Parts of the Femur and Their Biological Significance
The femur is known as the heaviest, most extended, and strongest bone in a human body. Here are some critical details about it:
The primary function of this bone is handling weight and ensuring the stability of gait, which is an essential component of the lower kinetic chain.
The weight of the upper body sits on two femoral heads. The capsular ligament is a more robust and thicker sheath that wraps around the acetabulum periosteum and proximal femur. This ligament holds the femoral head in the acetabulum.
Femur's robust shape provides several sturdy attachment points for stronger muscles of the hip and knee, and they all contribute to walking and other propulsive actions.
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Parts of Femur
The femur acts as the origin and attachment point for many muscles and ligaments. It can be divided into three main parts, as follows:
1. Proximal Femur:
It contains the femoral head pointed in a superior, medial, and slightly anterior direction. Ligamentum teres femoris helps connect the acetabulum to the fovea capitis femoris, a pit on the head. The pyramid-shaped neck attaches the spherical head at the apex and the cylindrical shaft at the base. They are attached to two prominent bony protrusions for the movement of muscles and knees, the greater and the lesser trochanter.
2. Shaft:
It contains a mild anterior arch.
3. Distal Femur:
The shaft flares out like a cone on to a cuboidal base made of the medial and lateral condyle. They join the femur to the tibia and form the knee joint.
Osteological Features of Femur
Proximal Femur:
At the femur's proximal end, the bulbous femoral head joins with the femur's shaft by the femoral neck. The medically oriented lesser and greater trochanters lie at the neck's base. A rough line named the intertrochanteric line connects the more significant and lesser trochanters on the femur's anterior part. In comparison, there is a smoother intertrochanteric crest that connects the trochanters from the posterior.
Inclination Angle- The angle between the femoral shaft's medial side and the femoral neck, as viewed from the frontal. This angle is greater during birth and decreased during childhood and adolescent development due to added loading stress across the femoral neck while walking and bearing weight. The normal inclination angle is 125-degrees, and it increases the femur's mobility at the hip joint by placing the femoral head and neck in a favourable walking position. There are abnormal angles, too: coxa vara, less than 125-degree and coxa valga, greater than 125-degree. Both the abnormal angles alter the biomechanics and lead to malalignment and other complications.
Femoral Shaft:
The femur shaft courses on an oblique, medial to lateral angle and functions to bring knees' alignment and feet closer to the midline. Shaft's cross-section is in the middle and is circular, but it is posteriorly flattened at proximal and distal aspects. Here is a brief on it:
Posterior Surface Shaft: These are the rough ridges of bones, known as linea Aspera. They then split inferiorly, forming the medial and lateral supracondylar lines. The flat popliteal surface then lies in between.
Proximally: Linea Aspera’s medial border becomes a pectineal line. The lateral border transforms into the gluteal tuberosity, attaching the gluteus maximus.
Distally: Linea Aspera widens, forming the popliteal fossa floor, medial and lateral borders from medial and lateral supracondylar lines. This medial supracondylar line ends when it reaches the abductor, the tubercle, attaching the adductor Magnus there.
Distal Femur:
At the distal femur end, prominent lateral and medial condyles form. An epicondyle then projects from each condyle and acts as an attachment site for collateral ligaments. Medial and lateral condyles then get separated by an intercondylar notch.
Blood Supply
The femoral artery mainly supplies blood to the lower extremity. Here is more about the blood supply around the femur:
Medial circumflex and anastomoses supply femoral heads with Obturator and circumflex artery. The femoral artery is branched into medial and lateral circumflex, and the internal iliac artery is branched into the obturator artery.
The foveal artery comes out of the obturator artery, running through ligamentum teres femoris and acting as a supportive blood supply to the femoral head.
The deep femoral artery's perforating branches supply the distal and shaft portion of the femur.
FAQs on Understanding the Femur: Anatomy and Importance
1. What is the femur bone, and where is it located in the human body?
The femur, commonly known as the thigh bone, is the longest, heaviest, and strongest bone in the human body. It is located in the upper leg, forming the link between the hip joint and the knee joint. Specifically, its upper (proximal) end articulates with the pelvic girdle, and its lower (distal) end connects to the tibia and patella.
2. What are the primary functions of the femur?
The femur is essential for several critical bodily functions. Its primary roles include:
- Weight Bearing: It supports the entire weight of the upper body during activities like standing, walking, and running.
- Locomotion: It acts as a crucial lever for the powerful muscles of the thigh, enabling a wide range of movements at both the hip and knee.
- Muscle Attachment: Its surface provides numerous attachment points for muscles and ligaments that control leg movement and stability.
- Haematopoiesis: The bone marrow within the femur is a major site for the production of red blood cells, white blood cells, and platelets.
3. How are the major muscles of the thigh organised around the femur?
The muscles surrounding the femur are organised into distinct compartments, each with a primary function:
- Anterior Compartment: Contains muscles like the quadriceps femoris, which are primarily responsible for knee extension and hip flexion. The femur itself lies within this compartment.
- Posterior Compartment: Houses the hamstring muscles (e.g., biceps femoris), which are responsible for knee flexion and hip extension.
- Medial Compartment: Includes the adductor muscles, which pull the leg towards the body's midline (adduction).
- Gluteal Compartment: Connects to the proximal femur and is responsible for hip extension, abduction, and rotation.
4. What are the main anatomical parts of a femur as per the Biology syllabus?
The femur is divided into three main sections:
- Proximal Femur: The upper end that articulates with the hip bone. It includes the femoral head (the ball of the ball-and-socket joint), the femoral neck, and the greater and lesser trochanters, which serve as important sites for muscle attachment.
- Shaft (Body): The long, cylindrical middle section of the bone that provides its length and strength.
- Distal Femur: The lower end that forms the knee joint. It features the medial and lateral condyles, which are smooth, rounded surfaces that articulate with the tibia.
5. Why is the femur considered the strongest bone in the human body?
The femur's incredible strength is due to its unique structure and composition. It has a very dense and thick outer layer of compact bone, particularly along its shaft, which is designed to withstand immense pressure and torsion. Furthermore, its slightly bowed or arched shape helps distribute body weight and mechanical stress effectively, preventing fractures under normal loads. This robust design is a critical evolutionary adaptation for upright posture and bipedal locomotion.
6. What are some common injuries and conditions related to the femur?
Due to its strength, injuring the femur typically requires significant force. Some common conditions and injuries include:
- Femoral Fractures: A break in the bone, which can occur at the neck (common in elderly individuals with osteoporosis) or the shaft (usually from high-impact trauma like a car accident). A femur fracture is a serious medical emergency.
- Stress Fractures: Incomplete cracks in the bone caused by repetitive force, often seen in athletes.
- Patellofemoral Pain Syndrome: A common condition causing pain around the kneecap, where the femur and patella interact.
7. How does the structure of the femur's proximal and distal ends relate to their function in joints?
The shape of each end of the femur is perfectly adapted for its specific joint function. The proximal end has a smooth, spherical head that fits into the acetabulum of the pelvis, forming a highly mobile ball-and-socket joint. This allows for a wide range of motion. In contrast, the distal end has two large, rounded condyles that articulate with the tibia to form a hinge joint. This structure primarily allows for flexion and extension (bending and straightening), providing stability for weight-bearing at the knee.
8. Besides movement and support, what other vital biological role does the femur play?
Beyond its obvious mechanical functions, the femur is a key player in haematopoiesis—the process of creating new blood cells. The hollow cavity of the femur's shaft is filled with red bone marrow, especially in children and at the proximal end in adults. This tissue is responsible for producing red blood cells (for oxygen transport), white blood cells (for immunity), and platelets (for clotting), making the femur essential for maintaining the body's blood supply.
