Muscular System

• Muscular system


  Consists of various types of muscle that each play a crucial role in the function of the body
• Muscles


  • Allow a person to move, speak, and chew
  • Control heartbeat, breathing, and digestion
  • Rely on the muscular system for temperature regulation and vision
• The muscular system contains more than 600 to 700 muscles that work together to enable the full functioning of the body
• Functions of the muscular system

  • Mobility
  • Stability
  • Posture
  • Circulation
  • Digestion
  • Urination
  • Childbirth
  • Vision
  • Organ Protection
  • Temperature Regulation
• Skeletal muscle


  • Also known as Striated Voluntary Muscle that consist of long fibers which are multinucleated cells
  • The only muscles that can be consciously controlled
  • Attached to the bones (hence called skeletal muscle); contractions resulted to movement
• Smooth muscle


  • Also known as Non-striated Involuntary Muscle or visceral muscles that has a spindle-shaped cells and contains a single nuclei (uninucleate)
  • Lines the inside of the blood vessels and the rest of the internal organs except the heart (have myofibrils but lack striations)
  • Weakest type of muscle but has an essential role in the digestion of food, and maintaining the circulation of blood in the blood vessels
• Cardiac muscle


  • Also known as Striated Involuntary Muscle
  • The heart muscle and the roots of the large blood vessels that pumps blood around the body
  • Stimulates its own contractions (rhythmically and involuntary) that for our heartbeat
  • Intercalated discs are present at intervals in cardiac muscle fibers
  • Each cell contains nucleus and is distinct entity
  • Signal from the nervous system control the rate of contraction
• Origin


  Less movable part of the muscle
• Insertion


  More movable part of the muscle
• Belly


  With pronounced bulge in the middle of origin and insertion
• Actions of muscles - Locomotion

  • Flexor/Flexion (Bend, close, or decrease the joint angle)
  • Extensor/Extension (Straighten, or increase the joint angle)
  • Abductor (Draw a part away from the median line)
  • Adductor (Draw a part toward the median line)
  • Circumduction (Movement of the body in circular manner)
  • Elevator/Levator (Raise or lift a part)
  • Depressor (Lower or depress a part)
  • Constrictor (Draws a part together or contract a part)
  • Dilator (Opens a part)
  • Pronator (Make a prone (turn it downward))
  • Supinator (Make it supinate (turn it upward))
  • Rotator (Revolve or rotate a part)
• How skeletal muscles are named

  • The direction of the fibers (Rectus, Obliques, Transverse)
  • Location or position (Lateralis, Medialis, Thoracic, Superficial, Deep)
  • Shapes (Deltoid, Trapezius)
  • Origin or Insertion (Sternocleidomastoid, Triceps, Biceps)
  • Actions (Extensors, Flexors, Rotators, Supinators)
  • Size (Maximus, Medius, Minimus, Major, Minor, Brevis, Longus)
• Muscle groups

  • Somatic muscles (Axial and appendicular muscles, Epaxial muscles, Dorsal muscles, Hypaxial muscles, Ventral muscles)
  • Visceral muscles (Smooth, cardiac and branchiomeric)
• Axial muscles are skeletal muscles of the trunk and tail and muscles under the pharynx, tongue, and eyeballs, divided into epaxial (continue to the skull) and hypaxial muscles (extended under the pharynx)
• Appendicular muscles are muscles inserted on the girdles, fins or limbs, with extrinsic appendicular muscles (axial) that their origin from the axial skeleton and intrinsic appendicular muscles (appendicular) that their origin on the girdles
• Muscular system of other chordates

  • Fish (Epaxial, Hypaxial, Lateral septum, Myomeres, Myosepta)
  • Amphibians (Metameric condition = obscure, Trunk reduced in volume)
  • Reptiles (Extend or straighten the spine and provide some lateral flexion, Lack myosepta and complex)
  • Avian (Have approximately 175 different muscles, Pygostyle (tail muscle), Suprecoracoideus – pulley like system to lift the wing)
• Muscles make up approximately 40% of total weight
• The heart is the hardest-working muscle in the body, pumping 5 quarts of blood per minute and 2,000 gallons daily
• The gluteus maximus is the body's largest muscle, located in the buttocks and helps humans maintain an upright posture
• The ear contains the smallest muscles in the body alongside the smallest bones, holding the inner ear together and connected to the eardrum
• The masseter muscle in the jaw is the strongest muscle by weight, allowing the teeth to close with a force of up to 55 pounds on the incisors or 200 pounds on the molars