Download NAME: GLORY P.A. BRIGGS MATRICULATION NUMER: 14/MHS06

NAME: GLORY P.A. BRIGGS
MATRICULATION NUMER: 14/MHS06/017
DEPARTMENT: MEDICINE AND SURGERY
COURSE: GENERAL HISTOLOGY
COURSE CODE: ANA 203
Histology of Muscle as a Tissue and Its Types
Muscle as defined by the Medical dictionary is a bundle of long
slender cells (muscle fibers) that have the power to contract and hence
produce movement. Also, another definition of muscle at Dictionary.com
states that a muscle is a tissue composed of cells or fibers, the contraction
of which produces movement in the body. It functions in the following ways:
contraction for locomotion and skeletal movement, contraction for
propulsion and contraction for pressure regulation.
The muscle is made up of smaller bundles known as FASCICLES
surrounded by a connective sheath known as PERIMYSIUM and these
fascicles are bundles of individual muscle cells known as MYOFIBER OR
MYOCYTE OR MUSCLE FIBRES, hence the reason for the classification
of muscle as a TISSUE. Each muscle fiber (cell) contains all the organelles
that we find in other cell types although they are given special names using
the prefixes sarco and myo and each of these muscle fibers is surrounded
by a connective sheath known as ENDOMYSIUM. Some of the organelles
include: nucleus which contains genetic information, sarcolemma (plasma
membrane of the muscle cell) which contains special invaginations known
as T tubules, cytosol which is the cytoplasm of the muscle cell, myoblasts
which are the embryonic precursors of skeletal muscle cells e.t.c.
Muscle cells also contain MYOFIBRILS (cylindrical bundles of
contractile proteins) which are composed of individual contractile proteins
called MYOFILAMENTS. They also have an A band which is a dark band
that corresponds to the length of a bundle of myosin filaments and a H
zone in the middle of the A band. The H zone also has an M line in the
middle. There is also an I band which is a light band composed mainly of
actin filaments and a Z line bisecting each I band. They also contain the
SARCOMERE (an area between two Z lines) which is the functional or
contractile unit of muscle.
Muscles as tissues have three major areas: A BELLY OR GASTER,
AN ORIGIN: a tendinous connection of the muscle to a bone, usually the
bone that is stabilized and AN INSERTION: a tendinous connection of the
muscle to a bone, usually the bone to be moved.
Muscle tissue may be classified according to MORPHOLOGICAL
CLASSIFICATION or FUNCTIONAL CLASSIFICATION. Morphologically,
they are classified into striated and non striated or smooth muscle and
functionally, they are classified into voluntary and involuntary muscles.
Also, there are generally three (3) types of muscles in the human body
namely: SKELETAL MUSCLE (striated and voluntary), CARDIAC MUSCLE
(striated and involuntary) and SMOOTH MUSCLE (non striated and
involuntary).
Skeletal muscles are long cylindrical cells with many nuclei per cell. It
has a stripy appearance because of the repeating structure of the muscle.
There are many myofibrils each one of each is made up of repeating units
called muscle sarcomeres, each sarcomere being 2.5mm long. Skeletal
muscles are of different shapes as shown in the diagram below: The
pennate are of three types namely; unipennate, bipennate and
multipennate e.t.c.
Cardiac muscle has a similar ultrastructural organization to skeletal
muscle. They are composed of elongated branched individual cells that lie
parallel to each other with single nucleus.
Smooth muscles are spindled shaped i.e. they are wide in the middle
and narrow to almost a point at both ends. They have a single centrally
located nucleus. Smooth muscles are classified into unitary/single
unit/synctial/visceral and multi unit