2 - Basic Concepts in MSK Flashcards
What are the three major tissue components of the musculoskeletal system?
- Bone - Muscle - Connective tissue
From which germ layer(s) does the musculoskeletal system arise from?
Mesoderm - Specifically paraxial mesoderm (flanks the neural tube)
What are the functions of bone?
- Support - Protection - Metabolic (store of Ca2+ and phosphate) - Storage (fat in bone marrow) - Movement (joints) - Haematopoiesis (in adults)
What are the functions of skeletal muscle?
- Locomotion - Posture (don’t need to consciously activate them) - Metabolic (store glycogen) - Venous return - Heat production - Continence
What is the structure and function of a tendon?
- High collagen (type I), low elastin = very little stretch - Regular dense connective tissue - Force transmission from muscle to bone
What is the structure and function of a ligament?
- Regular dense connective tissue (same as tendons) but undulate and arranged in fascicles - Fascicles separated by loose CT and ground substance - Support bone to bone
Where is the superficial fascia and what is it’s function?
- Subcutaneous layer of the skin (hypodermis) - Made of loose connective tissue - Soft medium for nerves and vessels to pass through - Protection - Insulation
Where is the deep fascia and what is it’s function?
- Sheets of connective tissue surrounding muscles - Dense connective tissue - Compartmentalisation - Supports and protects muscles - Barrier to the spread of infection
What is the function of articular (hyaline) cartilage?
Decrease friction within joints
What is the function of fibrocartilage?
- Shock absorption - Increase bony congruity (the way bones interact to maximise surface area)
What is the function of the synovial membrane?
Secretes synovial fluid for joint and tendon lubrication
What is the function of a bursa?
Synovial fluid-filled sacs to protect tendon and ligaments from friction as they run over bone
What cells and ECM components form bone?
- Cells - osteocytes, osteoblasts, osteoclasts - ECM - collagen fibres (calcified dense CT) and ground substance, also contains lots of CaPO4 (gives rigidity)
What does CaPO4 do in bone?
- Gives rigidity and compressive strength
What do the collagen fibres do in bone?
- Give tensile strength
What is the function of an: - osteoblast? - osteoclast? - osteocyte?
- Osteoblast - builds bone from calcium and phosphate - Osteoclast - releases acidic substances to breakdown bone releasing calcium and phosphate - Osteocyte - trapped osteoblasts, communicate through cytoplasmic processes
What is the functional unit of cortical bone?
The osteon
The canals running parallel to the length of the bone in the centre of the osteon are called ……
Haversian canals
The canals running perpendicular to the length of the bone, connecting osteons, are called ……
Volkmann’s canals
What are the 5 types of bone? Give an example for each.
- Long - e.g. humerus - Short - e.g. trapezoid - Flat - e.g. sternum - Irregular - e.g. vertebrae - Sesamoid - e.g. patella
What are the primary functions of the 5 types of bone? - Long - Short - Flat - Irregular - Sesamoid
- Long - good lever (movement) - Short - point of attachment and give large range of motion - Flat - protection - Irregular - varied functions (mostly protection and muscle attachments) - Sesamoid - protect the tendons as they cross other bones (other biomechanical reasons too)
A large site of attachment suggests a more ………… muscle (e.g. at the greater …………… of the femur)
Powerful Trochanter
Why do bones often have grooves for nerves and vessels to sit in?
- Over evolutionary time, nerves and vessels have developed grooves in the bones along which they project - There is no free space within the body
An indentation in a bone for structures to pass through is called a ……
Notch
A hole in bone for structures to pass through is called a …..
Foramen
Blood flow to a bone is supplied by its ……… ……… During development, there are also …….. ……….. supplying the epiphyses
Nutrient artery Epiphyseal arteries
What happends to the epiphyseal arteries present in development in mature bone?
- Epiphyseal arteries degrade, the epiphysis gets blood from the nutrient artery - Entry points of the former epiphyseal arteries become foramena in the bone surface
What happens if a bone is deprived of its blood supply?
- Ischaemia causes avascular necrosis - Especially important in fractures of the scaphoid and neck of the femur
What cells function to remodel bone?
Net effects of osteoblasts and osteoclasts
Give examples of joint with a high range of movement and a low range of movement?
High - Shoulder Low - teeth and jaw, skull
Highly mobile joints are ……… stable
Less stable (highest risk of dislocation)
What are the three classifications of joints? Which have the most and least range of movement?
- Fibrous (least movement) - Cartilaginous - Synovial (most movement)
What is a fibrous joint?
- Collagen fibres joining bones - Very limited mobility = high stability/strength - E.g. Sutures of the skull
What is a cartilaginous joint?
- Cartilage acts as glue holding the bones together - Limited mobility - Ends of growing bones or along the midline of the body - E.g. epiphyseal plates (primary), pubic symphysis (secondary), intervertebral discs (secondary)
What is a synovial joint?
- Bones capped with smooth articular cartilage with a thin film of synovial fluid between
- Highly mobile
- E.g. shoulder, hip etc.
What are the 6 types of synovial joint?
- Plane
- Hinge
- Pivot
- Saddle
- Ball and socket
- Condyloid
Give an example of each type of synovial joint. - Plane - Hinge - Pivot - Saddle - Ball and socket - Condyloid
- Plane - 2 flat surfaces (e.g. carpals, tarsals) - Hinge - single plane (e.g. elbow) - Pivot - pronation/supination (e.g. radius and ulna) - Saddle - movement in 2 planes (e.g. thumb and carpals) - Ball and socket - movement in many planes (e.g. hip) - Condyloid - elliptical, 2 planes but no rotation (e.g. radius/ulna to carpals)
How do synovial joints develop?
- Synovial joints will form between adjacent cartilage models, in an area called the joint interzone - Cells at the centre of this interzone region undergo apoptosis to form the joint cavity - Surrounding mesenchyme cells from the perichondrium will form the periosteum, the joint capsule and supporting ligaments
What are the three classes of levers?
- First class - effort and load are either side of the fulcrum
- Second class - fulcrum and effort at either end of the lever with load in the middle (i.e. wheelbarrow)
- Third class - fulcrum and load either side with effort in the middle
Give a musculoskeletal example of each of the three types of lever.
- First class - tilting the head
Second class - calf muscle raising the heel
Third class - biceps lifting the arm
Define:
- origin
- insertion
- Origin - stationary proximal anchor point
- Insertion - mobile distal attachment point
Can be inverted if the insertion point is fixed
Muscles can only ……..
Pull
What two factors affect the action of a muscle on a joint?
- Orientation of the fibres - Relation of those fibres to the joint
Muscles pull but don’t always shorten, what types of contraction are possible?
- Concentric contraction - pull and shorten - Eccentric contraction - pull and lengthen (usually controlling movement of another muscle) - Isometric contraction - pulls and stays the same length (e.g. carrying a load)
Muscles are found in compartments. Compartments are separated by …….. ………. What is the significance of compartments?
Deep fascia - Contain functionally-related muscles with the same nerves and vessels (mostly)
What are the types of muscle by fibre structure?
- Parallel
- Fusiform
- Circular (sphincter)
- Triangular
- Pennate (unipennate, bipennate, multipennate)
How are tendons anchored to the bone? How is loss of energy minimised between muscle and the bone?
- They are anchored to bone by Sharpey’s fibres - There is a low ratio of elastin to collagen, hence minimal waste of energy transfer
Why do tendons heal slowly?
- Relatively poor blood supply - Low water content - limiting the diffusion of nutrients
What is the function of the peri-articular ligaments surrounding synovial joints?
- Peri-articular ligaments comprise thickenings of the capsule that surrounds synovial joints - They act as mechanical reinforcements for the joint.
What is an aponeurosis?
Sheet-like structures that are (similar to tendons) that join muscles together
Not all aponeuroses still contact a muscle, where are these found?
- Palmar aponeurosis - Plantar aponeurosis
What is Hilton’s Law?
A nerve to a muscle will also supply the joint capsule a muscle crosses and the skin overlying the muscle insertion
What genes control body segmentation?
Hox genes
How do hox genes specify where a structure goes?
- These genes are expressed in a segmental pattern in a cranio-caudal (top-to-bottom) axis - The order that the Hox genes are encoded on the chromosome is reflected in the order they are expressed in the body
Hox genes determine ………… …………. but not the formation of the segments themselves.
Segmental identity
Mutation of Hox genes is an example of a homeotic mutation. What is a homeotic mutation?
- A mutation that causes tissues to alter their normal differentiation pattern, producing structures in unusual locations. - E.g. sixth lumbar vertebra in place of the first sacral vertebra
What is polydactyly?
- Formation of extra digits
- Mutation of Hox genes governing digit (finger or toe) development
Homeotic mutation in the cervical spine can result in generation of additional ribs. What problems can this cause? What is the name of this condition?
- Additional cervical ribs present clinically by compressing the nearby major arteries and nerves
- Thoracic outlet syndrome
The upper and lower limbs are serially homologous, what does this mean?
The upper and lower limbs have extremely similar development leading to extremely similar anatomy. (E.g. hip = shoulder, femur = humerus, knee = elbow etc.)
The upper and lower limbs are serially homologous, what does this mean?
The upper and lower limbs have extremely similar development leading to extremely similar anatomy. (E.g. hip = shoulder, femur = humerus, knee = elbow etc.)
The upper and lower limbs are serially homologous. However, the radial nerve (dorsal) and femoral nerve (ventral) are on opposite sides of the limbs. Why is this?
Due to 90 degree rotation of both the upper (lateral rotation - out) and lower (medial rotation - in) limbs in different directions during development.
