Origin, Insertion, and Function

• The point of origin on a muscle is the attachment site that doesn't move much during contraction.
• The point of insertion on the muscle is the attachment site that does move during contraction.
• The deep muscles of the vertebral column include the spinalis, longissimus, and the iliocostalis. They are all responsible for extending and laterally flexing the spine.
• The spinalis muscle originates and inserts on the cervical and thoracic vertebrae of the spine.
• The longissimus muscle originates on the cervical, thoracic, and lumbar vertebrae, and inserts on the cervical and thoracic vertebrae as well as the mastoid process.
• The iliocostalis muscle originates at the sacrum, lumbar vertebrae, and ribs, and inserts on the ribs and cervical vertebrae.
• The muscles that make up the rotator cuff are the supraspinatus, infraspinatus, teres minor, and subscapularis. They are responsible for stabilizing the shoulder joint.
• The biceps brachii originates at the tip of the coracoid process (short head), and the supraglenoid tubercle (long head). Its insertion point is on the radial tuberosity, and the muscle is responsible for flexing the elbow when in a supine position.
• The muscles in the quadriceps group include the rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis. They are responsible for knee extension and hip flexion.
• The quadricep muscles join at a common tendon (the patellar tendon), which wraps around the patellar ligament and inserts on the tibial tuberosity.
• The rectus femoris muscle originates on the anterior inferior iliac spine.
• The muscles that make up the hamstring group are the biceps femoris, semimembranosus, and semitendinosus. All three originate at the ischial tuberosity. They function as a hip extensor, knee flexor, and internally rotates the knee.
• The biceps femoris originates at the ischial tuberosity and the linea aspera, and inserts at the head of the fibula. Its function is as a hip extensor and knee flexor, it also internally rotates the flexed knee.
• The tensor fasciae latae originates on the anterior iliac crest and inserts on the iliotibial band. It is responsible for flexing, abducting, and medially rotating the thigh.
• The sartorius muscle originates on the anterior superior iliac spine and inserts on the medial surface of the tibia. Its function is flexion and outward rotation of the hip as well as knee flexion.
• The iliopsoas muscle is formed by the iliacus muscle and the psoas major muscles. The iliacus originates on the inner surface of the ilium, and the psoas major on the lumbar vertebrae. They both form a common tendon and insert on the lesser trochanter of the femur. The muscle functions as a hip and trunk flexor.
• The deltoid muscle originates on the clavicle, acromion, and spine of the scapula. The anterior, lateral, and posterior heads meet at a common insertion point on the humerus, the deltoid tuberosity. It is responsible for flexing and medially rotating the shoulder joint, abducts the arm, and extends and laterally rotates the arm.