slower in toenail. c. The longer the digit the faster the nail grows d. The more the had used, the faster the hand nail growth. e. Nails help us grasp and manipulate objects and provide a protection against damage to the fingertips.