Cell Bio- Lecture #4 (Bone & Cartilage)

Axial skeleton

Supports and protects the brain & spinal cord, thoracic region, and abdominopelvic region

Appendicular skeleton

Supports the limbs and facilitates their movement

Skeletal system

Composed of bones, cartilages, ligaments, and associated connective tissues

Spongy bone (trabecular)

Bone with a latticework interior, a scaffold of interconnected supports

Compact bone

Closely-spaced layers of bone stacked to create a solid wall of osseous tissue

Diaphysis

Shaft of a long bone; has a dense wall of compact bone, surrounds the medullary cavity

Epiphysis

Widened ends of a long bone; covered by thin compact bone, filled with spongy bone

Metaphysis

Meeting of the diaphysis and epiphysis

Osseous tissue

Another name for bone

Matrix

Dense connective tissue substance filling the space between bone cells

Calcification

Deposition of calcium salts that hardens the collagen fiber framework of bone

Hydroxyapatite

Crystals formed when calcium phosphate reacts with calcium hydroxide; combines with collagen to give bone flexibility & strength

Osteogenic cells

Stem cells that replace osteoblasts

Osteoblasts

Cells that make new bone (ossification); become osteocytes

Ossification

Process of making new bone, performed by osteoblasts

Osteocytes

Cells that maintain the bone matrix, form a network with gap junctions, live in lacunae

Osteoclasts

Cells that break down bone (osteolysis), releasing minerals

Osteolysis

Breakdown of bone, performed by osteoclasts

Osteoid

Secreted bone matrix that is not yet calcified

Lacunae

Spaces where osteocytes live, surrounded by calcified matrix

Filopodia

Structures connecting osteocytes to each other, forming gap junctions

Canaliculi

Channels in calcified matrix through which filopodia pass

Osteons

Units of compact bone; rings of bone matrix surrounding a central canal with blood supply

Lamellae

Thin layers composing osteons

Haversian canal

Central canal of an osteon allowing blood vessel passage

Trabeculae

Interconnected bone filaments composing spongy bone (no internal blood supply)

Periosteum

Tough, fibrous connective tissue membrane wrapping bones; isolates bone, contributes to repair

Endosteum

Membrane covering the inner surface of compact bone and trabeculae; formed of osteogenic cells, osteoblasts, osteoclasts

Pituitary dwarfism

Deficiency in growth hormone production, leading to proportionately smaller bones

Gigantism

Excess growth hormone (often from a pituitary tumor) prior to puberty

Acromegaly

Excess growth hormone after puberty; bones grow thicker rather than longer

Osteopenia

Normal bone loss associated with age from declining hormone secretion

Osteoporosis

Severe osteopenia, where bone fragility impedes normal skeletal function

Chondroblasts

Cartilage-forming cells (analogous to osteoblasts)

Chondrocytes

Mature cartilage cells (analogous to osteocytes)

Chondroclasts

Cartilage-breakdown cells (analogous to osteoclasts)

Chondroitin sulfate

A GAG found in cartilage's proteoglycan matrix

Hyaline cartilage- extra

Most common cartilage type, found in most joints; intermediate amount of collagen

Perichondrium

Connective tissue layer surrounding cartilage (absent in fibrocartilage)

Elastic cartilage

Found in only a few places; least collagen, many elastic fibers

Fibrocartilage

Found in joints under heavy compressive load; matrix heavy in collagen fiber bundles; lacks a perichondrium

Slipped disc

Occurs when pressure forces the fibrous ring surrounding the intervertebral disc to bulge out

Herniated disc

More serious condition where the pulpy nucleus of the intervertebral disc is forced through the fibrous ring

Growth plate closure

When the epiphyseal cartilage disappears during puberty

Articular cartilage

Cartilage that remains at joints after growth plate closure

Achondroplasia

Most common form of dwarfism; deficits in converting cartilage into bone, affecting long bone development

Arthritis

General term for joint damage/inflammation

Osteoarthritis

Caused by "wear and tear" on joints from heavy usage or cumulative strain

Rheumatoid arthritis

Autoimmune disorder where the immune system attacks joint structures, causing chronic inflammation

Long Bone

Diaphysis (shaft), Epiphysis (ends), metaphysis (junction)

Bone Cells

Osteogenic (stem), Osteoblasts (build), Osteocytes (maintain lacunae, canaliculi), Osteoclasts (break down)

Osteon

Unit of compact bone (Haversian canal + lameliae)

Traeculae

Spongy bone struts

Periosteum

Outer covering

Endosteum

inner lining

Cartilage Cells

Chondroblasts- Chondrocytes (breakdown by chondroclasts)

Hyaline

Most common; joints

Fibrocartilage

Heavy compression; NO perichondrium