Download types of muscle tissue

NAME: ADEBAYO ZULAIHA ADERONKE
DEPARTMENT; PHYSIOLOGY
MATRIC NO; 14/MHS01/003
COURSE; ANA 203 (HISTOLOGY OF BASIC TISSUES)
LEVEL; 200
ASSIGNMENT
Write an essay on the histology of muscle as a tissue and state its types.
ANSWER
HISTOLOGY OF THE MUSCLE TISSUE
Muscle is a soft tissue found in most animals. It is characterized
based on its functional property, which is the ability of its cells to
contract. The Muscle tissue is the fourth basic tissue type. All muscle
tissues are derived from the mesodermal layer of embryonic germ cells
in a process called myogenesis and they differentiate by a gradual
process of cell lengthening with abundant synthesis of the myofibrillar
proteins, actin and myosin. They are primarily responsible for
maintaining and changing posture, locomotion, as well as movement of
internal organs, such as the contraction of the heart and the movement of
food through the digestive system via peristalsis.
Muscle cells are generally refered to as ‘muscle fibers’ and are
arranged in parallel arrays allowing them to function together
effectively. Muscles are predominantly powered by the oxidation of fats
and carbohydrates, but anaerobic chemical reactions are also used,
particularly by fast twitch fibers. The term muscle is derived from the
latin word musculus meaning little mouse perhaps because of the shape
of certain muscles or because contracting muscles look like mice
moving under the skin.
TYPES OF MUSCLE TISSUE
There are three types of muscle tissue which are distinguished on the
basis of morphologic and functional characteristics, with the structure of
each adapted to its physiologic role. T
1. SKELETAL MUSCLE
This type of muscle constitutes the muscle that is attached to the
skeleton and controls motor movements and posture. It is a striated
muscle. Skeletal muscle fibers are a multinucleated syncytium formed
by the fusion of individual small muscle cells or myoblasts, during
development. They are filled with myofibrils of which are made up of
myofilaments myosin (thick filament) and actin (thin filament).
Individual contractile units are called sacromeres. A myofibril consists
of many sacromeres. Longitudinal sections of skeletal muscle contains
alternating pattern of dark and light bands called A(anisotropic) and
I(isotropic) band. The I band is bisected by a dense zone called the Z
line to which the thin filaments of the I band are attached. The nuclei are
located peripherally, immediately under the plasma. The thickness of
each fiber is uniform throughout its length and they do not branch out.
Skeletal/ voluntary muscle is divided into two;
a) Slow twitch
These muscles are also called red muscles. They are dense in capillaries
and rich in mitochondria and myoglobin, giving the muscle its red
colour. It can carry more oxygen and sustain aerobic activity using fats
or carbohydrates as fuel. They contract for a long period of time but with
little force.
b) Fast twitch
They contract quickly and powerfully but fatigue very rapidly,
sustaining only short, anaerobic bursts of activities before muscle
contraction becomes painful. They contribute most to the muscle
strength and have greater potential for increase in mass. Fast twitch
muscle/ Type II have three subtypes IIa, IIx, IIb that vary in contractile
speed and force generated.
2. CARDIAC MUSCLE
This is the type of muscle found in the heart and at the base of the
venae cava as they enter into the heart. Cardiac muscle also exhibit
striation due to the presence of actin and myosin filaments arranged into
sacromeres. Cardiac muscle cells have only one or two nuclei that are
centrally located. They are joined to one another in a linear array. The
boundary between two cells abutting each other is called an intercalated
disc. Cardiac muscle fibers branch and anastomose with one another.
Although made up of individual fibers, heart acts as a functional
syncytium during contraction for the efficient pumping of blood.
3. SMOOTH MUSCLE
This is the intrinsic muscle of the internal organs and blood
vessels. It is also found in the iris and ciliary body of the eye and
associated with hair follicles. No striations are present due to the
different arrangement of actin and myosin filaments. Smooth muscles
are specialised for slow, prolonged contraction. Smooth muscle fibers
are generally arranged in bundles or sheets. Each fiber is fusiform in
shape with tapered end. The single nucleus is located in the central part
of the fiber of which has a cork screw shape in longitudinal section due
to contraction of the muscle fiber during fixation. Fibers do not
branch.They range enormously in size, from 20 to 500mm. Smooth
muscle fibers lie over one another in a staggered fashion. Smooth
muscle has the ability to secrete connective tissue matrix.