Lecture 1: Intro to bone and soft tissue Flashcards
What 3 components is the musculoskeletal system composed of?
- bone
- muscle
- connective tissue
What types of connective tissue are there within the musculoskeletal system?
- tendon
- ligaments
- cartilage
What is a tendon?
connects muscle to bone
What is a ligament?
connects bone to bone
What is cartilage?
component for:
- structural support
- protection of tissues
- attachment sites
How many bones are in the human skeleton?
206 (+sesamoids), 270 in children
What is included in the appendicular skeleton?
pectoral girdle, upper and lower limbs, pelvic girdle
What is included in the axial skeleton?
cranium, vertebral column, rib cage
What are the 5 functions of the skeletal system?
- movement
- support
- protection of vital organs
- calcium storage
- haematopoiesis
How are bones classified by shape?
- flat bone
- sutured bone
- short bone
- irregular bone
- sesamoid bone (e.g. patella)
- long bone
What are the 4 types of bone cells?
- osteogenic cell
- osteoblast
- osteocyte
- osteoclast
What is an osteogenic cell?
bone ‘stem cell’
What is an osteoblast?
- ‘bone forming’
- secretes ‘osteoid’
- catalyse mineralisation of osteoid
What is an osteocyte?
- mature bone cell
- resting bone cell
- formed when an osteoblast becomes embedded in its secretions
- sense mechanical strain to direct osteoclast and osteoblast activity
What is an osteoclast?
- ‘bone breaking’
- dissolve and resorb bone by phagocytosis
- derived from bone marrow
- remodel bone
Where is each type of bone cell found?
Osteocytes - embedded in matrix
Osteoclasts - bone surfaces, at sites of old, injured or unneeded bone
Osteogenic cells - deep layers of periosteum
Osteoblasts - growing portions of bone, including periosteum and endosteum
Outline the composition of bone matrix.
40% = organic component (mainly Type 1 collagen, w/mainly ground substance - proteoglycans, glycoproteins, cytokine + growth factors) 60% = inorganic component (calcium hydroxyapatite and osteocalcium phosphate)
Outline 2 main bone types
IMMATURE BONE - is first bone produced that is laid down in ‘woven’ manner, and relatively weak
MATURE BONE - is mineralised woven bone with Lamellar (layer) structure - relatively strong
What 2 types of mature bone are there?
CORTICAL - dense + compact, suitable for weight bearing + very strong
CANCELLOUS - spongy, honeycomb structure, not suitable for weight-bearing
Outline what compact bone provides
Compact bone has few spaces, provides protection, support and resists stresses produced by weight of movement.
Outline organisation of bone?
Made of repeated structural units called ‘osteons’ - have concentric lamellae around central Haversian canal
What is the Haversian canal?
central canal in osteons that contains blood vessels, nerves and lymphatics
What are Lacunae?
small spaces containing osteocytes. Tiny canaliculi radiate from lacunae filled with extracellular fluid
What is the Volkmans canal?
transverse perforating canals
What are the 2 main parts of a long bone?
The DIAPHYSIS - the tubular shaft that runs between the proximal and distal ends of the bone
The EPIPHYSIS - wider section at the end of each bone, which is filled with spongy bone
What is the hollow region in the diaphysis called and what is it filled with?
medullary cavity - filled with yellow bone marrow
What are the walls of the diaphysis composed of?
dense and hard compact bone
Where does each epiphysis meet the diaphysis?
at the METAPHYSIS - the narrow area that contains the epiphyseal plate (growth plate - layer of hyaline cartilage in growing bone)
What is intramembranous ossification?
- bone development from fibrous membranes
- forms flat bones of skull, clavicle and mandible
- mesenchymal cell template
- bone forms within flat sheets
What is endochondral ossification?
- development of long bone from hyaline cartilage model
- cartilage precursor forms calcified bone
- takes longer than intramembranous ossification
- primary ossification centre = diaphysis
- secondary ossification centre = epiphysis
What is interstitial growth? (epiphyseal plate facts)
- long bone lengthening
Epiphyseal plate: - zone of elongation in long bone
- contains hyaline cartilage
- epiphyseal side - hyaline cartilage active and dividing to form hyaline cartilage matrix
- diaphyseal side - cartilage calcifies and dies and then replaced by bone
What is appositional growth?
deposition of bone beneath periosteum to increase thickness
- ridges in periosteum create groove for periosteal blood vessel
- periosteal ridges fuse, forming an endosteum-lined tunnel
- osteoblasts in endosteum build new concentric lamellae inward toward centre of tunnel, forming new osteon
- bone grows outwards as osteoblasts in periosteum build new circumferential lamellae - osteon formation repeats as new periosteal ridges fold over blood vessel
What is the role of bone in calcium homeostasis?
If there is less Ca2+ in blood then PTH stimulates bone resorption which increases Ca mobilisation, which increases plasma Ca
If too much Ca2+ in blood then calcitonin decreases osteoclast activity
Main facts about tendons?
- attaches skeletal muscle to bone
- transmit muscle force to bone
- made of collagen fibres
- stiff and strong
What is the microstructure of tendons?
Parallel arrays of collagen fibres closely packed together
- mainly collagen, very little elastin, proteoglycans and inorganic components e.g. Cu, Mn, and Ca
What is the function of tendons?
- transmit muscle forces
- elastic energy storage/recoil
- PG resists compressive stresses
Main facts about collagen?
- most abundant protein in human body
- molecule is long, rigid structure
- 3 polypeptides (referred to as alpha-chains) wound around one another
- rope-like triple helix
- crimping of fibres
- non elastic behaviour
- fibre component of connective tissue
3 types of relevant collagen and locations?
TYPE I - skin, tendon, ligaments and bone
TYPE II - cartilage, vitreous body, nucleus pulposus
TYPE III - skin, vessel wall, reticular fibre of most tissues (lungs, liver, spleen)
Main facts about ligaments?
- connect bone to bone to stabilise joint
- enable proprioception
- have functional subunits that tighten or loosen depending on joint position
- is not densely innervated or vascularised
- contain some blood vessels + nerves in outer covering (epiligament)
- contain proprioreceptors
- transmit pain signals via type C fibres
What does a normal ligament consist of?
- 90% Type I collagen (strong)
- 9% Type III collagen (immature, greater proportion in healing tissue)
- 1% fibroblast cells (cells that produce collagen)
Facts about cartilage?
- acts as shock absorber to reduce friction
- covers and protects long bones at joints
- structural component of ribs and IV discs
- made up of chondrocytes (produce large amounts of collagenous ECM, ground substance)
- 3 types
- avascular and worn down in osteoarthritis
What are the 3 types of cartilage?
- elastic
- hyaline (shiny surface of bone)
- fibrocartilage (shock-absorbing)
3 classifications of joints
- fibrous (synarthrosis): sutures, syndesmosis, interosseus membrane
- cartilaginous (amphiarthrosis): synchondroses, symphyses
- synovial (diarthrosis): plane, hinge, condyloid, pivot, saddle, ball + socket
What is the most common and most mobile type of joint?
Synovial joints
What does synovial fluid do?
Reduce friction during movement
2 parts of joint capsule of synovial joints?
Articular capsule (outer) - keeps bones together structurally Synovial membrane (inner) - contains synovial fluid
What do ligaments prevent?
Prevent excessive movement that could damage joint
More ligaments + tighter ligaments leads to…?
Greater stability but less mobility
Less ligaments + laxer ligaments leads to…?
Greater mobility but less stability
Factors affecting joint stability?
- joint shape
- ligaments
- tendons
- cartilage
