THE INTEGUMENTARY SYSTEM The Skin and its Appendages

Functions of the Skin PROTECTION – from injury, chemicals, temperature, and bacteria PREVENTS water loss by producing KERATIN – a water proofing protein REGULATES body temperature EXCRETES excess water and salt PRODUCES vitamin D SENSES our environment

STRUCTURE OF THE SKIN EPIDERMIS – outer layer composed of stratified squamous epithelium DERMIS – located directly below the epidermis – composed mostly of dense connective tissue SUBCUTANEOUS or HYPODERMIS – located below the dermis – composed mostly of adipose tissue

STRUCTURE OF THE EPIDERMIS COMPOSED OF FIVE LAYERS (STRATA) Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale

EPIDERMIS LAYERS (STRATA) STRATUM BASALE Receives the most adequate nourishment because it is closest to the dermis Constantly undergo mitosis Daughter cells are pushed upward closer to the skin’s surface and away from nutrition Also called stratum germinativum

EPIDERMIS LAYERS (STRATA) STRATUM SPINOSUM and STRATUM GRANULOSUM Cells become increasingly flat and full of keratin. STRATUM LUCIDUM layer in which cells die – only found where skin is hairless and extra thick – palms of hand and soles of feet

EPIDERMIS LAYERS (STRATA) STRATUM CORNEUM 20 to 30 cell layers thick Cells are completely dead and fully keratinized Creates hard layer that protects cells underneath Average person loses 40 lbs. of this layer in their lifetime! Replaced by cells of stratum basale every 25 – 45 days.

MELANOCYTES Specialized cells found primarily in the stratum basale Produce the pigment known as MELANIN – ranges in color from yellow to brown to black Production is stimulated by sunlight Freckles and moles are seen where melanin is concentrated in one area. Melanin production is genetically determined.

STRUCTURE OF THE DERMIS PAPILLARY LAYER Upper dermal region Has projections called PAPILLAE which indent the epidermis above Papillae of hands and feet are arranged in definite patterns – these form fingerprints Layer that houses touch ( Meissner’s corpuscles) and pain receptors (free nerve endings) Papillary layer

STRUCTURE OF THE DERMIS RETICULAR LAYER Deepest skin layer Contains blood vessels, sweat, and oil glands Has deep pressure receptors called Pacinian corpuscles Contains collagen which gives skin its strength Contains elastic fibers which give skin elasticity or “stretchiness” Reticular layer

SKIN COLOR PIGMENTS Amount of MELANIN – ranges from yellow to brown to black Amount of CAROTENE – a yellow-orange pigment found in foods like carrots – the body deposits it in stratum corneum and subcutaneous layer Amount of HEMOGLOBIN – blood pigment that shows through from the dermal capillaries

SKIN APPENDAGES SEBACEOUS GLANDS Produce oils (sebum) that keep skin moist and soft Prevent hair from becoming brittle Sebum contains chemicals that kill bacteria Sebaceous gland

SKIN APPENDAGES SWEAT(SUDORIFEROUS) GLANDS ECCRINE sweat glands secrete primarily water and empty from pores distributed on the body’s surface APOCRINE sweat glands are primarily in the axillary and genital regions and secrete into hair follicles – associated with body odors Sweat glands

SKIN APPENDAGES HAIR Produced by an EPIDERMAL structure called the hair FOLLICLE Composed of three layers: medulla, cortex and cuticle The cuticle is formed by highly keratinized, dead epithelial cells. The arrector pili muscle attached to the hair follicle are the cause of “goose bumps” Hair Structure Medulla (core) Cortex Cuticle

SKIN APPENDAGES NAILS Modification of the epidermis having a free edge, body (visible attached portion) and root (embedded in skin) Heavily keratinized and colorless – appear pink because of blood supply below. Grows from the nail bed or matrix

BURNS BURN – damage or cell death caused by heat, electricity, radiation, or chemicals 1st Degree – only the epidermis is damaged 2nd Degree – damage the epidermis and upper region of the dermis – blisters are likely 3rd Degree – entire thickness of the skin is destroyed – regeneration isn’t possible – skin grafts must be done to replace damaged tissue

SKIN DISORDERS ATHLETE’S FOOT – itchy, red, peeling condition between toes – caused by a fungus COLD SORES – fluid filled blisters that itch and sting – caused by herpes simplex virus – activated by upset, fever, or UV light PSORIASIS – chronic condition producing too many skin cells – believed to be an autoimmune condition in which the immune system attacks a person’s own tissues. ACNE – condition caused by over-production in the sebaceous glands – prevalent in teens because of hormonal changes

SKIN DISORDERS SKIN CANCERS Basal Cell Carcinoma – least malignant and most common – appear as lesions in areas that have been exposed to a lot of sun – relatively slow growing Squamous Cell Carcinoma – appears as a scaly, red lesion – eventually forms an ulcer on the surface of the skin – appear most often on scalp, ears, and lips – also believed to be sun-induced.

SKIN DISORDERS SKIN CANCERS Melignant Melanoma – begins wherever there is pigment – appear spontaneously or where there is existing pigment DIAGNOSIS Asymmetry Border irregularity Color Diameter Elevation