Basic Tissues 3 - Muscle Tissue PDF

BASIC TISSUES 3 MUSCLE TISSUE STEPHEN K AMOAH UCCSMS LR 2 29/04/2022  OBJECTIVES Know the cellular composition of muscle tissue (MT). Know the types, features & functions of MT tissue. Know the types & features of connective tissue present in MT. Know composition of fiber...

BASIC TISSUES 3 MUSCLE TISSUE STEPHEN K AMOAH UCCSMS LR 2 29/04/2022  OBJECTIVES Know the cellular composition of muscle tissue (MT). Know the types, features & functions of MT tissue. Know the types & features of connective tissue present in MT. Know composition of fibers in MT Know the basis of muscular contraction Know microscopic features of bone Answer simple examination questions on MT MUSCLE TISSUE – INTRODUCTION Mesodermal origin Cells containing actin and myosin contractile (contractile elements) Single cell contractile units Myoepithelial cells Pericytes Myofibroblasts MUSCLE TISSUE - INTRODUCTION Composed of specialised called myocytes which contracts Sarcomere: cytoplasm of myocyte Sarcolemma: cell membrane of myocyte Sarcoplastic reticulum: surrounds muscle fibre Myocytes composed of contractile protein filaments i.e. myofilaments: myosin & actin TYPES OF MUSCLE TISSUE Skeletal Cardiac Smooth TYPES OF MUSCLE TISSUE  Skeletal (Striated) Muscle Cells are elongated Multinucleated Peripherally located nuclei. Large, very long, unbranched cylindrical fibres Multiple, subsarcolemmal nuclei Strong quick intermittent contractions Voluntary (or reflexive), controlled by somatic nervous system SKELETAL MUSCLE Skeletal muscle can hypertrophy by growth of new myofibrils & thickening of diameter Hypertrophy Cells contains orderly arranged contractile units, sarcomeres forming cross striations Type I Type II  SKELETAL MUSCLE – Muscle fiber types Type I muscle fiber (slow oxidative) Rich capillary supply Numerous mitochondria Aerobic respiration High myoglobin content → red fibers Less prone to fatigue Do not produce high tension Function: maintaining posture, stabilizing bones and joints  SKELETAL MUSCLE – Muscle fiber types Type IIa (fast oxidative/ intermediate) Produce ATP relatively quickly Produce high amounts of tension High amount of mitochondria Aerobic respiration Myoglobin content less than type I Less prone to fatigue Function: walking  SKELETAL MUSCLE – Muscle fiber types Type IIb/IIx (fast glycolyis) Anaerobic glycolysis Less mitochondria (white) Less myoglobin Rapid forceful contraction Quick powerful movements Prone to fatigue; Use in short period of time Function: weight lifting COMPOSITION OF SARCOMERE I-band - actin filaments, A-band - myosin filaments which may overlap with actin filaments H-band - zone of myosin filaments within the A-band Z-line - zone of apposition of actin filaments belonging to 2 neighbouring sarcomeres (mediated by alpha-actinin)  CONSTITUENTS OF SARCOMERE M-line - band of connections between myosin filaments (mediated by proteins, e.g. creatinine phosphate myomesin, M-protein). T-tubule Sarcoplasmic reticulum Triad External lamina KELETAL MUSCLE CONTRACTION  MUSCLE TISSUE SKELETAL MUSCLES Highly vascularised Myoneural junction / motor end plate Muscle tendon junction CT of muscle Myasthenia gravis MUSCLE TISSUE SKELETAL MUSCLES A top-down view of skeletal muscle  TYPES OF SUPPORTING TISSUE Epimysium: surround entire muscle bundle e.g. temporalis fascia Endomysium: surround entire muscle fascicle Endomysium: surrounds muscle fiber Smooth Muscle Found in walls of hollow viscera & blood vessels; erector pili 30 – 200 μm in relaxed state Single small spindle-shaped fibers No striations Single central nucleus Weak, slow rhythmic contractions Controlled by autonomic nervous system Mode of contraction Smooth Muscle SMOOTH MUSCLE Ca release → Ca- calmodulin complex → myosin light chain → phosphorylates myosin → binding to actin → sliding filament contraction Calmodulin, cAMP Progesterone relaxes smooth muscles SMOOTH MUSCLE BONES Bone is a hard and rigid form of connective tissue with an extracellular matrix impregnated with inorganic salts e.g. Ca phosphate and carbonate Features Sclerous connective tissue specialized to provide support because of infiltration with inorganic salts It is characterized by its rigidity, hardness, and power of regeneration and repair Dynamic and living constantly undergoing remodeling to adapt to changing physical, biochemical, hormonal influences Functions:  COMPOSITION OF BONE - CELLS The osteoblast is responsible for forming new bone and is found in the growing portions of bone, including the periosteum and endosteum. Osteoblasts do not divide, they synthesize and secrete the collagen matrix and calcium salts. They are derived from osteoprogenitor cells, a mesenchymal stem cell line. The osteocyte is the primary cell of mature bone and the most common type of bone cell. Located in a space called a lacuna and surrounded by bone tissue. Maintains the mineral concentration of the matrix via the secretion of enzymes. Lacks mitotic activity. Communicate with each other and receive nutrients via long cytoplasmic processes that extend through canaliculi within the bone matrix. http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf  COMPOSITION OF BONE - CELLS The osteoclast is responsible for bone resorption. Found on bone surfaces, multinucleated, and originates from monocytes and macrophages. “Bone version” of macrophages. Howship’s lacuna. Osteogenic cells are undifferentiated with high mitotic activity and they are the only bone cells that divide. Immature osteogenic cells are found in the deep layers of the periosteum and the marrow. They differentiate and develop into osteoblasts. http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf  COMPOSITION OF BONE - MATRIX The extracellular matrix refers to the non-cellular component of the bone comprising organic and inorganic matter The ECM of bone is highly specialized. In addition to collagen and the associated proteins in CT, bone is impregnated with mineral salts, in particular calcium hydroxyapatite crystals. These crystals associate with the collagen fibers, making bone hard and strong. This matrix is organized into numerous thin layers, known as lamellae http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf  COMPACT AND SPONGY BONE Woven bone (primary bone) – Appears in embryonic development and fracture repair, as it can be laid down rapidly. Lamellar bone (secondary bone) – The bone of the adult skeleton. It consists of highly organized sheets of mineralized osteoid. This organized structure makes it much stronger than woven bone. Lamella bone itself can be divided into two types – compact and spongy. http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf  COMPACT AND SPONGY BONE COMPACT BONE SPONGY BONE Tightly packed tissue. Cancellous or Trabecular The outer layer, under the bone periosteum of the diaphysis Found in epiphyses of long and epiphysis. and also in short ,flat and Cortical bone Microscopic irregular bones structural unit of compact Built of numerous branching bone is called an osteon, or bony plates - in complete Haversian system osteons Spaces reduce weight http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf  COMPACT BONE http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf  READING ASSIGNMENT Mineralization of bone http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf http://anatomy.plcnet.org/files/Lectures/English_1_2/2019/WELCOME%20TO%20ANATOMY-OSTEOLOGY_D.pdf