Lab 3- Tissues and Integumentary Sys. Flashcards
What are the two distinct regions of the skin?
epidermis: composed of epithelium and an underlying connective tissue; and the dermis
What part is deep to the dermis?
subcutaneous layer or hypodermis; which is not considered part of the skin; consists primarily of adipose tissue
Epidermis
avascular; keratinized stratified squamous epithelium; consits of four distinct cells types and four or five distinct layers
What are the cells of the epidermis?
keratinocytes, melanocytes, dendritic cells, and tactile epithelial cells
Keratinocytes
most abundant epidermial cells; produce keratin fibrils; keratin is a fibrous protein that gives the epidermis its durability and protective capabilites; keratinocytes are tightly connected by desmoses
Melanocytes
spidery balck cells that produce the brown to black pigment called melanin; melanin protects against ultraviolet radiation (UVR)
Dendritic Cells
aka Langerhans cells; arise form the bone marrow and migrate to the epidermis; they ingest foreign sibstances and play a key role in activating the immune response
Tactile Epithelial Cells
occasional spiky hemispheres that, in combination with sensory nerve endings, form sensitive touch receptors located at the epidermal-dermal junction
How many layers are in thin skin?
4
How many layers are found in thick skin?
5; added stratum lucidum
What are the layers of the epidermis from deep to superficial?
stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum
Stratum Corneum
horny layer; the outermost layer consisting of 20-30 layers of dead, scalelike keratinocytes; they are constantly being exfoliated and replaced by the division of deeper cells
Stratum Lucidum
clear layer; present only in thick skin; a very thing transparent band of falttened, dead keratinocytes with indistinct boundaries
Stratum Granulosum
granular layer; a think layer named for the abundant granules its cells contain; these granules are 1) lamellar granules, which contain a waterproofing glycolipid that is secreted in the extracellular space; and 2) keratohylaine granules, which help to form keratin in the more superficial layers; at the upper border of this layer, the cells are beginning to die
Stratum Spinosum
spiny layer; serveral layers of cells that contain thick, weblike bundles of intermediate filaments made of a pre-keratin protein; the cells in this layer appear spiky because when tissue is prepared, the cells shrink, but their desmosomes hold tight to adjacent cells; cells in this layer and the basal layer are the only ones to receive adequate nourishment from diffusion of nutrients from the dermis
Stratum Basale
basal layer; a single row of cells immediately above the dermis; its cells are constantly undergoing mitosis to form new cells, hence it alternate name stratum germinativum; some 10-25% of the cells in this layer are melanocytes, which thread their processes through this and adjacent layers of keratinocytes; occasional tactile epithelial cells are also present in this layer
What are the two regions of the dermis?
papillary and reticular areas
Papillary Dermis
more superficial dermal region composed of areolar tissue; uneven and has fingerlike projections from it superior surface; abundant capillary networks allow nutrients and allow heat to radiate to the skin surface; pain receptors (free nerve ending) and touch receptors (tactile corpuscles) found here
Dermal Papillae
attach papillary dermis to the epidermis above; uneven fingerlike projections ; these projections lie on top of the larger dermal ridges; they produce fingerpronts
Reticular Dermis
deepest skin layer; composed of dense irregular connective tissue and contains many arteries and veins, sweat and sebaceous glands, and pressure receptors (lamellar corpuscles)
What results in skin color?
relative amount of melanin and carotene in the skin; degree of oxygenation of the blood
Carotene
yellow orange pigment present primarily in the stratum corneum and in the adipose tissue of the hypodermis
What are the accessory organs of the skin?
cutaneous glands, hair, and nails ; they originate from the stratum basale and extend into the dermis
Nails and their Parts
are hornlike derivatives of the epidermis; nail plate, free edge, hyponychium, nail root, nail folds, eponychium, nail bed, nail amtrix, lunule
Nail Plate
the visible attached portion
Free Edge
the port of the nail that grow out away from the body
Hyponychium
the region beneath the free edge of the nail
Nail Root
part that is embedded in the skin and adheres to an epithelial nail bed
Nail Folds
skin folds that overlap the borders of the nail
Eponychium
projection of the thick proximal nail fold commonly called the cuticle
Nail Bed
extension of the stratum basal beneath the nailN
Nail Matrix
thickened proximal part of the nail bed containing germinal cells responsible for nail growth; as the matrix produces the nail cells, they become heavily keratinized an die
Lunule
proximal region of the thickened nail matrix (appears as a white crescent moon)
What are the color of nails and why do they appear that way?
nails are transparent and nearly colorless but they appear pink because of the blood supply in the underlying dermis
Where is hair not found?
thick skinned areas (palms of the hands and soles of the feet) and parts of the external genitalia, nipple, and lips
What are the two primary regions of hair?
hair shaft: the region projecting from the surface of the skin; and the hair root: which is beneath the ruface of the skin and is embedded within the hair follicle
Hair Bulb
collection of well-nourished epithelial cells at the base of the hair follicle
Hair Follicle
structure formed from both epidermal and ermal cells; epithelial sheath is enclosed by a thickened basement membrane, the glassy membrane and by a peripheral connective tissue or fibrous sheath
Hair Papilla
snall nipple of dermal tissue protruding into the ahir from the peripheral connective tissue sheath and provides nutrients to the growing hair
Hair Matrix
layer of acitvely dividing epithelial cells located on top of the hair papilla
Arrector Pili Muscle
small bands of smooth muscle cells connect eahc hair follicle to the papillary layer of the dermis; when theu contract the slanted hair follice is pulled up right causing coose bumbs
What are the two categories of cutaneous glands?
sebaceous and sweat glans
Sebaceous Glands
oil glands; found nearly all over the skin (except for the palms of the hands and soles of the feet); ducts usually empty into a hair follicle but some open directly on the skin surface; become particulary active during puberty, when more male hormones (androgens) begin to be produced for both genders; this the skin becomes oilier during this period
Sebum
product of sebaceous glands; mixture of oily substance and fragmented cells that acts as a lubricant to keep the skin soft and moist (natural skin cream) and keeps the hair from becoming brittle
Sudoriferous Glands
sweat glands; exocrine glands that are widely distributed all over the skin; outlets for the glands are epithelial openings called pores; sweat glands are caegorized by the compostition of their secretions
Eccrine Sweat Glands
aka merocrine sweat glands; these are distributed all over the body; produce a clear secretion consisting primarily of water, salts, and urea; important part of bodys heat regulating apparatus (which is controlled by the nervous sys)
Apocrine Sweat Glands
found predominantly in the axillary and genital area; these secrete the basic components of eccrine sweat plus proteins and fat-rich substances; excellent nutrient medium for the microorganisms typically found on the skin; initially odorless but when bacteria break down its organic components it begins to smell
