Textbook Of Anatomy Upper Limb And Thorax Pdf Download

[Silvana Fleischacker]

Everwondered what the differences are between us humans and animals regarding the upper limb? One of them is certainly our ability to high five each other when we ace our anatomy exam. Of course, there are many more functions and movements that our upper extremity offers to us, and this is all due to its perfect anatomy that is designed to allow a large degree of mobility.

The shoulder is where the upper limb attaches to the trunk. Its most important part is the glenohumeral joint; formed by the humerus, scapula and clavicle. The humerus anatomy is a must-know before any discussion on the glenohumeral joint, and you can learn everything about it in our learning materials.

The shoulder joint is reinforced with two groups of muscles, superficial and deep. Superficial muscles include the deltoid and the trapezius, whereas the deep group contains the supraspinatus, infraspinatus, teres minor and subscapularis (rotator cuff) muscles.

Find out everything about shoulder anatomy through our fun and engaging educational content. Also, we have prepared a special quiz for you to solidify your knowledge about the upper limb anatomy. Take the upper extremity anatomy quiz and learn more about the bones, joints, muscles and vessels of the upper extremity!

The muscles are grouped into anterior and posterior compartments by the septa that attach to the humerus. The anterior compartment contains the coracobrachialis, brachialis and biceps brachii muscles. While the posterior compartment contains only one muscle, the triceps brachii.

Last but not least, is the neurovascular compartment. Every single structure of the arm is innervated by the brachial plexus, a network of nerves that originate from the C5-T1 spinal nerves. Arterial blood comes from the brachial artery, which arborizes on its way down the arm giving many branches for the supply of the structures of the arm.Learn more about the nerves of the upper limb with Kenhub.

Here comes the part that most students consider the hardest. The twenty muscles, and two bones (radius and ulna), of the forearm. When in anatomical position (supination), the radius is found laterally while the ulna is medially in the forearm. This is why while studying the forearm anatomy, you'll often encounter with terms radial, meaning lateral, and ulnar referring to the medial part of the forearm.

Radius and ulna articulate with each other by proximal and distal radioulnar joints and also contribute to the elbow and wrist joints. Thanks to the common sense of Mother Nature while designing these two bones, we can perform movements uniquely seen in the forearm such as supination and pronation.

The muscles of the forearm are grouped into anterior and posterior compartments, with the anterior compartment containing mostly flexors, and the posterior, extensors. Both the anterior and posterior compartments can be further divided into superficial and deep layers.

We know that reading about twenty muscles, two compartments and four layers can be monotonous, so we have designed these study units with video tutorial and integrated quizzes to make this topic more interesting, and your life easier!

The hand is probably the finest product of human evolution from the aspect of our body mechanics. The hand anatomy enables us various movements, with the spectrum ranging from rough movements, such as smashing a mosquito, to the finest movements like playing the guitar, drawing, or writing calligraphically.

The bony background of the hand is very interesting. The carpus contains 8 bones, the metacarpus are comprised of 5, and the digits have 14 bones. The bones within the carpus are small, irregularly shaped, and have such curious names that you may like to choose one for your instagram account: scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate and hamate bones.

The musculocutaneous nerve is a terminal branch of the lateral cord of the brachial plexus that carries fibers of cervical spinal nerves five through seven (i.e., C5, C6, and C7). The musculocutaneous nerve leaves the axilla and rapidly descends into the coracobrachialis muscle fibers.

The musculocutaneous nerve supplies the biceps brachii and brachialis muscles as it descends between them within the anterior compartment of the arm. The musculocutaneous nerve changes names as it passes lateral to the tendon of the biceps brachii, where it changes its name to the lateral cutaneous nerve of the forearm, also known as the lateral antebrachial cutaneous nerve. This nerve mainly provides motor innervation to the anterior compartment of the arm and returns cutaneous sensation from the lateral forearm.

The brachial plexus is the complex arrangement of nerves originating from the ventral roots of four cervical and one thoracic spinal nerve (C5-T1). The brachial plexus innervates numerous muscles and cutaneous regions of the upper limb, thorax, and back. The five ventral rami, or roots of the brachial plexus, rearrange into a superior, middle, and inferior trunk. These trunks form six divisions (three anterior and three posterior), which are continuous with a medial, posterior, and lateral cord. Along the course of the brachial plexus, 18 nerves arise, including five terminal branches. The musculocutaneous nerve (C5-7) is a terminal branch of the lateral cord. The musculocutaneous nerve innervates the three muscles of the anterior compartment of the arm: the coracobrachialis, biceps brachii, and brachialis muscles. It is also responsible for cutaneous innervation of the lateral forearm.

Throughout this portion of the arm, the nerve is found deep to the biceps brachii and superficial to the brachialis, and it gives off motor branches to these muscles along the way. Using the acromion process as the origin, the motor nerve branch points for the biceps brachii and brachialis were found to occur at an average distance of 13.0 cm and 17.5 cm along the course of the musculocutaneous nerve, respectively.[2] Having given off all of its motor fibers, the main trunk of the musculocutaneous nerve continues inferiorly. A few centimeters superior to the elbow joint, it then exits the space between the biceps brachii and brachialis muscles just lateral to the biceps brachii tendon. At this point, it is considered the lateral cutaneous nerve of the forearm.

The lateral cutaneous nerve of the forearm pierces the deep fascia superficially to gain access to the subcutaneous compartment. This terminal cutaneous branch of the musculocutaneous nerve gives off a volar and dorsal branch to supply the skin of the lateral forearm. Cutaneous innervation of the medial forearm is supplied by the medial cutaneous nerve of the forearm (roots C8-T1), a direct branch of the medial cord. The posterior forearm receives cutaneous innervation from the posterior cutaneous nerve of the forearm (roots C7-C8), a branch of the radial nerve.[3]

The musculocutaneous nerve parallels the axillary artery proximally in the arm, but as the nerve passes into the coracobrachialis, it then takes the unique course between the biceps brachii and brachialis and does not parallel any specific artery. Nevertheless, the blood supply to the arm is managed primarily by the brachial artery, which is a continuation of the axillary artery that arises once the vessel passes the lower margin of the teres major muscle. The brachial artery and its branches (the deep brachial, radial, and ulnar arteries) supply the muscles of the arm's anterior compartment in addition to the other structures in the arm, forearm, and hand.

Venous drainage in the arm is primarily supplied by the cephalic vein and its tributaries laterally and the basilic vein and its tributaries medially. These two veins, along with the brachial vein deep in the arm, all drain into the axillary vein that carries blood back towards the right atrium. The cephalic vein closely parallels the lateral cutaneous nerve of the forearm distal to the nerve's passage on the lateral side of the biceps brachii tendon.

The biceps brachii muscle has a short and long head. The short head originates from the coracoid process of the scapula, while the long head originates from the supraglenoid tubercle of the scapula. These two heads come together to form a single tendon that inserts in the radial tuberosity and the fascia of the forearm via the bicipital aponeurosis. The biceps brachii acts to flex the elbow, as well as supinate the forearm. The biceps brachii muscle receives innervation from the C5 and C6 fibers of the musculocutaneous nerve.

The brachialis muscle originates on the distal portion of the anterior humerus and inserts in both the coronoid process and tuberosity of the ulna. Many will think of the biceps brachii when thinking of elbow flexion, but it is actually the brachialis that is considered the primary flexor of the elbow. The brachialis is a versatile flexor in that it is able to flex the elbow from either a pronated or supinated forearm position.

Surgeons remain astute to peripheral nerve anatomy due to the relative susceptibility many nerves have to intraoperative damage. Zlotolow and colleagues describe the many surgical exposures of the humerus and the specific nerves that may be injured with each approach.[4] The deltopectoral approach, specifically for the repair of subscapularis tears, places the musculocutaneous nerve at risk. Anterolateral approaches for the reduction of humeral fractures put the lateral cutaneous nerve of the forearm at risk.[4] Additionally, it is noted that surgeons should avoid dissecting medial to the conjoined tendon (short head of the biceps and coracobrachialis attachment on the coracoid process) due to the risk of lesioning the musculocutaneous nerve.[4]

As with all nerves, direct trauma to the musculocutaneous nerve in lacerations, gunshot wounds, and nearby bone fractures has been reported.[5] While isolated musculocutaneous nerve syndromes are relatively uncommon, a few specific clinical situations have been described in the literature. Most significant is the entrapment of the musculocutaneous nerve within the coracobrachialis muscle, leading to biceps brachii and brachialis weakness and atrophy with accompanying loss of sensation in the lateral forearm. It has been found that patients most apt to develop this condition are active young individuals who frequently engage in shoulder and elbow flexion with the forearm in a pronated position.[6] This syndrome often occurs secondary to hypertrophy of the coracobrachialis as a result of chronic overuse. It is important to note that the compressed nerve within the coracobrachialis has already given off its motor branch to the coracobrachialis and thus will not present with defects of coracobrachialis muscle function.

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