A&P 4: Tissue - The Living Fabric Flashcards
Tissue
“woven”; groups of cells that are similar in structure and perform a common or related function
Histology
study of tissues
Fixed
before specimen can be viewed through a microscope, it must be preserved
Sections
slices thin enough to transmit light or electrons
Artifacts
preserved tissue under the microscope has been exposed to many procedures that alter its original condition and introduce these minor distortions
Epithelial tissue (epithelium)
sheet of cells that covers a body surface or lines a body cavity
Apical surface
all epithelia have this upper free surface exposed to the body exterior or the cavity of an internal organ
Basal surface
all epithelia have this lower attached surface
Microvilli
fingerlike extensions of the plasma membrane; tremendously increase the exposed surface area; often so dense that the cell apices have a fuzzy appearance (brush border)
Basal lamina
adjacent to the basal surface of an epithelium is this thin supporting sheet; noncellular, adhesive sheet consists largely of glycoproteins secreted by the epithelial cells plus some fine collagen fibers
Reticular lamina
just deep to the basal lamina is this layer of extracellular material containing a fine network of collagen protein fibers that belongs to the underlying connective tissue
Basement membrane
basal lamina + reticular lamina; reinforces the epithelial sheet, helps it resist stretching and tearing, and defines the epithelial boundary
Simple epithelia
consists of a single cell layer; typically found where absorption, secretion, and filtration occur; thin barrier is desirable
Stratified epithelia
composed of 2 or more cell layers stacked on top of each other; common in high-abrasion areas where protection is important, such as the skin surface and the lining of the mouth
Squamous cells
flattened and scalelike
Cuboidal cells
boxlike, approximately as tall as they are wide
Columnar cells
tall, column-shaped
Simple squamous epithelium
cells flattened laterally; sparse cytoplasm; resemble a tiled floor
Endothelium
provides a slick, friction-reducing lining in lymphatic vessels and in all hollow organs of the cardiovascular system (blood vessels/heart)
Mesothelium
epithelium found in serous membranes (lining ventral body cavity and covering its organs)
Simple cuboidal epithelium
consists of a single layer of cells as tall as they are wide; spherical nuclei stain darkly, causing the cell layer to look like a string of beads when viewed microscopically; important functions = secretion and absorption; forms the walls of the smallest ducts and glands and of many kidney tubules
Simple columnar epithelium
single layer of tall, closely packed cells, aligned like soldiers in a row; lines the digestive tract from the stomach through the rectum; mostly associated with absorption and secretion
Pseudostratified columnar epithelium
cells vary in height; all of its cells rest on the basement membrane, but only the tallest reach the free surface of the epithelium; tissue gives the false impression that several cell layers are present
Stratified squamous epithelium
most widespread of the stratified epithelia; several layers, thick, well-suited for its protective role in the body; free surface cells are squamous, deeper layers are cuboidal or columnar; found in areas subjected to wear and tear; surface cells constantly being rubbed away and replaced by division of its basal cells
Stratified cuboidal epithelium
quite rare in the body, mostly found in the ducts of some of the larger glands (sweat/mammary glands); typically has 2 layers of cuboidal cells
Stratified columnar epithelium
limited distribution in the body; small amounts in the pharynx, the male urethra, and lining some glandular ducts; occurs at transition areas/junctions between 2 other types of epithelia; only apical layer columnar
Transitional epithelium
forms the lining of hollow urinary organs, which stretch as they fill with urine; cells of its basal layer are cuboidal or columnar; apical cells vary in appearance, depending on the degree of distension (stretching) of the organ
Gland
consists of 1 or more cells that make/secrete a particular product
Secretion
product of glands; aqueous fluid usually containing proteins (some release lipid or steroid rich secretions)
Endocrine glands
ductless glands; produce hormones (secreted by exocytosis) directly into the extracellular space; from there, the hormones enter the blood or lymph and travel to specific target organs
Hormones
messenger chemicals secreted by endocrine glands via exocytosis; prompts their target organs to respond in some characteristic way
Exocrine glands
glands that secrete their products onto body surfaces (skin) or into body cavities; unicellular glands to so by exocytosis; multicellular glands do so via an epithelium-walled duct that transports the secretion to the epithelial surface
Unicellular exocrine glands
mucous cells & goblet cells; sprinkled in the epithelial linings of the intestinal and respiratory tracts amid columnar cells with other functions
Mucin
all unicellular exocrine glands in humans produce this complex glycoprotein that dissolves in water when secreted; once dissolved, forms a slimy coating that protects and lubricates surfaces
Goblet cells
cuplike accumulation of mucin distends the top of the cell, making the cells look like a glass with a stem; this distortion does not occur in mucous cells
Multicellular exocrine glands
structurally complex; 2 basic parts: (1) an epithelium-derived duct & (2) a secretory unit (acinus) consisting of secretory cells
Simple glands
glands with an unbranched duct
Compound glands
glands with a branched duct
Tubular
glands are categorized as this if the secretory cells form tubes
Alveolar
glands are categorized as this if the secretory cells form small, flask-like sacs
Tubuloalveolar
glands are categorized as this if the secretory cells form tubes and small, flask-like sacs
Acinar
“berrylike”; used interchangeably with alveolar
Merocrine glands
glands secreting products by exoctyosis as they are produced; most glands are this, including pancreas, most sweat glands, and salivary glands
Holocrine glands
secretory cells of these glands accumulate their products within them until they rupture; only true example = sebaceous (oil) glands
Apocrine glands
glands which accumulate their product but only just beneath the free surface; apex pinches off, releasing the secretory granules and a small amount of cytoplasm; best human example = release of lipid droplets by lactating mammary glands (most histologists classify mammary glands as merocrine glands)
Connective tissue
most abundant and widely distributed of the primary tissues; amount in particular organs varies; 4 classes - ___ tissue proper, cartilage, bone, and blood
Extracellular matrix
connective tissues are largely nonliving, which separates, often widely, the living cells of the tissue; because of this, connective tissues can bear weight, withstand great tension, and endure abuses (trauma, abrasion)
Ground substance
unstructured material that fills the space between cells and contains the fibers; composed of interstitial fluid, cell adhesion proteins, and proteolycans
Collagen fibers
constructed primarily of the fibrous protein that gives it its name; fibrils cross-link, so they are extremely tough and provide high tensile strength
Elastic fibers
long, thin fibers that form branching networks in the extracellular matrix; contain the rubberlike protein that allows them to stretch and recoil like rubber bands
Reticular fibers
short, fine, collagenous fibers with slightly different chemistry and form; continuous with collagen fibers & branch extensively, forming delicate NETWORKS that surround small blood vessels and support the soft tissue of organs
Fibroblast
primary blast cell type of connective tissue proper
Chondroblast
primary blast cell of cartilage
Osteoblast
primary blast cell of bone
Hematopoietic stem cell
undifferentiated blast cell that produces blood cells
Fat cells
stores nutrients
White blood cells
neutrophils, eosinophils, lymphocytes & other cell types that are concerned with tissue response to injury
Mast cells
typically cluster along blood vessels; oval cells that detect foreign microorganisms and initiate inflammatory responses against them; in the cytoplasm of these cells are secretory granules containing chemicals that mediate inflammation, especially in severe allergies (heparin, histamine, proteases, various enzymes = chemicals)
Macrophages
large, irregularly shaped cells that avidly phagocytize a broad variety of foreign materials, ranging from foreign molecules to entire bacteria to dust particles; “big eaters”
Mesenchyme
common embryonic tissue from which mature connective tissues arise; has a fluid ground substance containing fine sparse fibers and star-shaped ___-al cells
Connective tissue proper
2 subclasses - loose connective tissues (areolar, adipose, and reticular) and dense connective tissues (dense regular, dense irregular, and elastic)
Loose connective tissues
areolar, adipose, reticular
Dense connective tissues
regular, irregular, and elastic
Areolar connective tissue
functions include: (1) supporting and binding other tissues (job of fibers), (2) holding body fluids (ground substance’s role), (3) defending against infection (via the activity of WBCs and macrophages, & (4) storing nutrients as fat (in fat cells)
Edema
condition in which a body region is inflamed, the areolar tissue in the area soaks up excess fluids like a sponge, and the affected area swells and becomes puffy
Adipose tissue
similar to areolar tissue in structure/function but its nutrient-storing ability is much greater
Adipocytes
adipose/fat cells; account for 90% of adipose tissue’s mass
Brown fat (brown adipose tissue)
contains abundant mitochondria, which use the lipid fuels to heat the bloodstream to warm the body (rather than to produce ATP molecules); richly vascular, occurs mainly on the back of babies
Reticular connective tissue
resembles areolar connective tissue, but the only fibers in its matrix are reticular fibers, which form a delicate network along which fibroblasts (reticular cells) are scattered
Reticular cells
fibroblasts scattered throughout reticular connective tissue
Stroma
“bed/mattress”; labyrinth-like internal framework of reticular tissue that can support many free blood cells (mostly lymphocytes) in lymph nodes, the spleen, and bone marrow
Fibrous connective tissues
AKA dense connective tissues because all 3 types have fibers as their prominent element
Dense regular connective tissue
contains closely packed bundles of collagen fibers running in the same direction, parallel to the direction of the pull; arrangement results in white, flexible structures with great resistance to tension (where the tension is exerted in a single direction)
Dense irregular connective tissue
has the same structural elements as the other variety, but the bundles of collagen fibers are much thicker and they are arranged irregularly (run in more than one plane); forms sheets in body areas where tension is exerted from many different directions; found in the skin (dermis), forms fibrous join capsules and the fibrous coverings that surround some organs (kidneys, bones, cartilages, muscles, and nerves)
Elastic connective tissue
dense regular connective tissue of ligaments and many of the larger arteries
Cartilage
stands up to both tension and compression; has qualities intermediate between dense connective tissue and bone; tough but flexible, providing a resilient rigidity to the structures it supports; lacks nerve fibers and is avascular
Chondrocytes
mature cartilage cells; typically found in small groups within cavities called lacunae
Hyaline cartilage
gristle; most abundant cartilage in the body; contains a large number of collage fibers but they are not apparent and the matrix appears glassy blue-white when viewed by the unaided eye; chondrocytes account for 1-10% of the cartilage volume; provides springy pads that absorb compression at joints, covers the long bones of articular cartilage; supports the tip of the nose, connects the ribs to the sternum, and supports most of the respiratory system passages; most of the embryonic skeleton consists of this
Elastic cartilage
nearly identical to hyaline cartilage but has many more elastic fibers; found where strength and exceptional stretchability are needed; forms the “skeletons” of the external ear (pinna) & the epiglottis (flap that covers the opening to the respiratory passageway when we swallow)
Fibrocartilage
intermediate between hyaline cartilage and dense regular connective tissues; row of chondrocytes alternate with rows of thick collagen fibers; compressible and resists tension well; found where strong support and the ability to withstand heavy pressure are required (intervertebral disks and the spongy cartilages of the knee = menisci)
Bone (osseous tissue)
rocklike hardness; exceptional ability to support/protect body structures; provide cavities for storing fat and synthesizing blood cells; its matrix is similar to that of cartilage but harder and more rigid because it has an added matrix element (inorganic calcium salts)
Osteocytes
mature bone cells; reside in the lacunae; well supplied by invading blood vessels
Blood
fluid within blood vessels; most atypical connective tissue; does not connect things or give mechanical support; develops from mesenchyme and consists of _____ cells surrounded by a nonliving fluid matrix (plasma)
Muscle tissues
highly cellular, well-vascularized tissues responsible for most types of body movement
Myofilaments
muscle cells possess these elaborate versions of actin and myosin filaments that bring about movement or contraction in all cell types
Skeletal muscle
tissue packaged by connective tissue sheets into organs called this that are attached to the bones of the skeleton
Muscle fibers
skeletal muscle cells; long, cylindrical cells that contain many peripherally located nuclei; obvious banded (striated) appearance reflects the precise alignment of their myofilaments
Intercalated discs
cardiac muscle; branching cells that fit tightly at unique junctions called this
Smooth muscle
cells have no visible striations; spindle-shaped, contain one, centrally-located nucleus; found mainly in the walls of hollow organs other than the heart (digestive/urinary tract organs, uterus, blood vessels); squeezes substances through these organs by alternately contracting and relaxing
Voluntary muscle
skeletal muscle referred to as this because it is under our conscious control
Involuntary muscle
smooth and cardiac muscle referred to as this because we do not consciously control them
Neurons
highly specialized nerve cells that generate and conduct nerve impulses; typically branching cells with cytoplasmic extensions/processes that enable them to respond to stimuli (dendrites) and transmit electrical impulses over substantial distances within the body (axons)
Cutaneous membrane
skin; consists of keratinized stratified squamous epithelium (epidermis) firmly attached to a thick layer of connective tissue (dermis); exposed to the air and is a dry membrane
Mucous membranes (mucosae)
line all body cavities that open to the outside of the body (hollow organs of the digestive, respiratory, and urogenital tracts)
Lamina propia
loose connective tissue underneath the epithelial sheet
Serous membranes (serosae)
moist membranes found in closed ventral body cavities
Pleurae
line the thoracic wall and cover the lungs
Pericardium
encloses the heart
Peritoneum
encloses the abdominopelvic viscera
Regeneration
replaces destroyed tissue with the same kind of tissue
Fibrosis
fibrous connective tissue proliferates to form scar tissue
Scar tissue
in fibrosis, fibrous connective tissue proliferates to form this
Organization
1st phase of tissue repair; blood clot is replaced by granulation tissue
Granulation tissue
a delicate pink tissue composed of several elements (capillaries, proliferating fibroblasts, collagen fibers…)
Primary germ layers
one of the 1st events of embryonic development is the formation of these, which lie one atop the next like a 3-layered cellular pancake
Ectoderm
top of the primary germ layers
Mesoderm
middle of the 3 primary germ layers
Endoderm
deepest of the primary germ layers
Neoplasm
abnormal mass of proliferating cells
Benign
kindly neoplasms
Malignant
bad neoplasms
Metastasis
capability for traveling to other parts of the body
Oncogenes
cancer-causing genes
Proto-oncogenes
benign forms of oncogenes in normal cells; code for proteins that are essential for cell division, growth, and cellular adhesion
Tumor suppresor genes
anti-oncogenes; suppress cancer by inactivating carcinogens, aiding DNA repair, or enhancing the immune system’s counterattack
Biopsy
removing a tissue sample surgically and examining it microscopically for malignant cells
Stage
cancer assigned this (1-4) according to the probability of a cure; 1 has the best probability; 4 the worst
