Cartilage and Bone Tissue Flashcards
(41 cards)
1
Q
Where is cartilage found in the body?
A
- articular joints of bones
- organs such as trachea and bronchi
- costal cartilage connecting ribs to sternum
- in the larynx
- in the growth plate of long bones
- in the nose, ears, epiglottis, and Eustachian tubes
2
Q
What are the properties of cartilage?
A
- connective tissue from mesenchymal stem cells
- tough and resilient, cushions joints
- contains 60-80% water
- covered w/ dense perichondrium (helps resist outer cartilage expansion when compressed, contains the stem cells)
- no nerves or blood vessels (nutrients/gases travel from BV’s of surrounding tissue by diffusion)
- difficult to repair if damaged
3
Q
What are the different types of cells found within cartilage?
A
- chondroblast: forms (builds) initial cartilage matrix and are located next to perichondrium; have mitotic capabilities; precursor of chondrocytes
- chondrocyte: mature cells embedded within the cartilage extracellular matrix in a space referred to as a cartilage lacuna; can proliferate to form clusters call isogenous groups (pictured in the other side of the flash card)
4
Q
What is the cartilage extracellular matrix composed of?
What are the fibers present?
A
- composition: hyaluronic acid, proteoglycans, and water
- fibers: type-II collagen, some have added elastin or type-I collagen
5
Q
- layer of dense irregular CT covering hyaline and elastic cartilage
- lacking in fibrocartilage and articular cartilage (a subtype of hyaline)
- essential for growth and maintenance of cartilage
- two layers: outer/fibrous layer and inner/chondrogenic layer
A
perichondrium
6
Q
What is the inner and outer layer of perichondrium composed of?
A
- inner/fibrous layer: type-I collagen and fibroblasts
- outer/chondrogenic layer: adjacent to cartilage ECM, contains mesenchymal stem cells for source of chondroblasts that divide/differentiate into chondrocytes
7
Q
- most abundant type of cartilage
- has a glassy, shiny, smooth surface
- plays key role in bone development and growth
- location: joint surfaces, costal cartilage, larynx, trachea, bronchi, and nose
- cartilage ECM cells secretes contain type-II collagen and proteoglycans (chondroitin sulfate, keratan sulfate, and hyaluronic acid) that all bind to H20 (well hydrated matrix)
- surrounded by perichondrium (except on articular surfaces)
- surrounded by synovial fluid in moveable joints = glides easily
- chondrocytes located within lacunae or isogenous groups: territorial matrix (immediately surround chondrocytes, type-II collagen random and high proteoglycans) and interterritorial matrix (surrounds territorial, contains more type-II collagen and less proteoglycans)
- TLDR: great shock absorbing properties, covers ends of adjoining bones in moveable joints
A
hyaline cartilage
8
Q
- type of cartilage
- contains abundant network of elastic fibers embedded in type-II collagen (w/ staining, elastic fibers appear as dark bundles throughout matrix)
- elastic fibers allow for flexible recoil/rebound = retains shape after deformation
- perichondrium is present
- locations: auricle of ear, walls of external auditory canals, auditory (Eustachian) tubes, epiglottis
A
elastic cartilage
9
Q
- type of cartilage that is a mix of hyaline cartilage and dense CT
- lacks perichondrium
- tough, resists tension, yet cushioning support tissue for bone
- locations: intervertebral discs, pubic symphysis, and some menisci of long bone joints
- chondrocytes typically arranged in single rows of isogenous aggregates
- sparse matrix of type-II collagen, w/ fibroblasts and dense bundles of type-I collagen (fibers oriented in the direction of functional stress and provides extra tensile strength)
A
fibrocartilage
10
Q
- type of cartilage
- found on surfaces of moveable joints (2-5 mm thick)
- comparable to hyaline cartilage (remnant of originial hyaline cartilage template used by the developing bone)
- no perichondrium present
- collagen fibers run perpendicular to the tissue surface, but bend gradually to form an arc
- establishes four zones
A
articular cartilage
11
Q
Briefly describe appositional growth as it relates to cartilage:
A
(chondroblasts adjacent to the perichondrium form new cartilage on the surface)
- perichondrial mesenchymal cells differentiate into chondroblasts
- chondroblasts secrete ECM and become surrounded to form chondrocytes
- process continues to keep adding layers of cartilage on top of previous layer
12
Q
Briefly describe interstitial growth as it relates to cartilage:
A
(growth expands within cartilage)
- chondrocytes within cartilage divide forming clusters of cells called isogenous groups
- they then deposit extracellular matrix, spreading themselves from one another thereby expanding cartilage from within the cartilage, creating territorial matrix
- territorial matrix: newly synthesized ECM adjacent chondrocytes, stains differently
13
Q
Describe the repair of cartilage:
A
- cartilage undergoes very slow, incomplete repair
- more efficient in young children
- poor capacity for repair due to its avascularity and low metabolic rate
- cells from the perichondrium invade damaged area and produce new cartilage or dense CT, may even replace it w/ bone
14
Q
What are the functions of bone?
A
- support: provides structural framework
- movement: acts as levers for skeletal muscles
- protection: of organs
- mineral storage: reservoir for minerals including 99% of body’s calcium
- blood-cell formation: protected space for red marrow
15
Q
- type of bone cell
- mesenchymal cells that produce osteoblasts (found in periosteum and endosteum)
A
osteoprogenitor cells
16
Q
- type of bone cell
- produce osteoid, non-mineralized organic matrix, then initiate and control mineralization of osteoid (organic matrix: type-I collagen and proteoglycans; inorganic matrix: calcium and hydroxyapatite crystals (mineral salts) between fibers)
- produced from mesenchymal stem cells, when active are cuboidal mononuclear cells
- fates: osteocytes embedded in bone, bone lining cell on surface, die by apoptosis
A
osteoblasts
17
Q
- type of bone cell
- mature osteoblasts trapped in bone matrix, located in space called lacuna
- cell processes extend in canaliculi (tiny canals within matrix): communicate w/ other cells by gap junctions, receive nutrient flow via canaliculi
- maintain bone health: mechanosensory cells, control activity of osteoblasts and osteoclasts
A
osteocytes
18
Q
- type of bone cell
- differentiate from monocytic cells (macrophage-like from the blood)
- multinucleated (labeled O): located on bone surfaces, create Howship’s lacunae (labeled H)
- remove bone tissue (bone resorption) by degrading the matrix: secreting acids and proteases
- fate: eventually apoptosis
- important endocrine target for regulating calcium levels
A
osteoclasts
19
Q
What is the overall structure of long bones?
A
- epiphysis: knobby regions at ends of bones, compact bone is superficial w/ trabecular bone deep to surface, contains epiphyseal plate
- diaphysis: elongated shaft
- metaphysis: between diaphysis and epiphysis, consists of spongy bone
- epiphyseal line: within metaphysis, epiphyseal plate has fused
- marrow (meduallary) cavity: cylindrical space in diaphysis containing bone marrow
- articular cartilage: cap of hyaline cartilage found at ends of bones articulating w/ other bones
- primary/secondary osteogenic centers: sites of osteogenesis within cartilage of developing long bones
20
Q
What are the 2 bone coverings?
A
- periosteum: dense irregular CT covering external surface, does not cover articular cartilages, neurovascular, anchored by perforating fibers embedded in bone matrix, contains osteoblasts and osteoblast precursors
- endosteum: CT lining of all trabeculae and marrow cavity; contains osteoprogenitor cells, reticular cells of bone marrow, and CT fibers
21
Q
What are the 2 different types of bone?
A
- compact (cortical) bone: forms outer walls of bones, primary structure (lamellar (layers) either as circumferential arrangement (osteon) or partial rings (interstitial lamellae))
- trabecular (cancellous or spongy) bone: forms network of bony plates or rods surrounded by marrow, no osteons, proximal/distal ends of long bones, can be woven or lamellar bone
22
Q
What is the organization of the osteon (Haversian system)?
A
- osteon: cylindrical/layered structures comprising mature compact bone, run parallel to diaphysis, consists of concentric lamellae (bone matrix surrounding a central canal), has osteonal canal w/ blood vessels/nerves
- concentric lamellae (layered appearance): layers of osteocytes surrounding vessels
- lacunae: where osteocytes reside
- canaliculi: interconnect osteocytes by gap junction channels and reach central blood vessel of osteon
- cement line (CL): outer boundary of the osteon
- circumferential lamellae: line entire inner and outer circumferences of the diaphysis
- interstitial lamellae: remnants of previous concentric lamellae
(lamellar bone = mature bone b/c of layers)
23
Q
Inner _________ bone is surrounded by bone marrow and has source of blood from vessels within the bone marrow cavity
A
trabecular
24
Q
- immature or primary bone, usually replaced by lamellar bone (aka nonlamellar or bundle bone)
- characterized by loose arrangement of collagen fibers
- lower mineral content, more cells
- forms during fracture repair and remodeling: alveolar sockets, tendons insert into bone
A
woven bone
25
- laid down in highly organized layers w/ higher mineral content
- replaces woven bone during remodeling and in maintaining compact bone
lamellar (mature) bone
26
Describe the process of osteogenesis:
(born formation by **appositional growth** (only way to lay down bone) w/ osteoblasts putting bone down on the bone surface, as osteoblasts keep adding layers they become trapped as osteocytes, initial bone formed is woven bone that is later replaced by lamellar bone)
- **intramembranous ossification**: formed directly from mesenchyme, no cartilage involvement
- **endochondral ossification**: develops initially on a hyaline cartilage model
- **in both**: woven bone is produced first and replaced later by lamellar bone
27
- type of osteogenesis
- osteoblasts differentiate directly from mesenchyme and begin secreting osteoid
- no cartilage model, no cartilage involvement
- occurs: flat bones of the skull, most facial bones, mandible, central part of clavicle
intramembraneous ossification
28
- type of osteogenesis
- hyaline cartilage forms the initial model
- occurs in all bones except some bones of skull and central clavicle
- primary centers of ossification begin late in the 2nd month of development
- secondary centers of ossification are in epiphysis
- completed in early adulthood
endochondral ossification
29
What are the 6 steps of endochondral ossification?
1. **hyaline cartilage** forms initial model
2. perichondrium changes to **periosteum** (outer surface): **osteoblasts** form new bone on the surface of cartilage building an outer bony collar surrounding shaft of cartilage model, responsible for bone growth in width (**diaphyseal growth**)
3. embedded central **chondrocytes** begin **calcifying** the matrix and begin dying (starving) as **bone collar forms**
4. dying cartilage cells stimulate blood vessels to invade bringing in osteoblastic precursors \> osteoblasts, deposit bone matrix on surface of calcified cartilage forming trabecular bone covering calcified cartilage core, this is the **primary ossification center**, begins forming late in 2nd mo of dvlpmnt
5. **osteoclasts** move in and **remove** ossified **cartilage** to create marrow cavity
6. **secondary ossification centers** develop in the head (epiphysis) of long bones through same process beginning around time of birth
30
- hyaline cartilage found between the primary and secondary ossification centers
- bone lengthening is dependent on this cartilage plate
- damage to this plate (e.g. fractures) during growth will disrupt lengthening of the bone
epiphyseal growth plate
31
What are the different zones within an epiphyseal growth plate?
- **resting zone (reserved cartilage zone)**
- **proliferation zone**: chondrocytes within plate undergo mitosis and increase cell numbers forming stacks of chondrocytes (FGFR3 plays key role in maintaining chondrocyte proliferation, autosomal mutations in this receptor are responsible for achondroplasia)
- **hypertrophic zone**: chondrocytes deposit ECM spreading them apart while they increase in size (interstitial growth), initiate vascular invasion of cartilage, pushing the epiphysis away from diaphysis and lengthening the bone
- **calcification zone**: cartilage cells calcify surrounding matrix and die
- **ossification zone:** invading BV's bring in osteoprogenitor cells that differentiate into osteoblasts and cover hardened cartilage w/ woven bone matrix
(eventually osteoclasts remove ossified cartilage and osteoblasts replace w/ **trabecular bone**, **bony collar** of long bone is also added on periphery by **appositional growth** on the outer surface of long bone)
32
What is the mechanical regulation of bone? (bone design)
- anatomy of bone reflects stresses
- bone adapts to force placed on it
- fracture resistant
- exercise increases bone mass; prolonged bed rest or disuse results in bone loss (osteopenia/osteoporosis)
33
How does bone growth in diameter occur?
- occurs via osteoblasts in the periosteum
- begins w/ formation of bone collar on the cartilaginous diaphysis
- accompanied by enlargement of the marrow cavity by activity of osteoclasts in the endosteum
34
- autosomal dominant syndrome
- mutation in FGFR3 (important mediator of chondroblast proliferation)
- most common form of dwarfism
- shortening of long bones
- small midface (defects in cranial base)
- altered spinal curvature
achondroplasia
35
- process that **repairs bone microdamage**
- also provides **calcium metabolism** (500 mg of calcium may enter or leave skeleton each day)
- coupled activity: resorption by osteoclasts (**removal**) followed by formation of ostseoblasts (**replacement**), these two must be linked to maintain bone density
- responsible for the **concentric lamellar orientation** of osteons and for the interlamellar portions (partially removed osteons remaining from previous remodeling events)
bone remodeling
36
- type of bone remodeling
- this type of bone is replaced every 3-4 years
- osteoclasts remove (resorb) bone matrix and signal osteoblasts to come in
- osteoblast depost fresh new bone
trabecular bone remodeling
37
- type of bone remodeling
- occurs every 10 years
- old osteons are resorbed by osteoclasts, creating tunnels and signaling for BV's
- osteoprogenitors invade tunnels \> osteoblasts \> secrete osteoid
- new osteon forms w/ concentric lamellae and trapped osteocytes
- interstitial lamellae remain
compact bone remodeling
38
What are the 4 steps of bone fracture repair?
1. **fracture hematoma forms**: torn BV's w/in fracture release blood \> clots and produces the hematoma
2. **fibrocartilaginous (soft) callus forms**: hematoma removed by macros \> replaced by fibrocartilage-like mass (soft callus) within 2-3 weeks; if torn, periosteum reestablishes continuity over soft callus
3. **hard (bony) callus forms**: procallus invaded by BV's and osteoblasts; fibrocartilage is replaced by woven bone \> forms hard callus within 2 months
4. **bone is remodeled**: woven bone is remodeled as compact/cancellous bone; vasculature is reestablished
39
- bone disorder of low bone mass
- cause: bone resorption is faster than bone deposition
- 30% of caucasian women will experience bone fracture due to this condition
- occurs most often in women after menopause, but also occurs in elderly
- risk factors: strong genetic component, poor diet, insufficient exercise to stress bones, inadequate calcium in diet, insufficient vitamin D
- estrogen deficiency also a risk factor; estrogen therapy used as prevention, however it causes increased risk of CV dz and BrCa, thus its use is controversial
osteoporosis
40
- vitamin D deficiency in adults
- vit D required for calcium absorption
- bones are inadequately mineralized and are soft
osteomalacia
41
- vit D deficiency in children
- analagous to osteomalacia but is more severe
- weakened long bones, abnormal head and rib cage
rickets
