Histology Of Muscles

Question 1

What is a Muscle?

Answer 1

Is a contractile tissue that has the capacity of becoming short in response to an
appropriate stimulus. Muscle is the tissue of the body which primarily functions as a
source of power.

Question 2

Functions of Muscle Tissue

?

Answer 2

1. To produce movement by working

with bones, ligaments and tendons. 2. Maintenance of posture. 3. Stabilization of joints. 4. Production of heat.

Question 3

Types of Muscles?

Answer 3

There are three types of muscle:  Cardiac muscle  Smooth muscle  Skeletal muscle

Question 4

List the characteristics and site of Cardiac Muscle?

Answer 4

Site : it is found only in the myocardium of the heart.  Characteristics: 1- Made up of bundles of cells. 2- Each cell has one or two centrally placed nucleus. 3- Cells within a fiber often branch and bind to cells in adjacent fibers to form a network to contract as a one unit. 4- There are intercalated discs between the connecting branches of cells. 5- Striated. 6- Involuntary.

Question 5

List Smooth Muscle characteristics and site ?

Answer 5

Site : walls of hollow organs and blood vessels.  Characteristics: 1- consists of long, spindle-shaped cells with single central nuclei. 2- Its muscle fibers are not striated. 3- Involuntary. 4- In the walls of the blood vessels, the smooth muscle fibers are arranged circularly and serve to modify the caliber of the lumen. 5- In walls of digestive system arranged longitudinally and circularly that help movement of ingested food by a wave of contraction referred to as peristalsis.

Question 6

Skeletal Muscle characteristics and sit?

Answer 6

Site : attached to the skeleton and hence its name (skeletal).
 Characteristics: 1. Composed of muscle cells (fibers), connective tissue, blood vessels and nerves. 2. Consists of multi-nucleated, long and cylindrical muscle fibers . The nuclei of the cells are situated peripherally near the surface of the fiber. 3. The fibers to be smaller diameter in small muscles and larger in large muscles (1 mm- 4 cm in length) 4. Striated. 5. Contracts under Voluntary control.

Question 7

List the Connective Tissue Wrapping of Skeletal Muscle

?

Answer 7

• Endomysium: surrounds the individual muscle fiber/cell. • Perimysium: surrounds the whole bundle of muscle fibers
(fascicle). • Epimysium: surrounds the whole muscle. The epimysium is
covered with fascia.

Question 8

List the Microscopic Structures of Skeletal Muscle Fiber?

Answer 8

1. Sarcolemma – specialized plasma membrane.
2. Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum.
3. Myofibril:
    Bundles of myofilaments separated by sarcoplasmic
   reticulum.  Contains contractile organelles of skeletal muscle.  Extends through the entire length of a muscle fiber.
4. Sarcolemma – specialized plasma membrane.
5. Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum.
6. Myofibril:
    Bundles of myofilaments separated by sarcoplasmic
   reticulum.  Contains contractile organelles of skeletal muscle.  Extends through the entire length of a muscle fiber.
7. Transverse tubules:  They are invaginations of the sarcolemma that penetrate deeply into the muscle fiber around all
   myofibrils.  They permit rapid transmission of the action potential into the cell and play an important role in
   regulating cellular calcium concentration, increasing the efficiency of muscle contraction.

Question 9

Muscle Proteins

Myofibrils are built of 3 kinds of proteins

Answer 9

Contractile proteins “myosin and actin”.
 Regulatory proteins which turns contraction on
& off “troponin and tropomyosin”.
 Structural proteins which provide proper
alignment, elasticity and extensibility “titin,
myomesin, nebulin and dystrophin”.