Muscles PDF - General Human Anatomy

Muscles Muscle cells (muscle fibers) are specialized contractile cells. They are organized into tissues that move body parts or temporarily alter the shape of internal organs. Associated connective tissue conveys nerve fibers and capillaries to the muscle cells as it binds them into bundles or fasc...

Muscles Muscle cells (muscle fibers) are specialized contractile cells. They are organized into tissues that move body parts or temporarily alter the shape of internal organs. Associated connective tissue conveys nerve fibers and capillaries to the muscle cells as it binds them into bundles or fascicles. Three types of muscle are described based on distinct characteristics relating to * whether it is normally willfully controlled (voluntary or involuntary). * Whether it appears striped or unstriped when viewed under a microscope (striated or smooth). * whether it is located in the body wall and limbs (somatic) or makes up the hollow organs (viscera, e.g., the heart) of the body cavities or blood vessels (somatic or visceral). The three types of muscle are skeletal, smooth, and cardiac. I - Skeletal muscle It is a striated voluntary somatic muscle that makes up the gross skeletal muscles that compose the muscular system, moving or stabilizing bones and other structures. A skeletal muscle has two or more attachments. The more proximal, less mobile attachment is referred to as the origin. The more distal, more mobile attachment is the insertion. When a muscle contracts, the insertion is drawn proximally toward the origin. However, under varying circumstances, the degree of mobility of the attachments may be reversed (or interchanged).  GENERAL HUMAN ANATOMY 21 is Formed of The fleshy part of the muscle is referred to 093/ proximal: asoits belly. The ends of a muscle are & 9520mnon- attached to supporting elements (bones,F l e s h y Flesh non-Fleshy cartilage, ligaments, or other muscles) by Origin cords of fibrous tissue called tendons. Some the belly FIxes 6169 less mobile tendons (e.g., those belonging to the flat, Belly Fleshy wide abdominal oblique muscles) form a thin, strong sheet termed an aponeurosis. Gastrocnemius Other tendons may form a raphe, which is an interdigitation of the tendinous ends of ? Insertion distal fibers of flat muscles. more mobile each Muscle attached to the ins origin, insertion, and belly lessofFixes the (a l3) bhe sheum ant to obia guo gastrocnemius muscle. sterinagiru bones from origin and insertion -? 911190 3l noongt9 0 nore 20129 nsgid San, CircularJIVA Convergent 13211 16 79 e V E n eilsi 26 8 2 9 0 1 Multipennate 1221 3 2 0 n Fusiform vorn HA 69 2309 11110s 29076 common tendon for the insertion External oblique aponeurosis of the gastrocnemius and soleus muscies Parallel 1086 911J 1J36 292009 it ol 721n09639 12 01 2.13 Bipennate IN 10 V 1919ny? C Unipennate Raphe of mylohyoid muscles DeNI Examples of (A)a tendon, (B)an aponeurosis, The architecture and shape of a skeletal muscle depend on the arrangement of its fibers. and (C) a raphe, en b160m Sit 21101 11 19110 1369 Cliw stinu-bn6 ? origin ans insertion are exchanging alge bris chodw ni. big 16115 pribi6a basilbiasa? noitostinos sirntyni  22 Dr/ Abeer Madkour Mahmoud 20 Forms of the skeletal muscles: According to the arrangement of muscles 1- Parallel form: the muscle fibers run parallel to the axis of force Beng thisincludes a-Fus includessariethat varietieshas a wide center and tapered enis see biceps bras b-strap: long, at muscle fibers are parall from orien to insertion le sana c- Convergent (triangular or fan-shaped): muscle fibers are ? fanned out broachy. origin and converge at its insertion (e.g. pectoralis major). d- Circular muscle: in which the fibers are longitudinally arranged1, but create a from origin to insertion (e.g. the orbicularis ocull). 2- Pennate form: in which the muscle has a feathered appearance wine. muscle fibers run obliquely to the line of pull. Varieties are; a - Unipennates the tendon lies along one side of the muscle, and the muste pass obliquely to it (e.g., extensor digitorum longus), b- Bipennatel the tendon lies in the center of the muscle, and the muscle files, ? to it from two sides (e.g., rectus femoris). c- ?Multipennate: It is as a series of bipennate muscles lying alongside one ans (e.g., the deltoid). d--Circumpennate: Muscles have the tendon lying within its center and the ms fibers passing to it from all sides, converging as they go (e.g., tibialis anterior) Skeletal Muscle Action X All movements are the result of the coordinated action of many muscles. Mus contraction that produces movements can act in several ways: 1- Agonist (prime mover): A muscle is an agonist (prime mover) when it is the chi muscle or member of a chief group of muscles responsible for producing particular movement. 2- Antagonist: It the muscle that opposes the action of the agonist muscle. 3- Fixator: A fixator muscle contracts to stabilize the origin of the prime moverso that it can act efficiently. 4- Synergist: It may directly or indirectly assist a prime mover during movement. Il-Cardiac muscle Cardiac muscle consists of involuntary partially striated muscle fiber that bras. and unite with each other. It forms the myocardium of the heart. Its fibers tend to? arranged in whoris and spirals, and they have the property of spontaneous. rhythmic contraction. Specialized cardiac muscle fibers form the conducting ste  GENERAL HUMAN ANATOMY 2 3 of the heart. Cardiac muscle is supplied by autonomic nerve fibers that terminate in the nodes of the conducting system and in the myocardium. III-Smooth Muscle Smooth muscle is a non-striated involuntary visceral muscle consists of long, spindle-shaped cells closely arranged in bundles or sheets. It is present in; ? In the tubes of the body (as the ureters), it provides the motive power for propelling the contents through the lumen. ? In the digestive system, it mixes ingested food with digestive juices and propels the contents by the peristaltic contractions. ? In storage organs such as the urinary bladder and the uterus. ? In the walls of the blood vessels.