Introduction to bone and soft tissue (20) Flashcards
What are the 3 components of the musculoskeletal system?
- bone
- muscle
- connective tissue
What is connective tissue?
anything that links bits of the body
What is the purpose of a tendon?
connects muscle to bone
What is the purpose of ligaments?
connect bone to bone
What is the purpose of muscle?
allow movement
and give you posture
What is the purpose of cartilage?
- structural support
- protect tissues
- attachment sites
What are the functions of the skeletal system?
- movement
- support
- protection of vital organs
- calcium storage
- haematopoesis (in bone marrow)
How do we classify bones by shape?
- flat bone
- sutured bone
- short bone
- long bone
- irregular bone
- sesamoid bone
What is an osteogenic cell?
bone ‘stem cell’
What is an osteoblast?
- ‘bone forming’
- secretes osteoid
- catalyses mineralisation of osteoid
What is an osteocyte?
- ‘mature’ bone cell/’resting’
- formed by incorporation of osteoblasts into bone matrix
- sense mechanical strain to direct osteoblast and osteoclast activity
What is an osteoclast?
- ‘bone breaking’
- dissolve and resorb bone by phagocytosis
- derived from bone marrow
What cells occupy bone?
osteogenic stem cells, osteoblasts, osteocytes, and osteoclasts
Where are osteocytes found?
embedded in the matrix
Where are osteoclasts found?
bone surfaces and at sites of old, injured, or unneeded bone
Where are osteogenic cells found?
deep layers of periosteum
Where are osteoblasts found?
growing portions of bone, including periosteum and endosteum
What are the components of the bone matrix?
- 40% organic component: 90% type 1 collagen, 10% ground substance
- 60% inorganic component: calcium hydroxyapatite and osteocalcium phosphate
What is immature/ woven bone?
- first bone that is produced
- laid down in ‘woven’ manner= weak
- mineralised and replaced by mature bone
What is mature/lamellar bone?
- mineralised woven bone
- lamellar (layer) structure= strong
- cortical (outer) and cancellous (inner) components
What is cortical bone?
- type of mature bone
- compact + dense
- suitable for weight bearing
What is cancellous bone?
- type of mature bone
- spongy- honeycomb structure
- not suitable for weight bearing
- volume w/out weight
What is the structure of a long bone?
proximal epiphysis
physis (growth plate)
metaphysis
diaphysis (long bit)
What is intramembranous ossification in the uterus?
- formation of flat bones of skull, clavicle, and mandible
- bone development from fibrous membranes
- mesenchymal cell template
What are the steps in intramembranous ossification?
- condensation of mesenchymal cells, which differentiate into osteoblasts- ossification centre forms
- secreted osteoid traps osteoblasts–> become osteocytes
- trabecular matrix and periosteum form
- compact bone develops- superficial to cancellous bone + crowded blood vessels condense into red bone marrow
What is echondral ossification?
- process of forming long bones from a hyaline cartilage precursor
- NOT in flat sheets
- takes longer than intramembranous ossification
- 1y ossification centre= diaphysis
- 2y ossification centre= epiphysis
What is interstitial growth?
- long bone lengthening in the epiphyseal plate (contains hyaline cartilage)
1. growth plate zone
2. resting cell zone
3. proliferative zone
4. maturation and hypertrophy
5. calcified matrix
6. zone of ossification
What is appositional growth?
- deposition of bone beneath periosteum (outside covering) to inc. thickness (width)
1. periosteum ridges create groove for periosteal blood vessel
2. ridges fuse, forming an endosteum-lined tunnel
3. osteoblasts in endosteum build new concentric lamellae towards centre, forming a new osteon
4. 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 effect of calcitonin on osteoclast activity?
decrease osteoclast activity
so less eating up bone, so lowers plasma calcium
Where do we find type 1 collagen?
skin, tendons, ligaments and bone
Where do we find type 2 collagen?
cartilage
Where do we find type 3 collagen?
vessel walls and outside of skin
What is the microstructure of a tendon?
parallel arrangement of collagen fibres- closely packed together
- some elastin for spring
- some proteoglycans (a ground substance)
What are the functions of a tendon?
- transmit muscle forces to bone
- elastic energy storage
- proteoglycan resists compressive stresses
What are the functions of a ligament?
- connect bone to bone to stabilise joints
- contain proprioceptors- for balance
- transmit pain signals via type C fibres
What is the composition of a ligament?
- contain type 1 collagen
- also type 3
- fibroblast cells produce collagen
What are the functions of cartilage?
- shock absorber to reduce friction
- covers and protects long bones at joints
- structural component of ribs and intervertebral discs
N.B. made of chondrocytes- produce collagen
What are the 3 types of cartilage?
- elastic
- hyaline
- fibrocartilage e.g. meniscus
What are the 3 types of joints (structural classification)?
- fibrous e.g. skull
- cartilaginous e.g. spine
- synovial e.g. long bones
What is the function of synovial fluid?
- lubrication
- nutrition of joint
- hydrostatic pressure- shock absorber
What are the types of joints (functional classification)?
- ball and socket e.g. hip
- hinge e.g. elbow
- plane e.g. between tarsal bones
- condyloid e.g. between radius+carpal bones of wrist
- saddle e.g. between trapezium carpal bone+1st metacarpal
- pivot e.g. between C1+C2 vertebrae
What are synovial joints?
- most common and mobile type of joint
- joint capsule: articular capsule (outer) keeps bones together structurally…synovial membrane (inner) contains synovial fluid–> reduces friction during movement
What factors affect joint stability?
- joint shape e.g. hip vs shoulder
- ligaments
- tendons
- cartilage e.g. glenoid labrum
What is the function of ligaments?
to prevent excessive movement that could damage the joint
N.B. more + tighter ligaments–> more stable, but less mobile (vice versa)
- if joint = unstable–> risk of dislocation
- excessive ligament laxity–> hyper mobility–> greater risk of injury
What features of the shoulder joint make it more prone to dislocation than the hip joint?
- shallow socket
- weak joint capsule
- lack of strong ligaments
- greater mobility
