5.1: Introduction to the Musculoskeletal System Flashcards
What is the MSK system
(Musculoskeletal system)
The anatomical structures that allow locomotion
5 components of the MSK system
Bones
Joints - where 2 bones meet
Muscles
Tendons
Ligaments
Tendons are
Cords of strong fibrous connective tissue attaching muscle to bone
Ligaments are
Sheets of fibrous connective tissue which connect two bones
How many bones are in the human body
206 (+sesamoids)
How many bones are in a child’s body
270
Appendicular skeleton consists of
Pectoral and pelvic girdle, limbs
Axial skeleton consists of
Cranium, vertebral column, rib cage
5 functions of the skeleton
1) rigidity / support
2) movement
3) protection for internal organs (e.g. skull, rib cage)
4) mineral storage / homeostasis (e.g. regulation of calcium and phosphate)
5) bone marrow produces blood cells
Characteristics of bone
Not inert
Alive and undergoing continual change in response to external stresses
(therefore as a result of stroke bone undergoes demineralisation and osteoporosis)
Bone is composed of
Cells
Extracellular matrix : (2 branches)
organic component (osteoarthritis)
inorganic component (minerals)
2 bone cells and what they give rise to
Osteogenic cells - osteoblasts
Osteocyte - osteoclasts
Osteogenic cell characteristics
Bone ‘stem cells’
Osteoblast characteristics
“Bone forming”
Secretes ‘osteoid’
Catalyse mineralisation of osteoid
Osteocyte cell characteristics
(Formation and function)
Mature bone marrow
Forms when an osteoblast becomes imbedded in its secretions
Sense mechanical strain to direct osteoclast and osteoblast activity
Osteoclast characteristics
‘Bone breaking’
Dissolve and reabsorb bone by phagocytosis
Derived from bone marrow
Bone mineral density (BMD) is dependent upon
Balance of osteoblasts vs osteoclast activity
Osteoporosis arises as a result of
Low BMD
Osteoporosis results in
Increased risk for low-impact fractures (e.g wrist, hip,lumbar spine)
2 types of drugs used to treat osteoporosis
Drugs that :
Inhibit osteoclastic activity
Increase osteoblastic activity
Mechanisms of fracture (3)
Trauma: low energy and high energy
Stress: abnormal stresses on normal bone
Pathological: normal stresses on abnormal bone
5 scenarios of traumatic fractures
Falls
Road traffic accidents (RTA)
Assault
Sports
Crush injury
5 non-traumatic diseases affecting bone
Cancer
Osteoporosis
Endocrine/metabolic diseases
Paget’s disease
Genetic diseases
Classification of joints is based upon
Structure or function
Diseases of joints is referred to as
Arthritis
Significance of joint diseases
Impact quality of life and function
Affect ability to perform activities of daily living (ADLs)
Limit ability to work
Secondary effects on cardiovascular and metabolic systems
3 structural joint classifications
Fibrous joints
Cartilaginous joints
Synovial joints
3 functional joint classifications
Synarthroses
Amphiarthroses
Diarthroses
Characteristics of fibrous joints
No space between bones -synarthroses
(e.g. sutures in skull, syndesmosis in tibia and fibula)
Characteristics of cartilaginous joints
Joints in which bones are connected by cartilage (e.g. joints between spinal vertebrae)
-amphiarthroses
Characteristics of synovial joints
Space between adjoining bones filled with synovial fluid
- diarthroses
Characteristic of synarthroses
Allow no movement
Characteristic of amphiarthroses
Very limited movement
Characteristic of diarthroses
Free movement of joint
4 functional types of synovial joints
Hinge (e.g knee) - monoplanar
Ball and socket (e.g shoulder, hip) - multiplanar
Pivot joint (e.g cervical spine) - limited rotating movements
Condyloid / ellipsoidal joints (e.g. Wrist) - allow all types of movement except pivotal
Components of a synovial joint
2 bones, covered in articular cartilage, with a joint cavity containing synovial fluid
Characteristics of Synovium
1-3 cell deep lining containing macrophage like phagocytic cells and fibroblast-like cells producing hyaluronic acid
Type 1 collagen
Characteristics of synovial fluid
Hyaluronic acid-rich viscous fluid
Characteristics of articular cartilage
Type 2 collagen
Proteoglycan (aggrecan)
Result in cartilage being strong and resistant to compression
Function of Cartilage
Provides smooth lining at a joint to allow ends of two bones to move with minimal friction
Cartilage is composed of (2)
Chondrocytes (Specialised cells)
Extracellular matrix: water, collagen and proteoglycans (aggrecan)
Chondroitin sulphate and keratin sulphate chains - interact with hyaluronan
Blood supply to cartilage
Avascular: no blood supply, so if injured doesn’t heal well
Aggrecan is (2)
- Proteoglycan possessing many chondroitin sulphate, and keratin sulphate chains
- Characterised by ability to interact with hyaluronan (HA) to form large Proteoglycan aggregates
Two broad divisions of arthritis
Non-inflammatory : Osteoarthritis
inflammatory
Osteoarthritis is
loss of articular cartilage affecting whole joint
- non-inflammatory
-degenerative disease
3 types of inflammatory arthritis
Immune mediated
Crystal arthritis
Septic arthritis (infection)
Example of autoimmune arthritis
Rheumatoid arthritis
(Immune system attacks self)
Psoriatic arthritis
SLE (lupus)
Reactive arthritis
Example of crystal arthritis
Gout (urate) and pseudogout (calcium pyrophosphate dihydrate)
Crystals trigger inflammation
What is septic arthritis
Bacterial infection in the joint (medical emergency)
Function of muscles
Force generators of MSK system : move bones around a joint
Respond to load (hypertrophy) V atrophy with disuse
Provide protection for underlying structures
Characteristics of both ligaments and tendons (3)
Strong soft tissue structures
Predominantly consist of type1 collagen
Less blood supply than muscle
Characteristics of ligaments (3)
Connect bone to bone
Restrict joint motion
Stabil and proprioception
Characteristics of tendons (3)
Connect muscle to bone
Transmit forces
Collagen fibrils -> fibres
Acute injury to tendons occurs when
Force exceeds tensile strength
Chronic injury to tendons occurs when
There is a Pathological response to poor biomechanics or overuse
What cells control osteoblast and osteoclast formation
Osteocytes
