Key Features and Functions of the Sartorius Muscle
It is the longest muscle of the human body along with the quadriceps femoris, which belongs to the anterior muscles of the thighs. It is found slanted throughout the course of thighs, which arises from the anterior superior iliac spine and crosses to the medial side of the thighs.
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Finally, it inserts to the medial side of the proximal tibia. Due to the slanted nature of the sartorius muscle, it flexes, abducts and externally rotates the thighs, flexes, and internally rotates the leg.
Structure
The muscle sartorius originates from the anterior superior iliac spine and a part of this muscle is between the anterior superior iliac spine and anterior inferior iliac spine. Sartorius’s muscle runs slantly across the upper and anterior part of the thigh, and it passes behind the medial condyle of the femur to the end in a tendon. This tendon curves to the front to join the gracilis muscles and the semitendinosus muscles in the pes anserinus, where it attaches to the upper surface of the tibia.
The upper portion of the sartorius muscle forms a lateral border of the femoral triangle and a point, where it crosses the adductor longus marks the apex of the triangle. The depth of the sartorius and its fascia is the adductor canal, through which the saphenous nerve passes, the femoral artery and vein, and the nerve to the vastus medialis.
Sartorius Muscle Origin and Insertion
Origin of sartorius muscle - The origin of the sartorius muscle is found in the anterior superior iliac spine and the upper half of the notch between the anterior superior iliac spine and the anterior inferior iliac spine. The fibre of this muscle forms a thin, flat muscle, which extends inferomedially across the anterior surface of the thigh.
Thus muscle descends vertically through the medial aspect of the thigh. And the muscle also crosses the medial side of the knee joint, which inserts on to the medial aspect of the proximal tibia, anterior to the gracilis and semitendinosus muscles.
Sartorius muscle insertion - The insertion of the three muscles forms a wide aponeurotic sheath known as the anserinus. In which some of the fibres (inferior part of the tendon) blend with the medial collateral ligament of the knee joint, and the deep fascia over the medial aspect of the leg. While some of the superior fibres blend with the knee joint capsule, these connections contribute to the medial stability of the knee joint.
Functions of the Sartorius Muscle
Some of the functions of the sartorius muscles are - it crosses both the hip and the knee joint, which produces the movement on both of them. And at the hip joint, it is capable of flexion, external rotation and abduction of the leg. The shrinkage action of sartorius muscle can also cause flexion to the knee joint and inward, or medial, rotation of the tibia against the femur.
The combination of all these movements stated above allows a person to sit in an area with opposite legs. However, the movements made by the sartorius cut were not limited to that one function. Sartorius muscle also may play an important role in climbing.
The Blood Supply in the Sartorius Muscle
As sartorius muscle is a long muscle it requires extensive vascular supply from several sources:
The third proximal receives the vascular supply from the branch of femoral, deep femoral branches, lateral femoral arteries and/or quadriceps artery (branch of the deep femoral artery or lateral circumflex).
The middle third is provided by the femoral artery branches.
A third of the distal receives blood supply to the female artery and the descending vein descends.
Do You Know?
What causes Sartorius muscle pain? If the bursa under the muscles of the sartorius, gracilis, and semitendinosus are prone to overuse or injury, a person can develop pain. This condition is more common in athletes from overuse and is a common cause of knee weakness and pain.
FAQs on Sartorius Muscle: Anatomy, Functions, and Importance
1. What are the origin and insertion points of the sartorius muscle?
The sartorius muscle originates from the anterior superior iliac spine (ASIS) of the hip bone. It then runs diagonally down across the front of the thigh and inserts on the medial surface of the upper part of the tibia, at a site known as the pes anserinus, along with the gracilis and semitendinosus muscles.
2. What are the primary functions of the sartorius muscle?
The sartorius muscle is unique because it acts on two joints: the hip and the knee. Its primary functions include:
- Flexion of the hip: Lifts the thigh upwards, as in marching.
- Abduction and lateral rotation of the hip: Moves the thigh outwards and rotates it.
- Flexion of the knee: Bends the knee.
- Medial rotation of the tibia: Turns the lower leg inwards when the knee is bent.
3. Why is the sartorius muscle often called the "tailor's muscle"?
The name "sartorius" comes from the Latin word sartor, meaning tailor. The muscle is called the tailor's muscle because it enables the cross-legged sitting position that tailors traditionally used while working. This position involves a combination of hip flexion, abduction, and lateral rotation, all of which are primary actions of the sartorius muscle.
4. Which nerve provides innervation to the sartorius muscle?
The sartorius muscle is innervated by the femoral nerve. This nerve originates from the lumbar plexus, specifically from the spinal nerve roots L2, L3, and L4. Damage to the femoral nerve can weaken or paralyze the sartorius, affecting its functions.
5. What makes the sartorius muscle structurally unique in the human body?
The sartorius muscle is notable for being the longest muscle in the human body. It is a long, thin, ribbon-like muscle that spans the entire length of the thigh, running from the hip to just below the knee. Its unique spiral path allows it to influence movement at both the hip and knee joints simultaneously.
6. How can a tight or overused sartorius muscle cause knee pain?
A tight sartorius muscle can cause pain, particularly on the inner side of the knee. This is because its tendon inserts at the pes anserinus on the tibia. Overuse or tightness can lead to inflammation of this tendon (tendinitis) or the underlying bursa (pes anserine bursitis), resulting in localized pain, swelling, and weakness, especially during activities like running or climbing stairs.
7. How does the sartorius muscle work synergistically with other muscles in the thigh?
The sartorius muscle rarely works in isolation and functions as a synergist with other muscle groups. For example:
- During hip flexion, it works with the iliopsoas and rectus femoris.
- For knee flexion, it assists the hamstring muscles (biceps femoris, semitendinosus, semimembranosus).
- At its insertion point, the pes anserinus, it works alongside the gracilis and semitendinosus muscles to provide stability to the medial side of the knee.
8. What is the biomechanical importance of the sartorius muscle's spiral path across the thigh?
The long, oblique path of the sartorius muscle provides a significant mechanical advantage. By crossing two joints (hip and knee), it acts as a dynamic stabilizer and a versatile mover. Its line of pull allows it to contribute to multiple actions (flexion, abduction, rotation) with a single contraction, making it highly efficient for complex movements like crossing the legs or kicking a ball with the inside of the foot.
