The Integumentary System

Functions Guard the body’s physical and biochemical integrity Maintain a constant body temperature Provide sensory information about the surrounding environment.

Structure of the Skin 1. Epidermis Superficial; composed of epithelial tissue 2. Dermis Deeper layer; composed of connective tissue 3. Subcutaneous layer (Hypodermis) = not part of skin; consists of areolar and adipose tissues

Epidermis Composed of stratified squamous and contains four types of principal cells

Epidermal Cells 1. Keratinocytes Contain keratin which waterproofs cells; protect skin and underlying tissue from heat, microbes, and chemicals 2. Melanocytes Pigment cells; responsible for skin color and absorbs UV light 3. Langerhans cells Participates in immune responses 4. Merkel cells Sensory structure that function in touch

5 Layers of Epidermis 1. Stratum basale 2. Stratum spinosum Deepest layer of epidermis; contains some stem cells capable of undergoing cell division; when destroyed, new skin cannot regenerate without a skin graft 2. Stratum spinosum provides strength and flexibility

5 Layers of Epidermis 3. Stratum Granulosum Transition between deeper, metabolically active strata and the dead cells of the more superficial strata; formation of water repellent sealant between cells 4. Stratum Lucidium Present in only the fingers, palms, and soles (thick skin) 5. Stratum Corneum Most superficial layer; consists of dead cells

Dermis Two Regions Papillary layer Superficial Reticular layer Deep

Papillary Layer of Dermis Areolar Connective Tissue Contains Touch receptors Free nerve endings heat, cold, pain, tickle, and itch

Reticular Layer of Dermis Deeper region of dermis Contains Hair follicles Sebaceous (oil) glands Sudoriferous (sweat) glands

Structure and Basis of Skin Color A. Three Pigments: melanin, carotene, and hemoglobin B. Albinism = inherited inability to produce melanin C. Vitiligo = complete or partial loss of melanocytes from patches of skin; results in irregular white spots

Accessory Structures of Skin (hair, glands, nails)

Anatomy of Hair (Pili) Shaft = above the surface Root = penetrates the dermis Cuticle = covers hair Hair follicle = hair grows from here

Skin Glands

Sebaceous (Oil) Glands Produce sebum which moistens hair, waterproofs, and softens the skin; inhibits bacterial growth Acne results when sebaceous glands become inflamed

Sudoriferous (Sweat) Glands Eccrine sweat glands = function to help regulate body temp. through evaporation and eliminate wastes (urea) Apocrine sweat glands limited in distribution; occur in axillae (armpit) and pubic regions

Ceruminous glands Produce wax (cerumen) Found in ear

Nails Hard, keratinized epidermal cells Functions: grasping and protection

Types of Skin Thin vs Thick Skin

Thin vs Thick Skin Thin Skin Thick Skin Covers all parts of body except palms, palmar surfaces of digits, and soles Thick Skin Covers palms, palmar surfaces of digits, and soles; lacks hair follicles, sebaceous glands, and has more sweat glands

Functions of Skin Thermoregulation = regulate body temp Protection Cutaneous sensations = touch, pressure, vibrations, tickle, heat, cold, and pain D. Synthesis of Vitamin D