Anatomy: Carpal Bones, Metacarpal Bones, and Phalanges

Appendicular Skeleton

• Composed of 126 bones
• Divided into 4 main parts: pectoral girdles, upper limbs, pelvic girdle, and lower limbs

Pectoral Girdles

• Consist of 4 bones: 2 clavicles and 2 scapulae
• Anchor the upper limb to the axial skeleton
• Each side consists of a clavicle and a scapula

Clavicle

• A long bone with 2 ends: rounded, medial (sternal) end and flattened, lateral (acromial) end
• Articulates with the manubrium of the sternum to form the sternoclavicular joint
• Articulates with the acromion of the scapula to form the acromioclavicular joint

Scapula

• A flat, triangular bone located behind the chest at the level of rib pairs 2-7
• Has a horizontal plate of bone called the spine, with a bony process called the acromion at the end
• Articulates with the clavicle
• Has a concave area at the front called the subscapular fossa
• Has a glenoid cavity that articulates with the humerus

Upper Limbs

• Composed of: humerus, radius, ulna, carpals, metacarpals, and phalanges

Humerus

• The head of the humerus is round and articulates with the glenoid cavity of the scapula
• Has a groove called the anatomical neck
• Has two eminences (tubercles) that point forward: greater tubercle and lesser tubercle
• Has a deep groove called the intertubercular groove
• Has a segment called the surgical neck
• Has a rough, elevated surface called the deltoid tuberosity on the lateral side of the shaft

Radius and Ulna

• Radius: has a flat head that articulates with the capitulum of the humerus and the radial notch of the ulna
• Ulna: has an olecranon process that fits into the olecranon fossa of the humerus
• Ulna: has a coronoid process that fits into the coronoid fossa of the humerus
• Ulna: has a hook-like, anterior cavity called the trochlear notch

Elbow Joint

• Articulation of the distal end of the humerus and the head of the radius and proximal part of the ulna

Carpal Bones

• 8 small bones in the wrist, arranged in 2 rows (4 bones per row)
• Divided into proximal and distal rows
• Proximal row: scaphoid, lunate, triquetrum, and pisiform
• Distal row: trapezium, trapezoid, capitate, and hamate

Metacarpal Bones and Phalanges

• Metacarpal bones: 5 long bones in the palm, numbered from 1 to 5 (starting from the thumb)
• Each hand contains 14 phalanges, with 3 phalanges in each finger except the thumb which has only 2
• A phalanx is composed of proximal, middle, and distal parts

Pelvic Girdle

• Composed of 2 hip bones
• Each hip bone is composed of 3 parts: pubis, ilium, and ischium

Hip Bone

• Pubis: the ventral and anterior hip bone, tilts downwards and unites with the other pubic bone in the pubic symphysis
• Ilium: the largest region of the hip bone, has a broad cavity called the iliac fossa
• Ischium: found at the lower and back part of the hip bone, has a pointed eminence on the body posterior

Lower Limbs

• Composed of: femur, patella, tibia, fibula, tarsal bones, metatarsal bones, and phalanges

Femur

• The longest and heaviest bone in the body
• Divided into: head, neck, and shaft
• Has a nearly spherical head at the proximal end that articulates with the acetabulum of the hip bone
• Has a shaft (body) that contains the linea aspera, a longitudinal ridge where thigh muscles are attached

Patella

• A triangular bone found in front of the knee
• Articulates with the femur and tibia to form the knee joint

Joints

• Fibrous joint: adjacent bones are tightly joined by fibrous connective tissue, permitting little to no mobility
• Cartilaginous joint: joined by cartilage and contains no space between connected bones
• Synovial joint: contains a joint cavity between articulating bones; filled with synovial fluid that acts as a lubricant to facilitate joint movement
• Types of synovial joints: gliding, hinge, pivot, saddle, ellipsoidal, and ball-and-socket joints