Chapter 5 A&P

nail root

The nail is produced at the

Cortex (hair)

The underlying layer of hair is called the

basal cell carcinoma

This cancer originates in the stratum basale, and is the most common skin cancer, which often looks like a waxy bump

stratum spinosum (spiny layer)

This stratum consists of keratinocytes held together by desmosomes. It also contains branched dendritic cells that take part in the immune response.

lunula of the nail

Underlying blood vessels give the nail its pink appearance. Near the root these vessels may be obscured, leaving a pale crescent known as the

Thick skin

found on the palms of the hands and soles of the feet, contains five layers of cells.

Thin skin

has 4 layers and covers all of the body except the palms of the hands and the soles of the feet.

integumentary system (integument)

has two major parts: the cutaneous membrane and accessory structures

accessory structures

include hair, exocrine glands, and nails. They are located primarily in the dermis and protrude through the epidermis to the skin surface

four phases of skin regeneration

inflammatory, migratory, proliferation, scarring

sebum (oil)

inhibits the growth of bacteria, lubricates the hair, and conditions the surrounding skin.

Melanin

is a pigment made by pigment-producing cells called melanocytes (me-LAN-ō-sīts). There are two types of melanin, a red-yellow form and a brown-black form. It protects DNA from the damaging effects of ultraviolet radiation.

cutaneous membrane (skin)

is an organ composed of the superficial epithelium, or epidermis (epi-, above), and the underlying connective tissues of the dermis

Keratin

is extremely durable and water-resistant. In humans, keratin not only coats the surface of the skin but also forms the basic structure of hair, calluses, and nails. In various other animals, it forms structures such as horns and hooves, feathers, and baleen plates

Dermis

lies between the epidermis and the hypodermis. It has two major layers: a superficial papillary layer and a deeper reticular layer

hypodermis, or subcutaneous layer

lies deep to the dermis. The boundary between the two is generally indistinct because the connective tissue fibers of the reticular layer are extensively interwoven with those of the hypodermis. The hypodermis is not a part of the integument, but it is important in stabilizing the position of the skin relative to underlying tissues, such as skeletal muscles or other organs, while permitting them to move independently.

Medulla (hair)

makes up the core of the hair, contains a flexible soft keratin, contains thick layers of hard keratin, which give the hair its stiffness.

Nails

protect the dorsal surfaces of the tips of the fingers and toes (Figure 5-8a). They also help limit distortion of the digits when they are subjected to mechanical stress—for example, when you run or grasp objects.

Apocrine sweat glands

secrete their products into hair follicles in the armpits, around the nipples, and in the pubic region. The name apocrine was originally chosen because it was thought these gland cells use an apocrine method of secretion. We now know that they rely on merocrine secretion, but the name has not changed. At puberty, these glands begin discharging a sticky, cloudy, and potentially odorous secretion. The sweat is a food source for bacteria, which intensify its odor. In other mammals, this odor is an important form of communication. In our culture, whatever function it might have is masked by products such as deodorants. Other products, such as antiperspirants, contain astringent compounds that contract the skin and its sweat gland openings, thereby decreasing the quantity of both apocrine and merocrine secretions.

Hypodermis (subcutaneous layer)

separates the integument from deeper tissues and organs. It is often not considered to be part of the integumentary system, but we include it here because its connective tissue fibers are interwoven with those of the dermis.

strata (singular stratum)

shows the five cell layers in a section of thick skin. In order, from the basement membrane toward the free surface, they are the stratum basale, three intermediate layers (the stratum spinosum, the stratum granulosum, and the stratum lucidum), and the stratum corneum.

epidermal ridges

the stratum basale forms downward waves are extensions of the epidermis that are the cause for fingerprints. The combination of ridges and papillae increases the area of contact between the two regions and strengthens the bond between them. It also increases the available surface area for diffusion of nutrients between the dermis and epidermis.

Cuticle (Hair)

the surface layer of hair is made up of an overlapping shingle-like layer of cells, contains thick layers of hard keratin, which give the hair its stiffness.

carotene

the yellow pigment of the skin

inflammatory, migratory, proliferation, scarring

what are the four phases of skin regeneration?

cyanosis

During a sustained reduction in circulatory supply, the blood in the skin loses oxygen to surrounding tissues and takes on a darker red tone. Seen from the surface, the skin then takes on a bluish coloration called

Protection, Temperature maintenance, Synthesis and storage of nutrients, Sensory reception, Excretion and secretion.

5 major functions of the integument system

5 major functions of the integument system

1Protection. The skin covers and protects underlying tissues and organs from impacts, chemicals, and infections. It also prevents the loss of body fluids. 2Temperature maintenance. The skin maintains normal body temperature by regulating heat exchange with the environment. 3Synthesis and storage of nutrients. The epidermis synthesizes vitamin D3, a steroid building block for a hormone that aids calcium uptake. The dermis stores large reserves of lipids in adipose tissue. 4Sensory reception. Receptors in the integument detect touch, pressure, pain, and temperature stimuli and relay that information to the nervous system. 5Excretion and secretion. Integumentary glands excrete salts, water, and organic wastes. Also, specialized integumentary glands of the breasts secrete milk.

Arrector pili

A bundle of smooth muscle cells forms the muscle. It extends from the papillary dermis to the connective tissue sheath around each hair follicle. When stimulated, the muscle pulls on the follicle, forcing the hair to stand up. Contraction may be caused by emotional states (such as fear or rage) or a response to cold, producing "goose bumps."

cuticle or eponychium

A portion of the stratum corneum of the fold extends over the exposed nail nearest the root, forming the

carcinoma

Any cancer of epithelial tissue is called a

squamous cell carcinomas

Cancer, less common, involves the more superficial layers of epidermal cells.

granulation tissue

If the wound covers an extensive area or involves a region covered by thin skin, dermal repairs must be under way before epithelial cells can cover the surface. Fibroblasts and connective tissue stem cells divide to produce mobile cells that invade the deeper areas of injury. Epithelial cells lining damaged blood vessels also begin to divide, and capillaries follow the fibroblasts, enhancing circulation. The combination of blood clot, fibroblasts, and an extensive capillary network is called

malignant melanomas

In this condition, cancerous melanocytes are extremely dangerous, grow rapidly and metastasize through the lymphatic system. A melanoma usually begins from a mole but may appear anywhere in the body. The outlook for long-term survival depends on when the condition is detected and treated.

Stratum corneum (horny layer)

It normally contains 15-30 layers of flattened and dead epithelial cells packed with filaments of keratin. Such cells are said to be keratinized, or cornified The dead cells in each layer remain tightly connected by desmosomes. As a result, these cells are generally shed in large groups or sheets rather than individually. It takes seven to ten days for a cell to move from the stratum basale to this layer. During this time, the cell is displaced from its oxygen and nutrient supply, becomes filled with keratin, and finally dies. The dead cells usually remain in this layer for two more weeks before they are shed or washed away. As superficial layers are lost, new layers arrive from the underlying strata. Thus, the deeper layers of the epithelium and underlying tissues remain protected by a barrier of dead, durable, and expendable cells. Normally, the surface is relatively dry, so it is unsuitable for the growth of many microorganisms.

Epidermis

The epithelium covering the surface of the skin

Stratum lucidum (clear layer)

Only in thick skin, covers the stratum granulosum. The cells in this layer are flattened, densely packed, and filled with keratin.

Dermis

The connective tissue layer beneath the epidermis of the skin

stratum basale (germinativum)

The deepest epidermal layer Hemidesmosomes attach the cells of this layer firmly to the basement membrane. The basement membrane separates the epidermis from the areolar connective tissue of the adjacent dermis.

hair papilla

a peg of connective tissue containing capillaries and nerves

Intermdeiate Strata

contains 3 layers and sits directly above the basal layer

merocrine sweat glands

are coiled tubular glands that discharge their secretions directly onto the surface of the skin. They are far more numerous and widely distributed than apocrine glands. The skin of an adult contains 2-5 million glands. Palms and soles have the highest numbers. It has been estimated that the palm of the hand has about 500 glands per square centimeter (3000 per square inch).

sebaceous follicles

are large sebaceous glands that discharge sebum directly onto the skin. They are located on the face, back, chest, nipples, and external genitalia.

Keratinocytes

are the body's most abundant epithelial cells. They dominate the epidermis. They form several layers of cells and contain the protein keratin.

reticular layer

consists of an interwoven meshwork of dense irregular connective tissue containing both elastic fibers and collagen fibers. The elastic fibers provide flexibility, and the collagen fibers limit that flexibility to prevent damage to the tissue. Bundles of collagen fibers blend into those of the papillary layer above, blurring the boundary between these layers. Collagen fibers of this layer also extend into the deeper hypodermis.

papillary layer

consists of areolar tissue that supports and nourishes the epidermis. This region contains the capillaries, lymphatic vessels, and sensory neurons that supply the surface of the skin.

stratum granulosum (grainy layer)

consists of cells displaced from the stratum spinosum. They have stopped dividing and have begun making large amounts of the protein keratin

Sebaceous glands or oil glands

discharge an oily lipid secretion into hair follicles or, in some cases, onto the skin . The gland cells produce large quantities of lipids as they mature. The lipid is released through holocrine secretion, a process that involves the rupture and death of the cells. The contraction of the arrector pili muscle that elevates a hair also squeezes the gland, forcing the oily secretions into the hair follicle and onto the surrounding skin. This secretion, called sebum, inhibits the growth of bacteria, lubricates the hair, and conditions the surrounding skin.

basal cells (germinative cells)

dominate the stratum basale. Their continuous division replaces cells that are lost or shed at the epithelial surface.