Integumentary System Quiz

Integumentary System

• The integumentary system includes the skin and its accessory structures (hair, nails, glands, blood vessels, muscles, and nerves)
• Dermatology is the medical specialty for diagnosing and treating integumentary system disorders
• The skin, or cutaneous membrane, is the largest organ in the body by surface area and weight, approximately 2 square meters (22 square feet) and weighing 4.5-5 kg (10-11 lb), about 16% of body weight
• Skin thickness ranges from 0.5-4 mm, thinnest on eyelids and thickest on heels, with an average thickness of 1-2 mm
• A newborn's skin surface area is three times greater by volume than an adult's

Skin Structure

• The skin consists of two major layers: epidermis (outer, thinner layer of epithelial tissue) and dermis (inner, thicker layer)
• The subcutaneous layer (hypodermis) connects the skin to underlying tissues and organs

Epidermis

• The epidermis is composed of keratinized stratified squamous epithelium
• Four major cell types in the epidermis are keratinocytes (90%), melanocytes (produce melanin for UV protection), Langerhans cells (involved in immune responses), and Merkel cells (function in touch sensation)
• The epidermis has layers: stratum basale (deepest layer), stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin), and stratum corneum (outermost layer of flat, dead keratinocytes)
• Keratinization is the accumulation of keratin as cells move towards the surface, and continuously shed and replaced
• Dandruff is an excess of keratinized cells shed from the scalp
• Thick skin has five layers of epidermis, while thin skin has four

Dermis

• The dermis is composed of connective tissue containing collagen and elastic fibers
• The dermis has two regions: the papillary region (upper region) and the reticular region (lower region)
• The dermis contains nerve endings such as Meissner corpuscles (light touch), Pacinian corpuscles (deep pressure), and hair root plexuses (light touch)

Skin Color

• Skin color variations arise from differences in melanin, carotene, and hemoglobin
• Melanin, produced by melanocytes, is a yellow-red or brown-black pigment that protects against UV radiation
• Carotene is a yellow-orange pigment found in stratum corneum, dermis, and subcutaneous layer
• Hemoglobin, found in erythrocytes of dermal capillaries, contributes red color

Sun Protection

• Sun protection factor (SPF) measures the effectiveness of sunscreen
• SPF 15 allows for 15 times longer exposure to the sun without the same minimal degree of redness

Abnormalities in Skin Pigmentation

• Nevus (mole): benign localized overgrowth of melanocytes
• Albinism: inability to produce melanin, genetic condition
• Vitiligo: loss of melanocytes in patches due to autoimmune response
• Freckles: accumulation of melanocytes in patches, genetic condition

Accessory Structures of the Skin

• Hair: composed of dead, keratinized epidermal cells with functions in protection, heat loss reduction, and light touch sensation
• Skin glands: sebaceous (oil) glands that secrete sebum (protective oily substance), sudoriferous (sweat) glands that regulate body temperature, and ceruminous glands (in ear canal) that secrete earwax
• Nails: hard, keratinized plates that protect the dorsal tips of the fingers and toes

Wound Healing

• Epidermal wound healing involves basal cells migrating across the wound, stimulating epidermal growth factor for cell division
• Deep wound healing includes the inflammatory phase, migratory phase, proliferative phase, and maturation phase, with formation of blood clots, scabs, and scar tissue

Quick review

• Largest organ of the body: skin
• Thinnest layer of skin: eyelids
• Thickest layer of skin: heels
• Three pigments affecting skin color: melanin, carotene, hemoglobin
• A condition marked by partial or complete loss of melanocytes; Vitiligo
• Part of the hypodermis that detects external pressure: Pacinian corpuscles
• Muscle and nerve endings in hair follicles: arrector pili muscle and hair root plexus