The Integumentary System Overview

Study Notes

Comprises skin (cutaneous membrane) and accessory structures (hair, glands, nails, sensory receptors).
Largest system in the human body.

Two major layers:
- Epidermis: Outer layer, composed of epithelial tissue, avascular.
- Dermis: Inner layer, made of connective tissue.
Hypodermis (subcutaneous tissue):
- Stabilizes skin, consists of elastic and adipose tissues, contains few capillaries.
- Site for subcutaneous injections.

Contains four types of cells:
- Keratinocytes: Produce keratin to protect and prevent dehydration.
- Melanocytes: Produce melanin, influencing skin color.
- Langerhans cells: Involved in immune responses.
- Merkel cells: Responsible for touch sensation.
Composed of 4-5 layers:
- Stratum Corneum: Outermost layer of dead keratinocytes.
- Stratum Lucidum: Present only in thick skin (e.g., palms, soles).
- Stratum Granulosum: Keratinocytes undergoing apoptosis and granule formation.
- Stratum Spinosum: Provides strength and flexibility; contains Langerhans and melanocytes.
- Stratum Basal: Includes stem cells and melanocytes.

Cells in the stratum basal push toward the surface, accumulate keratin, and undergo apoptosis.
Excessive shedding of keratinized cells from the scalp is known as dandruff.

Composed of blood vessels, nerves, glands, and hair follicles.
Divided into:
- Papillary Layer: Superficial, rich in nerve endings.
- Reticular Layer: Thick, rich in collagen fibers, resists stretching.

Determined by melanin, hemoglobin, and carotene.
Melanocyte counts are similar in all individuals; variations in skin color arise from pigment amounts.
UV exposure increases melanin production.

Hair: Composed of dead, keratinized cells; provides protection and insulation.
Hair Structure:
- Shaft (above skin) and follicle (below skin), associated with arrector pili muscle.
Glands:
- Sebaceous Glands: Produce sebum; protect from drying and inhibit bacteria.
- Eccrine Sweat Glands: Most numerous, open at the epidermis.
- Apocrine Sweat Glands: Located in hairy skin, activated at puberty.
- Ceruminous Glands: Modified sweat glands in the ear canal.

Superficial: Merkel and Meissner receptors (respond to light touch).
Deep: Pacinian corpuscle and Ruffini receptors (respond to pressure and vibration).

Thin Skin: Covers most body areas, lacks stratum lucidum, contains hair and sebaceous glands.
Thick Skin: Found in palms and soles, has stratum lucidum, fewer hairs, more sweat glands.

Two types:
- Epidermal Healing: Affects only the epidermis.
- Deep Healing: Involves dermis and subcutaneous layers.

Wrinkles, dehydration, reduced sweat production, gray hair, and thinner skin occur with age.
Increased risk of pressure ulcers (bed sores).

Caused by excessive UV exposure; three major types:
- Basal Cell Carcinoma
- Squamous Cell Carcinoma
- Malignant Melanoma

First-Degree: Affects only the epidermis (e.g., sunburn).
Second-Degree: Destroys epidermis and part of dermis (blister).
Third-Degree: Full-thickness burn affecting all skin layers.
Rule of Nines: Used to estimate the total body surface area affected by burns.