Skeletal Structure Of The Arm
The bones of the arm consist of the humerus, radius and ulna. The primary bone of the arm is known as the humerus. This is attached to the area near the shoulder known as the scapula at the glenohumeral joint. The tip of the humerus fits well into the area near the shoulders through the ball and socket structure allowing its rotational motion. The elbow serves as the joint between the distal or far end of the humerus of the upper arm and the proximal tip of the bones of the lower arm which are the radius and the ulna. These bones are noted to be very strong especially the humerus because it is designed to be able to carry heavy load. It can carry weight till about 140 kilograms.
The Muscles Of The Arm
The arm is richly attached with different muscles making it capable of performing different functions and motion. First of all, the arm has its muscles which are separated into the osteofascial compartments or areas which are the anterior and posterior parts of the arm. The fascia of the muscles is known to be attached firmly to the humerus or the bone of the upper arm thus being able to support its range of movements.
There are two main muscles that can be found in the arm and these are the large deltoid muscle and the brachioradialis muscle. The deltoid muscle is known to be the great part of the anterior compartment of the arm or the upper area. This muscle is also known to be the primary abductor of the upper limb. Being an abductor, the deltoid muscle has the ability to move the arm closer to the body. On the other hand, the brachioradialis muscle is found greatly in the lower arm or the forearm. This is the muscle responsible for supination of the hand or movement of the hand with the palm facing upward.
The Nerves Innervating The Arm
Like any other body part, the arm is innervated with nerves and is well given its needed blood supply. As you may have noticed whenever there are blood extractions or venipuncture, the area or junction between the upper and the lower arm known as the elbow pit is often the site of choice. This is because there is an accessible vein on the said area where blood can be easily extracted. Also, as you take the blood pressure, you may notice that it is usually taken in the same area known as the elbow pit. This is because this area has an easily detectable pulse. The pulse that can be found in this area is known as the brachial pulse.
There are several nerves that can be found on the arm which are known to be very sensitive to environmental stimulus. The main nerve that supplies the muscles of the anterior part of the arm is known as the musculocutaneous nerve from the C5, C6 and C7 areas of the cervical spine. The musculocutaneous nerve is known to originate from the brachial plexus of nerves. There is also what is known as the radial nerve located from C5 to T1. This nerve originated from the posterior branch of the brachial plexus as compared to the musculocutaneous nerve which comes from the anterior branch.
Aside from these two main nerves that innervate the arm, there are also other nerves that pass through the arm. First of all, there is the median nerve coming from C5 to T1 of the cervical and thoracic spine respectively. It originates from the lateral and medial branch or cords of the brachial plexus. This nerve travels between the triceps and the biceps muscle and passes through the lower arm or the forearm. Another nerve related to the arm is known as the ulnar nerve coming from the C8 and T1. The ulnar nerve serves to be the continuation of the medial branch or cord of the brachial plexus. The area where the ulnar nerve passes is similar to that of the median nerve which also passes through the triceps and the biceps muscles.
The Blood Supply Of The Arm
When it comes to the blood supply, there are arteries and veins that can be greatly found in the arm. The main artery that can be found in the arm is the brachial artery. The brachial artery serves to become the continuation of the axillary artery found in the upper part of the arm. The brachial artery continues in the area of the anterior compartment of the arm primarily in the cubital fossa. The veins of the arm are known to carry the blood back to the heart from the arm itself. There are two main veins that can be found in the arm which are the cephalic and the basilic veins. The basilic veins and the cephalic veins are connected to each other by the means of the median cubital vein. The median cubital vein is passing through the cubital fossa, which can be very important in blood extraction or venipuncture. The cephalic vein passes through the lateral side of the arm and ends in the axillary vein. Lastly, the basilic vein passes through the medial side of the arm ending then at the seventh rib.
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