Describe the bones of the top limb, including the bones of the arm, forearm, wrist, and hand

Appropriately surname the areas of the upper limb and also list the bones in each regionList the bones and also bony landmarks the articulate at every joint that the top limb

The top limb is divided into three regions. These consist that the arm, located between the shoulder and elbow joints; the forearm, which is between the elbow and wrist joints; and also the hand, i beg your pardon is situated distal to the wrist. There room 30 skeletal in each upper limb. The humerus is the solitary bone of the arm, and the ulna (medially) and the radius (laterally) space the paired bones the the forearm. The basic of the hand includes eight carpal bones, and the palm that the hand is created by 5 metacarpal bones. The fingers and also thumb contain a total of 14 phalanges.

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Humerus

The humerus is the single bone of the arm region (Figure 8.2.1). At its proximal end is the head that the humerus. This is the large, round, smooth an ar that deals with medially. The head articulates with the glenoid cavity the the scapula to form the glenohumeral (shoulder) share (see thing 9). The margin the the smooth area the the head is the anatomical neck that the humerus. Located on the lateral next of the proximal humerus is an increased bony area dubbed the greater tubercle. The smaller sized lesser tubercle of the humerus is uncovered on the anterior facet of the humerus. Both the greater and lesser tubercles offer as attachments sites for muscles the act throughout the shoulder joint (see chapter 11). Passing in between the greater and also lesser tubercles is the small intertubercular groove (sulcus), which is additionally known together the bicipital groove because it provides passage because that a tendon of the biceps brachii muscle. The surgical neck is situated where the proximal finish of the humerus join the small shaft that the humerus, and is a typical site of arm fractures. The deltoid tuberosity is a roughened, V-shaped an ar located ~ above the lateral side in the middle of the humerus shaft. As its name indicates, that is the website of attachment for the deltoid muscle.

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Figure 8.2.1 – Humerus and also Elbow Joint: The humerus is the single bone the the eight region. It articulates through the radius and ulna bones of the forearm to form the elbow joint.

Distally, the humerus i do not care flattened. The prominent bony forecast on the medial side is the medial epicondyle of the humerus. The lot smaller lateral epicondyle that the humerus is uncovered on the lateral side of the distal humerus. The roughened ridge the bone over the lateral epicondyle is the lateral supracondylar ridge. All of these locations are attachments points because that muscles the act ~ above the forearm, wrist, and also hand. The an effective grasping muscles of the anterior forearm arise indigenous the medial epicondyle, which is therefore larger and much more robust than the lateral epicondyle that gives rise come the weaker posterior forearm muscles (see thing 11).

The distal finish of the humerus has actually two articulation areas, which sign up with the ulna and radius skeleton of the forearm to form the elbow joint. The an ext medial that these areas is the trochlea, a spindle- or pulley-shaped region (trochlea = “pulley”), i m sorry articulates v the ulna bone. Immediately lateral come the trochlea is the capitulum (“small head”), a knob-like structure located on the anterior surface of the distal humerus. The capitulum articulates through the radius bone of the forearm. Just above these bony locations are two small depressions. This spaces accommodate the forearm bones when the elbow is completely bent (flexed). Premium to the trochlea is the coronoid fossa, i beg your pardon receives the coronoid procedure of the ulna, and superior to the capitulum is the radial fossa, which receives the head the the radius once the elbow is flexed. Similarly, the posterior humerus has actually the olecranon fossa, a bigger depression that receives the olecranon procedure of the ulna once the forearm is completely extended.

Ulna

The ulna is the medial bone of the forearm. It operation parallel to the radius, which is the lateral bone the the forearm (Figure 8.2.2). The proximal finish of the ulna each other a crescent wrench through its large, C-shaped, trochlear notch. This region articulates v the trochlea of the humerus as part of the elbow joint. The worse margin the the trochlear notch is developed by a significant lip that bone dubbed the coronoid procedure of the ulna. Just listed below this ~ above the anterior ulna is a roughened area dubbed the ulnar tuberosity. To the lateral side and slightly inferior to the trochlear notch is a small, smooth area referred to as the radial notch the the ulna. This area is the website of articulation between the proximal ends of the radius and ulna, creating the proximal radioulnar joint. The posterior and also superior parts of the proximal ulna consist of the olecranon process, which develops the bony tip of the elbow.

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Figure 8.2.2 – Ulna and Radius: The ulna is situated on the medial next of the forearm, and the radius is on the lateral side. This bones room attached to each various other by one interosseous membrane.

More distal is the shaft of the ulna. The lateral next of the shaft creates a ridge called the interosseous border the the ulna. This is the line of attachment because that the interosseous membrane that the forearm, a paper of thick connective tissue that hold together the ulna and radius bones. The small, rounded area that creates the distal end is the head that the ulna. Projecting indigenous the posterior side of the ulnar head is the styloid process of the ulna, a short bony projection. This serves together an attachment allude for connective organization that unite the distal finish of the ulna v the carpal skeleton of the wrist joint.

In the anatomical position, v the elbow fully extended and the palms dealing with forward, the arm and forearm execute not kind a directly line. Instead, the forearm deviates laterally by 5–15 degrees from the line of the arm. This deviation is called the transporting angle. It permits the forearm and also hand come swing betterworld2016.orgly or to carry things without hitting the hip. The delivering angle is bigger in females.

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Radius

The radius operation parallel to the ulna, on the lateral (thumb) side of the forearm (see number 8.2.2). The head that the radius is a disc-shaped structure that forms the proximal end. The little depression on the surface of the head articulates through the capitulum of the humerus as part of the elbow joint, vice versa, the smooth, external margin of the head articulates through the radial notch that the ulna in ~ the proximal radioulnar joint. The neck of the radius is the narrowed an ar immediately below the increased head. Inferior to this suggest on the medial next is the radial tuberosity, one oval-shaped, bony protuberance that serves as a muscle attachments point. The shaft the the radius is contempt curved and has a tiny ridge follow me its medial side. This ridge forms the interosseous border the the radius, which, like the similar border of the ulna, is the line of attachment for the interosseous membrane that unites the two forearm bones. The distal end of the radius has a smooth surface ar for articulation v two carpal skeleton to form the radiocarpal joint or wrist share (Figure 8.2.3 and Figure 8.2.4). ~ above the medial side of the distal radius is the ulnar notch the the radius. This shallow depression articulates with the head the the ulna, which together kind the distal radioulnar joint. The lateral finish of the radius has a spicy projection called the styloid process of the radius. This offers attachment because that ligaments that assistance the lateral side of the wrist joint. Compared to the styloid procedure of the ulna, the styloid process of the radius projects more distally, in order to limiting the variety of motion for lateral deviations the the hand at the wrist joint.