Cubital fossa: boundaries, contents, muscles of the arm and forearm

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Contents

What is cubital fossa?

The cubital fossa is a triangular hollow space in front of the elbow joint and homologous to the popliteal fossa of the lower limb.

The lateral border is formed by the medial border of the brachioradialis muscle.
The medial border is bounded by the lateral border of the pronator teres muscle.
The base is formed by the imaginary horizontal line joining the front of the two epicondyles of the humerus.
Apex is formed by the meeting point of the lateral ( medial border of the brachioradialis muscle) and medial boundaries (lateral border of pronator teres muscle).
The roof is formed by Skin, Superficial fascia containing the median cubital vein, lateral & medial cutaneous nerve of the forearm. And Deep fascia, Bicipital aponeurosis.
The floor is formed by two muscles, they are; Brachialis (upper part) and Supinator muscle (lower part).

From medial to lateral (@MBBS).
- Median nerve
- Brachial artery
- Tendon of the Biceps brachii
- Superficial radial nerve

The cubital fossa is clinically important due to the following reasons,

Median cubital vein: it is a vein of choice for collecting blood samples and also giving an intravenous injection of drugs.
Brachial pulses: The easily felt medial to the biceps tendon in the body, and for recording the blood pressure in the body
Supracondylar fracture of the humerus: brachial artery and median nerve are vulnerable in this condition

Various structures are present on the anterior compartment of the arm, they are

Muscles: Biceps brachii, coracobrachialis, and brachialis.
Nerve: Musculocutaneous nerve.
Artery: Brachial artery
Other following nerves also pass through the anterior compartment of the arm, such as; Median nerve, ulnar nerve, radial nerve.

Origin, insertion, nerve supply (NS), and action (activity):

Muscle	Origin	Insertion	Nerve supply	Actions
Biceps brachii	The short head originates from the tip of the coracoid process of the scapula & the long head from the supraglenoid tubercle of the scapula.	Insertion occurs in a posterior rough part of the radial tuberosity	Musculocutaneous (C5, C6, and C7)nerve.	Supination of the forearm when the elbow is flexed and flexion of the forearm when the elbow is extended
Coracobrachialis	Originate from the tip of the coracoid process of the scapula along with short head of the biceps muscle	Insertion occurs in the middle one-third of the medial border of the humerus	Musculocutaneous nerve	Role on flexion and adduction of the arm occur.
Brachialis	Originate from the lower half of the anterior surface of the humerus	Insertion occurs on the anterior surface of the coronoid process of the ulna including ulnar tuberosity	Musculocutaneous nerve (medial 2/3) Radial nerve(lateral 1/3)	Help in flexion of the forearm

Origin, insertion, nerve supply (NS), and action (activity) of the muscles

Various structures are present on the posterior compartment of the arm, they are

Muscle: Triceps brachii
Nerve: Radial nerve
Artery: profunda brachii artery
Structures pass-through this compartment is following such as ulnar nerve and ulnar collateral arteries

Triceps brachii: Origin, insertion, nerve supply (NS), and action (Activity) of muscle

Origin:
- Long head: from the infraglenoid tubercle of the humerus.
- Lateral head: The lateral head of the triceps brachii muscle originates from an oblique ridge above the spiral groove on the upper part of the posterior surface of the shaft of the humerus.
- Medial head: The triceps brachii muscle origin from the posterior surface of the lower half of the shaft humerus below the spiral groove.
Insertion:
- The common tendon of the triceps muscle is inserted into the posterior part of the superior surface of the olecranon process of the ulna.
Nerve supply: radial (C7, C8) nerve.
Action: extensor of the elbow and supports the head of the humerus during hyperabduction of the arm.