Ch. 5 The Integumentary System Flashcards Preview

Human Anatomy > Ch. 5 The Integumentary System > Flashcards

Flashcards in Ch. 5 The Integumentary System Deck (33):

Functions of the Skin

- thermoregulation (sweat glands, vasodilation (loss heat), vasoconstriction)
- blood reservoir (mainly dermis)
- protection from external environment
- cutaneous sensations
- excretion and absorption
- synthesis of vitamin D



outer, thinner layer that consists of keratinized stratified squamous Epithelium; consists of four principle cells:
1. keratinocytes: (90% of cells) produce keratin which provides protection against microbes, chemicals, heat and abrasion
2. Melanocytes: (8%) produce the pigment, melanin that protects against damage by ultraviolet radiation
3. Langerhans cells: (intraepidermal macrophage cells) arise from red bone marrow and involved in immune responses, damaged by UV light
4. Merkel cells: (tactile cells) deepest layer of the epidermis, function in the sensation of touch along with the adjacent tactile (merkel) discs


Stratum Basale

deepest layer of epidermis, continuous cell division to produce keratinocytes
nuclei are large with abundant ribosomes, small Golgi complex and few mitochondria
intermediate filaments keratin protect deeper layers from injury
melanocytes and Merkel cells are found in this layer


Facts about the skin

- covers the body and is the largest organ of the body by surface area and weight
- 2 square meters and weighs 4.5-5kg and form about 7% of body weight
- .5-4mm thick, thinnest on the eyelids, thickest on the heels; average thickness is 1-2mm
- skin is organ because it performs a specific function, blood vessels, nerves


Stratum Spinosum

- 8-10 layers of thorn-like keratinocytes with bundles of tonofilaments
- cells in superficial layers are flat
- intermediate keratin filaments are present, provides strength and stability
- melanocytes and Langerhans cells are present and include arm-like processes


Stratum Granulosum

- 3-5 rows of flattened keratinocytes undergoing apoptosis
- keratohyalin converts keratin intermediate filaments into keratin
- lamellar granules fuse with the plasma membrane and release a lipid-rich water repellent secretion
- granules prevent water loss and microbe entry


Stratum Lucidum

- present in only thick skin areas (fingertips, palms, soles)
- 4-6 layers of clear, flat, dead keratinocytes containing large amount of keratin and thickened plasma membrane
- parallel arrangement of keratin provides an additional level of toughness in thick skin


Stratum Corneum

- 25-30 layers of flattened dead keratinocytes
- cells are extremely thin, flat, plasma-membrane-enclosed packages of keratin called corneocytes or squames that are shed and replaced by cells from the deeper strata
- protect deeper layers
- constant friction stimulates increased cell production and keratin developing a callus (thickening of skin)



- composed of dense irregular connective tissue
- collagen and elastic fibers provides tensile strength
- divided into two layers


Papillary Region

- 1/5 of the thickness of the dermis, superficial layer
- consists of areolar connective tissue containing thin collagen and elastic fibers, dermal papillae (undersurface, taller and numerous in sensative regions), capillary loops, corpuscles of touch (Meissner's corpuscles), and free nerve endings detect cool, warm, tickle, pain and itching


Reticular Region

- attached to subcutaneous layer, contains bundles of thick collagen and elastic fibers (dense irregular tissue), adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands, blood vessels
- tension lines in the skin indicate predominant direction of underlying collagen fibers
- provides extensibility and elasticity, striae appear when stretched too much



extensive stretching of the collagenous fibers (internal damage) within dermis causes stretch marks
- obesity, pregnancy, and weight lifting



loosening of both layers of dermis causes wrinkles and increases with the age of a person


Lines of Cleavage

- underlying collagen fibers tend to orient more in one direction than another in reticular region
- predominant in palmar surface of fingers and are arranged in parallel to long axis of the digits
- important to plastic surgeons



- yellow-red or brown-black pigment produced by melanocytes (located mostly in the epidermis where it absorbs UV radition)
- amount of melanin causes the skin's color to vary from pale yellow to red to tan to black
- melanocytes are more concentrated in the skin of penis, nipple, areolae, face and limbs
- melanocytes are about same in number in all people, skin color is due to the amount of melanocytes produced
- freckles are accumulation of melanin



oxygen-carrying pigment in red blood cells; located in erythrocytes flowing through dermal capillaries



yellow-orange pigment found in the stratum corneum, dermis, and subcutaneous layer


Subcutaneous Layer

- not part of the skin but among its functions
- attaches the skin to the underlying tissues and organs
- areolar tissue or fiberous collagen fibers with adipose tissue
- contain lamellated (pacinian) corpuscles which detect external pressure applied to skin
- storage depot for fat and contains large blood vessels



local, harmless overgrown of melanin-forming cells
can become malignant upon exposure to excessive UV light



- yellowish or brown spot that represent localized areas of excessive melanocyte activity
- degree of pigmentation varies and depends on both sun exposure and heredity



- congenial anomaly that results in skin discolouration due to blood vessels that proliferate and form a benign tumour
- capillary hemangiomas (strawberry-colored birth marks)
- cavernous hemangiomas (port-wine stains)


Hair Characteristics

- protection, reduction of heat loss, sensing light touch
- composed of dead, keratinized epidermal cells
- shaft: superficial portion of the hair, projects from the surface of the skin
- root: penetrates into the dermis
- hair follicle: surrounds the root; consists of an epithelial root sheath which in turn is surrounded by a dermal root sheath


Papilla of the Hair

located at the base of a hair follicle is the bulb; it has an indentation called the papilla of the hair where blood vessels provide nourishment to the growing hair


Hair Matrix

- part of bulb
- arise from stratum basale, the cite of cell division
- gives rise to the cells of the internal root sheath (forms cellular tubular sheath of epithelium between external root sheath and the hair), hair colour (melanocytes)


Arrector Pili

- extends from the superficial dermis of the skin to the connective tissue sheath around the hair follicle
- nerve endings stimulate the arrector pili muscles to contract, pulling hair shafts perpendicular to surface (goosebumps)
- insulate or look intimidating


Hair Root Plexus

-sensitive to touch, initiates nerve impulse if hair shaft is moved
- dendrites of neurons surrounding each hair follicle


Sebaceous Glands

-oil glands, simple branched acinar glands connected to hair folicle
- lining of cuboidal cells, secrete an oily substance called sebum, which prevents dehydration of hair and skin
- inhibits growth of certain bacteria


Sudoriferous Glands

- produce sweat by exocytosis through pores of into hair follicles
- eccrine or apocrine sweat glands


Eccrine (merocrine) sweat glands

- simple, soiled tubular glands, located deep dermis
- an excretory duct that opens at a pore at the surface of the epidermis
- more common than apocrine glands
- sweat helps to cool body by evaporating, insensible perspiration (evaporates before perceived) sensible perspiration (larger amounts and is seen as moisture)
- eliminates small amounts of wastes
- not on margin of lips, nail bed, glans penis, clitoris, labia minora, and eardrum


Apocrine Sweat Glands

- emotional sweating or cold sweat and sexual excitement
- larger ducts and lumens
- found mainly in skin of the axilla, groin, areolae, and bearded facial regions of adult males
- decompose proteins which causes body odor
- enlarge during ovulation and shrink during menstruation, become active only after puberty


Ceruminous Glands

- modified sweat glands located in the ear canal; and nearby sebaceous glands
- produce waxy substance called cerumen (ear wax) which provides a sticky barrier that prevents entry of foreign bodies into the ear canal



- composed of hard, keratinized epidermal cells located over the dorsal surfaces of the ends of fingers and toes
- nail body: visible portion of the nail, does not shed
- free edge: extend past the distal end of the digit
- nail root: buried in a fold of skin
- lunula: whitish, crecent-shaped area of the proximal end of nail body
- hyponychium: secures nail to fingertip
- eponychium: cuticle is a narrow band of epidermis that adheres to the margin of nail wall
- nail matrix: cell division occurs resulting in growth of nail


Functions of Nails

- help grasp and manipulate things
- protect against trauma to the ends of the digits
- scratching
- provide support and counter pressure to the palmar surface of the finger to enhance touch perception and manipulation