Histology - Cartilage + Bone

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Connective tissue w/rigid extracellular matrix Chondrocytes (cells) with low metabolic activity Collagenous (tensile strength) and elastic fibers Chondroitin sulfate...
From where does cartilage develop?
Cartilage development/growth
Develops from mesenchyme Chondroblasts for collagen fibrils Differentiation of cells to chondrocytes and separation by the matrix Perichondrium envelops cartilage Interstitial growth Appositional growth
Sheath of dense irregular connective tissue – with fibroblasts and vasculature, envelops cartilage Contains many undifferentiated cells which can differentiate into...
Interstitial growth
Mitotic division of existing chondrocytes and production of new matrix (young cartilage)
Appositional growth
Differentiation of new chondrocytes from stem cells (inner layer of perichondrium) and production of matrix at surface
Name the 3 forms of cartilage
Hyaline Elastic Fibrocartilage
Hyaline (glass) cartilage
Most common Type II collagen Appears blue/white In embryo: serves as skeleton until replaced by bone – acts as a template Epiphyseal plate in long bone growth Joint surfaces,...
Hyaline cartilage matrix
Amorphous ground substance with proteoglycans – including chondroitin sulfate and kertain sulfate Basophilic Collagen fibers (20 nm) are very fine, appear structureless Territorial matrix...
Hyaline cartilage chondrocytes
Chondrocytes occupy small cavities in matrix (lacunae) Surface of cell irregular; holds onto matrix + allows for better nutrition Chondrocytes = basophilic – large...
name the two kinds of bone growth
intramembranous ossificationendochondrial ossification
Small cavities in cartilage/bone matrix
Isogenous group / cell nests
Deeper round chondrocytes grouped – up to 8 cells – all offspring from same chondrocyte
Elastic cartilage
Support w/flexibility Auricle of ear, external auditory canal, Eustachian tube, epiglottis, cuneiform cartilage of larynx Similar to hyaline cartilage – many elastic...
Tough support + tensile strength Intervertebral disks, tendon and ligament attachment to bone, pubic symphysis Combination of hyaline cartilage and dense regular connective...
Trabecular / cancellous /spongy bone
Slender irregular bars and sheets of bone, trabeculae, which branch and intersect to form a sponge-like network which is filled with bone marrow Ends of long bones (epiphyses)...
Compact bone
No spaces or hollow space visible to the eye Thick-walled tube of the shaft (diaphysis) of long bones, surrounds the marrow cavity (medullary cavity) Thin layer of...
Haversian canals
Individual lamellae form concentric rings around larger longitudinal canals (50 micrometers in diameter) formed around blood vessels Contains one or two capillaries and...
Haversian canals and surrounding lamellae
Volkmann’s (perforating) canals
From peristeal surfaces, Haversian canals enter the bone perpendicular to its long axis Communicate with Haversian canals Contain: endosteum, blood vessels, nerves
Interstitial lamellae
Remnants of Haversian systems that have been partially destroyed Fills intervals between functional Haversian systems
Name the 2 lamella which run parallel to inner and outer surface of the bone, immediately beneath the periosteum and endosteum
1- Circumferential lamellae 2- Endosteal lamellae
Formation of compact bone
Osteoblasts produce lamellae of bone matrix inward on the surface of longitudinal cavities Cavities reduced to narrow canals containing blood vessels – called “primitive...
Intramembranous ossification
type of BONE GROWTH Primitive connective tissues layer that becomes vascularized Cells differentiate into osetoblasts – which enlarge the connective tissue fiber (osteoid) Osteoblasts deposit...
Endochondral ossification
type of BONE GROWTH transformation of cartilage (bone model) to osseous tissue periosteal bud invades cartilage model and allows osteoprogenitor cells to enter cartilage. Cartilage...
epiphyseal plate
between the diaphysis and the epiphyses – a thin sheet of cartilage is maintained until adulthood. It continues cartilage production and thereby provides the basis for rapid...
periosteal collar
consists of a thin sheet of woven bone deposited around shaft of the cartilage model formed during endochondral ossification
Decalcification of bone – tissue preparation
Cellular and organic components preserved and inorganic components removed by acid Then embedded, sectioned, stained Cells appear shrunken and matrix blurred
Ground bone – tissue preparation
Grining thin piece of bone with abrasives Matrix well preserved but cells are removes
Layer of dense connective tissue Covers all bones except over articular surfaces
Thin layer of cell-rich connective tissue Lines the surface of marrow cavity/spaces
Osteoprogenitor cells
Stem cells of bone Located in periosteum and endosteum Hard to distinguish from surrounding connective tissue cells Differentiate into bone cells
What components are responsible for bone’s hardness?
Cells (osteocytes) and intercellular matrix which contains organic compounds (collagen fibers) and inorganic components (calcium phosphate, calcium carbonate)
Lamellar structure
Bone matrix organized in layers
Cavities which contain cells
Radiating from each lacuna, narrow channels that penetrate adjacent lamellae
Associated with bone formation Small cuboidal or pyramidal cells, form continuous layer Large nucleus, basophilic cytoplasm (ribosome, protein formation) Found adjacent...
Collagen fibers
Within lamellae Run parallel and oblique in adjacent lamellae
Small inactive cells Isolated from each other in individual lacunae Cell processes extend out through canaliculi and provide gap-junctional contact among neighboring...
Bone-restoring cells Multinucleated (5 to 10 per section) Giant cells (up to 100 micrometers) Each one sits alone within a small hollow excavation in matrix (Howship’s...
Howship’s lacuna
small hollow excavation in matrix contains osteocytes
list the zones of cartilage at the zone of ossification that occur during endochondral ossification
reserve cartilage zone of chondrocyte proliferation zone of cartilage maturation + hypertrophy zone of cartilage calcification zone of retrogression zone of...
reserve cartilage
Farthest away from the zone of ossification looks like immature hyaline cartilage
zone of chondrocyte proliferation
longitudinal columns of mitotically active chondrocytes
zone of cartilage maturation and hypertrophy
cells and lacunae grow in size
zone of cartilage calcification
forms border between cartilage and zone of bone deposition matrix stains deeply basophilic deposition of minerals
zone of retrogression
cartilage cells die matrix destroyed and vascular primary marrow extends into spaces
zone of ossification
osteoblasts differentiate from cells in the marrow tissue and gather on calcified cartilage
zone of resorption
marrow cavities increase in size resorption of bone in diaphysis cavity forms secondary marrow cavity
bone remodeling
osteoclasts “drill” circular tunnel within existing bone matrix osteoblasts deposit new lamellae of bone matrix on the walls of these tunnels resulting in the formation...

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