Histo chap 4 Flashcards
four basic tissue types:
epithelial, connective, muscular, and nervous tissues
composed of the cells responsible for the organ’s specialized functions
parenchyma
cells of which have a supporting role in the organ
stroma
Except in the brain and spinal cord, the stroma is
always ______________________
connective tissue
are composed of closely aggregated
polyhedral cells adhering strongly to one another and to a thin layer of ECM, forming cellular sheets that line the cavities of organs and cover the body surface
Epithelial tissues
The principal functions of epithelial tissues include the following:
- Covering, lining, and protecting surfaces (eg, epidermis)
- Absorption (eg, the intestinal lining)
- Secretion (eg, parenchymal cells of glands)
Specific cells of certain epithelia may be contractile
myoepithelial cells
taste buds or the olfactory epithelium
specialized sensory cells
CELLS:
Aggregated polyhedral cells
ECM:
Small amount
FUNCTION:
Lining of surface or body cavities; glandular secretion
Epithelial
CELLS:
Several types of fixed and wandering cells
ECM:
Abundant amount
FUNCTION:
Support and protection of tissues/organs
Connective
CELLS:
Elongated contractile cells
ECM:
Moderate amount
FUNCTION:
Strong contraction; body movements
Muscle
CELLS:
Elongated cells with extremely fine processes
ECM:
Very small amount
FUNCTION:
Transmission of nerve impulses
Nervous
generally have elongated
nuclei,
Columnar cells
have flattened nuclei
squamous cells
have more spherical nuclei
cuboidal or
pyramidal cells
The connective tissue that underlies
the epithelia lining the organs of the digestive, respiratory, and urinary systems
lamina propria
area of contact between the two tissues may be increased by small evaginations
papillae
The region of the cell contacting the ECM and connective tissue is called
basal pole
the opposite end, usually facing a space
apical pole
The basal surface of all epithelia rests on a thin extracellular, felt-like sheet of macromolecules referred to as
basement
membrane
With the transmission electron microscope (TEM) two
parts of the basement membrane may be resolved. Nearest the epithelial cells is the _____________________________, a thin, electron-dense,
sheetlike layer of fine fibrils, and beneath this layer is a more diffuse and fibrous ________________________
basal lamina, reticular lamina
large glycoproteins that attach to
transmembrane integrin proteins in the basal cell membrane and project through the mesh formed by the type IV collagen
Laminin:
Respectively a short, rodlike
protein and a proteoglycan, both of these cross-link laminins to the type IV collagen network, helping to provide the basal lamina’s three-dimensional structure, to bind the epithelium to that structure, and to determine its porosity and the size of molecules able to filter through it.
Nidogen and perlecan:
form a seal between adjacent cells.
Tight or occluding junctions
bind epithelial
cells to the underlying basal lamina.
Hemidesmosomes
Seals adjacent cells to
one another, controlling
passage of molecules
between them;
separates apical and
basolateral membrane
domains
Tight Junction
(Zonula Occludens)
Provides points linking
the cytoskeletons
of adjacent cells;
strengthens and
stabilizes nearby tight
junctions
Adherens Junction
(Zonula Adherens)
Provides points of
strong intermediate
filament coupling
between adjacent cells,
strengthening the tissue
Desmosome
(Macula Adherens)
Anchors cytoskeleton
to the basal lamina
Hemidesmosome
Allows direct
transfer of small
molecules and
ions from one cell
to another
Gap Junction
(Nexus)
are sites of strong
cell adhesion
Adherent or anchoring junctions
are channels for communication between adjacent cells.
Gap junctions
The seal between the two cell membranes is due
to tight interactions between the transmembrane proteins
claudin and occludin
Tight junctions are clearly seen after _______________________
cryofracture of epithelia
encircles the epithelial cell, usually immediately below the tight junction
adherens junction or
zonula adherens
Cell adhesion is mediated by _________________, transmembrane glycoproteins of each cell that bind each other in the presence of Ca2
cadherins
These adhesive structures resemble a
half-desmosome ultrastructurally, but unlike desmosomes the clustered transmembrane proteins that indirectly link to cytokeratin intermediate filaments are integrins rather than cadherins
hemidesmosomes
in epithelia specialized for absorption the apical cell
surfaces are often filled with an array of projecting
microvilli
is a disorder of the small intestine in which one of the
first pathologic changes is loss of the microvilli brush border of the absorptive cells
Celiac disease,
a much less common type of apical process, best seen on the absorptive epithelial cells lining the male
reproductive system
Stereocilia
specialized stereocilia with a motion-detecting function are important components of inner ____ sensory cells.
ear
long, highly motile apical structures, larger than microvilli, and containing internal arrays of microtubules not
microfilaments
Cilia
9 + 2 assembly of microtubules is called
axoneme
is found mainly in the epidermis of skin, where it helps prevent dehydration from the tissue
Stratified squamous keratinized epithelium
EXAMPLES OF DISTRIBUTION:
Lining of vessels (endothelium);
Serous lining of cavities:
pericardium, pleura, peritoneum
(mesothelium)
MAIN FUNCTION:
Facilitates the movement of
the viscera (mesothelium),
active transport by pinocytosis
(mesothelium and endothelium),
secretion of biologically active
molecules (mesothelium)
SIMPLE SQUAMOUS
EXAMPLES OF DISTRIBUTION:
Covering the ovary, thyroid
MAIN FUNCTION:
Covering, secretion
SIMPLE CUBOIDAL
EXAMPLES OF DISTRIBUTION:
Lining of intestine, gallbladder
MAIN FUNCTION:
Protection, lubrication,
absorption, secretion
SIMPLE COLUMNAR
EXAMPLES OF DISTRIBUTION:
Epidermis
MAIN FUNCTION:
Protection; prevents water loss
STRATIFIED SQUAMOUS KERATINIZED
EXAMPLES OF DISTRIBUTION:
Mouth, esophagus, larynx,
vagina, anal canal
MAIN FUNCTION:
Protection, secretion; prevents
water loss
STRATIFIED SQUAMOUS NON-KERATINIZED
EXAMPLES OF DISTRIBUTION:
Sweat glands, developing
ovarian follicles
MAIN FUNCTION:
Protection, secretion
STRATIFIED CUBOIDAL
EXAMPLES OF DISTRIBUTION:
Bladder, ureters, renal calyces
MAIN FUNCTION:
Protection, distensibility
STRATIFIED TRANSITIONAL
EXAMPLES OF DISTRIBUTION:
Conjunctivas
MAIN FUNCTION:
Protection
STRATIFIED COLUMNAR
EXAMPLES OF DISTRIBUTION:
Conjunctivas
MAIN FUNCTION:
Protection, secretion;
cilia-mediated transport of
particles trapped in mucus out of
the air passages
PSEUDOSTRATIFIED COLUMNAR
Secretory cells may synthesize, store, and release _______________
proteins, lipids, or complexes of carbohydrates and proteins
remain connected with the surface epithelium, the connection forming the tubular ducts lined with epithelium that deliver the secreted material where it is used
Exocrine glands
lose the connection to their original epithelium and therefore lack ducts
Endocrine glands
Glands can be ________ (ducts not branched) or _________ (ducts with two or more branches).
simple, compound
Secretory portions can be ______ (either short or long and coiled) or ______ (rounded and saclike); either type
of secretory unit may be branched, even if the duct is not branched
tubular, acinar
glands can have branching ducts and can have multiple tubular, acinar, or tubuloacinar secretory portions.
Compound
the most common method of protein or glycoprotein secretion and involves typical exocytosis from membrane-bound vesicles or secretory
granules.
Merocrine secretion
cells accumulate product
continuously as they enlarge and undergo terminal differentiation, culminating in complete cell disruption that releases the product and cell debris into the gland’s lumen. This is best seen in the sebaceous glands producing lipid rich material in skin
Holocrine secretion
Here product accumulates at the
cells’ apical ends, portions of which are then pinched off to release the product surrounded by a small amount of cytoplasm and cell membrane
Apocrine secretion
FEATURES:
Elongated secretory
portion; duct usually
short or absent
EXAMPLES:
Mucous glands of colon;
intestinal glands or
crypts (of Lieberkühn)
Simple Tubular
FEATURES:
Several long secretory
parts joining to drain
into 1 duct
EXAMPLES:
Glands in the
uterus and stomach
Branched Tubular
FEATURES:
Secretory
portion is very long
and coiled
EXAMPLES:
Sweat glands
Coiled Tubular
FEATURES:
Rounded, saclike
secretory portion
EXAMPLES:
Small mucous
glands along the
urethra
Simple Acinar (or
Alveolar)
FEATURES:
Multiple saclike
secretory parts entering
the same duct
EXAMPLES:
Sebaceous glands of
the skin
Branched Acinar
FEATURES:
Several elongated coiled secretory units and their
ducts converge to form larger ducts
EXAMPLES:
Submucosal mucous glands (of Brunner) in the
duodenum
Compound Tubular
FEATURES:
Several saclike secretory units with small
ducts converge at a larger duct
EXAMPLES:
Exocrine pancreas
Compound Acinar
FEATURES:
Ducts of both tubular
and acinar secretory units
converge at larger ducts
EXAMPLES:
Salivary glands
Tubuloacinar
secretion releases products, usually containing proteins, by means of exocytosis at the apical end of the secretory cells.
Merocrine secretion
produced by the disintegration of the secretory cells themselves as they complete their terminal differentiation
Holocrine secretion
involves loss of membrane-enclosed apical cytoplasm, usually containing one or more lipid droplets
Apocrine secretion
a thin extracellular
layer of specialized proteins
basement membrane
is a thin meshwork of type IV collagen and laminin produced by the epithelial cells
basal lamina
contains type III collagen and anchoring fibrils of VII collagen, all secreted by cells of the immediately adjacent connective tissue.
reticular lamina
The major function in many epithelial cells is synthesis and secretion
of specialized products; organs composed primarily of such epithelia
are called
glands
have epithelial ducts carrying secretions to specific sites;
Exocrine glands
lack ducts; secreted substances are hormones carried throughout the body by the interstitial fluid and blood, with
specificity produced by the hormone receptors of target cells
Endocrine glands
