CH 4 Cartilage & Bone

What are the three types of cartilage?

Hyaline, elastic, and fibrocartilage.

What distinguishes hyaline cartilage histologically?

Type II collagen, smooth basophilic matrix, isogenic groups in lacunae.

What distinguishes elastic cartilage histologically?

Type II collagen + elastic fibers; more abundant chondrocytes; found in pinna and epiglottis.

What distinguishes fibrocartilage histologically?

Type I collagen; no perichondrium; chondrocytes aligned in rows with dense fibers.

What are the functions of bone aside from support?

Stores minerals (e.g., calcium), provides levers for movement, protects organs, and houses blood-producing bone marrow.

What are two methods to view bone histologically?

Decalcified sections and ground sections.

What is the difference between decalcified and ground bone sections?

Decalcified shows cells and soft matrix; ground retains minerals but no cells.

What are the two methods of bone ossification?

Intramembranous and endochondral ossification.

What bones are formed by intramembranous ossification?

Flat bones like skull and clavicle.

How does intramembranous ossification occur?

Mesenchymal cells differentiate into osteoblasts that form bone matrix directly.

What bones are formed by endochondral ossification?

Long bones like femur, humerus.

How does endochondral ossification occur?

Cartilage template forms first, then is replaced by bone through vascular invasion and remodeling.

What does an osteoclast do?

Resorbs bone matrix by releasing enzymes and acids.

What are the zones of an active osteoclast?

Basal zone, clear zone, vesicular zone, and ruffled border.

Where are osteoclasts derived from?

Granulocyte-macrophage progenitor cells (GM-CFU) from bone marrow.

How does bone grow in length?

Through the epiphyseal plate, with chondrocyte proliferation and ossification.

What are the zones of epiphyseal plate growth?

Reserve cartilage, proliferation, hypertrophy, calcification, ossification.

How does bone grow in width?

Appositional growth via periosteal osteoprogenitor cells laying new matrix.

What are osteoprogenitor cells?

Stem cells that differentiate into osteoblasts; found in periosteum and endosteum.

What are osteoblasts?

Bone-forming cells that secrete matrix proteins like osteocalcin and osteopontin.

What are osteocytes?

Mature bone cells trapped in lacunae; maintain bone and communicate via canaliculi.

What is the role of the ruffled border in osteoclasts?

It increases surface area for bone resorption.

What inhibits osteoclasts?

Calcitonin.

What stimulates osteoclast formation?

MCSF, RANKL interaction from osteoblasts.

What is the perichondrium?

Connective tissue sheath around cartilage (absent in fibrocartilage).

What is the endosteum?

A cellular layer lining bone cavities; contains osteoprogenitor cells and osteoblasts.

What are the inorganic and organic components of bone?

Inorganic: hydroxyapatite (Ca, PO4); Organic: type I collagen, proteoglycans.

What is an isogenous group?

A cluster of chondrocytes that originated from a single chondroblast through mitosis; found within a single lacuna.

What is interstitial growth in cartilage?

Growth from within the cartilage as chondrocytes divide and secrete new matrix inside the tissue.

What is a Volkmann's canal?

A transverse or diagonal canal in bone that connects adjacent Haversian canals; allows vascular and nerve communication.

What is a cementing line in bone?

The outermost boundary of an osteon; marks the limit of bone remodeling and separates osteons from interstitial lamellae.

What are Sharpey's fibers?

Collagen fibers that anchor the periosteum to the underlying bone; also help attach tendons and ligaments to bone.