Anatomy Presentation Ho 5(muscles)
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Muscles
Muscle is one of our 4 tissue types and muscle tissue combined with nerves, blood vessels, and various connective tissues is what makes up those muscle organs that are familiar to us. Muscles are quite complex and as we’ll find out, they are a marvel of
1
Muscle Functions Production of Movement
1.
Movement of body parts and of the environment Movement of blood through the heart and the circulatory vessels. Movement of lymph through the lymphatic vessels Movement of food (and, subsequently, food waste) through the GI tract Movement of bile out of the gallbladder and into the digestive tract Movement of urine through the urinary tract Movement of semen through the male reproductive tract and female reproductive tract Movement of a newborn through the birth canal
2
Muscle Functions Maintenance of posture
•
Muscle contraction is constantly allowing us to remain upright. The muscles of your neck are keeping your head up right now. As you stand, your leg muscles keep you on two feet.
Thermogenesis
2.
Generation of heat. Occurs via shivering – an involuntary contraction of skeletal muscle.
3
Muscle Functions Stabilization of joints
1.
Muscles keep the tendons that cross the joint nice and taut. This does a wonderful job of maintaining the integrity of the joint.
All the things muscles do fall under one of these 4 categories.
4
3 Types of Muscle Tissue
5
Characteristics of Muscle Tissue Excitability
1.
The ability to receive and respond to a stimulus
In skeletal muscle, the stimulus is a neurotransmitter (chemical signal) release by a neuron (nerve cell). In smooth muscle, the stimulus could be a neurotransmitter, a hormone, stretch, ∆pH, ∆Pco2, or ∆Po2. (the symbol ∆ means “a change in”) In cardiac muscle, the stimulus could be a neurotransmitter, a hormone, or stretch.
The response is the generation of an electrical impulse that travels along the plasma membrane of the muscle cell.
6
Characteristics of Muscle Tissue Contractility
1.
The ability to shorten forcibly when adequately stimulated. This is the defining property of muscle tissue.
Extensibility
2.
The ability to be stretched
Elasticity
3.
The ability to recoil and resume original length after being stretched. 7
Skeletal Muscle – the organ
Skeletal muscle organs are dominated by muscle tissue but also contain nervous, vascular and assorted connective tissues. The whole muscle is surrounded by a layer of dense irregular connective tissue known as the epimysium.(epi= ?, mysium=muscle).
8
Epimysium surrounds several bundles known as fascicles. Each fascicle is a bundle of super-long skeletal muscle cells (muscle fibers), surrounded by a layer of dense irregular CT called the perimysium (peri=around). Each muscle cell extends the length of the whole muscle organ and is surrounded by a fine layer of loose connective tissue, the endomysium. The epi-, peri-, and endomysium are all continuous with one another.
Skeletal Muscle – the organ
9
In this photomicrograph, you should notice: the epimysium on the left, the multiple fascicles, the translucent perimysium partitioning them , and the multiple muscle fibers making up the fascicles.
10
Skeletal Muscle – Blood & Nerve Supply
Each skeletal muscle is typically supplied by one nerve, an artery and one or more veins.
What is the function of each of these 3 items?
They all enter/exit via the connective tissue coverings and
11
Skeletal Muscle Attachments
Most span joints and are attached to bones.
The attachment of the muscle to the immoveable bone in a joint is its origin, while the attachment to the moveable bone is its insertion.
12
Muscle attachments may be direct or indirect.
Direct attachments are less common. The epimysium is fused to a periosteum or a perichondrium.
Indirect attachments are typical. The muscle CT extends and forms either a cordlike structure (a tendon) or a sheetlike structure (aponeurosis) which attaches to the periosteum or perichondrium.
13
Skeletal Muscle Microanatomy
Each skeletal muscle cell is known as a skeletal muscle fiber because they are so long.
Their diameter can be up to 100um and their length can be as long as 30cm. They’re so large because a single skeletal muscle cell results from the fusion of hundreds of embryonic precursor cells called myoblasts.
A cell made from the fusion of many others is known as a syncytium.
Each skeletal muscle fiber will have multiple nuclei. Why?
14
Muscle fiber PM is known as sarcolem ma Muscle fiber cytoplasm is known as sarcoplas m Sarcolemma has invaginations that penetrate through the cell called transverse tubules or T tubules. Sarcoplasm has lots of mitochondria (why?), lots of glycogen granules (to provide glucose for energy needs) as well as myofibrils and sarcoplasmic reticuli. 15
Sarcoplasmic Reticulum
Muscle cell version of the smooth endoplasmic reticulum. Functions as a calcium storage depot in muscle cells. Loose network of this membrane bound organelle surrounds all the myofibrils in a muscle fiber. We
16
Myofibrils
Each muscle fiber contains rodlike structures called myofibrils that extend the length of the cell. They are basically long bundles of protein structures called myofilaments and their actions give muscle the ability to contract. The myofilaments are classified as thick filaments and thin filaments.
17
18
Myofilament s
2 types of myofilaments (thick & thin) make up myofibrils. Thick myofilaments are made the protein myosin
A single myosin protein resembles 2 golf clubs whose shafts have been twisted about one another
About 300 of these myosin molecules are joined together to form a single thick filament
19
Each thin filament is made up of 3 different types of protein: actin, tropomyosin, and troponin.
Each thin filament consists of a long helical double strand. This strand is a polymer that resembles a string of beads. Each “bead” is the globular protein actin. On each actin subunit, there is a myosin binding site. Loosely wrapped around the actin helix and covering the myosin binding site is the filamentous protein, tropomyosin. Bound to both the actin and the tropomyosin is a trio of proteins collectively known as troponin.
20
Note the relationship between the thin and thick filaments
21
Myofibrils
Each myofibril is made up 1000’s of repeating individual units known as sarcomeres (pictured below) Each sarcomere is an ordered arrangement of thick and thin filaments. Notice that it has:
regions of thin filaments by themselves (pinkish fibers) a region of thick filaments by themselves (purple fibers) regions of thick filaments and thin filaments overlapping.
22
Sarcomere
The sarcomere is flanked by 2 protein structures known as Z discs. The portion of the sarcomere which contains the thick filament is known as the A band. A stands for anisotropic which is a fancy way of saying that it appears dark under the microscope.
The A band contains a zone of overlap (btwn thick & thin filaments) and an H zone which contains only thick filaments
23
The portion of the sarcomere which does not contain any thick filament is known as the I band. The I band contains only thin filament and is light under the microscope (it is isotropic).
One I band is actually
In the middle of the H zone is a structure called the M line which functions to hold the thick filaments to one another
24
Here we have several different cross sections of a myofibril. Why are they different?
25
Here is a longitudinal section of skeletal muscle. See the multiple nuclei (N) pressed against the side of the muscle fibers. The light I bands and dark A bands are labeled for you. What do you think the F stands for?
26
Each muscle fiber has many Ttubules
T-Tubules and the SR
Typically each myofibril has a branch of a T-tubule encircling it at each A-I junction
At each A-I junction, the SR will expand and form a dilated sac
Each T-tubule will be flanked by a terminal cisterna. This forms a so-called triad consisting of 2 terminal cisternae and one T27 tubule branch.
28
Smooth Muscle
Involuntary, non-striated muscle tissue Occurs within almost every organ, forming sheets, bundles, or sheaths around other tissues. Cardiovascular system:
Smooth muscle in blood vessels regulates blood flow through vital organs. Smooth muscle also helps regulate blood pressure.
Digestive systems:
Rings of smooth muscle, called sphincters, regulate movement along internal passageways. Smooth muscle lining the passageways alternates contraction and relaxation to propel matter through the alimentary canal.
29
Smooth Muscle
Integumentary system:
Respiratory system
Regulates blood flow to the superficial dermis Allows for piloerection Alters the diameter of the airways and changes the resistance to airflow
Urinary system
Sphincters regulate the passage of urine Smooth muscle contractions move urine into and out of the urinary bladder 30
Smooth Muscle
Reproductive system
Males
Allows for movement of sperm along the male reproductive tract. Allows for secretion of the non-cellular components of semen Allows for erection and ejaculation
Females
Assists in the movement of the egg (and of sperm) through the female reproductive tract Plays a large role in childbirth 31
Smooth Muscle
Smooth muscle cells:
Are smaller: 5-10um in diameter and 30-200um in length Are uninucleate: contain 1 centrally placed nucleus Lack any visible striations Lack T-tubules Have a scanty sarcoplasmic reticulum
• Smooth muscle tissue is innervated by the autonomic nervous system unlike skeletal muscle which is innervated by the somatic nervous system (over which you have control) • Only the endomysium is present. Nor perimysium or epimysium.
32
Smooth Muscle
Smooth muscle is always maintaining a normal level of activity – creating muscle tone. Smooth muscle can respond to stimuli by altering this tone in either direction.
Smooth muscle can be inhibited and relax Smooth muscle can be excited and contract
Possible stimuli include neurotransmitters, hormones, ∆pH, ∆ Pco2, ∆Po2, metabolites (such as lactic acid, ADP), or even stretch. 33
Types of Smooth Muscle
Smooth muscle varies widely from organ to organ in terms of:
Fiber arrangement Responsiveness to certain stimuli
How would the types of integral proteins that a smooth muscle cell contained contribute to this?
Broad types of smooth muscle:
Single unit (a.k.a. visceral) Multi unit 34
Single Unit Smooth Muscle
More common Cells contract as a unit because they are all connected by gap junctions - protein complexes that span the PM’s of 2 cells allowing the passage of ions between them, i.e., allowing the depolarization of one to cause the depolarization of another. Some will contract rhythmically due to pacemaker cells that have a spontaneous rate of depolarization. 35
Single Unit Smooth Muscle
Not directly innervated. Diffuse release of neurotransmitters at varicosities (swellings along an axon). Responsive to variety of stimuli including stretch and concentration changes of various chemicals Found in the walls of the digestive tract, urinary bladder, and other organs 36
Multi-Unit Smooth Muscle
Innervated in motor units comparable to those of skeletal muscles No gap junctions. Each fiber is independent of all the others. Responsible to neural & hormonal controls No pacemaker cells Less common Found in large airways to the lungs, large arteries, arrector pili, internal eye muscles (e.g., the muscles that cause dilation of the pupil) Why is good to have the digestive smooth muscle
37
Cardiac Muscle
Striated, involuntary muscle Found in walls of the heart Consists of branching chains of stocky muscle cells. Uni- or binucleate. Has sarcomeres & Ttubules Cardiac muscle cells are joined by structures called intercalated discs – which consist of desmosomes and gap junctions.
Notice the branching and the intercalated disc, indicated by the blue arrow. 38
Muscle is one of our 4 tissue types and muscle tissue combined with nerves, blood vessels, and various connective tissues is what makes up those muscle organs that are familiar to us. Muscles are quite complex and as we’ll find out, they are a marvel of
1
Muscle Functions Production of Movement
1.
Movement of body parts and of the environment Movement of blood through the heart and the circulatory vessels. Movement of lymph through the lymphatic vessels Movement of food (and, subsequently, food waste) through the GI tract Movement of bile out of the gallbladder and into the digestive tract Movement of urine through the urinary tract Movement of semen through the male reproductive tract and female reproductive tract Movement of a newborn through the birth canal
2
Muscle Functions Maintenance of posture
•
Muscle contraction is constantly allowing us to remain upright. The muscles of your neck are keeping your head up right now. As you stand, your leg muscles keep you on two feet.
Thermogenesis
2.
Generation of heat. Occurs via shivering – an involuntary contraction of skeletal muscle.
3
Muscle Functions Stabilization of joints
1.
Muscles keep the tendons that cross the joint nice and taut. This does a wonderful job of maintaining the integrity of the joint.
All the things muscles do fall under one of these 4 categories.
4
3 Types of Muscle Tissue
5
Characteristics of Muscle Tissue Excitability
1.
The ability to receive and respond to a stimulus
In skeletal muscle, the stimulus is a neurotransmitter (chemical signal) release by a neuron (nerve cell). In smooth muscle, the stimulus could be a neurotransmitter, a hormone, stretch, ∆pH, ∆Pco2, or ∆Po2. (the symbol ∆ means “a change in”) In cardiac muscle, the stimulus could be a neurotransmitter, a hormone, or stretch.
The response is the generation of an electrical impulse that travels along the plasma membrane of the muscle cell.
6
Characteristics of Muscle Tissue Contractility
1.
The ability to shorten forcibly when adequately stimulated. This is the defining property of muscle tissue.
Extensibility
2.
The ability to be stretched
Elasticity
3.
The ability to recoil and resume original length after being stretched. 7
Skeletal Muscle – the organ
Skeletal muscle organs are dominated by muscle tissue but also contain nervous, vascular and assorted connective tissues. The whole muscle is surrounded by a layer of dense irregular connective tissue known as the epimysium.(epi= ?, mysium=muscle).
8
Epimysium surrounds several bundles known as fascicles. Each fascicle is a bundle of super-long skeletal muscle cells (muscle fibers), surrounded by a layer of dense irregular CT called the perimysium (peri=around). Each muscle cell extends the length of the whole muscle organ and is surrounded by a fine layer of loose connective tissue, the endomysium. The epi-, peri-, and endomysium are all continuous with one another.
Skeletal Muscle – the organ
9
In this photomicrograph, you should notice: the epimysium on the left, the multiple fascicles, the translucent perimysium partitioning them , and the multiple muscle fibers making up the fascicles.
10
Skeletal Muscle – Blood & Nerve Supply
Each skeletal muscle is typically supplied by one nerve, an artery and one or more veins.
What is the function of each of these 3 items?
They all enter/exit via the connective tissue coverings and
11
Skeletal Muscle Attachments
Most span joints and are attached to bones.
The attachment of the muscle to the immoveable bone in a joint is its origin, while the attachment to the moveable bone is its insertion.
12
Muscle attachments may be direct or indirect.
Direct attachments are less common. The epimysium is fused to a periosteum or a perichondrium.
Indirect attachments are typical. The muscle CT extends and forms either a cordlike structure (a tendon) or a sheetlike structure (aponeurosis) which attaches to the periosteum or perichondrium.
13
Skeletal Muscle Microanatomy
Each skeletal muscle cell is known as a skeletal muscle fiber because they are so long.
Their diameter can be up to 100um and their length can be as long as 30cm. They’re so large because a single skeletal muscle cell results from the fusion of hundreds of embryonic precursor cells called myoblasts.
A cell made from the fusion of many others is known as a syncytium.
Each skeletal muscle fiber will have multiple nuclei. Why?
14
Muscle fiber PM is known as sarcolem ma Muscle fiber cytoplasm is known as sarcoplas m Sarcolemma has invaginations that penetrate through the cell called transverse tubules or T tubules. Sarcoplasm has lots of mitochondria (why?), lots of glycogen granules (to provide glucose for energy needs) as well as myofibrils and sarcoplasmic reticuli. 15
Sarcoplasmic Reticulum
Muscle cell version of the smooth endoplasmic reticulum. Functions as a calcium storage depot in muscle cells. Loose network of this membrane bound organelle surrounds all the myofibrils in a muscle fiber. We
16
Myofibrils
Each muscle fiber contains rodlike structures called myofibrils that extend the length of the cell. They are basically long bundles of protein structures called myofilaments and their actions give muscle the ability to contract. The myofilaments are classified as thick filaments and thin filaments.
17
18
Myofilament s
2 types of myofilaments (thick & thin) make up myofibrils. Thick myofilaments are made the protein myosin
A single myosin protein resembles 2 golf clubs whose shafts have been twisted about one another
About 300 of these myosin molecules are joined together to form a single thick filament
19
Each thin filament is made up of 3 different types of protein: actin, tropomyosin, and troponin.
Each thin filament consists of a long helical double strand. This strand is a polymer that resembles a string of beads. Each “bead” is the globular protein actin. On each actin subunit, there is a myosin binding site. Loosely wrapped around the actin helix and covering the myosin binding site is the filamentous protein, tropomyosin. Bound to both the actin and the tropomyosin is a trio of proteins collectively known as troponin.
20
Note the relationship between the thin and thick filaments
21
Myofibrils
Each myofibril is made up 1000’s of repeating individual units known as sarcomeres (pictured below) Each sarcomere is an ordered arrangement of thick and thin filaments. Notice that it has:
regions of thin filaments by themselves (pinkish fibers) a region of thick filaments by themselves (purple fibers) regions of thick filaments and thin filaments overlapping.
22
Sarcomere
The sarcomere is flanked by 2 protein structures known as Z discs. The portion of the sarcomere which contains the thick filament is known as the A band. A stands for anisotropic which is a fancy way of saying that it appears dark under the microscope.
The A band contains a zone of overlap (btwn thick & thin filaments) and an H zone which contains only thick filaments
23
The portion of the sarcomere which does not contain any thick filament is known as the I band. The I band contains only thin filament and is light under the microscope (it is isotropic).
One I band is actually
In the middle of the H zone is a structure called the M line which functions to hold the thick filaments to one another
24
Here we have several different cross sections of a myofibril. Why are they different?
25
Here is a longitudinal section of skeletal muscle. See the multiple nuclei (N) pressed against the side of the muscle fibers. The light I bands and dark A bands are labeled for you. What do you think the F stands for?
26
Each muscle fiber has many Ttubules
T-Tubules and the SR
Typically each myofibril has a branch of a T-tubule encircling it at each A-I junction
At each A-I junction, the SR will expand and form a dilated sac
Each T-tubule will be flanked by a terminal cisterna. This forms a so-called triad consisting of 2 terminal cisternae and one T27 tubule branch.
28
Smooth Muscle
Involuntary, non-striated muscle tissue Occurs within almost every organ, forming sheets, bundles, or sheaths around other tissues. Cardiovascular system:
Smooth muscle in blood vessels regulates blood flow through vital organs. Smooth muscle also helps regulate blood pressure.
Digestive systems:
Rings of smooth muscle, called sphincters, regulate movement along internal passageways. Smooth muscle lining the passageways alternates contraction and relaxation to propel matter through the alimentary canal.
29
Smooth Muscle
Integumentary system:
Respiratory system
Regulates blood flow to the superficial dermis Allows for piloerection Alters the diameter of the airways and changes the resistance to airflow
Urinary system
Sphincters regulate the passage of urine Smooth muscle contractions move urine into and out of the urinary bladder 30
Smooth Muscle
Reproductive system
Males
Allows for movement of sperm along the male reproductive tract. Allows for secretion of the non-cellular components of semen Allows for erection and ejaculation
Females
Assists in the movement of the egg (and of sperm) through the female reproductive tract Plays a large role in childbirth 31
Smooth Muscle
Smooth muscle cells:
Are smaller: 5-10um in diameter and 30-200um in length Are uninucleate: contain 1 centrally placed nucleus Lack any visible striations Lack T-tubules Have a scanty sarcoplasmic reticulum
• Smooth muscle tissue is innervated by the autonomic nervous system unlike skeletal muscle which is innervated by the somatic nervous system (over which you have control) • Only the endomysium is present. Nor perimysium or epimysium.
32
Smooth Muscle
Smooth muscle is always maintaining a normal level of activity – creating muscle tone. Smooth muscle can respond to stimuli by altering this tone in either direction.
Smooth muscle can be inhibited and relax Smooth muscle can be excited and contract
Possible stimuli include neurotransmitters, hormones, ∆pH, ∆ Pco2, ∆Po2, metabolites (such as lactic acid, ADP), or even stretch. 33
Types of Smooth Muscle
Smooth muscle varies widely from organ to organ in terms of:
Fiber arrangement Responsiveness to certain stimuli
How would the types of integral proteins that a smooth muscle cell contained contribute to this?
Broad types of smooth muscle:
Single unit (a.k.a. visceral) Multi unit 34
Single Unit Smooth Muscle
More common Cells contract as a unit because they are all connected by gap junctions - protein complexes that span the PM’s of 2 cells allowing the passage of ions between them, i.e., allowing the depolarization of one to cause the depolarization of another. Some will contract rhythmically due to pacemaker cells that have a spontaneous rate of depolarization. 35
Single Unit Smooth Muscle
Not directly innervated. Diffuse release of neurotransmitters at varicosities (swellings along an axon). Responsive to variety of stimuli including stretch and concentration changes of various chemicals Found in the walls of the digestive tract, urinary bladder, and other organs 36
Multi-Unit Smooth Muscle
Innervated in motor units comparable to those of skeletal muscles No gap junctions. Each fiber is independent of all the others. Responsible to neural & hormonal controls No pacemaker cells Less common Found in large airways to the lungs, large arteries, arrector pili, internal eye muscles (e.g., the muscles that cause dilation of the pupil) Why is good to have the digestive smooth muscle
37
Cardiac Muscle
Striated, involuntary muscle Found in walls of the heart Consists of branching chains of stocky muscle cells. Uni- or binucleate. Has sarcomeres & Ttubules Cardiac muscle cells are joined by structures called intercalated discs – which consist of desmosomes and gap junctions.
Notice the branching and the intercalated disc, indicated by the blue arrow. 38
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