Appendicular Skeleton

Overview of the Appendicular Skeleton

The appendicular skeleton consists of the bones that form the limbs and girdles, enabling movement and interaction with the environment. It is distinct from the axial skeleton, which includes the skull, vertebral column, and thoracic cage.

• Axial Skeleton: Central axis of the body (skull, vertebral column, rib cage).

• Appendicular Skeleton: Limbs and girdles (pectoral and pelvic girdles, upper and lower limbs).

Comparison: Axial vs. Appendicular Skeleton

Pectoral Girdle

Bones and Functions of the Pectoral Girdle

The pectoral girdle attaches the upper limbs to the trunk and provides mobility and flexibility.

• Bones: Clavicle (collarbone) and scapula (shoulder blade).

• Function: Supports the arm, allows for a wide range of motion.

Principal Bone Markings of the Upper Limb

The upper limb consists of several bones, each with distinct markings for muscle attachment and articulation.

• Humerus: Head, greater and lesser tubercles, deltoid tuberosity.

• Radius: Radial tuberosity, styloid process.

• Ulna: Olecranon, coronoid process.

Elbow Joint

The elbow joint is formed by the articulation of the humerus, radius, and ulna.

• Humerus: Trochlea and capitulum.

• Ulna: Olecranon and trochlear notch.

• Radius: Head of radius.

Carpal Bones and Carpal Tunnel

The wrist contains eight carpal bones arranged in two rows:

• Proximal row: Scaphoid, lunate, triquetrum, pisiform.

• Distal row: Trapezium, trapezoid, capitate, hamate.

The carpal tunnel is a passageway formed by carpal bones and the flexor retinaculum, through which nerves and tendons pass.

Metacarpals and Phalanges

• Metacarpals: Five bones numbered I-V from thumb to little finger; articulate with carpals and phalanges.

• Phalanges: Each finger has proximal, middle, and distal phalanges, except the thumb (pollex), which has only proximal and distal.

Pelvic Girdle

Bones and Functions of the Pelvic Girdle

The pelvic girdle attaches the lower limbs to the trunk and supports the weight of the body.

• Bones: Two hip bones (os coxa), each composed of the ilium, ischium, and pubis.

• Function: Supports body weight, protects pelvic organs, provides attachment for lower limbs.

Anatomy of the Pelvic Girdle

• Acetabulum: Deep socket for the head of the femur.

• Ilium: Largest part, forms the superior region.

• Ischium: Posterior and inferior part.

• Pubis: Anterior part.

Male vs. Female Pelvis

Lower Limb

Bones and Principal Bone Markings

• Femur: Head, neck, greater and lesser trochanters.

• Tibia: Medial and lateral condyles, tibial tuberosity.

• Fibula: Head, lateral malleolus.

Segments of the Lower Limb

• Thigh: Femur.

• Leg: Tibia and fibula.

• Foot: Tarsals, metatarsals, phalanges.

These segments correspond to the upper limb: arm (humerus), forearm (radius and ulna), hand (carpals, metacarpals, phalanges).

Q-Angle and ACL Injury

The Q-angle is the angle formed by the quadriceps muscle and the patellar tendon. A larger Q-angle is associated with increased risk of ACL injury, especially in females.

Bones of the Foot and Arch

• Tarsals: Seven bones including the talus and calcaneus.

• Metatarsals: Five bones numbered I-V.

• Phalanges: Proximal, middle, and distal for each toe except the hallux (big toe).

• Arch of the Foot: Provides support and flexibility; includes medial longitudinal, lateral longitudinal, and transverse arches.

Muscle Attachments in the Appendicular Skeleton

Muscles attach to specific bone markings, enabling movement. For example, the deltoid muscle attaches to the deltoid tuberosity of the humerus, and the quadriceps attach to the tibial tuberosity.

Summary Table: Major Bones and Markings

Additional info:

• The appendicular skeleton is essential for locomotion and manipulation of the environment.

• Bone markings serve as sites for muscle attachment, articulation, and passage of nerves and blood vessels.