Chapter 10 - Section 10.5 - Study Guide - Assess Your Learning Outcomes - Page 372: 3

These muscles play a crucial role in external (outward) rotation of the thigh at the hip joint. Let's take a closer look at each of these muscles: 1. **Gemellus Superior:** - The gemellus superior is a small muscle that lies deep within the hip joint. - It assists in external rotation of the thigh. 2. **Gemellus Inferior:** - The gemellus inferior is another small muscle located deep in the hip joint. - It also contributes to the external rotation of the thigh. 3. **Obturator Externus:** - The obturator externus is a flat, fan-shaped muscle that covers the outer surface of the obturator membrane and adjacent bone. - It is responsible for externally rotating the thigh and providing stability to the hip joint. 4. **Obturator Internus:** - The obturator internus is a muscle that lies deep within the pelvis, passing through the lesser sciatic foramen. - It plays a significant role in external rotation of the thigh. 5. **Piriformis:** - The piriformis is a triangular-shaped muscle located deep in the buttock. - It is one of the key muscles responsible for external rotation of the thigh, as well as abduction (moving the thigh away from the midline of the body). 6. **Quadratus Femoris:** - The quadratus femoris is a flat, square-shaped muscle located on the posterior aspect of the hip joint. - Its primary function is to assist in external rotation of the thigh. These muscles work together to facilitate the rotation of the thigh at the hip joint. They are essential for various activities such as walking, running, and maintaining balance. Additionally, they play a role in stabilizing the hip joint and contributing to the overall functionality of the lower extremities.

These muscles play a crucial role in external (outward) rotation of the thigh at the hip joint. Let's take a closer look at each of these muscles: 1. **Gemellus Superior:** - The gemellus superior is a small muscle that lies deep within the hip joint. - It assists in external rotation of the thigh. 2. **Gemellus Inferior:** - The gemellus inferior is another small muscle located deep in the hip joint. - It also contributes to the external rotation of the thigh. 3. **Obturator Externus:** - The obturator externus is a flat, fan-shaped muscle that covers the outer surface of the obturator membrane and adjacent bone. - It is responsible for externally rotating the thigh and providing stability to the hip joint. 4. **Obturator Internus:** - The obturator internus is a muscle that lies deep within the pelvis, passing through the lesser sciatic foramen. - It plays a significant role in external rotation of the thigh. 5. **Piriformis:** - The piriformis is a triangular-shaped muscle located deep in the buttock. - It is one of the key muscles responsible for external rotation of the thigh, as well as abduction (moving the thigh away from the midline of the body). 6. **Quadratus Femoris:** - The quadratus femoris is a flat, square-shaped muscle located on the posterior aspect of the hip joint. - Its primary function is to assist in external rotation of the thigh. These muscles work together to facilitate the rotation of the thigh at the hip joint. They are essential for various activities such as walking, running, and maintaining balance. Additionally, they play a role in stabilizing the hip joint and contributing to the overall functionality of the lower extremities.