INTEGUMENTARY SYSTEM

Skin, hair, nails, and glands

What does it mean?

• Integere (Latin)- “to cover”• Dermato and cutis (Greek and Latin)- “skin”• Epi- (Greek)- “upon” or “above”

Why do we need it? overview

• Largest organ• Retains moisture• Sensory receptors for:– pain,– Heat– Touch

• Excretes salts• Excretes small amounts

of waste• Stores blood• Regulates body temp.

• 2 main parts– Epidermis and dermis

• Under the dermis is the hypodermis (supericial fascia- subcutaneous tissue)– It acts a foundation not truly part of the skin

Epidermis

• Surface skin– 1st line of defense against infection– Contains no blood vessels– Layers and layers of epithelial cells

• Melanocytes– ¼ of stratum basale is made of these– Synthesize a pale yellow to black pigment called

melanin– Cytocrine secretion- melanin is secreted into

keratinocytes• Melanin- skin color and protection against uv rays• Keratinocytes– majority of stratum basale– Primary epithelial cell of skin

More about the epidermis• Carotene- in stratum

corneum and fatty layers beneath the skin– Produces yellowish hue

common with Asian ancestry• Hemoglobin- cause for

pinkish color of Caucasian skin– Less melanin, more

hemoglobin• Albinos- no melanin in skin

at all

• Ridges and grooves- increase friction to grasp other objects– Ex. Loops and whorls

(fingerprints, palm prints, footprints)

The Dermis• Also known as the

corium • Thicker and more

fibrous than the dermis• 2 layers• Fibrolasts- connective

tissue develops

• Macrophages- engulf wastes and foreign microorganisms

• Adipose tissue• Thinnest over eyelids

and male sex organs• Thicker on back than

stomach• Thickest on palms of

hands and soles of feet

Papillary Layer

• Top (outer) layer• Soft• Elastic, reticular fibers that enter the epidermis – Brings blood and nerve endings closer

• Papillae are finger-like projections- loops of capillaries to increase the surface area of dermis and anchor epidermis

• Meissner’s corpuscles- nerve endings sensitive to soft touch.– In some papillae

Reticular Layer

• Rete- net (Latin)• Dense, irregular connective tissue– Interlacing bundles of collagenous and elastic

fibers• Strong resistant layer• Gives skin strength, extensibility, ad elasticity

• Oil glands (seaceous glands), sweat glands, fat cells, and larger blood vessels are in this layer

Hair• Follicles embedded in the epidermis and extend to

the dermis angle hair growth (curly or straight).• Follicle bases are expanded (called bulbs) reach

nerve endings• Epithelial cells in the bulb divide to create the hair

shaft • Hair pigment: melanin– Gives hair its color– Gray and white hair grow when melanin levels decrease

and air pockets form• sebaceous gland- sebum is produced (cholesterol,

fats, and other substances)– Keeps hair soft, pliable, and waterproof

• Hair has 3 layers– Medulla

• Central core• Cells contain eleidin separated by air spaces• Fine hair- minimal/ nonexistent

– Cortex• Major part of hair shaft

– Several layers– Flattened cells

• Elongated pigment-bearing cells in dark hair• Air pockets in white hair

– Cuticle• Single layer, overlapping cells with free end pointing up• Strengthens and compacts the inner layers• Split ends

– Abrasion wears away the end of the shaft, exposes the medulla and cortex to create the horrid split end

Sweat? Gross…or is it?• 2 types of sweat glands (sudoriferous)

– Coiled tubules in the dermis– Eccrine glands-all over body

• Watery (99%), salty secretion known as sweat

• Passes through the epidermis to skin’s surface and opens to a sweat pore

• Controlled by the sympathetic nervous system

– Apocrine sweat glands• Under the armpits and groin area,

associated with hair follicles• Same components as eccrine and is odorless

– Bacteria breaks down apocrine sweat’s fatty acids and proteins» Creates the odor accompanying post

exercise

Connection to the Nervous System• 4 receptors are involved in the sensation of touch• 2 primary temperature receptors• Dermis has neuromuscular spindles

(proprioceptors)– Transmit information to the spinal cord and brain about

the lengths and tensions of muscles• Provides awareness about the body’s position

– Spindles help in muscle coordination and muscle action efficiency

– Jess check with Hans but I think he covers this in his presentation!!!!!!

Touch • Free nerve endings- dendrites are primarily pain

receptors– Sometimes touch, temperature, and muscles– Fibers swell at the end in response– Disc-shaped (merkel discs) endings- light-touch receptors

in deep layers of epidermis• Meissner’s corpuscles- light-touch

mechanoreceptors in dermal papillae– Egg-shaped capsules of connective tissue around a

spiraled end of a dendrite– Great amounts in lips and fingertips– Sense quick touch, not sustained

• Pacinian corpuscles- deep-pressure mechanoreceptor– Dendrites surrounded by layers of connective tissue– Respond to deep/firm pressure or vibration– Visible to the naked eye- 2 millimeters long

• Hair nerve endings– Respond to change in hair position– Bare dendrites

TEMPERATURE• End-bulbs of Krause (Krause’s corpuscles)– Activate below 68 degrees F– Bulbous capsule surrounds the dendrite– Commonly found throughout the body in the dermis and

lips, tongue, and conjunctiva of the eyes• Brushes of Ruffini (Ruffini cylinders/Ruffini’s

Corpuscles)– Respond between 77 degrees and 113 degrees F– Found in dermis and subcutaneous tissue– Dendrite endings in flattened capsules– There are less then end-bulbs and are deeper in the tissue

• Human body is less sensitive to heat than to cold