Muscular Tissue Histology Lecture Notes PDF

Histology Lecture Notes Dr. Shaimaa Kashef Muscular Tissue Muscle tissue consists of elongated cells called muscle fibers. Its cell membrane is called sarcolemma, and its cytoplasm is called sarcoplasm. The sarcopla...

Histology Lecture Notes Dr. Shaimaa Kashef Muscular Tissue Muscle tissue consists of elongated cells called muscle fibers. Its cell membrane is called sarcolemma, and its cytoplasm is called sarcoplasm. The sarcoplasm contains contractile elements called myofibrils. - There are three types of muscle tissue: - 1. Skeletal muscles. 2. Cardiac muscles. 3. Smooth muscles. 1- Skeletal Muscle They are called skeletal as they are attached to the skeleton and responsible for body movements. They are striated because they have transverse bands. They are voluntary in action because they are under the control of the will. Gross structure of muscle and the surrounding connective tissue (Fig.11) The muscles are arranged in a special structure: Whole muscle: It is made up of multiple muscle fascicles and surrounded by epimysium (an external sheath of connective tissue surrounding the whole muscle). Muscle fascicle: It is made up of bundles of individual muscle fibers surrounded by perimysium (a thin sheath of connective tissue). Muscle fibers: Individual muscle cells (but typically called “fibers” because they are so long). Immediately enclosed by sarcolemma. They are surrounded by endomysium that contain capillaries and nerve fibers to supply each cell/fiber. Myofibrils: Long functional subunits made up of myofilaments within a muscle cell Myofilaments: individual contractile proteins (actin &myosin). 1 Histology Lecture Notes Dr. Shaimaa Kashef Figure (11): Structure of skeletal muscle. L.M.: - Skeletal muscle fibers are elongated and vary in length. -The muscle fibers do not branch except the tongue and face muscles - They are multinucleated. The nuclei are oval in shape and peripheral in position (lie under the sarcolemma). - The sarcoplasm is deeply acidophilic and showing cross striations as it contains longitudinal, cylindrical parallel myofibrils. Figure (12): Light microscopic structure of skeletal muscle 2 Histology Lecture Notes Dr. Shaimaa Kashef E.M (Fig.13): - The sarcoplasm contains longitudinal, cylindrical parallel myofibrils, numerous mitochondria and well-developed sarcoplasmic reticulum. - Each myofibril shows alternating dark and light transverse bands which are responsible for transverse striation of the muscle fiber. - The dark bands called A bands and light bands called I bands. - The I band is formed by actin thin filaments. - The A band is formed by both thick myosin and thin actin filaments. - The dark A bands are bisected by paler region called H zone. - H zone contains myosin filaments only. - The light I bands are bisected by dark line called Z line, as actin filaments are attached to Z line. - The distance between two Z lines is known as the sarcomere. - Sarcomere is the structural and functional unit of the skeletal muscle, it contains one A band separating two halves I bands. Figure (13): Structure of skeletal muscle. 3 Histology Lecture Notes Dr. Shaimaa Kashef Test yourself Q1. MCQ 1) Which one of the following zones are forming the sarcomere? A) Complete A band and two halves of I band. B) Complete I band and two halves of A band. C) One zone of A band and one zone of I band. D) Half zone of A band and half zone of I band. 2) Name the dense connective tissue that surrounds the whole skeletal muscle. A) Perimysium B) Endomysium C) Epimysium D) Ectomysium Q2. Complete the missing data 4