Download Cardiac Muscle

ADIZUA IJEOMA EMMANUELLA
MEDICINE & SURGERY
14/MHS01/009
HISTOLOGY ASSIGNMENT
HISTOLOGY OF THE MUSCLE TISSUE AND ITS TYPES
Muscle tissue is a soft tissue that composes muscles in animal bodies, and gives rise to muscles'
ability to contract. This is opposed to other components or tissues in muscle such as tendons or
perimysium. It is formed during embryonic development through a process known as
myogenesis.
Muscle tissue varies with function and location in the body. In mammals the three types are:
skeletal or striated muscle; smooth or non-striated muscle; and cardiac muscle, which is
sometimes known as semi-striated.[citation needed] Smooth and cardiac muscle contracts
involuntarily, without conscious intervention. These muscle types may be activated both
through interaction of the central nervous system as well as by receiving innervation from
peripheral plexus or endocrine (hormonal) activation. Striated or skeletal muscle only contracts
voluntarily, upon influence of the central nervous system. Reflexes are a form of non-conscious
activation of skeletal muscles, but nonetheless arise through activation of the central nervous
system, albeit not engaging cortical structures until after the contraction has occurred.
The different muscle types vary in their response to neurotransmitters and endocrine
substances such as acetyl-choline, noradrenalin, adrenalin, nitric oxide and among others
depending on muscle type and the exact location of the muscle.
Sub-categorization of muscle tissue is also possible, depending on among other things the
content of myoglobin, mitochondria, myosin ATPase etc.
STRUCTURE OF THE MUSCLE TISSUE
Muscle (myocytes) are elongated cells ranging from several millimetres to about 10 centimetres
in length and from 10 to 100 micrometres in width. These cells are joined together in tissues
that may be either striated or smooth, depending on the presence or absence, respectively, of
organized, regularly repeated arrangements of myofibrillar contractile proteins called
myofilaments. Striated muscle is Structure
further classified as either skeletal or cardiac muscle. Striated muscle is typically subject to
conscious control, while smooth muscle is not. Thus, muscle tissue can be described as being
one of three different types:
TYPES OF MUSCLE TISSUE

Skeletal muscle
It is striated in structure and under voluntary control, is anchored by tendons (or by
aponeuroses at a few places) to bone and is used to effect skeletal movement such as
locomotion and to maintain posture. An average adult male is made up of 42% of skeletal
muscle and an average adult female is made up of 36% (as a percentage of body mass).[3] It
also has striations unlike smooth muscle.
Types of Skeletal Muscle
Skeletal muscle is further divided into several subtypes:
Type I, slow oxidative, slow twitch, or "red" muscle is dense with capillaries and is rich in
mitochondria and myoglobin, giving the muscle tissue its characteristic red color. It can carry
more oxygen and sustain aerobic activity. Type I muscle fiber are sometimes broken down into
Type I and Type Ic categories, as a result of recent research. Type II, fast twitch muscle, has
three major kinds that are, in order of increasing contractile speed: Type IIa, which, like slow
muscle, is aerobic, rich in mitochondria and capillaries and appears red when deoxygenated.
Type IIx (also known as type IId), which is less dense in mitochondria and myoglobin. This is the
fastest muscle type in humans. It can contract more quickly and with a greater amount of force
than oxidative muscle, but can sustain only short, anaerobic bursts of activity before muscle
contraction becomes painful (often incorrectly attributed to a build-up of lactic acid). N.B. in
some books and articles this muscle in humans was, confusingly, called type IIB. Type IIb, which
is anaerobic, glycolytic, "white" muscle that is even less dense in mitochondria and myoglobin.
In small animals like rodents this is the major fast muscle type, explaining the pale color of their
flesh.
 Smooth Muscle
Smooth muscle, neither striated in structure nor under voluntary control, is found within the
walls of organs and structures such as the esophagus, stomach, intestines, bronchi, uterus,
urethra, bladder, blood vessels, and the arrector pili in the skin (in which it controls erection of
body hair). In vertebrates, there is a third muscle tissue recognized:
Types of Smooth Muscle
The smooth muscle fibres taper at both ends and do not show striation. Cell junctions hold
them together and they are bundled together in a connective tissue sheath. The wall of internal
organs such as the blood vessels, stomach and intestine contains this type of muscle tissue.
Smooth muscles are involuntary
 Cardiac Muscle
Cardiac muscle (myocardium), found only in the heart, is a striated muscle similar in structure
to skeletal muscle but not subject to voluntary control. Cardiac and skeletal muscles are
"striated" in that they contain sarcomeres and are packed into highly regular arrangements of
bundles; smooth muscle has neither. While skeletal muscles are arranged in regular, parallel
bundles, cardiac muscle connects at branching, irregular angles (called intercalated discs).
Striated muscle contracts and relaxes in short, intense bursts, whereas smooth muscle sustains
longer or even near-permanent contractions.
Types of Cardiac Muscle
Cardiac muscle cells are joined end to end. The resulting fibers are branched and
interconnected in complex networks. Each cell has a single nucleus. At its end, where it touches
another cell, there is a specialized intercellular junction called an intercalated disc, which occurs
only in cardiac tissue. Cardiac muscle is controlled involuntarily for pumping blood through the
heart chambers into the blood vessels.
Functions of the Muscle Tissues
 Skeletal muscle
1. They carry out movements of the body.
2. They support the body.
3. They maintain the posture of the body.
 Smooth muscle
It is responsible for the contractility of hollow organs, such as blood vessels, the gastrointestinal
tract, and the bladder.
 Cardiac muscle
Cardiac muscle is the muscle of the heart. It is self-contracting, autonomically regulated and
must continue to contract in rhythmic fashion for the whole life of the organism. Hence it has
special features.