Exercise 16: Muscular System

• Muscles - contractile structures often involved in motion and locomotion
• In invertebrates such as nematodes, locomotory muscles form layers underneath their integuments
• In vertebrates, a skeletal muscle is usually attached on two ends with a free middle portion
• The fixed end of a muscle is known as what?

  origin
• The movable end of a muscle is called what?

  Insertion
• Sometimes, when a muscle has multiple origins, each one is referred to as a what?

  Head
• In the case of multiple insertions of muscle, they are known as what?

  slips
• The region between the origin and insertion is referred to as what?

  Belly
• Skeletal muscles are attached to each other by sheets of connective tissue known as what?

  Fascia
• The fascia may sometimes extend towards the bones, acting as the origin or insertion of a muscle, such as the cord-like tendon and the flat, but tough aponeuroses
• Action - movement of a body part that results from muscle contraction
• Synergists - muscles with the same action
• Antagonists - muscles with opposing actions
• What are the six most common actions of the muscles?

  Extension, flexion, adduction, abduction, elevation, depression
• Extension - straightening of a part
• Flexion - bending of a part
• When a muscle adducts, it brings the limbs toward the longitudinal axis
• Abductors - draw the limb away
• Elevation - raises a structure
• Depression - brings the muscle down
• What actions are usually associated with the movement of the jaw?

  Elevation, depression
• In the Ascaris lumbricoides x.s., what are located immediately beneath the epidermis?

  Longitudinal muscles
• The head of the toad is surrounded by how many pairs of muscles?

  3
• Temporalis - pair of triangular muscles found dorsally, behind each eye and it acts to raise the mandible.
• What is the origin and insertion of the temporalis respectively?

  Origin: mid-dorsal line of skull

  Insertion: posterior region of the mandible
• Depressor mandibulae - large muscle, will be found posterior to the tympanum and acts to lower the jaw
• What is the origin and insertion of the depressor mandibulae respectively?

  Origin: Mid-dorsal line

  Insertion: Angle of the jaw
• Mylohyoid - flat muscles found on the ventral surface of the lower jaw and elevates the floor of the mouth
• What is the origin and insertion of the mylohyoid respectively?

  Origin: Median raphe

  Insertion: Inner surface of the lower jaw
• The back of the toad is covered by a thick layer of connective tissue known as what?

  lumbo-dorsal fascia
• Dorsalis scapulae - muscle on top of the suprascapula wherein it abducts the forelimb and rotates the upper arm medially
• What is the origin and insertion of the dorsalis scapulae respectively?

  Origin: suprascapula Insertion: humerus
• Latissimus dorsi- posterior to the dorsalis scapulae which adducts the forelimb and slides the upper arm forward
• What is the origin and insertion of the latissimus dorsi respectively?

  Origin: lumbo-dorsal fascia

  Insertion: Humerus
• Longissimus dorsi - immediately bordering the vertebral column wherein it elevates the head and extends the trunk
• What is the origin and insertion of the longissimus dorsi respectively?

  Origin: Urostyle

  Insertion: Base of the skull
• Coccygeosacralis - lateral to the longissimus dorsi is a V-shaped muscle wherein it moves the urostyle dorsally or laterally to aid in locomotion
• What is the origin and insertion of the coccygeosacralis respectively?

  Origin: Transverse processses of the sacral vertebra

  Insertion: anterior half of the urostyle
• Coccygeoiliacus - another V-shaped muscle found lateral to the coccygeosacralis wherein it moves the ilium dorsally or laterally to aid in locomotion
• What is the origin and insertion of the coccygeoiliacus respectively?

  Origin: Urostyle

  Insertion: anterior part of the ilium