Muscles

• The word 'muscle' is derived from the Latin word musculus, which means little mouse (mus).
• The muscle or flesh is a specialized tissue which can contract and produce movement. This is also known as the “property of a muscle”.
• There are 3 main types of muscles:

  1. Skeletal muscle (voluntary, striated muscle)
  2. Smooth muscle (involuntary, non-striated muscle)
  3. Cardiac muscle ( involuntary, striated muscle)
• Skeletal muscle

  • Form muscles of face & scalp, body & limbs
  • Both ends of a muscle are attached to bone except:

  1. in facial muscles where only one end is attached to bone and the other end is attached to skin; in diaphragm where the other end is attached to tendon
  2. sphincters where the muscle forms a circle and has no bony attachment
• The fleshy portion is called “flesh”; this ends either in a fibrous portion called a tendon or aponeurosis.
• A rounded or flat fibrous portion is called a tendon. In flat muscles, the fibrous portion is a flat sheet called aponeurosis.
• Muscle is fleshy, composed of muscle cells, is vascular and heals well. However, cannot resist stretching force.
• Tendon is fibrous, composed of connective tissue collagen, has poor blood supply, resists stretching force. However, it heals poorly.
• Organization of skeletal muscle

  A) Perimysium

  B) Perimysium

  C) Endomysium

  D) Epimysium

  
• Elastic connective tissue contains

  • capillaries
  • myosatellite cells that function in the repair of damaged muscle tissue
  • nerve fibers.
• The cytoplasm of muscle cells (excluding the myofibrils) is called sarcoplasm , and the cell membrane is called sarcolemma.
• Fill in the blank

  A) Epimysium

  B) Perimysium

  C) Endomysium

  D) Sarcoplasm

  E) Sarcolemma

  
• Fill in the blank

  A) athletes

  B) intramuscular injection

  C) Deltoid

  D) Gluteus medius

  E) Vastus lateralis

  
• Fill in the blank

  A) Parallel

  B) Pennate

  C) Fusiform

  D) Triangular

  E) Sphincter

  
• Arrangement of muscle fibers

  1. Fibers parallel to the long axis of the muscle

  (i) Muscle fibers may be parallel from origin to insertion e.g. strap muscles

  (ii) Muscle fibers may converge to a point at the ends → fusiform muscles; e.g. biceps muscle
• Fibers parallel to the long axis of the muscle

  A) rhomboid

  B) quadrilateral

  C) strap

  D) strap

  E) quadrate

  F) strap

  G) Strap

  
• Fill in the blank

  A) fusiform

  B) 2 bellies

  C) 2 headed

  
• Fibers in a muscle are arranged oblique to the long axis of the muscle.
• Uni-pennate Muscle: Fibers are arranged on one side of the tendon, resembling half a feather.
• Examples of Uni-pennate Muscles include Flexor pollicis longus (forearm) and Extensor digitorum longus (leg).
• Bi-pennate Muscle: Oblique fibers arise on both sides of the tendon, resembling a whole feather.
• Tendon of insertion extends upward through the middle of the muscle in a Bi-pennate Muscle.
• Examples of Bi-pennate Muscles include Flexor hallucis longus (leg) and Rectus femoris.
• Multi-pennate Muscle: Septa extend into the muscle attachment, dividing it into feather-like portions.
• Circum-pennate Muscle: Fibers converge on a tendon from the walls of a cylindrical space.
• Tendon lies buried within the muscle in a Circum-pennate Muscle.
• Examples of Circum-pennate Muscles include Tibialis anterior (leg).
• Arrangement of muscle fibers

  (3) Radial, triangular or fan-shaped muscle

  • The fleshy fibers converge from a wide attachment to a fibrous apical insertion.
  • E.g. temporalis muscle
• Fill in the blank

  A) Unipennate

  B) Bipennate

  C) Fusiform

  D) Multipennate

  E) Circular

  F) Convergent

  G) Parallel

  
• The variation in diameter of skeletal muscle fibers depends on factors such as the specific muscle and the age and sex, state of nutrition, and physical training of the individual. Exercise enlarges the musculature and decreases fat deposits.
• The increase in muscle thus obtained is caused by formation of new myofibrils and a pronounced growth in the diameter of individual muscle fibers. This process, characterized by augmentation of cell volume, is called hypertrophy.
• Tissue growth by an increase in the number of cells is termed hyperplasia . Hyperplasia does not occur in either skeletal or cardiac muscle but does take place in smooth muscle, whose cells have not lost the capacity to divide by mitosis.
• Hyperplasia is rather frequent in organs such as the uterus, where both hyperplasia and hypertrophy occur during pregnancy
• Muscles According to Action

  1. Prime Mover:

  • Initiates a desired movement.
  • Example: In arm flexion, the Biceps is the prime mover.

  1. Antagonist:

  • Opposes the action of another muscle.
  • Interaction: Prime mover requires the relaxation of the antagonist for smooth movement.

  1. Fixators:

  • Muscle groups stabilizing proximal joints, allowing movement at distal joints on a fixed base.
  • Ex: Muscles acting on the shoulder joint fix it for better finger movement.
• Fill in the blank

  A) Prime mover

  B) Prime mover

  C) Antagonist

  D) Antagonist

  E) Flexion

  F) Extension

  
• Fill in the blank

  A) Prime mover

  B) Antagonist

  C) Synergist

  
• Paralysis

  • Loss of motor power (power of movement)
  • This is due to inability of the muscles to contract, caused either by damage to the motor nerves or by the inherent disease of muscles (myopathy).
• Muscular spasm :

  • Localized spasms often result from muscle pulls.
  • Painful and require relaxation through treatment.
  • Generalized spasms can occur in conditions like tetanus and epilepsy.
• Disuse Atrophy:

  • Cause: Muscles not used for a long time.
  • Effect: Muscles become thin and weak.
  • Term: Referred to as disuse atrophy.
• Hypertrophy:

  • Cause: Adequate or excessive use of specific muscles.
  • Effect: Results in better development or hypertrophy.