Muscular Tissue PDF

MUSCULAR TISSUE Dr.Ebtehal Zaid Hassan 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 TISSUE Dr.Ebtehal Zaid Hassan 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.??? In LS: the fiber shows alternating light and dark bands (transverse striations). T.S L.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 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…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 During contraction, actin glide (slide) over myosin causing shortening of sarcomere  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.