Study Guide: Bones of the Axial and Appendicular Skeleton (Anatomy & Physiology)

Section 8-1: The Pectoral (Shoulder) Girdle and the Upper Limbs

Structure and Articulations of the Pectoral Girdle

The pectoral girdle connects the upper limbs to the axial skeleton and provides mobility and support. It consists of the clavicle and scapula, which articulate with the humerus at the shoulder joint.

• Clavicle: The only direct articulation between the pectoral girdle and the axial skeleton is at the sternoclavicular joint, where the clavicle meets the manubrium of the sternum.

• Acromioclavicular joint: The lateral end of the clavicle articulates with the acromion of the scapula.

• Glenohumeral joint: The scapula articulates with the head of the humerus at the glenoid cavity.

• Coracoid process: A projection on the scapula that serves as an attachment for muscles and ligaments.

Example: The clavicle can be palpated at the base of the neck, and its sternal end is easily felt at the manubrium.

Key Bony Landmarks and Functions

• Acromion: The lateral extension of the scapula, forming the highest point of the shoulder.

• Coracoid process: Projects anteriorly from the scapula and serves as a muscle attachment site.

• Glenoid cavity: The shallow socket that articulates with the head of the humerus, allowing for a wide range of motion.

• Spine of the scapula: A prominent ridge on the posterior surface of the scapula.

Additional info: The pectoral girdle is highly mobile but less stable than the pelvic girdle, making the shoulder susceptible to dislocation.

Section 8-2: The Bones of the Upper Limbs

Adaptations for Free Movement

The bones of the upper limbs are specialized for a wide range of motion, allowing for complex movements and dexterity.

• Humerus: The bone of the upper arm, articulating proximally with the scapula and distally with the radius and ulna.

• Radius and Ulna: The two bones of the forearm. The radius is lateral (thumb side), and the ulna is medial (little finger side) in anatomical position.

• Olecranon: The prominent bony point of the elbow, part of the ulna.

• Styloid process: A pointed projection at the distal ends of both the radius and ulna.

• Carpals, Metacarpals, and Phalanges: The bones of the wrist, hand, and fingers, respectively.

Example: The pollex (thumb) is composed of only two phalanges, unlike the other fingers, which have three.

Section 8-3: The Pelvic Girdle and Lower Limbs

Structure and Function of the Pelvic Girdle

The pelvic girdle supports the weight of the upper body, protects pelvic organs, and provides attachment for lower limbs. It is formed by two hip bones (ossa coxae), each consisting of three fused bones: ilium, ischium, and pubis.

• Sacroiliac joint: The articulation between the sacrum and the ilium of the hip bone.

• Pubic symphysis: A cartilaginous joint uniting the left and right pubic bones.

• Acetabulum: The deep socket that receives the head of the femur, forming the hip joint.

• Obturator foramen: A large opening created by the ischium and pubis bones, allowing passage of nerves and blood vessels.

Additional info: The pelvic girdle is more stable but less mobile than the pectoral girdle, providing support for locomotion.

Section 8-4: The Bones of the Lower Limbs

Adaptations for Movement and Support

The bones of the lower limbs are adapted for weight-bearing and locomotion, providing strength and stability.

• Femur: The longest and strongest bone in the body, articulating proximally with the pelvis and distally with the tibia and patella.

• Patella: The kneecap, a sesamoid bone embedded in the quadriceps tendon.

• Tibia and Fibula: The bones of the lower leg. The tibia is medial and weight-bearing; the fibula is lateral and slender.

• Malleoli: The medial and lateral projections at the ankle, formed by the tibia and fibula, respectively.

• Tarsals, Metatarsals, and Phalanges: The bones of the ankle, foot, and toes.

Example: The calcaneus (heel bone) is the largest tarsal bone and forms the prominence of the heel.

Table: Major Bones of the Lower Limb

Bone	Location	Key Features
Femur	Thigh	Head, neck, greater and lesser trochanters, condyles
Patella	Knee	Sesamoid bone, articulates with femur
Tibia	Medial leg	Medial malleolus, tibial tuberosity
Fibula	Lateral leg	Lateral malleolus
Tarsals	Ankle	Calcaneus, talus, navicular, cuboid, cuneiforms
Metatarsals	Foot	Numbered I-V from medial to lateral
Phalanges	Toes	Proximal, middle, distal (except hallux)

Section 8-5: Differences in Sex and Individual Skeletal Variation

Sexual Dimorphism in the Human Skeleton

There are distinct differences between male and female skeletons, especially in the pelvis, which are adaptations for childbirth in females.

• General appearance: Male skeletons are generally larger and more robust; female skeletons are smaller and lighter.

• Pelvic inlet: Wider and more circular in females; narrower and heart-shaped in males.

• Pubic outlet: Larger in females to facilitate childbirth.

• Pubic angle: Greater in females (usually >90°) than in males (usually

Additional info: Other differences include the shape of the sacrum, coccyx, and the relative size of muscle attachment sites.