Anatomy 201: Chapter 10 - The Muscular System

Forearm Muscles

Pronator teres brachioradials flexor carpi radialis palmaris longus extensor carpi radialis longus flexor carpi ulnaris extensor carpi ulnaris extensor digitorum

Abdomen Muscles

Rectus abdominus external oblique internal oblique transversus abdominis

Thigh Muscles

Tensor fasciae sartorius adductor longus gracilis, rectus femoris vastus lateralis vastus medialis illotibial tract aductor magnus hamstrings (biceps femoris, semitendinosus, semimembranosus)

Illustrate the criteria used to name muscles by providing an example, using each criterion

1. Location of the muscle: Some muscle names indicate the bone or body region with which the muscle is associated. For example, the temporalis muscle overlies the temporal bone, and inter-costal muscles run between the ribs. 2. Shape of the muscle: Some muscles are named fir their distinctive shapes. For example the deltoid muscle is roughly triangular (deltoid = triangle), and together the right and left trapezius muscles form a trapezoid. 3. Relative size of the muscle: Terms such as maximus (largest), minimus (smallest), longus (long) and brevis (short) are often used is muscle names as in gluteus maximus and gluteus minimus (the large and the small gluteus muscles, respectively). 4. Direction of the muscle fibers: The names of some muscles reveal the direction in which their fibers (and fascicles) run in reference to some imaginary line, usually the mid-line of the body or the longitudinal axis of a limb bone. in muscles with the term rectus (straight) in their names, the fibers run parallel to that imaginary line (axis), whereas the terms transverse and oblique indicate that the muscle fibers run respectively at right angles and obliquely to the line, specific examples include the rectus femoris ( straight muscle of the thigh or femur) and transverses abdominis (transverse muscle of the abdomen). 5. Number of origins: When biceps, triceps, or quadriceps forms part of a muscles name, you assume that the muscle has two, three, or four origins, respectively. For example, the biceps brachii muscle of the arm has two origins, or heads. 6. Location of the attachments: Some muscles are named according to their points, of origin, and insertion. the origin is always named first for instance, muscle of the neck has a dual origin on the sternum (Sterno) and clavicle (cleido), and it inserts on the mastoid process of the temporal bone. 7. Action: When muscles are named for the action, acion words such as flexor, extensor, or adductor appear in the muscles name. for example, the adductor longus, located in the medial thigh, brings about a high adduction, and the supinator muscle supinates the forearm. Often, several criteria are combined in the naming of a muscle. For instance, the name extensor carpi radialis longus tells us the muscles action (extensor), what joint it acts on (carpi = wrist), and that is lies close to the radius of the forearm (radialis); it also hints at its size (longus) relative to other wrist extensor muscles. unfortunately, not all muscle names are this descriptive.

Neck Muscles

1. Sternohyoid: (Most medial muscle of the neck, thin muscle covered inferiorly by the sternocleidomastoid.) 2. Sternocleidomastoid: (located on side of neck, massive muscle) Used when sitting up or rotating head towards shoulder on either side. 3. Epicranius: (frontal and occipital): Pulls scalp forward and backward. 4. Trapezius:

Shoulder Muscles

1. Trapezius: 2. Deltoi: 3. Infraspinatus: 4. Teres major: 5. Rhomboid major: 6. Latissmus dorsi:

Lever Systems: Bone-Muscle Relationships

A lever is a rigid bar that moves on a fixed point (fulcrum) when a force is applied to it. The applied force, or effort, is used to move the load. A load is the amount of resistance being moved. In first-class levers, the effort is applied at one end of the lever and the load is at the other, with the fulcrum somewhere between. An example would be a seesaw or pair of scissors. In a second-class lever, the effort is applied at on end of the lever and the fulcrum is located at the other, with the load between them. An example would be a wheelbarrow. This type of lever is a lever of strength but range of motion and speed are sacrificed for that strength. In third-class levers, the effort is applied between the load and the fulcrum. These levers operate at great speed. Tweezers and forceps provide this type of leverage. In conclusion, differences in the positioning of the three elements modify muscle activity with respect to (1) speed of contraction, (2) range of movement, and (3) the weight of the load that can be lifted. In lever systems that opperate at a mechanical disadvantage (speed levers), force is lost but speed and range of movement are gained, and this can be a ditinct benefit. Systems that operate at a mechanical advantage (power levers) are slower, more stable, and used where strength is a priority.

Prime mover

A muscle that provides the major force fir producing a specific movement is a _____, or agonist "leader" of that movement.

Lower Leg Muscles

Fibularis longus extensor digitorum longus tibialis anterior gastronemius soleus calcaneal (achilles tendon)

Pelvis/Thigh/Hip Muscles

Illopsoas pectineus gluteus medius gluteus maximus

Antagonist

Muscles that oppose or reverse, a particular movement are called _____. Located opposite of the prime mover.

Thorax Muscles

Pectoralis minor pectoralis major serratus anterior intercostals

Synergist

Performs or helps perform, the same set of joint motion as the agonists. These act on movable joints.

Four functional muscle groups

Prime movers, antagonists, synergists, and fixators.

Arrangement of Fascicles by name and by purpose.

The most common patterns of fascicle arrangement are parallel, pennate, convergent, and circular. The fascicle pattern is circular when the fascicles are arranged in concentric rings. Muscles with this arrangement surround external body openings, which that close by contracting. Circular patterns are called sphincters (squeezers). A convergent muscle has a broad origin, and its fascicles converge toward a single tendon of insertion. Such a muscle is triangular or fan shaped like the pectoralis major muscle of the anterior thorax. In a parallel arrangement, the long axes of the fascicles run parallel to the long axis of the muscle. Such muscles are either strap-like or spindle shaped with an expanded belly like the biceps brachii muscle of the arm. However sometimes spindle shaped muscles are referred to as fusiform muscles. In a pennate pattern, the fascicles are short and they attach to a central tendon that runs the length of the muscle. This creates a feather shaped appearance. Unipennate looks like half a feather, Bipennate looks like a normal feather, and Multipennate looks like a bunch of feathers grouped together and connecting at one point.

Upper Arm Muscles

Triceps brachii biceps brachii brachialis

Fixator

When synergists immobilize a bone, or a muscle's origin, they are more specifically called _____.