In Depth: Muscles
An important group of muscles in the pelvis is the pelvic floor. The pelvic floor muscles provide foundational support for the intestines and bladder. They also help the anus function. In women, these muscles also help push a baby through the vaginal opening during childbirth and support the uterus. These muscles are located on the inner portion of the pelvic bones.
In front of the pelvis and extending upward, the muscles of the abdomen play a large role in maintaining posture and supporting the spine. They also protect the organs situated underneath them. These muscles also compress the organs underneath them to help with bodily functions such as coughing, urination, defecation, sneezing, and vomiting.
The muscles that make up the abdominal wall are the external oblique, internal oblique, rectus abdominis, and the transverse abdominis. These muscles are covered by a crisscrossing pattern of tissue. Together, these whitish connective tissues make a covering known as the rectus sheath.
The rectus sheath has two layers: the Camper’s fascia and the Scarpa’s fascia. Both are made up of adipose tissue, otherwise known as fat. The abdominal area is a common place for fat to accumulate.
In the back of the torso, the latissimus dorsi is a large, rectangular muscle that extends from the lower back near the top of the pelvis to near the shoulder. Its primary role is in arm movement, but it also assists in moving the spine.
Below the latissimus dorsi is the gluteus maximus, the muscle that gives the buttocks their shape. This muscle’s large size is due to fact that it plays an important role in standing upright, walking, and running by extending the thigh. It partially covers the gluteus medius, a smaller muscle that pulls the thigh in.
Other muscles close to the skin that affect leg movement include:
- Tensor fascia lata: This long thin muscle stabilizes the hip and knee joints. It runs from the hip bone to the tibia, or shinbone, on the outside of the thigh.
- Gracilis: Another long thin muscle, it extends from the pubis bone to the lower end of the femur at the knee on the inside of the thigh. Its primary function is to bring the hip inward, but it also helps flex the knee.
- Sartorius: Like the gracilis, this long muscle aids the hip and flexes the knee. It runs from the hip bone to the tibia, on the inside of the thigh.
- Rectus femoris: One of four quadriceps muscles in the thigh, this muscle attaches to the kneecap. It helps flex the knee but has the least effect compared with the other three quadriceps muscles.