Lecture 2 Dr. Amal Elkattan - Principle Muscular System 2020 PDF

The muscular system is concerned with the production of movement both of the body as a whole and of the internal organs. There are three types of muscles in the human body. Each is concerned with a different type of movement. Types of Muscles 1- Skeletal muscles 2- Smooth (visceral muscles) 3- Cardi...

The muscular system is concerned with the production of movement both of the body as a whole and of the internal organs. There are three types of muscles in the human body. Each is concerned with a different type of movement. Types of Muscles 1- Skeletal muscles 2- Smooth (visceral muscles) 3- Cardiac muscles Skeletal muscle Skeletal muscles are attached to their origins and insertions by white fibrous tissue forming rounded tendons or flattened aponeurosis The fleshy part of the muscle is called belly. Skeletal muscle The end of the muscle which remains fixed during contraction is the origin while the end which moves is the insertion. Under varying circumstances the degree of mobility of the attachments may be reversed; therefore, the terms origin and insertion are interchangeable The fleshy part of the muscle is called belly It is controlled by the voluntary part of the nervous system. - Parts of skeletal muscle Each skeletal muscle is formed of three parts: Origin: it is the proximal part Insertion: it is the distal movable part Belly: it is the intermediate fleshy part Visceral (smooth) muscle Visceral muscles are found in the walls of the visceral organs and blood vessels. It is controlled by the involuntary part of the nervous system. In the tubes of the body as digestive tract, it provides the motive power for propelling the contents through the lumen (peristalsis).. Visceral (smooth) muscle In storage organs such as the urinary bladder and the uterus, the 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 serves to modify the caliber of the lumen Cardiac muscle It is only found in the heart (myocardium). It is controlled by the autonomic nervous system. Specialized cardiac muscle fibers form the conducting system of the heart. Skeletal Muscles Form of muscles: There is a wide variation in the size, shape and form of attachment of muscles. Each is well adapted to meet the requirements at the articulations over which it passes It forms the main bulk of the body (about 40% of the body weight).The total number is 620 muscles. SKELETAL MUSCLES Muscles may be grouped according to the direction of their fibres which may be parallel, oblique or spiral. Forms of Skeletal muscles A- Muscles with fibers parallel to the line of pull: -they are strap like -they give wide range of movements -Examples: Sartorius, rectus abdominis Sartorius Rectus abdominis B- Muscles with fibers oblique to line of pull: 1- Triangular (fan like) : e.g. Temporalis Pennate muscles (feather-like) 1-Unipennate muscles 2-Bipennate muscles 3-Multipennate muscles 2- Pennate Muscles (feather- like) a- Unipennate muscles: -Tendon is along one margin of muscle - Fibers slope into one side of tendon like half a feather - Example: flexor pollicis longus Flexor pollicis longs b- Bipennate Muscles: Tendon is in the center - Fibers slope into two sides of tendon like a feather - Example: Rectus femoris - Multipennate muscles: FLATE MUSCLE CIRCUMPENNATE SPIRAL MUSCLE cMultipennate muscles: 1- Flat type which is a series of bipennate muscles alongside one another. E.g. middle fibers of deltoid Flat type 2- Circumpennate type in which muscle fibers converge from all sides into central tendon. E.g. tibialis anterior C- Spiral Muscles: -There is a twist between two groups of muscle fibers - Example: pectoralis major Differants shapes of skeletal muscle Types of muscle action: All movements are the result of the coordinated action of many muscles. However, to understand a muscle's action it is necessary to study it individually. A muscle may work in the following four ways 1-Prime movers: 2-Antagonists: 3-Fixators: 4-Synergic muscles: 1-Prime movers: - 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. Quadriceps femoris extending the knee as a prime mover, and biceps femoris acting as an antagonist 2-Antagonists: 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 Biceps femoris flexing the knee as a prime mover, and quadriceps acting as an antagonist 3-Fixators: 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 Muscles around shoulder girdle fixing the scapula so that movement of abduction can take place at the shoulder joint 4-Synergic muscles: In many locations in the body 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 carpal bones contract to fix the wrist joint, and this allows the long flexor and extensor muscles of the fingers to work efficiently. : Flexor and extensor muscles of the carpal bones act as synergists and stabilize the carpals so that long flexor and extensor tendons can flex and extend the fingers. Nerve supply of muscles: The nerve trunk to a muscle is a mixed nerve. About 60% is motor and 40% is sensory, and it also contains some sympathetic autonomic fibers. The nerve enters the muscle at about the midpoint on its deep surface, often near the margin. This place of entrance is known as the motor point which allows the muscle to move with minimum interference with the nerve trunk Hilton's law : The motor nerve to a muscle tends to give a branch of supply to the joint which the muscle moves and another branch to the skin over the joint.