Tissues Flashcards
Nervous Tissue
conduct impulses that help control and coordinate body activities
Muscle tissue
Contracts to cause movement; includes muscles attached to bone (skeletal), muscles of heart (cardiac), and muscles of walls of hollow organs (smooth)
What are the four tissue types?
Nervous, muscle, epithelial, connective
Epithelial tissue
Forms boundaries between different environments (lines body cavity), protects, secretes, absorbs, filters; includes lining of digestive tract organs and other hollow organs, skin surface (epidermis); lacks blood vessels
Connective tissue
Supports, protects, binds, other tissues together, plus insulates and transports; includes bones, tendons, fat, and blood
Apical surface
The upper free surface of the epithelia tissue, exposed to the body exterior or the cavity of an internal organ
Basal surface
the lower attached region of epithelia tissue
microvilli
fingerlike extensions of the plasma membrane that increase the exposed surface area
cilia
hairlike projections that propel substances along their free surfaces
basal lamina
a think supporting sheet that is adjacent to the basal surface of an epithelium; noncellular, adhesive sheet consists of glycoproteins secreted by the epithelial cells
reticular lamina
a layer of extracellular material containing a fine network of collagen protein fibers that belongs to the underlying connective tissue; located just deep to the basal lamina
basement membrane
reinforces the epithelial sheet, helping to resist stretching and tearing, and defines the epithelial boundary; made up of the two laminae
avascular
contains no blood vessels
innervated
supplied by nerve fibers
simple epithelia
consist of a single cell layer; typically found where absorption, secretion, and filtration occur
stratified epithelia
composed of two or more cell layers stacked on top of each other; common in high-abrasion areas where protection is important (skin surface, lining of mouth)
squamous cells
flattened and scale-like
cuboidal cells
boxlike, approximately as tall as they are wide
columnar cells
tall and column shaped
stratified epithelia
cell shapes differ in the different layers; named according to the shape of the cells in the apical layer
endothelium
slick, friction-reducing lining in lymphatic vessels and in all hollow organs of the cardiovascular system; exceptional thinness encourages efficient exchange of nutrients and wastes btw bloodstream and surrounding tissue cells
mesothelium
epithelium found in serous membranes, which line the ventral body cavity and covering its organs
simple squamous epithelium
flattened laterally; cytoplasm sparse; thin and often permeable; found where FILTRATION or the exchange of substances by rapid DIFFUSION is a priority (capillary walls, kidneys, lungs)
simple cuboidal epithelium
important functions are SECRETION & ABSORPTION; forms the walls of the smallest ducts of glands and of many kidney tubules, ovaries
simple columnar epithelium
lines digestive tract from stomach through rectum; mostly associated with SECRETION & ABSORPTION; ciliated (female reproductive tubes) or nonciliated (uterus; organs of digestive tract)
What two distinctions make the digestive tract lining ideal for secretion and absorption?
dense microvilli on the apical surface of absorptive cells; tubular glands made primarily of cells that secrete mucus-containing intestinal juice
pseudostratified columnar epithelium
cells vary in height; all cells rest on the basement membrane, but only the tallest reach the free surface of th epithelium; cell nuclei lie at different levels giving the stratified impression; SECRETES & ABSORBS substances; ciliated version contains mucus-secreting goblet cells (line respiratory tract)
stratified squamous epithelium
most widespread of the stratified; thick and well suited for PROTECTIVE roles in body; free surface cells are squamous and the cells of deeper layers are cuboidal or columnar; found in areas subjected to WEAR AND TEAR; surface cells replaced by basal cells; skin, vagina, esophagus, and anal canal
Why are apical surface stratified epithelial cells less viable?
Because they are farther from the basement membrane, which diffuses nutrients from the deeper connective tissue
What special protein does the outer layer, or epidermis, of the skin contain?
Keratin, a tough protective protein
stratified cuboidal epithelium
quite rare in the body; mostly found in the ducts of some larger glands (sweat glands, mammary glands) and lumens; typically has 2 layers of cuboidal cells; PROTECTION
stratified columnar epithelium
has limited distribution in body; found in pharynx, the male urethra, lining some glandular ducts; occurs at transition areas or junctions btw two other types of epithelia; PROTECTION, SECRETION
What is a gland?
consists of one or more cells that make and secrete a particular product, called a secretion
What is a secretion
an aqueous (water-based) fluid that usually contains proteins, but there is variation (some cells release a lipid- or steroid-rich secretion
How are glands classified?
Where they secrete (endocrine; exocrine); and number of cells (unicellular or multicellular)
Endocrine glands
called ductless glands because they eventually lose their ducts; produce hormones (messenger chemicals) that they secrete by exocytosis directly into the extracellular space; structurally diverse
Exocrine glands
secrete their products into ducts that open onto body surfaces (skin) or into body cavities; unicellular glands this directly by exocytosis, multicellular glands do so via an epithelium-walled duct that transports the secretion to the epithelium surface