Bones, joints and cartilage Flashcards
Muscoskeletal system comprised of
Skeleton, muscles and accessory tissues which together allow locomotion and articulation
ie bone, cartilage, joints, ligaments, tendons, nerve fibres and BVs
2 main tissue types the skeleton is made up of
bone and cartilage
Bone 2 types
compact (exterior) and trabecular (interior)
bone shapes
long, short, flat (slightly curved and irregular
bone is encased with
fibrous periosteum (blood supply and nutrients)
3 main types of cartilage
hyaline, fibro and elastic
cartilage is sometimes encased within
fibrous perichondrium
Hyaline
growth plate, joint surfaces and temporary scaffold
nose, ribs and larynx
Fibrocartilage
invertebral discs, menisci (pads) in joint spaces
no perichodrium
Found in areas which must withstand lots of pressure
elastic cartilage
external ear, epiglottis and larynx
stretchy
bone functions
support, protection, attachment (locomotion), store minerals
Haematopopoiesis- produces RBCs
Lipid storage
Bone water content
low
Bone is made up of
minerals
type I collagen
proteoglycans/glycoproteins
cell types in bones
osteoblasts (form bones)
osteocytes (abundant)
osteoclasts (bone resorbing)
Cartilage function
template for bone formation, growth of long bones, smooth, articulating joint surface
water content in cartilage
high
Cartilage is made up of
type II collagen
Proteoglycans
Glycosaminoglycans
Glycoproteins
Cell types in cartilage
chrondoblasts
chrondocytes
Axial skeleton
bones of the skull, vertebral column and ribs
Appendicular skeleton
bones of limbs, pelvis, scapula and clavicle
Short bones
support and stability, little to no movement
cube like
hands and feet
Flat bones
thin and flat
Can be a bit curved
Points of attachment for muscle or protect internal organs
Irregular bones
don’t fit other categories
Complex shape eg bones in the face
Long bone
located in the appendicular skeleton
anatomy of a long bone
includes diaphysis, epiphysis, spongy bone, epiphyseal line, metaphysis, fatty tissue, periosteum
Diaphysis
shaft of long bone
Epiphysis
at each end. Proximal and distal
spongy bone
found in the epiphysis. Contains bone marrow for rbcs
Epiphyseal plate/line
depending on stage of development
Becomes line when fully developed
Marks where proximal epiphysis starts
Metaphysis
contains the medullary cavity which is the hollowed out core of the bone
Fatty tissue
energy store
aka yellow marrow
Periosteum
outside the bone
membrane
endosteum
lining inside of medullary cavity
both membranes
Whats at the end of the bone
articular cartilage
Allows joints to move smoothly
Microanatomy of a long bone
basic functional unit of long bone is the osteon
Rings around it referred to as concentric lamellae- made up of layers of osteocytes
Canal in the centre where blood vessel is located
Orientation of the lamellae run in opposite directions i each layer to give bone ability to withstand impact
Central canal
runs parallel to osteon
Perforating canal
runs perpendicular to osteon
cannaliculi
holds together osteocytes in the lacuna
Deliver nutrients and oxygen to osteocytes
Trabecular (spongy) bone
here the bone isn’t solid, instead filled with holes connected by thin rods/plates of bone tissue
Trabeculae have no blood vessels or central canal
Contains lamella like osteon, but lamella are parallel
Matrix inside which contains the lacuna which contains osteocytes
Space for red bone marrow between trabeculae
SPongy bone has no central canal, so obtains nutrients through pores in the bone surface
Osteogenic cells
undifferentiated
HIgh mitotic activity
In periostium and bone marrow
GIve rise to osteoblasts
Osteoblasts
Found in periostium and endostium
Growing portions of bone
Responsible for forming new bone
Don’t divide but synthesise and secrete organic compounds and ca salts
Osteocytes
formed from osteoblasts
Mature bone
Located in the lacuna
Maintain mineral concentration of the bone matrix
Osteoclasts
degrade bone
Cause bone resorption
They are a form of macrophage and don’t originate from osteogenic cells
bone development aka
ossification
ossification has 2 form depending on the type of bone that is formed
intramembranous ossification and endochronal ossification
skeleton develops from
The embryonic mesenchyme:
- loosely packed, unspecialised cells in a gel-like matrix
- derived from the embryonic mesoderm
Mesenchymal cells migrate and form
condensations- small clusters
Prefigure sites of bone development
Intramembranous ossification
bone forms directly within the condensation
Endochronal ossification
most bones
Cartilage template (analage )forms within the condensation The cartilage analage is subsequently replaced by bone
Intramembranous ossification process step 1
Cells come together and start aggregating and replicating, then differentiate into osteoblasts. The osteoblasts come together to form an ossification centre
Cells release osteoid (unmineralized bone)
Only happens at the middle of the ossification centre, so osteoblasts become trapped in the centre and differentiate into osteocytes
Step 2 IO
After a few days the osteoid begins to hardens and calcifies to form bone
After this the osteoid continues being deposited in a random fashion around blood vessels
step 3 IO
trabeculae form
step 4 IO
development of periosteum
Lamellae of of compact bone begins to form which replaces the trabeculae on the outside edge.
It gets deposited in layers and the spongy layer is still there
The osteoblasts stay on the outside surface of the bone- help remodel it when necessary
Endochrondal ossification step 1
Chrondocytes at center of the growing cartilage model enlarge and then die as the matrix calcifies
Step 2 EO
Stem cells divide to form osteoblasts which cover the shaft of the cartilage in a thin layer of bone
Step 3 EO
Blood vessels penetrate the cartilage and new osteoblasts form the primary ossification center
Step 4 EO
Bone of shaft thickens, and cartilage near each epiphysisis replaced by shafts of bone
Step 5 EO
Blood vessels invade the epiphyses and osteoblasts form secondary ossification centres
Secondary ossification complete: cartilage totally replaced by bone except in 2 places- surface of epiphyseal
When is IO
commences in week 6 of gestation
When is EO
occurs in the foetus after 8 weeks of development
Post natal growth in length: epiphseal plate
go over
1 new cartilage is produced on the epiphyseal side of the plate as the chrondocytes divide and form stacks of cells
As the chrondocytes divide and align in columns, the cartilage expands towards the epiphysis and the bone elongates
2 Chrondocytes mature and enlarge
3 Matrix is calcified, and chrondocytes die
4 The cartilage on the diaphyseal side of the plate is replaced by bone by osteocytes. Osteoclasts erode the old cartilage
Net result is that plate remains same in thickness, with elongation of the bone
Post natal growth in width: apposition
osteoblasts deposit new bone on the outside of the bone shaft, and the osteoclasts break down tissue from the medulla to mainatin thickness of the bone
Bone remodelling step 1
Resting step- all the lining cells that are inactive osteoblasts are attached to the bone surface. Factors like microfracture and release of certain substances eg hormones can activate the lining cells. These cells interact with receptors that trigger pre-osteoclast fusion and form multi nucleate osteoclasts
Bone remodelling step 2
Osteoclasts gather together and begin to dissolve the bone. First they dissolve the matrix (acidification) and then release lysozomal enzymes to degrade organic components of the bone
Once dissolved to the required extent, undergo apoptosis to prevent excess resorption
remodelling step 3
Reversal
Cells remove the debris produced during resorption
Release of growth factors- recruit osteoblasts
remodelling step 4
Bone formation
Once osteoblasts are generated, alkaline phosphatase is produced to help form a new bone matrix
Matrix mineralised with calcium and P to form new bone and it returns to the resting phase
Bone mass in women
Osteoclast apoptoss is regulated by oestrogen so when oestrogen levels decrease, osteoclasts can live longer and breakdown more bone
In old people
trabeculae thinner, fewer and more widely spaced
Bone regeneration: fracture healing step 1
Blood released from damaged blood vessels forms a hematoma
BR 2
internal callus forms between ends of bones and the exteral callus forms a collar around the break
BR 3
woven, spongy bone replaces the internal and external calluses
Callus ossification
BR 4
bone remodelling
Compact bone replaces woven bone, and part of the internal callus is removed, restoring medullary cavity
Joints
Occur at the joins between bones
synovial, fibrous, cartilaginous
Largest and most important are synovial
6 subtypes of synovial joint
planar hinge pivot condyloid saddle, ball and socket
Joint movement
X axis for up and down
Y for side to side
Z for 3D
Uniaxial joints
move along a single axis
Biaxial
move about 2 distinct axis
Simpified structure of a synovial joint
articular cartilage covering the ends of the bones
- smooth, lubricating surface- resists compression
Bilayered joint capsule: outer fibrous and inner elastic
- fibrous layer attaches to the periosteum of the articulating bone
- inner synovial membrane : site of production of the synovial fluid
a joint cavity filled with viscous synovial fluid
