The integumentary System

Papillary layer

this layer of the dermis is composed of areolar tissue. This layer contains all the capillaries, lymphatic vessels, and sensory neurons that supply the surface of the skin.

Cleavage Lines

Cleavage lines is the term for the resulting pattern of fiber bundles in the skin. These bundles are arranged parallel to each other and are oriented to resist the forces applied to skin during movement. - Cutting parallel to cleavage lines ensures faster healing and will usually remain closed.

Stratum Lucidum

Lucidum- 'clear layer' - The cells in this layer are flattened, densely packed, largely without organelles, and filled with keratin.

Melanin

a pigment produced by melanocytes. Two types of melanin: 1. pheomelanin- a red-yellow form 2. eumelanin- a brown/black form - The melanin in keratinocytes protect the epidermis and dermis from ultraviolet radiation.

Dermatitis

an inflammation of the skin that occurs primarily in the papillary layer.

Epidermal growth factor (EGF)

is a peptide factor. It's produced by the salivary glands and gland of the duodenum. Roles of EGF include: - promoting division of basal cells in stratum basale and stratum spinosum. - Accelerating the production of keratin in differentiating keratinocytes - Stimulating epidermal development and epidermal repair after injury - stimulating synthetic activity and excretion by epithelial glands

The cutaneous plexus

is deeper, along the border of the hypodermis with the reticular layer of the dermis. This plexus supplies both the adipose tissues of the subcutaneous layer, and the tissues of the integument. - Once these arteries reach the papillary layer, they form another plexus called the subpapillary plexus.

Melanocytes

located in the stratum basal. melanocytes manufacture melanin from the amino acid tyrosine.

Ceruminous glands

modified sweat glands in the passageways of the external ear. Combines with nearby sebaceous glands to form cerumen, or earwax.

The Subpapillary Plexus

supplies arterial blood to capillary loops that follow the dermis/epidermis boundary. They then empty into small veins of the SP after which it drains into accompanying arteries of the CP. This connects to larger veins in the hypodermic

Keratinocytes

the body's most abundant epithelial cells and they dominate the epidermis.

Cyanosis

when the skin takes on a blueish coloration during a sustained reduction in circulatory supply.

hypodermis

- Boundary between HD and the dermis is indistinct due to the reticular layer's connective tissue fibers being extensively interwoven with those of the HD. - NOT part of the integument! - Importance lies in stabilizing the position of the skin in relation to underlying tissues, while permitting independent movement. - Very Elastic - Consists of areolar tissue and adipose tissue (subcutaneous fat). 80% of the body's fat is subcutaneous. - Contains a substantial amount of blood - "blood reservoir"

Stratum Spinosum

- Consists of 8-10 layers keratinocytes bound together by desmosomes. The name Spinosum means 'spiny layer'. - contains dendritic cells which stimulate defense against microorganisms that can penetrate this deep, as well defend against superficial skin cancers.

Stratum Basale

- Deepest later of the epidermis - Is attached to the basement membrane by Hemidesmosomes. This is where the epidermis and dermis meet. The Stratum basal actually interlocks with the dermis which increases the strength of the bond between the two. Here, epidermal ridges extend into the dermis and are adjacent to dermal projections called dermal papillae, which . Sorta looks like a zipper. - Basal cells dominate the stratum basale - Merkel cells are special tactile cells - A merkel cell together with a sensory nerve terminal is called a tactile disc. This is responsible foe the sensation of touch

Hair

- Hair production begins at the hair bulb, which surrounds a small hair papilla (a peg of connective tissue containing capillaries and nerves). - A layer of epithelial cells at the base of the hair bulb is called the hair matrix. As these cells divide, they produce daughter cells that are gradually pushed towards the surface. - The daughter cells create: 1. The medulla (core of hair) 2. The cortex (intermediate layer) 3. the cuticle (cells at the edge which become the surface of hair) - The follicle walls are made up of several layers of epithelial cells. Moving outward, they are: 1. the internal root sheath 2. the external root sheath 3. the glassy membrane

Reticular layer

- The Reticular layer (of the dermis) is made of an interwoven meshwork of dense irregular connective tissue containing collagen and elastic fibers. Accessory structures from the epidermis extend here (hair follicles, glands)

Effects of Aging

- The epidermis thins as basic cell activity declines - Number of dendritic cells decreases to about 50 percent of levels seen at age 21 - Vitamin D3 production declines by about 75 percent - melanocyte activity decreases - glandular activity declines - blood supply to the dermis is reduced - Hair follicles stop functioning or produce thinner, finer hairs - The dermis thinsm and the elastic fiber network decreases in size - With changes in levels of sex hormones, secondary characteristics in hair and body fat distribution begin to fade - skin repairs proceed more slowly

calcitriol

- The liver converts cholecalciferol into calcitriol. Calcitriol is essential for the normal absorption of calcium and phosphorus in the small intestine.

cholecalciferol

- When exposed to UV radiation, epidermal cells in the stratum spinosum and stratum basale convert a cholesterol related steroid into cholecalciferol aka vitamin d3.

Stratum Corneum

- contains 15-30 layers of keratinized cells. - Keratinization is the formation of protective, superficial layers of cells filled with keratin. - All these dead cells are tightly interconnected by desmosomes. - takes 7-10 days for cells to move from stratum basale to stratum corneum - Insensible perspiration accounts for 500 mL (1 pint) of water loss each day

Stratum Granulosum

Graulosum- 'grainy layer' - made up of 3-5 layers of keratinocytes derived from stratum spinosum. - is basically a tightly interlocking layer of cells that consist of keratin fibers surrounded by keratohyalin

Sebaceous Glands

Sebaceous glands or oil glands, are holocrine glands that discharge an oily lipid secretion into hair follicles. - This is done through holocrine secretion, which involves the rupture of secretory cells - The secreted lipid product is called sebum- a mixture of triglycerides, cholesterol, proteins, and electrolytes.. -Function: - Sebum inhibits growth of bacteria, lubricates and protects the keratin of the hair shaft, and conditions the surroundig skin

Innervation of the skin

The Dermis contains similar receptors to the epidermis, as well as more specialized receptors.

Dermis

The Dermis lies between the epidermis and the hypodermis. It has two major components: 1. the Papillary layer (superficial) 2. the reticular layer (deep)

The Dermal Blood Supply

The arteries that supply the skin are located deep within the hypodermis. - The branches of these arteries form two plexuses (networks): the cutaneous plexus, and the subpapillary plexus. - The SP supplies arterial blood to capillary loops that follow the dermis/epidermis boundary. They then empty into small veins of the SP after which it drains into accompanying arteries of the CP. This connects to larger veins in the hypodermic

Dermal Strength and elasticity

The dermis derives its strength from collagen and elastic fibers. - Collagen fibers are very strong and resist stretching, but are easily bent or twisted - Elastic fibers permit stretching and then recoil to their original length - The water content of skin helps maintain its flexibility and resistance. - Skin turgor is the term to refer to these properties collectively

Sweat Glands

The skin contains two types of sweat glands or sudoriferous glands: 1. Apocrine sweat glands- found around the nipples, armpits, and in the pubic region - begin secreting at puberty - Special myoepithelial cells contract and squeeze the gland, causing the accumulated sweat to discharge onto the hair follicles 2. Merocrine sweat glands- also know as eccrine sweat glands- - discharge their secretions directly onto the surface of the skin - far more numerous than apocrine sweat glands. - Palms and soles have the highest numbers Functions: 1. cooling the surface of the skin 2. exerting water and electrolytes 3. providing protection from environmental hazards

Phases of Injury repair

There are four phases in the regeneration of skin after an injury 1. Inflammatory Phase- triggered by mast cells in the region. Swelling, redness, and pain occur. 2. Migratory phase- blood clot/scab forms- phagocytic cells are removing debris and enhanced circulation brings more of these cells to the area 3. Proliferation phase- scab is undermined by epidermal cells migrating over the collagen fiber meshwork produced by fibroblasts 4. Scarring phase- Scar tissue is formed- it is flexible, fibrous and noncellular. This completes the repair process. Sometimes scar tissues forms beyond what is necessary forming a keloid

- Sebaceous follicles

large sebaceous glands that are not associated with hair follicles. Their ducts discharge sebum directly onto the epidermis.

Nails

protect the tips of fingers and toes, as well as helping to limit distortion of digits from mechanical stress Nails are made of - the nail body - the visible portion of the nail, covers an area of epidermis called the nail bed. The nail body consists of dead, tightly compressed cells packed with keratin - The nail bed is bordered on either side by lateral nail folds and lateral nail folds - The distal part of the nail past the nail bed is called the free edge. It extends over the hyponychium, which is an area of thickened stratum corneum Nail production takes place at the nail root. The deepest portion of the nail root lies very close to the bone of the fingertip. - A portion of the stratum corneum of the nail root extends over the exposed nail forming the eponychim, or cuticle. - The lunula is the pale crescent of the fingernail

Lamellated (pacinian) corpuscles

receptors sensitive to deep pressure and vibration. Located in the reticular layer.

Tactile (Meissner's) corpuscles

receptors sensitive to light touch. Located in the dermal papillae