Chapter 10 - Section 10.5 - Study Guide - Assess Your Learning Outcomes - Page 372: 1

The iliopsoas muscle is a major muscle of the hip joint that plays a crucial role in hip flexion and stability of the lumbar spine. It is actually composed of two separate muscles: the iliacus and the psoas major. Let's take a closer look at each of these muscles: 1. **Iliacus Muscle:** - The iliacus muscle is the flat, triangular-shaped muscle located in the iliac fossa of the pelvis. - It originates from the iliac crest (the upper part of the pelvic bone) and the inner surface of the ilium (the largest bone of the pelvis). - The iliacus muscle then inserts onto the lesser trochanter of the femur (the bone of the thigh). - Functionally, the iliacus is responsible for flexing the hip joint, and it works in conjunction with the psoas major to perform this action. 2. **Psoas Major Muscle:** - The psoas major is a long, thick muscle that runs from the lumbar spine (specifically, the bodies and transverse processes of the lumbar vertebrae) down to the lesser trochanter of the femur. - The psoas major is often referred to as the "iliopsoas" along with the iliacus because these two muscles are closely related and share a common insertion point. - It plays a major role in flexing the hip joint and also contributes to stabilizing the lumbar spine, particularly during activities like sitting up from a lying position or lifting the legs. Together, the iliacus and psoas major muscles work synergistically to flex the hip joint. They are essential for activities such as walking, running, and climbing stairs. Additionally, they play a role in maintaining proper posture and providing stability to the lower back and pelvis. These muscles are commonly referred to as the "hip flexors," and they are involved in a wide range of movements and activities in our daily lives. Proper conditioning and flexibility of the iliopsoas muscles are important for overall lower body function and comfort.

The iliopsoas muscle is a major muscle of the hip joint that plays a crucial role in hip flexion and stability of the lumbar spine. It is actually composed of two separate muscles: the iliacus and the psoas major. Let's take a closer look at each of these muscles: 1. **Iliacus Muscle:** - The iliacus muscle is the flat, triangular-shaped muscle located in the iliac fossa of the pelvis. - It originates from the iliac crest (the upper part of the pelvic bone) and the inner surface of the ilium (the largest bone of the pelvis). - The iliacus muscle then inserts onto the lesser trochanter of the femur (the bone of the thigh). - Functionally, the iliacus is responsible for flexing the hip joint, and it works in conjunction with the psoas major to perform this action. 2. **Psoas Major Muscle:** - The psoas major is a long, thick muscle that runs from the lumbar spine (specifically, the bodies and transverse processes of the lumbar vertebrae) down to the lesser trochanter of the femur. - The psoas major is often referred to as the "iliopsoas" along with the iliacus because these two muscles are closely related and share a common insertion point. - It plays a major role in flexing the hip joint and also contributes to stabilizing the lumbar spine, particularly during activities like sitting up from a lying position or lifting the legs. Together, the iliacus and psoas major muscles work synergistically to flex the hip joint. They are essential for activities such as walking, running, and climbing stairs. Additionally, they play a role in maintaining proper posture and providing stability to the lower back and pelvis. These muscles are commonly referred to as the "hip flexors," and they are involved in a wide range of movements and activities in our daily lives. Proper conditioning and flexibility of the iliopsoas muscles are important for overall lower body function and comfort.