Final answer:
Humans have abductor muscles in the hips and glutes, such as the gluteus maximus and gluteus medius, to stabilize the body, maintain posture, and allow for movements like walking and standing. The pelvic girdle offers limited range of motion but provides the necessary support for bipedal locomotion. Muscular adaptations, including the angling of the femur and spinal curves, contribute to the ability to walk upright.
Step-by-step explanation:
Humans have abductors in our hips and glutes to facilitate movement, stabilize our posture, and maintain our center of gravity. The pelvic girdle attaches the legs to the axial skeleton and is designed to support the upper body's weight and help transfer it to the lower limbs. The psoas major and iliacus form the iliopsoas in the gluteal region, assisting in leg movements. The gluteus maximus, gluteus medius, and gluteus minimus are part of the gluteal muscles which play crucial roles in extending and abducting the femur. These muscles are integral to humans' ability to maintain upright posture and perform motions such as walking, running, and standing.
Unlike the pectoral girdle, which allows a wide range of motion for arm movements, the pelvic girdle provides limited movement because it serves as a stable base for the lower body. This stability is crucial for bipedal locomotion, as it aids in the efficient transfer of energy and supports the body's weight during movement. The angling of the femur inward at a valgus angle is an important anatomical adaptation that positions the knees and feet under the center of the pelvis, contributing to successful bipedalism.
The powerful gluteus maximus along with other muscles forms the iliotibial tract, while muscles such as the tensor fascia lata, piriformis, obturators, gemelli, and quadratus femoris are key lateral rotators of the femur at the hip. Additionally, muscles on the medial part of the thigh, including the adductor longus, adductor brevis, and adductor magnus, adduct the thigh and medially rotate it.