Chapter 5: The Integumentary System https://www.youtube.com/watch?v=d-IJhAWrsm0&list=PLF2F5D171DA2715B7

Size of the Integument The integument is the largest system of the body: 16% of body weight 1.5 to 2 m2 in area

Connections to other systems Circulatory system: blood vessels in the dermis Nervous system: sensory receptors for pain, touch, and temperature

Functions of Skin Protects underlying tissues and organs Excretes salts, water, and organic wastes (glands) Maintains body temperature (insulation and evaporation)

Functions of Skin Synthesizes vitamin D3 Stores lipids Detects touch, pressure, pain, and temperature

Parts of the Integument The integument is made up of 2 parts: cutaneous membrane (skin) accessory structures hair, nails and glands

Parts of the Cutaneous Membrane Outer epidermis: superficial epithelium (epithelial tissues) Inner dermis: connective tissues

Skin Structure Epidermis—outer layer Stratified squamous epithelium Outer layers keratinized (hardened by keratin) Dermis Dense connective tissue (beneath thin layer of loose CT)

Layers of the Epidermis Stratum corneum – outer 20-30 layers of dead, heavily keratinized cells Stratum lucidum - thick, hairless, “clear layer” skin of palms and feet only Stratum granulosum – “grainy layer” produces keratin Stratum spinosum – “spiny layer” has an immune response Stratum basale – a.k.a. stratum germinativum; stem cells here give rise to all other epidermal cells. Melanocytes located here.

Thin Skin Covers most of the body Has 4 layers of keratinocytes

Thick Skin Covers the palms of the hands and soles of the feet Has 5 layers of keratinocytes

Keratin, Melanin, and an Amazing Factoid! Keratin – tough, pliable protein; water resistant; gives skin, hair, and nails protective properties Stratum corneum is ‘cornified’ = filled with keratin Cells are shed everyday; stratum basale totally replaces epidermis every 25 – 45 days!!

Melanin – pigment of skin color Produced by melanocytes (usually in stratum basale) Color is yellow to brown to black Amount depends upon genetics and exposure to sunlight Protects skin from sun damage

Dermis – deep to epidermis: 2 layers (has capillaries and sensory neurons) Papillary layer (upper dermal region) Projections called dermal papillae Capillary loops, pressure and pain receptors, fingerprints, made of areolar tissue Reticular layer (deepest skin layer). Made of collagen & elastic fibers. Blood vessels Sweat and oil glands Hair follicles Deep pressure receptors

Damage to the Dermis: Skin Damage Sagging and wrinkles (reduced skin elasticity) are caused by: dehydration age hormonal changes UV exposure

Stretch Marks Thickened tissue resulting from: excessive stretching of skin due to: pregnancy weight gain

Lines of Cleavage Clinically significant: A cut parallel to a cleavage line will usually remain closed and heals with little scarring. A cut at a right angle to a cleavage line will be pulled open as severed elastic fibers recoil and will result in greater scarring.

The skin contains two types of exocrine glands: Sebaceous glands (oil glands): secrete sebum -- inhibits bacteria growth, lubricates and protects hair and skin. Sweat glands: (2 types) apocrine – located in armpits and pubic region, produce a sticky, cloudy, and potentially odorous secretion. Begin secreting at puberty. Mammary glands of the breast are modified apocrine sweat glands, a complex interaction between sex and pituitary hormones controls their development and secretion. merocrine – secrete “sweat” onto the skin, composed of 99% H2O. Found all over the skin, the palms and soles have the highest number per cm2. Cools the skin surface, flushes the surface of the skin.

Hair Produced by hair follicles Consists of keratinized epithelial cells Melanocytes provide pigment

Arrector pili – smooth muscle attached to follicle and papillary layer cause ‘goosebumps’

Nails – heavily keratinized modifications of epidermis Stratum basale in nail matrix responsible for growth, nail itself is mostly dead cells (like hair)

The Subcutaneous Layer Subcutaneous layer (hypodermis): Not part of the skin Composed of loose connective tissue: areolar & adipose tissue. ½ of your fat is stored here Lots of blood vessels, location of hypodermic injections.

Review

Burns – damage from heat, electricity, UV, chemicals

Severity of Burns Burns – damage from heat, electricity, UV, chemicals First-degree burns Epidermis only Red and swollen (typical sunburn) Second-degree burns Epidermis and upper dermis damaged Red with blisters Third-degree burns Entire skin layer destroyed Burn is gray-white or black

Rule of 9’s to estimate burn area.

Skin Cancer Figure 5–6

Skin Cancer – uncontrolled cell division in skin Skin cancer = #1 cancer Basal cell carcinoma – least malignant, most common, (stratum basale) Squamous cell carcinoma – easy cure early, but does metastasize to lymph nodes, (stratum spinosum) Malignant melanoma – most deadly, rapid metastasis to lymph and blood, (melanocytes)

ABCD Rule: detecting malignant melanoma A = Asymmetry – opposite sides don’t match B = Border irregularity – borders not smooth C = Color – one mole, several colors D = Diameter - >6mm (pencil eraser)

Hair and Hair Follicles Figure 4.7c