Histo 2024 Muscular & Nervous T.-1.pdf

Muscular & Nervous Tissue  Histology & Cell Biology Team Medical College, Tiabah University Objectives At the end of this lecture, the student should know 1. Todemonstrate knowledge of the light and electron microscopic structure of skeletal muscle. 2. Tocompare between structure of...

Muscular & Nervous Tissue  Histology & Cell Biology Team Medical College, Tiabah University Objectives At the end of this lecture, the student should know 1. Todemonstrate knowledge of the light and electron microscopic structure of skeletal muscle. 2. Tocompare between structure of cardiac, smooth and skeletal muscles. 3. Toknow structure & classification of neurons. 4. Toknow types and structure of neuroglia. 5. Toknow structure of a peripheral nerve.  Muscular tissue 1. Skeletal muscle 2. Cardiac muscle 3. Smooth muscle Skeletal muscle  General characters 1. Sites:  All muscles attached to the skeleton.  Tongue muscles.  Eye muscles.  Pharynx and larynx. Mscell  Formed of a group of muscle fibres.  Cell membrane is called sarcolemma.  Cytoplasm is called sarcoplasm.  Cytoplasm contains myofibrils (contractile elements Actin and myocin).  Striated: cytoplasm has regular transverse striations.  Voluntary.  Organization of skeletal muscle  Whole muscle is surrounded by dense C.T. called epimysium(E)  Skeletal muscle is organized into bundles called fascicles. Organization of skeletal muscle Fascicles are separated by dense C.T. called perimysium……(P) Each Ms fibre is enclosed by loose C.T.called endomysium (En). E:Epimysium P:Perimysium EN: Endomysium LM of skeletal msfibers 1. Number of cells/fiber 2. Branching 3. Length 4. Diameter 5. Nucleus 6. Cytoplasm LM of skeletal ms fibers 1. Number: the fiber is formed of a Single elongated cell. origin insertion 2. No branching. 3. Length: from 1mm up to 30 cm. 4. Diameter: 10-100 um. micro 5. Nucleus: multinucleated, flattened & peripheral.makespaceForactinandmyosin 6. Sarcoplasm: acidophilic with regular striations (regular myofibrils). EM of skeletal msfibers 1. Cytoplasmiccontents 2. Myofibrils 3. Sarcomeres 1. Cytoplasmic contents smooth 1. Sarcoplasmic reticulum (SER). cat Distribution 2. Numerous mitochondria. 3. Myoglobin. 4. Beta glycogen granules. m.ca 5. Myofibrils (sarcostyles). mitochondria 2. Myofibrils  Longitudinal contractile elements in the sarcoplasm. actin aceinansmy.in  Myofibrils consist of light & dark bands.  Light band (I- band): contains thin filaments only.Actin  Dark band (A-band): contains thin and thick filaments. aceinandmyo.in  The dark band of one myofibril is present beside those of adjacent myofibril → cross striations seen by LM. 3. Sarcomeres tomere Functionstructureunitom f s  M Line : A dark line down the center of the sarcomere.  Z-lines: Dark lines in the center of the I bands.  Sarcomere begins from Z-line to Z-line. me  Each myofibril consists of successivesarcomeres. Cardiac muscle LM of cardiac muscle fibers  Site: in the wall of the heart.  Involuntary. 1. Number: Each fibre is formed of a chain of muscle cells linked by intercalated discs. 2. Branching and anastomosing fibers. 3. Length: variable. 4. Diameter: smaller than skeletal ms fibres. 5. Nucleus : central; one or two. 6. Cytoplasm: acidophilic with irregular striations. Smooth muscle LM of smooth muscle  Site: in the wall of viscera (GIT and urinary organs) and blood vessels.  Involuntary. 1. Number: Formed of a single cell. 2. Shape: fusiform (spindle-shaped). 3. Diameter: small. 4. Length: variable (30 µm in blood vessels & 500 µm in pregnant uterus). 5. Nucleus: single, oval nucleus, central in position. 6. Cytoplasm: acidophilic and non-striated.  Skeletal muscle Cardiac muscle Smooth muscle Number of Fiber is formed of one The fiber is formed of Asinglecell. cells/fiber cell. more than one cell. Branching No branching. Branching& No branching. anastomosing fibers. Length Very long: 1 mm up to 30 Variable in length. Variable in length. cm Diameter 10-100 micron. Lessthan skeletal muscle Smaller. fiber. Nucleus Multinucleated. One or two nuclei. Single oval nucleus. Flattened & peripheral Central nuclei. Central. nuclei. Cytoplasm Acidophilic. Acidophilic. Acidophilic. Regular striations. Irregularstriations. Non-  striated Nervous tissue Nervous system Anatomically: B. Peripheral nervous system (PNS) 1. Peripheral nerves. A. Central nervous system a. Cranial nerves. (CNS) b. Spinal nerves 1. Brain. 2. Ganglia. 2. Spinal cord. a. Cerebrospinal b. Autonomic.  Sympathetic.  Parasympathetic. Nervous system Histologically: A. Nerve cells (neurons)  Transmit nerve impulses and control body organs. B. Neuroglia  Occupy the interneuronal space.  Create a microenvironment suitable for neuronal activity. The neuron is composed of: 1. Cell body (perikaryon). 2. Processes: Axon andDendrites. Cell body (perikaryon)  Contains the nucleus and most of the organelles.  Act as a synthetic or trophic center for the entire neuron. 1. Nucleus:  Large and spherical.  Euchromatic with a prominent nucleolus (active). 2. Cytoplasm. exceptcentriolesneuronscan't devise A. Cytoplasmic organelles. B. Cytoskeleton. C. Cytoplasmic inclusions. Cytoplasmic contents A. Cytoplasmic organelles  Nissl bodies.  Golgi apparatus.  Mitochondria. B. Cytoskeleton  Neurofilaments. (intermediate filaments).  Microtubules. C. Cytoplasmic inclusions  Melanin pigments.  Lipofuscin pigments.  Basophilicrich inRERribosomes in Nissl bodies protein Acidophiliccontain Site: Scattered in the cytoplasm, EXCEPTin: o  Axon and axonhillock. o  Periphery of the nerve cell.  Around the nucleus. 0 LM: Basophilic granules. EM: Well developed rough endoplasmic reticulum (RER) & polyribosome. Function: synthesize proteins of nerve cell:  Cytoskeletal proteins.  Proteins for transport & secretion. Achieve Golgi apparatus Nissibodies Site: well developed, around the nucleus (perinuclear). Function: Packaging of proteins of the nerve cell to be secreted. Mitochondria cenbody Site: scattered in the perikaryon, axon and dendrites. Locatedinalloftheneuron Neuronal processes The axon The dendrites Number Single Multiple Length Very variable (may be Usually short very long or short) Branches Constant diameter. Inconstant diameter. Branches at its Extensive branching terminal end only along their course. E.M. Mitochondria. Mitochondria. Neurofibrils. Neurofibrils. No Nissl granules. Nissl granules Functions Conduct nerve Conduct nerve impulses impulses awayfrom to the cell body. the cell body.  Neuron Classification Physiological Number of processes classification Sensory Multipolar Motor Bipolar Interneurons Pseudounipolar Anaxonic neurons Types of Neurons neurons to the number of processes According 1. Multipolar neurons 2. Bipolar neurons 3. Pseudo-unipolar neurons 4. Anaxonic neurons NoAxon  Multipolar MCQ Multipolar neurons Polygonal neurons Pyramidal neurons Pyriform neurons Eg. Sympathetic ganglia Eg. Cerebral cortex Eg. Cerebellar cortex Ps.unipolar neurons Bipolar neurons Anaxonic neurons noactionpotential  Many dendrites with no axon.  Do not produce action potential, only regulates electrical changes of One process that divides adjacent neurons. into axon & dendrite. Example: Retina and  Example: interneurons Example: Spinal ganglia olfactory epithelium. of CNS& retina  II. NEUROGLIA (NEUROGLIAL CELLS)  Neuroglia are the supporting cells of the nervous tissue of CNS.  Number: 10 times more than neurons.  They provide mechanical and metabolic support to the neurons cell bodies and to the axons and dendrites for neuronal activity.  Neuroglia are not excitable cells, they do not generate, conduct or transmit impulses.  Unlike nerve cells, neuroglial cells are able to divide by mitosis. nervecellscan't  Types 1. Oligodendrocytes 2. Schwann cells 3. Astrocytes 4. Microglia 1. Oligodendrocytes Found in grey and white matter of the CNS Produce myelin in the CNS: cell processes wrap around more than one axon to form myelin. Myelin provides electric insulation of neurons in CNS. 2. Schwann cells f Function same Shaped like a rolled-up sheet of paper, Produce myelin in the PNS. Insulation of nerve impulse. Regeneration of peripheral nerves.  3. Astrocytes Star-shaped. Its processes surround blood vessels. The most numerous neuroglial cells. They are the main supporting cells of the CNS. Astrocytes proliferate to form scar tissue which fills in the damaged areas of the CNS. Neurons exchange their nutrients & waste products with blood through the processes of astrocytes. 4. Microglia Site: white & gray matters of CNS. Shape: spindle-shaped. It is phagocytic cells. Could be changed into macrophages to phagocytose foreign bodies or bacteria Oligodendrocytes Schwanncells Astrocytes Microglia Found in grey and white matter Found in the Its processessurround white & gray matters peripheral nervous blood vessels of CNS. of CNS of the CNS system Small cuboid cell body shape Shapedlike a rolled-up Star-shaped Spindle-shaped. sheet of paper, with few cytoplasmic processes and a small nucleus Produce myelin in the Produce myelin in They are the most Phagocytic cells. the PNS. numerous and main Could be changed CNS: Insulation of supporting cells of cell processes wrap into macrophages nerve impulse. the CNS around more than one Regeneration of Astrocytes proliferate to phagocytose axon to form myelin. peripheral to form scar tissue foreign bodies or nerves. which fills in the bacteria (brainme Myelin provides electric damaged areas of the insulation of neurons in CNS. macrophages). CNS. Exchange nutrients & waste products with blood through the processes of astrocytes. Peripheral nerve  Formed of groups (bundles) of nerve fibres separated by connective tissue  The nerve fibres may be myelinated or non-myelinated. Myelinated nerve fibre A. The axon: may be long or short B. The myelin sheath: cellmembrane  Concentric layers of lipoprotein.  Formed by Schwann cells.  Insulates the axon & provides suitable environment for action potential. C. Schwann cells:  Achain of cells that cover the axon.  Forms myelin sheath. A: axon. M: myelin sheath. SC:Schwanncell. UM: unmyelinated fiber.. Resources 1. Junqueira LC,Carneiro J:Basic Histology. Text and Atlas, 11th edition (2005), LANGEMc Graw Hill, Chapter: 8, PP: 160-211. 2. Young B, Heath JW: WHEATER´sFunctional Histology. AText and Colour Atlas (2001). Churchill Livingstone. Chapter 9, PP: 101-143.