General Morphology of muscle cells

1. DR S. B PHIRI
Dr S.B Phiri

2. TYPES OF MUSCLES
Dr S.B Phiri

3. Three classification of muscle tissue
According to the gross structure
1. Skeletal muscle
2. Smooth muscle
3. Cardiac muscle
According to the microscopic structure
1. Striated (striped) muscle – skeletal and cardiac muscle
2. Unstriated muscle – smooth muscle
According to the function
1. Voluntary – skeletal muscle
2. Involuntary – smooth and cardiac muscle
The general description
Dr S.B Phiri

4. 
Types of Muscle
 Skeletal
 Attached to bones
 Makes up 40% of body weight
 Responsible for locomotion, facial expressions, posture, respiratory
movements, other types of body movement
 Voluntary in action; controlled by somatic motor neurons
 Smooth
 In the walls of hollow organs, blood vessels, eye, glands, uterus, skin
 Some functions: propel urine, mix food in digestive tract,
dilating/constricting pupils, regulating blood flow,
 In some locations, auto rhythmic
 Controlled involuntarily by endocrine and autonomic nervous systems
 Cardiac
 Heart: major source of movement of blood
 Auto rhythmic
 Controlled involuntarily by endocrine and autonomic nervous systemsDr S.B Phiri

5. Function of Skeletal Muscles
1. Skeletal movement
2. Posture and body position
3. Support of soft tissues
4. Guarding of entrances & exits
5. Maintenance of body temperature
Dr S.B Phiri

6. Nerve and Blood Vessel Supply
Skeletal muscles are rich in nerves
and blood vessels
Chemical communication at Synapsis
(neuromuscular junction)
Synaptic terminal of axon meets motor end
plate of muscle cell
Coiled capillaries are able to adapt to
changes in length of muscle fiber
Fig 9-2
Dr S.B Phiri

7. Microanatomy of Skeletal Muscle Fibers
Some vocabulary:
Skeletal muscle fiber or
myofiber
Sarcolemma
Sarcoplasm
Sarcoplasmic reticulum
Myofibril
Myofilaments
Fig 9-3
Dr S.B Phiri

8. Skeletal Muscle
Structure Composed of muscle cells
(fibers), connective tissue,
blood vessels, nerves
 Fibers are long, cylindrical,
and multinucleated
 Tend to have a smaller
diameter in small muscles
and larger in large muscles.
 Develop from myoblasts;
numbers remain constant
 Striated appearance
 Nuclei are peripherally
located
•Sarcomere = the basic contractile unit of a muscle
Dr S.B Phiri

9.  I-band: this is the region of the thin
filament that does not overlap the thick
filament. (isotropic)
 A- band: corresponds to the entire length
of the thick filament (anisotropic)
 H-zone: the region of the thick filament
that does not overlap the thin filament.
Dr S.B Phiri

10.  Two types of Myofilaments in the sarcomere are
Thin and thick myofilaments.
 Thick myofilaments are made up of myosin. In
muscle there is myosin II, with two globular
heads and tail.
 Thin myofilaments are made up of Actin,
tropomyosin and troponin
Dr S.B Phiri

11. Dr S.B Phiri

12. Dr S.B Phiri

13. Sarcotubular System - Triad
 The muscle fibrils are surrounded by vesicles and
tubules.
 These structures/membranes form the sarcotubular
system, which is made up of a T system and a
sarcoplasmic reticulum.
 The T system of transverse tubules, which is
continuous with the sarcolemma of the muscle fiber,
forms a grid perforated by the individual muscle
fibrils.
 The space between the two layers of the T system is
an extension of the extracellular space.
Dr S.B Phiri

14. RECEPTORS: dihydropyridine receptors (DHPR)
and ryanodine (RyR)
Dr S.B Phiri

15. MUSCLE SPINDLES AND GOLGI TENDON ORGANS
15

16. Thank you
Dr S.B Phiri