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MUSCULAR SYSTEM
HISTOLOGY
OBJECTIVES
• Be able to distinguish the three types of muscle at
the light microscope, including distinctive features of
each muscle fiber.
• Describe the structural basis of muscle striations.
• Know the structural elements that harness muscle
contraction (i.e., the shortening of myofibrils) to the
movement of a body part (i.e., via connection to
bone) as well as the mechanism by which muscle
cells contract
MUSCULAR SYSTEM
FUNCTIONS
• Body movement (Locomotion)
• Maintenance of posture
• Respiration
– Diaphragm and intercostal contractions
• Communication (Verbal and Facial)
• Constriction of organs and vessels
– Peristalsis of intestinal tract
– Vasoconstriction of b.v. and other structures (pupils)
• Heart beat
• Production of body heat (Thermogenesis)
PROPERTIES OF MUSCLE
• Excitability: Capacity of muscle to respond
to a stimulus
• Contractility: Ability of a muscle to shorten
and generate pulling force
• Extensibility: Muscle can be stretched back
to its original length
• Elasticity: Ability of muscle to recoil to
original resting length after stretched
TERMINOLOGIES
• Myofiber Or Myocyte: A muscle cell
• Sarcolemma: The plasma membrane of a muscle cell
• Sarcoplasm: The cytoplasm of the muscle cell
• Sarcoplasmic reticulum: The endoplasmic reticulum
of a muscle cell
• Sarcosome: The mitochondria of a muscle cell
• Sarcomere: The contractile or functional unit of
muscle
TYPES OF MUSCLE
• Skeletal
– Attached to bones
– Makes up 40% of body weight
– Responsible for locomotion, facial expressions, posture, respiratory
movements, other types of body movement
– Voluntary in action; controlled by somatic motor neurons
• Smooth
– In the walls of hollow organs, blood vessels, eye, glands, uterus, skin
– Some functions: propel urine, mix food in digestive tract,
dilating/constricting pupils, regulating blood flow,
– In some locations, autorhythmic
– Controlled involuntarily by endocrine and autonomic nervous systems
• Cardiac
– Heart: major source of movement of blood
– Autorhythmic
– Controlled involuntarily by endocrine and autonomic nervous systems
Skeletal
Muscle
Cardiac
Muscle
Smooth
Muscle
Skeletal Muscle Cardiac Muscle Smooth Muscle
SMOOTH MUSCLES
• Characteristics
– Spindle-shaped cells with
central nuclei
– Arranged closely to form
sheets
– No striations
– Single centrally located nucleus
– More actin than myosin
• Function
– Propels substances along
internal passageways
– Involuntary control
• Location
– Mostly walls of hollow organs
Smooth Muscles
CARDIAC MUSCLE
• Cardiac muscle cells are not as long as skeletal
muscles cells and often are branched.
• Cardiac muscle cells may be mononucleated
or binucleated.
• Nuclei are located centrally in the cell.
• Cardiac muscle is also striated.
• In addition cardiac muscle contains
intercalated discs
CARDIAC MUSCLE
SKELETAL MUSCLES
• Skeletal muscle cells are elongated or tubular.
• multiple nuclei located on the periphery of
the cell.
• Skeletal muscle is striated.
Skeletal muscle.
Are the striated voluntary
muscle held together by
connective tissue.
Epimysium: CT that
surrounds the entire
skeletal muscle.
Perimysium: CT
surrounds bundles of
muscle fiber.
Endomysium: CT
surrounds each muscle
fiber individually.
SKELETAL MUSCLE
Skeletal Muscle as seen in transverse section in the light microscope...
MUSCLE FIBER ANATOMY
• Sarcolemma - cell membrane
– Surrounds the sarcoplasm (cytoplasm of fiber)
• Contains many of the same organelles seen in other cells
• An abundance of the oxygen-binding protein myoglobin
• Myofibrils -cylindrical structures within muscle fiber
– Are bundles of protein filaments (=myofilaments)
• Two types of myofilaments
1. Actin filaments (thin filaments)
2. Myosin filaments (thick filaments)
– At each end of the fiber, myofibrils are anchored to the
inner surface of the sarcolemma
– When myofibril shortens, muscle shortens (contracts)
• Syncytium a bundle of smooth muscles fibres
contracting together
• SR is an elaborate, smooth endoplasmic reticulum
– runs longitudinally and surrounds each myofibril
• SR stores Ca++ when muscle not contracting
– When stimulated, calcium released into sarcoplasm
– SR membrane has Ca++ pumps that function to pump
Ca++ out of the sarcoplasm back into the SR after
contraction
CYTOSKELETAL
• The cytoskeleton of smooth muscles consists up
of intermediate filaments of desmin variety.
• The intermediate filaments and thin filaments
are inserted into Dense Bodies , they may be
located in the sarcoplasm or sarcolemma.
• Dense bodies
o Round, amorphous bodies scattered through
the cytoplasm of smooth muscle fibers; they
appear to be points of attachment for
myofilaments.
INNERVATION OF SMOOTH
MUSCLE
• Smooth muscle is primarily under the control of
autonomic nervous system.
• The single-unit smooth muscle has pacemaker
regions where contractions are spontaneously
and rhythmically generated.
• The fibers contract in unison, that is the single
unit of smooth muscle is syncytial.
• The fibers of multi-unit smooth muscle are
innervated by sympathetic and parasympathetic
nerve fibers and respond independently from
each other upon nerve stimulation.
Epimysium -
dense irr. c.t.
Perimysium -
less dense irr. c.t.
Endomysium -
basal lamina and
reticular fibers
Skeletal Muscle Investments
ALL MUSCLE
CELLS HAVE
BASAL LAMINAE!
THANK YOU

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muscle Histo.ppt

  • 2. OBJECTIVES • Be able to distinguish the three types of muscle at the light microscope, including distinctive features of each muscle fiber. • Describe the structural basis of muscle striations. • Know the structural elements that harness muscle contraction (i.e., the shortening of myofibrils) to the movement of a body part (i.e., via connection to bone) as well as the mechanism by which muscle cells contract
  • 3. MUSCULAR SYSTEM FUNCTIONS • Body movement (Locomotion) • Maintenance of posture • Respiration – Diaphragm and intercostal contractions • Communication (Verbal and Facial) • Constriction of organs and vessels – Peristalsis of intestinal tract – Vasoconstriction of b.v. and other structures (pupils) • Heart beat • Production of body heat (Thermogenesis)
  • 4. PROPERTIES OF MUSCLE • Excitability: Capacity of muscle to respond to a stimulus • Contractility: Ability of a muscle to shorten and generate pulling force • Extensibility: Muscle can be stretched back to its original length • Elasticity: Ability of muscle to recoil to original resting length after stretched
  • 5. TERMINOLOGIES • Myofiber Or Myocyte: A muscle cell • Sarcolemma: The plasma membrane of a muscle cell • Sarcoplasm: The cytoplasm of the muscle cell • Sarcoplasmic reticulum: The endoplasmic reticulum of a muscle cell • Sarcosome: The mitochondria of a muscle cell • Sarcomere: The contractile or functional unit of muscle
  • 6. TYPES OF MUSCLE • Skeletal – Attached to bones – Makes up 40% of body weight – Responsible for locomotion, facial expressions, posture, respiratory movements, other types of body movement – Voluntary in action; controlled by somatic motor neurons • Smooth – In the walls of hollow organs, blood vessels, eye, glands, uterus, skin – Some functions: propel urine, mix food in digestive tract, dilating/constricting pupils, regulating blood flow, – In some locations, autorhythmic – Controlled involuntarily by endocrine and autonomic nervous systems • Cardiac – Heart: major source of movement of blood – Autorhythmic – Controlled involuntarily by endocrine and autonomic nervous systems
  • 8. Skeletal Muscle Cardiac Muscle Smooth Muscle
  • 9. SMOOTH MUSCLES • Characteristics – Spindle-shaped cells with central nuclei – Arranged closely to form sheets – No striations – Single centrally located nucleus – More actin than myosin • Function – Propels substances along internal passageways – Involuntary control • Location – Mostly walls of hollow organs
  • 11.
  • 12. CARDIAC MUSCLE • Cardiac muscle cells are not as long as skeletal muscles cells and often are branched. • Cardiac muscle cells may be mononucleated or binucleated. • Nuclei are located centrally in the cell. • Cardiac muscle is also striated. • In addition cardiac muscle contains intercalated discs
  • 14. SKELETAL MUSCLES • Skeletal muscle cells are elongated or tubular. • multiple nuclei located on the periphery of the cell. • Skeletal muscle is striated.
  • 15. Skeletal muscle. Are the striated voluntary muscle held together by connective tissue. Epimysium: CT that surrounds the entire skeletal muscle. Perimysium: CT surrounds bundles of muscle fiber. Endomysium: CT surrounds each muscle fiber individually.
  • 17. Skeletal Muscle as seen in transverse section in the light microscope...
  • 18. MUSCLE FIBER ANATOMY • Sarcolemma - cell membrane – Surrounds the sarcoplasm (cytoplasm of fiber) • Contains many of the same organelles seen in other cells • An abundance of the oxygen-binding protein myoglobin • Myofibrils -cylindrical structures within muscle fiber – Are bundles of protein filaments (=myofilaments) • Two types of myofilaments 1. Actin filaments (thin filaments) 2. Myosin filaments (thick filaments) – At each end of the fiber, myofibrils are anchored to the inner surface of the sarcolemma – When myofibril shortens, muscle shortens (contracts)
  • 19. • Syncytium a bundle of smooth muscles fibres contracting together • SR is an elaborate, smooth endoplasmic reticulum – runs longitudinally and surrounds each myofibril • SR stores Ca++ when muscle not contracting – When stimulated, calcium released into sarcoplasm – SR membrane has Ca++ pumps that function to pump Ca++ out of the sarcoplasm back into the SR after contraction
  • 20. CYTOSKELETAL • The cytoskeleton of smooth muscles consists up of intermediate filaments of desmin variety. • The intermediate filaments and thin filaments are inserted into Dense Bodies , they may be located in the sarcoplasm or sarcolemma. • Dense bodies o Round, amorphous bodies scattered through the cytoplasm of smooth muscle fibers; they appear to be points of attachment for myofilaments.
  • 21. INNERVATION OF SMOOTH MUSCLE • Smooth muscle is primarily under the control of autonomic nervous system. • The single-unit smooth muscle has pacemaker regions where contractions are spontaneously and rhythmically generated. • The fibers contract in unison, that is the single unit of smooth muscle is syncytial. • The fibers of multi-unit smooth muscle are innervated by sympathetic and parasympathetic nerve fibers and respond independently from each other upon nerve stimulation.
  • 22. Epimysium - dense irr. c.t. Perimysium - less dense irr. c.t. Endomysium - basal lamina and reticular fibers Skeletal Muscle Investments ALL MUSCLE CELLS HAVE BASAL LAMINAE!