MUSCULAR

RT211 | Muscular System

Classification of Muscles

1. Skeletal Muscles

   • Usually attached to bones.

   • Striated and voluntary.

2. Visceral Muscles

   • Located in the walls of some organs.

   • Nonstriated and involuntary.

3. Cardiac Muscles

   • Found in the heart (myocardium).

   • Striated and involuntary.

Characteristics of Skeletal Muscles

• The red lean meat of the body makes up almost half of the body weight and is usually controlled by the cerebrum.

1. Muscle Fibers

   • Definition: Muscle cells.

2. Fibrils or Myofibrils

   • Definition: Many fine threadlike structures.

3. Fascia

   • Definition: A layer of connective tissue.

Attachments of Skeletal Muscles

• Skeletal muscles can be attached to bones, but some may also attach to:

  • Cartilage

  • Ligament

  • Another muscle

  • Skin

• Origin

  • Definition: The more fixed, less movable attachment of a muscle (usually its proximal end).

• Insertion

  • Definition: The more movable end of the muscle (usually its distal end).

• Tendon

  • Also called a sinew cord or leader.

  • Definition: A cordlike fibrous connective structure that extends from the end of a muscle to a bony attachment.

• Aponeurosis

  • Definition: A sheet of fibrous connective tissue often attached at one end to a muscle and at the other end to a bone, cartilage, ligament, or other muscle.

• Tendon Sheath

  • Definition: A tunnel-like channel that surrounds a tendon.

• Tenosynovitis

  • Definition: An inflammation of a tendon sheath.

• Bursa

  • Definition: A saclike structure lying between a muscle or tendon and an adjacent bony prominence over which the muscle tendon moves.

• Bursitis

  • Definition: An inflammation of a bursa, often very painful.

• Calcification

  • Definition: The deposition of calcium, which may occur in a bursa or tendon sheath.

Muscle Functionality

1. Muscle Tone

   • Definition: Muscles do not completely relax when at rest but remain partly contracted.

2. Contraction

   • Definition: The main function of all muscles is to contract and cause movement of the body or its parts.

Muscle Actions

• Muscles that cross a joint to insert into a bone and cause movement are located proximal to that joint.

1. Prime Movers

   • Definition: Muscles that initiate and carry out a particular movement.

2. Antagonists

   • Definition: Muscles that perform movements opposite to those caused by the prime movers.

3. Synergists

   • Definition: Muscles that act with the prime movers to accomplish movement and prevent unwanted movement.

4. Fixation Muscles

   • Definition: Muscles that hold adjacent bones in a fixed position to allow the prime movers to perform their function.

5. Posture

   • Definition: Maintenance of the upright position of the body relies on balanced contraction of muscle groups and partial relaxation of opposing groups.

6. Muscle Spasm

   • Definition: A contraction of muscles that may persist for a long time without relaxation.

7. Paralysis of Muscles

   • Definition: Follows injury to or destruction of the nerves supplying that muscle.

   • Example: Poliomyelitis (infantile paralysis) can attack motor nerve cells to skeletal muscles.

Characteristics of Skeletal Muscles

1. Irritability

   • Definition: The property of being able to respond to stimuli.

2. Conductivity

   • Definition: The ability to conduct impulses from nerves or electrical stimuli.

3. Extensibility

   • Definition: The capacity for stretching, which occurs by lengthening the fibrils of each muscle fiber.

4. Elasticity

   • Definition: The ability to return to the original length after stretching.

5. Contractility

   • Definition: The ability to become shorter due to a shortening and thickening of each fibril of each muscle fiber.

Functions of the Muscular System

1. Movement

   • Skeletal muscles work with the skeletal system to generate voluntary movements.

2. Posture and Stability

   • Muscles assist in maintaining posture and stabilizing joints.

3. Digestion

   • Smooth muscles in the digestive tract help move food through the system.

4. Heat Production

   • Muscle contractions generate heat, important for regulating body temperature.

5. Respiration

   • The diaphragm and intercostal muscles are crucial for breathing.

6. Circulation

   • Cardiac muscles propel blood and smooth muscles in blood vessels regulate blood flow and pressure.

How Muscles are Named

1. By location.

2. By shape.

3. By direction of fibers.

4. By action.

5. By number of parts.

Important Muscles in Radiography

1. Diaphragm

   • A dome-shaped muscular partition that separates the thorax from the abdomen.

   • Greek Origin: (G) Diaphragma = a partition; (G) Phren = diaphragm.

   • Has three large openings:

   1. Aortic Hiatus

   2. Esophageal Hiatus

   3. Opening of the Inferior Vena Cava

   4. Costophrenic Sinus (Costodiaphragmatic Recess).

   • During inspiration (breathing in), it moves down; during expiration (breathing out), it moves up.

   • When supine, the diaphragm appears higher due to abdominal pressure.

   • Air escaping from a gastrointestinal perforation rises to the highest point in the abdomen.

   • Must be visible in both chest and abdominal X-rays.

2. Pectoralis Major Muscle

   • A thick fan-shaped muscle covering the upper anterior chest wall.

3. Psoas Major Muscle

   • Located lateral to the lumbar vertebrae in the posterior wall of the abdomen.

4. Intercostal Muscles

   • Fill spaces between adjacent ribs and their costal cartilages.

Examples of Ligaments and Tendons

1. Inguinal ligament.

2. Patellar ligament.

3. Ligamentum teres.

4. Calcaneal tendon.

Weak Abdominal Areas

1. Umbilical Area.

2. Inguinal Area.

3. Femoral Area.

Other Examples of Skeletal Muscles

1. Sternomastoid muscle.

2. Trapezius muscle.

3. Pectoralis minor muscle.

4. Latissimus dorsi muscle.

5. Deltoid muscle.

6. Sacrospinalis muscle.

7. Biceps brachii.

8. Psoas minor muscle.

9. Brachialis muscle.

10. Gluteus maximus muscle.

11. Triceps brachii.

12. Quadriceps femoris muscle.

13. Flexor digitorum profundus.

14. Biceps femoris muscle.

15. Extensor digitorum.

16. Gastrocnemius muscle.