Histology of Muscle 1.pptx

Muscle Tissue Anatomy Unit  Objectives Identify basic structure of Muscles Recognize types of muscular tissues and the difference between them Recognize the relation between structure and function of various muscular tissues  Characters of muscle tissue The m...

Muscle Tissue Anatomy Unit  Objectives Identify basic structure of Muscles Recognize types of muscular tissues and the difference between them Recognize the relation between structure and function of various muscular tissues  Characters of muscle tissue The muscle tissue is formed of a group of muscle fibers. have a contractility power due to presence of (myofibrils) in cytoplasm. The cell membrane is called the sarcolemma. The cytoplasm is called the sarcoplasm. The muscle fibers may be: - Striated or Non-striated. Voluntary or Involuntary. Types of muscle fibers 1. Skeletal muscle fibers. 2. Cardiac muscle fibers. 3. Smooth muscle fibers.  SKELETAL MUSCLE FIBERS Characters: Striated (show transverse dark and light band). Voluntary except:  Upper third of esophagus.  Pharynx.  Cremastric muscle. Do not branch except: tongue and face. SKELETAL MUSCLE FIBERS Sites:  All skeletal muscles are attached to skeleton.  Eye.  Tongue. Structure of skeletal muscle fibers It is formed of cells (fibers) and connective tissue.  A. Connective tissue: 1-Epimysium - It is a dense C.T. which surrounds the whole muscle. 2-Perimysium - It is a dense C.T. which divides the muscle into bundles. 3-Endomysium: - It is a loose C.T. which separates the muscle fibers. B- Skeletal muscle fiber: LM of skeletal muscle fiber: L/S: Single elongated multinucleated cell (syncytium). Have multiple flattened oval peripherally situated nuclei. Have regular transverse striation. The sarcoplasm is acidophilic and contains: B-Glycogen granules. & Myoglobin pigment.  B- Skeletal muscle fiber: T/S: Polyhedral in shape. The nucleus may be seen in some fibers. The sarcoplasm may show dark areas (Cohnheim’s areas) due to grouping of the myofibrils.  Myofibrils (Sarcostyles) Definition: These are contractile elements longitudinally arranged in the sarcoplasm of the skeletal muscle fiber. Structure: The myofibril shows alternating light and dark bands. The light band (Isotropic or I- band) is pale in living fibers. The dark band (Anisotropic or A- band) is dark in fresh state.  Myofibrils (Sarcostyles) The dark band of one myofibril is present beside those of adjacent myofibril giving the cross striation seen by light microscope. Each dark band is divided at its center by a light disc called H-zone. Each light band is divided at its center by a dark line called Z-line.  Myofibrils (Sarcostyles ) The Sarcomere: It is the area between two Z-lines. It is the functional contractile unit of a myofibril. It includes a whole A (dark band) and ½ of I (light band) on either side. It contains minute structure called The myofilame nts These are thread-like filaments which are longitudinally arranged in the myofibrils. The myofilaments  N.B.: The A band is dark as it contains actin and myosin filament. The I band is light as it contains only actin filament. The H- zone is light as it contains only myosin filaments. The Z-line is dark as it contains other types of filaments and due to interdigitation of actin filaments.