Download Structure of Muscle Tissue

Structure of Muscle Tissue
and Associated Tissues
Tissue
Tissue combinations from muscle, fat
and bone which are the gross
components of carcasses, and their
properties and proportions are
responsible for quality and leanness of
meat.
Muscle tissue
Skeletal muscles constitute 35-65 % of
carcass weight of meat animals.
Smooth muscle - blood vessels
Cardiac muscle- is confined solely to
the heart
Skeletal muscle
Are organs of the muscular system
There are more than 600 muscle in the
animal body.
Vary widely in shape, size and action.
The structure of muscle will be showed
in Figure
Muscle fiber
Is the highly specialized cell.
Constitute 75-92% of muscle volume
Blood vessels, nerve fibers and
extracellular fluid make up the other
volume.
Skeletal muscle fiber
Are long , unbranched, threadlike cells
which taper slightly at both ends.
Vary considerably in diameter.
Ranged from 10um->100 um within the
same species or the same
muscle.(micrometer=one millionth of a
meter)
Sarcolemma
Surround the muscle fiber
Is composed of protein and lipid
material and it relatively elastic (adjust
very well during contraction, relaxation
and stretching).
A network of tubules called transverse
tubules –T system or T tubules is
circumferential on the surface.
Myofibrils
Are long , thin, cylindrical rods, usually
1-2 um in diameter.
A muscle fibers of meat animals with
diameters of 50um have at least 1000
and could have as many as 2000 or
more myofibrils.
Sarcomere
In myofibrillar cross-section, a well
ordered array of dots that have two
distinct size. ( thin and thick filaments).
Area of different density are visible
within light and dark bands of myofibrils.
The unit of the myofibril between two
adjacent Z disks- a sarcomere
Sarcomere
includes both an A band and the two
half T bands located on either side of
the A band.
Is the repeating structural unit of the
myofibril.
Is also the basic unit in which events of
the muscle’s contraction-relaxation
cycle occur.
myofilament
Divided into thick and thin filaments.
Thick filaments – 14-16 nm
( nanometer, one-billionth of a meter) in
diameter and 1.5 um long, constitute the
A band of the sarcomere ; referred as
myosin filament. Some of which are
located in the M line .
myofilament
Thin filaments: are about 6-8 nm in
diameter , 1.0 um long; on either side of
the Z disk; they also constitute the I
band and extend beyond the I band
into the A band, referred as actin
filaments
The orderly arrangement
H zone : Only thick filaments (myosin)
are present.
A band : thin and thick filaments
overlap , show six thin filaments
surrounding each thick filament
I band : only thin filaments (actin)are
present.
Proteins of the myofilaments
The protein actin and myosin :65% of
the protein of the myofibril.
The remaining fraction consists of
regulatory (tropomyosin and troponin)
and cyto-skeletal proteins ( c-proteinencircle the myosin filament , desminencircle the Z disks).
Actin or thin filament
20% of the myofibrillar protein
A globular shaped molecule , 5.5 nm in
diameter.Referred to as G-actin
F actin is linked by G-actin
The actin filament : two strands of Factin are spirally coiled around one
another to form a super helix
Myosin or thick filament
Is a fibrous protein.
45% of myofibrillar protein.
Is an elongated rod shape, with a
thickened portion at one end- referred to
as the head region. Another is the long
thin portion –is called the rod or tail
portion, between two is called the neck.
Sarcoplasmic Reticulum and T tubules
Sarcoplasmic Reticulum (SR)- is a
membraneous system of tubules and
cisternae (reservoirs for Ca+2). Longitudinal
tubules and terminal cisternae
Transverse tubules –T system or T tubules is
circumferential on the surface.
Usually discussed together, are two separate
and distinct membrane systems.
Connective tissue
Connects and holds verious parts of the
body together.
Are distributed throughout the body.
Such as blood vessel , tendon, nerve
trunk. Or skin , hide
Fat storage cells are located within a
specialized type of connective tissue –
adipose tissue.
Connective tissue
Ground substance –containing soluble
glycoprotein(carbohydrate +protein),
such as proteoglycans or
glycosaminoglycans (hyaluronic acid –
can be found in joints and chondroitin
sulfates- can be found in cartilage,
tendons and adult bone)
Connective tissue
Extracellular fibers: reticulin, collagen
and elastin.
Collagen is the most abundant protein
in the animal body and significantly
influences meat tenderness. Constitutes
20-25% of total body protein; is a
glycoprotein.
Collagen
Glycine is the most abundant amino
acid in collagen and comprises about
1/3 of the total amino acids.
Hydroxyproline, and proline account for
another 1/3 of its amino acid content.
Hydroxyproline is a relatively constant
component of collagen (13-14 %).
Collagen
In young animal , cross linkages are
fewer in number and more easily broken.
Collagen is more soluble in young
animals and becomes less soluble as
the animal ages.
Elastin
Is a much less abundant connective
tissue protein than collagen.
Is a rather rubbery protein that is
present throughout the body in
ligaments and arterial walls
Is highly resistant to digestive enzymes
and no method of cookery has any
appreciable solubilizing effect on it.
Reticulin
Is composed of small fibers that form
delicate networks around cells, blood
vessels, neural structures which hold
them in place.
Are numerically overwhelmed by
collagenous fibers.
Adipose tissue
Accumulation of numerous adipocytes.
Also know as fat.
Contains two types of adipose tissue ;
white and brown fat. White type is the
most in meat animal . Brown type is
present in all of them at birth, especially
around the kidneys.
Muscle and Fiber type
Muscle are usually classified as red, or white,
based principally on their color intensity,
which is attributable to the proportion of red
and white fibers they contain.
Few muscle are composed of all red or white
fibers.
Most are mixtures of red and white fibers
For example, red muscle are those with
higher proportion of red fibers than found in
white muscle.
Muscle and Fiber type
Such as leg muscle and breast muscle
of chicken or turkey.
Different color also can be showed in
various parts in a meat animal.
The structural, functional and metabolic
characteristics of red , intermediate and
white muscle fibers are different.
The chemical composition of
meat
Moisture :65-80%
Protein:16-22%
Lipid: 1.5-13%
Carbohydrates: 0.5-1.5%
Mineral: 1.0-1.2%
The end of this chapter