Integumentary System Overview

Integumentary System

• The integumentary system consists of skin, hair, nails, sweat glands, and sebaceous (oil) glands.

Structure of Skin

• The skin has two distinct regions: the epidermis and the dermis.
• The epidermis is the superficial region and is avascular, consisting of epithelial tissue.
• The dermis is the layer beneath the epidermis, composed mostly of fibrous connective tissue and is vascular.
• The hypodermis is the subcutaneous layer deep to the skin, mostly adipose tissue that absorbs shock and insulates.

Epidermis

• The epidermis is mostly composed of keratinized stratified squamous epithelium.
• There are four types of cells in the epidermis: keratinocytes, melanocytes, Langerhans cells, and Merkel cells.
• Keratinocytes produce the protein keratin, which gives skin its protective properties and are the major cells of the epidermis.
• Melanocytes produce the pigment melanin, which protects against UV radiation and provides skin color.
• Langerhans cells are immune cells that help fight infection.
• Merkel cells are sensory cells that detect touch.

Layers of the Epidermis

• The epidermis is composed of five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
• The stratum basale is the deepest layer and contains rapidly dividing cells that continually produce new keratinocytes.
• The stratum spinosum is a layer of cells that are held together by desmosomes.
• The stratum granulosum is a layer of cells that begin to keratinize, accumulate keratin, and a water-resistant glycolipid.
• The stratum lucidum is only found in thick skin and is a thin, translucent layer of cells.
• The stratum corneum is the outermost layer of the epidermis and is composed of dead, keratinized cells that provide protection from the environment.

Hair Follicles

• Hair follicles extend from the epidermal surface to the dermis,
• The hair bulb is the expanded area at the deep end of the follicle.
• The hair follicle receptor (or root hair plexus) is a sensory nerve ending that wraps around the bulb and acts as a touch receptor.
• The wall of the follicle has three layers: peripheral connective tissue sheath (or fibrous sheath), glassy membrane, and epithelial root sheath.
• The hair matrix is an actively dividing area of the bulb that produces hair cells.
• The arrector pili is a smooth muscle that attaches to the follicle and causes the hair to stand on end, creating "goose bumps."
• The hair papilla is a protrusion of dermal tissue that contains blood vessels that supply nutrients to the hair.

Types and Growth of Hair

• Vellus hair is a pale, fine body hair found in children and adult females.
• Terminal hair is coarse, long hair found on the scalp and eyebrows.
• Hair growth is affected by nutrition and hormones.
• Hair follicles cycle between active and regressive phases and grow an average of 2.25 mm per week.

Skin Functions

• The skin provides protection against environmental factors.
• The skin functions as a chemical barrier by secreting antimicrobial proteins, lipids, and acids, and an acid mantle with a low pH.
• The skin acts as a physical barrier by blocking water and water-soluble substances, while allowing some chemicals to penetrate, such as lipid-soluble substances.
• The skin provides a biological barrier with dendritic cells and macrophages that activate immune responses.
• The skin regulates body temperature by controlling blood flow and sweat gland activity.
• The skin senses touch, pressure, temperature, and pain through cutaneous sensory receptors.
• The skin synthesizes vitamin D.
• The skin carries out metabolic functions, including converting cortisone into hydrocortisone, and producing collagenase.
• The skin acts as blood reservoir for blood storage.
• The skin excretes a limited amount of nitrogenous wastes, such as ammonia, urea, and uric acid.

Skin Cancer and Burns

• Skin cancer is a serious condition that can occur when cells in the skin begin to grow abnormally.
• Three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma.
• Burns are injuries that can occur when the skin is exposed to heat, chemicals, or radiation.
• Burns are classified by degree: first-degree burns, second-degree burns, and third-degree burns.

This quiz covers key concepts related to the integumentary system, including the structure and function of skin layers, types of cells in the epidermis, and associated glands. Test your knowledge on the vital roles these components play in protection and regulation.