Intro to musculoskeletal Flashcards
What are the two types of bones that differ in length?
What are the component parts of these bones?
What do bumps on bone represent?
- Long bones and short bones
- Long bones have an epiphysis at either end, diaphysis centrally which is joined to the epiphysis via the metaphysis.
- Short bones often irregular, e.g carpal region of the hand
- Bumps on bones represent points of muscle attachment, bone reinforces itself at regions of stress.
What are two other types of bone?
Where are they found and what is their function?
- Sesamoid bone:
- found within tendons
- reduce wear and tear
- improve muscle efficiency
- Flat bones:
- large SA for muscle attachment
- Weight / force transfer region
- Protection (e.g. pelvic girdle and skull).
What makes up the axial skeleton?
What makes up the appendicular skeleton?
- Axial skeleton formed of:
- skull
- sternum
- Ribs
- vertebrae
- sacrum
- coccyx
- Appendicular skeleton:
- Hip bones/ pelvic girdle
- pectoral girdle
- upper and lower limbs
What week does limb development start in the embryo?
When is the overall shape of the limb apparent?
what process is required for digit formation?
- The limbs grow out as limb buds from the developing embryo at week 4/5
- Digits and overall limb shape are present by week 8
- Digits form by programmed cell death, if this doesnt occur –> webbed digits
Describe some of the limb abnormalities that can be seen
What mechanisms are there that can result in abnormal limb development?
- Amelia = complete lack of limb development
- Meromelia = only partial limb development
- Phocomelia = seal limb / flipper
- Polydactyly = extra digit
- Syndactyly = fused digits
Abnormal limb development can occur as a result of:
- Retinoids (careful when advising on diet in pregnancy, vitamin A)
- Thalidomide (tetratogenic drug withdrawn for its use with morning sickness)
- Mechanical –> due to strangulation of tissue by amniotic bands
How does lower and upper limb structure differ according to their different roles?
Upper limb:
- range of movement in preference to strength
- carriage
- fine manipulative tasks
- feeding
- minimal locomotion
Lower limb:
- support body weight
- maintain upright posture
- locomotion
- accomodate shock loading
What type of joint predominates in the limbs?
Describe the joints seen in the upper and lower limb
- Synovial joints predominate in the limbs –> a synovial joint is a fibrous type joint where bones are joined together via a fibrous joint capsule that is continuous with the periosteum of joined bones.
In the upper limb:
- shouder = ball and socket joint
- Elbow = hinge joint formed between humerus, radius and ulna.
- A pivot joint exists between the radius and ulna both proximally and distally
- The wrist is called the radiocarpal joint, and is a synovial joint between the radius and the proximal row of carpal bones.
- Upper limb ends with the carpals, metacarpals and phalanges
In the lower limb:
- ball and socket joint at the hip
- modified hinge joint at the knee
- hinge joint at the ankle
- mixed joint types between the tarsals, metatarsals and phalanges
Describe the two main types of joint in the body and the subcategories of joints that exist with them
Two main types of joint are fibrous and cartilaginous.
Fibrous joints have no joint cavity, they are connected by dense connective tissue consisting mainly of collagen. They are “fixed/ immovable” joints, and relatively stable.
Cartilaginous joints are connected entirely by cartilage (either hyaline or fibrocartilage), and are relatively fixed and stable to highly mobile.
Examples of fibrous joints are:
- Sutures
- Gomphosis –> mobile peg and socket joint, only found between the teeth and mandible/ maxilla
- Syndesmosis –> fibrous sheet of tissue that keeps bones in close proximitiy, helps transmit forces between them.
Examples of Cartilaginous joints:
- Epiphysis –> joint between rounded end of the bone (epiphysis) and the dipahysis via metaphysis
- Symphysis –> is a fibrocartilaginous joint, a secondary cartilaginous joint. It is slightly movable and is a growing together of parts or structures (e.g. pubic symphysis and intervertebral discs).
What two factors must joints balance?
For:
Fibrous
1º & 2º Cartilagenous
Synovial
Explain how much of each of these factors there are
- All joints must balance mobility with stability.
- Fibrous joints (e.g sutures, syndesmosis) tend to be highly stable with very little mobility
-
1º & 2º Cartilaginous joints:
- Primary cartilaginous joint –> e.g occuring at growth plates between ossification centres, connected by hyaline cartilage, allow a little movement, highly stable
- Secondary cartilaginous joint –> e.g Pubic Symphysis, manubriosternal joint, IV discs. Fibrocartilaginous joints occuring in the midline. Allow a little movement but stables.
-
Synovial joint:
- bones joined together by a fibrous joint capsule continuous with the periosteum of joined bones.
- Highly mobile, little stability
Describe the anatomy of a synovial joint
- The bones of a synovial joint are enclosed by an articular capsule with an inner synovial lining/ serous membrane that secretes synovial fluid
- Articular capsule has outer fibrous later that is continuous with the periosteum of the two bones, holds them together and supports underlying synovium
- Inner synovial layer = synovium, highly vascularised, absorbs and secretes synovial fluid, responsible for nutrient exchange between blood and joint
- Synovial fluid lubricates the joint, acts as a shock absorber., distributes nutrients.
- Ends of the two bones are covered by smooth, slippy hyaline cartilage which is avascular
- The synovial membrane also forms bursae and sheaths which cover parts of tendons and ligaments.
What is the effect of increasing joint constraining forces?
Give an example of two joints where one has more constraining forces than the other
Increasing joint constraining forces decreases joint mobility but increases the stability.
E.g. the hip joint is much more stable than the shoulder joint due to a deeper socket and the acetabular labrum which deepens the joint further, increasing SA of contact and stability
Shoulder joint much more shallow, better range of movement but easier to dislocate.
Describe the pectoral girdle:
Mobility/ stability/ range of movement
Clinically relevant fractures
tension
- Pectoral girdle is a mobile structure with only one joint with the axial skeleton –> Via clavicle onto the manubrium of the sternum
- Girdle mobility increases overall range of limb motion
- shoulder range of motion is high, stability is low
- Compressive forces are transmitted to the clavicle –> fracture due to either direct blunt force trauma or a fall on an outstretched hand.
- Tension is transmitted via the muscles
- Scapula fractures are very uncommon, due to high impact blunt force trauma.
Describe the pelvic girdle:
Shape
what forms it
function
range of motion
stability
what it enables
What type of trauma can fracture it?
- Pelvic girdle also called bony pelvis = rigid ring of bone that is basin shaped, partly formed by the axial skeleton
- connects the trunk to the legs, supports and balances the trunk, contains/ supports intestines/ bladder/ internal sex organs.
- Consists of paired hipbones connected via pubic symphysis and behind via the sacroiliac joints. Each pelvic bone made up of wing shaped ilium, ischium below and pubis in front.
- Provides rigid connection with the axial skeleton
- Hip range of motion = medium
- stability = medium/ high
- Distributes weight of axial body to the lower limbs
- Enables locomotion and standing
- force transmission mostly via compression
- High force trauma (RTA) can fracture the pelvic girdle.
What structures normally support synovial joints?
How can they be damaged or stretched?
- Synovial joints are normally supported by accessory ligaments that are either separate ligaments or parts of the joint capsule
- Consist of dense regular connective tissue, adapted for resisting strain, resisting any extreme movement that may damage the joint.
- E.g. Iliofemoral, pubofemoral and ischiofemoral ligaments.
- Damage to accessory ligaments can occur with trauma (fracture), or by twisting/ landing awkwardly where ligaments are at full stretch, causing them to tear away from the bone.
- Synovial joints also can contain articular fat that protects the articular cartilage
- Can be reinforced by tendon attachement from surrounding muscles
- Bursae –> sac of synovial fluid at points where there is high friction
What are bursae?
What is inflammation of bursae called? What does it cause?
How can it be treated?
Bursae are pockets of synovium/ synovial membrane filled with synovial fluid that are found in regions of high friction or wear.
Allow joints greater freedom of movement whilst protecting articular surfaces from friction degeneration
Some are isolated, some can communicate with joint spaces.
Bursistis = inflammation of bursa
Causes localised pain, and tenderness on palpation
can be aspirated or injected with steroid.
Where are synovial sheaths found?
What is their function?
What is inflammation of the synovial sheath called?
What is inflammation of the synovial sheath and tendon called?
What are the symptoms of synovial sheath inflammation?
What is the clinical relevance of synovial sheaths?
- Synovial sheaths are found surrounding tendons at points of wear/ friction or direction change
- Function: reduce friction between tendon and surrounding structures
- They can be individual or shared e.g. common flexor sheath in the hand that extends through palm and carpal tunnel into proximal forearm
- inflammation of the synovial sheath = synovitis
- Inflammation of tendon and synovial sheath = Tenosynovitis
- Symptoms = pain on use and possible tendon rupture
- Clinical relevance = sheaths can act as routes for infection spread e.g. flexor tendon sheath infection from hand into arm
What are nerve plexi?
Give examples
What do the named nerves from plexi contain?
- Nerve plexi are where the ventral rami of spinal nerves join and exchange neurons
- Brachial plexus in the upper limb
- Lumbar and sacral plexus in the lower limb
- Named nerves from plexi contain neurons from multiple spinal nerves
Define a dermatome
How can neurons travel to innervate their dermatome?
What is the difference between dermatomal loss and cutaneous loss?
- A dermatome = an area of skin innervated by a single spinal nerve
- The neurons from a spinal nerve can take multiple different routes to innervate their dermatome
- As nerve plexi allow neurons from different spinal nerves to converge and exchange neurons, a named neuron from that plexus may contain several spinal neuron routes each innervating a different dermatome.
- Dermatomal loss would mean loss of sensation in the region of that dermatome only
- Cutaneous loss would mean loss of sensation in a cutaneous region e.g. anterior thigh that has L1/ L2/ L3/ L4 dermatomes but cutaneously is supplied by obturator nerve, femoral nerve, lateral femoral cutaneous.
What is a cutaneous nerve area?
- Cutaneous nerve area = area of skin innervated by a named cutaneous nerve
- It can innervate all of a dermatome, part of one or all of dermatome plus parts of another (e.g. anterior thigh with L1/L2/L3/L4 dermatomes, and cutaneous innervation of obturator nerve, femoral nerve and lateral cutaneous nerve).
- On picture see that nerve Y territory is made up of C5/6/7 dermatomes.
What are compartments?
What is the general function of anteior compartments?
What is the general function of posterior compartments?
What is compartment syndrome?
How is it treated?
- Compartments are formed by deep fascial layers that completely surround muscle groups within the limbs, forming a jacket
- Anterior compartments –> generally = flexor compartment
- Posterior compartment –> generally the extensor compartment
- Compartment syndrome = medical emergency, sharp increase in pressure within a compartment that can cut off the blood supply leading to necrosis.
- Treated by surgically opening up the compartment until the swelling has decreased. (infection risk but better than losing the limb).
What can create spaces in the limb? What is the clinical importance?
What are retinacula and what is their function?
- Fascia can create contained spaces in the limb, this is important in infection localisation and spread.
- Retinacula are thick bands of fascia that prevent tendon bowstringing.
- They keep tendons in close proximity of the the joint enabling functioning through a range of joint motion.
What is cellulitis?
What is paronychia?
What is felon?
- Cellulitis = common skin bacterial infection, appears red, inflammed and hot. Track the spread via pen marks
- Paronychia = soft tissue infection around the nail bed, classically presents with erythema and pus around nail bed
- Felon = abcess of distal pulp of the fingertip
Label this image
Draw from memory after.
Describe the venous drainage of the limbs
Which veins are clinically useful?
Venous drainage starts superficial as arches on the dorsum of the hand or foot and eventually drain into deeper veins.
Superficial veins are clinically useful for cannulation and often run close to cutaneous nerves.
What are venae comitantes?
Venae comitantes are usually paired veins that run closely with arteries and between muscles. The pulsation of the artery helps aid venous return. As they usually run in pairs they are known as venae comitantes.
Describe the lymphatic drainage of the upper and lower limb
Upper:
- From cubital fossa, lympatic drainage follows arteries to key groups of nodes
- Key nodes are:
- humeral, subscapular and pectoral –>
- –> All run into Central –> apical –> supraclavicular
Lower:
- From popliteal fossa –> inguinal lymph nodes
