L2: Basic concepts Flashcards
What are the 3 main components of the musculoskeletal system?
- Muscle
- Bone
- Connective Tissue
What is the embryonic origin of the 3 main components?
Mesoderm
What are the functions of bone?
- Support
- Protection
- Metabolism (calcium and phosphate)
- Storage (calcium, phosphate, proteins, fat)
- Movement (at joints)
- Hematopoiesis
What are the functions of skeletal muscle?
- Locomotion
- Metabolic
- Posture
- Venous return
- Heat production
- Continence
What are the different types of connective tissue and there function?
- Tendon –> muscle to bone
- Ligament –> bone to bone
- Fascia –> compartmentalisation and protection (very tough)
- Cartilage –>
- Hyaline –> end of bones –> friction-less movement
- Fibrocartilage –> shock absorber and bony congruity (complementary shape to bone) –> IVD and knee
- Synovial Membrane –> synovial fluid –> lubrication
- Bursae –> Synovial fluid filled sacs –> frictionless movement of tendons, ligaments etc
What are the main cells found in bone? What is the function of each?
- Osteoblasts –> formation of bone, synthesis and deposit osteoid (collagen), then add calcium phosphate to mineralise it
- Osteoclasts –> Resorption of bone, multinucleated, secrete acid to dissolve bone and then absorb minerals (calcium and phosphate)
- Osteocytes –> Osteoblasts trapped in lacuna, filipodia –> communication and nutrients
What type of bone forms the outer layer?
Compact or cortical bone
What type of bone forms the inner bone?
Spongy or cancellous bone
Spaces occupied by bone marrow
What are the two division of the skeleton?
Axial –> longitudinal axis (trunk and head)
Appendicular –> Upper and lower limbs
Define osteology?
The study of the structure and function of bones.
How are bones classified?
- Long- Length > width
- Short- Length = width
- Irregular
- Sesamoid - In tendon
- Flat - roughly parallel edges
What is the structure of a long bone?
- Length > Width
- Diaphysis –> long shaft
- Metaphysis –> flares out adjacent to growth plate
- Epiphysis–> End of long bone
- Articular surface –> hyaline cartilage
- Medullary cavity –> Lind with endosteum
- Periosteum –> outside of bone
What is contained within a long bone?
Children–> Red marrow –> hematopoiesis
Adults –> Yellow marrow –> fat
How is a long bone supplied?
Nutrient artery penetrates the diaphysis.
Where are long bones normal found? Why?
Appendicular skeleton
Rigid levers
Muscle attachment and movement
Where are short bones found? Function?
Long= Wide
Ankle joints and wrist
Stability and great range of movement.
Where are flat bones found? Function?
Skull, ribcage, pelvis, sternum
Protection
Attachment for muscles
What are irregular bones?
Vary in shape and size
Vertebrae–> offer protection
What is a seasamoid bone? Function?
Bone within a tendon (patella, hands and feet)
Protection from stress and wear
Falcrum for muscles
What are processes? What are the different types?
Prominent projections of a bone. Articulating or non articulating. Articulating - Head --> rounded - Condyle --> knuckle like - Facet --> flat surface Non Articulating - Epicondyle -->Small projection - Trochanter --> Blunt projection - Tubercle --> knob-like rounded process - Tuberosity --> large roughened process - Crest --> prominent border on ridge - Line --> less prominent ridge - Spine --> sharp slender process
What are depressions? Different types?
Indents on bone –> Blood vessel, nerves, soft tissue
- Fovea
- Sulcus/ groove
- Fossa
- Cavity
- Notch
What are openings?
Where BV or nerves pass through bone
- Fissure –> slit like opening
- Foramen –> Hole
- Canal –> Tube-like
What is the blood supply to all bones? What additional blood supply?
Periosteal arteries –>periosteum
Nutrient artery –> diaphysis
Some bones:
Metaphyseal arteries –> enter at site of attachment of capsule
Epiphyseal arteries –> supply epiphysis when growth plate present
Anastamose in adulthood
What happens if blood supply to bone is lost? What could cause this to happen?
Avascular necrosis
Fracture (most common), alcoholism, excessive steroids, trauma, radiation, thrombosis etc…
What is bone remodelling?
Changes in the activity of osteoblast and osteoclast to change the shape of bone.
Response to environmental factors e.g. exercise or after fracture
What is a joint?
Articulation between two or more bones
What are the main classification of joints?
Fibrous, Cartilagenous, Synovial
What are fibrous joints?
Very limited mobility
Most Stable
Collagen fibres join bone
E.g. skull, inferior tibofilbular joint, root of tooth and mandible
What are cartilaginous joints? How are they further classified?
Limited mobility
Cartilage unites bones
Primary–> hyaline cartilage –> completely immobile
- e.g. sternocostal joint
Secondary–> symphyses –> hyaline cartilage with fribrocartilage between –> midline of body
- e..g symphysis pubis
What are synovial joints? What are the features?
Joint cavity containing synovial fluid –> Lubrication
- High degree of mobility
- Articular surfaces –> hyaline cartilage (smooth, low-friction, resists compressive forces
- Fibrous capsule –> collagen, continuous with periosteum
- Synovial membrane –> vascularise, synovial fluid, line capsule
What are the different types of synovial joints?
- Hinge –> Elbow –> single plane, flexion and extension
- Plane –> Vertebra –> flat surfaces slide against each other
- Ball and Socket –> Shoulder, hip –> Stable, multiple directions
- Condyloid –> Base of skull –> two elliptical bowls, not rotation
- Pivot –> atlanto-axial joint –> peg with a ring shaped hole –> rotation without gliding
- Saddle –> Thumb (carpometacarle joint) –> ‘rider in a saddle’ –> motion in two planes at same time
What are some specialised structures found in the synovial joint?
Bursae –> small sac, synovial fluid, cushion between tendon and bone
Tendon sheaths –> elongated bursae
Synovial fluid –> clear, viscous, slightly alkaline fluid, reduce friction, shock absorber, transport nutrients
Why is there a rich blood supply around synovial joints?
Articular cartilage and fibrous capsule avascular.
Synovial membrane–> rich blood supply –> nutrients
What factors affect the range of motion at a joint?
- Strength and tension of ligament supporting joint
- Shape of articulating surfaces
- Arrangement and tone of muscles
- Neightbouring soft tissue
- Disuse
- Effect of hormones
How does a joint develop?
Bone develops from cartilage model
Joint- interruption in model –> joint interzone
Mesenchymal cells differentiate into hyaline cartilage
Cells in interzone under apoptosis –> joint cavity
Surrounding mesenchymal cells form perichondrium (capsule)
How do ligaments in the knee develop?
Some cartilage is preserved in the joint interzone
Becomes intra-articular ligaments
What are the different classes of levers in the body?
First class- Effort applied to the opposite side of fulcrum to the load
Second class- Load being lifted lies between the effort and the fulcrum
Third class- Effort lies between the loads and the fulcrum.
What are the two key principles about muscles?
They can only pull, NOT push.
Can only act on joints that there tendons cross.
What do muscles produce force for?
To provide stability
To move bones
What are the attachment sites of muscles?
Origin- stationary anchor point, usually proximal
Insertion- mobile attachment point, usually distal
Contraction is symmetrical on origin and insertion, stabilisation of origin means the insertion point moves
Can you tell which way a muscle will cause something to move?
Yes, you can tell by the direction of the muscle fibres. The action of a muscle depends on its starting position.
What is the name given to the prime muscle? What is the name given to the muscle that opposes its action?
Agonist and antagonist
What is the name of a muscle that assists the prime mover?
The synergist
What do neutralisers and fixators do?
Neutralisers prevent unwanted actions of muscles
Fixators stabilise the joint.
What are the three types of muscle contraction?
Concentric–> muscle fibres shorten
Eccentric–> muscle fibres lengthen
– controlled movement such as lying down from sitting up
Isometric–> muscle fibres stay the same length
– carrying shopping
What are the different arrangements of skeletal muscle fibres?
- Parallel
- -> Strap- fibres parallel, longitudinal
- -> fusifrom - cyclindrical, wider in middle,
- -> Triangular - fibres converge at one end
- Circular - rings of fibres
- Pennate
- -> Unipennate- fascicles on same side of tendon
- -> Bipennate- fascicles on both sides of tendon
- -> Multipennate - central tendon branches, fascicles orginate from each tendon
How are muscles arranged in the body?
They are usually arranged in compartments with functionally related muscle.
Normally share same blood supply and innervation.
Surrounded by deep fascia
What are the names of the different compartments?
Anterior, posterior, lateral and medial
Sometimes even superficial posterior and deep posterior compartments etc…
Why is connective tissue called connective tissue?
It is all connected to one another!
What is fascia?
Band or sheet of connective tissue
Compare and contrast superficial and deep fascia?
Superficial fascia –> subcutaneous fatty layer
–> storage, passageway for lymphatics, BV and nerves and protection
Deep fascia –> Thickened elaboration of the epimysium
–> contains collagen and elastin –> wavy pattern parallel to fibres –> flexible but resists great forces
–> can be named
What is a tendon? Function?
Dense regular connective tissues, low ratio of collagen to elastin
Connect muscle to bone
Anchored to bone by Sharpey’s fibres
Do tendons repair well after injury? Why?
No, limited blood supply and low water content limiting diffusion
What are ligaments? Function?
Dense regular bundles of connective tissue
Connect bone to bone
Stabilise joints, limit range of movement
What is an aponeurosis?
Flatterend tendon
Primarily connect muscles to other muscles, can connect muscle to bone
What is Hilton’s Law?
Nerve supplying the muscles also supplies the joint capsule and skin overlying insertions of these muscles.
What are segments?
The repeating pattern of subunits arranged in the longitudinal axis.
What controls segmentation?
Hox genes, expressed in the cranio-caudal axis.
Order on chromosome reflects expression in the body.
What do Hox genes do?
They determine the different types of vertebra and limb that will form in each part of the body.
What are mutation in Hox genes called? What is a consequence?
Homeotic mutation
Alters normal patterning and can result in body parts in unusual location, or extra or reduced numbers of digits, ribs, toes etc…
How are the upper and lower limbs homologous?
Shoulder = Hip Humerus = Femur Ulnar = Tibia Radius= Fibular Carpal bones = Tarsal bones Phalanges = phalanges Similar pattern of muscles and nerves is also seen.
What are the limb buds and when do they first appear?
Mesenchyml stem cells covered in ectoderm
Appear 4th week
How do limbs develop?
Limb bud forms apical ectodermal ridge
Elongation by prolferation of mesenchyme
Forms cartilage model
12th week endochondrial ossification begins
Hyaline cartilage remains –> articular cartilage
How do the limb bus rotate?
Upper limb 90 degree outwards (laterally)
Lower limb 90 degree inwards (medially)
What does rotation of the limbs explain?
Why flexion and extension in limb in different directions
Spiral patterns of dermatomes
Sartorious muscle oblique direction
