Question

There are many similarities within our own bodies and the upper extremity often mirrors the lower extremity. Choose 2 joints, one upper and one lower extremity, and describe how the bones and joint structures are similar. Why do you think our bodies have these similarities?

Answer 1

The upper and lower limb have marked differences such as joints of upper limb are smaller compared to that of lower limb.
Also the lower limb is responsible for weight bearing and locomotion. The upper limb is responsible for reaching out, grasping and gripping of objects.
But there are also some similarities between the gross anatomy of upper and lower limb.
The two joints of upper and lower limb that exhibits similarities in their gross structure and function are hip joint and shoulder joint.
The shoulder joint is the largest joint of upper limb that forms the pectoral girdle. Similarly the hip jont is the largest joint of lower limb that forms the pelvic girdle.
The shoulder joint connects the upper limb to the trunk. Similarly the hip joint connects the lower limb to the trunk.
The shoulder consists of two bones scapula and humerus. The head of humerus articulates the scapula at a cavity known as glenoid cavity. Similarly the hip joint consists of two bones the pelvic bone and the femur. The head of femur articulates with the cavity on pelvic bone known as acetabulum.
The head of humerus is firmly enclosed within the glenoid cavity with the help of glenoid labrum and the capsule. Similarly head of femur is firmly enclosed within the acetabulum with help of acetabular labrum and a capsule.
The shoulder joint provides attachment to various muscles that help move the shoulder joint and ligaments that provide joint stability. Hip joint also provides attachment to various muscles and ligaments.
The shoulder joint and hip joint both are synovial joint of ball and socket variety and provide a wide degree of movement. Shoulder and hip joint exhibit flexion, extension, abduction, adduction, internal and external rotation movement.