Bone and Cartilage Histology Flashcards
Does cartilage have neurovasculature
No it receives nutrients from diffusion via surrounding capillaries
Chondroblasts
Cells that secrete cartilage matrix
Have mitotic capabilities
Chondrocytes
Mature cartilage cells in lacunae
Surrounded by and maintain matrix
Form isogenous groups
Fibers of the cartilage matrix
Type II collagen is predominant although type I may be present
Elastin fibers in elastic cartilage
Ground substance includes hyaluronic acid and chondroitin sulfate
Differentiation of cartilage cells
Takes place from the center outward
Central cells are chondrocytes
Peripheral cells are chondroblasts
Cartilage arises from what
Embryonic mesoderm
Perichondrium
Dense irregular CT covering hyaline and elastic cartilage
Lacking in fibrocartilage and articular cartilage
Arises from mesenchyme
Outer/fibrous layer of perichondrium
Largely type I collagen and fibroblasts
Inner/chondrogenic layer of perichondrium
Adjoins cartilage matrix, contains mesenchymal stem cells
Source for new chondroblasts to divide/differentiate into chondrocytes
Hyaline cartilage
Found on articular surfaces of synovial joints, larger respiratory passages, costal cartilages and epiphyseal plates of long bones, portions of embryonic skeleton
Surrounded by perichondrium
Territorial matrix of hyaline cartilage
Immediately surrounds each chondrocyte
ECM consists of type II collagen
High GAGs
Staining is more basophilic
Interterritorial matrix of hyaline cartilage
Surrounds territorial matrix
More collagen II, fewer proteoglycans
Staining is less basophilic
Elastic cartilage
Similar to hyaline but contains elastic fibers embedded in type II collagen
Elastic fibers appear dark with orcein or resorcin-fuchsin stains
Found in auricle of ear, walls of EAC, eustachian tubes, epiglottis
Fibrocartilage
Mix of hyaline cartilage and dense CT
Lacks perichondrium
Tough, yet cushioning support tissue for bone
Found in intervertebral discs, pubic symphysis, and selected joint capsules
Sparse type II collagen, with fibroblasts and dense bundles of type I collagen
Interstitial vs appositional growth
Interstitial- mitotic division of pre-existing chondrocytes in lacunae
Appositional- chondroblast differentiation from progenitor cells in the perichondrium
Damaged cartilage undergoes slow and incomplete repair except in young children
-due to avascularity and low metabolic rate
Osteoblasts
Produce osteoid, initiate and control mineralization of osteoid
Located along edges of bone and/or matrix, near periosteum or endosteum
Located near mesenchyme in developing bone
Osteoclasts
Multi-nucleated cells
Ruffled border which reabsorbs bone through H+ and lysosomal protein
Typically located along edges of bone for digestion/remodeling purposes
Osteocytes
Mature bone cells in lacunae, maintain bone matrix
Communicate with osteoblasts to increase deposition of bone matrix
Extend long, spider-like processes
Typically centrally located, embedded in lacunae but extend processes in canaliculi
Compact bone
Encloses cancellous bone
Lamellar (mature) bone
Cancellous/spongy bone
Trabeculae
Porous to house bone marrow
Parallel bundles of collagen in thin layers, with regularly spaced cells in between
Can be lamellar (mature) or woven (immature) bone
Woven bone
Usually replaced by lamellar bone
Characterized by loose, random arrangement of collagen, low cell count
Forms during fracture repair and remodeling
Epiphysis
Knobby regions at ends of bone
Compact bone is superficial, with spongy 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
Endosteum
CT lining of all trabeculae and marrow cavity
Contains osteoprogenitor cells, reticular cells of bone marrow, CT fibers
Periosteum
Dense irregular CT covering external surface of bone
Does not cover articular cartilages
Neurovascular
Anchored by perforating fibers embedded in matrix
Contains osteoblasts
Spongy bone tissue
Arranged as trabeculae, open lattice of narrow lamellar plates
Most easily seen in bones of the skull
Oriented in positions that maximize strength while minimizing mass
Houses bone marrow
Endochondral ossification
Pre-existing hyaline cartilage is eroded and evaded by osteoblasts, beginning osteoid production
Happens in bones of extremities, pectoral/pelvic girdles
Pelvis, vertebrae, ends of clavicles
Intramembranous ossification
Osteoblasts differentiate directly from mesenchyme and begin secreting osteoid
Flat bones of skull, facial bones, mandible, central part of clavicle
What is similar b/w intramembranous and endochondral ossification
Woven bone is produced first and then replaced by lamellar bone
Zone of proliferation
Cartilage cells undergo division and secrete collagen
Zone of hypertrophy
Greatly enlarged chondrocytes
Secrete factors that initiate vascular invasion
Zone of ossification/resorption
Nearest the diaphysis
Calcified cartilage is in direct contact with marrow cavity
Blood vessels and osteoprogenitors invade the region
Osteoprogenitors differentiate into osteoblasts
Achondroplasia
Autosomal dominant syndrome, mutation in FGFR3 Most common form of dwarfism Shortening of long bones Small midface Altered spinal curvature
Appositional growth
Growth in circumference of long bones via osteoblasts in periosteum
Accompanied by enlargement of marrow cavity by activity of osteoclasts in endosteum
Rickets
Calcium deficiency in children
Bone matrix does not calcify normally and the epiphyseal plate can become distorted by normal strains of body wait and muscular activity
Bones grow slowly and become deformed
Widening of wrist and bowing of distal radius/ulna and femur/tibia
Can also be caused by failure to produce Vitamin D
Osteomalacia
Deficient calcification of recently formed bone and partial decalcification of already calcified matrix
Vitamin D deficiency, lack of sun, GI disease
Can be asymptomatic
Bone fracture repair
Torn blood vessels release blood and produce fracture hematoma
Hematoma removed by macrophages, replaced by fibrocartilage mass called pro-callus, which is then invaded by vessels and osteoblasts
Fibrocartilage replaced by woven bone forming hard callus which eventually becomes compact/cancellous bone
Osteoporosis
Decrease in bone mass and increased fragility
Loses ability to produce organic matrix (collagen)
Commonly occurs in elderly and postmenopausal females
Synovial membrane
Lines joint cavity, except articular cartilage
Vascular CT membrane
Regenerative properties
Absorbs shock
Articular cartilage
Reduces friction, avascular, no nerve supply
Hyaline cartilage without perichondrium
Collagen fibers run perpendicular to the tissue surface, but bend gradually to form an arc
Superficial vs intermediate vs deep vs calcified zones
Superficial- elongated and flattened chondrocytes
Intermediate- round chondrocytes
Deep- chondrocytes arranged in short columns
Calcified- small chondrocytes surrounded by calcified matrix, borders subchondral bone
Tidemark
Separates calcified zone from subchondral bone
Osteoarthritis
Degenerative joint disease
Related to aging and injury of articular cartilage
Various degrees of joint deformity and destruction
Commonly affects weight bearing joints
Early stage- superficial layer of articular cartilage affected
Late stage- destruction of cartilage extends to the bone, where the exposed subchondral bone becomes new articular surface
