Exam 10: B: Articulations

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Flexion and extension are two fundamental types of movements that occur in the joints of the body, allowing for changes in the angle between bones or body parts.

Flexion refers to a bending movement that decreases the angle between two body parts. This movement is typically directed anteriorly (forward) in the sagittal plane. An example of flexion is bending the elbow to bring the hand closer to the shoulder, which decreases the angle between the forearm and the upper arm.

Extension is the opposite of flexion; it involves a straightening movement that increases the angle between body parts. Extension is typically directed posteriorly (backward) in the sagittal plane. An example of extension is straightening the elbow, which increases the angle between the forearm and the upper arm, returning the arm to a straight position.

These movements are common in hinge joints like the elbow and knee, but they also occur in ball-and-socket joints such as the shoulder and hip, as well as in other types of joints throughout the body. Flexion and extension are essential for a wide range of everyday activities, including walking, sitting, standing, and grasping objects.

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The symphysis pubis is a cartilaginous joint located between the left and right pubic bones near the front of the pelvis. This joint is made up of fibrocartilage and allows for a slight degree of movement, which is necessary for several reasons:

1. Childbirth: In females, the slight movement of the symphysis pubis is crucial during childbirth. The flexibility of this joint allows the pelvis to expand slightly, facilitating the passage of the baby through the birth canal. Hormonal changes during pregnancy, particularly the release of the hormone relaxin, increase the flexibility of the symphysis pubis to prepare for delivery.

2. Biomechanical Adaptation: The slight movement of the symphysis pubis contributes to the overall adaptability and flexibility of the pelvic girdle. This flexibility helps to absorb and distribute the forces that are transmitted through the pelvis during activities such as walking, running, and jumping. Without this movement, the rigid bones of the pelvis would be more susceptible to stress and injury.

3. Load Bearing and Balance: The pelvis plays a key role in supporting the weight of the upper body and in maintaining balance. The ability of the symphysis pubis to move slightly helps to balance the distribution of weight and adapt to changes in posture and body position.

4. Shock Absorption: The fibrocartilaginous nature of the symphysis pubis provides a degree of cushioning and shock absorption for the pelvis. This is particularly important for protecting the pelvic and abdominal organs from the impact of various movements and forces.

Overall, the slight movement of the symphysis pubis is a necessary feature of human anatomy that contributes to the flexibility, adaptability, and functionality of the pelvic region. It plays a vital role in everyday movements as well as in special circumstances such as childbirth.