4 Anatomy Lecture_Muscles PDF

Faculty of Medicine Medical Education- Damietta University Level 1 Semester 1 PAH 101 Muscle Dr. Gamal Elsayed  Contact: Anatomy Department. Official email: [email protected] Instructor Mobile (optional): 01014935906...

Faculty of Medicine Medical Education- Damietta University Level 1 Semester 1 PAH 101 Muscle Dr. Gamal Elsayed  Contact: Anatomy Department. Official email: [email protected] Instructor Mobile (optional): 01014935906 Academic hours: information sunday: wednsday:  Types of muscles. Skeletal muscles: General features. Functions. Lecture Action. topics Arrangement of fascicles. Naming skeletal muscles. Structures associated with muscles. Types of fascia  By the end of the lecture, the students will be able to: 1- Skeletal muscle 2- Internal structure of skeletal muscle 3- Actions of skeletal muscle Learning 4- Nerve supply of skeletal muscle Outcomes 5- Identify smooth muscle 6- Identify cardiac muscle  A 22-year-old man presented to his family physician with a laceration of the fibrous Case sheets or bands that cover his body under the skin and invest the muscles. scenario, Which of the following structures would Clinical most likely be injured? Correlate, Tendon Fascia Practice Synovial tendon sheath Aponeurosis points Ligament  Muscle The three types of muscle are: Skeletal. Smooth. Cardiac.  Skeletal Muscle Skeletal muscles produce the movements of the skeleton; they are sometimes called voluntary muscles and are made up of striped muscle fibers. A skeletal muscle has two or more attachments: 1. The attachment that moves the least is referred to as the origin. 2. The one that moves the most, the insertion.  The fleshy part of the muscle is referred to as its belly. The ends of a muscle are attached to bones, cartilage, or ligaments by cords of fibrous tissue called tendons. Flattened muscles are attached by a thin but strong sheet of fibrous tissue called an aponeurosis. A raphe is an interdigitation of the tendinous ends of fibers of flat muscles. Internal Structure The muscle fibers are bound together with delicate of Skeletal Muscle areolar tissue, which is condensed on the surface to form a fibrous envelope, the epimysium.  The individual fibers of a muscle are arranged either parallel or oblique to the long axis of the muscle. The muscles whose fibers run parallel to the line of pull will bring a greater degree of movement compared with those whose fibers run obliquely.  Examples of muscles with parallel fiber arrangements are: The sternocleidomastoid, the rectus abdominis, and the sartorius.  Muscles whose fibers run obliquely to the line of pull are pennate muscles (they resemble a feather). A unipennate muscle is one in which the tendon lies along one side of the muscle, and the muscle fibers pass obliquely to it (e.g., extensor digitorum longus).  A bipennate muscle is one in which the tendon lies in the center of the muscle and the muscle fibers pass to it from two sides (e.g., rectus femoris).  A multipennate muscle: - It may be arranged as a series of bipennate muscles lying alongside one another (e.g., acromial fibers of the deltoid) - It may have the tendon lying within its center and the muscle fibers passing to it from all sides, converging as they go (e.g., tibialis anterior). Pennate muscles have many more fibers compared to muscles with parallel fiber arrangements and are therefore more powerful. Skeletal Muscle Action A muscle may work in the following four ways: Prime mover: A muscle is a prime mover when it is the chief muscle or member of a chief group of muscles responsible for a particular movement. For example, the quadriceps femoris is a prime mover in the movement of extending the knee joint.  Antagonist Any muscle that opposes the action of the prime mover is an antagonist. For example, the biceps femoris opposes the action of the quadriceps femoris when the knee joint is extended. Before a prime mover can contract, the antagonist muscle must be equally relaxed; this is brought about by nervous reflex inhibition.  Fixator A fixator contracts isometrically (i.e., contraction increases the tone but does not in itself produce movement) to stabilize the origin of the prime mover so that it can act efficiently. For example, the muscles attaching the shoulder girdle to the trunk contract as fixators to allow the deltoid to act on the shoulder joint.  Synergist The prime mover muscle crosses several joints before it reaches the joint at which its main action takes place. To prevent unwanted movements in an intermediate joint, groups of muscles called synergists contract and stabilize the intermediate joints. For example, the flexor and extensor muscles of the carpus contract to fix the wrist joint, and this allows the long flexor and extensor muscles of the fingers to work efficiently.  Many muscles can act as a prime mover, an antagonist, a fixator, or a synergist, depending on the movement to be accomplished. Muscles can even contract paradoxically, for example, when the biceps brachii, a flexor of the elbow joint, contracts and controls the rate of extension of the elbow when the triceps brachii contracts.  Nerve Supply of Skeletal Muscle The nerve trunk to a muscle is a mixed nerve: 1. About 60% is motor. 2. 40% is sensory. 3. It contains some sympathetic autonomic fibers. The nerve enters the muscle at about the midpoint on its deep surface, the place of entrance is known as the motor point. This arrangement allows the muscle to move with minimum interference with the nerve trunk.  Naming of Skeletal Muscles Individual muscles are named according to their shape, size, number of heads or bellies, position, depth, attachments, or actions.  Smooth Muscle Smooth muscle consists of long, spindle-shaped cells closely arranged in bundles or sheets. In the tubes of the body, it provides the power for propelling the contents through the lumen. In the digestive system it also causes the ingested food to be thoroughly mixed with the digestive juices.  A wave of contraction of the circularly arranged fibers passes along the tube, milking the contents onward. By their contraction, the longitudinal fibers pull the wall of the tube proximally over the contents. This method of propulsion is referred to as peristalsis.  In storage organs such as the urinary bladder and the uterus, the fibers are irregularly arranged and interlaced with one another. Their contraction is slow and sustained and brings about expulsion of the contents of the organs.  In the walls of the blood vessels the smooth muscle fibers are arranged circularly and serve to modify the caliber of the lumen. Depending on the organ, smooth muscle fibers may be made to contract by: 1. local stretching of the fibers, 2. Nerve impulses from autonomic nerves, 3. Hormonal stimulation.  Cardiac Muscle Cardiac muscle consists of striated muscle fibers that branch and unite with each other. It forms the myocardium of the heart. Its fibers tend to be arranged in whorls and spirals, and they have the property of spontaneous and rhythmic contraction.  Specialized cardiac muscle fibers form the conducting system of the heart. Cardiac muscle is supplied by autonomic nerve fibers that terminate in the nodes of the conducting system and in the myocardium.  A 22-year-old man presented to his family physician with a laceration of the fibrous sheets or bands that cover his body under the skin and invest the muscles. Which of the following structures would Case most likely be injured? Discussion/reflection Tendon Fascia Synovial tendon sheath Aponeurosis Ligament  1- The attachment of the skeletal muscle are in the form of : - Tendon. - Aponeurosis. - Raphe. - Belly. Questions 2- The arrangement of the fibbers of skeletal muscle are : - Parallel - Pennate - Circular - Fusiform. 3- Example of muscle with parallel fibers is: - Sartorius - Rectus femoris - Tibialis anterior - Deltoid. 4- The types of actions of skeletal muscles are : - Prime mover - Antagonist - Fixator - peristalsis  Independent learning from the Internet https://www.youtube.com/watch?v =w6k5tzFbfa4 References https://www.youtube.com/watch?v =RYs6Ja4XHjI