Histology Flashcards
What are characteristics of hyaline cartilage?
Characterized by matrix containing:
Type II Collagen
Glycosaminoglycans (GAGs)
Proteoglycans
Multiadhesive glycoproteins
Where is hyaline cartilage found?
Articular surface of joints
respiratory passages
precursor to bones during development
What are chondrocytes?
Cells that forme the cartilage matrix, they are surrounded by lacunae
What are osteoblasts?
Cells that secrete the extracellular matrix of bone;
once the cell is surrounded with its secreted matrix, it is reffered to as an osteocyte
What are osteoclasts?
boen-resorbign cells present on bone surfaces where bone is being removed or remodeled
or where bone has been damaged
Is of granulocyte/monocyte lineage (not the same lineage as osteoblasts)
What are lamellae?
They appear on mature bone and make op osteons.
They are bone matrix surrounding a central (Haversian) canal
What are interstitial lamellae?
Remnants of previous concentric lamellae
What are circumferential lamellae?
Follow the entire inner and outer circumferences of the shaft of long bone
What are canaliculi?
Small tunnels that course through mineralized matrix, connecting adjacent lacunae and allowing contact between the cell processes of neighboring osteocytes
What is an osteon?
Cylindrical units that compose the majority of mature bone
They contain lamellae, lacunae, and the encompassed osteocyte
What is an osteoid?
unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue
What is the periosteum?
Covering of an actively growing bone that consists of:
outer fibrous layer that resembles other dense connective tissues
inner, more cellular layer that contains osteoprogenitor cells
What is the endosteum?
The lining tissue of both the compact bone facing the marrow cavity and the trabeculae of spongy bone within the cavity
What is the trabeculae?
Thin, anastomosing spicules of bone tissue that make up the spongelike meshwork of spongy bone
What is articular cartilage?
Hyaline cartilage covering the articular surfaces of movable joints
(does not have a perichondrium)
What is appositional growth?
The process that forms new cartilage at the surface of an existing cartilage
What is interstitial growth?
The process that forms new cartilage within an existing cartilage mass
What are isogenous groups?
Clusters of chondrocytes produced by proliferation of chondrocytes
What is endochondral ossification?
Production of bone with a cartilage precursor
What is intramembranous ossification?
Formation of bone by differentiation of mesenchymal cells into osteoblasts
What is the process of intramembranous ossification?
- Mesenchymal cells migrate and aggregate at the site of bone formation
- Mesenchymal cells differentiate into osteoprogenitor cells
- further differentiating to osteoblasts that secret collagens (mainly Type I) and other bone matrix proteins developing the bone through appositional growth
- In time, the matrix becomes calcified the bone-forming cells, now osteocytes, are contained within canaliculi
What is the process of endhochondral ossification?
- Also begins with migration and proliferation of mesenchymal cells at site of future bone, but initially, hyaline cartilage is formed
- The cartilage grows through interstitial and appositional growth
- Perichondrial cells at midregion begin to produce osteoblasts, producing an osteogenic layer and a distinctive cuff of periosteal bone (bony collar)
- midregion chondrocytes become hypertrophic and undergo calcification (not to be confused with mineralization that occurs in bone tissue)
- Calcified cartilage matrix inhibits diffusion of nutrients, killing chondrocytes
- Mesenchymal and hemopoietic stem cells from periosteum migrate along penetrating blood vessels and differentiate into osteoprogenitor cells and bone marrow in bone marrow cavity.
- Osteoprogenitor cells come in apposition with remaining calcified cartilage spicules, become osteoblasts and begin ossification of the bone framework
Where does growth of endochondral bone occur after primary ossification?
in the presence of epiphyseal cartilage at epiphyseal growth plates
What are the zones of endochondral bone formation?
The zones of epiphyseal cartilage are:
Resting
Proliferative
Hypertophy
Calcification
Ossification
What is a Haversian canal?
Central canals in the bone matrix that contain vascular and nerve supply of the osteon
What is a Volkmann’s canal?
Perforating canals that are channels in lamellar bone through which blood vessels and nerves travel from the periosteal and endosteal surfaces to reach the osteonal canal
What is Howship’s lacunae?
Shallow resorption bays observed in the bone directly under osteoclasts
What are Sharpey’s fibers?
In areas where ligaments and tendons attach to the bone, Sharpey’s fibers are collagen fibers from these structures that extend directly, but at an angle, into the bone tissue
What is an epiphyseal closure?
Elimination of the epiphyseal plate after individual achieves maximal growth
What is synarthrosis?
A joint that allows little to no movement under normal conditions
What is osteomalacia?
A softening of bones, generally caused by a lack of Vitamin D
What is rickets?
Calcium deficiency during growth, leads to bone matrix not able to calcify normally
May be caused by insufficient vitamin D, which can also lead to osteomalacia in adults
What is scurvy?
Vitamin C deficiency in which matrix produced in scurvy is not calcifiable
Cartilage is unable to undergo hydroxylation
