Introduction to Bone and Soft Tissue Flashcards
What makes up the MSK system?
Bone
muscle
connective tissue (tendon, ligaments and cartilage)
What is a joint?
a point at which 2 separate bones meet
How many bones are there in the adult human skeleton?
206 bones (+sesamoids)
How many bones are there in the a child’s human skeleton?
270 bones
What two skeletons is the human skeleton split into?
Appendicular and axial skeleton
See diagram 4/33
What does the appendicular skeleton compose of?
pectoral girdle, upper and lower limbs, pelvic girdle
What does the axial skeleton compose of?
Cranium, vertebral column, rib cage
What are the 5 functions of the skeleton?
- Support - helps you stand up
- Protection - protects vital organs
- Movement - works with muscles so you can get around
- Mineral Storage - stores Calcium and phosphate
- Produces blood cells
How do bones develop in utero?
Intramembranous (Mesenchymal cells -> bone) — flat bones
Endochondral (Mesenchymal -> cartilage -> bone) — long bones
What does intramembranous ossification form?
flat bones of skull, clavicle and mandible
How does intramembranous ossification form bone?
(Bone development from fibrous membranes)
With mesenchymal cell template
- Condensation of mesenchymal (stem) cells which differentiate into osteoblasts - ossification centre forms
- secreted osteoid traps osteoblasts which become osteocytes
- Osteoid calcifies and forms slender, needle-like structures of spongy bone called spicules, which aggregate in the form of small supporting beams or trebeculae. Trabecular matrix and periosteum forms
- (lamellar) compact bone develops superficial to cancellous bone. Crowded blood vessels condense into red bone marrow
(See diagram 7/33)
What is osteoid?
organic part of the bone, consisting of collagen fibres
What is the periosteum?
fibrous sheet that covers bone
What is woven bone characterised by?
organisation of collagen fibres and is mechanically weak
What is lamellar/compact bone?
has regular, parallel alignment of collagen in the form of sheets or lamellae and is mechanically quite strong
What does Endochondral ossification form?
long bone from a hyaline cartilage model
which takes longer, intramembranous ossification or endochondral ossification?
endochondral ossification
What is the primary ossification centre in endochondral ossification?
diaphysis
forms the centre of long bones
What is the secondary ossification centre in endochondral ossification
epiphysis
forms the end of long bones
Describe the formation of bones via endochondral ossification.
Process begins in the developing fetus.
Around the 8th week of development, chondroblasts begin secreting a cartilaginous matrix that will form the hyaline cartilage model for bone development. Chondrocytes are trapped in lacunae and a perichondrium surrounds the model.
As chondrocytes enlarge, the matrix begins to calcify and chondrocytes begin to die as nutrients cannot diffuse through the newly-formed calcified matrix.
Stem cells within the perichondrium divide to form osteoblasts and a compact bone collar is formed around the calcified cartilage shaft.
- Bone collar formation
- Cavitation
- Periosteal Bud Invasion into the core of the cartilaginous shaft, forming a primary ossification centre
- Diaphysis Elongation
- Epiphyseal Ossification
(see diagram 9/33)
What is the name of the junction between the primary and secondary ossification centres?
epiphyseal plate
this is where the growth of bones occur after birth
When are most primary ossification centres formed by?
12th week of development
What are bones made up of?
cells
matrix
What is the osteogenic cell?
bone ‘stem cell’ - precursor to all of these bone cells
What are osteoblasts?
‘bone forming’
secretes osteoid
catalyse mineralisation of osteoid
What are osteocytes?
‘mature’ bone cells
formed when an osteoblast becomes imbedded in its secretions
sense mechanical strain to direct osteoclast and osteoblast activity
What are osteoclasts?
‘bone breaking’
dissolve and resorb bone by phagocytosis
derived from bone marrow
Where do you find osteogenic cells?
deep layers of periosteum
see diagram 13/33
Where do you find osteoblasts?
growing portions of bone, including periosteum and endosteum
see diagram 13/33
Where do you find osteocytes?
entrapped in matrix
see diagram 13/33
Where do you find osteoclasts?
Bone surfaces and at sites of old, injured or unneeded bone
see diagram 13/33
What is the bone matrix made up of?
Organic component 40%
Inorganic component 60%
What is the Organic component of the bone matrix made up of?
Type 1 Collagen 90%
Ground substance 10% (Proteoglycans, glycoproteins, cytokine + growth factors)
What is the inorganic component of the bone matrix made up of?
Calcium hydroxyapatite
Osteocalcium phosphate
What are the types of bone types?
Immature bone
Mature bone
(immature/woven/disorganised bone will go to mature/well-organised bone)
What is immature bone?
first bone that is produced
laid down in a ‘woven’ manner - relatively weak
mineralised and replaced by mature bone
What is mature bone?
mineralised woven bone
lamellar (later) structure - relatively strong
What are the two types of mature bone?
Cortical
Cancellous
What is cortical bone?
compact/cortical/lamellar
dense
suitable for weight bearing
What is cancellous bone?
spongy/cancellous
honeycomb structure
not suitable for weight bearing
What are the differences between cortical and cancellous bone?
(See diagram 17/33)
