Unit 3 The Integementary System

Integumentary System

Comprises the skin, hair, and nails, serving as the body's outermost protective barrier.

Body Membranes

Thin sheet-like structures that cover and protect, lining body cavities and inner surfaces, with functions including lining, protection, and lubrication.

Connective Tissue Membranes

Composed solely of various connective tissues, such as synovial membranes that line spaces between moving bones and joints.

Synovial Membrane

A smooth and slick membrane that secretes synovial fluid to reduce friction between bones and joints.

Epithelial Membranes

Composed of epithelial tissues and underlying layer of connective tissue.

Serous Membrane

An epithelial membrane that lines body cavities and covers organs, with parietal and visceral portions and serous fluid filling the cavity.

Mucous Membrane

An epithelial membrane that lines body surfaces open to the outside, secreting mucus for protection and lubrication.

Cutaneous Membrane

Refers to the skin, being the largest and most visible organ of the body.

Skin Function

Protection, temperature regulation, sense organ activity, important molecule protection, blood reservoir, and excretion.

Hypodermis/Subcutaneous Tissue

The fatty tissue layer beneath the skin.

Epidermis

The outermost layer of the skin, constantly regenerating and classified into thick skin (palms, fingers, soles) and thin skin (rest of the body).

Dermis

The thickest layer of the skin composed of connective tissue, fibers, and blood vessels, with papillary and reticular layers.

Stratum Corneum

The outermost layer of the epidermis consisting of dead, flat, hardened keratinocytes replaced by keratin.

Stratum Lucidium

Very thin clear band of flattened dead keratinocytes (NOT PRESENT IN THIN SKIN).

Stratum Granulosum

A small layer where the keratinocytes are actively changing by flattening out and harden as granules begin "armor plating" the cells.

Stratum Spinosum

Keratinocytes in this layer appear spiny as they begin to shrink.

Stratum Basale

The deepest epidermal layer attached to the dermis, consisting of rapidly dividing keratinocytes and melanocytes producing melanin.

Langerhans Cells

Cells present in the stratum spinosum of the epidermis that help activate the immune system.

Melanocytes

Cells in the stratum basale that produce melanin, the pigment responsible for skin color.

Merkel Cells

Function as touch receptors (with merkel discs in dermis).

Epidermis Physiology

The constant sloughing off and replacement of epidermal cells, with cell production in the stratum basale and complete epidermal replacement every 25-45 days.

Melanin

A pigment produced by melanocytes packaged in melanosomes in the skin's basal layer, providing protection against UV rays and determining skin color.

Papillary Layer

The thin, superficial layer of the dermis containing areolar connective tissue, capillaries, and sensory neurons.

Elastin

A type of fiber present in the dermis providing elasticity to the skin.

Collagen

A type of fiber in the dermis contributing to the skin's strength.

Dermal Papillae

Fingerlike projections of the papillary layer of dermis

Epidermal Ridges

Areas of the epidermis that dip down into the dermal papillae

Reticular Layer

Deepest and thickest skin layer containing dense irregular connective tissue, arteries, veins, and glands

Cleavage lines

Deep creases where collagen and elastic fibers are arranged in parallel bundles

Light Touch

Meissner's Corpuscles, Merkel Discs, and Root Hair Plexus.

Deep Pressure

Pacinian Corpuscles and Ruffini's Corpuscles.

Free nerve endings

Sensory receptors for pain and temperature.

Krause End Bulbs

Sensory receptors for temperature.

Sudoriferous (sweat) glands

Glands that originate in the dermis, excrete sweat, and are found throughout the skin except nipples and some genital areas

Eccrine Sweat Glands

Most common sweat glands that produce watery sweat released through pores

Apocrine Sweat Glands

Sweat glands found in axillary and genital regions, larger than eccrine glands, excreting sweat, fatty substances, and proteins into hair follicles

Sebaceous (oil) glands

Glands found all over the body except palms and soles, secreting sebum to lubricate and protect the skin

Sebum

Oily substance of lipids and cell fragments secreted by sebaceous glands. It softens and lubricates the hair and surrounding skin and is antibacterial.

Hair (Pili)

A modified portion of the epidermis where cells fill with hard keratin and grow out in pillars instead of the flat sheets of the stratum corneum.

Hair follicle

Modified fold of the epidermis into the dermis where hair grows from

Root Hair Plexus

A touch receptor wrapping the hair bulb, or the deep end of the follicle.

Papilla

Dermal tissue that protrudes into the hair supplying the hair with blood vessels.

Hair Matrix

Actively dividing area that produces the hair shaft.

Arrector pili muscle

Smooth muscle cells that raise the hair when cold or scared

Hair shaft

Consists of medulla, cortex, and cuticle layers of keratinized cells

Anagen Growth Phase

Lasting weeks to years depending on location.

Catagen Regressive Phase

When the hair matrix cells die.

Telogen Resting Phase

Lasts one to three months.

Nail Matrix

Area of epidermis producing new nail cells

Lunula

White crescent visible on the nail above the matrix

Hyponychium

Area under the free edge of the nail

Nail Bed

Deeper layers of epidermis underneath the nail body which contains blood vessels.

Nail Root

Area of nail embedded in the matrix.

Eponychium

Cuticle; area where the skin folds in on itself.