Muscular System Notes PDF

MUSCULAR SYSTEM SMOOTH MUSCLE Located in the walls of hollow internal OVERVIEW structures, such as blood vessels, The scientific study of muscles is known airways, and...

MUSCULAR SYSTEM SMOOTH MUSCLE Located in the walls of hollow internal OVERVIEW structures, such as blood vessels, The scientific study of muscles is known airways, and most organs in the as myology (myo - = muscle; -logy = abdominopelvic cavity. It is also found study of) in the skin, attached to hair follicles. Muscular tissue contributes to Under a microscope, this tissue lacks homeostasis by producing body the striations of skeletal and cardiac movements, moving substances muscle tissue. For this reason, it looks through the body, and producing heat to nonstriated, which is why it is referred to maintain normal body temperature. as smooth. (other 2 muscle tissues are striated) TYPES OF MUSCULAR TISSUE Usually involuntary, the muscles that propel food through your digestive SKELETAL MUSCLE canal, has autorhythmicity. most skeletal muscles move the bones *PERISTALSIS of the skeleton works mainly in a voluntary manner. FUNCTIONS OF MUSCULAR TISSUE Its activity can be consciously controlled by neurons (nerve cells) that 1. Producing body movements - rely on the are part of the somatic (voluntary) integrated functioning of skeletal muscles, division of the nervous system. bones, and joints. Most skeletal muscles also are 2. Stabilizing body positions - muscle controlled subconsciously to some contractions stabilize joints and help maintain extent. body positions, such as standing or sitting. o Diaphragm continues to Postural muscles contract continuously when alternately contract and relax you are awake. without conscious control so 3. Storing and moving substances within the that you don’t stop breathing. body - Storage is accomplished by sustained o Also, you do not need to contractions of ring-like bands of smooth consciously think about muscle called sphincters contracting the skeletal muscles 4. Generating heat - As muscular tissue that maintain your posture or contracts, it produces heat, a process known stabilize body positions. as thermogenesis. Involuntary contractions of skeletal muscles, known as shivering, can CARDIAC MUSCLE increase the rate of heat production. Only found in the heart, which forms the wall. Alternating contraction and relaxation of 3 LAYERS OF CONNECTIVE TISSUE the heart are not consciously controlled. Rather, the heart beats - extend from the fascia to protect and because it has a natural pacemaker strengthen skeletal muscle that initiates each contraction – 1. Epimysium (epi- = upon) - is the outer layer, AUTORHYMICITY, *heart rate encircling the entire muscle. It consists of dense irregular connective tissue. 2. Perimysium (peri- = around) is also a layer of dense irregular connective tissue, but it surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called muscle fascicles/muscle fasciculi. Many muscle fascicles are large enough to be seen with the naked eye. They give a cut of meat its characteristic “grain”; if you tear a piece of meat, it rips apart along the muscle fascicles. 3. Endomysium (endo- = within) - is mostly reticular fibers, that penetrates the interior of each muscle fascicle and separates individual muscle fibers from one another. The epimysium, perimysium, and endomysium are all continuous with the connective tissue that attaches skeletal muscle to other structures, such as bone or another muscle. For example, all three connective tissue layers may extend beyond the muscle fibers to form a rope like tendon that attaches a muscle to the periosteum of a bone. o An example is the calcaneal (Achilles) tendon When the connective tissue elements extend as a broad, flat sheet, it is called an aponeurosis o An example is the epicranial aponeurosis on top of the skull SKELETAL MUSCLES between the frontal and occipital bellies of the occipitofrontalis ORIGIN - the attachment of a muscle’s tendon muscle to the stationary bone INSERTION - the attachment of the muscle’s other tendon to the movable bone ✓ A useful rule of thumb is that the origin is usually proximal and the insertion distal; the insertion is usually pulled toward the origin. BELLY/BODY - the fleshy portion of the muscle between the tendons. ✓ Certain muscles are also capable of reverse muscle action (RMA). This  means that during specific movements SYNERGISTS - contract and stabilize the of the body the actions are reversed; intermediate joints to prevent unwanted therefore, the positions of the origin and movements at intermediate joints or to insertion of a specific muscle are otherwise aid the movement of the prime switched. mover. COORDINATION AMONG MUSCLES FIXATORS - stabilizing the origin of the prime Movements often are the result of mover so that the prime mover can act more several skeletal muscles acting as a efficiently. Fixators steady the proximal end of a group. limb while movements occur at the distal end. Most skeletal muscles are arranged in Ex: scapula (holds by pecs, traps, SA) opposing (antagonistic) pairs at joints— during arm abduction by deltoids that is, flexors– extensors, abductors– adductors, and so on. ✓ Compartment is a group of skeletal Within opposing pairs, one muscle, muscles, their associated blood called the prime mover or agonist (= vessels, and associated nerves, all of leader), contracts to cause an action which have a common function. while the other muscle, (ex. Flexor compartment) the antagonist (anti- = against), stretches and yields to the effects of the prime mover. MUSCLES OF THE ABDOMEN THAT PROTECT o In the process of flexing the ABDOMINAL VISCERA AND MOVE THE forearm at the elbow, for VERTEBRAL COLUMN instance, the biceps brachii is the prime mover, and the triceps Anterolateral abdominal wall is composed of brachii is the antagonist skin, fascia, and four pairs of muscles: the external oblique, internal oblique, transversus abdominis, and rectus abdominis External abdominal oblique – superficial, its muscle fascicles extend inferiorly and medially. Internal abdominal oblique - intermediate flat muscle. Its fascicles extend at right angles to those of the external abdominal oblique. Transversus abdominis - deep muscle, with most of its muscle fascicles directed transversely around the abdominal wall. Rectus abdominis - is a long muscle that extends the entire length of the anterior abdominal wall  Intercostal muscle – other muscle for breathing located in between intercostal spaces. o External intercostals - occupy the superficial layer, and their fibers run in an oblique direction interiorly and anteriorly from the rib above to the rib below. They elevate the ribs during inhalation to help expand the thoracic cavity. o Internal intercostals - occupy the intermediate layer The fibers of these muscles run at right angles to the external intercostals, in an oblique direction interiorly and posteriorly from the inferior border of the rib above to the superior border of the rib below. They draw adjacent ribs together during forced exhalation to help decrease the size of the thoracic cavity. MUSCLES OF THE THORAX THAT ASSIST IN BREATHING ✓Note: A mnemonic for the action of the intercostal muscles is singing “Old MacDonald Diaphragm - is a dome-shaped and had a farm, E, I, E, I, O” = External Intercostals most important muscle that powers Elevate during Inhalation, Oh!” breathing. Central tendon - a strong aponeurosis located near the center  the anus and keeps the anal canal and anus closed except during defecation MUSCLES OF THE PELVIC FLOOR THAT SUPPORT THE PELVIC VISCERA AND MUSCLES OF THE GLUTEAL REGIONS THAT FUNCTION AS SPHINCTERS MOVE THE FEMUR Levator ani and Ischiococcygeus - Muscles of the lower limbs are larger muscles of the pelvic floor aka pelvic and more powerful than those of the diaphragm along with fascia covering upper limbs because of differences in the internal and external surface function. 3 components of the levator ani muscle While upper limb muscles are are the pubococcygeus, puborectalis, characterized by versatility of and iliococcygeus movement, lower limb muscles function Levator ani in stability, locomotion, and o largest and most important maintenance of posture. muscle of the pelvic floor. In addition, muscles of the lower limbs o supports the pelvic viscera and often cross two joints and act equally resists the inferior thrust that on both. accompanies increases in intra- o The majority of muscles that abdominal pressure during move the femur (thigh bone) functions such as forced originate on the pelvic girdle and exhalation, coughing, vomiting, insert on the femur urination, and defecation. Ischiococcygeus o pulls the coccyx anteriorly after it has been pushed posteriorly during defecation or childbirth. MUSCLES OF THE PERINEUM Perineum - is a diamond-shaped area in the region of the trunk inferior to the pelvic diaphragm External anal sphincter closely adheres to the skin around the margin of MUSCLES OF THE THIGH THAT MOVE THE FEMUR, TIBIA, AND FIBULA MUSCLES OF THE LEG THAT MOVE THE FOOT AND TOES Deep fascia (intermuscular septum) separates the muscles of the thigh that act on the femur (thigh bone) and tibia and fibula (leg bones) into medial, anterior, and posterior compartments  ▪ EPICRANIAL APONEUROSIS/GALEA APONEUROTICA – holds the 2 muscular portion that covers the superior and lateral surfaces of the skull FACIAL MUSCLES MUSCLES OF THE HEAD THAT PRODUCE FACIAL EXPRESSIONS MUSCLES OF THE HEAD THAT MOVE THE EYEBALLS AND UPPER EYELIDS OCCIPITOFRONTALIS o FRONTALIS – anterior belly, Extraocular (extrinsic eye) muscles - superficial to the frontal bone muscles that move the eyeballs that o OCCIPITALIS – posterior belly, originate outside the eyeballs (in the superficial to the occipital bone  orbit) and insert on the outer surface of ex: when the patient is asked to look up and the sclera (“white of the eye”) inward it is testing your inferior oblique o The extraocular muscles are some of the fastest contracting and most precisely controlled skeletal muscles in the body 3 pairs of extraocular muscles 1. Superior and inferior recti – moves eye up and down 2. Lateral and medial recti – moves eye side to side 3. Superior obliques (moves the eyeballs inferiorly and laterally) and inferior obliques (moves the eyeballs superiorly and laterally) MUSCLES THAT MOVE THE MANDIBLE AND Levator palpebrae superioris does not ASSIST IN MASTICATION AND SPEECH move the eyeballs, it raises the upper eyelids, that is, opens the eyes. The muscles that move the mandible o It is therefore an antagonist to (lower jawbone) at the the orbicularis oculi, which temporomandibular joint (TMJ) are closes the eyes. known as the muscles of mastication (chewing) o Of the four pairs of muscles involved in mastication, three are powerful closers of the jaw and account for the strength of the bite: masseter, temporalis, and medial pterygoid. Masseter is the strongest muscle of mastication. Medial and lateral pterygoid muscles assist in mastication by moving the mandible from side to side to help grind CARDIAC POSITIONS OF GAZE (RIGHT EYE) food. o Additionally, the lateral pterygoid muscles protract (protrude) the mandible. ✓ Note: A mnemonic for muscles of mastication is Teeny Mice Make Petite Little Prints = Temporalis, Masseter, Medial Pterygoid, and Lateral Pterygoid. The muscle tested is where they are asked to move their eye:  The extrinsic and intrinsic muscles of the tongue insert into both lateral halves of the tongue Extrinsic muscles of the tongue: Genioglossus (origin: the mandible) pulls the tongue downward and forward Styloglossus (origin: the styloid process) pulls the tongue upward and backward Hyoglossus (origin: the hyoid bone) pulls the tongue downward and flattens it Palatoglossus (origin: the soft palate) raises the back portion of the tongue MUSCLES OF THE HEAD THAT MOVE THE TONGUE AND ASSIST IN MASTICATION AND SPEECH Tongue is a highly mobile structure that is vital to digestive functions such as mastication (chewing), detection of taste, and deglutition (swallowing). It is also important in speech. o The tongue’s mobility is greatly aided by its attachment to the mandible, styloid process of the temporal bone, and hyoid bone. Extrinsic tongue muscles - originate MUSCLES OF THE ANTERIOR NECK THAT outside the tongue and attach to it ASSIST IN DEGLUTITION AND SPEECH o They move the entire tongue in Two groups of muscles are associated various directions, such as with the anterior aspect of the neck: anteriorly, posteriorly, and (1) the suprahyoid muscles - elevates laterally. the hyoid bone, floor of the oral cavity, Intrinsic tongue muscles - originate and tongue during deglutition and insert within the tongue. (swallowing). o These muscles alter the shape of (2) the infrahyoid muscles - depress the tongue rather than moving the hyoid bone and some move the the entire tongue. larynx during swallowing and speech. o Both groups of muscles stabilize the hyoid bone, allowing it to  serve as a firm base on which the MUSCLES OF THE THORAX THAT MOVE THE tongue can move. PECTORAL GIRDLE Anterior and Posterior Digastric - The main action of the muscles that united by an intermediate tendon that move the pectoral (shoulder) girdle is held in position on the hyoid bone by a (clavicle and scapula) is to stabilize the fibrous loop. scapula so it can function as a stable o elevates the hyoid bone and base for most of the muscles that move larynx (voice box) during the humerus. Because scapular swallowing and speech. movements usually accompany o When the hyoid is stabilized, the humeral movements in the same digastric depresses the mandible direction, the muscles also move the and is therefore synergistic to the scapula to increase the range of motion lateral pterygoid in the opening of of the humerus. the mouth. For example, it would not be possible to Stylohyoid muscle - elevates and raise the arm above the head if the draws the hyoid bone posteriorly, thus scapula did not move with the humerus. elongating the floor of the oral cavity During abduction of the humerus, the during swallowing scapula follows the humerus by rotating Mylohyoid muscle - elevates the hyoid upward. bone and helps press the tongue ** SCAPULOHUMERAL RHYTHM\ against the roof of the oral cavity during swallowing to move food from the oral cavity into the throat. Geniohyoid muscle - elevates and draws the hyoid bone anteriorly to shorten the floor of the oral cavity and to widen the throat to receive food that is being swallowed. It also depresses the mandible Inferior and superior Omohyoid muscle ✓ omohyoid, sternohyoid, and thyrohyoid muscles depress the hyoid MUSCLES OF THE ARM THAT MOVE THE bone. RADIUS AND ULNA Sternothyroid muscle - depresses the Most of the muscles that move the thyroid cartilage (Adam’s apple) of the radius and ulna (forearm bones) cause larynx to produce low sounds flexion and extension at the elbow, Thyrohyoid muscle - elevates the which is a hinge joint. thyroid cartilage to produce high The biceps brachii, brachialis, and sounds. brachioradialis muscles are the flexor muscles. The extensor muscles are the triceps brachii and the anconeus  Posterior (extensor) compartment muscles of the forearm originate on the humerus, insert on the metacarpals and phalanges, and function as extensors. At the wrist, the deep fascia is thickened into fibrous bands called retinacula (retinacul = holdfast). MUSCLES OF THE FOREARM THAT MOVE THE WRIST, HAND, THUMB, AND DIGITS Those in this group that act on the digits are known as extrinsic muscles of the hand (ex- = outside) because they originate outside the hand and insert within it. They produce a powerful but crude movements of the digits Anterior (flexor) compartment muscles of the forearm originate on the humerus; typically insert on the carpals, metacarpals, and phalanges; and function primarily as flexors MUSCLES OF THE PALM THAT MOVE THE DIGITS—INTRINSIC MUSCLES OF THE HAND Intrinsic muscles of the hand in the palm produce the weak but intricate and precise movements of the digits that characterize the human hand Thenar eminence – bulk side of anterior lateral palm area Hypothenar – bulk side of the medial anterior aspect of the palm Intermediate – mid palm area