MIDTERM: BONE AND CARTILAGE Flashcards
A tough, durable form of supporting connective
tissue, characterized by an extracellular matrix (ECM) with high concentrations of GAGs and proteoglycans, interacting with collagen and elastic fibers.
cartilage
has a firm consistency that allows the tissue to
bear mechanical stresses without permanent
distortion
cartilage
provides cushioning and sliding regions
within skeletal joints and facilitates bone
movements
cartilage
lack vascular supplies, Also lacks nerves
cartilage
Embedded in the ECM which unlike connective
tissue proper contains no other cell types.
- Synthesize and maintain all ECM
components and are located in matrix cavities
called ________
chondrocytes, lacunae
Cartilage consists of these cells
chondrocytes
Chondrocytes receive nutrients by ________ in surrounding connective
tissue (the perichondrium).
diffusion from capillaries
a sheath of dense connective tissue that surrounds cartilage
perichondrium
harbors the blood supply serving the
cartilage and a small neural component
perichondrium
PHYSICAL PROPERTIES OF CARTILAGE:
TYPE II COLLAGEN FIBRILS
HYALURONAN
PROTEOGLYCANS
covers the ends of bones in movable joints and which erodes in the course of arthritic degeneration
- Lacks perichondrium and is sustained by the diffusion of oxygen and nutrients from the synovial fluid
articular cartilage
3 TYPES OF CARTILAGE
- Hyaline Cartilage
- Elastic Cartilage
- Fibrocartilage
Most common of the three types
- Homogeneous and semitransparent in the fresh state
hyaline cartilage
__________,hyaline cartilage is located in the:
o articular surfaces of movable joints
o in the walls of larger respiratory passages (nose, larynx, trachea, bronchi)
o in the ventral ends of ribs, where they articulate with the sternum
o and in the epiphyseal plates of long boneswhere it makes possible longitudinal bone growth.
in adults
__________,hyaline cartilage forms the temporary skeleton that is gradually replaced by bone.
in the Embryo
- a chronic condition that commonly occurs during aging
- involves the gradual loss or changed physical properties of the hyaline cartilage that lines the articular ends of bones in joints.
Osteoarthritis
The dry weight of hyaline cartilageis _________ collagen embedded in a firm, hydrated gel of proteoglycans and structural glycoproteins.
matrix, is nearly 40%
most collagen in hyaline cartilage
type 2
most abundant proteoglycan of hyaline cartilage
- bind further to the surface of type II collagen fibrils
aggrecan
Structural multiadhesiveglycoprotein
- Binds specifically to GAGs, collagen and integrins mediating the adherence of chrondrocytes to the ECM
CHRONDRONECTIN
makes matrix generally basophilic and thin collagen fibrils barely discernable
PROTEOGLYCANS:
elliptic shape, with long axes parallel to the surface
CHONDROBLAST
- Common in aging
- degenerative changes in the chondrocytes
- resembles endochondral ossification by which bone is formed.
Calcification
a pituitary-derive protein which is a major regulator of hyaline cartilage growth
Somatotropin or growth hormone
acts indirectly, promoting the endocrine release from the liver of insulin-like growth factors, or somatomedins, which directly stimulate the cells of hyaline cartilage
Somatotropin or growth hormone
benign or slow growing tumor which cells produce normal matrix components.
Chondroma
malignant tumor which cells produce normal matrix components.
- seldom metastasize and are generally removed surgically.
Chondrosarcoma
all hyaline cartilage is covered by a layer of dense connective tissue
- essential for the growth and maintenance of cartilage
PERICHONDRIUM
consists largely of collagen type I
fibers and fibroblasts
outer region of perichondrium
adjoining the cartilage matrix also
contains mesenchymal stem cells
inner layer of perichondrium
similar to hyaline cartilage
elastic cartilage
contains an abundant network of elastic fibers in addition to a meshwork of collagen type II fibrils,
elastic cartilage
give fresh elastic cartilage a
yellowish color
More flexible than hyaline cartilage
elastic cartilage
elastic cartilage Found in the:
o auricle of the ear
o the walls of the external auditory canals
o auditory (Eustachian) tubes
o epiglottis
o upper respiratory tract
Mingling of hyaline cartilage and dense connective tissue
- Found in intervertebral discs,
attachment of certain ligaments, and in pubic symphysis
fibrocartilage
the only cartilage that dont have perichondrium
fibrocartilage
All place where it serves as VERY TOUGH, YET CUSHIONING SUPPORT tissue for bone
fibrocartilage
occur single and often in aligned isogenous aggregates producing type II collagen and other ECM components
fibrocartilage chondrocytes
scarcity of proteoglycans
fibrocartilage is acidophilic
fibrocartilage act as lubricated
cushions and shock absorbers preventing damage to adjacent vertebrae from abrasive forces of impacts
INTERVERTEBRAL DISCS OF SPINAL
COLUMN
A process where all cartilage forms from embryonic mesenchyme
CHONDROGENESIS
Poor capacity of cartilage for repair or regeneration is due in part to its
AVASCULARITY and LOW METABOLIC RATE
Is the main constituent of the adult skeleton
Bone (or osseous) tissue
provides solid support for the body, protects vital organs (such as cranial and thoracic cavities and medullary cavities) containing bone marrow where blood cells are formed
Bone (or osseous) tissue
Serves as a reservoir of calcium, phosphate and other ions that can be released or stored in a controlled fashion to maintain constant concentrations in body fluids
Bone (or osseous) tissue
is a specialized connective tissue composed of calcified extracellular material, bone matrix and three major cell types
Bone (or osseous) tissue
3 major cells types of bone
osteocytes
osteoblast
osteoclast
Found in cavities (lacunae) between bone matrix layers (lamellae) with cytoplasmic processes in small canaliculi that extend into the matrix
Osteocytes
Growing cells which synthesize and secrete the organic components of the matrix
Osteoblasts
Bone forming cell
Osteoblasts
Immature cells before turning into osteocytes
Has a prominent nucleus
Osteoblasts
Which are giant, multinucleated cells mvolved in removing calcified bone matrix and remodeling bone tissue
Osteoclasts
Bone consuming cell
Osteoclasts
Macrophage of bone
Osteoclasts
Contains the capillaries, fibroblasts and osteoprogenitor stem cells
Mesenchymal regions
internal surface surrounding the marrow cavity
Endosteum
external surface of the bone
Periosteum
Originated from mesenchymal stem cells
Produce the organic components of bone matrix, including type I collagen fibers, proteoglycans and matricellular glycoproteins such as osteonectin
Are polarized cells with ultrastructural features denoting active protein synthesis and secretion
Osteoblasts
a layer of unique collagen-rich material between osteoblast layer and the pre-existing bone surface
OSTEOID
a vitamin K-dependnet polypeptide, prominent among the noncollagen proteins secreted by osteoblasts
OSTEOCALCIN
release membrane-enclosed by osteoblast
rich in alkaline phosphatase and other
enzymes which raisies the local
concentration of PO4 3− ions
- serve as foci for the formation of
hydroxyapatite crystals, the first visible step in calcification
MATRIX VESICLES
Most abundant cell in bone
OSTEOCYTES
Enclosed singly within the lacunae spaced throughout the mineralized matrix
OSTEOCYTES
where diffusion of metabolites between osteocytes and blood vessels occurs
CANALICULI
detects mechanical load on the bone as well as stress-or fatigue-induced micro-damage and trigger remedial activity in osteoblasts and osteoclasts
MECHANOSENSORS
paracrine and endocrine that helps regulate bone remodeling
proteins
It maintains the calcified matrix and their death is followed by rapid matrix resorption
OSTEOCYTES
Are very large, motile cells with multiple nuclei that are essential for matrix resorption during bone growth and remodeling
Osteoclasts
For the development it needs 2 polypeptides (produced by osteoblasts):
Macrophage-colony-stimulating factor (M-CSF)
Receptor Activator of Nuclear factor B ligand (RANKL)
Areas of bone that undergo resorption. osteoclasts on the bone surface lie within enzymatically etched depression or cavities in the matrix
Resorption lacunae (or Howship lacunae)
the membrane domain that contacts the bone forms a sealing zone that binds the cell tightly to the bone matrix and surrounds an area with many surface projections, called ruffled border
Active osteoclast
Allow the formation of a specialized microenvironment between the osteoclast and the matrix which bone resorption occurs
Circumferential sealing zone
of the dry weight of bone matrix is inorganic materials
About 50%
is the most abundant but bicarbonate, citrate, magnesium, potassium and sodium are also found
Calcium hydroxyapatite
90% but also include
small proteoglycans and multi-adhesive
glycoproteins such as OSTEONECTIN
- Calcium binding proteins, osteocalcin, and
the phosphatases release from matrix vesicles promotes calcification of the matrix
- Because of its high collagen content, decalcified bone matrix is acidophilic
type 1 collagen
notably osteocalcin and the phosphatases released from cells in matrix vesicles promote calcification of the matrix.
Calcium-binding proteins
External and internal surfaces of all bones are covered by connective tissue of periosteum and endosteum
PERIOSTEUM & ENDOSTEUM
Is organized much like the perichondrium of cartilage with an outer fibrous layer of dense connective tissue, containing mostly bundled type I collagen but also fibroblasts and blood vessels
PERIOSTEUM
penetrate the bone matric and bind
periosteum to the bone
- Periosteal blood vessels branch and penetrate the bone, carrying metabolities to and from bone cells
Perforating (or Sharpey) fibers
inner layer and more cellular, includes osteoblasts, bone lining cells, and mesenchymal stem cells
- play a prominent role in bone growth and repair
- proliferate extensively and produce new osteoblasts
OSTEOPROGENITOR CELLS
Internally (inner layer)
Very thin endosteum covers small trabeculae of bony matrix that project into marrow cavities
Also contains osteoprogenitor cells, osteoblasts and bone lining cells but within sparse delicate matrix of fibers
ENDOSTEUM
Types of bone in Macroscopic/Gross Observation Level
- Compact/cortical bone
- Cancellous/ Trabecular bone
Typex of bone in Microscopic level
Lamellar bone
Woven bone
Constituting 20% of the total bone mass/ lamellar bone
Cancellous (trabecular) bone
Deeper areas with numerous interconnecting cavities
Cancellous (trabecular) bone
Dense areas near the surface
Found mostly in the diaphysis of long bones
Also includes parallel lamellae organized as multiple external
Compact (cortical) bone
Represents 80% of the total bone mass/ lamellar bone
Compact (cortical) bone
At the microscopic level both compact & cancellous bone typically show 2 types of organization:
(a) Mature lamellar bone
- With matrix existing as a discrete sheets
(b) Woven bone
- Newly formed with randomly arranged components
With matrix existing as a discrete sheets
Mature lamellar bone
Newly formed with randomly arranged components
Woven bone
outer and innermost areas of compact bone enclose and strengthen the middle region containing vascularized osteons
Lamellae
Most bone in adults, compact or cancellous, is organized as
Lamellar bone
- Bulbous ends
- Composed of cancellous bone covered by a thin layer of compact cortical bone
EPIPHYSES
Almost totally dense compact bone with a thin region of cancellous bone on the inner surface around the central marrow cavity
DIAPHYSES
Flat bones that form the calvaria
(skullcap) have two layers of compact bone
PLATES
a thicker layer of cancellous bone that separates the plates
DIPLOE
Refers to the complex of concentric lamellae surrounding a central canal that contains small blood vessels, nerves and endosteum
It is the one that usually form the compact bone
Osteon (haversian system)
A transverse use by canals in
communicating with one another
PERFORATING CANALS (Volkmann
canals)
Scattered among the intact osteons are numerous irregularly shaped groups of parallel lamellae
INTERSTITIAL LAMELLAE
Beneath the periosteum
EXTERNAL CIRCUMFERENTIAL
LAMELLAE
Around the marrow cavity
INNER CIRCUMFERENTIAL LAMELLAE
Pathway of bone
Lamellae/lamellar
Occurs continuously thoughout life
- In compact bone, remodeling resorbs parts of old osteons and produce new ones
- In healthy adults, 5%-10% of the bone turns over annually
BONE REMODELING
Is nonlamellar and characterized by random disposition of type I collagen fibers and is the first bone tissue to appear in embryonic development and in fracture repair
Is usually temporary and is replaced in adults by lamellar bone, except in some places of the body
Woven Bone
newly calcified
Woven bone
Remodeled from woven bone
Lamellar bone
80% of all lamellar bone
Compact bone
20% of the lamellar bone
Cancellous bone
Irregular and random arrangement of cells. and collagen, lightly calcified
Woven bone
Parallel bundles of collagen in thin layers (lamellae) with regularly spaced cells between; heavily calcified
Lamellar bone
Parallel lamellae or densely packed osteons with interstitial lamellae
Compact bone
Interconnected thin spicules or trabeculae covered by endosteum
Cancellous bone
Bone development occurs by one of two processes:
Intramembranous ossification
Endochondral ossification
In which osteoblasts differentiate directly from mesenchyme and begin secreting osteoid
Bone generates through membranes
By which most flat bones begin to form, takes place within condensed sheets (“membranes”) of embryonic mesenchymal tissue
Intramembranous ossification
Preexisting matrix of hyaline cartilage is eroded and invaded by osteoblasts which then begin osteoid production
Endochondral ossification
Takes place within hyaline cartilage
Shaped as a small version or model of the bone
formed
Bones are well studied in developing long bones where it consists a sequence of events
Endochondral ossification
Also called epiphyseal plate
At the age of 18, bone growth stops
➤ Is responsible for the growth in length of the bone and disappears upon completion of bone development at adulthood
Epiphyseal cartilage
Is composed of typical hyaline cartilage
Zone of reserve (or resting) cartilage
Cartilage cells divide repeatedly, enlarge and secrete more type II collagen and proteoglycans and become organized into columns parallel to the long axis of the bone
Proliferative zone
Chondrocytes undergo mitosis and appear stacked within elongated lacunae
Zone of proliferation
Mature chondrocytes in lacunae swell up. compress matrix and undergo apoptosis
closer to the large primary ossification center
Zone of Hypertrophy
Spaces created in the matrix by these events
When they are invaded by osteoblasts, osteoclasts and vasculature from the primary center
zone of cartilage calcification
Woven bone is laid down initially by osteoblasts and remodeled into lamellae bone
Zone of ossification
Increases the circumference of a bone by osteoblasts activity at the periosteum and is accompanied by enlargement of the medullary marrow cavity
Appositional bone growth
Raises low blood calcium levels by stimulating osteoclasts and osteocytes to resorb bone matrix and release Ca2+
PTH effect on osteoclast is indirect
Parathyroid hormone (PTH)
Produced within the thyroid gland, can reduce elevated blood calcium levels by opposing the effects of PTH in bone
Calcitonin
Are regions where adjacent bones are capped and held together firmly by other connective tissues
JOINTS
2 types of joints
Diarthroses (freely movable joints)
Synarthroses (immovable joints)
Allow very limited or no movement and are subdivided into fibrous and cartilaginous joints, depending on the tissue joining the bones
Synarthroses joints
Major subtypes of Synarthroses:
Synostases
Syndesmoses
Symphyses
Involve bones linked to other bones and allow
essentially no movement
In older adults, it unites the skull bone
In children and young adults, it is held together by sutures or thin layers of dense connective tissue with osteogenic cells
Synostases
Involve bones linked to other bones and allow
essentially no movement
In older adults, it unites the skull bone
In children and young adults, it is held together by sutures or thin layers of dense connective tissue with osteogenic cells
Synostases
Join bones by dense connective tissue only Ex interosseous ligament of inferior tibiofibular joint & posterior region of sacroiliac joints
Syndesmoses
Join bones by dense connective tissue only Ex interosseous ligament of inferior tibiofibular joint & posterior region of sacroiliac joints
Syndesmoses
Have thick pad of fibrocartilage between thin articular cartilage covering the ends of the bones
Ex. intervertebral discs
Symphyses
In a diarthroses ligament and a capsule of dense
connective tissue
Freely mobile joints
Classified as free bone movement
Diarthrosis Joints
In a diarthroses ligament and a capsule of dense
connective tissue
Freely mobile joints
Classified as free bone movement
Diarthrosis Joints
2 specialized cells of diarthrosis joints:
(a) Macrophage-like synovial cells (type A cells)
(b) Fibroblastic synovial cells (type B cells)
Derived from blood monocytes and remove wear and tear debris from the synovial fluid
Represent approximately 25% of the cells lining the synovium which are important in regulating inflammatory events with diarthrotic joints
(a) Macrophage-like synovial cells (type A cells)
Produce abundant hyaluronan and smaller amounts of proteoglycans
Materials is transported by water from the capillaries into the joint cavity to form the synovial fluid
(b) Fibroblastic synovial cells (type B cells)
Cancer originating directly from bone cells. (primary bone tumor) is fairly uncommon (0.5% all cancer deaths)
Arise in osteoprogenitor cells
The skeleton is often the site of secondary, metastatic tumors however arising when cancer cells move into bones via small blood or lymphatic vessels from malignancies in other organs
• Most commonly breast, lung, prostate gland, kidney or thyroid gland
Multiple production of bone
Osteosarcoma
Extensive network of osteocvte dendritic processes and other bone cells called “mechanostat”
Monitoring mechanical loads within bones and signaling cells to adjust ion levels and maintain the adjacent bone matrix
Resistance exercise can produce increased bone density and thickness in affected regions,
While lack of exercise (or weightlessness experienced by astronauts) leads to deeased bone density, due in part to the lack of mechanical stimulation of the bone cells
Mechanostat
Common among postmenopausal women
because it lacks of estrogen
Estrogen is hormone responsible for strengthen bone in women
Also common to immobilized patients
Osteoporosis
Characterized by dense, heavy bones (“marble bones”)
• Osteoclast lack ruffled borders and bone resorption is defective
o Defective osteoclasts in most patients with osteopetrosis have mutations in genes for the cell’s proton-ATPase pumps or chloride channels
Opposite of osteoporosis & a genetic disease
Result to overgrowth a thickening of bones, often with obiteracion of the marrow cavities, depressing blood cell formation and causing anemia and the loss of WBC
Osteopetrosis
Refers to a group of related congenital disorders in which the osteoblasts produce deficient amounts of type I collagen or defective type I collagen due to genetic mutations
It will lead to a spectrum of disorders, all characterized by significant fragility of the bones
The fragility reflects normal collagen, which normally reinforces and adds a degree of resiliency to the mineralized bone matrix
Osteogenesis imperfecta (“Brittle bone disease”)
Is a fluorescent molecule that binds newly
deposnea oreoramic during mineralization with high affinity and specifically labels new bone under the UV microscope
Is has been found that it lowers the rate of bone growth
A bone biopsy was performed, bone was
sectioned without decalcification and examined Appears that fluorescent lamellae and the distance between the labeled layers is proportional to the rate of bone appositional growth
This procedure is of diagnostic importance in such diseases as osteomalacia, in which mineralization is impaired and osteitis fibrosa cystica, in which osteoclast activity results in removal of bone matrix and fibrous degeneration
Antibiotic Tetracycline
Calcium deficiency in children
A disease in which the bone matrix, does not calcify normally and the epiphyseal plate an be distorted by the normal strains of bone weight and muscular activity
Insufficient calcium in the diet or failure to produce the steroid prohormone vitamin D with important absorption of Calcium oy cens of the small intestine
Rickets
Adults calcium deficiency
• Dencient calcification of recently formed and partial decalcification of already calcified matrix
Osteomalacia
Lack of growth hormone during the growing years
Pituitary Dwarfism
Excess growth hormone causing excessive growth of the long bones
Gigantism
A disease in which the bones- mainly the long ones- becomes very thick
Acromegaly
Chronic inflammation of the synovial membrane causes thickening of this connecave ussue and stimulates the macrophages to release collagenases and other hydrolytic enzymes
Some enzymes eventually causes destruction of the articular cartilage allowing direct contact o the bones projecting into the joint
Rheumatoid arthritis
Within an intervertebral dises
Collagen toss or other degenerative changes in the annulus fibrosus are often accompanied by displacement of the nucleus pulposus
Occurs most frequently on the posterior region of the intervertebral disc where there are fewer collagen bundles
Affected disc dislocates or shifts slightly from its normal position
The pain accompanying a slipped disc may be perceived in areas innervated by the compressed nerve fibers- usually the lower lumbar region
Slipped or herniated disc
