A&P1 CH5 Integumentary System

Integumentary System

Skin - 1.5 to 4 millimeters

Upper epidermis, Lower dermis, below skin (hypodermis)

Upper Epidermis

Epithelial Tissue

Lower Dermis

Leathery connective tissue

Below skin, Hypodermis, subcutaneous tissue

Superficial fascia (Areolar & Adipose loose fibrous connective tissue)

Anchors the skin

Epidermis

Keratinized stratified squamous epithelium

4-5 layers (depends if it’s thick or thin skin)

Keratinocytes: most cells, produce keratin, from deepest layer stratum basal

Keratinocytes

Constantly divide & move to upper layers.

At surface dead (protective of under layers) and filled with keratin for strength and water resistance.

Epidermis Regeneration Cycle

New one every 25-45 days.

How does a callus form?

Keratin acceleration in areas subjected to friction.

Cells in the Epidermis

Melanocytes, granules, dendritic/langerhans cells, tactile/merkel cells

Melanocytes

In deepest layer, produce melanin

Granules

Melanosomes that are transferred to keratinocytes for UV protection

Dendritic / Langerhans cells

From bone marrow, ingest foreign material and activate immune system.

Take surveillance , then presents stuff to the immune system, “inspectors,” helps the immune system respond.

Tactile / Merkel Cells

Spiky, associated with sensory nerve for touch = ______ disc in bottom layer

Thick skin

Areas of abrasion = soles, fingers, palms

5 layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

Stratum Basale

Deepest Layer, 1 layer thick

Contains stem cells.

New cells move to upper layer above.

Melanocytes and Merkel (tactile) cells are present.

Stem cells

Basal cells that divide to form keratinocytes.

Stratum Spinosum

8-10 layers.

Keratinocytes have spines = prickle cells (see only from dead tissue)

Melanin granules and dendritic cells are present.

Many Desmosome connections.

Keratin production and release of water resistant glycolipid outside of the cells begins.

Stratum Granulosum

3-5 layers.

Keratinization continues in keratinocytes (completes)

Cells start to flatten, lose organelles, nuclei, disintegrate.

Accumulate Keratohaline and put in lamellar granules.

Keratinocytes die in upper layers.

Stratum Lucidum

ONLY THICK SKIN HAS THIS!

Thin, translucent band that is 2-3 rows thick of clear, flat, dead keratinocytes and gummy substance (eleiden) from keratohyaline that combines with keratin.

Stratum Corneum

Anucleated dead cells (cornified or horny cells)

15-30 layers.

keratin and thick plasma membranes offer protection against abrasion and penetration.

Glycolipid between cells makes the skin nearly waterproof.

Shed cells seen as dandruff / dander / skin flakes (50,000 cells/minute)

What is dandruff, dander, and skin flakes composed of?

Dead keratinocytes

Thin skin

Has 4 layers, no stratum lucidum

Dermis

Strong, flexible connective tissue.

Fibroblasts and macrophages mostly, mast and white blood cells occasionally.

Forms hides.

Semi fluid matrix.

See supply of nerve fibers, blood vessels, lymphatic vessels.

2 layers: papillary and reticular

Papillary layer

Thin, Areolar connective tissue with fibroblasts, defense (phagocytes) and fat cells.

“Upper layer of dermis”

Peg-like projections.

Small blood vessels and lymphatic capillaries, and nerve fibers.

Sweat leaves the crests of friction ridges to form fingerprint.

Peg-like projections on papillary layer

Dermal papillae with capillaries and meissner’s or tactile corpuscles for touch which indent and strongly connect to the overlying epidermis.

Papillary layer in thicker skin

Dermal papillae are atop dermal ridges which cause overlying epidermis to form epidermal ridges and together form friction ridges for gripping and sense detection (fingerprints)

Reticular Layer

Deeper layer, below papillary layer, 80% of dermis.

Dense irregular fibrous connective tissue.

Blood vessels at bottom form cutaneous plexus, lots of collagen and elastin & some adipose cells.

Ample blood & nerve supply.

Cleavage lines in Reticular Layer

Less dense regions of collagen.

Surgeons cut parallel to so that the skin gapes less and heals better.

(Shows the arrangement of collagen lines so you heal faster)

Collagen fibers in Reticular layer

For strength, resiliency, and hydration

Elastic Fiber in Reticular layer

For stretch-recoil

Flexure lines in Reticular layer

Dermal folds at/near the joints where dermis is tightly secured and folds creating deep skin creases in palm, fingers, foot, toes, wrist.

Dermis disorders: Extreme Stretching

Stretch marks (tears in the dermis), striae

Dermis disorders: acute trauma

Can cause blisters in which dermis separates from epidermis and forms fluid-filled packets.

Melanin

Made in skin. Located in stratum basale in the dermis.

Range from reddish yellow to brownish black.

Made by ______cytes that pass it to deeper layer keratinocytes in melanosomes which eventually get broken down by lysosomes.

How does darker skin differ from lighter skin?

We all have the same number of melanocytes but the amount of melanosomes with melanin and type of melanin produced is different.

Dark-skinned retain it longer.

Freckles and moles

Localized accumulation of melanin

Sun exposure effect on melanin production

Causes more melanin to be produced to protect cells by absorbing UV that can damage DNA and preventing folic acid breakdown.

What does melanin interfere with?

Vitamin D synthesis

What happens when you get too much UV?

You burn and peel (your body has “too much,” and your body wants to get rid of it)

What does excessive sun exposure do to the body?

Damages the skin by causing elastic fiber clumps, impair immune system, and can cause cancer.

Carotene

Yellow to orange pigment, accumulates in hypodermis and stratum corneum, due to foods.

hemoglobin

Found in red blood cells in dermis, seen mostly in caucasians since epidermis is clear and melanin does not mask as in darker-skinned people.

Blue

Cyanosis, poor oxygen

Redness

Hypertension, blushing, fever, inflammation, allergy

Pallor

Fear, anger, emotional stress, low blood pressure, anemia (“pale”)

Jaundice/yellow cast

Liver disorder

Bronzing

Addison’s disease with abnormal amounts of steroid hormones or brain tumors

Black and blue / bruises

Clotted blood outside blood vessels

Hair

Pili, produced by hair follicle, mostly dead Keratinized cells, keratin is tougher and doesn’t flake so termed “hard keratin” (vs skin = “soft keratin”)

Shaft

Portion in which keratinization is complete, not anchored to follicle, shape influences hair structure.

Root

Keratinization ongoing, anchored to the follicle, deep in skin, ends at hair bulb and contains matrix for new hair formation.

Hair: Medulla

Central core - large cells & air spaces

Hair: Cortex

Outside of the medulla - several layers of flat Keratinized cells

Hair: Cuticle

Outermost - single layer of overlapping Keratinized cells, avoids matting with other hairs, can wear away and form split ends.

How does hair color work?

Melanocytes at base of hair follicle and transferred, various proportions of melanin combine for color.

Grey/white hair

Melanin production decreased and air bubbles appear

How is bending the hair sensed?

Hair follicle extend from surface into dermis and possible hypodermis, at bottom see hair bulb surrounded by hair follicle receptor/root hair plexus.

Hair Papilla

“Nipple-shaped”

At the bulb containing capillaries (blood supply)

Wall of hair follicle: Outer Peripheral

Connective tissue sheath from the dermis

Wall of hair follicle: thick basal lamina

Glassy membrane covers root and connects to dermis.

Wall of hair follicle: Inner epithelial root

Sheath from epidermis with external root sheath that encloses root and internal root sheath that surrounds root and extends to shaft.

Basal cells of hair matrix

Above hair papilla produce keratinocytes and as a division continues hair is pushed up and the cells become Keratinized and die.

Arrector pili muscles

Small muscles attached to the hair follicles.

If cold, these muscles pull the hair follicle upright = see goose pimples to retain heat and produce oil.

Vellus

Pale and fine (body hair of children and females)

Terminal

Coarse and darker

Found: scalp, eyebrows, in axillary & pubic regions, also on face and chest of males

How fast does hair grow?

About 2.5 mm/week

Follicle growth cycles: Active Growth Anagen Phase

2-7 years

Follicle growth cycles: Regressive Growth Catagen Phase

2-3 weeks

Hair matrix cells die and follicle base and hair bulb shrivel

Follicle growth cycles: Telogen Phase

2-4 months “resting phase”

Hair lifespan

On scalp: 6-10 years

Lose: about 90 scalp hairs a day

In eyebrow: 3-4 months

Hirsutism

Excessive hairiness in females due to hormone imbalances

Alopecia

Baldness, all follicles have a limited number of cycles

Alopecia areata

Immune system attacks follicles

Nails

Scale-like modification of epidermis.

Hard keratin.

Has free edge, plate/body, root

Eponychium

Nail folds - skin folds and some form cuticle

Hyponychium

Thick skin region beneath free edge that secures nail

Sweat glands: Eccrine/Merocrine

Most numerous.

Concentrated on palms, soles, forehead.

Simple, coiled, tubular gland (secretory part in dermis and duct extends to open in a funnel-shaped pore at the skin surface)

Sweat

99% water with salts, vitamin C, wastes, antibodies, microbe-killing protein, weak acid

Apocrine Glands

Mostly in axillary and anogenital areas. Starts at puberty.

Larger glands that lie deeper in the dermis or in hypodermis.

Ducts usually empty into hair follicle.

Sweat has more fat and protein so milky/yellowish which has odor from microbes degrade it (ALWAYS SMELLS!)

Activated during pain and stress, may be equivalent to animal sexual scent glands.

Mammary glands secrete milk.

Apocrine Gland: Ceruminous Glands

In lining of external ear.

Secretion mixes with sebum/oil to form cerumen (earwax for protection)

Sebaceous Glands

Oil glands, largest on face, neck, and upper chest.

Alveolar glands all over except palms and soles.

Secrete sebum when burst (holocrine glands)

Most are attached to hair follicles.

Hormones influence.

Sebum

Softens and lubricates skin and hair, prevents brittle hair, slows water loss, antimicrobial

Integumentary system: Protection LEFT OFF ON SLIDE 47

Chemical barrier, from secretions that kill microorganisms and form acid covering/mantle slows microorganism growth & melanin for UV protection.