Musculoskeletal Anatomy Flashcards
What makes up the axial skeleton?
The skull, vertebral column, ribs, and sternum (the CENTRAL parts).
What makes up the appendicular skeleton?
The bones of the limbs, including the scapulae, clavicles and the hip bones.
What happens to the skeleton from babies -> adults?
The cartilage (which babies’ skeletons are mostly made up of) ossifies as they grow. Some cartilage remains in adulthood.
What is a joint?
Where two bones meet and articulate with each other.
What is the most common type of joint? Give examples of this type of joint.
Synovial joint. Shoulder, knee and wrist joints.
What is the structure of a synovial joint? Describe the available movement.
Narrow synovial cavity containing lubricating synovial fluid, enclosed in a joint capsule.
Joint capsule has two layers.
Articular surfaces covered with articular hyaline cartilage.
Allow a great deal of movement.
What is the structure of a fibrous joint? Describe the available movement and give an example of this type of joint.
Strong fibrous tissue connects two bones, no cavity and no fluid.
Usually very little (if any) movement.
Individual bones of the skull (sutures).
What is the structure of a primary cartilaginous joint? Describe the available movement and give an example of this type of joint.
Like fibrous joints, but connected by hyaline cartilage instead.
Some flexibility.
Where the ribs meet the sternum (sternocostal joints).
What is the structure of a secondary cartilaginous joint? Describe the available movement and give an example of this type of joint.
Joints connected by fibrocartilage, plus a layer of hyaline cartilage covers the articular surfaces of the bones.
Flexible, but strong and able to support a lot of weight.
The intervertebral discs between vertebrae in the spine.
What are the six types of synovial joint?
Ball and socket, hinge, pivot, saddle, condyloid, and plane joint.
What is a ball and socket joint? Give examples and discuss mobility.
The end of one bone is shaped like a ball, fitting in a bowl-shaped socket on another bone.
Shoulder joint and hip joint.
Allow significant range of movement in all directions -> better fit = more stable but less mobile, and vice versa.
What is a hinge joint? Give examples and discuss mobility.
Just like a hinge on a door.
Elbow joint and knee joint.
Allow significant range of movement, but only in one plane.
What is a pivot joint? Give examples and discuss mobility.
Allows rotational movement only.
C1 pivots around the peg of C2, allowing us to turn our head.
What is a saddle joint? Give examples and discuss mobility.
Shaped like a rider sat in a saddle.
Joint at the base of the thumb.
Permit movement in two planes.
What is a condyloid joint? Give examples and discuss mobility.
Like ball and socket, but oval-shaped.
Wrist joint and the metacarpophalangeal joints (knuckles).
Good range of movement, but only in two planes.
What is a plane joint? Give examples and discuss mobility.
The articular surfaces are flat, almost gliding against each other.
Joints between small carpal bones of the wrist.
Movement is usually limited and dictated y neighbouring bones and ligaments.
What is a ligament?
A band of fibrous connective tissue that attaches bone to bone.
What is the function of ligaments?
Stabilising joints and limiting their movement. Can stretch over time to allow greater joint movility.
What is a sprain?
Occurs when a ligament is overstretched and injured. They may not return to their original shape.
What are the three types of muscle?
Skeletal, smooth, and cardiac.
Which types of muscle are under voluntary or involuntary control?
Voluntary - skeletal.
Involuntary - smooth and cardiac.
Which types of muscle are striated?
Skeletal and cardiac, not smooth.
Where can skeletal, smooth, and cardiac muscle be found?
Skeletal - throughout the body.
Smooth - walls of blood vessels and internal organs such as the intestine.
Cardiac - in the heart.
What connects skeletal muscles to bone or soft tissue?
Tendons, composed of strong connective tissue.
What are the four main orientations of skeletal muscle fibres?
Parallel, convergent, circular, and pennate.
Describe parallel skeletal muscles.
Muscle fibres are aligned parallel to each other.
Two subtypes:
- Fusiform: long tendon at each end, muscle belly
bulges in the middle.
- Strap: belt-shaped and relatively uniform in width.
Describe convergent skeletal muscles.
Fan-shaped with a very broad attachment at one end, and a very small attachment at the other.
Describe circular skeletal muscles.
Muscle fibres arranged in concentric rings around a structure, often called sphincters.
Describe pennate skeletal muscles.
Muscles fibres arranged at an angle to the direction in which the muscle acts.
Three subtypes:
- Unipennate: fibres arranged diagonally, inserting
onto one side of the tendon only (like a one sided
feather).
- Bipennate: fibres arranged in a v-shape, inserting
onto both sides of the tendon (like a feather).
- Multipennate: look like multiple bipennate muscles
side-by-side, all converging onto one tendon (like
multiple fathers).
What is a motor unit?
Composed of a single motor neuron, its axon, and the muscle fibres it supplies. Can massively vary in size dependent on the size of the muscle it supplies.
In an eyeball, may supply only a few muscle fibres.
In the thigh, may supply thousands.
Describe the gross anatomy of the upper and lower limbs.
- Ball and socket joint where limbs
meet torso - Large bone in proximal part
- Hinge joint
- Two bones in middle part
- Collection of small bones at the
distal part - Five digits, one significantly larger
- Most of the muscle mass
concentrated proximally
For what purposes have upper and lower limbs evolved differently to one another?
Upper - for dexterity and mobility.
Lower - for bipedal locomotion and to support body weight.
How have the upper limbs evolved for dexterity and mobility?
Shoulder joint has a shallow socket and lax ligaments - allows for a range of movement.
The fingers are also long and capable of complex movements.
How have the lower limbs evolved for bipedal locomotion and to support body weight?
Hip joint has a deep socket and strong ligaments - very stable.
Foot and toes adapted to weight-bearing rather than dexterity.
How many vertebrae are in the vertebral column, and how many ‘sections’ are these divided into? What are these ‘sections’ called?
33 vertebrae
5 sections
Cervical, thoracic, lumbar, sacral, and coccygeal.
How many cervical vertebrae are there and where are they in the vertebral column?
7
In the neck
C1 - C7
How many thoracic vertebrae are there and where are they in the vertebral column?
12
In the thorax
T1 - T12
How many lumbar vertebrae are there and where are they in the vertebral column?
5
In the abdomen
L1 - L5
How many sacral vertebrae are there and where are they in the vertebral column?
5
In the pelvis, fused into the sacrum
S1 - S5
How many coccygeal vertebrae are there and where are they in the vertebral column?
4
In the pelvis, fused into the coccyx
Co1 - Co4
Which segment/s of the vertebral column curve anteriorly? What does this form?
Cervical segment -> cervival lordosis
Lumbar segment -> lumbar lordosis
Which segment/s of the vertebral column curve posteriorly? What does this form?
Thoracic segment -> thoracic kyphosis
Sacral segment -> sacral kyphosis
What connects the vertebrae to one another?
Small synovial joints.
Intervertebral discs.
Several groups of ligaments.
What are the distinguishing features of cervical vertebrae?
Bifid (two-pronged) spinous processes.
Holes in the transverse processes (transverse foramen).
Oval-shaped bodies.
Triangular vertebral foramen.
What are the distinguishing features of thoracic vertebrae?
Long, sharp, downward-sloping spinous processes.
Additional articular facets.
Heart-shaped bodies.
Round vertebral foramen.
What are the distinguishing features of lumbar vertebrae?
Short, blunt spinous processes.
Extra-large oval-shaped bodies.
Triangular vertebral foramen.
What are the distinguishing features of sacral vertebrae?
Fused into the sacrum.
Triangular bone sitting in posterior midline.
Articulates with hip bones.
What are the distinguishing features of coccygeal vertebrae?
Fused to form the coccyx.
What is the most commonly fractured bone?
The clavicle.
Describe the shape of the clavicle. Is it palpable?
- Slender, S-shaped bone.
- Easily palpable in most individuals.
What does the clavicle articulate with and where?
- The manubrium of the sternum at its proximal end.
- The acromion of the scapula at its distal end.
What type of joints are the sternoclavicular joint and acromioclavicular joint?
Synovial joints.
Describe the shape, location and palpability of the scapula.
- Mostly flat but with some bony projections.
- Located on the posterior thorax.
- Some parts can be easily palpated through the skin.
What is the ridge of bone on the posterior surface of the scapula? What does the lateral end of this expand to form?
- The spine.
- Expands to form the acromion (articulates with lateral end of the clavicle).
What is the projection of bone just inferior to the acromion on the anterior surface of the scapula? What does this do?
The coracoid process - site of attachment for several muscles.
What comprises the pectoral girdle?
The clavicle, scapula and the attached muscles.
What is the name of the shallow fossa on the lateral aspect of the scapula? What does this articulate with?
The glenoid fossa - articulates with the proximal humerus (a poor fit).
Describe the humerus.
The long bone of the arm, has a shaft and an expanded proximal and distal end.
Describe the shoulder/glenohumeral joint.
A poor fit which increases the range of movement possible at the shoulder but compromises the stability of the joint.
What does the head of the humerus articulate with?
The glenoid fossa of the scapula.
What is the name of the bony projection on the proximal humerus? What does it do?
The greater tubercle - an important site for muscle attachments.
What is immediately distal to the smooth head of the humerus?
A groove which is the position of the anatomical neck of the humerus.
What is the name of the smaller bony projection on the anterior humerus? What does it do?
The lesser tubercle - also a site of muscle attachment.
What happens to the humerus just distal to the tubercles? What is this region then called?
- The bone narrows and becomes continuous with the shaft.
- Called the surgical neck.
Why is the surgical neck clinically important?
Commonly fractured, especially in the elderly.
What nerve runs close to the surgical neck region of the humerus?
The axillary nerve.
What is the name of the slight protuberance on the upper lateral aspect of the humeral shaft? What does it do?
- The deltoid tuberosity.
- Site of attachment for the deltoid muscle.
What is the radial (spiral) groove?
Marks the path of the radial nerve over the posterior aspect of the humeral shaft. Radial nerve runs along a spiral route.
What are the 5 movements of the scapula?
- Protraction.
- Retraction.
- Elevation.
- Depression.
- Rotation.
What is the key muscle involved in protraction of the scapula?
The serratus anterior.
What are the 2 large and superficial muscles of the posterior pectoral girdle (connect the scapula to the vertebral column)?
The trapezius and latissimus dorsi.
What does the latissimus dorsi attach to?
The anterior aspect of the proximal humerus, not the scapula.
What are the 3 smaller and deeper muscles of the posterior pectoral girdle (connect the scapula to the vertebral column)? What are they attached to?
- Levator scapulae, rhomboid major and rhomboid minor.
- Attach to the medial border of the scapula and to the vertebral column.
How does the trapezius move the scapula?
Rotation, and individually: the upper part elevates, middle part retracts, and the lower part depresses the scapula.
How does the latissimus dorsi move the humerus?
Extends, adducts, and medially rotates the humerus.
How does the levator scapulae move the scapula?
Elevates.
How does the rhomboid major move the scapula?
Retracts.
How does the rhomboid minor move the scapula?
Retracts,
What is the origin of a muscle?
The more ‘fixed’ or stable bone.
What is the insertion point of a muscle?
The bone that moves when the muscle contracts.
What is the origin of the trapezius?
Skull, cervical and thoracic vertebrae.
What is the insertion of the trapezius?
Clavicle and scapula (spine and acromion).
What is the origin of the latissimus dorsi?
Lower thoracic vertebrae.
What is the insertion of the latissimus dorsi?
Humerus - proximal and anterior.
What is the origin of the levator scapulae?
Upper cervical vertebrae.
What is the insertion of the levator scapulae?
Scapula - medial border.
What is the origin of the rhomboid minor?
C7 and T1 vertebrae.
What is the insertion of the rhomboid minor?
Scapula - medial border.
What is the origin of the rhomboid major?
Thoracic vertebrae.
What is the insertion of the rhomboid major?
Scapula - medial border.
What nerves supply most of the muscles of the posterior pectoral girdle?
Branches that arise from the brachial plexus - a complex network of nerves that innervate the upper limb.
What innervates the trapezius?
The accessory nerve (CN XI).
What innervates the latissimus dorsi?
A branch of the brachial plexus called the thoracodorsal nerve.
What type of joint is the shoulder (glenohumeral) joint?
Synovial ball and socket joint.
What are the 7 possible movements at the shoulder joint?
- Flexion.
- Extension.
- Abduction.
- Adduction.
- Internal (medial) rotation.
- External (lateral) rotation.
- Circumduction.
What is the most commonly dislocated joint in the body?
The shoulder joint.
How many muscles attach the scapula to the humerus? What are they called?
6
- Deltoid.
- Supraspinatus.
- Infraspinatus.
- Subscapularis.
- Teres minor.
- Teres major.
Which 4 muscles work together to provide stability to the shoulder joint? What are they referred to as?
- Supraspinatus.
- Infraspinatus.
- Subscapularis.
- Teres minor.
- Known as the rotator cuff.
Describe the deltoid muscle.
- Large muscle over the lateral aspect of the shoulder.
- Attaches humerus to lateral part of the clavicle and to the spine of the scapula.
- Gives the shoulder its rounded contour.
- Inserts onto humerus at the deltoid tuberosity.
What does the deltoid act as?
- A powerful abductor of the shoulder joint, though it cannot initiate abduction - take s over at 15 degrees.
- Also contributes to flexion and extension of the shoulder.
What innervates the deltoid?
The axillary nerve.
Describe the teres major.
- Arises from posterior aspect of the scapula.
- Tendon slots underneath the humerus and inserts onto the anterior aspect of the humerus.
What does the teres major act as?
An internal rotator and adductor of the shoulder joint.
What do the supraspinatus, infraspinatus, teres minor and subscapularis muscles attach?
The scapula to the tubercles of the humerus.
What does the supraspinatus act as?
Abductor of the shoulder joint - first 15 degrees.
What does the infraspinatus act as?
External rotator of the shoulder joint.
What does the teres minor act as?
External rotator of the shoulder joint.
What does the subscapularis act as?
Internal rotator of the shoulder joint.
The tendons of which 3 muscles fuse with the fibrous capsule that surrounds the shoulder joint?
The supraspinatus, infraspinatus, and teres minor.
What is the origin of the deltoid?
Spine and acromion of the scapula, and the clavicle.
What is the insertion of the deltoid?
Deltoid tuberosity of the humerus.
What is the origin of the teres major?
Posterior surface of the scapula, inferior part of the lateral border.
What is the insertion of the teres major?
Anterior humerus.
What is the origin of the supraspinatus?
Supraspinous fossa of the scapula.
What is the insertion of the supraspinatus?
Greater tubercle of humerus - superior facet.
What is the origin of the infraspinatus?
Infraspinous fossa of the scapula.
What is the insertion of the infraspinatus?
Greater tubercle of humerus - middle facet.
What is the origin of the teres minor?
Lateral border of the scapula.
What is the insertion of the teres minor?
Greater tubercle of humerus - inferior facet.
What is the origin of the subscapularis?
Subscapular fossa of the scapula.
What is the insertion of the subscapularis?
Lesser tubercle of humerus.
What is impingement?
When the supraspinatus tendon can become inflamed and pinched between the acromion and humerus during movement of the shoulder.
Describe the quadrilateral space.
Square-shaped space bound by: teres minor above, teres major below, long head of the triceps medially, and surgical neck of the humerus laterally.
What travels through the quadrilateral space?
The axillary nerve.
What provides stability to the shoulder joint?
- The rotator cuff.
- The glenoid labrum
- Ligaments reinforcing the capsule.
- The tendon of biceps brachii.
How many boundaries does the axilla have? Describe them.
6
- Anterior wall: pectoralis major and minor.
- Posterior wall: subscapularis, teres major and latissimus dorsi.
- Lateral wall: proximal humerus.
- Medial wall: serratus anterior and thoracic wall.
- Apex: first rib, clavicle and scapula.
- Base: skin and fascia between thoracic wall and arm.
What are 5 important structures in the axilla?
- Fat.
- Lymph nodes.
- Axillary artery.
- Axillary vein.
- Brachial plexus.
When does the subclavian artery become the axillary artery?
After it passes over the lateral border of the first rib.
When does the axillary artery become the brachial artery?
As it crosses over the inferior border of the teres major.
When does the axillary vein become the subclavian vein?
At the lateral border of the first rib.
What forms the axillary vein?
The union of the brachial veins with the basilic vein, cephalic vein also joins the axillary vein in the axilla.
Which type of shoulder dislocation is more common?
Anterior dislocation (humeral head ends up anterior to the glenoid fossa).
What can shoulder dislocation cause?
Injury to the axillary nerve.
What can cause shoulder dislocation?
Blunt force trauma, such as a fall.
What can cause a rotator cuff injury?
Acute trauma or repetitive use.
When are tears of the rotator cuff usually painful?
At rest and on movement.
What 2 nerves are at risk when removing axillary lymph nodes?
- The long thoracic nerve.
- The thoracodorsal nerve.
What does the long thoracic nerve innervate?
The serratus anterior.
What does the thoracodorsal nerve innervate?
The latissimus dorsi.
What 2 prominences form from the shaft of the humerus distally?
The medial and lateral epicondyles.
What are the 2 further prominences of the distal humerus? What do these articulate with?
- The trochlea (articulates with the trochlear notch of the ulna at the elbow joint).
- The capitellum (articulates with the head of the radius at the elbow joint).
What separates the arm into anterior and posterior compartments?
The intermuscular septa
How many muscles does the anterior compartment of the arm contain? What are these called? What do they act as? What are they innervated by?
- 3.
- Biceps brachii, brachialis and coracobrachialis.
- Act as flexors.
- Innervated by the musculocutaneous nerve.
Describe the structure of the biceps brachii.
- Lies most superficially.
- Two heads: long head and short head.
- Proximally, both heads attach to scapula (long -> supraglenoid tubercle, short -> coracoid process).
- Long head pierces capsule and helps stabilise the joint.
- 2 muscle bellies converge to their insertion via a common tendon onto the radial tuberosity of the radius.
What does the biceps brachii act as?
- A flexor of the elbow joint, and also contributes to flexion of the shoulder joint as it crosses the joint.
- A powerful supinator of the forearm when the elbow if flexed
Describe the structure of the brachialis.
- Lies deep to biceps.
- Proximally, attached to anterior aspect of distal half of the shaft of the humerus.
- Crosses the elbow joint to insert distally upon the ulna tuberosity.
What does the brachialis act as?
A powerful flexor of the elbow joint, but does not act upon the shoulder joint as it does not cross the joint.
Describe the structure of the coracobrachialis.
- Deep and much smaller muscle.
- Attaches proximally to the coracoid process of the scapula and distally to the medial aspect of the middle part of the humerus.
What does the coracobrachialis act as?
A weak flexor of the shoulder joint as it crosses the joint.
How many muscles does the posterior compartment of the arm contain? What are these called?
- 1.
- The triceps brachii.
Describe the triceps brachii.
- Has 3 muscle bellies/heads, all of which converge via a common tendon onto a single insertion point - the olecranon of the ulna.
What does the triceps brachii act as?
Extender of the elbow when it contracts, as it crosses the posterior aspect of the elbow joint.
What are the 3 heads of triceps called, and where do they originate?
- Long head: infraglenoid tubercle of the scapula.
- Lateral head: posterior humerus, proximal to the radial groove.
- Medial head: posterior humerus, distal to the radial groove.
What is the long head of the triceps brachii able to act as?
Contributes to extension of the shoulder joint in addition to extension of the elbow joint, as it is attached to the scapula.
What innervates the 3 parts of the triceps?
The radial nerve.
Which spinal nerves form the brachial plexus? Which type of fibres do these carry?
- C5, C6, C7, C8, and T1.
- Sensory and motor fibres.
Describe the roots of the brachial plexus.
C5 -> T1 spinal nerves exit the spinal cord and become the brachial plexus (they are found in the neck).
Describe the trunks of the brachial plexus.
Also located in the neck, formed from the roots:
- C5 and C6 = superior trunk.
- C7 = middle trunk.
- C8 and T1 = inferior trunk.
Describe the divisions of the brachial plexus.
Each trunk divides into an anterior and a posterior division under the clavicle.
Describe the cords of the brachial plexus.
Named relative to their position around the second part of the axillary artery.
- Anterior division of superior and middle trunks combine = lateral cord.
- Anterior division of inferior trunk continues = medial cord.
- Posterior divisions of all trunks combine = posterior cord.
Describe the branches of the brachial plexus.
Located in the axilla, formed by cords.
- Axillary: branch from posterior cord.
- Radial: continuation of posterior cord.
- Musculocutaneous: branch from lateral cord.
- Ulnar: branch from the medial cord.
- Median: formed by branches from lateral and medial cords.
- Gives rise to other nerves, but do not need to know their origins, only the 5 terminal nerves above.
What does the axillary nerve innervate?
- Deltoid and teres minor, and a small region of skin over the upper lateral arm.
What cord is the axillary nerve a branch of? Which spinal nerves does it contain fibres from?
- Branch of the posterior cord.
- Fibres from C5 and C6.
Where does the axillary nerve run? When is it vulnerable?
- Runs close to the surgical neck of the humerus.
- Vulnerable to injury in fractures of the surgical neck of the humerus, or dislocations of the humeral head.
What does the radial nerve innervate?
- Triceps in the posterior arm, muscles in the posterior component of the forearm. Also innervates the regions of the skin over the arm, forearm and hand.
What cord is the radial nerve a continuation of? Which spinal nerves does it contain fibres from?
- Continuation of the posterior cord.
- Fibres from C5 -> T1.
Where does the radial nerve run? When is it vulnerable?
- Along the radial (spiral) groove on the posterior surface of the humerus.
- Vulnerable in mid-shaft fractures of the humerus.
What does the musculocutaneous nerve innervate?
- The 3 muscles of the anterior compartment of the arm: biceps brachii, brachialis and coracobrachialis.
What cord is the musculocutaneous nerve a branch of? Which spinal nerves does it contain fibres from?
- Arises from the lateral cord.
- Fibres from C5 -> C7.
Where does the musculocutaneous nerve run? When is it vulnerable?
- Continues as a sensory nerve that innervates a region of skin over the lateral forearm, after supplying the 3 muscles.
- Rarely injured in isolation.
What does the median nerve innervate?
- Most of the muscles of the anterior forearm, and small muscles of the thumb. Also provides sensory innervation to the skin over the lateral aspect of the palm of the hand and over the lateral digits.
What cord is the median nerve a branch of? Which spinal nerves does it contain fibres from?
- Formed from both the lateral and medial cords.
- Normally, fibres from C6 -> T1, but in some individuals, fibres from C5 -> T1.
Where does the median nerve run? When is it vulnerable?
- Crosses the anterior aspect of the elbow, in a region called the cubital fossa.
- Most vulnerable in the arm.
What does the ulnar nerve innervate?
- Most of the small muscles in the hand, also innervates skin over the medial aspect of the hand and medial digits.
What cord is the ulnar nerve a continuation of? Which spinal nerves does it contain fibres from?
- Continuation of the medial cord.
- Fibres from C8 -> T1.
Where does the ulnar nerve run? When is it vulnerable?
- Lies in a superficial position behind the medial epicondyle.
- Vulnerable to injury behind the medial epicondyle.
What can injury of the axillary nerve result in?
- Weakness or paralysis of deltoid (presents functionally as difficulty abducting the shoulder).
- Altered sensation or numbness over the upper lateral arm.
What can injury of the radial nerve result in?
- Weakness and paralysis of muscles that are innervated downstream of the point of injury.
- Usually affects movement of the wrist.
What can injury of the ulnar nerve result in?
- Motor impairments of the hand and sensory impairments in the hand.
- Tingling and pain in the same regions of the hand are possible if the elbow is knocked.
How does Erb’s Palsy (upper brachial plexus injury) typically present?
- Paralysis of the lateral rotators of the shoulder, and extensors of the wrist.
- Affected limb appears medially rotated with the wrist flexed.
What typically causes Erb’s Palsy?
- Trauma e.g. being thrown off a motorbike or horse, or in new-borns if the shoulder becomes stuck during delivery.
- Involves C5 -> C6/7.
How does Klumpke’s Palsy (lower brachial plexus injury) typically present?
- Paralysis of the small muscles of the hand.
What typically causes Klumpke’s Palsy?
- Trauma e.g. if a baby’s arm is pulled forcefully superiorly to aid delivery.
- Involved C8 -> T1.
How does Horner’s syndrome present?
- Triad of ptosis, miosis and anhidrosis on one side of the face.
What typically causes Horner’s syndrome?
- When the sympathetic nerve supply to the face is interrupted.
- A brachial plexus injury affecting the T1 nerve root may result in Horner’s syndrome, as T1 carries sympathetic fibres to the face.
What is brachial plexus block?
- A form of regional anaesthesia, can be used as an alternative to general anaesthesia for surgery of the upper limb.
- Local anaesthetic is infiltrated around the nerves of the plexus, which anaesthetises the upper limb, under ultrasound guidance.
What are the 2 bones of the forearm? How are they connected?
- Radius and ulna.
- Interosseous membrane.
How do the radius and ulna articulate with the humerus?
- Trochlea notch of ulna articulates with trochlea of humerus.
- Radial head articulates with capitellum of humerus.
What movement can occur at the elbow joint?
Flexion and extension.
Where do the radius and ulna articulate with each other?
Proximal and distal radioulnar joints.
What movement do the proximal and distal radioulnar joints allow? How? Which muscles are involved?
- Pronation and supination of the forearm and hand.
- Radius pivots around the ulna.
- Muscles in the anterior arm, and the anterior and posterior forearm.
What does the radius articulate with distally?
Two carpal bones of the wrist (scaphoid and lunate), forming the radiocarpal joint.
What movement is possible at the radiocarpal joint? Which muscles are involved?
- Flexion, extension, abduction and adduction.
- Muscles in the anterior and posterior foraerm.
What is the name of the bulky process on the posterior proximal ulna? What does this fit into? What does this allow?
- The olecranon.
- Fits in the olecranon fossa of the posterior distal humerus.
- Allows full extension.
What is the name of the process on the anterior proximal ulna? What does this fit into and when does this fit?
- Coronoid process.
- Fits in the coronoid fossa of the anterior distal humerus when we flex our elbow fully.
Where can the radial tuberosity be found? What is it’s relevance?
- Roughened lump near the proximal end of the radius, distal to the head and neck.
- Where the biceps brachii tendon inserts onto the radius.
What are the distal protrusions on both the radius and ulna called which are often implicated in fractures?
Styloid processes.
What type of joint is the elbow joint?
Synovial hinge joint.
Give 2 factors that increase the stability of the elbow joint.
- Trochlea notch of the ulna forms a deep recess which the trochlea of the humerus fits into very well.
- Coronoid process and olecranon of the ulna ‘pinch’ the trochlea of the humerus to increase stability.
What reinforces the joint capsule of the elbow joint?
Medial (ulnar) and lateral (radial) collateral ligaments.
What type of joint are the proximal and distal radioulnar joints?
Synovial, pivot-type joints.
Which ligament wraps around the radial neck and holds the radial head in place whilst attaching to the ulna to allow radial rotation around the ulna?
The annular ligament.
How many bones is the carpus comprised of? How are these arranged?
- 8.
- 2 rows of 4 bones.
Give the proximal row of carpal bones, from lateral to medial.
Scaphoid, lunate, triquetrum and the pisiform.
Which is not a true carpal bone and why?
- The pisiform.
- Small bone that develops in the tendon of flexor carpi ulnaris.
Give the distal row of carpal bones, from lateral to medial.
Trapezium, trapezoid, capitate and the hamate.
Which is the largest carpal bone?
Capitate.
What is the name of the anterior bony process on the hamate?
The hook.
What type of joint is the radiocarpal joint?
A condyloid synovial joint.
What type of joints are the intercarpal joints?
Synovial joints.
Which bones are located distal to the carpus?
The metacarpals.
What are the bones of the digits called? How many are there in each digit?
- Phalanges
- 3 in each finger, 2 in the thumb.
Where can the cubital fossa be found?
Anterior to the elbow joint.
What else may the cubital fossa be referred as?
The antecubital fossa / ACF.
What forms the lateral border of the cubital fossa?
The brachioradialis (posterior forearm muscle).
What forms the medial border of the cubital fossa?
The pronator teres (anterior forearm muscle).
What forms the superior border of the cubital fossa?
An imaginary line between the medial and lateral epicondyles of the humerus.
Is the apex of the cubital fossa distal or proximal? Which direction is it pointing?
Distal, pointing towards the hand.
Give 5 contents of the cubital fossa.
- The tendon of the biceps brachii.
- The bicipital aponeurosis.
- The brachial artery.
- The median nerve.
- The radial nerve.
What happens to the brachial artery deep in the cubital fossa?
Bifurcates into its terminal branches - the radial and ulnar arteries.
Give 3 superficial veins located in the subcutaneous tissue over the cubital fossa.
- Cephalic cubital vein.
- Basilic cubital vein.
- Median cubital vein.
Give 3 clinical relevancies of the bones/joints of the forearm and the cubital fossa.
- Radial head subluxation.
- Scaphoid fracture.
- Fracture of the distal radius.
What is radial head sublaxation? Which group is it most common in?
- Annular ligament is partially torn, and the radial head moves distally out of the ligament.
- Most common in young children, by being pulled up by their arm.
What is the risk of a scaphoid fracture?
Proximal part of the bone may be disconnected from the blood supply and death of this segment results - avascular necrosis.
Why is avascular necrosis a serious problem?
As the proximal scaphoid articulates with the distal radius at the wrist joint.
Who are distal radius fractures most common in? Why?
- Older people, particularly females.
- Osteoporosis is more common in these groups.
What usually causes a distal radius fracture?
FOOSH:
- Fall Onto OutStretched Hand.
How many muscles can be found in the anterior compartment of the forearm? How many layers can these be split into?
- 8 muscles.
- 3 layers: superficial, middle and deep.
What do most of the muscles in the anterior compartment act as?
Flexors of the wrist, fingers or thumb.
What nerve innervates most of the muscles of the anterior compartment?
Median nerve.
How many muscles are in the superficial layer of the anterior compartment? What are these called?
4:
- Pronator teres.
- Flexor carpi radialis.
- Palmaris longus.
- Flexor carpi ulnaris.
What are the superficial muscles of the anterior compartment attached to proximally?
The medial epicondyle of the humerus AKA the common flexor origin.
What is the action of the pronator teres?
Pronator of the proximal radioulnar joint.
What is the action of the flexor carpi radialis?
Flexes and abducts the wrist.
Describe the palmaris longus.
Small muscle belly but long, thin, easily recognisable tendon when present (approx 15% don’t have one).
Where does the tendon of the palmaris longus insert into?
The fascia of the palm of the hand.
What is the action of the flexor carpi ulnaris?
Flexes and adducts the wrist.
How many muscles can be found in the middle layer of the anterior compartment? What is it called?
1:
- Flexor digitorum superficialis.
How many tendons does the flexor digitorum superficialis give rise to?
Four.
Where do the tendons of the flexor digitorum superficialis travel to?
Beyond the wrist, into the hand and to the fingers (digits 2-5).
What is the action of the flexor digitorum superficialis?
Flexor of the digits.
Which muscles of the anterior compartment does the media nerve travel between?
The flexor digitorum superficialis and the flexor digitorum profundus.
How many muscles can be found in the deep layer of the anterior compartment? What are they called?
3:
- Flexor digitorum profundus.
- Flexor pollicis longus.
- Pronator quadratus.
How many tendons does the flexor digitorum profundus give rise to?
Four.
Where do the tendons of the flexor digitorum profundus travel to?
Into the hand and to the fingers (digits 2-5).
What is the action of the flexor digitorum profundus?
Flexor of the digits.
Describe the innervation of the flexor digitorum profundus.
- Lateral half of the muscle (which gives rise to the tendons that travel to the index and middle fingers) is innervated by the median nerve.
- Medial half of the muscle (which gives rise to the tendons that travel to the ring and little fingers) is innervated by the ulnar nerve.
What is the action of the flexor pollicis longus?
Flexor of the thumb.
What is the action of the pronator quadratus?
Pronates the distal radioulnar joint.
Which anterior forearm muscles are NOT flexors?
- Pronator teres.
- Pronator quadratus.
Which anterior forearm muscles are NOT innervated by the median nerve?
- Flexor carpi ulnaris.
- Flexor digitorum profundus.
How many muscles can be found in the posterior compartment of the forearm? How many layers can these be split into?
- 12.
- 2 layers: superficial and deep.
What is the action of most of the muscles of the posterior compartment?
Extensors of the wrist, digits or thumb.
What nerve innervates all of the muscles of the posterior compartment?
Radial nerve.
How many muscles are in the superficial layer of the posterior compartment of the forearm? What are these called?
7:
- Brachioradialis.
- Extensor carpi radialis longus.
- Extensor carpi radialis brevis.
- Extensor digitorum.
- Extensor digiti minimi.
- Extensor carpi ulnaris.
- Anconeus.
What are the superficial muscles of the posterior compartment attached to proximally (generally)?
The lateral epidcondyle of the humerus AKA the common extensor origin.
Describe the brachioradialis.
- Located on the boundary of the anterior and posterior compartments of the forearm.
- Originates from humerus, proximal to lateral epicondyle, inserts on the distal radius.
What is the action of the brachioradialis?
Weak flexor of the elbow joint (hence functions as an anterior compartment muscle).
Where are the extensor carpi radialis longus and brevis located in the posterior compartment?
On the radial side.
What is the action of the extensor carpi radialis longus and brevis?
Extend and abduct the wrist.
Where does the extensor carpi radialis longus insert onto?
The 2nd metacarpal.
Where does the extensor carpi radialis brevis insert onto?
The 3rd metacarpal.
What is the action of the extensor digitorum?
Extends the digits.
How many tendons does the extensor digitorum give rise to?
Four.
Where do the tendons on the extensor digitorum insert onto?
Dorsal aspects of the fingers (digits 2-5).
