1) Skeletal muscle: Voluntary<ul><li>Elongated or tubular.</li><li>Have multiple nuclei. Nuclei are located on the periphery of the cell.</li><li>Striated, i.e, have alternating pattern of light and darks bands.</li></ul> 2) Cardiac muscle: Involuntary<ul><li>Not as long as skeletal muscles. Are often branched.</li><li>Can be mononucleated or binucleated. In both cases nuclei are placed centrally.</li><li>Have striations like that of skeletal.</li><li>Also display Intercalated Discs & Oblique Bridges.</li></ul>3) Smooth muscle: Involuntary<ul><li>Spindle shaped (tapering ends)</li><li>Uninucleated & it is centrally located.</li><li>No striations though they have same contractile proteins.</li></ul>

Types of Muscles- Structures (Simplified)

<html>

<body>

<div>

Histology of muscle

 <o:p></o:p>

Muscle function:

                1.
contraction for locomotion and skeletal movement

                2.
contraction for propulsion

3. contraction for pressure
regulation

 <o:p></o:p>

Muscle classification: muscle tissue may be classified
according to a morphological classification or a functional classification.

 <o:p></o:p>

                Morphological
classification (based on structure)

 <o:p></o:p>

There are two types of muscle based
on the morphological classification system

 <o:p></o:p>

1. Striated

2. Non striated or smooth.

 <o:p></o:p>

                Functional
classification

 <o:p></o:p>

There are two types of muscle based
on a functional classification system

 <o:p></o:p>

1. 
Voluntary

2. 
Involuntary.

 <o:p></o:p>

Types of muscle: there are generally considered to be three
types of muscle in the human body.

 <o:p></o:p>

                Skeletal
muscle: which is striated and voluntary

                Cardiac
muscle: which is striated and involuntary

                Smooth
muscle: which is non striated and involuntary

 <o:p></o:p>

Characteristics of skeletal muscle

 <o:p></o:p>

Skeletal muscle cells are elongated
or tubular. They have multiple nuclei and these nuclei are located on the
periphery of the cell. Skeletal muscle is striated. That is, it has an
alternating pattern of light and darks bands that will be described later.

 <o:p></o:p>

<img src="./Histology%20of%20musclefor%20web_files/image002.jpg"/>

 <o:p></o:p>

Characteristics of Cardiac muscle

 <o:p></o:p>

Cardiac muscle cells are not as
long as skeletal muscles cells and often are branched cells. Cardiac muscle
cells may be mononucleated or binucleated. In either case the nuclei are
located centrally in the cell. Cardiac muscle is also striated. In addition
cardiac muscle contains intercalated discs.

<img src="./Histology%20of%20musclefor%20web_files/image004.jpg"/>

 <o:p></o:p>

Characteristics of Smooth muscle

 <o:p></o:p>

Smooth muscle cell are described as
spindle shaped. That is they are wide in the middle and narrow to almost a
point at both ends. Smooth muscle cells have a single centrally located
nucleus. Smooth muscle cells do not have visible striations although they do
contain the same contractile proteins as skeletal and cardiac muscle, these
proteins are just laid out in a different pattern.

<img src="./Histology%20of%20musclefor%20web_files/image006.jpg"/>

 <o:p></o:p>

For the purposes of this class we will focus mainly on
skeletal muscle.

 <o:p></o:p>

Shapes of skeletal muscles:

 <o:p></o:p>

1. 
Parallel or fusiform: as their name implies their fibers run parallel to
each other.  These muscles contract over
a great distance and usually have good endurance but are not very strong.  Examples: Sartorius muscle and rectus
abdominus muscle.

 <o:p></o:p>

2. 
Convergent: the muscle fibers converge on the insertion to maximize the
force of muscle contraction.  Examples:
Deltoideus muscle and Pectoralis Major muscle.

 <o:p></o:p>

 <o:p></o:p>

<img src="./Histology%20of%20musclefor%20web_files/image007.jpg"/>

 <o:p></o:p>

3. 
pennate: many fibers per unit area. 
These types of muscles are strong but they tie or quickly.  There are three types of pennate muscle.

                                unipennate

                                bipennate

                                multipennete

 <o:p></o:p>

4. 
Circular: the muscle fibers surrounded opening to act as a
sphincter.  Examples: Orbicularis oris
and Orbicularis oculi muscles.

 <o:p></o:p>

5. 
fusiform: some texts classify parallel muscles that are slightly wider
in their middle (spindle shaped) as fusiform. This term will not be used in
this course.

 <o:p></o:p>

Muscle terminology

 <o:p></o:p>

                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

 <o:p></o:p>

<img src="./Histology%20of%20musclefor%20web_files/image009.jpg"/>

 <o:p></o:p>

For the purposes of this class we will focus mainly on
skeletal muscle.

 <o:p></o:p>

Muscles have three major areas:

 <o:p></o:p>

1. a belly or Gaster

2. an origin: a tendinous
connection of the muscle to a bone, usually the bone that is stabilized.

3. an insertion: a tendinous
connection of the muscle to a bone, usually the bone to be moved.

 <o:p></o:p>

Skeletal muscle is designed as a bundle within a bundle
arrangement.  We will start with a whole
muscle and then work our way down to the microscopic level of the muscle

 <o:p></o:p>

The entire muscle is surrounded by a connective tissue
called the epimysium.

<img src="./Histology%20of%20musclefor%20web_files/image011.jpg"/>

The muscle is made up of smaller bundles known as fascicles.
Fascicles are actually bundles of individual muscle cells (myofibers or
myocytes). These bundles are surrounded by a connective tissue sheath called
the perimysium.

 <o:p></o:p>

Each fascicle is made up of several muscle cells known as
myocytes. They may also be called myofibers or muscle fibers. Each muscle cell
is surrounded by a connective tissue sheath known as the endomysium. This
sheath is very important in the physiology of muscle contraction because it
electrically insulates the individual muscle cells from each other.

<img src="./Histology%20of%20musclefor%20web_files/image013.jpg"/>

At the ends of the muscle all of the connective tissue
sheaths (epimysium, perimysium, and endomysium) converge to form a tendon which
will connect the muscle to its attachment site.

 <o:p></o:p>

Each muscle fiber (muscle cell) contains all of the
organelles that we find in other cell types.

Although these organelles are the same as in other cells
they are given special names. Note that the prefixes sarco and myo both refer
to muscle. Therefore if you see a word with either of these prefixes you should
immediately think MUSCLE.

<img src="./Histology%20of%20musclefor%20web_files/image014.jpg"/>

The nucleus contains the genetic material of the muscle
cell.

 <o:p></o:p>

The sarcolemma is the name given to the plasma membrane of
the muscle cell. There are specialized invaginations of the sarcolemma that run
transversely across the cell. These invaginations are known as T tubules (short
for transverse tubules). The T tubules are essential for carrying the
depolarization brought to the cell by a motor nerve impulse down into the
muscle cell where it can have an affect on the terminal cisternae. We will
cover more about this in the unit on the physiology of muscle contraction.

 <o:p></o:p>

The cytosol is the cytoplasm of the muscle cell.

 <o:p></o:p>

The sarcoplasmic reticulum is the endoplasmic reticulum of
the muscle cell. There are sac-like regions of the sarcoplasmic reticulum known
as terminal cisternae. The terminal cisternae act as calcium storage sites. The
calcium ions stored in the terminal cisternae are essential in muscle
contraction. We will cover more about this in the unit on the physiology of
muscle contraction. NOTE: this is not calcium storage for use in general body
physiology as we would see with bone tissue, but rather is calcium storage for
muscle contraction.

 <o:p></o:p>

In skeletal muscle two terminal cisternae are associated
with a T tubule to form a structure known as a triad. This differs from cardiac
muscle where one terminal cisternae associates with one T tubule to form a
diad.

 <o:p></o:p>

Mitochondria are sites of energy production (ATP synthesis)
in the muscle cell as in all other cells of the body, except for mature red
blood cells.

 <o:p></o:p>

A myofibril is a cylindrical bundle of contractile proteins
found within the muscle cell. Note that there are several myofibrils within
each muscle cell. It is the arrangement of the contractile proteins within the
myofibril that cause the striated appearance of skeletal and cardiac muscle.

 <o:p></o:p>

Myofibrils are composed of individual contractile proteins
called myofillaments. These myofilaments are generally divided into thick and
thin myofilaments.

 <o:p></o:p>

The thin myofilaments are composed mainly of a protein known
as actin. Actin filaments are anchored into the z-line of a sarcomere.

 <o:p></o:p>

The thick myofilaments are composed mainly of the protein
myosin.

 <o:p></o:p>

It is the orderly overlapping of the actin and myosin filaments
that give cardiac and skeletal muscle their striated appearance (light and dark
bands).

 <o:p></o:p>

The A band is the dark band and corresponds to the length of
a bundle of myosin filaments. Because muscle contraction is a sliding of the
myofilaments past each other we do not see any of the myofilaments actually
shorten. However the width of the banding patterns change as the degree of
overlap changes. Because the A band corresponds to the length of the myosin
filaments, and these filaments do not shorten, the width of the A band also
does not shorten.

 <o:p></o:p>

The light bands are known as I bands. The I bands are
composed mainly of actin filaments. Each I band is bisected by a protein disc
known as the Z-line. Actin filaments are anchored into the Z-line. During
muscle contraction the actin filaments slide over the myosin filaments which
results in a shortening of the I band.

 <o:p></o:p>

In the middle of the A band is a somewhat lighter area known
as the H zone. This zone corresponds to the area where we have myosin not
overlapped by actin (the area between the thin filaments). During muscle
contraction the actin sliding over the myosin encroaches into this area so that
the H zone shortens. In the middle of the H zone we see a dark band known as
the M line. The M line is comprised of protein fibers that function to anchor
the myosin filaments.

 <o:p></o:p>

The area between two Z lines is known as a sarcomere. The
sarcomere is the functional or contractile unit of muscle.

 <o:p></o:p>

To recap, a whole muscle if made up of many smaller bundles
known as fascicles. Each fascicle is made up of many muscle cells (myofibers).
Myofibers contain cylindrical bundles of myofibrils which in turn contain many
smaller bundles of myofilaments.

 <o:p></o:p>

Muscles contract when they receive a motor impulse from a
motor nerve. These nerve impulses serve only a limited number of muscle fibers.
The muscle fibers served by a single motor neuron make up a structure known as
a motor unit. Motor units allow for selective contraction of muscle fibers so
that we may control the strength and extent of muscle contraction. Without
motor units a nerve impulse to the muscle would result in the entire muscle
contracting to its full extent. That would make every motion that we make an
“all or none” motion. This type of movement would make life nearly impossible.

<img src="./Histology%20of%20musclefor%20web_files/image015.jpg"/>

 <o:p></o:p>

Note that this diagram shows a neuromuscular junction of one
motor neuron with one muscle fiber. In a motor unit the motor neuron branches
to form neuromuscular junctions with several muscle fibers. To repeat, a motor
neuron and all of the muscle fibers it supplies is called a MOTOR UNIT.

</div>




</body></html>

personaldevelopment

Personal Development

communication

Communication

1. contraction for locomotion and skeletal movement

2. contraction for propulsion

3. contraction for pressure regulation

Muscle classification: muscle tissue may be classified according to a morphological classification or a functional classification.

Morphological classification (based on structure)

There are two types of muscle based on the morphological classification system

Functional classification

There are two types of muscle based on a functional classification system

Types of muscle: there are generally considered to be three types of muscle in the human body.

Skeletal muscle: which is striated and voluntary

Cardiac muscle: which is striated and involuntary

Smooth muscle: which is non striated and involuntary

Characteristics of skeletal muscle

Skeletal muscle cells are elongated or tubular. They have multiple nuclei and these nuclei are located on the periphery of the cell. Skeletal muscle is striated. That is, it has an alternating pattern of light and darks bands that will be described later.

Characteristics of Cardiac muscle

Cardiac muscle cells are not as long as skeletal muscles cells and often are branched cells. Cardiac muscle cells may be mononucleated or binucleated. In either case the nuclei are located centrally in the cell. Cardiac muscle is also striated. In addition cardiac muscle contains intercalated discs.

Smooth muscle cell are described as spindle shaped. That is they are wide in the middle and narrow to almost a point at both ends. Smooth muscle cells have a single centrally located nucleus. Smooth muscle cells do not have visible striations although they do contain the same contractile proteins as skeletal and cardiac muscle, these proteins are just laid out in a different pattern.

For the purposes of this class we will focus mainly on skeletal muscle.

1. Parallel or fusiform: as their name implies their fibers run parallel to each other. These muscles contract over a great distance and usually have good endurance but are not very strong. Examples: Sartorius muscle and rectus abdominus muscle.

2. Convergent: the muscle fibers converge on the insertion to maximize the force of muscle contraction. Examples: Deltoideus muscle and Pectoralis Major muscle.

3. pennate: many fibers per unit area. These types of muscles are strong but they tie or quickly. There are three types of pennate muscle.

4. Circular: the muscle fibers surrounded opening to act as a sphincter. Examples: Orbicularis oris and Orbicularis oculi muscles.

5. fusiform: some texts classify parallel muscles that are slightly wider in their middle (spindle shaped) as fusiform. This term will not be used in this course.

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

2. an origin: a tendinous connection of the muscle to a bone, usually the bone that is stabilized.

3. an insertion: a tendinous connection of the muscle to a bone, usually the bone to be moved.

Skeletal muscle is designed as a bundle within a bundle arrangement. We will start with a whole muscle and then work our way down to the microscopic level of the muscle

The entire muscle is surrounded by a connective tissue called the epimysium.

The muscle is made up of smaller bundles known as fascicles. Fascicles are actually bundles of individual muscle cells (myofibers or myocytes). These bundles are surrounded by a connective tissue sheath called the perimysium.

Each fascicle is made up of several muscle cells known as myocytes. They may also be called myofibers or muscle fibers. Each muscle cell is surrounded by a connective tissue sheath known as the endomysium. This sheath is very important in the physiology of muscle contraction because it electrically insulates the individual muscle cells from each other.

At the ends of the muscle all of the connective tissue sheaths (epimysium, perimysium, and endomysium) converge to form a tendon which will connect the muscle to its attachment site.

Each muscle fiber (muscle cell) contains all of the organelles that we find in other cell types.

Although these organelles are the same as in other cells they are given special names. Note that the prefixes sarco and myo both refer to muscle. Therefore if you see a word with either of these prefixes you should immediately think MUSCLE.

The nucleus contains the genetic material of the muscle cell.

The sarcolemma is the name given to the plasma membrane of the muscle cell. There are specialized invaginations of the sarcolemma that run transversely across the cell. These invaginations are known as T tubules (short for transverse tubules). The T tubules are essential for carrying the depolarization brought to the cell by a motor nerve impulse down into the muscle cell where it can have an affect on the terminal cisternae. We will cover more about this in the unit on the physiology of muscle contraction.

Histology of muscle

Types of Muscles- Structures (Simplified)

Vaidehi Watwe's ideas are part of this journey:

Related collections

Similar ideas