Test 2 Flashcards
what kind of tissue is cartilage and what does it contain?
cartilage is a specialized connective tissue; it is avascular and lacks nerve fibers and contains cells, fibers, and ECM
what are the three types of cartilage?
hyaline cartilage, elastic cartilage, and fibrocartilage
describe hyaline cartilage
known for its “glassy” appearance and is the most common type; composed mostly of type II collagen
where can you find hyaline cartilage?
in places where it maintains a lumen/space open (nose, larynx, trachea, and bronchi), at articular surfaces of bones (ventral ends of the ribs that articulate with sternum, articulating surfaces of mobile joints such as femur), and at epiphyseal plates (“growth” plates of growing bones)
what are the functions of hyaline cartilage?
to maintain an open lumen/space, to act as a shock absorber, and to allow friction-free gliding between bones of moveable joints
what is the function of epiphyseal growth plates?
they allow long bones to grow in length; they start as hyaline and are eventually replaced completely by bone
describe the histogenesis of hyaline cartilage
mesenchymal cells retract their cell processes and become round-shaped cells. these cells form chondrification centers which are future cartilage sites. mesenchymal cells then differentiate into chondroblasts which synthesize more of this matrix in their surroundings, they become trapped in lacunae
what does “isogenous” mean?
isogenous cells are progeny of a single cell and are genetically uniform
describe the perichondrium
a connective tissue capsule that covers only hyaline and elastic cartilage; composed of 2 cell layers: the outer fibrous layer that contains fibroblasts and the inner cellular layer composed of chondrogenic cells
explain how cellular growth occurs in perichondrium
the perichondrium has vessels to provide oxygen and nutrients; the nutrients and oxygen can get into cartilage layer; when there isn’t enough diffusion, the cells in the hyaline cartilage layer break down and new cells form from the perichondrium and move inward
what are the 2 mechanisms of cartilage growth
interstitial growth (cartilage grows from within); appositional growth (cartilage grows on the surface)
where does interstitial growth occur?
during early stages of cartilage formation, in articular cartilage (does not have perichondrium), in growth plates, and deep within the cartilage
what makes up the hyaline cartilage matrix?
proteins (mainly type II collagen; cannot be seen with staining so that is why you see glassy), proteoglycans, glycoproteins, and extracellular fluid
what are the three different types of cartilage cells?
chondrogenic cells, chondroblast and chondrocytes
describe chondrogenic cells
arise from mesenchymal cells and differentiate into chondroblasts and osteoprogenitor cells
describe chondroblasts
differentiate from mysenchymal cells in the chondrification center and/or chondrogenic cells in the inner perichondrium; form matrix and fibers of cartilage
describe chondrocytes
“grown up” chondroblasts; have large nucleus and prominent nucleoulus; can go back to being chondroblasts; are trapped in lacuna, and monitor matrix composition; synthesize necessary molecules to maintain cartilage matrix
where would you find elastic cartilage?
pinna of the ear, internal and external auditory tubes, the epiglottis, and larynx
how is elastic cartilage different from hyaline cartilage?
it contains not only type II collagen, but also elastic fibers in the ECM and in the fibrous layer of the perichondrium; it also has larger chondrocytes than hyaline cartilage, is more flexible and elastic than hyaline cartilage, and is yellow in the fresh state
describe fibrocartilage
transitional form between dense connective tissue and hyaline cartilage; contains chondrocytes and type I collagen; lacks a perichondrium
where do you find fibrocartilage
in areas requiring tough, tensile strength; can be seen in intervertebral discs, pubic symphysis, articular dists, menisci of knee joints, and attached to bones (between tendons and bones)
how are fibroblasts and chondrocytes related
fibroblasts secrete proteoglycans that become surrounded by matrix and become chondrocytes
osteoarthritis
articular surface of bone where cartilage has degenerated, exposing the underlying bone; caused by the breakdown of hyaline cartilage which normally provides a slippery surface for articulating bones; most prevalent in older individuals
tell me some general things about bone
it is a specialized connective tissue; bone is mineralized, living tissue that is continuously being remodeled; bone serves as a storage depot for minerals; bone marrow is a blood-cell forming tissue; bone supports and protects
how does bone respond to pressure and tension?
pressure applied to bone results in born resorption(breakdown); tension applied to bone results in bone deposition (addition)
what defines a long bone
long bones have long, cylindrical shaft and 2 epiphyses on either end (the heads of the bone)
define metaphysis
angulation between the epiphyseal plate and diaphysis
define diaphysis
diaphysis is the long cylindrical shaft between two epiphyses
what is the periosteum?
the external connective tissue capsule of bone; the periosteum of an actively growing bone has 2 layers - an outer fibrous layer and an inner cellular layer (not defined when inactive)
describe the outer fibrous layer of the periosteum
the outer layer consists of dense collagenous CT; it contains blood vessels, lymphatic vessels, and nerves that supply the bone; it is anchored into bone via Sharpey’s fibers (bundles of collagenous fibers) so it does not slide or peel off of the bone
describe the inner cellular layer of the periosteum
if the bone is actively growing, the inner layer contains osteoprogenitor cells; if the bone is mature and not growing, it contains periosteal cells that have the ability to differentiate into osteoblasts if necessary (for repair); it plays a role in the repair of bone fractures; covers the outer surface of bone, except the articular surface
describe endosteum
internal CT capsule of bone; consists of a thin CT layer with a single row of osteoprogenitor cells that have the ability to differentiate into osteoblasts or bone-lining cells; the endosteum lines the bone marrow cavity
what are the 2 component of bone matrix?
inorganic component and organic component
what makes up the inorganic layer of the bone matrix?
minerals; hydroxyapatite crystals (calcium phosphate), bicarb, citrate, magnesium, sodium, potassium
what makes up the organic layer of the bone matrix?
fibers (type 1 collagen mostly), ground substance (proteoglycans, glycoproteins, growth factors)
define osteonectin
serves as glue between collagen and hydroxyapatite crystals
define sailoproteins
help bind cells to bone matrix; examples are osteopontin and sialoproteins I and II; sailoproteins also begin calcium phosphate formation
define osteocalcin
traps calcium from the blood and stimulates osteoclasts to remodel bone
define trabeculae
islands of bone
what are the 2 ways to form bone?
via intramembranous ossification or endochondral ossification
what forms first - spongey bone or compact bone
spongey bone forms first, but it can become compact bone
how do blood vessels end up in bone?
during bone development, bone grows around blood vessels
intramembranous ossification
bone forms directly within a membrane of highly vascular mesenchyme; the mechanism by which flat bones form (face bone, skull, clavicle)
endochondral ossification
bone forms in hyaline cartilage; mechanism by which long bones form; forms a cartilage mold to be filled by bone
what are the layers of the eye
fibrous layer (corneoscleral coat), vascular layer (uvea), and retina (neural layer)
what are the chambers of the eye?
anterior segment (anterior chamber and posterior chamber), and posterior segment (vitreous chamber)
what are the 5 layers of the cornea (outside to in)
corneal epithelium, bowman’s membrane, corneal stroma, Descemet’s membrane, corneal endothelium
explain Bowman’s Membrane
acellular, does not regenerate, terminates at corneoscleral limbus, contributes to strength of cornea, is barrier to infections
corneal stroma
collagen fibrils arranged in lamellae; adjacent lamellae are arranged at right angles to each other, this maintains the transparency of the cornea; AKA substantia propia
Descemet’s membrane (posterior basement membrane)
regenerates after injury, thickens with age, helps maintain the normal curve of cornea
corneal endothelium
simple squamous epithelium, joined by zona adherens, zona occludens, and desmosomes; limited proliferative ability; responsible for virtually all of the metabolic exchange of the cornea
sclera
white of the eyeball that gives the eye shape; provides attachment for eye muscles; made up of 3 layers - episcleral/Tenon’s space, substantia propria (Tenon’s capsule), and suprachoroid lamina
iridocorneal angle
apparatus for outflow of aqueous humor
ciliary processes
secretion and anchoring of zonule fibers, form suspensory ligaments of the lens; form blood-aqueous layer, produce aqueous humor
what is the flow of aqueous humor?
posterior chamber –> pupil –> anterior chamber –> trabecular meshwork –> Canal of Schlemm –> venous system
open angle glaucoma
vision is damaged gradually; may take place over the course of some years; caused by blockage of meshwork leading to the canal of schlemm
fovea centralis
point of retina with the greatest visual acuity
Retinal Pigment Epithelium (RPE)
attached through Bruch’s membrane to the choriocapillary layer of the choroid; mechanical separation at this point is known as a “detached retina”
name 2 photoreceptors
rods and cones
name 2 conducting neurons
bipolar cells and ganglion cells
name 3 supporting/neuroglial cells
Muller’s cells, microglial cells, astrocytes
what are cones responsible for?
color
what are rods responsible for
low intensity light
are rods or cones more abundant?
rods
what vitamin is associated with rods?
vitamin A: retinal
what defines a bipolar cell?
1 cell body in the middle with the dendrites and axon coming off of a long neck
what is the most common cause of blindness?
diabetic retinopathy; neovascularization of the retina
what does macular degeneration affect?
the fovea centralis; causes blurriness in the center of your vision due to drusen (lipid deposit near the macula and fovea centralis)
where does drusen occur?
inferior to RPE
what are the three parts that make up the lens
the capsule (basal lamina), the subcapsular epithelium, and the lens fibers
where does cataracts act?
the lens; loss of transparency
what occurs to the lens as you age?
fibers stiffen and enlarge with age
conjunctiva
stratified columnar epithelium with goblet cells and basal lamina overlying a loose connective tissue; secretions produce a tear film to protect cornea
what are 2 sebaceous glands found in the eyelids?
Meibomian (tarsal) glands and Glands of Zeis (smaller glands opening into eyelash follicles)
explain the layers of the tympanic membrane
external layer is thin epidermis, intermediate layer is collagen and elastic fibers (fibroblasts), and the internal surface is simple squamous to simple cuboidal
what are the ossicles lined with?
simple squamous epithelium
what histology defines the auditory tube?
pseudostratified columnar epithelium with goblet cells
what are the 3 fluid-filled spaces in the internal ear?
endolymphatic space, perilymphatic space, and cortilymphatic space
endolymph is found where
membranous labyrinth
where can you find the perilymph?
bony labyrinth
where can you find corilypmh
in the corticolymphatic space in the cochlear duct
what fluid is perilymph similar to?
extracellular fluid (high in sodium, low in potassium)
what fluid is endolymph similar to?
intracellular fluid (high in potassium, low in sodium)
what are the sensory cells for the semicircular canals?
crista ampullaris; located in the amuplla of the semicircular duct and canal; senses angular, rotational movements of the head
what is the sensory cell for the utricle and saccule?
macula; have otolithic membrane, otoliths, and hair cells
type 1 hair cells
surrounded entirely by efferent nerve
type 2 hair cells
efferent nerve found on the base
what are the three compartments of the cochlear duct?
scala media, scala vestibuli, and scala tympani
scala media
the cochlear duct; filled with endolymph
scala vestibuli
space above cochlear duct; located on the vestibule; filled with perilylmph
vestibular (reissner’s) membrane
keeps the ionic gradient; has tight junctions to separate the endolymph and perilymph
what is an active fibroblast?
posesses the cellular machinery for the synthesis and secretion of fibers and ground substance; typically do not divide, but may do so during wound healing (fibroplasia)
what is a quiescent fibroblast?
commonly referred to as fibrocytes; smaller than the fibroblast, is spindle-shaped, possesses fewer processes. as an eosinophilic cytoplasm, nucleus is elongated and heterochromatic, and nucleoli are not visible; when stimulated, fibrocytes become fibroblasts
how can you tell a quiescent fibroblast from an active fibroblast?
a quiescent fibroblast (fibrocyte) has an elongated, basophilic nucleus; an active fibroblast has a spherical nucleus and is lighter in color due to euchromatin
what defines a unilocular adipocyte?
unilocular adipoctes or white adipose tissue is defined by the presence of a signet ring in light microscopy; this is due to the removal of lipid during tissue processing; the nucleus in unilocular adipocytes can be seen in the periphery of the cytoplasm
how is collagen synthesized?
- 3 mRNA strands are made 2. triple helix is assembled in rER. each helix has extensions that make it soluble. these extensions are processed by fibroblasts 3. triple helix with propeptides are packaged in vesicles in the Golgi 4. when released into ECM, they are assembled into fibrils or larger collagen molecules; for this to happen they must become less soluble by eliminating extensions
why is hydroxylation important in collagen formation?
proline and leucine must be hydroxylated for collagen to form properly; for this to happen vitamin C needs to be present; deficiency in vitamin C leads to scurvy
what is a myofibroblast?
possesses characteristics of fibroblasts and smooth muscle cells; actin and myosin are present, thus it has contractile activity
dupuytren’s contracture
repair of microvascular ischemia in the tissue leads to active myofibroblast and fibroblasts; increase of type III collagen forms cross links with myofibroblasts leading to the contraction of 4th and 5th digits
what defins multilocular adipocytes?
aka brown adipose tissue; smaller than unilocular cells and well-endowed with mitochondria; nucleus is spherical and not displaced peripherally
lipodystrophies
acquired or inherited loss of body fat to a general or confined area of the body
what defines a mast cell
large, ovoid cell with membrane bound granules that contain diverse chemical compounds
what are mast cells responsible for?
mediators of the inflammatory responses and hypersensitivity reactions; trigger causes mast cell to release the chemicals from secretory granules
what is a macrophage derived from
a monocyte
how is a macrophage formed?
a monocyte migrate into connective tissue from the bloodstream where it develops into a macrophage
what defines a macrophage?
oval nucleus with clumps of heterochromatin; functions in phagocytosis; nucleus is indented
what is a giant cell?
macrophages fuse together in states of chronic inflammation to form giant cells
what are migratory cells?
cells that migrate into the connective tissue from the blood
where are plasma cells derived?
B lymphocytes in the ECM
what are 3 signature features of plasma cells?
basophilia due to large volume of rER; large negative Golgi with absence of secretory vesicles; clock face nucleus due to arrangement of euchromatin and heterochromatin
what is the function of plasma cells?
synthesis and release of immunoglobins; can be seen where bacteria and antigens have entered connective tissue
what is the function of leukocytes?
monocytes, lymphocytes, neutrophils, eosinophils, and basophils migrate from blood into the connective tissue during inflammatory response; neutrophils are the first response followed by monocytes as the second response
what are the 2 classes of embryonic CT?
mesenchymal and mucous
what are the 2 classes of CT proper?
loose and dense; dense can be regular or irregular in arrangement
what are the 5 types of specialized CT?
adipose, bone, blood, cartilage, reticular
true or false: mesenchymal tissue is the most differentiated CT?
false; it is the least differentiated
what defines loose CT
abundant, viscous, amorphous with hyaluronic acid, GAGs, proteoglycans, and glycoproteins
mucoid degeneration of anterior cruciate ligament
presents in patients as knee pain or restricted movement; can be age related degeneration, congenital or acquired synovial tissue entrapment between ACL fibers
what does dense regular CT look like
elastin forms thin sheets of fenestrated membranes; elastic fibers run parallel to one another with few collagen fibers
where is dense regular CT found?
ligamentum flava, the suspensory ligament of penis, arteries, and vocal ligament
are lamellae and laminae elastic fibers?
no, they lack microfibrils needed to form fibers; they do have elastin; can be found in aorta
where can you find dense irregular CT?
organ capsules, dermis of skin, sleeve around nerves
Ehlers-Dalos syndrome
presents as hyperelasticity of skin and hypermobility of joints; defect in type 1 collagen
what is reticular CT made of
reticular (type III collagen)
Achilles tendon xanthoma
results from macrophages invading area and phagocytosing cholesterol and accumulating cholesterol; also seen in arteries with atherosclerosis
where is reticular tissue found?
red bone marrow, liver, and lymphatic tissues/organs
what is fibronectin
an adhesive glycoprotein that assists chondroblasts and chondrocytes to adhere to the ECM
describe the capsular/pericellular matrix of hyaline cartilage matrix
intensely-stained thin layer of matrix immediately around lacuna; contains highest concentration of proteoglycans, hyalouronan, and glycoproteins
describe the territorial matrix of hyaline cartilage
the lighter-staining matrix that surrounds the isogenous group; contains collagen and a lower concentration of proteoglycans than the capsular matrix
describe the interterritorial matrix of hyaline cartilage matrix
represents most of the matrix; fills the space around the territorial matrix
osteoprogenitor cells
early stage, immature bone cells; arise from mesenchymal stem cells
where can you find osteoprogenitor cells
the inner layer of periosteum (here they are called periosteal cells) and the endostem (here they are called endosteal cells)
what do osteoprogenitor cells turn into
differentiate into osteoblasts and chondrogenic cells )in low oxygen tension)
when are osteoprogenitor cells active?
during bone growth
what is an osteoblast
cells that arise from osteoprogenitor cells; cuboidal-columnar shaped cells that synthesize and secret osteoid, the organic component of the bone matrix
what is the function of osteoblasts
they are in charge of the mineralization of the bone matrix
what do osteoblasts become when they are enclosed in the matrix they produce?
osteocytes
explain the function of alkaline phosphatase
osteoblasts contain high levels of the enzyme alkaline phosphatase; when they synthesize bone, there is an increase in alkaline phosphatase levels in the blood; alkaline phosphatase splits pyrophosphate from groups from the macromolecules of the matrix
what are bone-lining cells
arise from osteoblasts and cover one surface, protecting it from osteoclasts. expose bone is vulnerable to resorption by osteoclasts;
what do bone-lining cells do?
function in nutritional support of osteocytes, function in the uptake and release of calcium
what are osteocytes?
grown up osteoblasts, quiescent cells, that maintain bone matrix; enclosed in lacuna
what is periosteocytic space
the space between the osteocyte cell membrane and the lacuna and canaliculi
what are osteoclasts
multinucleated, motile, acidophilic, enormous cells; resorb, remodel, “chisel” bone;
how does an osteoclasts break down bone?
the acidic environment created by osteoclasts breaks down the inorganic component of bone. the minerals released pass into the cytoplasm of the osteoclasts and are then transported into capillaries
what happens to osteoclasts after they complete their bone resorption assignment?
apoptosis!
what enzymes are released from osteoclasts to break down organic components of the decalcified matrix?
lysosomal hydrolases and metalloproteinases
describe compact bone
dense, solid bone that forms a shell around the exterior of long bones; an example is the calvaria; contains Haversian systems (osteons)
describe cancellous bone
spongey, porous bone that lines the marrow cavity of long bones; fills epiphyses of long bones; contains mainly irregular arrangement of bone lamellae
describe primary (immature, woven, bundle) bone
forms during fetal development and bone repair; contains irregular bundles of collagen; less mineral content than mature bone; this is a temporary tissue that is resorbed by osteoclasts and replace them with secondary bone
describe secondary (mature, lamellar) bone
consists of parallel or concentric bone lamellae; has more mineral content than primary bone, so it is stronger; may exist as spongy or compact bone
what is a Haversian canal?
aka osteonal canal; a vascular space that encloses a neurovascular bundle; has a vein, artery, and nerve, but no lymphatic vessels; consists of concentric bone lamellae
what are Volkmann’s canals
obliquely oriented canals that connect osteons that are next to each other; they do not have concentric lamellae of bone that is characteristic of Haversian systems
how do osteons form
during bone formation, osteons form from outside to inside; the bone grows around an existing blood vessel which then becomes trapped in bone
what is ankylosis?
trauma introduced that damages hyaline cartilage; this results in fusion of two articulating bones, obliterating the joint and creating a joint without movement; can occur in the foot and knee joints of athletes and the hand and finger joints of musicians
rheumatoid arthritis
autoimmune disease that attacks synovial joints, damaging articular cartilages and producing severe pain and disfigurement
Gout
accumulation of uric acid crystals in the joints, especially the joints of the fingers and toes
Rickets
a disorder resulting from calcium deficiency during development, or from inadequate dietary supply of vitamin D; causes osteoid to form incorrectly
Osteoporosis
condition characterized by a reduction in bone mass both in organic and inorganic components of the matrix; bone breakdown by osteoclasts exceeds bone formation by osteoblasts resulting in porous bones that break easily; in women, a drop in estrogen levels causes a increased release of substances that boost osteoclast activity
how do bones grow in length?
long bones grow from the epiphyseal plates; there is cartilage growth in the direction of the epiphysis and bone grown towards the diaphysis
how does the thickness of the growth plate change as you grow? distance between growth plates?
the thickness stays the same and the growth plates grow apart
what is the order of zones in the epiphyseal plate from epiphyseal side towards diaphysis?
zone or reserve cartilage, zone of proliferation, zone of hypertrophy, zone of calcified cartilage, zone of resorption
zone of reserve cartilage
resting zone with typical hyaline cartilage
zone of proliferation
chondrocytes proliferate and form isogenous groups; produce organic matrix
zone of hypertrophy
glycogen in chondroytes and enlarged lacunae
zone of calcified cartilage
lacunae coalesce, chondrocytes die, calcification of cartilage matrix
zone of resorption
calcified cartilage remnants form long spicules in the direction of diaphysis, blood vessels bring osteoprogenitor cells to invade this zone; osteoprogenitor cells emigrate to calcified cartilage matrix area and differentiate into osteoblasts
how do you distinguish between calcified cartilage and mineralized bone?
with H&E staining: calcified cartilage is basophilic without cells; mineralized bone is acidophilic and has living cells
achondroplasia
characterized by decrease in production of cartilage cells in epiphyseal growth plates of long bones; cartilage is replaced by bone in a slow rate, resulting in short upper and lower limbs
