Origins and Insertions Worksheet

Transcription

1 Origins and Insertions Worksheet First, understanding various boney markings and joint structure will help in determining movements that associated with each muscle. For example, if we are analyzing the sternocleidomastoid muscle it may be obvious what the origins and insertions of the muscle are- since the muscle is named on its origin and insertion. A general approach for how we should analyze any muscle in the body requires observations of increasing details. Step one: What are the names of the bones involved? (Axial or Appendicular: i.e. temporal and clavicle) Step two: What part of the bone does the muscle attach to? (Proximal or distal/portion) Step three: What is the name of the boney marking? Second, review the joint that the muscle will cross. A muscle can t cause an action for a joint it doesn t cross. Samples to get you started: The occipital-atlantial joint is an articulation between the bone and cervical vertebrae number. The atlanto-axial joint is an articulation between cervical vertebrae number and vertebrae number 2. The sterno-clavicular joint is an articulation between the head of the clavicle and the manubrium of the. Do not be fooled by how little movement there appears to be between any bones- you probably do not realize just how diarthrotic the sterno-clavicular joint really is. Since there are muscles attaching to the clavicle, it must be moveable. Remember that bones are rigid. Origin and insertion of Sternocleidomastoid When we are trying to figure out origins and insertions it is important to remember that immovable bone which a muscle attaches to is the and the movable part is the. Rotating your head left and right, keep one on your clavicle. Does the bone move? If you place your hands on the top of your chest just below your neck you should not feel any movement at all. Therefore the sternum and the clavicle represent the of the sternocleidomastoid muscle.the part of your body that is moving, however, is the skull. The process of the bone is the insertion, since it acts on the movable lever.

2 Actions of Sternocleidomastoid The primary actions of the sternocleidomastoid muscles are the the neck, and if one contracts it will rotate the head to the side. Now try the same movement with lateral flexion of the neck (if you don t remember what lateral flexion is, deduce the word lateral=away from the midline and flexion=decreasing an angle. When a muscle contracts it decreases in. When an antagonist acts, the original primary mover yields and in length. Once you have all of the movements of the sternocleidomastoid do not forget to record these on pages 102/103 of your lab manual. Let s take a look at two other muscles using a similar method of analyzing origin, insertion, and action. DELTOID AND TRAPEZIUS MUSCLE The actions of the trapezius muscle include:,, and depression of the. This bone therefor acts as a lever. The trapezius also assists in upward rotation of the and the, which is another lever. This new lever was of particular importance when we were analyzing the sternocleidomastoid muscle. So is the trapezius a (pick one: fixer/synergist/antagonist) to the actions of the sternocleidomastoid muscle? The trapezius can also participate in of the neck. If place your hands on the back of your neck and move from a flexed position into extension, you can feel the trapezius contracting. The actions of the deltoid muscle include of the shoulder. The anterior portion of the deltoid performs and rotation of the humerus, and the posterior portion of the deltoid performs and rotation of the humerus Before you go and look up one or the other in the book, try to think about how the anterior and posterior parts would be related to the pectoral girdle. The deltoid is a pennate muscle (review page 252). Since there are three tendons running through the muscle, the muscle has multiple actions depending on what side of the lever the muscle is acting on. This means the anterior and posterior portion perform dual roles in movement. Common Muscle attachments There are two levers that the deltoid and trapezius have in common as the produce movement: the and. For one muscle the scapula must be held still so the humerus can become movable, the muscle that acts on the humerus is the muscle. For the other muscle,, the scapula must be movable while the origin is held still. Therefore, the origin of the muscle is on the scapula and the insertion of the muscle is on the scapula. What are the exact boney marking these muscles originate and insert on? 1) 2) and of the.

3 Now if we know that the origin of the deltoid is the, and that the muscle performs movement on the humerus, we know that the insertion must lie somewhere on the humerus (proximal or shaft or distal?). If we recall what we know about boney markings, the place on the humerus for the deltoid to insert, is the deltoid of the humerus. The next section will help to review boney markings. Using the white boards practice this method of analysis for three more muscles. Begin with a general understanding and move to more complex details with confidence. Important facts to review 1. Sometimes, boney markings may be identified by the muscles which attach to them, for instance the of the deltoid muscle attaches to the deltoid of the humerus. The iliac fossa is the origin of the muscle. The lines of the ilium are an origin for the gluteus maximus/medius/minimus. 2. Muscle are grouped in pairs and can be located in muscle compartments. These compartments allow for an agonist/antagonist relationship between muscles. For instance, name the actions of the following muscles, as well as the antagonistic action. The antagonistic action is the pull of the antagonist which will make the primary mover return to its noncontracted position (yield and become longer: relaxed). Muscle Primary Movement Antagonist Movement Long head biceps brachii Short head biceps brachii Long head triceps brachii Lateral head triceps brachii Medial head triceps brachii We can clearly see that the biceps brachii and the triceps brachii perform dual actions. Their origins are on the scapula near the glenoid cavity. The glenoid fossa of the is an articulation point for the head of the, this bone acts as a lever during flexion and extension. Recalling a type of projection for muscle attachment, we can establish that the origin of the biceps brachii is the supraglenoid tubercle, and the of the long head triceps brachii is the tubercle. The scapula is a very important site for the origins of these muscles, the short head of the biceps brachii has its origin at the process of the scapula while the long head origin is the. Use your

4 book to find the origins of the lateral and medial triceps brachii muscles and don t forget to record them in your lab manual on pages 102 and 103. The insertions of the biceps and triceps brachii muscles have similar dualities and both insert on the proximal part of the and bones respectfully. Since the muscles perform opposite actions, they need to attach to different points of the anti. In this case, however, they insert on two levers. The insertion of the biceps brachii muscles is the tuberosity. The insertion of the triceps brachii muscles is the process of the ulna. Another example of opposite actions occurs between the tibialis anterior muscle and the peroneus/fibularis longus muscles. First, think about the general location of each muscle: the Tibialis Anterior is located in compartment, whereas, the Peroneus longus is located in the compartment. Use the following chart to record the actions of these muscles on the foot at the ankle. MUSCLE Primary Action on foot Antagonist Action Tibialis Anterior Peroneus Longus One muscle performs dorsiflexion at the ankle, and another performs plantar flexion at the ankle. In the book, the insertion is listed as the medial cuneiform and the base of the first metatarsal bone. The muscle which performs dorsiflexion is going to insert on the superior portion of the medial cuneiform, while the muscle inserts on the inferior portion. Note the specific path of travel for the two tendons. The tendon of the travels behind the lateral and inferior to the plantar surface? Also consider the Sartorius and Rectus Femoris muscles and their action on the leg. Both muscles are located in the anterior compartment of the leg and have an origin on the. At the point of origins which muscle is more superficial?. This thought helps to understand why the is the origin for the Sartorius while the is the origin for the rectus femoris. Viewing the belly of each muscle which muscle will remain in the anterior most position?. This thought helps to understand why the action on the leg are different. Muscle Action on the Leg Flexion Extension

5 If the Rectus Femoris has its insertion at the anterior of the result is of the leg (increasing the angle). Then the muscle which performs flexion has its insertion medially on the proximal part of the it will the angle between the and the. Muscles with the same origin that cross the same joints have the similar actions. For instance, located in the posterior compartment of the thigh, have the common origin of the. This group of muscles also cross two joints, the joint and the joint. If we add a short muscle located in the posterior compartment that crosses only the knee joint we would call this group of muscle the. Remember a muscle can only act on a joint that is crosses. Therefore the muscle will only act to the leg across the knee joint. In the anatomical position the leg is, therefore the action on decreasing the angle must occur in a posterior direction (not anteriorly like most of the other joints). Keep it simple: Lock in general relationships first and then move to more specific or detailed relationships.