Chapter 5: The Integumentary System

 What are the structures and functions of the integumentary system?

Size of the Integument  The integument is the largest system of the body: 16% of body weight 16% of body weight 1.5 to 2 m 2 in area 1.5 to 2 m 2 in area

Parts of the Integument  The integument is made up of 2 parts: 1. cutaneous membrane (skin) 2. accessory structures

Parts of the Integumentary System

Parts of the Cutaneous Membrane  Outer epidermis: superficial epithelium (epithelial tissues) superficial epithelium (epithelial tissues)  Inner dermis: connective tissues connective tissues

Accessory Structures  Originate in the dermis  Extend through the epidermis to skin surface: hair hair nails nails multicellular exocrine glands multicellular exocrine glands

Connections  Circulatory system: blood vessels in the dermis blood vessels in the dermis  Nervous system: sensory receptors for pain, touch, and temperature sensory receptors for pain, touch, and temperature

The Subcutaneous Layer  Subcutaneous layer (superficial fascia or hypodermis): loose connective tissue loose connective tissue below the dermis below the dermis location of hypodermic injections location of hypodermic injections

Functions of Skin  Protects underlying tissues and organs  Excretes salts, water, and organic wastes (glands)  Maintains body temperature (insulation and evaporation)

Functions of Skin  Synthesizes vitamin D 3  Stores lipids  Detects touch, pressure, pain, and temperature

What are the main structures and functions of the epidermis?

Cells of the Epidermis  Keratinocytes: contain large amounts of keratin contain large amounts of keratin the most abundant cells in the epidermis the most abundant cells in the epidermis

Epidermis  Avascular stratified squamous epithelium  Nutrients and oxygen diffuse from capillaries in the dermis

Thin Skin  Covers most of the body  Has 4 layers of keratinocytes

Layer of skin  Stratum germinativum Epidermal ridges Epidermal ridges

Page 156  Stratum spinosum Spiny layers Spiny layers

P 156  Stratum granulosum Grainy layer Grainy layer

5 layers of skin only  Stratum lucidum Only in palms and soles Only in palms and soles

p156  Stratum corneum Dead Dead 15 – 30 cell layers15 – 30 cell layers Water resistant – not waterproofWater resistant – not waterproof

Thick Skin  Covers the palms of the hands and soles of the feet  Has 5 layers of keratinocytes

Skin Life Cycle  It takes 15–30 days for a cell to move from stratum germinosum to stratum corneum

What causes different skin colors?

Skin Color  Skin color depends on: the pigments carotene and melanin the pigments carotene and melanin blood circulation (red cells) blood circulation (red cells)

Carotene  Orange-yellow pigment  Found in orange vegetables  Accumulates in epidermal cells and fatty tissues of the dermis  Can be converted to vitamin A

Melanin  Yellow-brown or black pigment  Produced by melanocytes in stratum germinativum  Stored in transport vesicles (melanosomes)  Transferred to keratinocytes

Function of Melanocytes  Melanin protects skin from sun damage  Ultraviolet (UV) radiation: causes DNA mutations and burns which lead to cancer and wrinkles causes DNA mutations and burns which lead to cancer and wrinkles

Melanocytes  Skin color depends on melanin production, not number of melanocytes

Capillaries and Skin Color  Oxygenated red blood contributes to skin color: blood vessels dilate from heat, skin reddens blood vessels dilate from heat, skin reddens blood flow decreases, skin pales blood flow decreases, skin pales

Cyanosis  Bluish skin tint  Caused by severe reduction in blood flow or oxygenation

Illness and Skin Color  Jaundice: buildup of bile produced by liver buildup of bile produced by liver yellow color yellow color  Addison’s disease: and other diseases of pituitary gland and other diseases of pituitary gland skin darkening skin darkening

What are the structures and functions of the dermis?

The Dermis  Is located between epidermis and subcutaneous layer  Anchors epidermal accessory structures (hair follicles, sweat glands)

Characteristics of Dermis  Strong, due to collagen fibers  Elastic, due to elastic fibers  Flexible (skin turgor)

Skin Damage  Sagging and wrinkles (reduced skin elasticity) are caused by: dehydration dehydration age age hormonal changes hormonal changes UV exposure UV exposure

Lines of Cleavage  Collagen and elastic fibers in the dermis: are arranged in parallel bundles are arranged in parallel bundles resist force in a specific direction resist force in a specific direction

Clinical Importance  Lines of cleavage establish important patterns: a parallel cut remains shut, heals well a parallel cut remains shut, heals well a cut across (right angle) pulls open and scars a cut across (right angle) pulls open and scars

Lines of Cleavage

Dermal Circulation

What are the structures and functions of the subcutaneous layer? What are the structures and functions of the subcutaneous layer?

The Hypodermis  The subcutaneous layer or hypodermis: lies below the integument lies below the integument stabilizes the skin stabilizes the skin allows separate movement allows separate movement

What are the skin glands and secretions?

Exocrine Glands  Sebaceous glands (oil glands): holocrine glands holocrine glands secrete sebum secrete sebum  Sweat glands: merocrine glands merocrine glands watery secretions watery secretions

Types of Sebaceous Glands  Simple branched alveolar glands: associated with hair follicles associated with hair follicles  Sebaceous follicles: discharge directly onto skin surface discharge directly onto skin surface

Sebaceous Glands

Sebum  Contains lipids and other ingredients  Lubricates and protects the epidermis  Inhibits bacteria

What are the functions of sweat glands?

Types of Sweat Glands  Apocrine: found in armpits, around nipples, and groin found in armpits, around nipples, and groin  Merocrine: widely distributed on body surface widely distributed on body surface especially on palms and soles especially on palms and soles

Apocrine Sweat Glands  Merocrine secretions, not apocrine  Associated with hair follicles  Produce sticky, cloudy secretions  Break down and cause odors

Merocrine Sweat Glands  Also called eccrine glands: coiled, tubular glands coiled, tubular glands discharge directly onto skin surface discharge directly onto skin surface sensible perspiration sensible perspiration water, salts, and organic compounds water, salts, and organic compounds

Functions of Merocrine Sweat  Cools skin  Excretes water and electrolytes  Flushes microorganisms and harmful chemicals from skin