epidermis, dermis, hypodermis

Epidermis

it is keratinized stratified squamous epithelium that contains four distinct cells: Keratinocytes, melanocytes, tactile epithelial cells and dendritic cells.

Primary function of the skin

Protection: Skin cushions and insulates the deeper body organs and protects the body from bumps, scrapes, and cuts.

Body temperature regulation: the skin’s rich capillary networks and sweat glands regulate the loss of heat from the body, helping to control body temperatures

Excretion: The skin acts as a miniature excretory system when urea, salts, and water are lost through sweat.

Production of Vitamin: The epidermal cells use UV radiation to synthesize vitamin D, a molecule necessary for absorbing calcium from the digestive tract

Sensory reception: The skin contains sense organs called sensory receptors that are associated with nerve endings.

Name the five principles function of the skin

Protection, body temperature regulation, excretion, production of vitamin D, sensory reception.

stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale.

Epidermis is divided into five layer, name them

Keratinocytes

the most abundant epidermal cell, produce keratin, a tough fibrous protein that gives the epidermis its protective properties.

35 to 45 days—the average time from the birth of a keratinocyte to its final wearing away.

stratum basale

the deepest epidermal layer, is firmly attached to the underlying dermis along a wavy borderline. it consists of a single row of cells, mostly stem cells representing the youngest keratinocytes

stratum spinosum

is several cell layers thick (Figure 5.3). Mitosis occurs here, but less often than in the basale layer. Dendritic cells are found in here

stratum granulosum

thin layer consists of one to five layers of flattened keratinocytes. Along with abundant pre-keratin intermediate filaments, these cells also contain keratohyalin granules and lamellar granules

stratum lucidum

occurs in thick skin but not in thin skin.

stratum corneum

The most external part of the epidermis, it is many cells thick. It is much thicker in thick skin than in thin skin

Dendritic cells

These star-shaped cells are part of the immune system.

Melanocytes

Make the dark skin pigment melanin. Found in the stratum basale

Tactile epithelial cells, or Merkel

cells, are distributed sparsely among the keratinocytes.

Keratinocytes

found in every layer of the epidermis.

The dermis,

the second major region of the skin, is a strong, flexible connective tissue. The cells of the dermis are typical of any connective tissue proper: fibroblasts, macrophages, mast cells, and scattered white blood cells

The dermis has two regions:

the papillary dermis and the reticular dermis

The papillary dermis

the superficial 20% of the dermis, is areolar connective tissue, containing very thin collagen and elastic fibers. includes dermal papillae

Dermal papillae

fingerlike projections that extend into the overlying epidermis. helps to gas diffusion and to nourish the epithelial tissue.

Reticular dermis

accounts for about 80% of the thickness of the dermis, is dense irregular connective tissue.

dermal plexus

Blood vessel that nourish the hypodermis and deeper dermis

subpapillary plexus

Blood vessels supplying the superficial dermis and epidermis

Subcutaneous

hypodermis or superficial fascia. The subcutaneous tissue consists of both areolar and adipose connective tissue, but adipose tissue normally predominates.

Melanin, Carotene, Hemoglobin

skin colors

Skin appendages

Nails, hair, hair follicles sebaceous glands, sweat glands

Nail matrix

the actively growing part of the nail

hair

is a flexible strand made of dead cells filled with hard keratin

nail

is a scalelike modification of the epidermis that corresponds to the hoof or claw of other mammals

hair follicles

are tubular invaginations of the epidermis from which the hairs grow.

shaft

the part that projects above the skin surface

root

The chief parts of a hair are

Medulla

consists of large cells and air spaces.

cuticle

is a single layer of fattened, overlapping cells, and it prevents hair from matting

Hair follicles

extend from the epidermal surface into the dermis.

hair bulb

A knot of sensory nerve endings wraps around each hair bulb to form a hair follicle receptor or root hair plexus

Sebaceous gland

skin’s oil glands and they produce sebum

Sweat glands

sudoriferous glands, we have two Eccrine gland and Apocrine gland

Eccrine glands

are by far the more numerous type. They are most abundant on the palms, soles, and forehead.

Apocrine glands

are mostly confined to the axillary, anal, and genital areas. They are larger than eccrine glands, and their ducts open into hair follicles. They produce fatty and protein substance that when decomposed it release body odors.

Sodium, ammonia, water, uric acid, and no amino acid

components sweat glands secreted by eccrine glands includes

Holocrine secretion

sebaceous gland go in a process

Mole

what structure is formed when clusters of melanocytes are transformed into melanin-containing cells (nervus cells)

Stratum granulosum

In what location can the epidermal cell type or structure keratohyalin be found

Keratinocytes, dendritic, pre-keratin cells

Stratum spinosum contains all this cells

Hypodermis is made of

Areolar connective tissue and adipose connective tissue

Melanocytes

respond to ultraviolet radiation by increasing the production of melanin