Musculoskeletal System Intro 0.0 Flashcards
Abduction
moving away from medial point
Adduction
moving towards median plane
What movement to abduction and adduction show
Abduction/ adduction shown with thumb movement and limb movement
Pronation
radius rotates medially, so palm of hand faces posteriorly (dorsal) or inferiorly
Supination
radius rotates laterally, so palm of hand faces anteriorly (ventral) or superiorly
How to remember pronation vs supination
Pour the drink, carry the soup
Inversion
the sole of the foot is directed towards median plane , movement inwards
Eversion
the sole of the foot is directed lateral from median plane
Dosifiexion
lift foot up
Plantar flexion
point foot down
Axial skeleton
bones of head, neck, and trunk
• Skull
• Vertebral column
• Ribs
Appendicular skeleton
bones of limbs
Including pectoral and pelvic girdles
Describe 2 types of bone
- Compact - cortical bone
- cancellous = spongy bone
Structure of bone
• Compact = (cortical) surrounds spongy (trabecular, cancellous) bone, provides strength, and is greatest near middle of shaft of long bones
• Spongy = consists of spicules of bone which enclose cavities containing blood-forming cells (marrow)
• Periosteum = on the outside of bone is a dense fibrous layer
-muscles insert
-contains bone forming cells.
-not found in the regions covered by articular cartilage
Haversion system (osteon)
basic unit microscopic canal system (structure of compact bone)
• Osteocytes sit in lacunae – form rings (lamella) around central Haversian canal
5 classifications of bone
- Long – tubular eg humerus
- Short – cuboidal eg tarsus and carpus
- Flat – usually protective eg bones of cranium
- Sesamoid – eg patella, protect tendons from wear, change the angle of tendon
- Irregular (various shapes) – eg spine or bones of face
Long bone
tubular eg humerus
Short bone
cuboidal eg tarsus and carpus
Flat bones
usually protective eg bones of cranium
Sesamoidbone
eg patella, protect tendons from wear, change the angle of tendon
Irregular bone
- Various shapes
eg spine or bones of face
Where do bones derive from
—> all bones derive from mesenchyme (mesodermal)
2 types of ossification
Intramembranous ossification
Endochondral ossification
Intramembranous ossification
(mainly bones of the face and cranial vault)
= mesenchymal models of bones form which begin to ossify directly in foetal period
Endochondral ossification
= cartilage models of bones form from mesenchyme then bone replaces cartilage
Perichondrium -> calcification -> primary ossification -> secondary ossification -> epiphyseal plate
Steps of Endochondral ossification
- Fetal hyaline cartilage model develops
- Cartilage calcifies and periosteal bone collar forms around diaphysis
- Primary ossification centre forms in the diaphysis
- Secondary ossification centres form in epiphysis
- Bone replaces cartilage, except articular cartiliage and epiphyseal plates
G. Epiphyseal plates ossify and form epiphyseal lines
Bone blood supply
• Passes through compact bone via nutrient formina = supplies marrow, spongy bone and deeper part of compact bone
Role of periosteum
- –>fibrous connective tissue surrounding bone (except where articular cartilage occurs)
- can lay down new bone esp during fracture healing
- supplies most of the compact bone
- bone from which the periosteum has been removed, dies
- has loads of nerves
Joint definition
—> A union or junction of 2 or more bones
3 classifications of joints
fibrous, cartilaginous, synovial
Fibrous joints
–> Very stable joint, limited range of movement
• Bones united by fibrous collagen tissue
Fibrous joints _ examples
- Sutures of cranium: on completion of growth, many sutures obliterated (synostoses) = no movement
- Syndesmosis: sheet of fibrous tissue (ligament or membrane) allow some movement eg interosseous membrane in forearm (radius and ulna) (tibia and fibula)
- Dento-alveolar syndesmosis (gomphosis): a peg-and-socket junction between tooth and socket; maintained by collagen
Cartilaginous joints
–> bones united by cartilage
• Great stability of joint = limited range of movement
Cartilaginous joints - example
- Primary cartilaginous joints (synchondroses): bones united by hyaline cartilage, eg epiphyseal growth plates of the long bones
- Secondary cartilaginous joints (symphyses) : bones covered with hyaline cartilage with a pad of fibrocartilage between them (pubic symphesis)
Synovial joints
—> Connections between skeletal components where the elements are separated by a narrow articular cavity
• Various factors confer stability (Intrinisic/extrinsic ligaments, configuration of bone and support from the soft tissues) = freely moving joints
Synovial joints - features
- joint capsule – inner synovial membrane, outer fibrous membrane
- articular cartilage (hyaline) covering articular surfaces
- synovial fluid in joint cavity – a potential space that contains synovial fluid (secreted by synovial membrane) - about 0.5–4 ml within large joints e.g. knee
Synovial joint classifications
Ball and socket Hinge Pivot Plane Condylar Bicondylar
Innervation of joints
Inervation —> rich nerve supply - pain fibres in fibrous part of capsule and accessory ligaments
• also contribute to proprioception (awareness of movement and position
Hilton’s law
Nerves supplying a joint also supply muscles moving the joint and the skin overlying the muscle
Blood supply to joint
Articular arteries
- arise from vessels around joint and supply joint
They anastomose to form Peri articular aterial plexus
The Peri articular aterial plexus branches and these branches pierce fibrous capsules to form
Sub synovial vascular plexus
What are myocytes
Muscle cells
3 types of muscle
- Skeletal
- Cardiac
- Smooth
Skeletal muscle function
• locomotion
• static support – standing/ posture, stabilise joints
• provide heat – about 80% of chemical energy is lost as heat
– shivering involves involuntary activity of skeletal muscle to raise core temperature
Skeletal muscle structure
- Fibres – large and long cylindrical unbranched multinucleate cells
- cytoplasm of each fibre (sarcoplasm) surrounded by a plasma membrane (sarcolemma)
- bulk of sarcoplasm comprises contractile machinery: myofibrils 1–2 µm in diameter, extend the length of the fibre
- oval nuclei (numerous) usually peripherally located - between the myofibrils and the sarcolemma
3 Skeletal muscle connective tissue
Epi pe en
- epimysium = surround muscle
- perimysium = surrounds bundles of muscle fibres
- Endomysium = surround muscle fibres
First class levers
• Load and force are on opposite sidesof fulcrum (like a seesaw).
First class levers - examples
– Eg muscles in posterior region of neck attached to the skull acting on the joint
– Fulcrum (pivot) is fairly central at the base of the skull
Second class levers
• Load and force are on same side of fulcrum, with load between the force and the fulcrum (like a wheelbarrow).
Second class levers - excemples
– Eg. gastrocnemius muscle exerts force on calcaneus and flexes foot
Third class levers
Load and force are on same side of fulcrum, with force applied between the load and the fulcrum (like a forceps or fishing rod)
Third class levers - excumples
– Eg biceps flexes elbow joint (fulcrum)
Long lever arm
• If lever arm is long, then then muscle contraction will move joint through small angle → lever system is suited to small and/or slow movements/ more forceful movements
Short lever airm
• If lever arm is short, then muscle contraction will move joint through a large angle => lever system is suited to large and/or rapid movements / less forceful movements
Agonist muscle
prime mover; main muscle responsible for specific movement
– sometimes 2 prime movers working equally [can also be gravity]
Eg. Biceps brachii
Antagonist muscle
oppose prime movers
Eg triceps brachii
Synergist
complements action of prime mover, for example resist sideways motion to maintain the force in one direction
e.g. g for biceps brachii → brachioradialis, brachialis
Fixator
steadies proximal part of limb (isometric contraction) while movements occurring in distal parts
e.g. for biceps curl → shoulder rotator cuff
2 types of phasic muscle contraction
- isotonic contraction (tone same, but muscle length changes)
- isometric contraction (length same but tension increases)
Isotonic contraction
– concentric contraction – muscles shorten
– eccentric contraction– muscles length
Fascial compartment
• As muscles contract, blood is pushed out of veins in the compartment
• Valves in veins allow blood to flow only towards heart
→ deep fascia, muscles and valves work together as a musculovenous pump to return blood to heart
Compartment syndrome
Increase in pressure in compartment
5 other examples of connective tissue
Retinaculum
Bursae
Synovial tendon sheaths
Tendons
Ligaments
Retinaculum
-Fascia coming round
• thickening of deep fascia to hold tendons in place where they cross the joint
• prevent “bow stringing” of tendons
• Looks like a bowstring being pulled away from the bow (string = tendon, bow = bone)
Bursae
-closed sacs of serous membranes (secrete fluid)
• usually at locations subject to friction – allow one structure to move over another
• Allows sliding e.g. patella
Synovial tendon sheaths
• bursae wrap around tendons eg under retinaculum or in specialised osseofibrous tunnels (that anchor tendons in place)
Tendon
• Tendons transfer forces developed by skeletal muscles to bone
• Composed of dense, regular connective tissue – 60% dry weight = large collagen type Ifibres – also collagen II and V, elastin, glycoproteins and proteoglycans
• Tendons are slightly elastic (can be stretched by 15% of their length)
Cellularity (and metabolic rate) of adult tendons is very low → increases during infection or injury
– repair involves proliferation of fibroblasts followed by deposition of new collagen fibres
-sparse vascular supply
• Specialised golgi tendon organs – importnant in protecting from injury
Liguments
- Ligaments prevent excessive separation of adjacent bones
* Microstructure and biology of ligaments is broadly similar to tendons; mostly large crimped fibres of collagen type I
Tendons vs ligament
• Two major differences between tendons and ligaments:
– structure: ligaments tend to have fibres orientated in a range of directions
– composition: e.g., ligamentum flavum has very high elastin content, enables it to be stretched more than 80% when the spine is flexed, and yet remain under tension in extension
3 main cells in bone formation
- chondrocytes (cartilage cells – produces mineralised matrix)
- osteoblasts (bone-forming cells)
- osteoclasts (bone-resorbing cells)
→ also osteocytes
What is endochondral bone formation
- cartilaginous template precedes ossification
- complex process that involves three main cell types:
- chondrocytes (cartilage cells – produces mineralised matrix)
- osteoblasts (bone-forming cells)
- osteoclasts (bone-resorbing cells)
What structures use endochondral bone formation
- all axial (vertebral column, sternum, and ribs)
- appendicular (limb) bones of the body, with exception of part of clavicle
- cranial base and pharyngeal arch cartilages also
What is membranous bone formation
- osteoblast progenitors differentiate directly from condensed mesenchyme
- eventually differentiate into osteoid producing mature osteoblasts
- Osteoblasts that get entrapped into the compact bone, reside in lacuna and differentiate into osteocytes
What structures use membranous bone formation
• Most bones of the face and cranial vault
Myotome
• Hypomeres form hypaxial muscles of lateral and ventral body wall (innervated by ventral ramus of spinal nerve) including:
- 3 layers of intercostal muscles in thorax
- anterolateral abdominal wall
- cervical region, contribute to strap muscles of neck
- lumbar region, form quadratus lumborum muscles
Epimeres give rise to
deep epaxial muscles of back (innervated by dorsal ramus of spinal nerve) including:
– erector spinae
Formation of vertebrae
—> formed by resegmnetation of sclerotome
• each sclerotome splits into a cranial and caudal segment
• the spinal nerves grow toward the myotomes
• the caudal segment of each sclerotome recombines /fuses with cranial segment of sclerotome caudal to it
• each of the two segments of the sclerotome contributing to a vertebra
Limb development
- starts with proliferation of somatic lateral plate mesoderm in limb regions of lateral body wall
- upper limb bud appears in lower cervical region day 24 (earlier)
- lower limb bud appears in lower lumbar region at 28 days
- Ectoderm along distal tip of bud forms a ridge- like thickening, apical ectodermal ridge (AER, arrow in C, day 32); divides into dorsal/ventral aspects
Limb rotation
- Upper extremity rotates 90 degrees laterally (ventral, flexor compartment faces anteriorly)
- Lower extremity rotates 90 degrees medially so that embryonic ventral, flexor compartment is posterior and extensors are in front
- Rotation via a torsion in femoral and humeral shafts
