Cartilage (Ch 6) Flashcards
Structure of Cartilage
- avascular: no blood supply (get blood from diffusion)
- cell type: chondrocytes (cartilage cell) in lacunae
Functions of cartilage
- support soft tissue
- model for formations of bone
- gliding surface at articulations (joints)
- ->cartilage is NOT a soft bone
Types of cartilage
- Hyaline
- Elastic
- Fibrocartilage
Hyaline cartilage
- most common
- support, but can be somewhat manipulated
- has fibrils: tiny (almost invisible) collagen fibers
- glossy/smooth looking
- ->found at ends of long bones, respiratory structures, and in fetal skeletons
Elastic cartilage
- similar to hyaline, but LOTS of elastic fibers
- VERY resilient and flexible - tolerates repeated bending
- -> found in pinna (outer ear) and epiglottis
Fibrocartilage
- little ground substance and matrix has thick/dense collagen fibers
- resists strong compression (shock/strong pressure)
- -> found in intervertebral discs, knee joint, public symphysis
What are the types of cartilage growth?
- Interstitial Growth
2. Appositional Growth
Interstitial Growth
- chondrocytes within existing cartilage divide and secrete new matrix to LENGTHEN the skeleton
- mostly in utero
Appositional Growth
- chondroblasts in perichondrium make new cartilage tissue by secreting new matrix on the perichondrium (outside edge)
- on the outside –> widens the cartilage
What is the skeletal system?
- internal, muscles attach to and pull against it
- bones connect via joints
- considered organs because they contain different tissue types
- Axial vs. Appendicular
What makes up the axial skeleton?
skull, vertebral column, sternum, ribs
What makes up the appendicular skeleton?
pectoral/pelvic girdles, bones of upper and lower limbs
Functions of the skeletal system
- support
- protection
- movement
- hemopoiesis (blood cell production)
- energy/mineral reserves (good source of calcium)
What is bone tissue?
- denser than cartilage
- resists compression/tension = strong
- well vascularized = heal/remodel easily
- cells: osteocytes, osteoblasts, osteoclasts
- ->constantly built up/broken down (growth, strengthening, remodeling, healing, maintenance)
What is the extracellular matrix?
organic: fibers (lots of collagen), ground substance
inorganic: 65% mineral salts (calcium phosphate)
Epiphysis
ends of long bone (proximal and distal)
Diaphysis
middle portion of bone
Compact bone
aka Cortical
- more superficial
- smooth, dense, strong, rigid
- osteon is structural unit
Spongy bone
aka Trabecular
- more deep
- better at shock absorption
Periosteum
- most external surface, white tissue –> helps ligaments and tendons attach to the bones
- well supplied with nerves/blood vessels
- attached to underlying bone by collagen fibers
(ex. shin splints = tears in periosteum)
Endosteum
where osteoblasts and osteoclasts hide out, line medullary cavity
Medullary Cavity
aka bone marrow
fills diaphysis, includes RBCs
Nutrient Arteries
fed bone
Articular Cartilage
on ends of long bone
Osteons
- made up of concentric tubes called lamellae
- oriented parallel to long axis/main compression stresses
- Haversian (central) canal runs through core of each osteon and provides blood supply/nutrients/nerves
Flat, Irregular, and Short Bones
- compact bone with periosteum on outside
- spongy bone with endosteum inside
- marrow, but no marrow cavity
What is osteogenesis?
process of bone development
-begins in embryonic period –> continues thru life
What is the skeleton made of before week 8?
hyaline cartilage/mesenchyme
What the skeleton made of after week 8?
bone tissue begins to replace most cartilage
What are the types of bone ossification?
- Intramembranous Ossification
2. Endochondrial Ossification
Intramembranous Ossification
- between the two membranes
1. mesenchymal cells congregate in CT membrane
2. become osteoblasts and region is called “ossification center” (osteoid)
3. osteoblasts –> osteocytes and new bon tissue is formed
4. embryonic blood vessels grow through the region, forming “woven” bone tissue (trabeculae) - -> forms flat bones (ex. skull, clavicle)
Endochondrial Ossification
- most bones grow this way
1. skeleton begins as hyaline cartilage model
2. from primary center of ossification in diaphysis, bones begin to replace cartilage cells
3. secondary centers of ossification form in epiphysis
4. skeleton continues to grow via diffusion of cartilage cells (and bones) until maturity - ->when two centers meet = growth stops
Achondroplasia
mutation in gene on chromosome 4 inhibits cartilage proliferation in epiphyseal plates –> close too early
- truck and head = normal size, limbs = short
- autosomal dominant, most common form of dwarfism
Osteoporosis
- imbalance in normal building/degradation cycle
- mostly in post-menopausal women who don’t absorb as much calcium –> osteoclasts break bone down to release calcium from blood to bloodstream (bone = mineral reserve)
Osteoarthritis
-articular cartilage is thin and doesn’t have a good blood supply so it heals poorly –> bones rub creating bone spurs, PAIN! (periosteum is innervated)
Bone Healing
- requires both osteoblasts and osteoclasts
- osteoblasts tend to overgrow at the site and form bony callus, then osteoblasts smooth it out (strengthen bone)
What are the steps to bone healing?
- Broken blood vessels = hematoma (blood clot) –> inflammation response
- New blood vessels grow, osteoblasts form a fibrocartilaginous (soft) callus
- Trabecular (part of spongy bone) appear and join together the pieces of broken bone and new bone forms
- Bony callus is formed, osteoclasts smooth away excess tissue (replaces fibrocartilaginous callus)
