Chapter 4- Cartilage & Bone Flashcards
contents of skeletal system
- bones
- ligaments
- cartilage
- other supportive connective tissues
functions of cartilage
- support soft tissues (respiration airways cartilaginous rings keep trachea open, auricle of ear)
- articulations (smooth surfaces between bones)
- precursor model for bone growth (fetal long bones)
cartilage
- semi-rigid connective tissue
- not as strong as bone but more flexible/resilient
- mature cartilage is avascular (no blood supply)
cartilage cells
- chondroblasts: young cells, produce matrix
- chondrocytes: older cells, surrounded by matrix
- both live in small spaces called lacunae (little lakes)
types of cartilage
1) hyaline cartilage
2) elastic cartilage
3) fibrocartilage
all have similar ground substance but different types fo fibres in extracellular matrix
CT= cells= extracellular matrix
extracellular matrix= fibers+ ground substance
hyaline cartilage
- most common but weakest (glassy)
- lacks collagen
- in fetal skeleton, at ends of bones that articulate with each other, in trachea, larynx, and nose
elastic cartilage
- elastic fibres are main feature
- in epiglottis and external ear
- needs to be able to bend and snap back to original form
fibrocartilage
- densely interwoven collagen fibers contribute to durability
- in intervertebral discs, pubic symphysis, and menisci
- schock absorber, resists tension in one direction
calcification
- minerals deposited in the matrix that strengthens the bone
- main store and source of Ca++ and PO4—
bones
- living organ that contains all 4 tissue types
- mostly connective tissue
- extracellular matrix is sturdy and rigid
functions of bones
- support: framework
- protection: hard casing around organs
- anchors for movement: muscles
- hematopoiesis: blood cell product, red marrow inside bone
- storage: calcium, phosphate, fats
classification of bones
-long bones: greater length than width
-short bones: nearly equal length and width
-flat bones: thing surfaces
irregular bones: complex shapes
long bones
- have compact and spongy bone
- most common
- femur, humerus, phalanges etc.
short bones
- have compact and spongy bone
- carpals, tarsals, patella
flat bones
- have compact and spongy bone
- provide muscle attachment sites
- protects underlying structures
- skull, ribs, sternum, scapula
irregular bones
- odd shapes, do not fit into any regular category
- vertebrae, hip bones, internal skull bones
long bone anatomy
- diaphysis
- epiphysis
- metaphysis
- articula cartilage
- medullary/marrow cavity
diaphysis
elongated, usually cylindrical shaft
epiphysis
- knobby, enlarged regions at ends
- strengthen joints
- attachment site for tendons/ligament
metaphysis
- between diaphysis and epiphysis
- contains epiphyseal (growth) plate
articular cartilage
- thin layer of hyaline cartilage on epiphysis
- reduces friction between articulating bones
medullary/marrow cavity
- cylindrical space in diaphysis
- contains yellow bone marrow (fat)
bone coverings
1) periosteum
2) endosteum
periosteum
- dense irregular CT
- covers external surfaces of bones except for articular cartilage
- anchor for blood vessels and nerves
- anchored by perforating Sharpey’ fibres embedded in the bone matrix
endosteum
covers most internal surfaces of bone
bone cells
- osteoprogenitors
- osteoblasts
- osteocytes
- osteoclasts
osteoprogenitors
- stem cells
- in endosteum and periosteum
- mitotically produce more stem cells or osteoblasts
osteoblasts
- young cells
- form bone matrix
- very mitotic
osteocytes
- mature cells
- reside in lacunae
- maintain matrix and communicate with osteoblasts for further deposit of bone matrix
osteoclasts
- large
- multinucleated cells
- dissolve cartilage and bone
- release Ca++
bone matrix
1/3 organic components (osteoid): flexible, resists breaking (cells, collagen fibres, ground substance)
2/3 inorganic components: hardness (mineral salts of inorganic hydroxyapatites, which is mostly calcium phosphates)
this deposits aourd the collagen fibres in tiny crystals and hardens bone matrix
without mineral/collage
without mineral= snake bone
without collagen= brittle bone
bone tissue
- compact bone
- spongy bone
compact bone
- cortical bone
- solid and dense
- external surfaces of long and flat bones
spongy bone
- cancellous or trabecular bone
- open lattice of narrow plates: trabeculae
- internal surface of bones
compact bone organization
basic structural and functional unit of mature bone is the osteon (a.k.a. Haversian system)
- cylindrical structures
- parallel to shaft of bone
osteon components
- lamellae
- canals
- lacunae
- canaliculi
lamellae
- concentric
- circumferential
- interstitial
concentric lamellae
concentric rings of bone around central canal
circumferential lamellae
along outer edge under the periosteum
interstitial lamellae
leftover pieces of old osteons
canals
- central (Haversian) canal
- perforating (Volkmann’s) canal
central (Haversian) canal
carried blood vessels and nerves
perforating (Volkmann’s) canal
perpendicular connections to central canal with blood vessels and nerve
lacunae
small spaces in matrix that house osteocytes
canaliculi
tiny channels between lacunae allowing metabolic interactions between osteocytes
ossification
- a.k.a. osteogenesis
- the formation and development of bone
- begins by 8th week of embryonic development and continues
patterns of ossification
- intramembranous
- endochondral
intramembranous ossification
- develops from mesenchyme
- produces flat bones of skull, some facial bones, mandible, and central portion of clavicle
endochondral ossification
- begins with a hyaline cartilage model
- produces majority of bones in body
bone growth
- bone is always being remodelled
- more dense in early adulthood, less dense in older adults
types of bone growth
1) appositional: increase diameter
2) interstitial: increase length
appositional growth
bone deposited by osteoblasts and restores by osteoclasts
interstitial growth
- grow by gradual remodelling at the articular cartilages and epiphyseal plate
- superior surfaces increase cartilage volume (chondroblasts), inferior surfaces remove cartilage (osteoclasts) and replaces it with bone (osteoblasts)
- articular cartilage and epiphyseal plate remain constant thickness (equal growth & replacement rates)
- epiphyseal plate ossifies to form epiphyseal line after age 18 (bone deposition>cartilage growth)
epiphyseal plate
- cartilage, still growing
- dark gap on x-ray
epiphyseal line
- ossified bone (age 18-21)
- appears as white band on x-ray
bone fracture repair steps
1) fracture hematoma forms
2) fibrocatilaginous (soft) callus forms
3) a hard (bony) callus forms
4) bone is remodelled
bone aging
during aging bone changes in two ways
1) loses ability to produce organic matrix (collagen)
2) loses Ca++ and other bone salts
can result in osteoporosis: decrease in bone density and can result in bone fractures
