Histo

Front 1

origin of bone and cartilage

Back 1

mesenchyme

Front 2

formation of chondrocytes

Back 2

mesenchymal cells migrate, aggregate, and condense and give rise to condrogenic cells. They then develop into condroblasts, which secrete an ECM. the chondroblasts mature into chondrocytes.

Front 3

perichondrium

Back 3

a fibrous CT covering in cartilage

Front 4

what cartilage does not contain

Back 4

nerves, vasculature or lymphatics

Front 5

how nutrients and waste products get to and from cartilage cells

Back 5

simple diffusion

Front 6

composition of cartilage

Back 6

cartliage cells (chondroblasts and chondrocytes), the ECm and the periochondrium

Front 7

fibers of cartilage ECM

Back 7

mostly type 2 collagen, of small diameter. may also contain small amounts of other collagens. cannot see the fine fibrillar matrix of cartilage at the light microscope level

Front 8

amorphous ground matrix of catilage

Back 8

composed mostly of the proteoglycan, aggrecan

Front 9

composition of aggrecan

Back 9

each monomer had a core protein, with a multitude of glycosaminoglycan chains. the chains are higly sulfated molecules of keratin sulfate and chondroitin sulfate. The core protein is linked it hyaluronic acid by link protein as well as by a globular domain in the terminal portion of the core protein itself.

Front 10

purpose of collagen within cartilage

Back 10

provides tensile strength

Front 11

purpose of aggrecan in cartilage

Back 11

contains a high concentration of negative ions of attract and bind vast quantities of water molecules

Front 12

how cartilage acts as a shock absorber

Back 12

releases water when under compression and attracts water when not under compression

Front 13

ultrastructure of chondroblasts

Back 13

extensive amount of rough ER, a well-developed golgi, lipid depostis and glycogen pariticles.

Front 14

cartilage growth interstitially

Back 14

by the mitotic division of chondroblasts within lacunae

Front 15

cartilage growth appositionally

Back 15

by the development of new cells from the chondrogenic layer of the perichondrium

Front 16

hyaline cartilage

Back 16

most common cartilage type, has a smooth homogeonous appearance of its ECM. contributes strength and flexibility where needed

Front 17

locations of hyaline cartilage

Back 17

fetal skeleton, costal cartilage of ribs, trachea, bronchi, epiphyseal plate in long bone.

Front 18

synovial joints

Back 18

composed of a fibrous capsule, synovial membrane, and an articular layer of cartliage (hyaline cartilage)

Front 19

is there a perichondrium in cartilage of synovial joints?

Back 19

no, because nutrients pass into the cartilage by diffusion from the synovial fluid and leave by the same mechanism

Front 20

production of synovial fluid

Back 20

produced by a thin layer of specialized epithelial cells that line the joint capsule. the epithelium is unusal in that it has no basement membrane which makes it susceptible to immune attack in rheumatoid arthritis

Front 21

isogenous groups

Back 21

closely-packed chondroblasts. especially prominent in the area of growth plates in long bones. It is composed of daughter cells of a common ancestral chondroblast.
the cells are undergoing rapid mitosis, so individual cells do not have the opportunity to make their own domains of ECM

Front 22

perichondrium

Back 22

surrounds the entire hyaline cartilage
has a fibrous layer similar to dense CT, with fibroblasts, type 1 collagen fibers, vasculature, nerver and lymphatics.
has a chondrogenic layer which is a source of cartilage precursor cells, which are capable of transformation into flattened condroblasts or rounder more mature chondroblasts-shape is a indicator of activity level

Front 23

Elastic cartilage

Back 23

has elastic fibers in its ECM, as well as the same ECM components found in other cartilage (type II collagen, minor collagens, same amorphous ground substance).
the fibers provide an increased amount of flexibility designed to with stand repeated flexions and extensions
in the electron microscope, elastic fibers show an amorphous elastin core that is built upon and surrounded by individiual strands of fibrillin
elastic fibers must be stained by an elastic stain to be seen

Front 24

location of elastic cartilage

Back 24

found in structures that must with stand repeated bending: auricle of the ear, external auditory canal, eustachian tube, the epiglotis and the larynx.

Front 25

Fibrocartilage

Back 25

the ECM contains the normal components as well as type I collagen fibrils, which are synthesized by fibroblasts and not chondroblasts.
The type I collagen imparts resistance to compression and to shear forces
fibrocartilage is more flexible than dense regular CT and bone, but tougher than the other cartilage types

Front 26

locations of fibrocartilage

Back 26

found where dense CT is blending into hyaline cartilage like symphysis pubis, intervertebral disks, knee joint, and at attachment points of tendons to bones

Front 27

cellular arrangement in fibrocartilage

Back 27

cells in lacunae assume a linear arrangement, with rows parallel to the direction of tensile forces exerted on the cartilage

Front 28

does fibrocartilage have a perichondrium?

Back 28

no, because it is a transitional or blending zone

Front 29

acidophilia observed in fibrocartilage ECM

Back 29

caused by the presence of type I collagen fibers

Front 30

rheumatoid arthritis

Back 30

an autoimmune dieasese often localized in joints that damages articular cartilage and causes severe joint pain

Front 31

gout

Back 31

a form of arthritis that damages articular cartilage. can be a side effect in the treatment of hypertension by the use of prescription drugs such as thiazide diuretics

Front 32

condroplasiaa

Back 32

a range of disorders classified according to the specific collagen type that is defective. in general, the condroblasts are unable to produce a normal matrix

Front 33

achondroplasia

Back 33

a specific type of dwarfism characterized by shortened limbs on a normal sixed head and trunk. an inherited disorder, is invovles defectice cartilage and bone, preventing proper growth of the bones of the extremities.

Front 34

classifications of bone

Back 34

specialized connective tissue and an organ

Front 35

classifications of bone as an organ

Back 35

long bones, short bones, flat bones, irregular bones

Front 36

bone functions

Back 36

1. form the jointed skeletal system
2. protect vital organs
3. contain bone marrow
4. provide a reservoir

Front 37

osteogenesis

Back 37

the creation of bone as an organ

Front 38

ossification

Back 38

process whereby osteoblasts secrete an organic matrix that becomes calcified
it is the generation of the bone tissue itself

Front 39

calcification

Back 39

the process in which crystals are deposited upon the organic matrix. iti s one part of the ossification process

Front 40

osteoblasts

Back 40

basophilic cuboidal cells that actively secrete the organic component of the ECM.
produce alkaline phosphatase, procollagen, and non-collagenous proteins that have a role in calcification.
stimulated by vitamin D, calcitonin, estrogen and various growth factors
contain receptors for PTH, which inhibit their activity
originate from osteoprogenitor cells in the periosteum and bone marrow
cabale of active cell division
found in the endosteal and periosteal surfaces of actively growing bone
maintain communication with each other my means of gap juntcions
have a prominent golgi and RER

Front 41

osteoid

Back 41

the organic portion of bone ECM. It contains amorphous ground substance composed of proteoglycans, and fibers which are mostly type 1 collagen.

Front 42

principal mineral component of the ECM of bone

Back 42

calcium phosphate. it is present in crystalline form.

Front 43

osteocytes

Back 43

produce and maintain the ECM of bone
are the more mature forms of osteoblasts and no longer have the ability to divide
each cell resides in its own lacuna and communicates through gap junctions which reside in canaliculi
have a large amt of RER when they are actively producing protein

Front 44

osteoclasts

Back 44

they are large, acidophillic cells which are multinucleated.
they are often found within indentations in the bone (howships lacunae)
resorb bone.
secrete acid phosphatase, whish dissolved the calsium phosphate matrix of bone.
stimulated by PTH (indirectly) and inhibited by calcitonin (directly)
they share a common embryonic origin with hemopoietic cells, esp closely related to monocytes
they begin their digestive process extracellularly by secreting enzymes into the lumen adjacent to their "ruffled border".

Front 45

osteoclast process

Back 45

they migrate to an ear of the bone, seal it off, and secrete H to lower the pH of the enclosed space.
they then secrete degredative enzymes into the space, and endocytose the bone remnants for further digestion.

Front 46

architecture of long bone

Back 46

a diaphysis (shaft), 2 epiphyses (ends), metaphysis (funnel like portion of the shaft), and marroe spaces

Front 47

compact bone

Back 47

located in the periphery of the shaft
also called dense or cortical bone

Front 48

trabecular bone

Back 48

central portion of bone
has a spongy appearance
contains spaces for bone marrow
also called cancellous or spongy

Front 49

ground bone method

Back 49

one way to prepare bone for LM
the bone is thinly sliced and finely ground
the matrix is preserved, but the cells are lost

Front 50

demineralized method

Back 50

one way to prepare bone for the LM
the bone is fixed, the calsium phosphate is removed and the reamaining material is embedded and sectioned.
this way preseerves the cells and the organic portion of the ECM

Front 51

osteon

Back 51

a feature of compact bone.
consists of a central (haversian) canal, all of the concentric lamellae and their canilculi.
it cannot grow to an unlimited size
lamellae are concentric plates surrounding the central canal and are composed of collagen fibrils in an orthogonal arrangement and in neighboring lamellae, all the fibers are oriented in a 90-degree angle to the first lamella, which gives it great strength
the haversian canal consisits of blood vessels, nerve processes and lymphatics

Front 52

lacunae

Back 52

the dark spaces between the lamellae
one osteocyte resides in each lacuna
extending between lacunae are canaliculi, through which the processes of adjacent osteocytes communicate via gap junctions

Front 53

lamellae

Back 53

on the outside of the entire compact bone is an outer circumferential lamella.
on the internal surface is an inner circumferential lamella

Front 54

interstitial lamellae

Back 54

the remnants of older osteons that have been partially resorbed and remain btw the fully developed osteons

Front 55

vasculature in bone

Back 55

bone is vascular
vascular supplies in central canals are in direct communication with volkmann's canals, which run at right angles to the haversian canal.
the arteries and veins within volkmanns are extensions or arteries that enter the cortex of the bone at nutrient foramina

Front 56

Periosteum

Back 56

the outer covering of bone
it has 2 layers.
the first layer is an outer fibrous layer
the second layer is an inner cellular layer, which contains the osteoprogenitor cells which give rise to osteoblasts
ligaments and tendons insert into bone by merging with the periosteum-type 1 collagenous fibers called sharpeys fibers extend into the bone, anchoring it firmly.

Front 57

trabecular bone

Back 57

acidiphilic because it has a high content of type 1 collagen.
the basophilic area between trabeculae represents marrow cells within the marrow space. it is basophillic because of the high numbers of nucleated cells.

Front 58

endosteum

Back 58

lines all trabeculae of spongy bone
primarily composed on osteoblasts

Front 59

histological classifications of bone

Back 59

woven (primary or immature)
lamellar (seconday, lay ered or mature)

Front 60

woven bone

Back 60

the first to be deposited during growth or repair
lower mineral concentration (greater proportion of osteoid)
more cellular in appearance
exhibits a random arrangment of collagen fibrils
disorganized structure
also called primary or immature bone
modeled bone

Front 61

lamellar bone

Back 61

also called secondary or layered or mature bone
more mineralized, has fewer cells
highly ordered arrangment of collagen fibrils
replaces woven bone during development of repair
remodeled bone

Front 62

examples of bone deposition and resorption

Back 62

1. in long bones, more deposition occurs in the periosteum side and more resorption occurs on the endosteum side to accomodate a larger marrow cavity
2. in calvaria, growth is rapid on the outer surface and resorption is rapid on the inner surface to allow for an increase in the size of the cranial cavity

Front 63

intramembraneous ossification

Back 63

bone forms directly from the mesenchyme
mesenchyme directly differentiates into osteoblasts that are able to deposit bone tissue
cartilage is not involved in the process
most of the bones of the skull are produced this way

Front 64

step 1 of intramembraneous ossification: appearance of ossification centers

Back 64

the mesenchymal cells proliferate and become highly concentrated.
The region is highly vascularized
the cells differentiate into osteoprogenitor cells which divide into osteoblasts.
the osteoblasts produce the matrix around them and mature to osteocytes
many small calcified regions appear this way

Front 65

step 2 of intramembraneous ossification: Trabecular formation

Back 65

bone is first deposited as tiny, needle like spicules radiating from the ossification center and expanding toward the periphery
the addition of bone to the surfaces of these spicules leads to construction of larger, bony "struts"
then the trabeculae meet, fuse and form a complete bony network containing blood vessels
this results in a sandwich with trabecular bone in the middle and two coverings or hard, dense, lamellar bone
the bony trabeculae are continually remodeled by osteoclasts

Front 66

step 3 on intramembraneous ossification: periosteum construction

Back 66

differentiating cells at the periphery of this entire region form the outer periosteal layer

Front 67

skull bones at birth

Back 67

the bones are separated from one another by narrow seams of CT (sutures) or by larger CT areas (fontanelles) which will ossify later. The central areas (trabecular) are called diploe and have a small amount of marrow and will eventually take on a lamellar structure

Front 68

endochondrial ossification

Back 68

bone tissue is deposited upon a cartilaginous model that serves as a template
long bones develop and grow this way
how marrow cavities are produced

Front 69

step 1 in endochondrial ossification: formation of the cartilage model

Back 69

formation begins in the limb buds under low oxygen conditions
centrally located mesenchymal cells differentiate into chondroblasts which produce a cartilagenous ECM
gradually the mesenchymal mass is replaced by a cartilage model of the bone surrounded by a definitive perichondrium

Front 70

step 2 in endochondrial ossification: deterioration of the cartilage model

Back 70

the limb bud is invaded by blood vessels from the perichondrium
this results in a high oxygen levels and causes the chondrocytes to hypertrophy
their lacunae enlarge and the matrix thins out.
the hypertrophied cells produce alkaline phosphatase which causes the matrix to calcify.
the chondrocytes become completely encased in the calcified ECM and die
because they die, the matrix has nothing to support it, so it disintegrates are creates large spaces in the center of the cartilage model, creating a weak center

Front 71

step 3 in endochondrial ossification: appearance of a bony collar

Back 71

due to the increased oxygen levels from the increased blood supply, progenitor cells in the perichondrium differentiate into osteoblasts.
these osteoblasts deposit bone directly around the periphery of the weakened model, forming a collar and adding support (this step is technically done by ImOs)
the perichondreum can now be referred to the peristeum and will be the source of osteoblasts

Front 72

step 4 in endochondrial ossification: construction of the marrow cavity

Back 72

as the oxygen level increases, a periosteal bud of blood vessels and connective tissue invades the matrix spaces formed by the death of the hypertrophied chondrocytes
the bud deleivers osteoprogenitor cells which give rise to osteoblasts
they attach to the calcified cartilage matrix and deposit bone upon its surface, so these trabeculae has a cartilage core covered by bone
through resorption and depostion, the marrow cavity is carved and hemopoietic cells seed the cavity and bone marrow develops

Front 73

step 5 in endochondrial ossification: primary and seconday centers of ossification

Back 73

bone tissue is first deposited in the diaphysis, in the primary center of ossification
after birth, the secondary centers of ossification develop in the epiphyses. and here ossification begins centrally and radiates peripherally

Front 74

step 6 in endochondrial ossification: epiphyseal plate formation

Back 74

as ossification continues, a plate of cartilage is retained.
it is composed of hyalin cartilage and takes advantage of the fact that cartilage can grow interstitially
because it is not calcified, it appears as a space in X-rays

Front 75

long bone growth

Back 75

the growth plate grows on its epiphyseal sdie and is replaced by bone on its diaphysis side

Front 76

how the bone increases in diameter

Back 76

appositional deposition of bone at the periosteum, combined with resorption os bone at the endosteum

Front 77

closure of the growth plate

Back 77

when the cartilage of the epipyseal plate stopes growing and is replaced by bone
occurs around age 20

Front 78

fracture repair

Back 78

the fractured ends are separated by a gap and woven bone is quickly deposited into this space either by intramembraneous ossification (high oxygen) or endochondiral ossification (low oxygen) or both
may have a bump, a new bony callus
eventually the osteoclasts and osteoblasts replace the woven bone with lamellar bone and original shape reappears.

Front 79

response of high calcium levels

Back 79

C cells in the thyroid gland secrete calcitonin which inhibit osteoclast activity and decrease the level of calcium in the blood

Front 80

response of low calcium levels

Back 80

the parathyroid gland releases PTH which binds to osteoblasts and stimulate them to produce macrophage colony stimulating factor (MCSF) which increases the number of macrophages in the bone marrow, and RANKL, a osteoblast cell surface protein that bind macrophages and stimulates them to differentiate into osteoclasts.

Front 81

green-stick fracture

Back 81

breakage on one side of the shaft of a long bone without actual separation of the ends at the break site.
this occurs because the trabecular bone is weaker than the lamellar bone of the collar

Front 82

breakage at the growth plate

Back 82

when the growth plate is separated from the underlying bone
growth of the bone may be stunted

Front 83

breakage at the neck of the femur

Back 83

this may cut off blood supply to the head of the femus because the femoral head runs through the neck of the femur
this may prevent repair and may cause avascular necrosis of the entire head of the femur

Front 84

rickets

Back 84

a dietary calcium deficiency affecting bone mineralization.
responds well to calcium supplementation

Front 85

giantism/dwarfism

Back 85

over or under secretion of growth hormone which can have profound effects on bone growth

Front 86

osteoporosis

Back 86

postmenopausal condition
lack of estrogen results in underactive osteoblasts but osteoclasts are unaffected, so there is a shift in favor o resorption, or a net loss in bone mass

Front 87

osteogenesis imperfecta

Back 87

a genetic defect involving a collagen gene
may be lethal
responsible fo multiple fractures during childhood