Muscular Tissues PDF

MUSCULAR TISSUES dr. ebtehal zaid hassen saleh Assistant Professor of Medical Histology and Cell Biology General characters of muscular tissue: 1- It consists of: - Muscle cells (fibers) - Rich capillary network - Supporting C.T. 2- Types of muscles: - Skeletal muscles - Cardia...

MUSCULAR TISSUES dr. ebtehal zaid hassen saleh Assistant Professor of Medical Histology and Cell Biology General characters of muscular tissue: 1- It consists of: - Muscle cells (fibers) - Rich capillary network - Supporting C.T. 2- Types of muscles: - Skeletal muscles - Cardiac muscles - Smooth muscles - Muscle fiber: is the muscle cell Sarcolemma = plasma membrane of muscle cells Sarcoplasm = cytoplasm of muscle cells. Sarcoplasmic reticulum = SER (smooth endoplasmic reticulum) of muscle cells. Sarcosomes = mitochondria  I. SKELETAL MUSCLE  All skeletal muscles are attached to the skeleton (so, called skeletal).  It is voluntary muscle (except in reflex arc and eye blinking).  Each muscle consists of: 1. Connective tissue component: - It consists of collagen fibers and fibroblasts. - It carries blood vessels, lymphatics and nerves to muscle cells. - It connects muscle fibers together and to bone by its continuity with tendons and aponeurosis. - It is located in the skeletal muscle: 1. Epimysium: a dense CT sheath covering the whole muscle fibers. 2. Perimysium: less dense connective tissue surrounds each bundle of muscle. 3- Endomysium: delicate CT sheath surrounds each muscle fiber.  2- Skeletal Muscle fibers:  Long, cylindrical in shape.  Multiple peripheral Nuclei.  Acidophilic cytoplasm.??? L.S T.S  2- Skeletal Muscle fibers: - In LS: the fiber shows alternating light and dark bands (transverse striations). - In TS: the fiber shows fine acidophilic dots. L.S T.S EM :  The sarcoplasm contains: ▪ Multiple nuclei ▪ Numerous parallel myofibrils ▪ Sarcoplasmic reticulum ▪ T tubules ▪ Numerous mitochondria ▪ Myoglobin (O2 binding protein), ▪ Glycogen & lipids 1. Numerous parallel myofibrils. Each myofibril is formed of large number of myofilaments (actin and myosin) that appear as alternating light and dark bands:  Light band = (I) band: is formed of thin actin filaments only. - A dense line called Z line or disk bisects each I band.  Dark band = (A) band: is formed of actin and myosin filaments. - The center of A band is occupied by a pale area called H band which is bisected by a thin; (M) line. Structure of Skeletal Muscle Fiber - The region of myofibril lying between two successive Z lines is called sarcomere (structural and functional unit of the muscle). - During muscle contraction, the actin filaments slide over the myosin filaments resulting in shortening of sarcomeres.  Skeletal Muscle (EM) Sarcomere: Structural & functional unit of skeletal ms NB.  Muscle fiber…Myofibrils (small units)…Myofilaments (actin & Myosin)  Actin filaments are present in A & I bands  Myosin filaments are present in A band only  Dark band= A band  Light band= I band N.B. satellite cells?? During contraction, actin glide (slide) over myosin causing shortening of sarcomere Skeletal Muscle Innervation 1- motor innervation (motor end plate):  II. CARDIAC MUSCLE  Have the same structure as the skeletal muscle with some differences:  The fibers have smaller diameter.  Each fiber is surrounded by a delicate C.T sheath rich in blood capillaries.  The fibers branch and anastomose with each other.  Each fiber contains large central oval nucleus.  The cytoplasm is granular acidophilic, and contains lipofuscin pigments which increase with age.  No satellite cells i.e.no stem cells are present.  The fibers are joined by intercalated disks, which appears as dark transverse line between the cardiac muscle fibers. 1- it prevents detachment of the cardiac muscle fibers from one another during contraction. 2- allow spreading of excitation waves through the muscle fibers.  III- Smooth Muscle Fibers - involuntary non- striated fibers. - Present in:  Wall of blood vessels.  Viscera of various systems (digestive, respiratory ….ect).  Structure:  Fusiform with single central nucleus.  Have the smallest diameter.  Have acidophilic cytoplasm with actin, myosin and intermediate filaments without special arrangement (No striations).  Their contraction occurs more slowly and lasts for longer duration.