CHAPTER 9: MUSCLES AND MUSCLE TISSUE
OVERVIEW OF MUSCLE TISSUE
Types of muscle tissue:
Skeletal muscle tissue: Skeletal muscle tissue is attached to the bones of the skeleton and allows the skeleton to
move. It’s striated (alternating light and dark bands of muscle proteins) and voluntary (consciously controlled by
motor neurons of the somatic nervous system).
Cardiac muscle tissue: Cardiac muscle tissue forms the heart wall, and it’s composed of cardiac muscle fibers
(contractile cells of the heart). It’s striated and involuntary (not consciously controlled; controlled and regulated by
motor neurons of the autonomic nervous system) . It’s composed of pacemaker cells t hat function in
autorhythmicity, and it remains contracted 10-15 times longer than skeletal muscle tissue. Cardiac muscle fibers
have larger and more numerous mitochondria than skeletal muscle fibers, and they are autorhythmic (cells can
spontaneously contract on their own without stimulation from motor neurons). Cardiac muscle fibers depend on
aerobic cellular respiration to synthesize ATP, so they require a constant supply of oxygen, and they can use
lactic acid produced by skeletal muscle fibers to synthesize ATP, which is important during exercise.
Smooth muscle tissue: Smooth muscle tissue forms the walls of hollow internal organs (EX: blood vessels,
organs in the abdominopelvic cavity – stomach, small intestine, large intestine, urinary bladder, reproductive
organs, organs in the respiratory tract – bronchioles). It’s non-striated and involuntary (not consciously controlled;
controlled and regulated by motor neurons of the autonomic nervous system).
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,CHAPTER 9: MUSCLES AND MUSCLE TISSUE
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, CHAPTER 9: MUSCLES AND MUSCLE TISSUE
Functions of muscle tissue:
1. Movement of body: Skeletal muscle tissue moves body structures with the coordination and integration of
bones and joints.
2. Stabilizes body position: Contraction of skeletal muscles aids in stabilizing joints and helps maintain body
position (EX: sustained contractions of neck muscles hold the head upright).
3. Stores and moves substances within the body: Muscle tissue is capable of storing and moving substances via
contraction and relaxation of the tissue (EX: contraction and relaxation of smooth muscle tissue in the walls of
blood vessels adjusts blood-vessel diameter in order to aid in blood circulation and regulate blood flow).
4. Generates heat: Muscle tissue produces heat when it contracts, which is used to maintain body temperature
(EX: shivering, which is involuntary contractions of skeletal muscle tissue, increases the rate of heat production in
the body).
Properties of muscle tissue:
1. Electrical excitability: This is the ability of the muscle tissue to respond to specific stimuli by producing
electrical signals/messages, which causes muscle tissue to contract or relax depending on the stimuli that is
detected.
2. Contractility: This is the ability of muscle tissue to contract forcefully when stimulated by an electrical
signal/message.
3. Extensibility: This is the ability of muscle tissue to stretch without being damaged and to allow muscle tissue
to contract forcefully even it is already stretched. Smooth and cardiac muscle tissues are subject to the most
frequent stretching.
4. Elasticity: This is the ability of muscle tissue to return to its original length and shape following contraction or
extension.
SKELETAL MUSCLE TISSUE
Skeletal muscle tissue: Each skeletal muscle is a separate organ composed of thousands of muscle fibers. Connective
tissue surrounds muscle fibers, whole muscles, blood vessels, and nerves.
Muscle fibers: Muscle fibers are muscle cells that compose muscle tissue and are referred to as fibers due to
their elongated shape.
Connective tissue components:
Fascia: Sheet or band of connective tissue that supports and surrounds skeletal muscles.
Superficial fascia: This type of fascia separates skeletal muscle tissue from the skin. It is, actually, the
hypodermis (subcutaneous layer) of the skin and is composed of adipose tissues and areolar connective
tissue. It serves as a pathway for nerves, blood vessels, and lymphatic vessels to enter and exit the
muscle tissue. The adipose tissue of the superficial fascia functions to reduce heat loss from the body
and protects skeletal muscles from physical trauma.
Deep fascia: This type of fascia is composed of dense irregular connective tissue, and it lines the body
wall and limbs, and holds muscles with similar functions together. Deep fascia functions to allow muscles
to move freely.
Epimysium: Outermost layer of the deep fascia composed of dense irregular connective tissue, and it surrounds
the entire muscle.
Perimysium: Connective tissue layer that surrounds 10-100 or more skeletal muscle fibers. It separates the
muscle fibers into bundles called fascicles.
Fascicles: Bundles of skeletal muscle fibers that are covered by perimysium.
Endomysium: Thin sheath of areolar connective tissue that covers each individual muscle fiber within the
fascicles.
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OVERVIEW OF MUSCLE TISSUE
Types of muscle tissue:
Skeletal muscle tissue: Skeletal muscle tissue is attached to the bones of the skeleton and allows the skeleton to
move. It’s striated (alternating light and dark bands of muscle proteins) and voluntary (consciously controlled by
motor neurons of the somatic nervous system).
Cardiac muscle tissue: Cardiac muscle tissue forms the heart wall, and it’s composed of cardiac muscle fibers
(contractile cells of the heart). It’s striated and involuntary (not consciously controlled; controlled and regulated by
motor neurons of the autonomic nervous system) . It’s composed of pacemaker cells t hat function in
autorhythmicity, and it remains contracted 10-15 times longer than skeletal muscle tissue. Cardiac muscle fibers
have larger and more numerous mitochondria than skeletal muscle fibers, and they are autorhythmic (cells can
spontaneously contract on their own without stimulation from motor neurons). Cardiac muscle fibers depend on
aerobic cellular respiration to synthesize ATP, so they require a constant supply of oxygen, and they can use
lactic acid produced by skeletal muscle fibers to synthesize ATP, which is important during exercise.
Smooth muscle tissue: Smooth muscle tissue forms the walls of hollow internal organs (EX: blood vessels,
organs in the abdominopelvic cavity – stomach, small intestine, large intestine, urinary bladder, reproductive
organs, organs in the respiratory tract – bronchioles). It’s non-striated and involuntary (not consciously controlled;
controlled and regulated by motor neurons of the autonomic nervous system).
Page 1
,CHAPTER 9: MUSCLES AND MUSCLE TISSUE
Page 2
, CHAPTER 9: MUSCLES AND MUSCLE TISSUE
Functions of muscle tissue:
1. Movement of body: Skeletal muscle tissue moves body structures with the coordination and integration of
bones and joints.
2. Stabilizes body position: Contraction of skeletal muscles aids in stabilizing joints and helps maintain body
position (EX: sustained contractions of neck muscles hold the head upright).
3. Stores and moves substances within the body: Muscle tissue is capable of storing and moving substances via
contraction and relaxation of the tissue (EX: contraction and relaxation of smooth muscle tissue in the walls of
blood vessels adjusts blood-vessel diameter in order to aid in blood circulation and regulate blood flow).
4. Generates heat: Muscle tissue produces heat when it contracts, which is used to maintain body temperature
(EX: shivering, which is involuntary contractions of skeletal muscle tissue, increases the rate of heat production in
the body).
Properties of muscle tissue:
1. Electrical excitability: This is the ability of the muscle tissue to respond to specific stimuli by producing
electrical signals/messages, which causes muscle tissue to contract or relax depending on the stimuli that is
detected.
2. Contractility: This is the ability of muscle tissue to contract forcefully when stimulated by an electrical
signal/message.
3. Extensibility: This is the ability of muscle tissue to stretch without being damaged and to allow muscle tissue
to contract forcefully even it is already stretched. Smooth and cardiac muscle tissues are subject to the most
frequent stretching.
4. Elasticity: This is the ability of muscle tissue to return to its original length and shape following contraction or
extension.
SKELETAL MUSCLE TISSUE
Skeletal muscle tissue: Each skeletal muscle is a separate organ composed of thousands of muscle fibers. Connective
tissue surrounds muscle fibers, whole muscles, blood vessels, and nerves.
Muscle fibers: Muscle fibers are muscle cells that compose muscle tissue and are referred to as fibers due to
their elongated shape.
Connective tissue components:
Fascia: Sheet or band of connective tissue that supports and surrounds skeletal muscles.
Superficial fascia: This type of fascia separates skeletal muscle tissue from the skin. It is, actually, the
hypodermis (subcutaneous layer) of the skin and is composed of adipose tissues and areolar connective
tissue. It serves as a pathway for nerves, blood vessels, and lymphatic vessels to enter and exit the
muscle tissue. The adipose tissue of the superficial fascia functions to reduce heat loss from the body
and protects skeletal muscles from physical trauma.
Deep fascia: This type of fascia is composed of dense irregular connective tissue, and it lines the body
wall and limbs, and holds muscles with similar functions together. Deep fascia functions to allow muscles
to move freely.
Epimysium: Outermost layer of the deep fascia composed of dense irregular connective tissue, and it surrounds
the entire muscle.
Perimysium: Connective tissue layer that surrounds 10-100 or more skeletal muscle fibers. It separates the
muscle fibers into bundles called fascicles.
Fascicles: Bundles of skeletal muscle fibers that are covered by perimysium.
Endomysium: Thin sheath of areolar connective tissue that covers each individual muscle fiber within the
fascicles.
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