Chapter 5 : Integumentary System (5.1 Vocab (Keros - horn, Cornu - horn,…
Chapter 5 : Integumentary System
Integumentary System: Or simply the integument has two major components ; the cutaneous membrane and accessory structures.
Cutaneous Membrane: also known as skin, is an organ composed of superficial epithelium, or epidermis, and the underlying connective tissues of the dermis.
Accessory Structures: include hair, nails, and a variety of exocrine glands.
Beneath the dermis, the loose connective tissue of the subcutaneous layer, or hypodermis, attaches the integument to deeper structures, such as muscles or bones.
Protection - the skin covers and protects underlying tissues and organs from impacts, chemicals, and infections, and it prevents the loss of body fluids.
Temperature maintenance - the skin maintains normal body temperature by regulating heat exchange with the environment.
Synthesis and storage of nutrients - the epidermis synthesizes vitamin D3, a steroid building block for a hormone that acids calcium uptake. The dermis stores large reserves of lipids in adipose tissue.
Sensory reception - receptors in the integument detect tough, pressure, pain, and organic wastes. Additionally, specialized integumentary glands of the breasts secrete milk.
Thick skin is found on the palms of the hands and soles of the feet, contains five layers. Only four layers make up thick skin, which covers the rest of the body. Thick skin is about as thick as the wall of plastic sandwich bag, whereas thick skin is about as thick as paper.
Cornu - horn
Cutis - skin
Derma - skin
Epi - above or over
Facere - to make
Germinare - to start growing
Keros - horn
Kyanos - blue
Luna - moon
Melas - black
Onyx - nail
Papilla - a nipple shaped mound
Thick skin is found on the palms of the hands and soles of the feet, which contains five layers.
Strata shows the cell layers in a section of thick skin.
The deepest epidermal layer is called the stratum germinativum or stratum basale. The cells of this layer are firmly attached to the basement membrane by hemidesomes. The basement membrane separates the epidermis from the loose connective tissue of the adjacent dermis.
The stratum germinativum forms epidermal ridges, which extend into the dermis, increasing the area of contact between the two regions.
Each time a stem cell divides, one of the resulting daughter cells enters the next layer, the stratum spinosum, where it may continue to divide and add to the thickness of the epithelium.
The stratum granulosum consists of cells displaced from the stratum spinosum.
The cells in this grainy layer have stopped dividing and begin making large amounts of protein keratin. Keratin is extremely durable and water-resistant.
In the thick skin of palms and soles, a glassy stratum lucidum covers the stratum granulosum. The cells in this layer are flattened, densely packed, and filled with keratin.
The most superficial layer of the epidermis, the stratum corneum consists of 15-30 layers of flattened and dead epithelial cells that have accumulated large amounts of keratin.
Such cells are said to be keratinized or cornified. The dead cells in each layer of the stratum corneum remain tightly connected by desmosomes. As a result, the keratinized cells of the stratum corneum are generally shed in large groups or sheets rather than individually.
It takes 2-4 weeks for a cell to move the stratum germinativum to the stratum corneum. During the cell is displaced from it's oxygen and nutrient supply, becomes packed with keratin, and finally dies.
5.2 Factors influencing skin color are epidermal pigmentation and dermal circulation
The color is caused by interaction between the pigments in the epidermis and blood flow in the dermis.
The epidermis contains variable amounts of two pigments, carotene, and melanin. Carotene is an orange-yellowish pigments that normally accumulates in epidermal cells. Carotene pigments are present in a variety of orange-colored vegetables, including carrots and squashes. Eating large amounts of carrots can actually cause the skin of light -skinned individuals to turn orange. The color change is less striking in the skin of darker individuals. Carotene can be converted to vitamin A, which is required for the normal maintenance of epithelial tissues and the synthesis of photoreceptor pigments in the eye.
Melanin is a brown, yellow-brown, or black pigment produced by melanocytes. Melanocytes manufacture and store melanin within intracellular vesicles. These vesicles are transferred to the epithelial cells of the stratum germinativum, coloring the entire epidermis. Melanocyte activity slowly increases in response to sunlight exposure, peaking around 10 days after the initial exposure.
Freckles are small pigmented spots that appear on the skin of pale-skinned individuals. Freckles represent areas of greater-than-average melanin production. They tend to be most abundant on surfaces exposed to the sun, such as the face.
Sunlight contains significant amounts of ultraviolet radiation. A small amount of UV radiation is beneficial because it stimulates the synthesis of vitamin D3 in the epidermis. Too much ultraviolet radiation, however, produces immediate effects of the mild or even serious burns.
Blood without abundant oxygen is bright red, so blood vessels in the dermis normally give the skin a reddish tint that is most apparent in lightly pigmented individuals.
The skin that takes on a bluish coloration called cyanosis.
5.2 vocab ::
ultraviolet radiation (UV) -
integumentary system or integument -
cutaneous membrane or skin -
subcutaneous layer -
5.1 vocab ::
thick skin -
stratum germinativum -
epidermal ridges -
stratum spinosum -
stratum granulosum -
stratum lucidum -
stratum corneum -
keratinized or cornified -
5.3/5.4 The dermis is the tissue layer that supports the epidermis
The dermis lies beneath the epidermis. It has two major components : a superficial papillary layer and a deeper reticular layer.
The papillary layer was named after the dermal papillae, consists of loose connective tissue that supports and nourishes the epidermis. This region contains the capillaries and nerves supplying the surface of the skin.
The deeper reticular layer consists of an interwoven meshwork of dense, irregular connective tissue. Both elastic fibers and collagen fibers are present.
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,
Skin cancers are the most common form of cancer. The more common skin cancer is basale cell carcinoma which originates in the stratum germinativum layer.
Less common are squamous cell carcinomas, which involve more superficial layers of the epidermal cells. Metastasis seldom occurs in either cancer, and most people survive these cancers.
the usual treatment involves surgical removal of the tumor.
Compared with these common and seldom life-threatening cancers, malignant melanomas are extremely dangerous. A melanoma usually begins from a mole but may appear anywhere in the body. In this condition, cancerous melanocytes grow rapidly and metasize through the lymphoid system. The outlook for long term survival depends on when the condition is detected and treated.
Avoiding exposure to UV radiation in sunlight and using a sunblock would largely prevent all three forms of cancer.
Organ systems communicate with the skin through their connections to the dermis. For example, both dermal layers contain a network of blood vessels, lymphatic vessels, and nerve fibers.
Blood vessels provide nutrients and oxygen and remove carbon dioxide and waste products. Both the blood vessels and the lymphatic vessels help local tissues defend and repair themselves after injury or infection.
The nerve fibers control blood flow, adjust gland secretion rates, and monitor sensory receptors in the dermis and the deeper layers of the epidermis.
These receptors, which provide sensations of touch, pain, pressure, and temperature.
An extensive network of connective tissue fibers attaches the dermis to the subcutaneous layer, or hypodermis. The boundary between the two is indistinct, and although the hypodermis is not actually a part of the integument, it is important in stabilizing the position of the skin relative to underlying tissues, such as skeletal muscles or other organs, while permitting independent movement.
The hypodermis consists of loose connective tissue with many fat cells. These adipose cells provide and small children with a layer of "baby fat," which helps them reduce heat loss. Subcutaneous fat also serves as an energy reserve and a shock absorber for the rough and tumble activities for our early years.
As we grow and mature, the distribution of subcutaneous fat changes. Beginning at puberty, men accumulate subcutaneous fat at the neck, upper arms, along the lower back, and over the buttocks.
Hair and several other structures - hair follicles, sebaceous and sweat glands, and nails - are considered accessory structures of the integument.
Hair project above the surface of the skin is almost everywhere except the sides and soles of the feet, the palms of the hands, the sides of the fingers and toes, the lips, and portions of the external genital organs. Hairs are nonliving structures produced in organs called hair follicles.
Hair follicles project deep into the dermis and often extend into underlying subcutaneous layer. The walls of each follicle contain all the cell layers found in the epidermis.
The epithelium at the base of a follicle forms a cap over the hair papilla, a peg of connective tissue containing the capillaries and nerves.
The point at which this occurs is about halfway to the skin surface and marks the boundary between the hair root and the hair shaft. Each hair shaft consists of three layers of dead, keratinized cells.
The surface layer, or cuticle, is made up of an overlapping shingle- like layer of cells.
The underlying layer is called the cortex, and the medulla makes up the core of the hair. The medulla contains a flexible soft keratin; the cortex and cuticle contain thick layers of hard keratin, which give the hair its stiffness.
A bundle of smooth muscle cells forms the arrector pili muscle, which extends from the papillary dermis to the connective tissue sheath that surrounds each hair follicle. When stimulated, the arrector pili pulls on the follicle, forcing the hair to stand up.
Sebaceous glands or oil glands are holocrine glands that 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 sweat glands that secrete their products into hair follicles in the armpits, around the nipples and in the groin are called apocrine sweat glands.
Coiled tubular glands that discharge their secretions directly onto the surface of the skin are merocrine sweat glands or eccrine sweat glands.
Nails form on the dorsal surfaces of the fingers and toes, where they protect the exposed tips and help limit their distortion when they are subjected to mechanical stress.
The visible nail body consists of a dense mass of dead, keratinized cells. The body of the nail covers an area of epidermis called the nail bed. Nail production occurs at the nail root, an epithelial fold not visible from the surface.
A portion of the stratum corneum of the fold extends over the exposed nail nearest the root, forming the cuticle. Underlying blood vessels give the nail its pink color, but near the root these vessels may be obscured, leaving a pale cresent known as the lunula.
The blood clot, or scab, that forms at the surface temporarily restores the integrity of the epidermis and restricts the entry of additional microorganisms.
The combination of blood clot, fibroblasts, and an extensive capillary network is called granulation tissue.
The formation of this rather inflexible, fibrous, noncellular scar tissue can be considered a practical limit to the healing process.
The thickened area of scar tissue, called a keloid, is covered by a shiny, smooth epidermal surface.