1 THE MUSCULAR SYSTEM Chapter 11 Anatomy and Physiology Lecture
THE MUSCULAR SYSTEM 2 Muscle Tissue - refers to all the contractile tissues of the body; skeletal, cardiac, and smooth muscle. Muscular System - refers to the skeletal muscle system: the skeletal muscle tissue and connective tissues that make up individual muscle organs, such as the biceps brachii muscle. GENERAL PRINCIPLES This chapter is devoted to the description of the major named skeletal muscles. Tendons Attach muscle to bones and other connective tissues. Aponeurosis A very broad tendon. Origin (head) Is normally the of the muscle attached to the more stationary of the two bones. Insertion Is the end of the muscle attached to the bone undergoing the greater movement. Belly Is the largest portion of the muscle, between the origin and the insertion. Agonist Is a muscle causing an action when it contracts. Antagonist Is a muscle working in opposition to the agonist, moving a structure in the opposite direction. Synergists - Are muscles that work together to cause a movement. Prime mover Is a muscle, among a group of synergists, that plays the major role in accomplishing the desired movement.
Muscle Shapes 3 Four groups Muscular shapes are: 1. Pennate When muscular fasciculi are arranged like the bards of a feather along a common tendon. (a) Unipennate A muscle with fasciculi on one side of the tendon. (b) Bipennate A muscle with fasciculi on both sides of the tendon. (c) Multipennate A muscle with fasciculi arranged at many places around the central tendon. 2. Parallel When the muscular fasciculi are organized parallel to the long axis of the muscle. 3. Convergent When the base is much wider than the insertion, giving the muscle a triangular shape and allowing it to contract with more force than could occur in a parallel muscle. Example: Deltoid muscle. 4. Circular When they have their fasciculi arranged in a circle around an opening and act as sphincters to close the opening. Example: Orbicularies oris. Nomenclature About 700 skeletal muscles. Characteristic used to name the muscles: 1. Location - Named according to their location Temporalis - is near the temporal bone. Tibialis Anterior - is near the front of the tibia. Pectoralis located at the chest Gluteus located at the buttock
2. Size May refer to the relative size of the muscle. Maximus - mean large Minimus - smallest Longus - long Brevis - short 4 3. Shape Named according to their shape Deltoid - triangular Trapezius - trapezoid Serratus anterior - saw-toothed Rhomboideus major - rhomboid or diamond shaped 4. Orientation According to their fascicular orientation Rectus (straight) - 5. Origin and insertion Sternocleidomastoid - originate on the sternum and clavicle and inserts at the mastoid process of the temporal bone. 6. Number of heads A biceps muscle has two heads, while triceps has three heads. 7. Function Abductor moves a structure away from midline, while a adductor moves structure toward midline. MOVEMENTS ACCOMPLISHED BY MUSCLES When muscles contract: 1. The Pull (P), or force, of muscle contraction is applied to levers, such as bones, resulting in movement of livers; 2. A Lever is a rigid shaft capable of turning about a pivot point called a Fulcrum (F) and transferring a force applied at one point along the lever to a Weight (W), or resistance, placed at some other point along the lever.
5 Note: The joints function as fulcrums The bones function as levers The muscles provide pull to move the levers. Three classes of lever exist based on the relative position of the lever, weight, fulcrum, and forces. Class I Lever Class I Lever System: The fulcrum is located between the force and the weight. W 9 P ϖ F Example is the head resting on the vertebral column. Class II Lever Class II Lever System The weight is located between the fulcrum and the pull. ϖ F W 8 P Example is raising the body on the toes.
Class III Lever 6 Class III Lever System The Pull is located between the fulcrum and the weight. ϖ F 8 P W Example is a person using a shovel. Leverage - the mechanical advantage gained by a lever, is largely responsible for a muscle's strength and range of movement. Muscle Anatomy An over view of the Superficial muscles; (a) (b) Anterior View Posterior View Be able to identify the structure (muscular) based on the figures shown. HEAD MUSCLES Head and Neck muscles: Muscles Moving the Head Facial Expression: Muscles of Facial Expression
Mastication: 7 Muscles of Mastication Swallowing and the Larynx: Muscles of Swallowing and the Larynx The hyoid muscles are divided into a Suprahyoid group superior to the hyoid bone and an Infrahyoid group inferior to it. The Soft palate, pharynx, and larynx contain several muscles involved in swallowing and speech. Swallowing is accomplished by elevation of the pharynx, which in turn is accomplished by elevation of the larynx. Snoring is a rough, raspy noise that can occur when a sleeping person inhales through the mouth and nose. The noise usually is made by vibration of the soft palate but also may occur as a result of vocal cord. Movements of the Eyeball The eyeball rotates within the orbit to allow vision in a range of direction. The movements of each eye are accomplished by six muscles named for the orientation of their fasciculi relative to the spherical eye. Muscles Moving the Eye Thoracic Muscles Diaphragm causes the major movement produced during quiet breathing. Muscles of the Thorax
Pelvic Floor and Perineum 8 Muscles of the Pelvic Floor and Perineum Ankle, Foot, and Toe Movements Muscles of the Leg Acting on the Leg, Ankle, and Foot