Anatomy & Physiology I: Lower Limb Bones (Lab Practical II Review, Lessons 8–12)

Lesson 8: The Leg - Bones

Overview of the Pelvic Girdle

The pelvic girdle is a ring-like bony structure located at the base of the spine, connecting the axial skeleton to the lower limbs. It is composed of the two hip bones (ossa coxae), sacrum, and coccyx.

• Ilium: The broad, flaring portion of the hip bone.

• Ischium: The lower, posterior portions of the pelvis.

• Pubis: The anterior portion of the pelvic bone.

• Acetabulum: The deep socket that receives the head of the femur.

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

Femur: Structure and Features

The femur is the longest and strongest bone in the human body, forming the thigh. It articulates proximally with the pelvis at the acetabulum and distally with the tibia and patella.

• Head: The rounded proximal end that fits into the acetabulum.

• Neck: The constricted region just distal to the head.

• Greater and Lesser Trochanters: Large projections for muscle attachment.

• Linea aspera: A ridge on the posterior shaft for muscle attachment (visible only posteriorly).

• Intercondylar fossa: A deep notch between the posterior surfaces of the condyles (visible only posteriorly).

Example: The linea aspera and intercondylar fossa are two features of the femur only visible from the posterior view.

Tibia and Fibula: Structure and Features

The tibia and fibula are the two bones of the lower leg. The tibia is the larger, medial bone, while the fibula is slender and lateral.

• Tibia: Bears most of the body’s weight; features include the medial and lateral condyles, tibial tuberosity, anterior border, medial malleolus, and intercondylar eminence.

• Fibula: Serves mainly for muscle attachment; features include the head and lateral malleolus.

Key Point: The medial malleolus is found on the tibia, while the lateral malleolus is found on the fibula.

Key Point: The tibia is medial to the fibula (not lateral).

Foot Bones and Phalanges

The foot consists of tarsal bones, metatarsals, and phalanges. The phalanges are the bones of the toes.

• Phalanges: Each toe has three phalanges (proximal, middle, distal), except the hallux (big toe), which has only two (proximal and distal).

Example: The statement "all the phalanges are made up of three bones" is false because the big toe has only two phalanges.

Identification of Bone Features (Sample Table)

The following table summarizes key features of the femur, tibia, and pelvis as referenced in the review questions and diagrams.

Bone	Feature	Description
Femur	Head	Articulates with acetabulum of pelvis
Femur	Linea aspera	Posterior ridge for muscle attachment
Tibia	Medial malleolus	Medial ankle prominence
Fibula	Lateral malleolus	Lateral ankle prominence
Pelvis	Acetabulum	Socket for femoral head

Summary of True/False Statements

• In the foot, all the phalanges are made up of three bones: False (the big toe has only two phalanges).

• The medial and lateral malleolus are found on the tibia: False (medial is on tibia, lateral is on fibula).

• The tibia is lateral to the fibula: False (the tibia is medial to the fibula).

Additional info:

• For identification of labeled features, students should be able to recognize anatomical landmarks such as the iliac crest, ischial tuberosity, pubic symphysis, greater and lesser trochanters, and condyles on diagrams or models.

• Understanding the orientation (anterior vs. posterior) is crucial for identifying features visible only from certain views.