General Histology and Histotechnique 2012 - 2013 Student made handout Credits to the original owner of the pictures used.

1. General Histology and Histotechnique (1st semester 2012-2013)
MUSCLE TISSUES Similarities of Muscle Tissues
- Cells of muscles: fibers
Myology
Muscle contraction
Functions of muscle movements: - Depends on two types of myofilaments (contractile
proteins)
1. Produce body movements  Actin
Ex. Skeletal muscle – Pull bones
- Muscle movements; walking, running  Myosin
- With the help of joints
- Sarcolemma – plasma membrane
2. Stabilize body positions - Sarcoplasm
- To sit, stand, balance position
3. Regulate organ volume
- Due to smooth muscle
Smooth muscle
Location:
Stomach – for temporary storage
Uterine – Store temporarily the urine
4. Move substances within the body
Ex.
Cardiac muscle - blood will be pumped
Smooth muscle – enzymes, food GIT
Skeletal muscle – substances within the body; produces
Lactic acid.
5. Produce heat
- Body movement – Increases temperature
Properties
Contractility
- To generate the pulling force
- Ability of muscle to contract forcefully
Excitability
- Ability to respond to a certain stimuli to produce
electrical signals SKELETAL MUSCLE
Extensibility - To move the bones of skeleton
- Ability to stretch without being destroyed - It does not consists of single muscle fiber
- It form multinucleated used muscle fiber
Elasticity - Form by diffusion of myoblast
- Able to go back to its original shape/length  Embryonic cells of skeletal
muscle

2. General Histology and Histotechnique (1st semester 2012-2013)
- Striations are present  Dense irregular connective
- Nucleus is found at the Peripheral – at the sides tissue
- Attached to the bones
c. Endomysium
I. Connective Tissue components of skeletal
muscle - 1 bundle of muscle
- Covers the individual muscle fiber
1. Fascia – (Bandage) - Areolar tissue
- Fibrous connective tissue that is deep to the skin - Separate muscle fibers from each others
- Surrounds muscles and other organs of the body.
2 types:
a. Superficial fascia or the subcutaneous layer
- separate muscles from skin
Made up of:
- Areolar connective tissue
- Adipose tissue
Functions:
1. It provides a pathway for nerves and Blood
vessels to enter and exits muscles.
2. Stores most of the triglycerides
3. Serves as good insulating layer; reducing heat
loss – due to Connective tissue
4. Protects muscles from physical trauma
b. Deep fascia
- A dense irregular connective tissue
Functions:
- Lines the body wall and limbs
- Holds muscles together
- Allows free movement of muscles
- Carries Blood vessels, nerves, Lymphatic vessels
- Fills the spaces between muscles
2. Three layers of connective tissue
- Extend from the deep fascia to further protect and
strengthen skeletal muscle
a. Epimysium
- Encircles the whole muscle/covers the muscle Basic features of skeletal muscle
- Dense irregular connective tissue
Nerves and blood vessels
b. Perimysium - Each skeletal muscle is supplied by branches of one
- Encircles bundles of muscles nerve, one artery, one or more veins
 Wrapped by Fascicle - Nerves and vessels branch repeatedly
 10-100 or more muscle; - Smallest nerve branches serve
Individual muscle fibers

3. General Histology and Histotechnique (1st semester 2012-2013)
 Individual muscle fibers
Tissue sheaths – extend to from the tendon - attaches
muscles to bone.
 Neuromuscular junction
- A place in the body where nerves meet a muscle.
- A synapse the motor neuron and the muscle fiber.
Muscle attachments
- Most skeletal muscles run from one bone to
another
b. The sarcolemma of the fiber encloses sarcoplasm
- One bone will move – other bone remains fixed
and myofibrils which are striated
 Origin – less movable part of the bone
 Insertion – more movable attachment c. A sac of sarcoplasm is reticulum wraps around
each myofibril
- Composed of a triad: is a two terminal cisterns and
a T (transverse tubule).
Histological features
Microscopic organization and development
a. Embryonic development
- Fusion of myoblasts into muscle fibers
Myoblast – fused to form the muscle fibers
- After fusion, still with satellite cell, immature
muscle fiber will lose their potential to divide
hence, satellite cell retains it.
- It cannot have any cell division
Satellite cell – forms the muscle
Functions:
- Acts as a reserved population of cells
- Whenever skeletal muscle is in its normal state it is
inactive or quiescent; if it is injured it becomes
active.
- It continues to divide in order to repair and grow
more muscle fibers.
- Repair and maintenance of skeletal muscle

4. General Histology and Histotechnique (1st semester 2012-2013)
- The cytoplasm of muscle fibers
- Contains a substantial amount of glycogen and
myoglobin
 Oxygen binding protein which is red colored
globins and found only in muscle fibers.
3. Myofibrils
- Contractile element of muscles
- Contains overlapping thick and thin filaments
- With prominent striations
Alternating line and dark bands
4. Sarcoplasmic Reticulum
- Fluid-filled system of membranous sacs that
Structure of a skeletal muscle fiber encircles each myofibrils
Function:
- Releases Calcium ions to trigger muscle contraction
5. Sarcomere
- Basic functional unit of myofibril
- Compartment of filaments inside the myofibrils
6. Filaments
- Within the myofibrils of two types:
a. Thin filaments
- 8 nm in diameter
- Protein: Myosin
b. Thick filaments
Sarcoplasmic reticulo  Triad - 16 nm in diameter
- Protein: Actin
1. Sarcolemma
- Muscle fibers plasma membrane which is
7. Mitochondria
perforated with thousands of tiny invagination
- Small and less numerous skeletal muscle fiber
called triad. - For cell respiration
Two terminal sisters: - Powerhouse of the cell
a. Terminal cisterns
- For the synthesis of ATP
- Structure madeup of two strands on either strands
of T tubule. Zones and bands of sarcomere:
b. T tubules
- These are tunnels from the surface towards the
1. A-band – anisotropic
center of each muscle fiber.
- Darker middle portion
Function of Triad:
- Where thick filaments (myosin) are located
To ensure that all parts of the muscle fiber become
- Toward the end of the A band is a zone of overlap:
excited by an action potential virtually simultaneously. where thick and thin filaments lie side by side
2. Sarcoplasm

5. General Histology and Histotechnique (1st semester 2012-2013)
2. I-band – isotropic
- Lighter dense area
- Where thin filaments (actin) extend
- No thick filaments
3. Z-line
- Distinct dark line running down the middle of the I-
band
- Where thin filaments are attached end to end
- Zone of apposition (increase in diameter) of actin
filaments belonging to two neighboring sarcomeres
4. M-line
- So named because it is at the middle of sarcomere
- Where thick filaments are attached end-to-end in
the center of the A-band
- Band of connections between myosin filaments
- Supporting proteins that hold thick filaments
together at the center of H-zone.
5. H-band
- Appears along the middle of A-band, between the
free ends of the thin filaments when muscles are
stretched.
- Zone of myosin filaments only (no overlap with
actin filaments) within the A-band
CARDIAC MUSCLE
II. Cardiac muscle tissue
- Principal muscular tissue in the heart wall
- Shorter in length and larger in diameter
- Exhibit branching which gives an individual fiber and
y-shaped appearance
- Nucleus centrally located

6. General Histology and Histotechnique (1st semester 2012-2013)
Histological parts: - Found in wrap around sheets that form part of the
1. Sarcolemma walls of smaller arteries and veins and hollow
- Plasma membrane surrounding the cardiac muscle viscera such as the stomach, intestines, uterus, and
urinary bladder.
2. Sarcoplasm
- The cytoplasm 2. Multiunit smooth muscle tissue
- Consists of individual fibers, each with its own
3. Mitochondria motor neuron terminals and with few gap junctions
- Larger and more numerous between neighboring fibers
- Found in the walls of large arteries, in airways to
4. T-tubules the lungs, in arrector pili muscle that attaches to
- Wider and less abundant and there is only one T- hair follicles and muscles of iris that adjust pupil
tubule per sarcomere located at the Z-disc. diameter
5. Sarcoplasmic reticulum Histological features:
- Few, has limited intracellular reserved of Calcium
ions. 1. Endomysium
- Surrounds the smooth muscle fiber
6. Myofibril
- Contractile unit 2. Have a single centrally located oval nucleus
7. Sarcomeres 3. Sarcoplasm
- Functional unit, same zones, bands and lines as the - Contains both thick and thin filaments
skeletal muscle.
4. There is no sarcomere
SMOOTH MUSCLE 5. Contains intermediate filaments
6. Have a sarcoplasmic reticulum which is scanty
7. Do not have T-tubules
8. Gap junction in visceral smooth muscles is present
but not in multiunit smooth muscle.
III. Smooth muscle tissue
Two types:
1. Visceral smooth muscle tissue
- Also known as the single unit smooth muscle tissue