What Is Your Upper Arm Bone Called – The upper part is divided into three parts. These include the arm between the shoulder and elbow joints; forearm between the elbow and wrist joints; and the arm away from the wrist. Each upper leg has 30 bones. The humerus is one bone of the arm, while the ulna (medial) and radius (lateral) are the joint bones of the forearm. The base of the hand contains eight carpal bones, while the palm of the hand is made up of five metacarpal bones. The fingers and thumb contain a total of 14 phalanges.
The humerus is a single bone of the upper arm (Figure 8.2.1). At its proximal end is the head of the humerus. This is a large, round, smooth area facing the middle face. The head articulates with the glenoid fossa of the scapula to form the glenohumeral (shoulder) joint (see Chapter 9). The border of the smooth surface of the head is the anatomical neck of the humerus. On the lateral side of the proximal humerus is an enlarged bony area called the greater tubercle. The small tubercle of the humerus is located in the anterior part of the humerus. Both the greater and lesser tubercles serve as points of attachment for the muscles that run across the shoulder (see Chapter 11). Passing between the greater and lesser tuberosities is a small intertuberous groove (sulcus), known as the bicipital groove, as it passes the tendon of the biceps brachii muscle. The surgical neck is located where the proximal end of the humerus joins the small shaft of the humerus, a common location for arm fractures. The deltoid tuberosity is a rough, V-shaped area located on the medial-lateral side of the humerus shaft. As its name suggests, it is the attachment point of the deltoid muscle.
What Is Your Upper Arm Bone Called
Figure 8.2.1 – Humerus and Elbow Joint: The humerus is one bone of the arm. It articulates with the radius and ulna bones of the forearm to form the elbow joint.
Types Of Bones
Distally, the humerus is flat. The most prominent bone on the medial side is the medial epicondyle of the humerus. The very small lateral epicondyle of the humerus is found on the lateral side of the distal humerus. The rough ridge of bone above the lateral epicondyle is the lateral supracondylar ridge. All of these areas are attachment points for the muscles that work in the forearm, wrist and hand. The strong muscles of the forearm come from the medial epicondyle, which is larger and stronger than the lateral epicondyles, which form the weak muscles of the forearm (see Chapter 11).
The distal end of the humerus has two articular surfaces, which are attached to the ulna and radius bones of the forearm to form the elbow joint. Central to these areas is the trochlea, a spindle or pulley-shaped region (trochlea = “pulley”) that corresponds to the ulna. Immediately lateral to the trochlea is the capitulum (“small head”), a button-like structure located on the anterior surface of the distal humerus. The capitulum articulates with the radius bone in the forehead. Just above these bone sites are two small dances. These spaces accommodate the bones of the forearm when the elbow is fully flexed. Superior to the trochlea is the coronoid fossa, which receives the coronal process of the ulna, and superior to the capitulum is the radial fossa, which receives the head of the radius when the elbow is flexed. Similarly, the posterior humerus has the olecranon fossa, a large depression that receives the olecranon process of the ulna when the forearm is fully extended.
The ulna is the middle bone in the forearm. It runs parallel to the radius, the lateral frontal bone (Figure 8.2.2). The proximal end of the ulna resembles a crescent wrench and its large, C-shaped, trochlear notch. This region corresponds to the trochlea of the humerus as part of the elbow joint. The lower border of the trochlear notch is formed by a prominent bone called the coronoid process of the ulna. Just below here is a rough area called the ulnar tuberosity on the anterior ulna. Lateral and slightly inferior to the trochlear notch is a small smooth surface of the ulna known as the radial notch. This region is the joint between the ends of the radius and the ulna, which forms the proximal radiolunar joint. The posterior and superior parts of the anterior ulna form the olecranon process, which forms the bony tip of the elbow.
Figure 8.2.2 – Ulna and Radius: The ulna is on the medial side of the forearm, while the radius is on the lateral side. These bones are connected to each other by an inner membrane.
Humerus: Anatomy, Bone Markings, Labeled Diagrams
The most distal part is the shaft of the ulna. The lateral side of the shaft forms a ridge called the interosseous border of the ulna. This is the line of attachment to the interosseous membrane of the forearm, a thick sheet of connective tissue that connects the ulna and radius bones. A small, rounded area that forms the distal end of the head of the ulna. Projecting from the back side of the ulnar head is the styloid process of the ulna, a short bony outline. This serves as an attachment point for the connective tissue that connects the distal end of the ulna with the carpal bones of the wrist joint.
In the anatomical situation, when the elbow is fully extended and the palm is forward, the hand and the forearm do not form a straight line. Instead, the forearm deviates laterally by 5-15 degrees from the wrist line. This deviation is called the bearing angle. It allows the forearm and arm to swing freely or carry an object without hitting the hip. The bearing angle is greater for the female.
The radius runs parallel to the ulna, on the lateral (big toe) side of the forefoot (see figure 8.2.2). The radial head is a disk-shaped structure that forms the proximal end. A small depression on the surface of the head defines the capitulum of the humerus as part of the elbow joint, and the smooth, external head defines the radial notch of the ulna in the joint radiolunar joint. The radial neck is the narrow region below the enlarged head. Below this level on the medial side is the radial tuberosity, an oval-shaped, bony projection that serves as a place for muscle attachment. The shaft of the radius is slightly curved and has a small ridge along its middle. This spine forms the joint border of the radius, which, like the same border of the ulna, is the line of attachment to the joint membrane that connects the two bones of the forearm. The distal end of the radius has a smooth surface to articulate with the two carpal bones to form the radiocarpal joint or wrist joint (Figure 8.2.3 and Figure 8.2.4). On the medial side of the distal radius is the ulnar notch of the radius. This shallow depression articulates with the head of the ulna, which when united forms the distal radioulnar joint. At the lateral end of the radius is a pointed projection called the process of the radial style. This provides attachment to the ligaments that support the lateral aspect of the wrist joint. Compared to the ulna style system, the radius style system projects more, thereby limiting the range of motion of lateral deviation of the arm at the wrist joint.
Watch this video to see how a distal radius fracture affects the wrist. Explain the problems that can occur if the radius is broken far to the articular surface of the radiocarpal joint of the wrist.
Fractures Of The Shoulder Blade (scapula)
The wrist and hand have eight small carpal bones (see Figure 8.2.3). Carpal bones are arranged in two rows, forming a circular row of four carpal bones and a descending row of four carpal bones. Running from the lateral side (big toe) to the medial side are the scaphoid (“boat-shaped”), the lunate (“moon-shaped”), the triquetrum (“three-cornered”) and the pisiform (“pea-shaped”). bones. The small, round pisiform bone articulates with the anterior surface of the triquetrum bone. Thus the pisiform projects forward, where it forms a bony bump that can be felt on the medial side of your hand. The distal bones (from lateral to medial) are the trapezium (“table”), trapezoid (“table-like”), capitate (“head-shaped”), and hamate (“bone this hook”). The hamate bone is characterized by a prominent bony prominence on the anterior side, called the hook of the hamate bone.
A useful mnemonic for remembering the arrangement of the carpal bones is “Pinky gets the longest, big toe.” This mnemonic starts on the lateral side and names the adjacent bones from side to medial (scaphoid, lunate, triquetrum,
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