Flashcards in Session 3 Anatomy Deck (27)
Describe the Brachial Artery
Ends in the cubital fossa oppsotie the neck of radius under cover of the bicipital aponeurosis, divides into the radial and ulnar arteries.
At first lies medial to the humerus then passes anterior to the medial supra-epicondylar ridge and trochlea then accompanies median nerve (laterally).
Gives off many branches in particular the profunda brachii (accompanies radial nerve along the radial groove posteriorly)
Profunda brachii terminates into the radial and ulnar collateral arteries which participated the peri-articular anastomoses around the elbow.
Why is the Peri-Articular anastomoses important around the elbow?
Resulting collateral circulation allows blood to reach the forearm when flexion of the elbow compromises flow through the terminal part of the brachial artery
Describe the course of the Cephalic Vein
A main superficial vein of the upper limb, originates from the lateral aspect of the subcutaneous tissue on the dorsum of the hand from mother dorsal venous network.
Ascends in the subcutaneous tissue along the lateral border of the worst and anterolateral surface of proximal forearm and arm.
Courses superiorly between the deltoid and Pectoralis major muscles along the deltopectoral groove and then enters the clavipectoral triangle
joins the terminal part of the axillary vein.
Describe the course of the basilic vein
Ascends in the subcutaneous tissue from the medial end of the dorsal venous network along the medial side of the forearm and the inferior part of the arm.
It then passes deeply near the junction of the middle and inferior thirds of the arm, piercing the brachial fascia and running superiorly parallel to the brachial artery and the medial cutaneous nerve of the forearm to the axilla.
Here it merges with the venae comitantes (accompanying nerves) of the axillary artery to form the axillary vein.
What is the Median Cubital Vein?
Anterior to the elbow, the cephalic vein communicates with the median cubital vein which passes obliquely across the anterior aspect of the elbow in the cubital fossa and joins the basilic vein.
What is the Median Antebrachial vein?
Median vein of the forearm - highly variable
Begins at the base of the dorsum of the thumb, curves around the lateral side of wrist and ascends in the middle of the anterior aspect of the forearm between the cephalic and the basilic veins,
The median Antebrachial vein sometimes divides into a median basilic vein which joins the basilic vein and a median cephalic vein which joins the cephalic vein.
Describe the deep veins of the arm
Paired deep veins accompany the brachial artery, collectively known as the brachial vein
Their frequent connections encompass the brachial artery, forming an anastomotic network within a common vascular sheath.
The pulsations of the brachial artery help move the blood in this venous network,
Brachial vein begins at the elbow by union of the accompanying veins of the ulnar and radial arteries and ends by merging with the basilic vein to form the axillary vein
Describe the Musculocutaneous Nerve
Begins opposite the inferior border of the pec minor, pierces the coracobrachialis and continues distally between the biceps and the brachialis.
It supplies BBC and emerges lateral to the biceps as the lateral cutaneous nerve of the forearm.
It becomes truly subcutaneous when it pierces the deep fascia proximal to the cubital fossa to course initially with the cephalic vein in the subcutaneous tissue.
After crossing the anterior aspect of the elbow, it supplies the skin of the lateral aspect of the forearm.
Describe the Radial Nerve
Enters the arm posterior to the brachial artery, medial to the humerus and anterior to the long head of the triceps. Gives branches to long head and medial head.
Descends inferolaterally with profunda brachii - radial groove
Branch of the radial nerve to lateral head of triceps rises within the radial groove.
When it reaches the lateral border of the humerus, the radial nerve pierces the lateral intermuscular septum and continues inferiorly in the anterior compartment of the arm between the brachialis and the brachioradialis.
Passes anterior to the lateral epicondyle. Radial nerve divides into deep and superficial branches. Deep branch is entirely muscular and articular to its distribution. Superficial branch of the radial nerve is entirely cutaneous in its distribution supplying sensation to the dorsum of the hands and fingers.
Describe the Ulnar Nerve
Passes distally from the axilla anterior to the insertion of the teres major and long head of the triceps, on the medial side of the brachial artery.
Descends between the medial intermuscular septum and the medial head of the triceps
Passes posterior to the medial epicondyle (funny bone) and medial to the olecranon to enter the forearm
Ulnar nerve is superficial, easily palpable and vulnerable to injury. Like the median nerve the ulnar nerve had no branches in the arm but it also supplies articular branches to the elbow joint.
Describe the Median Nerve
Runs distally in the arm on the lateral side of the brachial artery until it reaches the middle of the arm where it crosses to the medial side and contacts the brachialis.
Then descends into the cubital fossa where it lies deep to the bicipital aponeurosis and median cubital vein.
Median nerve has no branches in the axilla or arm but it does supply articular branches to the elbow joint.
What are the contents of the cubital fossa?
Medial to Lateral:
Brachial artery (+ deep accompanying veins)
Biceps brachii tendon
Superficially in the subcutaneous tissue overlying the cubital fossa are the median cubital vein, lying anterior to the brachial artery and the medial and lateral cutaneous nerves of the forearm, related to the basilic and cephalic veins.
Describe the sternoclavicular joint
Saddle type of synovial joint but functions as a ball-and-socket,
Divided into two compartments by an articular disc
The disc is firmly attached to the anterior and posterior sternoclavicular ligaments, thickening of the fibrous layer of the joint capsule as well as the interclavicular ligament.
Articular disc serves as a shock absorber of forces transmitted along the clavicle from the upper limb so dislocation of the clavicle is rare but fracture is common.
SC joint is the only articulation between the upper limb and the axial skeleton.
Describe the acromioclavicular joint
Plane type of synovial joint
Acromial end of clavicle articulates with the acromion of the scapula. The articular surfaces, covered with Fibrocartilage, are separated by an incomplete wedge-shaped articular disc.
The Sleeve-like relatively loose fibrous layer of the joint capsule is attached to the margins of the articular surfaces.
A synovial membrane lines the fibrous layer.
Although relatively weak, the joint capsule is strengthened superiorly by fibres of the trapezius
Integrity of the joint is maintained by extrinsic ligaments, distant from the joint itself.
Describe Injury to Musculocutaneous Nerve
Although uncommon in this protected position, injury to the nerve in the axilla is typically inflicted by a weapon such as a knife.
Results in the paralysis of BBC muscles. Weaker flexion at the shoulder joint due to long head of the biceps brachii and coracobrachialis being affected. Consequently flexion of the elbow joint and supination of forearm are weakened but still possible because the brachioradialis and supinator muscles.
Loss of sensation may occur on the lateral surface of the forearm supplied by the lateral Antebrachial cutaneous nerve (forearm continuation of the Musculocutaneous nerve)
Describe injury to the radial nerve
Injury to the nerve suitor to the origin of its branches to the triceps brachii results in paralysis of the triceps, brachioradialis, supinator and extensor muscles of the wrist and fingers.
Loss of sensation in areas of skin supplied by nerve,
When the nerve is injured in the radial groove, triceps is not completely paralysed but only weakened (only medial head is affected) however the muscles in the posterior compartment of the forearm that are supplied by more distal branches of the nerve are paralysed.
What is the classic characteristic of radial nerve injury?
Wrist drop - inability to extend the wrist and the fingers at the MCPs. Instead, the relaxed wrist assumes a partly flexed position owing to unopposed tonus of flexor muscles and gravity.
Explain about Myotomes
Somatic motor fibres travelling in the same fixed peripheral nerves that convey sensory fibres to the cutaneous nerves transmit impulses to voluntary muscles of the upper limb.
The unilateral embryological mass (and derived muscle) receiving innervations from a single spinal cord segment or spinal nerve constitutes a myotome.
Most muscles are made up of more than one myotome and multiple spinal cord segments are usually involved in producing the movement of the upper limb. E.g. The intrinsic muscles of the hand constitute a single myotome.
How would you test the biceps reflex?
Support the patient's arm with it flexed at roughly 60 degrees, placing your thumb over the biceps tendon and hitting your thumb with the tendon hammer.
It is vital to get your patient to relax as much as possible and for you to take the entire weight of their arm.
How would you test the triceps reflex?
Rest patient's arm across their chest and hit the triceps tendon (with tendon hammer) just proximal to the elbow
How would you test the supinator reflex?
With their arm rested on the abdomen, locate the supinator tendon as it crosses the radius, place three fingers on it and hit the fingers (with tendon hammer)
How would you palpate the brachial artery?
Used in measuring blood pressure
Brachial artery lies medial to the humerus where its pulsations are palpable in the medial bicipital groove just below the bend of the elbow - proximal to medial epicondyle.
Describe an avulsion fracture of the greater tubercle of the humerus
Most commonly seen in middle-aged and elderly people
A small part of the tubercle is avulsed.
Usually results from a fall on the acromion.
In younger people an avulsion fracture of the greater tubercle usually results from a fall on the hand when the arm is abducted. Muscles especially subscapularis that remain attached to the humerus pull the limb into medial rotation.
Describe a transverse fracture of the shaft of the humerus
Frequently results from a direct blow to the arm
The pull of the deltoid muscle carries the proximal fragment laterally.
Indirect injury resulting from a fall on the outstretched hand may produce a spiral fracture of the humeral shaft.
Overriding of the oblique ends of the fractured bone may result in foreshortening.
Because the humerus is surrounded by muscles and has a well-developed periosteum, the bone fragments usually unite well.
Describe an intercondylar fracture of the humerus
Usually results from a fall on the flexed elbow,
The olecranon of the ulna is driven like a wedge between medial and lateral parts of the condyle of the humerus, separating one or both parts from the humeral shaft.
Describe venepuncture in cubital fossa
Median cubital vein is most commonly selected.
A tourniquet is placed around the mid arm to distend the veins in the cubital fossa.
Once the vein is punctured, the tourniquet is removed so that when the needle is removed, the vein will not bleed excessively.
Median cubital vein is also a site for the introduction of cardiac catheters to secure blood samples from the great vessels and chambers of the heart. These veins may also be used for coronary angiography.