Download histology of muscle as a tissue

NAME: - FAGBUYI MOTUNRAYO
DEPT:-NURSING SCIENCE
MATRIC NO:- 14/MHS02/025
HISTOLOGY OF MUSCLE AS A TISSUE
Muscle tissue is composed of cells differentiated for optimal use of the universal cell property
termed contractility. Microfilaments and associated proteins together generate the forces
necessary for cellular contraction, which drives movement within certain organs and the body as
a whole. Nearly all muscle cells are of mesodermal origin and they differentiate mainly by a
gradual process of cell lengthening with simultaneous synthesis of myofibrillar proteins.
Muscle function:
1. contraction for locomotion and skeletal movement
2. contraction for propulsion
3. contraction for pressure regulation
MORPHOLOGICAL CLASSIFICATION
1. Striated
2. Non striated or smooth
FUNCTIONAL CLASSIFICATION
There are two types of muscle based on a functional classification system
1. Voluntary
2. Involuntary.
The Three Types of Muscle
Skeletal Muscle
Skeletal muscle cells are innervated by motor neurons. Contractions move part of the skeleton.
Also called 'voluntary' because usually its contractions are under your control.
It has a stripy appearance, because of the repeating structure of the muscle: there are many
myofibrils (fibers), each one of which is made up of repeating units called muscle sarcomeres.
Cardiac Muscle
Cardiac muscle makes up the muscular walls of the heart (myocardium). It is 'involuntary'
because its contractions are not under your control. However, it has a similar ultrastructural
organisation to skeletal muscle. So, it too has a stripy appearance because of the repeating units
called muscle sarcomeres.
Smooth Muscle
Found in the walls of most blood vessels and tubular organs such as the intestine. It is also
'involuntary'. However, it does NOT have a stripy appearance, because it does not have repeating
sarcomeres. The contractile proteins, myosin and actin are much more randomly arranged than in
skeletal or cardiac muscle
TYPES OF MUSCLE
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
Characteristics of Cardiac muscle
Cardiac muscle shares important characteristics with both skeletal and smooth muscle.
Functionally, cardiac muscle produces strong contractions like skeletal muscle. However, it has
inherent mechanisms to initiate continuous contraction like smooth muscle. The rate and force of
contraction is not subject to voluntary control, but is influenced by the autonomic nervous
system and hormones. 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.
Characteristics of Smooth muscle
Smooth muscle forms the contractile portion of the wall of the digestive tract from the middle
portion of the esophagus to the internal sphincter of the anus. It is found in the walls of the ducts
in the glands associated with the alimentary tract, in the walls of the respiratory passages from
the trachea to the alveolar ducts, and in the urinary and genital ducts. The walls of the arteries,
veins, and large lymph vessels contain smooth muscle as well. 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.
MUSCLE TERMINOLOGY
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
LINES AND BANDS OF MUSCLE HISTOLOGY
The two bands are:
1. Light band or 'I' band.
2. Dark band or 'A' band.
LIGHT BAND OR 'I' BAND
The light band is isotropic in nature. At the point when the captivated light is gone through the
muscle fiber at this range the light beams are refracted at the same edge. Along these lines, this
band is called "I" (isotropic) band.
DARK BAND OR 'A' BAND
The dark band is anisotropic in nature. At the point when the spellbound light is gone through
the muscle fiber at this range, the light beams are refracted at various headings. In an intact
muscle fiber, 'I' band and 'A' band of the adjacent myofibrils are placed side-by-side. It gives the
appearance of characteristics cross striations in the muscle fiber.
I band is divided into two portions by means of a narrow and dark line called 'Z' line or 'Z' disk
(in German Zwischenscheibe=between disks).
A set of proteins crosslinks each myosin filament to its neighbors at the center of the
filament. These proteins make up the M-line.
The thin filaments are attached to a disc-like zone that appears histologically as the Z-line. The
Z-lines contain proteins that bind and stabilize the plus ends of actin filaments. Z-lines also
define the borders of each sarcomere.