Integumentary System

Integumentary System

A body system mainly responsible for protection; consists of the skin, hair, glands, and nails.

Integument

Covering.

Main structures of the integumentary system

Skin and accessory structures such as hair, glands, and nails.

Protection

The skin protects against abrasion and ultraviolet light.

Sensation

Sensory receptors in the integumentary system detect heat, cold, touch, pressure, and pain.

Vitamin D production

Exposure to ultraviolet light allows the skin to produce a molecule that can be transformed into vitamin D.

Function of Vitamin D

Helps with calcium absorption.

Temperature regulation

Blood flow beneath the skin and sweat gland activity help regulate body temperature.

Secretion

Release of oil through the skin.

Excretion

Small amounts of waste, excess water, and excess salt are lost through the skin and sweat glands.

Skin

Made up of two major tissue layers: epidermis and dermis.

Two major layers of the skin

Epidermis and dermis.

Subcutaneous tissue

Connective tissue beneath the skin; it is not considered part of the skin.

Epidermis

The most superficial layer of skin; avascular and rests on the dermis.

Avascular

Without blood vessels.

Epidermis tissue type

Keratinized stratified squamous epithelium.

Functions of the epidermis

Prevents water loss and resists abrasion.

Keratin

Protein that makes the skin firm.

Strata

Distinct layers that compose the epidermis.

Five epidermal strata

Stratum corneum, lucidum, granulosum, spinosum, and basale.

Stratum corneum

Most superficial epidermal layer; has 25 or more layers of dead squamous cells.

Function of keratin in stratum corneum

Gives the stratum corneum structural strength.

Dandruff

Excessive sloughing of stratum corneum cells on the scalp.

Callus

Increase in the layers of the stratum corneum caused by friction.

Corn

Thickened stratum corneum over a bony prominence.

Stratum lucidum

3–5 layers of transparent dead cells found in thick skin.

Location of stratum lucidum

Palms of the hands and soles of the feet.

Stratum granulosum

2–5 layers of flattened, diamond-shaped cells.

Stratum spinosum

8–10 layers of many-sided cells with a spiny appearance.

Stratum basale

Deepest or basement layer of the epidermis where mitosis occurs.

Where does mitosis occur in the epidermis?

Stratum basale.

Where are melanocytes located?

Stratum basale.

Dermis

Vascular layer composed of dense collagenous connective tissue.

Cells found in the dermis

Fibroblasts, adipocytes, and macrophages.

Structures extending into the dermis

Nerves, hair follicles, smooth muscles, glands, and lymphatic vessels.

Collagen fibers in the dermis

Help keep the skin intact and provide structural strength.

Elastic fibers in the dermis

Provide resistance to stretching.

Cleavage lines (tension lines)

Directions within the dermis that are more resistant to stretching.

Why are surgical incisions made parallel to cleavage lines?

They tend to gap less, produce less scar tissue, and heal faster.

Dermal papillae

Projections of the upper dermis toward the epidermis that contain many blood vessels.

Dermal papillae and fingerprints

Dermal papillae contribute to the ridges that produce fingerprints and footprints.

Stretch marks

Can occur when overstretching damages the dermis.

Factors determining skin color

Pigments in the skin, blood circulating through the skin, and thickness of the stratum corneum.

Effect of UV light on melanocytes

Stimulates melanocytes to increase melanin production.

Melanin

Group of pigments mainly responsible for skin, hair, and eye color.

Melanocytes

Cells that produce melanin.

Function of melanin

Provides protection against UV light.

Melanosomes

Vesicles into which melanin is packaged.

Carotene

Lipid-soluble pigment that can accumulate in the stratum corneum, dermis, and subcutaneous tissue.

Effect of excessive carotene consumption

Can cause the skin to become yellowish.

Beta carotene

Associated with vitamin A and good eyesight.

Albinism

Condition in which a mutation prevents melanin production.

Albinism and skin cancer

Albinism is associated with a high risk of skin cancer.

Pale skin during shock

Can result from decreased blood flow through the dermis.

Cyanosis

Bluish skin color caused by decreased blood oxygen content.

Hair

Protects the skin and helps reduce friction.

Areas where hair is absent

Palms, soles, lips, nipples, parts of the genitalia, and distal segments of fingers and toes.

Hair follicle

Invagination of the epidermis extending deep into the dermis where hair arises.

Hair shaft

Part of the hair that projects above the skin surface.

Hair root

Part of the hair below the skin surface.

Cortex

Hard portion of hair surrounding the softer center.

Medulla

Softer center of the hair.

Cuticle

Single layer of overlapping cells covering the cortex.

Hair bulb

Area where hair is produced and which rests on the hair papilla.

Hair papilla

Extension of the dermis that protrudes into the hair bulb and contains blood vessels.

Hair growth stage

Hair forms through mitosis of epithelial cells in the hair bulb followed by keratinization.

Hair resting stage

Hair growth stops and the hair is held within the hair follicle.

Arrector pili muscle

Smooth muscle attached to a hair follicle that helps with body temperature regulation.

Two major glands of the skin

Sebaceous glands and sweat glands.

Sebaceous glands

Simple branched acinar glands that produce sebum.

Sebum

Oily, white, lipid-rich substance produced by sebaceous glands.

Function of sebum

Lubricates hair and skin, prevents drying, and protects against some bacteria.

When are sebaceous glands more active?

During puberty.

Two types of sweat glands

Eccrine and apocrine sweat glands.

Eccrine sweat glands

Simple coiled tubular glands that release sweat through merocrine secretion.

Where are eccrine sweat glands most numerous?

Palms and soles.

Apocrine sweat glands

Produce thick secretions rich in organic substances and open into hair follicles.

Locations of apocrine sweat glands

Axillary and pubic areas.

When do apocrine glands become active?

During puberty due to the influence of sex hormones.

Cause of body odor

Apocrine secretion is initially odorless but bacterial action breaks it down and produces odor.

Nails

Thin plates consisting of dead stratum corneum cells containing very hard keratin.

Nail body

Visible part of the nail.

Lunula

Whitish portion visible through the nail body.

Cuticle (eponychium)

Stratum corneum extending onto the nail body.

Nail root

Nonvisible portion extending distally from the nail matrix.

Diagnostic importance of the integumentary system

It can help with diagnosis because the skin is easily observed.

Cyanosis as a diagnostic sign

May indicate impaired circulatory or respiratory function due to decreased blood oxygen.

Jaundice

Yellowish skin color that can occur with liver damage or other causes mentioned in the module.

Hepatitis

Inflammation/damage involving the liver that can be associated with jaundice.

Burn

Injury to tissue caused by heat, cold, friction, chemicals, electricity, or radiation.