Histology Flashcards
Histology
the science and study of tissues
tissue
a group of cells, usually with a common embryonic origin, that function together to carry out
specialized activities
pathologist
a physician who examines cells and tissues to help other physicians make accurate
diagnoses
4 types of tissues
epithelial
connective
muscular
nervous
epithelial tissue
covers body surfaces; lines body cavities, hollow organs, and ducts (tubes);
and forms glands
connective tissue
protects and supports the body and its organs, binds organs together, stores
energy reserves as fat, and provides immunity
muscular tissue
generates the physical force needed to make body structures move
nervous tissue
detects changes inside and outside the body and initiates and transmits nerve
impulses (action potentials) that coordinate body activities to help maintain homeostasis
2 types of epithelial tissue
covering and lining epithelium
glandular epithelium
covering and lining epithelium
outer covering of the skin and the outer covering of some
internal organs; lines body cavities, blood vessels, ducts, interiors of the respiratory, digestive,
urinary, and reproductive systems
glandular epithelium
makes up secreting portions of glands such as sweat glands
general features of epithelial tissue
Consists of closely packed cells with little extracellular material between them; arranged in
continuous sheets
Avascular
Epithelial tissue has a nerve supply
Has a high capacity for renewal by cell division (because it is subject to a certain amount of wear
and tear)
avascular
lacks blood vessels; blood vessels that supply epithelial tissue are located in adjacent
connective tissues
components of epithelial tissue
an apical (free) space surface
lateral surface
a basal surface
basement membrane
an apical (free) surface
exposed to a body cavity, lining of an internal organ, or the exterior of the body (most superficial layer)
lateral surface
face adjacent cells on either side
basal surface
attached to a basement membrane (deepest layer)
basement membrane
a thin extracellular structure composed mostly of protein fibers; located
between the epithelial tissue and the underlying connective tissue layer; helps bind and support
the epithelial tissue
classification of epithelial tissue
classified according to the arrangement of cells into layers and the
shape of the cells
arrangement of cells in layer
simple epithelium
pseudostratified epithelium
stratified epithelium
secretion
the production and release of substances such as mucus, sweat or enzymes
absorption
the intake of fluids or other substances such as digested food from
the intestinal tract
pseudostratified epithelium
actually simple epithelium, but appears to have multiple
layers of cells because the cell nuclei lie at different levels and not all cells reach the
apical surface
stratified epithelium
consists of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear
squamous cells
thin, allowing for the rapid passage of substances through them
cuboidal cells
as tall as they are wide, shaped like cubes or hexagons; have microvilli at their apical surface and function in either secretion or absorption
columnar cells
much taller than they are wide, like columns, protect underlying tissues.
Their apical surfaces may have cilia or microvilli; often specialized for secretion and
absorption
transitional cells
change shape, from flat to cuboidal and back, as organs such as the urinary bladder stretch to a larger size, then collapse to a smaller size
arrangement of simple epithelium
simple squamous epithelium
simple cuboidal epithelium
simple columnar epithelium ( noncilated and ciliated)
pseudostratified columnar epithelium ( noncilated and ciliated)
stratified epithelium
stratified squamous epithelium ( keratinzed and nonkeratinzed)
stratified cuboidal epithelium
stratified columnar epithelium
transitional epithelium
Simple squamous epithelium
a single layer of flat cells that resembles a tiled floor when
viewed from apical surface; centrally located nucleus that is flattened and oval or spherical in shape
location of simple squamous epithelium
lines Lines heart, blood vessels, and lymphatic vessels (endothelium)
Lines air sacs of lungs, glomerular capsule of kidneys, and inner surface of the
tympanic membrane
Forms the epithelial layer of serous membranes such as peritoneum, pleura, or
pericardium (mesothelium)
function of simple squamous epithelium
filtration, diffusion, osmosis, and secretion in serous membranes
simple cuboidal epithelium
single layer of cube-shaped cells; round, centrally located nucleus
location of simple cuboidal epithelium
Lines kidney tubules and smaller ducts of many glands
Makes up the secreting portion of some glands such as the thyroid gland
Covers surface of ovary
Lines anterior surface of capsule of the lens of the eye
Forms the pigmented epithelium at the posterior surface of the eye
function of simple cuboidal epithelium
secretion and absorption
noncilated simple columnar epithelium
a single layer of nonciliated column-like cells with
nuclei near bases of cells; contains cells with microvilli and goblet cells
microvilli
microscopic fingerlike projections that increase the surface area of the
plasma membrane to increase the rate of absorption
goblet cells
modified columnar cells that secrete mucus, a slightly sticky fluid, at their apical surfaces
location of noncilated simple columnar epithelium
lines most of the gastrointestinal tract (from stomach to anus), ducts of many glands, and gallbladder
function of noncilated simple columnar epithelium
secretion and absorption
Ciliated simple columnar epithelium
a single layer of ciliated column-like cells with nuclei
near bases; contains goblet cells in some locations
location of ciliated simple columnar epithelium
lines a few portions of upper respiratory tract, uterine (fallopian) tubes, uterus,
some paranasal sinuses, and central canal of spinal cord
function of ciliated simple columnar epithelium
mucus secreted by goblet cells forms a film over respiratory surface that traps
inhaled foreign particles; cilia wave in unison and move mucus and any trapped foreign particles toward throat where it can be coughed up and swallowed or spit out.
Pseudostratified columnar epithelium
not a true stratified tissue; nuclei of cells are at different
levels; all cells are attached to basement membrane, but not all reach the apical surface
location of pseudostratified columnar epithelium
Lines the airways of most of upper respiratory tract and larger ducts of many
glands, epididymis, and part of male urethra
function of pseudostratified columnar epithelium
ciliated variety secretes mucus that traps foreign particles, and cilia sweep
away mucus for elimination from body; nonciliated variety functions in absorption and
protection
Stratified squamous epithelium
2+ layers of cells; cells in apical layer and several layers deep to it are squamous; as new cells grow at the basal layer, the deepest layers are pushed upward toward the surface
Keratinized stratified squamous epithelium
develops a tough layer of keratin in apical layer and
several layers deep to it
Nonkeratinized stratified squamous epithelium
does not contain keratin in apical layer and several layers deep to it and remains moist
location of Nonkeratinized stratified squamous epithelium
keratinized variety forms superficial layer of skin; nonkeratinized variety lines wet surfaces (lining of mouth, esophagus, part of epiglottis, part of pharynx, and vagina), covers tongue
function of Nonkeratinized stratified squamous epithelium
protection; provides first line of defense against microbes
stratified cuboidal epithelium
two or more layers of cells; cells in the apical layer are cubeshaped; fairly rare type
location of stratified cuboidal epithelium
ducts of adult sweat glands and esophageal glands and part of male urethra
function of stratified cuboidal epithelium
Protection and limited secretion and absorption
stratified columnar epithelium
basal layers usually consist of shortened, irregularly shaped
cells; only apical layer has columnar cells; uncommon.
location of stratified columnar epithelium
Lines part of urethra, large excretory ducts of some glands such as esophageal
glands, small areas in anal mucous membrane, and part of conjunctiva of eye
function of stratified columnar epithelium
Protection and secretion
transitional epithelium
variable in appearance; in relaxed or unstretched state, looks similar to
stratified cuboidal epithelium, except apical layer cells tend to be large and rounded; as tissue is
stretched, cells become flatter
location of transitional epithelium
lines urinary bladder and portions of ureters and urethra
function of transitional epithelium
allows urinary organs to stretch and maintain protective lining while holding
variable amounts of fluid without rupturing
glandular epithelium
secretion accomplished by glandular cells that lie in clusters deep to the
covering and lining epithelium
gland
may consist of one cell or a group of highly specialized epithelial cells that secrete
substances into ducts onto a surface or into the blood
glands are classified as endocrine and exocrine
secretions (hormones) enter the interstitial fluid and then diffuse into the
bloodstream without flowing through a duct
glands are classified exocrine
secrete their products into ducts that empty at the surface of covering and
lining epithelium such as the skin surface or the lumen (interior space) of a hollow organ
connective tissue
one of the most abundant and widely distributed tissues in the body
functions of connective tissue
Binds together, supports, and strengthens other body tissues
Protects and insulates internal organs
Compartmentalizes structures such as skeletal muscles
Is the major transport system within the body (blood)
Is the major site of stored energy reserves (adipose)
Is the main site of immune responses
2 basic elements of connective tissue
cells
extracellular matrix
extracellular matrix
the material between its widely spaced cells; consists of protein
fibers and ground substance (the material between the cells and the fibers
general features of connective tissue
Do not usually occur on body surfaces
Usually are highly vascular
Except for cartilage, connective tissue is supplied with nerves
Connective tissue cells
Fibroblasts
large flat cells with branching processes; usually the most numerous; migrate through the connective tissue secreting the fibers and ground substance of the
extracellular matrix
macrophages
develop from monocytes (a type of white blood cells); irregular shape with short branching projections; capable of engulfing bacteria and cellular debris by
phagocytosis
plasma cells
small cells that develop from B lymphocytes (a type of white blood cells); secrete antibodies
mast cells
abundant alongside the blood vessels that supply connective tissue; produce histamine (chemical that dilates small blood vessels as part of the inflammatory response); can kill bacteria
adipocytes
fat cells; adipose cells; store triglycerides; found below the skin and around
organs such as the heart and kidneys
connective tissue extracellular matrix
Each type of connective tissue has unique properties based on the specific extracellular
materials between the cells
Fluid, gel, or solid ground substance plus protein fibers
ground substance
the component of connective tissue between the cells and fibers
supports and binds cells together
provides a medium through which substances are exchanged between the blood and cells
plays an active role in how tissues develop, migrate, proliferate, change shape, and carry out their metabolic functions
contains water and an assortment of large organic molecules
fibers
Strengthen and support connective tissues
3 types in the extracellular matrix
collagen fibers
elastic fibers
reticular fibers
collagen fibers
very strong and resist pulling forces; not stiff, promotes
tissue flexibility; often occur in parallel bundles that offer strength
Most types of connective tissue; bone, cartilage, tendons, and
ligaments
elastic fibers
smaller in diameter than collagen fibers, branch and joint together to form a network within a tissue; strong but can be stretched up
to 1 ½ times their relaxed length without breaking
Plentiful in skin, blood vessel walls, and lung tissue
reticular fibers
much thinner than collagen fibers; provide support and
strength; supporting framework of many soft organs
provide support in the walls of blood vessels and form branching
networks around fat cells, nerve fibers, and skeletal and smooth
muscle cells
loose connective tissue
fibers are loosely arranged areolar connective tissue adipose tissue reticular connective tissue dense connective tissue dense irregular connective tissue elastic connective tissue cartilage liquid connective tissue
areolar connective tissue
one of the most widely distributed connective tissues; consists of
fibers arranged randomly and several kinds of cells embedded in a semifluid
ground substance
location of areolar connective tissue
in and around nearly every body structure (“packing material of the
body”); subcutaneous layer deep to skin, superficial region of dermis of skin,
connective tissue layer of mucous membranes, around blood vessels, nerves, and
body organs
function of areolar connective tissue
strength, elasticity, and support
adipose tissue
cells called adipocytes; specialized for storage of triglycerides; new
blood vessels form with weight gain
location of adipose tissue
Wherever areolar connective tissue is located; subcutaneous layer deep to skin, around heart and kidneys, yellow bone marrow, and padding around joints and behind eyeball in eye socket
function of adipose tissue
reduces heat loss through skin; serves as an energy reserve; supports
and protects organs
reticular connective tissue
fine interlacing network of reticular fibers and reticular cells
location of reticular connective tissue
stroma (supporting framework) of liver, spleen, lymph nodes; red bone marrow; part of the basement membrane; around blood vessels and muscles
function of reticular connective tissue
forms stroma of organs; binds together smooth muscle tissue cells;
filters and removes worn-out blood cells in spleen and microbes in lymph nodes
dense regular connective tissue
contains more numerous, thicker, and denser fibers, but fewer cells than loose connective tissue
description of dense regular connective tissue
extracellular matrix looks shiny white; consists mainly of collagen fibers regularly arranged in bundles
location of dense regular connective tissue
forms tendons, most ligaments, and aponeuroses (sheet-like tendons
that attach muscle to muscle or muscle to bone)
function dense regular connective tissue
provides strong attachment between various structures; tissue structure
resists pulling along long axis of fibers
dense irregular connective tissue
consists predominantly of collagen fibers randomly arranged and a
few fibroblasts
location of dense irregular connective tissue
often occurs in sheets (fascia), deeper region of dermis of skin, periosteum of bone, perichondrium of cartilage, joint capsules, various organs,
pericardium of the heart; also in heart valves
function of dense irregular connective tissue
provides tensile strength in many directions
elastic connective tissue
consists predominantly of elastic fibers; fibroblasts are present in spaces between fibers; unstained tissue is yellowish
location of elastic connective tissue
lung tissue, walls of elastic arteries, trachea, bronchial tubes, true vocal
cords, suspensory ligaments of penis, some ligaments between vertebrae
function of elastic connective tissue
allows stretching of various organs; is strong and can recoil to original shape after being stretched
cartilage
Consists of a dense network of collagen fibers or elastic fibers firmly embedded in chondroitin sulfate (a rubbery component of the ground substance)
Can endure considerably more stress than loose and dense connective tissues
chondrocytes
perichondrium
no blood vessels or nerves except in the perichondrium
antiangiogenesis factor
heals poorly
chondrocytes
cells of mature cartilage
perichondrium
a membrane of dense irregular connective tissue that surrounds the surface of most cartilage
antiangiogenesis factor
secreted by cartilage to prevent blood vessel growth
3 types of cartilage
Hyaline
Fibrocartilage
Elastic cartilage
hyaline cartilage
contains a resilient gel as ground substance and appears in the body as a bluish-white, shiny substance; most abundant type of cartilage in the body
location of hyaline cartilage
ends of long bones, anterior ends of ribs, nose, parts of larynx, trachea, bronchi, bronchial tubes, and embryonic and fetal skeleton
function of hyaline cartilage
provides smooth surfaces for movement at joints, as well as
flexibility and support; weakest type of cartilage (can be fractured)
fibrocartilage
consists of chondrocytes scattered among clearly visible thick bundles of collagen fibers within extracellular matrix; lacks perichondrium
location of fibrocartilage
pubic symphysis, intervertebral discs, menisci of knee, and portions of tendons that insert into cartilage
function of fibrocartilage
Support and joining structures together. Strength and rigidity
make it the strongest type of cartilage
elastic cartilage
consists of chondrocytes located in a threadlike network of elastic fibers within the extracellular matrix; perichondrium present
location of elastic cartilage
lid on top of larynx (epiglottis), part of external ear, and
auditory (Eustachian) tubes
function of elastic cartilage
provides strength and elasticity; maintains shape of certain structures
bone tissue
each bone is an organ composed of different tissues: bone tissue, cartilage,
dense connective tissue, epithelium, blood-forming tissue, adipose tissue, and nerve tissue
liquid connective tissue
( blood and lymph tissue)
blood tissue
connective tissue with a liquid extracellular matrix (blood plasma) and red blood cells, white blood cells, platelets, and a variety of other substances
lymph tissue
a fluid that flows in lymphatic vessels; a connective tissue that consists of several types of cells in a clear extracellular matrix similar to blood plasma
membranes
flat sheets of pliable tissue that cover or line a part of the body
epithelial membrane
combination of an epithelial layer and an underlying connective tissue layer
principle epithelial membranes
mucous membranes, serous membranes, cutaneous membrane (skin), and synovial membranes (except these do not contain epithelium)
mucous membrane (mucosa)
lines a body cavity that opens directly to the exterior
Lines the entire digestive, respiratory, and reproductive systems and much of the urinary
system
Secretes mucus which prevents the cavities from drying out
Traps particles in the respiratory passageways, lubricates and absorbs food as it moves through the gastrointestinal tract, and secretes digestive enzymes
serous membrane
lines a body cavity that does not open directly to the exterior, and covers the
organs that lie within the cavity
Consists of 2 parts: parietal layer (attached to cavity wall) and visceral layer (covers and
attaches to the organs inside the cavities)
secretes serous fluid
serous fluid
watery lubricating fluid that allows organs to glide easily over one another or to slide against the walls of cavities
synovial membrane
lines the cavities of some joints
composed of areolar connective tissue and adipose tissue with collagen
do not have an epithelial layer
Contain cells which secrete synovial fluid
synovial fluid
lubricates the ends of bones as they move at joints, nourishes the cartilage covering the bones, and removes microbes and debris from the joint cavity
musuclar tissue
Consists of elongated cells called muscle fibers that are highly specialized to generate force
Produces motion, maintains, posture, generates heat, and offers protection
classified into skeletal, cardiac, smooth
skeletal muscular tissue
usually attached to the bones of the skeleton
cardiac muscular tissue
the bulk of the wall of the heart
smooth muscular tissue
located in the walls of hollow internal structures (blood vessels, airways, digestive and urinary systems
nervous tissue
consists of neurons and neuroglia
neurons
nerve cells; sensitive to various stimuli which are converted into nerve
impulses and conducted to other neurons, muscle fibers, or to glands
neuroglia
do not generate or conduct nerve impulses, but serve protective and
supportive functions
