Bones of the Upper Limb

Study Notes

Bones of the Upper Limb

Clavicle (Collar Bone): Connects the upper limb to the trunk. The medial two-thirds of the shaft are convex anteriorly, while the lateral third is flattened and concave anteriorly.
- Sternal end (flat): Forms the sternoclavicular joint
- Acromial end (round): Forms the coracoacromial joint
Scapula (Shoulder Blade): A triangular flat bone overlying the 2nd-7th ribs.
- Posterior surface: Unevenly divided by the spine of the scapula into a small supraspinous fossa and a larger infraspinous fossa.
- Anterior costal surface: Forms a large subscapular fossa.
- Spine continues laterally: As the acromion and articulates with the acromial end of the clavicle.
- Lateral surface: Has a glenoid cavity which articulates with the head of the humerus.
- Coracoid process: Projects anterolaterally, superior to the glenoid cavity.
Humerus (Upper Arm Bone):
- Proximal end: Includes the head, surgical and anatomical necks, greater and lesser tubercles, and the intertubercular sulcus (bicipital groove).
- Shaft: Features the deltoid tuberosity (laterally), radial groove (posteriorly), and medial and lateral supra-epicondylar ridges.
- Distal end (condyle of the humerus: Two articular surfaces (lateral capitulum and medial trochlea) and three fossae (coronoid, radial, and olecranon).
Ulna (Medial Forearm Bone):
- Proximal end: Articulates with the humerus via the olecranon and coronoid processes, and with the head of the radius via the radial notch.
- Shaft: Thick and cylindrical proximally, diminishing in diameter distally, has a tuberosity of the ulna inferior to the coronoid process.
- Distal end: Includes the head, ulnar styloid process, and does not participate in the wrist joint.
Radius (Lateral Forearm Bone):
- Proximal end: Head articulates with the capitulum of the humerus and radial notch of the ulna. The neck is a constriction distal to the head, and the oval radial tuberosity is distal to the medial part of the neck.
- Shaft: Gradually enlarges distally and is triangular in cross-section, with an interosseous border forming the apex.
- Distal end: Forms a concavity (ulnar notch), terminates in the styloid process, larger than the ulnar styloid process.
Carpus (Wrist): Eight carpal bones arranged in two rows:
- Proximal row (lateral to medial): Scaphoid, lunate, triquetrum, pisiform
- Distal row (lateral to medial): Trapezium, trapezoid, capitate, hamate
Metacarpus (Palm): Five metacarpal bones, the proximal bases articulate with the carpal bones, and the distal heads articulate with the proximal phalanges.
Phalanges (Fingers): Three phalanges in each digit except the thumb which has two. Each phalanx has a base, shaft, and head.
Radiographs of the wrist and hand: Used to assess skeletal age and compared with standard atlases. Ossification centers are usually evident during the first year and appear before birth.
- Capitate and hamate: Centers appear first.
Fractures of the Humerus: Potential injuries include:
- Surgical neck: Axillary nerve
- Radial groove: Radial nerve
- Distal end: Median nerve and brachial artery
- Medial epicondyle: Ulnar nerve
Colles Fracture: A complete transverse fracture of the distal 2 cm of the radius, the distal fragment is displaced dorsally, usually caused by forced extension of the hand.

Muscles of the Back

Extrinsic back muscles: Move the upper limbs, scapula, and head.
- Superficial Layer:
  - Trapezius
  - Latissimus dorsi
  - Levator scapulae
  - Rhomboids
- Intermediate Layer:
  - Serratus posterior superior
  - Serratus posterior inferior
Intrinsic back muscles: Move the vertebral column.
- Superficial Layer:
  - Splenius cervicis
  - Splenius capitis
- Intermediate Layer:
  - Iliocostalis
  - Longissimus
  - Spinalis
- Deep Layer:
  - Semispinalis
  - Multifidus
  - Rotatores
  - Interspinales
  - Intertransversarii
  - Levatores costarum