MUSCLE TISSUE Larry Johnson Texas A&M University
Objectives
• Histologically identify and functionally characterize each of the 3 types of muscle tissues.
• Describe the organization of the sarcomere as seen in light and electron microscopy.
• Identify the endomysium, perimysium, and epimysium CT sleeves in muscle.
• Relate the functional differences of the three muscle cell types. From: Douglas P. Dohrman and TAMHSC Faculty 2012 Structure and Function of Human Organ Systems, Histology Laboratory Manual MUSCLE FUNCTION: • GENERATION OF CONTRACTILE FORCE
DISTINGUISHING FEATURES: • HIGH CONCENTRATION OF CONTRACTILE PROTEINS ACTIN AND MYOSIN ARRANGED EITHER DIFFUSELY IN THE CYTOPLASM (SMOOTH MUSCLE) OR IN REGULAR REPEATING UNITS CALLED SARCOMERES (STRIATED MUSCLES, e.g., CARDIAC AND SKELETAL MUSCLES) MUSCLE
• DISTRIBUTION:
SKELETAL – STRIATED MUSCLES MOSTLY ASSOCIATED WITH THE SKELETON
MUSCLE
• DISTRIBUTION:
SKELETAL – STRIATED MUSCLES MOSTLY ASSOCIATED WITH THE SKELETON
CARDIAC – STRIATED MUSCLES ASSOCIATEWD WITH THE HEART
MUSCLE
• DISTRIBUTION:
SKELETAL – STRIATED MUSCLES MOSTLY ASSOCIATED WITH THE SKELETON
CARDIAC – STRIATED MUSCLES ASSOCIATEWD WITH THE HEART
SMOOTH – FUSIFORM CELLS ASSOCIATED WITH THE VISCERA, RESPIRATORY TRACT, BLOOD VESSELS, UTERUS, ETC. MUSCLE
• HISTOLOGICAL INDENTIFICATION: SKELETAL MUSCLE – VERY LONG CYLINDRICAL STRIATED MUSCLE CELLS WITH MULTIPLE PERIPHERAL NUCLEI
MUSCLE
• HISTOLOGICAL INDENTIFICATION: SKELETAL MUSCLE – VERY LONG CYLINDRICAL STRIATED MUSCLE CELLS WITH MULTIPLE PERIPHERAL NUCLEI
CARDIAC MUSCLE – SHORT BRANCHING STRIATED MUSCLE CELLS WITH CENTRALLY LOCATED NUCLEI
MUSCLE
• HISTOLOGICAL INDENTIFICATION: SKELETAL MUSCLE – VERY LONG CYLINDRICAL STRIATED MUSCLE CELLS WITH MULTIPLE PERIPHERAL NUCLEI
CARDIAC MUSCLE – SHORT BRANCHING STRIATED MUSCLE CELLS WITH CENTRALLY LOCATED NUCLEI
SMOOTH MUSCLE – CLOSELY PACKED SPINDLE-SHAPED CELLS WITH A SINGLE CENTRALLY PLACED NUCLEUS AND CYTOPLASM THAT APPEARS HOMOGENEOUS BY LIGHT MICROSCOPY MUSCLE
• HISTOLOGICAL INDENTIFICATION: SKELETAL MUSCLE – VERY LONG CYLINDRICAL STRIATED MUSCLE CELLS WITH MULTIPLE Myoepithelial cells PERIPHERAL NUCLEI
CARDIAC MUSCLE – SHORT BRANCHING STRIATED MUSCLE CELLS WITH CENTRALLY LOCATED NUCLEI
SMOOTH MUSCLE – CLOSELY PACKED SPINDLE-SHAPED CELLS WITH A SINGLE CENTRALLY PLACED NUCLEUS AND CYTOPLASM THAT APPEARS HOMOGENEOUS BY LIGHT MICROSCOPY Muscle Tissue
• Muscle cells specialized for contraction with apparatus of actin and myosin proteins. • 3 types:
Skeletal Muscle Smooth Muscle Cardiac Muscle Longitudinal sections Longitudinal sections Longitudinal sections - Peripheral nuclei - Central nuclei (often - Central nuclei (often - Striations fusiform) elongated) - No branching - Meshwork - Striations appearance of cells - Branching cells - No striations - Intercalated discs Cross section Cross section Cross section - Peripheral nuclei - Central nuclei - Central nuclei - Massive cytoplasm - Low cytoplasm to - High cytoplasm to nucleus ratio nucleus ratio Slide 11: Skeletal muscle (longitudinal and cross sections)
Muscle fibers with peripheral Capillary Cross sections of nuclei muscle fibers with peripheral nuclei
Slide 052: Skeletal muscle (longitudinal and cross sections)
Muscle fibers with peripheral Cross striations nuclei Capillary (A and I bands) Slide 052: Skeletal muscle (longitudinal and cross sections)
Muscle fibers with peripheral Cross striations nuclei Capillary (A and I bands) The increase in muscle mass during exercise results from stimulating formation of new myofibrils and enlargement in the diameter of individual muscle fibers (hypertrophy = increase in size). CONNECTIVE TISSUE LAYERS OF SKELETAL MUSCLE • EPIMYSIUM - COARSE CT
EPIMYSIUM CONNECTIVE TISSUE LAYERS OF SKELETAL MUSCLE • EPIMYSIUM - COARSE CT • PERIMYSIUM - LESS COARSE CT
PERIMYSIUM
EPIMYSIUM CONNECTIVE TISSUE LAYERS OF SKELETAL MUSCLE • EPIMYSIUM - COARSE CT • PERIMYSIUM - LESS COARSE CT • ENDOMYSIUM - DELICATE CT PERIMYSIUM
EPIMYSIUM
ENDOMYSIUM CONNECTIVE TISSUE LAYERS OF SKELETAL MUSCLE EPIMYSIUM, PERIMYSIUM, and ENDOMYSIUM Slide 11: Skeletal muscle (longitudinal and cross sections)
Epimysium
Perimysium
Endomysium Slide 052 Skeletal muscle (longitudinal and cross sections)
Perimysium
Endomysium with its capillaries CONNECTIVE TISSUE connect LAYERS OF SKELETAL MUSCLE
• ENDOMYSIUM CONNECTIVE TISSUE LAYERS OF SKELETAL MUSCLE PERIMYSIUM CONNECTIVE TISSUE LAYERS OF SKELETAL MUSCLE PERIMYSIUM
052
• ENDOMYSIUM Striations in skeletal muscle 052
Skeletal muscles have striations, peripheral nuclei, same thickness throughout their length and do not branch. Specialized for powerful and rapid contraction. Voluntary. Found attached to the skeleton. Slide 12: Skeletal muscle (phosphotungstic acid/hematoxylin)
Sarcomere: Z line to Z line
Z line is In the I band
I band A band STRIATED MUSCLE
CARDIAC
SKELETAL A
“A” BAND = dark band ANISOTROPIC = DOES ALTER POLARIZED LIGHT (BIREFRINGENT)
STRIATED MUSCLE
CARDIAC
SKELETAL A I
“A” BAND = dark band ANISOTROPIC = DOES ALTER POLARIZED LIGHT (BIREFRINGENT)
“I” BAND = light band ISOTROPIC = DOES NOT ALTER POLARIZED LIGHT
STRIATED MUSCLE (SKELETAL) A I
SARCOMERES ARE ORGANIZED FOR RAPID AND HIGHLY CONTROLLED CONTRACTION SKELETAL MUSCLE cell structure SKELETAL MUSCLE
SKELETAL MUSCLE
INTERMEDIATE FILAMENTS – FUNCTION in muscle cells
• MYOFIBRIL ORGANIZATION – MUSCLE cells INTERMEDIATE FILAMENTS – FUNCTION in muscle cells
• MYOFIBRIL ORGANIZATION – MUSCLE cells
Cell = CONTRACTION OF THE SARCOMERE • THIN FILAMENT ACTIN (F-ACTIN) TROPOMYOSIN TROPONIN T - ATTACHES TO TROPOMYOSIN C - BINDS CALCIUM IONS I - INHIBITS ACTIN-MYOSIN INTERACTION
The stoppage of the neural impulse and depletion of free calcium ends the actin- myosin crossbridge cycle in skeletal muscle. ATP is required in this process.
. CALCIUM REGULATION
• TRANVERSE (T) TUBULE (INVAGINATION OF SARCOLEMMA) • TRANSMIT DEPOLARIZATION OF MEMBRANE DEEP INTO THE CELL • SARCOPLASMIC RETICULUM (SER OF CELL) RELEASE CA++ FOR CONTRACTION - THEN RECOVER CA++ • AFTER CONTRACTION • TRIAD = (T TUBULE AND TWO ENDS OF SER) EM 29 : Skeletal muscle
052 EM 46 and 47 : Skeletal muscle STIMULATION OF MUSCLE CELLS
Slide 13: Skeletal Muscle – muscle spindles (trichrome)
Intrafusal muscle fibers
Muscle spindle: (stretch receptors)
Nerve fibers INNERVATION OF MUSCLE
MUSCLE SPINDLE
MUSCLEIntracapsular SPINDLE fibers SMOOTH MUSCLE SMOOTH MUSCLE Has a PAS + basement membrane Slide 35: Urinary bladder
Muscularis externa (smooth muscle) Smooth muscle fibers with central nuclei Smooth muscles are fusiform with tapered ends, single, central nuclei, and no striations. Involuntary. Found in sphincters and sheets of internal visceral organs and glands. Slide 63: Appendix
Submucosa Muscularis externa Smooth muscle layer arrangement in tubular organs The layering of smooth muscle in the gut is responsible for contractions which mix and propel luminal contents forward. Actin EM 49: Smooth muscle Myosin SMOOTH MUSCLE MUSCULAR ARTERY
Skeletal Smooth Muscle muscle CARDIAC MUSCLE IS STRIATED MUSCLE •INTERCALATED DISC • FASCIA ADHERENS • MACULAE ADHERENS • GAP JUNCTIONS - LATERAL PORTION CARDIAC MUSCLE INTERCALATED DISC
The intercalated discs enables coordinated function via gap junctions to facilitate energy and calcium conductance between neighboring myocytes. pulmonary artery in the INTERCALATED lungs of a rat DISC pulmonary artery in the INTERCALATED lungs of a rat DISC
nucleus mitochondria Slide 14: Heart & EM 48: Heart
Intercalated discs CARDIAC MUSCLE – Diad located at Z line
Diad = (T tubule + one end of SER) REGENERATION OF MUSCLE Which type of muscle cells can be replaced in adults?
•SMOOTH – LOTS
•SKELETAL – SOME
•CARDIAC – NONE
Clinical Correlation
Ischemic heart disease is one of the most significant health problems in the US. Coronary artery thrombosis usually precedes and precipitates a myocardial infarct, resulting in the death of cardiac myocytes. Eventually scar tissue is formed and there is some loss of contractility.
Image taken from adultstemcellawareness.wordpress.com Lacking muscle mesenchymal satellite cells, adult mammalian cardiac muscle has little potential to regenerate after injury. Damage is replaced by proliferating fibroblasts and connective tissue growth, forming myocardial scars. Summary of MUSCLE shapes and excitations of types Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources!
• Bruce Alberts, et al. 1983. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. • Bruce Alberts, et al. 1994. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY.
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• Nature (http://www.nature.com), Vol. 414:88,2001.
• A.L. Mescher 2013 Junqueira’s Basis Histology text and atlas, 13th ed. McGraw
• Douglas P. Dohrman and TAMHSC Faculty 2012 Structure and Function of Human Organ Systems, Histology Laboratory Manual - Slide selections were largely based on this manual for first year medical students at TAMHSC The end!