This region contains two bones, the ulna medially and the radius on the lateral thumb side. The elbow joint is formed by the articulation between the trochlea of the humerus and the trochlear notch of the ulna, plus the articulation between the capitulum of the humerus and the head of the radius.
The proximal radioulnar joint is the articulation between the head of the radius and the radial notch of the ulna. The proximal ulna also has the olecranon process, forming an expanded posterior region, and the coronoid process and ulnar tuberosity on its anterior aspect.
On the proximal radius, the narrowed region below the head is the neck; distal to this is the radial tuberosity. The shaft portions of both the ulna and radius have an interosseous border, whereas the distal ends of each bone have a pointed styloid process. The distal radioulnar joint is found between the head of the ulna and the ulnar notch of the radius. The distal end of the radius articulates with the proximal carpal bones, but the ulna does not. The base of the hand is formed by eight carpal bones.
The carpal bones are united into two rows of bones. The proximal row contains from lateral to medial the scaphoid, lunate, triquetrum, and pisiform bones. The scaphoid, lunate, and triquetrum bones contribute to the formation of the radiocarpal joint. The anterior hamate has a prominent bony hook.
The proximal and distal carpal rows articulate with each other at the midcarpal joint. The carpal bones, together with the flexor retinaculum, also form the carpal tunnel of the wrist.
The five metacarpal bones form the palm of the hand. The metacarpal bones are numbered 1—5, starting with the thumb side. The first metacarpal bone is freely mobile, but the other bones are united as a group. The digits are also numbered 1—5, with the thumb being number 1.
The fingers and thumb contain a total of 14 phalanges phalanx bones. The thumb contains a proximal and a distal phalanx, whereas the remaining digits each contain proximal, middle, and distal phalanges.
A fracture through the joint surface of the distal radius may make the articulating surface of the radius rough or jagged. This can then cause painful movements involving this joint and the early development of arthritis.
Surgery can return the joint surface to its original smoothness, thus allowing for the return of normal function. The hand has a proximal transverse arch, a distal transverse arch, and a longitudinal arch. These allow the hand to conform to objects being held. These arches maximize the amount of surface contact between the hand and object, which enhances stability and increases sensory input.
In this case, metal plates and screws can be used to stabilize the fractured bone. Which region of the humerus articulates with the radius as part of the elbow joint? Your friend runs out of gas and you have to help push his car. Discuss the sequence of bones and joints that convey the forces passing from your hand, through your upper limb and your pectoral girdle, and to your axial skeleton. As you push against the car, forces will pass from the metacarpal bones of your hand into the carpal bones at the base of your hand.
Forces will then pass through the midcarpal and radiocarpal joints into the radius and ulna bones of the forearm. These will pass the force through the elbow joint into the humerus of the arm, and then through the glenohumeral joint into the scapula. The force will travel through the acromioclavicular joint into the clavicle, and then through the sternoclavicular joint into the sternum, which is part of the axial skeleton.
Name the bones in the wrist and hand, and describe or sketch out their locations and articulations. The base of the hand is formed by the eight carpal bones arranged in two rows distal and proximal of four bones each.
The distal row contains from medial to lateral the hamate, capitate, trapezoid, and trapezium bones. The rows of the proximal and distal carpal bones articulate with each other at the midcarpal joint. The palm of the hand contains the five metacarpal bones, which are numbered 1—5 starting on the thumb side. The proximal ends of the metacarpal bones articulate with the distal row of the carpal bones. The distal ends of the metacarpal bones articulate with the proximal phalanx bones of the thumb and fingers.
The thumb digit 1 has both a proximal and distal phalanx bone. The fingers digits 2—5 all contain proximal, middle, and distal phalanges. Skip to content The Appendicular Skeleton. Learning Objectives By the end of this section, you will be able to: Identify the divisions of the upper limb and describe the bones in each region List the bones and bony landmarks that articulate at each joint of the upper limb.
Humerus The humerus is the single bone of the upper arm region Figure. Humerus and Elbow Joint. The humerus is the single bone of the upper arm region. It articulates with the radius and ulna bones of the forearm to form the elbow joint. Ulna The ulna is the medial bone of the forearm. Ulna and Radius. The ulna is located on the medial side of the forearm, and the radius is on the lateral side. These bones are attached to each other by an interosseous membrane.
Radius The radius runs parallel to the ulna, on the lateral thumb side of the forearm see Figure. Carpal Bones The wrist and base of the hand are formed by a series of eight small carpal bones see Figure. Bones of the Wrist and Hand. The eight carpal bones form the base of the hand. These are arranged into proximal and distal rows of four bones each. The metacarpal bones form the palm of the hand.
The thumb and fingers consist of the phalanx bones. This radiograph shows the position of the bones within the hand. Note the carpal bones that form the base of the hand. The carpal tunnel is the passageway by which nine muscle tendons and a major nerve enter the hand from the anterior forearm. The walls and floor of the carpal tunnel are formed by the U-shaped grouping of the carpal bones, and the roof is formed by the flexor retinaculum, a strong ligament that anteriorly unites the bones.
Hand During Gripping. During tight gripping—compare b to a —the fourth and, particularly, the fifth metatarsal bones are pulled anteriorly. This increases the contact between the object and the medial side of the hand, thus improving the firmness of the grip. Disorders of the….
Fractures of the Humerus and Radius. Falls or direct blows can result in fractures of the surgical neck or shaft of the humerus. Falls onto the elbow can fracture the distal humerus.
A Colles fracture of the distal radius is the most common forearm fracture. The radius is smaller than the ulna. Key Terms radius : One of two forearm bones, it is located laterally to the ulna. The Ulna Anatomically, the ulna is located medially to the radius, placing it near the little finger.
Proximally, there are five key regions of the ulna: The olecranon is a projection of bone that extends proximally from the ulna. The triceps brachii muscle attaches to the ulna superiorly. The cornoid process, together with the olecranon, forms the trochlear notch where it articulates with the trochlea of the humerus. Laterally to the trochlear notch lies the radial notch, which articulates with the head of the radius to form the proximal radioulnar joint.
Immediately distal to the coronoid process is the tuberosity of ulna, to which the brachialis muscle attaches. The Radius Anatomically, the radius is located laterally to the ulna placing it near the thumb. Only three of these bones, the scaphoid, lunate, and triquetrum, contribute to the radiocarpal joint.
The scaphoid and lunate bones articulate directly with the distal end of the radius, whereas the triquetrum bone articulates with a fibrocartilaginous pad that spans the radius and styloid process of the ulna. The distal end of the ulna thus does not directly articulate with any of the carpal bones. The palm of the hand contains five elongated metacarpal bones.
These bones lie between the carpal bones of the wrist and the bones of the fingers and thumb see Figure 6. The proximal end of each metacarpal bone articulates with one of the distal carpal bones. Each of these articulations is a carpometacarpal joint. The expanded distal end of each metacarpal bone articulates at the metacarpophalangeal joint with the proximal phalanx bone of the thumb or one of the fingers. The distal end also forms the knuckles of the hand, at the base of the fingers.
The metacarpal bones are numbered 1—5, beginning at the thumb. The thumb pollex is digit number 1 and has two phalanges, a proximal phalanx, and a distal phalanx bone see Figure 6.
Digits 2 index finger through 5 little finger have three phalanges each, called the proximal, middle, and distal phalanx bones. An interphalangeal joint is one of the articulations between adjacent phalanges of the digits. Visit this site to explore the bones and joints of the hand. What are the three arches of the hand, and what is the importance of these during the gripping of an object?
Due to our constant use of the hands and the rest of our upper limbs, an injury to any of these areas will cause a significant loss of functional ability. Many fractures result from a hard fall onto an outstretched hand. The resulting transmission of force up the limb may result in a fracture of the humerus, radius, or scaphoid bones.
These injuries are especially common in elderly people whose bones are weakened due to osteoporosis. Falls onto the hand or elbow, or direct blows to the arm, can result in fractures of the humerus Figure 6. Following a fall, fractures at the surgical neck, the region at which the expanded proximal end of the humerus joins with the shaft, can result in an impacted fracture, in which the distal portion of the humerus is driven into the proximal portion.
Falls or blows to the arm can also produce transverse or spiral fractures of the humeral shaft. In children, a fall onto the tip of the elbow frequently results in a distal humerus fracture. In these, the olecranon of the ulna is driven upward, resulting in a fracture across the distal humerus, above both epicondyles supracondylar fracture , or a fracture between the epicondyles, thus separating one or both of the epicondyles from the body of the humerus intercondylar fracture.
With these injuries, the immediate concern is possible compression of the artery to the forearm due to swelling of the surrounding tissues. If compression occurs, the resulting ischemia lack of oxygen due to reduced blood flow can quickly produce irreparable damage to the forearm muscles.
In addition, four major nerves for shoulder and upper limb muscles are closely associated with different regions of the humerus, and thus, humeral fractures may also damage these nerves. This involves a complete transverse fracture across the distal radius that drives the separated distal fragment of the radius posteriorly and superiorly.
This is the most frequent forearm fracture and is a common injury in persons over the age of 50, particularly in older women with osteoporosis. It also commonly occurs following a high-speed fall onto the hand during activities such as snowboarding or skating.
The most commonly fractured carpal bone is the scaphoid, often resulting from a fall onto the hand. Deep pain at the lateral wrist may yield an initial diagnosis of a wrist sprain, but a radiograph taken several weeks after the injury, after tissue swelling has subsided, will reveal the fracture. Due to the poor blood supply to the scaphoid bone, healing will be slow and there is the danger of bone necrosis and subsequent degenerative joint disease of the wrist.
Watch this video to learn about a Colles fracture, a break of the distal radius, usually caused by falling onto an outstretched hand. When would surgery be required and how would the fracture be repaired in this case?
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