Integumentary System Sheet-like membranes of epithelium, connective tissue, and other organs.
Chapter 6: The integumentary System. Integumentary System Composed of the cutaneous membrane with...
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Transcript of Chapter 6: The integumentary System. Integumentary System Composed of the cutaneous membrane with...
Chapter 6: The integumentary System
Integumentary System
Composed of the cutaneous membrane with certain accessory organs
4 Major Types of Membranes Serous membrane Mucous membranes Synovial membranes Cutaneous membrane
Serous MembranesLine body cavities that lack openings to the
outside of the body
Form the inner linings of the thorax and abdomen
Consists of a layer of simple squamous epithelium & a thin layer of loose connective tissue
Cells of a serous membrane secrete watery serous fluid which lubricates membrane surfaces
Mucous membranesLine cavities & tubes that open to the outside
of the body
Include the oral & nasal cavities & the tubes of the digestive, respiratory, urinary, and reproductive systems
Specialized cells within a mucous membrane secrete mucus
Synovial membranesForm inner linings of the joint cavities between
the ends of bones at freely movable joints (synovial joints)
Usually include dense connective tissue that overlies loose connective tissue and adipose tissue
Cells secrete a thick, colorless synovial fluid into the joint cavity this lubricates the ends of the bones within the joint
Cutaneous MembraneMore commonly called skin
Skin & its tissues (figure 6.1)
The skin is the largest and one of the more versatile organs of the body
Plays a major role in maintaining the body’s homeostasis
Includes 2 distinct tissue layers: Epidermis outer layer, composed of stratified squamous epithelium Dermis inner layer, thicker than the epidermis & it contains connective
tissue, epithelial tissue, smooth muscle tissue, nervous tissue, & blood
Basement membrane that is anchored to the dermis separates the two skin layers
Masses of loose connective & adipose tissues that bind the skin to the underlying organs these tissues form the subcutaneous layer (hypodermis)
Epidermis
Lacks blood vessels but the deepest layer of epidermal cells (stratum basale) is close to the dermis and is nourished by its blood vessels
As the cells divide and grow, the older cells are pushed away from the dermis toward the skin surface
The farther away, the poorer the nutrient supply becomes, in time they die
Older cells (keratinocytes) harden in a process called keratinization Cytoplasm fills with strands of a tough, fibrous, waterproof keratin protein Many layers accumulate in the outer epidermis this forms the stratum
corneum (outermost layer of the epidermis) Dead cells are often rubbed away
Epidermis Important protective functions:
Shields moist underlying tissues against excessive water loss, mechanical injury, and the effects of harmful chemicals
Keeps out disease-causing microorganisms when unbroken
Epidermis
Melanocytes – specialized cells that produce melanin (a dark pigment that provides skin color)
Absorbs light energy which helps protect deeper cells from the damaging effects of ultraviolet radiation in sunlight
Melanocytes lie in the deepest portion of the epidermis & in connective tissue of the dermis
Skin color
Due largely to melanin
Differences in skin color result from: Differences in the amount of melanin produced Genetics Environmental and physiological factors
Blood may also affect skin color as physiological changes occur Well oxygenated blood has hemoglobin that is bright red pinkish color
in light-complexioned people Low concentration of oxygen in blood causes hemoglobin to be dark red
makes the skin appear blue (cyanosis)
Skin colorMelanin – yellow to reddish-brown to black
pigment, responsible for dark skin colors
Carotene – yellow to orange pigment, most obvious in the palms and soles of the feet
Hemoglobin – reddish pigment responsible for the pinkish hue of the skin
DermisBinds the epidermis to underlying tissues
Composed largely of dense connective tissue that includes tough collagenous fibers & elastic fibers in a gel-like ground substance Gives the skin its toughness & elasticity
Dermal blood vessels supply nutrients to all skin cells and help regulate body temperature
Nerve fibers carry impulses out from the brain to dermal muscles & glands
Sensory fibers carry impulses away from specialized sensory receptors to the brain (ex touch receptors)
Contain hair follicles, sebaceous (oil-producing) glands, & sweat glands
Subcutaneous layerAlso called the hypodermis (beneath the
dermis)
Consists of loose connective & adipose tissues
The adipose tissue insulates which helps conserve body heat and impedes the entrance of heat from the outside
Accessory Organs of the skinHair Follicles
Sebaceous Glands
Nails
Sweat Glands
Hair (figure 6.4)Filamentous strands of dead keratinized cells produced by hair
follicles
Contains hard keratin which is tougher and more durable than soft keratin of the skin
Made up of the shaft projecting from the skin, and the root embedded in the skin
Consists of a core called the medulla, a cortex, and an outermost cuticle
Pigmented by melanocytes at the base of the hair
Hair function & distributionFunctions of hair include:
Helping to maintain warmth Alerting the body to presence of insects on the
skin Guarding the scalp against physical trauma, heat
loss, and sunlight
Hair function & distributionHair is distributed over the entire skin surface
except: Palms, soles, and lips Mammaries & portions of the external genitalia
Sebaceous glandsSimple alveolar glands found all over the body
(except palms & soles)
Soften skin when stimulated by hormones
Secrete an oily secretion called sebum Keeps the hair and skin soft, pliable, and
waterproof
Sebaceous GlandsCan be found next to hair follicles
Functions: Lubricates hair & skin, collects dirt, layer of
protection, kills bacteria, prevents water loss
Acne – gland becomes blocked because too much sebum is produced Androgens – hormone that stimulates sebum
production Ex) puberty
Pimple forms when pore is infected & inflammation occurs
Sweat glandsAre exocrine glands
Different types prevent overheating of the body
Eccrine Glands
Apocrine Glands
Ceruminous Glands
Mammary Glands
Eccrine Sweat GlandsMost numerous of the sweat glands
Respond when the body experiences elevated temperatures due to heat or physical exercise
Found on the forehead, neck, and back
Apocrine sweat GlandsBecome active when a person is emotionally
upset, frightened, stressed, or in pain
Can activate during physical activity or elevated body temperature
Found in axillary regions and groin
Ceruminous glandsModified apocrine gland
Found in the external ear canal
Secretes earwax
Mammary glandSpecialized type of sweat gland that secretes
milk in females
Nails
Protective coverings on the ends of fingers and toes
Consist of keratinized stratified squamous epithelial cells w/ very hard keratin
Form by cell division in the nail root
The most active growing region of the nail is the whitish half-moon-shaped area at the base of the nail (lunula)
As nails develop they slide forward over the nail bed; the nail is attached to it
Healing of wounds
The specific events in healing depend on the severity and extent of the injury
A shallow break in the skin causes epithelial cells to divide more rapidly than usual so the cells fill the gap
Deeper breaks into the dermis or subcutaneous layer may break blood vessels Escaping blood forms a clot in the wound which dries and forms a scab
covering the wound Fibroblasts migrate into the injured area and begin forming new
collagenous fibers that bind the edges of the wound together If the wound is extensive, newly formed connective tissue may appear on
the surface as a scar
Skin cancer
Most skin tumors are benign and do not metastasize
A crucial risk factor for non-melanoma skin cancers is the disabling of the p53 gene
Newly developed skin lotions can fix damaged DNA
Skin CancerThe three major types of skin cancer are:
Basal cell carcinoma Squamous cell carcinoma Melanoma
Basal cell carcinoma Least malignant and most common skin cancer
Stratum basale cells proliferate and invade the dermis and hypodermis (located in the stratum basale)
Slow growing and do not often metastasize
Can be cured by surgical excision in 99% of the cases
Develops a central ulcer
Attracts blood vessels which then take away nutrients from the body
Squamous cell carcinomaArises from keratinocytes of stratum spinosum
Arise most often on scalp, ears, and lower lip
Grows rapidly and metastasizes if not removed
Prognosis is good if treated by radiation therapy or removed surgically
MelanomaCancer of melanocytes is the most dangerous
type of skin cancer because it is: Highly metastatic Resistant to chemotherapy
Ex) moles
MelanomaMelanomas have the following characteristics
(ABCD rule) A: Asymmetry; the two sides of the pigmented
area do not match B: Border is irregular and exhibits indentations C: Color (pigmented area) is black, brown, tan, and
sometimes red or blue D: Diameter is larger than 6 mm (size of a pencil
eraser)
MelanomaTreated by a wide surgical excision
accompanied by immunotherapy
Chance of survival is poor if the lesion is over 4 mm thick
BurnsFirst-degree – only the epidermis is damaged
Symptoms include localized redness, swelling, and pain
Ex) sunburn
Can be caused by heat, chemicals, friction, electrical
BurnsSecond-degree – epidermis and upper regions
of dermis are damaged Symptoms mimic first-degree burns, but blisters
also appear Takes 3-4 weeks to heal Little scarring occurs
burnsThird-degree – entire thickness of the skin is
damaged Burned area appears gray-white, cherry red, or
black; there is no initial edema or pain (since nerve endings are destroyed)
Skin graft is usually needed