Upper Limb Bones PDF
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Saba University School of Medicine
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This document provides a detailed exploration of the bones of the upper limb, covering their structure, articulations, functions, and surfaces. It explains the connections, roles, and relationships between the bones.
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Upper Limb Overview The upper limb is primarily an organ of manipulation, designed for grasping or prehensile functions. It consists of four sub-regions: Shoulder: Located proximal to the shoulder joint and unites the upper limb to the torso. Arm (Brachium): Extends from the...
Upper Limb Overview The upper limb is primarily an organ of manipulation, designed for grasping or prehensile functions. It consists of four sub-regions: Shoulder: Located proximal to the shoulder joint and unites the upper limb to the torso. Arm (Brachium): Extends from the shoulder to the elbow. Forearm (Antebrachium): Extends from the elbow to the wrist. Hand: Located distal to the wrist. Bones of the Upper Limb Clavicle: Also known as the collar bone. Scapula: Also known as the shoulder blade. Humerus: The arm bone. Radius: The lateral forearm bone, located on the thumb side. Ulna: The medial forearm bone, located on the little nger side. Carpal Bones: Consist of 8 bones located in the wrist. Metacarpal Bones: Consist of 5 bones located in the palm of the hand. Phalanges: Consist of 14 bones that make up the thumb and ngers. Clavicle The only bony connection between the upper limb and the torso. Articulations: ◦ Medially with the manubrium. ◦ Laterally with the acromion. Structure: ◦ The medial two-thirds are cylindrical and convex anteriorly. ◦ The lateral one-third is at and concave anteriorly. Functions: ◦ Pushes the limb away from the trunk. ◦ Protects the neurovascular bundle going to the upper limb. ◦ Transmits shocks (traumatic impacts) from the upper limb to the axial skeleton. Surfaces of the Clavicle Superior Surface: Smooth. Inferior Surface: Rough, containing: ◦ Costal tuberosity (medially) for the costoclavicular ligament. ◦ Subclavian groove (centrally). ◦ Conoid tubercle and trapezoid line (laterally) for the coracoclavicular ligament. Scapula Triangular-shaped, at bone. Lies on the posterolateral aspect of the thorax, overlying ribs 2–7. Surfaces of the Scapula fl fl fi fi Posterior Surface: ◦ Spine and acromion. ◦ Supraspinous fossa. ◦ Infraspinous fossa. Anterior Surface: ◦ Subscapular fossa. Borders and Angles of the Scapula Lateral Border: Thick. Medial (Vertebral) Border: Thin. Superior Border: Contains the suprascapular notch. Superior Angle: ◦ Thin, smooth, rounded, and inclined somewhat lateralward. ◦ Provides attachment to a few bers of the levator scapulae. Inferior Angle: ◦ Thick and rough. ◦ Provides attachment to the teres major and frequently a few bers of the latissimus dorsi. ◦ Level with the spinous process of T7. Head and Neck of the Scapula Head of the Scapula: ◦ Glenoid cavity: Articulates with the head of the humerus to form the glenohumeral joint. ◦ Supraglenoid and infraglenoid tubercles. Neck of the Scapula: Narrow region connecting the head to the body of the scapula. Humerus The largest bone of the upper limb. Articulates superiorly with the scapula and inferiorly with the radius and ulna. Proximal End of the Humerus Head Anatomical neck Greater and lesser tubercles Intertubercular groove Surgical neck Shaft of the Humerus Deltoid tuberosity Radial (spiral) groove Distal End of the Humerus fi fi Medial epicondyle Lateral epicondyle Trochlea Capitulum Radial fossa Coronoid fossa Olecranon fossa Ulna Located medial to the radius and is the longer of the two bones of the forearm. Homologous to the bula. Divided into three segments: proximal, shaft, and distal. Proximal End of the Ulna Olecranon process Coronoid process Trochlear notch Tuberosity of the ulna Radial notch Supinator crest and fossa Shaft of the Ulna Tapers from proximal to distal Distal End of the Ulna Round head Styloid process Radius Located lateral to the ulna. Homologous to the tibia. Proximal End of the Radius Cylindrical head ◦ Articulates proximally with the capitulum of the humerus. ◦ Articulates medially with the radial notch of the ulna. Short neck Radial tuberosity Shaft of the Radius Lateral convexity Gradually enlarges as it passes distally Distal End of the Radius fi Ulnar notch (accommodates the head of the ulna) Styloid process Dorsal tubercle of the radius Inferior surface ◦ Facet for the scaphoid and lunate bones Carpal Bones Arranged in two rows of four bones each. Proximal Row (Lateral to Medial) Scaphoid Lunate Triquetrum Pisiform Distal Row (Lateral to Medial) Trapezium Trapezoid Capitate Hamate Mnemonic "Some Lovers Try Positions That They Can’t Handle" Metacarpals and Phalanges Metacarpal Bones: ◦ Five total, numbered 1 to 5 from the thumb to the little nger. Phalanges: ◦ Fourteen total. Proximal Row of Carpal Bones Scaphoid Boat-shaped. Articulates proximally with the radius. Has a prominent scaphoid tubercle for the transverse carpal ligament. Lunate fi Moon-shaped. Articulates proximally with the radius. The median nerve crosses over it. Triquetrum Pyramidal-shaped. Articulates proximally with the articular disk of the wrist joint. Pisiform Pea-shaped. A sesamoid bone within the tendon of the exor carpi ulnaris. A good landmark for the entry of the ulnar nerve and artery. Distal Row of Carpal Bones Trapezium Lies under the thumb. Has a tubercle on its anterior surface for the attachment of the exor retinaculum and the thenar muscles. Trapezoid Resembles the trapezium but lies inside the thumb. Capitate Dome-shaped, resembling a capital building. The largest of the carpal bones. The median nerve crosses it. Hamate Wedge-shaped, located on the medial side of the hand. Possesses the hook of the hamate for the attachment of the exor carpi ulnaris and the exor retinaculum (transverse carpal ligament). The ulnar nerve passes medial to the hook. Metacarpals Numbered 1 through 5 from the thumb to the little nger. Each metacarpal has: ◦ A base (proximal), which articulates with the carpals. ◦ A shaft. ◦ A head (distal), which articulates with the phalanges. Phalanges fl fl fi fl fl Numbered 1 through 5 from the thumb to the little nger. Each phalanx has: ◦ A base (proximal). ◦ A shaft. ◦ A head (distal). Types of Phalanges: ◦ Proximal: Largest. ◦ Middle: Intermediate in size. ◦ Distal (terminal): Smallest. Clavicle Fractures Commonly caused by an indirect force transmitted from an outstretched hand. The weakest point of the clavicle is the junction of the medial two-thirds and lateral one-third. Clinical Features of a Clavicle Fracture Medial fragment moves upward due to the pull of the sternocleidomastoid (SCM) muscle. Lateral fragment moves downward due to the weight of the upper limb. The upper limb remains adducted. The most important complication is injury to the subclavian vein. fi Humerus Fractures Most fractures occur where the humerus meets the shoulder, but they can occur anywhere along the bone. Nerve damage is a major concern: ◦ Axillary nerve: Associated with fractures at the surgical neck. ◦ Radial nerve: Associated with fractures in the radial groove. ◦ Median nerve: Associated with fractures in the distal portion of the humerus. ◦ Ulnar nerve: Associated with fractures posterior to the medial epicondyle. Colles' Fracture (Dinner Fork Deformity) Common in elderly individuals with low bone density. Often results from a fall onto an outstretched hand (FOOSH). Classically involves a transverse fracture of the distal radius with dorsal displacement and shortening of the wrist. Frequently accompanied by a fracture of the ulnar styloid. Smith's Fracture (Garden Spade Deformity) Characterized by volar displacement of the distal fragment of the radius. Extraarticular fracture. Scaphoid Fracture Most commonly fractured bone of the wrist. Often results from a FOOSH (fall on outstretched hand) that exposes the scaphoid. The proximal part of the scaphoid receives its blood supply from the distal side. In a fracture, the proximal part may undergo necrosis due to disrupted blood supply. Initial radiographs may not reveal a fracture, but radiographs taken 10–14 days later can show the fracture due to bone resorption. Carpal Bone Dislocations and Fractures Dislocation of the lunate can result in impingement of the median nerve. Fracture of the capitate can lead to impingement of the median nerve. Fracture of the hamate can cause impingement of the ulnar nerve.