Muscular Function and Anatomy of the Upper Leg

Muscular Function and Anatomy of the Upper Leg
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  • 0:08 The Pelvic Girdle
  • 1:19 Muscles That Move the…
  • 3:40 Muscles That Move the Leg
  • 5:40 Lesson Summary
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Lesson Transcript
Instructor: Heather Adewale

Heather has taught reproductive biology and has researched neuro, repro and endocrinology. She has a PhD in Zoology/Biology.

Our legs allow us to do everything from walking to dancing to just standing still. All these actions involve the function of many muscles. Learn about the muscles above the knee in this lesson covering muscles of the hip, thigh, and leg.

The Pelvic Girdle

So, how many of you are runners? Or, who likes dancing, playing football, or maybe soccer? What do all of these sports have in common? Not sure? Well, it's a lot simpler than you might think. They all involve the use of your legs! The muscles of your legs are called appendicular muscles because they are attached to the bones of the appendicular skeleton. This attachment site is called the pelvic girdle, these bones here, which are attached to the axial skeleton here at the sacrum.

On top of the pelvic bones are muscles that move the hips, or pelvis. These movements consist mostly of rotation of the hips, side-to-side movement, or back-and-forth movements and are often paired with movements of the thigh or upper part of the leg. All of the muscles that move your legs can be divided into three groups: muscles that move the thigh, muscles that move the leg, and muscles that move the foot and toes. We'll start at the top, with the muscles that move the hip and thigh, and focus on the muscles above the knee in this lesson.

Muscles That Move the Hip and Thigh

First up: the gluteus maximus, or your butt muscle. This muscle is the largest and most well-known of the gluteal group of muscles, which includes the gluteus medius, maximus, and minimus, as well as the tensor fasciae latae. Together, these muscles extend, flex, and rotate the hip. The origin points for these muscles are on the posterior side of the illium of the pelvic bone, this part here. Some, like the gluteus maximus, have multiple origin points and also originate from the sacrum and coccyx, these bones here.

These muscles all insert either on the femur, the large bone of the upper leg, or the iliotibial tract. This is a tract of collagen fibers that extends from the hip along the thigh and down to the tibia of the lower leg, inserting just below the knee. This IT band, as it is commonly called, helps support the knee and flex, abduct, and rotate the thigh at the hip joint. Remember, abduction is the movement of a part of the body away from the center of the body, while adduction is movement toward the center of the body.

I know these terms are easy to confuse, but if you think about it, what does the word 'abduct' mean? If somebody is abducted by aliens, they are taken away from Earth, right? So 'abduction' equals 'away from,' while 'adduction' equals 'adding to' or 'bringing back towards' the body. Not so hard to remember now, right?

Underneath the gluteal muscles are other muscles involved in movement of the hip and thigh, the lateral rotator group, which, as its name suggests, rotates the hip laterally, away from the body, like this. Below this group are the adductors, which move the hip back toward the body. All of the adductor muscles, as their name suggests, perform hip adduction, and some also perform flexion and extension of the hip. Whenever someone suffers from a pulled groin, it's usually because one of these muscles has been injured.

Muscles That Move the Leg

Underneath the hip and thigh are the muscles that move the leg. These can be divided into muscles that flex the leg and those that extend the leg. This flexion and extension occurs at the knee. Most of the muscles involved in flexion of the knee and leg are located along the back (or posterior) and side surfaces of the leg.

These muscles include the biceps femoris. Hmm, that 'biceps' term sounds familiar, doesn't it? That's right; doesn't the biceps brachii flex the arm? Well, the biceps femoris flexes the leg at the knee. This can pull the lower leg up or move the entire leg back, away from the body. This motion is aided by other flexors, and together, they are referred to as the hamstrings. The hamstring muscles originate up here at the pelvic bone and insert down here on the tibia and fibula of the lower leg.

The hamstrings are the opposing muscles, or antagonists, to the quadriceps muscles located on the front, or ventral, side of the leg. When the quads contract to extend your knee, they pull your leg up and allow you to move it away from your body. In this way, they are the prime mover, or the agonist. When the hamstrings contract, they pull the leg back, toward your body. You can see this action most easily when you're walking or running.

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