Anatomy - Cartilage and Bone Tissue

Cartilage

Type of connective tissue that is firm but flexible supporting tissue

What is cartilage compose of?

Tissue fluid (60-80% water)

Properties of Cartilage

Covered with dense perichondrium that helps resist outer expansion of the cartilage when the cartilage is compressed - not innervate (no nerves) and is avascular (no blood vessels)

Cartilage cells that form the cartilage matrix and are located next to the perichondrium

Chondroblasts

Mature cartilage cells that are embedded within the extracellular matrix in a space called a cartilage lacuna

Chondrocytes

Cartilage extracellular matrix

Ground substance containing hyaluronic acid, proteoglycans, glycoproteins, and water

What makes each cartilage different?

Physical characteristics, different extracellular matrix and fiber content

Extracellular matrix - fibers

All types of cartilage include type II collagen in the matrix but in some cartilage types there is the additional elastin or type I collagen fibers

Hyaline cartilage

Great shocking absorbing properties - covers ends of adjoining bones in movable joints - most abundant - plays a key role in bone development

Elastic Cartilage

Flexible and able to tolerate repeated bending while maintaining shape - found in the ear, epiglottis, and Eustachian tube - contains many elastic fibers in extracellular matrix

Fibrocartilage

Contain thick type I and type II collagen fibers - very tough, resisting strong compression and tensional forces - intervertebral disks

Cartilage growth: Appositional growth

Chondroblasts next to the perichondrium deposit one layer of cartilage on top of another (piling on the outside)

Cartilage growth: Interstitial growth

Expanding from within the tissue. Chondrocytes within cartilage divide forming isogenous groups (nest of cells). Each cells then secretes new extracellular matrix between one another so they become increasingly separated, expanding the cartilage

Hip and Knee Osteoarthritis

Break down of hyaline cartilage form wear and tear over time or due to physical damage

Torn meniscus (fibrocartilage between femur and tibia)

Common injury in sports

Bone tissue

Rock-hard connective tissue comprised of cells embedded in a mineralized extracellular matrix

How are bones connected to muscles?

Tendons

How are bones connected to other bones?

Ligaments

Functions of bones

Support, movement, protection of underlying organs, mineral storage (99% of body's calcium), blood-cell formation

Bone cells that contain osteogenic precursors that can go on to differentiate into osteoblasts

Mesenchymal stem cells

Bones cells that form bone tissue

Osteoblast

Bones cells that are mature osteoblasts that are embedded in bone matrix which sense strain of bone and help monitor the condition of the bone tissue (control activities of osteoblasts and osteoclasts)

Osteocyte

Bone cells that remove bone tissue (bone reabsorption)

Osteoclast

Diaphysis

Main middle shaft of a long bone

Epiphysis

Rounded end of a long bone

Metaphysis

Wider portion of a long bone adjacent the growth plate

Epiphyseal plate

Hyaline cartilage plate within the metaphysis of children and adolescents (elongation of bones)

Medullary Cavity

Hollow area within long bones (marrow cavity)

Periostium/endostium

Connective tissue found on the outer surface and inner surface of hollow bones

Articular cartilage

Cap of hyaline cartilage found at ends of bones articulating with other bones

Primary and Secondary Osteogenic centers

Sites of osteogenesis (bone formation) within the cartilage of developing long bones