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
What are important examples of unicellular exocrine glands?
mucous cells and goblet cells
mucin
a complex glycoprotein that dissolves in water when secreted and forms mucus; is produced by unicellular exocrine glands
goblet cells
cuplike accumulation of mucin distends the top of the cell, making cells look like a goblet
multicellular exocrine glands
have two basic parts, an epithelium-derived duct and a secretory unit (acinus) consisting of secretory cells;
Why is supportive connective tissue important to exocrine glands?
supportive connective tissue surrounds the secretory unit, supplying it with blood vessels and nerve fibers, an forming a fibrous capsule that extends into the gland and divides it into lobes
simple gland
glands with an unbranched duct
compound gland
glands with a branched duct: tubular, alveolar, or tubuloalveolar
merocrine glands
secrete their products by exocytosis as they are produced; secretory cells are not altered in any way; pancreas, most sweat glands, salivary glands
holocrine glands
accumulate their products within them until they rupture; replaced by the division of underlying cells; sebaceous oil glands of the skin only true example
What are the four main classes of connective tissue, along with their respective subclasses?
connective tissue proper, cartilage, bone tissue, and blood
What are the subclasses of connective tissue proper?
Loose connective tissue (areolar, adipose, reticular) and dense connective tissue (regular, irregular, elastic)
What are the major functions of connective tissues?
binding and supporting, protecting, insulating, storing reserve fuel, and transporting substances within the body
What three characteristics are shared between connective tissues?
common origin (all arise from mesenchyme, an embryonic tissue); degrees of vascularity; extracellular matrix (largely nonliving structures)
What are the three main elements of connective tissue?
ground substance, fibers, and cells
What is ground substance?
the unstructured material that fills the space between cells and contains the fibers; composed of interstitial fluid, cell adhesion proteins, and proteoglycans
What are the three connective tissue fibers?
collagen fibers, elastic fibers, and reticular fibers
collagen fibers
made up of the fibrous protein collagen; are secreted into the extracellular space where they assemble into cross-linked fibrils (long, parallel); extremely tough and provide high tensile strength to the matrix
elastic fibers
long, thin, elastic fibers form branding networks in the extracellular matrix; contain rubberlike protein, elastin, that allows them to stretch and recoil like rubber bands; snap the connective tissue back to its norma length and shape
reticular fibers
short, fine, collagenous fibers are continuous with collagen fiber and they branch extensively, forming delicate networks (reticul) that surround small blood vessels and support the soft tissue of organs
What are the primary blast cell types and their associated connective tissue class?
- connective tissue proper: fibroblast; 2. cartilage: chondroblast; 3. bone: osteoblast; 4. bood: hematopoietic stem cell, though it is not located in the blood (tissue) and does not make the fluid matris (plasma)
What other cell types find their home in connective tissue?
fat cells (store nutrients), white blood cells (concerned with tissue response to injury), mast cells (detect foreign microorganisms and initiate the inflammatory response, macrophages (devour foreign materials, dispose of dead tissue cells, central actors in immune system)
What chemicals are contained within mast cell cytoplasm and help mediate inflammation?
heparin, histamine, proteses, and other enzymes
areolar connective tissue
supporting and binding other tissues, holding body fluids, defending against infection, storing nutrients; loosely arranged fibers that create an open space with a reservoir of water and salts for surrounding body tissues
fibroblasts
flat branching cells that appear spindle shaped in profile, present a formidable barrier to invading microorganisms;
most common type of fixed cell in connective tissue; produces fibers (collagenous, elastic, and reticular fibers) by secreting proteins into the extracellular matrix
adipose (fat) tissue
Specialized form of LOOSE connective tissue that develops when adipocytes store fat in droplets within their cytoplasm and enlarge; When numerous, closely packed and crowd other cell types, they form adipose tissue.
Provides reserve food fuel, insulates against heat loss, supports, cushions and protects organs; subcutaneous tissue, kidneys, eyeballs, abdomen, breasts
reticular connective tissue
very thin, highly branched collagenous fibers that offer a delicate support system in a variety of tissues, including lymphoid organs (lymph nodes, bone marrow, and spleen)
dense regular connective tissue
primarily parallel collagen fibers, a few elastic fibers, major cell type is fibroblast; attaches muscles to bones or to muscles, attaches bones to bones, and withstand great tensile stress when pulling force is applied in one direction; found in tendons, ligaments, and aponeuroses
dense irregular connective tissue
primarily irregularly arranged collagen fibers & some elastic fibers; fibroblast is the major cell type; withstands tension exerted in many direction, and provides structural strength; found in fibrous capsules of organs and of joins; dermis of the skin, and submucosa of the digestive tract
dense elastic connective tissue
contains a high proportion of elastic fibers; allows tissue to recoil after stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration; walls of large arteries, within certain ligaments associated with the vertebral column, within the walls of the bronchial tubes
cartilage
Rigid connective tissue providing support, frameworks, and attachments; protects underlying tissues; forms structural models for many developing bones
Abundant extracellular matrix, lacks nerve fibers and is avascular; receives nutrients by diffusion of the blood vessels from the surrounding perichondrium (the covering of connective tissue the cartilaginous structure is enclosed in)
chondroblasts
predominant cell type in growing cartilage with in small chambers called lacunae; produce new matrix until skeleton stops growing at end of adolescence
chondrocytes
mature cartilage cells typically found in small group within cavities called lacunae; account for only 1-10% of cartilage volume
hyaline cartilage, or gristle
most abundant type; contains large amount of fine collagenous fibers; matrix appears like white glass; supports and reinforces; important in the growth of most bones
serves as resilient cushion; resists compressive stress; forms most of the embryonic skeleton; covers ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx
elastic cartilage
dense network of elastic fibers; more flexible than hyaline; provides framework for external ears and parts of larynx
fibrocartilage
very tough tissue; contains many collagenous fibers; shock absorber for structures subjected to pressure (intervertebral discs; cushions bones in knees and pelvic girdle)
bone (osseous tissue)
most rigid connective tissue; hardness due largely to mineral salts (calcium phosphate; calcium carbonate); extracellular matrix contains abundant collagenous fibers, which reinforce mineral components
Internally SUPPORTS body structures; PROTECTS vital parts of cranial and thoracic cavities; is an attachment for muscles; contains red marrow, which forms blood cells, and stores and releases inorganic chemicals such as calcium & phosphorus
blood
red and white blood cells, as well as platelets (cell fragments) in a fluid matrix (plasma); transport respiratory gases, nutrients, wastes, and other substances; contained within blood vessels
Why is blood considered a connective tissue?
Because it develops from mesenchyme and consists of blood cells, surrounded by a nonliving fluid matrix called blood plasma
skeletal muscle
long, cylindrical, multinucleate cells; obvious striations; voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control
characteristics of muscle tissues
highly cellular, well-vascularized; responsible for most types of body movement; possess myofilaments
miyofilaments
elaborate networks of the actin and myosin filaments that bring about movement or contraction in all cell types
What are the 3 types of muscle tissue?
skeletal, cardiac; smooth
Which muscle tissue is voluntary muscle?
skeletal muscle - contraction that is under our control
Which muscle tissues are involuntary muscle?
cardiac and smooth - we do not consciously control them
What is the extracellular matrix?
non-living portion within tissues; varies in composition from tissue to tissue and supports the cell from within; transmits signals from outside cells into cells
List the general characteristics of epithelial tissues.
Lack blood vessels, readily divide, cells are tightly packed
Describe the classification of epithelium in terms of shape and number of cell layers.
Squamous, Cuboidal, Columnal; simple & stratified
apocrine glands
cellular product and portions of the free ends of glandular cells pinched off during secretion; mammory glands, ceruminous glands lining the external ear canal
Explain how exocrine glands are classified.
according to the ways these glands secrete their products
What is transitional epithelium?
specialized to change in response to increased tension; DISTENSIBILITY, PROTECTION; inner lining of urinary bladder and linings of ureters and part of urethra
What is glandular epithelium?
composed of cells that are specialized to produce and secrete substances into ducts or into body fluids; one or more of these cells constitute a gland; SECRETION; salivary glands, sweat glands, endocrine glands
macrophages
or histiocytes, originate as white blood cells and are almost as numerous as fibroblasts in some connective tissues; specialized to carry on phagocytosis; “wandering cells” that move about and function as scavenger and defensive cells that clear foreign particles from tissues
Mast cells
large and widely distributed in connective tissue; usually located near blood vessels; release HEPARIN, which prevents blood clotting, and HISTAMINE, which promotes some of the reactions associated with inflammation and allergies
Describe loose connective tissue.
AKA areolar tissue, forms delicate, thin membranes throughout the body; fibroblasts are the main cells of this tissue; binds skin to the underlying organs and fills spaces between muscles; lies beneath most layers of epithelium, where its many blood vessels nourish nearby epithelial cells
Describe dense connective tissue.
Consists of many closely packed, thick, collagenous fibers and a fine network of elastic fibers; has relatively few cells, most of which are fibroblasts; blood supply is poor, slowing tissue repair.
Explain why injured bone heals more rapidly than injured cartilage.
Each central canal contains a blood vessel, which places every bone cell near a nutrient supply. Bone cells have many cytoplasmic processes that extend outward and pass through the canaliculi, connecting with the membranes of nearby cells. As a result, materials can move rapidly between blood vessels and bone cells.
