Ch. 6 Integumentary Text book pdf

Page 1: Vocabulary and Chapter Objectives

Vocabulary Understanding

• alb-: refers to a lack of pigment (e.g., o/binism—condition characterized by a lack of pigment)

• cut-: related to skin (e.g., subcutaneous—beneath the skin)

• derm-: pertaining to skin (e.g., dermis—inner layer of the skin)

• epi-: upon, in addition (e.g., epidermis—outer layer of skin)

• follic-: small bag (e.g., hair follicle—a tube-like depression in which a hair develops)

• holi-: entire, whole (e.g., holocrine gland—gland that discharges the entire cell containing the secretion)

• kerat-: horn (e.g., keratin—protein produced as epidermal cells die and harden)

• melan-: black (e.g., melanin—dark pigment produced by certain cells)

• pore: opening by which a sweat gland communicates to the skin's surface

• seb-: grease (e.g., sebaceous gland—gland that secretes an oily substance)

Chapter Objectives

After studying this chapter, you should be able to:

1. Describe the structure of the layers of the skin.

2. List the general functions of each layer of the skin.

3. Describe the accessory organs associated with the skin.

4. Explain the functions of each accessory structure of the skin.

5. Explain how the skin helps regulate body temperature.

6. Summarize the factors that determine skin color.

7. Describe the events that are part of wound healing.

8. Describe life-span changes in the integumentary system.

Page 2: Hair and Skin Functions

Hair Facts

• Hair as extensions of specialized cells in the outer skin layer.

• Humans have as many hair follicles as chimpanzees but appear relatively hairless.

• Lanugo: Downy layer coating the fetus formed during the fifth month of prenatal development.

• Hypertrichosis: Rare inherited condition resulting in excessive hair growth due to persistence of lanugo.

• Hair provides warmth to mammals; absent in aquatic mammals like whales and hippos.

Human Hair Function Theories

1. Less hair might help humans conquer grasslands due to resistance to overheating during running.

2. Parasite-reduction Hypothesis: Less fur reduces the risk of parasites.

Skin Structure and Functions

• The skin is composed of several types of tissues and is a protective covering vital in maintaining homeostasis.

• General functions include:

  • Protects against harmful substances and microorganisms.

  • Retards water loss and helps regulate body temperature.

  • Houses sensory receptors and synthesizes chemicals (e.g., vitamin D).

  • Contains immune cells and excretes waste.

Page 3: Skin Layers

Anatomy of the Skin

• The skin has two distinct layers:

  • Epidermis: Outermost layer made of stratified squamous epithelium, lacks blood vessels.

  • Dermis: Thicker than epidermis, composed of connective tissue containing collagen and elastic fibers, muscle, nervous tissue, and blood vessels.

• The layers are separated by a basement membrane connected via short fibrils.

Subcutaneous Layer

• Beneath the dermis is the subcutaneous layer (hypodermis), composed of loose connective tissue and adipose tissue.

• Functions include insulation and binding the skin to underlying organs, containing major blood vessels.

Page 4: Skin Components

Structure of Skin

• Key components include:

  • Sweat glands, Sebaceous glands, Hair follicles, and Nerve cells.

Skin's Tissues and Functions

• Skin's epidermis is comprised of stratified squamous epithelium while the dermis consists of connective tissue, muscle fibers, and nerve tissues.

• Unique sensory receptors (e.g., Meissner's corpuscles for light touch, Pacinian corpuscles for pressure).

Page 5: Epidermis Layers

Layers of the Epidermis

• The epidermis has several layers, primarily:

  1. Stratum corneum: Outermost, dead, keratinized cells.

  2. Stratum lucidum: Found in thick skin (palms/soles).

  3. Stratum granulosum: Contains granular cells.

  4. Stratum spinosum: Several layers of cells with developing keratin fibers.

  5. Stratum basale: Deepest layer where cell division occurs; contains melanocytes.

Skin Cell Lifespan

• Epidermal cells continuously divide; balance maintained with cell loss from the surface.

• Calluses form in areas of high friction due to increased cell production.

Page 6: Melanin Production

Melanocytes

• Melanocytes produce melanin, which protects skin from UV radiation and contributes to skin color.

• Sunburn is an inflammatory response to excessive UV exposure, leading to skin damage.

• Skin tanning is a response to increased melanin production due to UV exposure.

Page 7: Skin Cancer Risks

Skin Cancer Types

• Skin cancer arises from:

  • Cutaneous carcinomas (from epithelial cells).

  • Cutaneous melanomas (from melanocytes).

• Factors contributing include UV exposure, genetics, and skin types.

Page 8: Contact Dermatitis

Dermatitis Types

• Allergic contact dermatitis: Reactive response to allergens.

• Irritant contact dermatitis: Caused by irritants without immune response.

• Common in professions handling irritating substances.

Page 9: Hair Growth and Loss

Hair Follicles

• Each hair grows from epidermal cells at the follicle base; hair color is genetically determined.

• Alopecia conditions (e.g., androgenic alopecia) cause baldness or spots.

Page 10: Skin Appendages

Skin Glands and Functions

• Sebaceous glands secrete sebum for hair and skin maintenance.

• Sweat glands regulate body temperature and waste secretion.

Page 11: Nail Structure

Nail Anatomy

• Nails serve as protective covers on fingers and toes, consist of keratinized cells.

Page 12: Temperature Regulation

Body Temperature Control

• The skin plays a vital role in regulating body temperature through blood vessel dilation and sweating.

Page 13: Temperature Regulation Mechanism

Mechanisms of Heat Loss

1. Radiation: Heat radiates from warm surfaces to cooler surroundings.

2. Conduction: Heat transfers to cooler objects in contact with skin.

3. Convection: Air circulation that helps cool the body.

4. Evaporation: Sweat evaporation cools the body.

Page 14: Hypothermia and Hyperthermia

Temperature Regulation Problems

• Hyperthermia: Body's inability to cool down; symptoms include heat exhaustion.

• Hypothermia: Dangerously low body temperature from prolonged exposure to cold.

Page 15: Wound Healing

Healing Processes

• Inflammation: Normal response to injury; brings nutrients and oxygen to healing tissues.

• Different degrees of burns heal differently:

  • Superficial (first degree) heals quickly with minimal or no scarring.

  • Deep partial (second degree) involves blistering and longer healing.

  • Full thickness (third degree) may require skin grafting and extensive care.

Page 16: Skin Color Variability

Factors Influencing Skin Color

1. Genetic: Number of melanocytes is the same across races, variation due to melanin production.

2. Environmental: Sunlight and UV light darken existing melanin.

3. Physiological: Blood oxygen levels affect skin hue (red/pink when well-oxygenated, bluish when low).

Page 17: Changes with Aging

Age-Related Changes

• Aging affects skin appearance, elasticity, and temperature regulation.

• Thinning epidermis, sagging skin, slower healing processes, and other skin conditions emerge.

Page 18: Summary of Key Points

Key Summary Points

1. Skin and its structures make the integumentary system.

2. Skin functions include protection, regulation, sensory reception, and chemical synthesis.

3. Injured skin undergoes inflammation and healing processes.

4. Age-related changes affect skin structure, function, and appearance.