Integumentary System Nestor T. Hilvano, M.D., M.P.H

Learning Objectives You should be able to: 1. Describe the histological structures of the integument including the layers of the epidermis and dermis. 2. Discuss the functions of the skin and subcutaneous tissue. 3. Discuss the skin’s color and pigmentation. 4. Describe the histology of hair and hair follicle. 5. Explain how a hair grow and distinguish the types of hair. 6. Describe the anatomical structure of nails and how they are formed. 7. Describe the structure and function of glands in the skin. 8. Explain how the skin responds to injury and aging.

Skin Largest organ (15% of body weight) 2 main layers: a) ______________ b) ______________ Rest on stroma (supporting tissue) called ___________. Functions: -Protection or defense -Excretion of materials by glands -Synthesis of Vitamin D3 (cholecalciferol) synthesis -Sensory receptors – pain, temperature, touch, pressure and vibration -Thermoregulation -Storage of lipids

Layers of the Epidermis Thick skin- located on palms and soles; 5 layers 1. Stratum germinativum 2. Stratum spinosum 3. Stratum granulosum* 4. Stratum lucidum* 5. Stratum corneum Thin skin- located on general region of the body; 3 layers 1. Stratum germinativum 2. Stratum spinosum 3. Stratum corneum a. general region of the body b. palm and soles

Epidermis of Thick Skin: Layers 1.Stratum germinativum (basale)- deepest layer; basal cells, melanocytes, and merkel cells; epidermal ridges (fingerprints) 2.Stratum spinosum- spiny layer due to shrinkage; dendritic (Langerhans) cells 3.Stratum granulosum * - grainy layer, 3 to 5 layers flat keratinocytes; contain keratohyaline granules 4.Stratum lucidum * - clear (prickle cell) layer; keratinocytes with eleidin, a precursor to keratin 5.Stratum corneum- superficial layer; dead, scaly, keratinized cells; barrier; water resistant; shed every 2-4 weeks Psoriasis results from increase in the mitotic rate of the germinativum causing epidermal layer replaced within a wk. ___ What cells are capable of initiating an immune response? ___ What layer of epidermis contain non-nucleated, squamous cells? ___ What pigment cells are found at stratum basale?

Skin Colors Melanin = brown, yellow- brown, or black pigment. ___ = flat pigmented spots. ___ = clusters of pigmented cells, raised or flat. ___ = most serious type of skin cancer. ___= homozygous recessive trait disorder caused by the absence of the pigment melanin (in skin, hair, or eyes). ___= pigment loss due to antibodies attacking melanocytes. a. albinism b. freckles c. vitiligo d. malignant melanoma e. moles (nevi)

Skin Colors ___ = blueness from deficiency of oxygen in the circulating blood (cold weather) ___ = redness due to dilated cutaneous vessels (anger, sunburn, embarrassment) ___ = yellowing of skin and sclera due to excess of bilirubin in blood a. erythema b. jaundice c. palor d. cyanosis

Dermis Connective tissue layer a) papillary layer or dermal papillae - areola (LCT) tissue - meissner’s corpuscle - dermatitis b) reticular layer - Dense Irregular CT - accessory organs Why does inflammation of the skin is painful?

Hypodermis Also called subcutaneous tissue or superficial fascia Functions –energy reservoir –thermal insulation What types of tissues is hypodermis composed of? _______. What is liposuction? ____. Why does subcutaneous injections of drugs has faster rate of absorption? ____.

Hair and Hair Follicle Hair is a keratinous strand produced by epithelial cells of hair follicle Hair bulb is where hair originates Hair papilla provides nutrients Epithelial root sheath – extension of epidermis Connective tissue root sheath – derived from the dermis Arrector pili muscle contraction causes goose flesh Hair matrix is important for growth Human hair can support 3 kg. (6.6 lb)

Sweat Glands ____ glands is simple tubular gland –help cool the body ____ glands produce sweat containing fatty acids –found only near hair follicles –bromhidrosis is body odor produced by bacterial action on fatty acids a. apocrine sweat glands b. eccrine (merocrine) sweat glands

Sebaceous Glands Oily secretion called sebum Flask-shaped gland with duct that opens into hair follicle ___ What type of gland is sebaceous gland as to manner of secretion? a. merocrine (eccrine) b. apocrine c. holocrine d. endocrine

Homework (Self-Review) 1. Define the following: melanocytes, jaundice, cyanosis, arrector pili muscle, merocrine sweat gland, apocrine sweat gland, sebaceous gland, hair matrix, langerhans cell, dermis, subcutaneous tissue, dermatitis, albinism, vitiligo, freckles, moles, keratinocytes, merkel cells, and erythema. 2. Describe briefly the 5 layers of epidermis in thick skin. 3. Discuss why hypodermic injection has faster rate of drug absorption? 4. Classify type of skin in: a) palms, b) chest, c) face, d) trunk, e) buttocks, f) soles