Integumentary System PDF

Integumentary System The integumentary system consists of the skin, hair, nails, the subcutaneous tissue below the skin, and assorted glands. Skin Functions Protection from injury Protection against infection Regulates body temperature Regulates water loss Chemical synthesis...

Integumentary System The integumentary system consists of the skin, hair, nails, the subcutaneous tissue below the skin, and assorted glands. Skin Functions Protection from injury Protection against infection Regulates body temperature Regulates water loss Chemical synthesis Sensory perception Types of Membranes Mucous Membranes Line cavities and tubes that open to the outside Serous Membranes Line body cavities that have no opening to the outside Secrete a watery fluid called serous fluid that lubricates surfaces Cutaneous Membrane – also known as skin Synovial Membranes Form the inner lining of joint cavities Secrete a thick fluid called synovial fluid Skin Layers and Attachment Layer Epidermis Covers internal + external surfaces of body Dermis Inner layer – Contains accessory skin structures Hypodermis or subcutaneous layer Attaches the skin to underlying organs & tissues Thin skin vs. Thick skin Thin - 1-2 mm on most of the body and 0.5 mm in eyelids – Hairy; Covers all parts of the body except palms, soles Thick - up to 6 mm thick on palms of hands and soles of feet; Hairless; Covers palms, and soles  Epidermal Cell Types Keratinocytes - 90 % of epidermal cells are keratinized contains keratin (fibrous protein) protects and waterproofs the skin Langerhans cells - Arise from red bone marrow and migrate to the epidermis - Constitute small portion of epidermal cells -Participate in immune responses Easily damaged by UV light Melanocytes - 8% of the epidermal cells produces melanin contributes to skin color and absorbs UV light Merkel cells - Least numerous of the epidermal cells Found in the deepest layer of the epidermis-Along with tactile discs, they function in sensation of touch  Epidermal Layers Stratum corneum - nuclei and organelles are destroyed by lysosomes and the cells fill with keratin Stratum lucidum - only found in the palms and soles of feet 3-5 layers of clear, flat, dead keratinocytes -Dense packed intermediate filaments Thick plasma membranes Stratum granulosum - cells start to become keritanized --Secretes lipid-rich secretion that acts as a water sealant Stratum spinosum - 8-10 layers of keratinocytes - skin both strength and flexibility Stratum basale - Also referred to as stratum germinatum -where new cells are formed Growth of Epidermis Newly formed cells in the stratum basale undergo keratinazation as they are pushed to the surface and accumulate more keratin during the process Then they undergo apoptosis or death Eventually they slough off and are replaced The process takes about 4 weeks Rate of cell division in the stratum basale increases during injury  Dermis Second deepest part of the skin Composed mainly of connective tissues (collagen and elastic fibers) Papillary Layer – Surface area is increased due to projections called dermal papillae which contains capillaries or tactile receptors -Epidermal ridges conforms to the dermal papillae Reticular Layer -Contains hair follicles, nerves, sebaceous and sudoriferous glands  Hypodermis (Subcutaneous) Attaches the skin to underlying organs and tissues Not part of the skin - lies below the dermis Contains connective tissue and adipose tissues (subcutaneous fat) for insulation Infants and elderly have less of this than adults and are therefore more sensitive to cold Skin Color Skin Color Genetic Factors – Skin pigmentation All humans have the same number of melanocytes How much melanin they produce is controlled by several genes Lack of pigment is called albinism Environmental Factors - Exposure to sunlight Volume of Blood – Hemoglobin in blood Skin Pigments – Melanin Located mostly in epidermis Two types of melanin: eumelanin which is brownish black pheomelanin which is reddish yellow Fair-skinned people have more pheomelanin Dark skinned people have more eumelanin Environmental Factors Affect Melanin Production UV light increases enzyme activity in melansomes increased melanin production Amount of melanin increases + Darkness of melanin = Tan Eumelanin protection from UV radiation Pheomelin breaks down with too much UV Too much UV radiation may cause skin cancer  Other Skin Pigments Carotene yellow -orange pigment precurser of Vitamin A important for vision Found in Stratum corneum and fatty areas of dermis and hypodermal layer Hemoblobin oxygen carrying pigment in red blood cells Skin Markings friction ridges: markings on fingertips characteristic of primates - allow us to manipulate objects more easily- fingerprints are friction ridge skin impressions flexion lines: on flexor surfaces of digits, palms, wrists, elbows etc.- skin is tightly bound to deep fascia at these points freckles: flat melanized patches vary with heredity or exposure to sun moles: elevated patch of melanized skin, of the with hair mostly harmless, beauty marks  Aging Skin In our 20s, the effects of aging begin to be visible in the skin. Stem cell activity declines: skin thin, repair difficult Epidermal dendritic cells decrease: reduced immune response Vitamin D3 production declines: calcium absorption declines and brittle bones Glandular activity declines: skin dries, body can overheat Blood supply to dermis declines: tend to feel cold Hair follicles die or produce thinner hair Dermis thins and becomes less elastic – wrinkles Skin Derivatives During embryonic development thousands of small groups of epidermal cells from stratum basale push down into dermis to form hair follicles and glands Functions – Hair & Nails Functions of Hair Hair on the head protects scalp from injury and sunlight Eyelashes and eyebrows protect eyes Nostril and ear hairs protect from foreign particles Help in sensing light touch due to the touch receptors associated with the hair root plexuses. Functions of the Nails Grasping objects Manipulating objects Protects ends of digits from trauma Scratching Hair Anatomy Shaft: portion of hair that projects from skin surface Root: portion of hair deep to the shaft penetrating the dermis Has 3 layers: medulla cortex cuticle Base of the hair follicle Bulb: houses the papilla which contains the blood vessels that nourishes the growing hair follicle. Matrix: responsible for hair growth and produces new hair Arrector pili: smooth muscle Extends from the dermis to the side of hair follicle. Hair root plexus - dendrites of neurons which are sensitive to touch  Hair Features & Texture About 100,000 hairs are on the scalp Almost every part of body is covered with hair except palms of hands, soles of feet, sides of fingers and toes, lips and parts of genitals Hair shafts differ in size, shape, and color. In the eyebrows they are short and stiff while on the scalp they are longer and more flexible. Over the rest of the body they are fine and nearly invisible Oval shaped hair shafts produce wavy hair, Flat or ribbon-like hair shafts produce curly or kinky hair Round hair shafts produce straight hair. Roughly 5 million hairs cover the body of an average individual Hair Growth Hair follicles grow in repeated cycles. One cycle can be broken down into three phases. Anagen - Growth Phase Catagen – Transitional Phase Telogen - Resting Phase Each hair passes through the phases independent of the neighboring hairs Skin Glands Sudoriferous - sweat glands Eccrine sweat glands -Secretes cooling sweat Appocrine sweat glands - during emotional stress/excitement Sebaceous - oil glands – Acne - inflammation of sebaceous gland ducts Ceruminous - modified sweat glands of the external ear that produce ear wax Nails Made of tightly packed, hard, keratinized epidermal cells Consist of: Nail body: portion of the nail that is visible- Free edge: part that extends past the distal end of the digit Nail root: portion buried in a fold of skin Lunula: means little moon - Crescent shaped area of the nail Hyponychium: secures the nail to the fingertip -Thickened stratum corneum Eponychium or cuticle: narrow band of epidermis-Growth of nails is in the nail matrix. Skin Receptors Heat Cold Light pressure Heavy Pressure Pain Skin Imbalances Skin Leisons Skin Infections Viral as cold sores, herpes simplex, warts (HPV) Bacterial as boils, carbuncles, inflammation of hair follicles and sebaceous glands. Impetigo Fungal as Athlete’s Foot, Tinea Contact Dermatitis Irritant Dermatitis as soaps, detergents, shampoo Allergic Dermatitis as poison ivy, poison oak, rubber gloves, nickel and other medals, fragrances Genetic Disorders Psoriasis chronic, noninfectious skin disease skin becomes dry and scaly, often with pustules and many varieties stratum corneum gets thick as dead cells accumulate often triggered by trauma, infection, hormonal changes or stress Vitiligoa autoimmune pigmentation disorder melanocytes in the epidermis are destroyed (e.g., Michael Jackson) Skin Cancer Very common ABCD Asymmetry Borders Color Diameter Skin Cancer Prevention Use SPF 15 minimum. Wear hats and shirts with sleeves. Wear sunglasses to protect eyes from UV. Avoid tanning beds Skin Cancer Types of Skin Cancer Basal Cell Carcinoma Spread uncommon Very curable if found early Squamous Cell Carcinoma Occurs in parts exposed to the sun Malignant Melanoma Most common in southern hemisphere where the ozone layer is thin Deadly if not caught early!!