Anatomy Ch. 4: Integumentary System

Thick Skin

covers the palms of the hands and soles of feet, all 5 epidermal layers are present (can be 6x thicker than thin skin)

eponychium

cuticle, formed by portion of stratum of corneum of the nail fold that extends over exposed nail near the root

Vellus hairs

fine "peach fuzz" hairs covering much of the body

myoepithelial cells

found in both types of sweat glands. located between gland cells and underlying basal lamina, these cells contract and squeeze the gland and discharge accumulated secretions.

hyponychium

free edge of the nail body extends over thickened stratum corneum

intermediate hairs

hairs that change in their distribution, such as those of upper and lower limbs

Terminal hairs

heavy,more deeply pigmented, sometimes curly. (hair on your head, eyebrows, eyelashes)

furnucle

if a duct/gland becomes blocked, an abscess called furnucle can form (boil)

melanin in light vs dark skinned people

in light skinned individuals, melanin transfer occurs in stratum basale and stratum spinosum, and the number of intact melanosomes decreases in the more superficial layers, making the skin lighter. in dark skin, melanosomes are larger and transfer continues into stratum granulosum, making the skin more pigmented.

mammary glands

in the breasts, complex interaction between sexual and pituitary hormones controls their development and secretion

Cutaneous Plexus

interconnected network of arteries and veins supplying the skin, present in subcutaneous layer along the border with the reticular layer.

Hair Production

involves a specialization of the keratinization process. When the superficial basal cells divide, th daughter cells are pushed toward the surface as part of the developing hair.

Sebaceous follicles

large sebaceous glands that communicate directly with the epidermis. never produce hair, and are found on face, back, chest, nipples, and male sex organs.

Callus

local thickening of the skin from excess friction, which causes increased keratohylin and keratin synthesis.

Superficial Papillary Layer of Dermis

loose connective tissue, contains capillaries supplying epidermis and axons of sensory neurons that monitor receptors in papillary layer and epidermis

Outer Cortex of hair

matrix cells closer to the edge of the developing hair form the relatively hard cortex. Cortex contains hard keratin that gives hair its stiffness.

pheremones

may be contained in apocrine gland secretions. chemicals that communicate information to other at subconscious level.

Ceruminous glands

modified sweat glands located in external auditory canal. different than merocrine glands in that they have a larger lumen and their gland cells contain pigment granules and lipid droplets not found in other sweat glands. secretions combine with nearby sebaceous glands to produce EARWAX (cerumen)

merocrine sweat glands (eccrine sweat glands)

more numerous than apocrine, much smaller though. palms and soles have the highest number of them, discharge directly onto the skin.

Stratum Corneum

most superficial epidermal layer, many layers of flattened, dead cells, that still contain lg. amts of keratin filaments, relatively dry, so unsuitable more microorganism growth, water resistant but not waterproof, because water from interstitial fluid exits through this layer to be evaporated (sweat),

Nail

nail body (nail itself) covers the nail bed, nail production occurs at the nail root, which is the deepest portion of the nail. Nail body is bounded by nail grooves (nail) and nail folds (skin).

Importance of subcutaneous layer (hypodermis, or superficial fascia)

not considered part of integument but still stabilizes the position of the skin in relation to underlying tissues, such as skeletal muscles/other organs, while permitting independent movement.

Roles of the dermis (papillary layer)

nourishes and supports the epidermis

Cyanosis

occurs during a sustained reduction in blood supply to dermis, skin appears bluish. (usually seen in lips or under nails), can be caused by extreme cold, respiratory disorders or even severe asthma.

Sebaceous Glands

oil glands, discharge oily secretions into hair follicles. lipids are released through holocrine secretion. lipids released enter open passageways (lumen), and contraction of arrector pili squeezes the sebacceous gland, forcing waxy secretions (sebum) to surface of the skin.

lunula

pale crescent nearest root, vessels may be obscured here, causing the discoloration

Langherans cells

play an important role in initiating an immune reponse against pathogens that have penetrated the superficial layers of the epidermis

dermal papillae

projections from the dermis toward the epidermis, extending between adjacent epidermal ridges.

Roles of Nails

protect and support tips of fingers and toes

Ratio of melanocytes to stem cells in the stratum basale

ranges from 1:4 to 1:20, depending on the region

Tension Lines of skin

reflect orientation of collagen bundle fibers in the dermis, affect how quickly and how well skin will heal after a cut. (important in surgery)

apocrine sweat glands

release secretions into hair follicles (armpits, around nipples, in the groin). secretory products are ACTUALLY produced through merocrine secretion. coiled glands that produce cloudy/potentially odorous secretion,start at puberty.

arrector pili

ribbon of smooth muscle, when stimulated, it pulls on the follicle and elevates the hair (goose bumps) can be response to cold, acting to increase thickness of "insulating coat"

Tactile discs

sensory nerve endings , monitor touch receptors (ex. Merkel cells)

Root hair plexus

sensory nerves that surround the base of each hair follicle so the movement of even a single hair can be felt at a conscious level.

simple vs. branched alveolar glands

simple-each gland has its own duct branched-several glands empty into a single duct

Subpapillary Plexus (papillary plexus)

small arteries branch into the dermis, and form a network when they reach the papillary layer. Eventually this network circles back and empties into the deeper cutaneous plexus

The dermis is ______________ to the deep fascia.

superficial

hair papilla

surrounded by the epithelium at the follicle base. It is a peg of connective tissue containing capillaries and nerves.

hair matrix

the epithelial layer involved in hair production

Shaft of the hair

the part we see on the surface, extends about halfway to the skin surface, to the exposed tip of the hair. size, shape and color can vary

glassy membrane

thickened basal lamina, wrapped in dense connective tissue sheath

sebum

waxy secretions that provide lubrication and inhibit bacteria growth. it protects the keratin of the hair shaft and conditions surrounding skin.

Basal cell -> keratinocyte

when a basal cell divides, a daughter cell is pushed into the stratum spinosum, where it begins to differentiate into a keratinocyte

club hair

while hair is growing, the root is firmly attached to the matrix of the follicle, at the end of growth cycle, follicle becomes a=inactive and hair becomes a club hair.

Thick Skin

Covers most of the body, only 4 layers deep because stratum lucidum is absent

2 layers of the Cutaneous Membrane

Epidermis and Dermis

Accessory Structures of the Integumentary System

Hair follicles, exocrine glands, and nails

Stratum spinosum

4th epidermal layer from surface (2nd deepest) several cells thick, keratinocytes bound together by maculae adherins attached to tonofibrils, some keratinocytes divide in this layer, Langerhans cells and melanocytes often present here

sweat

99% water, 1% of electrolytes (mainly NaCl), produced by merocrine glands

Roles of exocrine glands

-assist in thermoregulation -excrete wastes -lubricate epidermis

Roles of Hair follicles

-produce hairs that protect skull -produce hairs that provide delicate touch sensations on general body surface

Roles of the epidermis

-protect dermis from trauma, chemicals -skin permeability, prevents water loss -prevents entry of pathogens -synthesize vit D3 -sensory receptors to detect touch, pain, pressure, temp. -immune response to pathogens and skin cancers

roles of the dermis (reticular layer)

-restricts spread of pathogens -stores lipid reserves -attaches skin to deeper tissues -sensory receptors to detect pain, pressure, touch, vibration, temp. -blood vessels assist in thermoregulation

Stratum Lucidum

2nd epidermal layer from the surface, only in the thick skin (palms and soles), cells lack organelles and nuclei, flattened and densely packed

Stratum Granulosum

3rd epidermal layer from the surface (3rd deepest), keratinocytes produce keratin and keratohylin, keratin fibers develop as cells become thinner and flatter, cell membrane gradually thickens, organelles disintegrate and cells die

Merkel cells

A type of touch receptor. found contained in skin cells that lack hair. They are sensitive to touch, when compressed, they release chemicals that stimulate sensory nerve endings to provide info about objects touching skin.

How do stretch marks occur?

Because of the excessive distortion of the dermis that occurs, the elastic and collagen fibers break and the skin does not recoil to its original size.

Epidermal ridges

Pattern revealed in your fingerprint pattern, stratum basale forms these ridges into the dermis, increasing the contact area between the regions.

5 layers of the epidermis (deep to superficial)

Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

2 layers of the dermis

Superficial Papillary layer and Deeper Reticular layer

Internal Root Sheath

Surrounds the hair root and the deeper portion of the shaft, produced by cells at the periphery of the hair matrix. typically ends where the sebaceous gland duct attaches to the hair follicle

Cuticle of hair

a single layer of dead, keratinized cells at the outer surface of the hair form the cuticle that coats the hair.

How long does it take for a cell to move from stratum basale to stratum corneum?

about 15-30 days, and about 2 weeks in the cornuem before they are shed

2 groups of sweat glands

apocrine and merocrine

Lanugo hairs

appear after 3 months of embryonic development, very fine and unpigmented, usually shed before birth

folliculitis

bacteria in glands/follicles that produces local inflammation

tonofibrils

bundles of protein filaments contained in each keratinocyte,, extending from one side of the cell to the other. (begin and end at macula adherins, or desmosomes, which connect the keratinocyte to its neighbors) tonofibrils act as braces to strengthen and support the cell junctions

Skin color is determined by what two pigments?

carotene and melanin, the amount of these two are under genetic control

Keratohylin

cells in stratum granulosum begin to maufacture this, it assumulates in eletron dense granules, which form an intracellular matrix, surrounding keratin filaments.

Lipid rich substance of Stratum Granulosum

cells in this layer can release their contents by exocytosis to form sheets of a lipid rich substance. That substance coats the cells, and will form a water resistant layer to protect the epidermis. This, though, prevents nutrient diffusion, causing the more superficial layers to die.

Why might nails turn yellow?

chronic respiratory disorders, AIDS, or thyroid gland disorders

Deep Reticular layer of Dermis

collagen fiber bundles in interwoven arrangement that surrounds blood vessels, hair follicles, nerves, sweat glands, and sebaceous glands. some collagen fibers extended into papillary layer, connecting the two.

What does white hair result from?

combination of a lack of pigment and air bubbles within the medulla of the hair shaft

hair bulb

consists of epithelial cells cells that surround the hair papilla

Stratum Basale

deepest epidermal layer, attaches to basal lamina, contains: epidermal stem cells (basal cells), melanocytes, Merkel cells

Inner Medulla of hair

each hair has an inner medulla, which contains relatively soft/flexible soft keratin.

External Root Sheath

extends from skin surface to the hair matrix,

Hair root

extends from the hair bulb to the point where the internal organization of the hair is complete. It attaches the hair to the hair follicle.