accessory muscles

Examples of accessory muscles in the following topics:

• Inspiration

  • These muscles are referred to as accessory muscles of inhalation.
  • Sternocleidomastoid muscle: muscles that connect the sternum to the neck and allow for rotation and turning of the head.
  • Trapezius muscle: muscles in the shoulders, which retracts the scapula and expands the upper part of the thoracic cavity.
  • The accessory muscles assist breathing by expanding the thoracic cavity in a similar way to the diaphragm.
  • A common problem in novice singers is breathing with the accessory muscles of the neck, shoulder, and ribs instead of the diaphragm, which gives them a much smaller air supply than what is needed to sing properly.

• Accessory (XI) Nerve

  • The accessory nerve is designated the 11th of 12 cranial nerves and it controls the muscles of the shoulder and neck.
  • The accessory nerve is the 11th of 12 cranial nerves and it controls the sternocleidomastoid and trapezius muscles of the shoulder and neck.
  • The accessory nerve provides motor innervation from the CNS to the sternocleidomastoid and trapezius muscles of the neck.
  • Limited range of motion or diminished muscle strength often indicates injury of the accessory nerve.
  • Upon exiting the skull via the jugular foramen, the spinal accessory nerve pierces the sternocleidomastoid muscle before terminating on the trapezius muscle.

• Types of Breathing

  • 3) Costal breathing: a mode of breathing that requires contraction of the intercostal muscles.
  • As the intercostal muscles relax, air passively leaves the lungs.
  • In addition to the contraction of the diaphragm and intercostal muscles, other accessory muscles must also contract.
  • During forced expiration, accessory muscles of the abdomen, including the obliques, contract, forcing abdominal organs upward against the diaphragm.
  • In addition, accessory muscles (primarily the internal intercostals) help to compress the rib cage, which also reduces the volume of the thoracic cavity.

• Functional Anatomy of the Respiratory System

  • The respiratory system include lungs, airways and respiratory muscles.
  • During vigorous inhalation (at rates exceeding 35 breaths per minute), or in approaching respiratory failure, accessory muscles—such as the sternocleidomastoid, platysma, and the scalene muscles of the neck—are recruited to help sustain the increased respiratory rate.
  • Pectoral muscles and latissimus dorsi are also accessory muscles for the activity of the lungs.
  • Active or forced exhalation is achieved by the abdominal and the internal intercostal muscles.
  • During forced exhalation, as when blowing out a candle, the expiratory muscles, including the abdominal muscles and internal intercostal muscles, generate abdominal and thoracic pressure that force air out of the lungs.

• Brief Overview of Cranial Nerves

  • The Trochlear Nerve (IV)-The trochlear nerve is a motor nerve that innervates the superior obliuque muscle of the eye, which controls rotational movement.
  • The Abducens Nerve (VI)- The abducens nerve is a motor nerve that innervates the lateral rectus muscle of the eye, which controls lateral movement.
  • The Facial Nerve (VII)- The facial nerve controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity.
  • The Vagus Nerve (X)-The vagus nerve is responsible for many tasks, including heart rate, gastrointestinal peristalsis, sweating, and muscle movements in the mouth, including speech and keeping the larynx open for breathing.
  • The Spinal Accessory (XI)- The spinal accessory nerve controls specific muscles of the shoulder and neck.

• Muscles that Cause Movement at the Foot

  • Movement of the foot and toes requires the action of many muscles.
  • Although many extrinsic muscles attach within the dorsal compartment, there are only three intrinsic muscles which act on the foot and two extrinsic muscles which act on the foot rather than the ankle.
  • Extensor Digitorum Brevis - The extensor digitorum brevis muscle is a deep-lying intrinsic muscle lying beneath the tendon of the extensor digitorum longus.
  • Extensor Hallucis Brevis - The extensor hallucis brevis muscle is an intrinsic muscle of the foot lying between the extensor digitorum longus and lateral to extensor hallucis longus.
  • Lumbricals - The lumbricals are four small skeletal muscles, accessory to the tendons of the flexor digitorum longus and numbered from the medial side of the foot.

• Control of Muscle Tension

  • The pull exerted by a muscle is called tension.
  • This amount of stretching does not usually occur because accessory proteins, internal sensory nerves, and connective tissue oppose extreme stretching.
  • This is close to the maximum force the muscle can produce.
  • Muscle tension is produced when the maximum amount of cross-bridges are formed, either within a muscle with a large diameter or when the maximum number of muscle fibers are stimulated.
  • Muscle tone is residual muscle tension that resists passive stretching during the resting phase.

• Accessory Sex Glands

  • The primary purposes of the accessory sex glands are to produce seminal fluid and to clean and lubricate the urethra.
  • Seminal vesicle fluid is expelled under sympathetic contraction of the muscularis muscle coat.
  • The prostate is sheathed in the muscles of the pelvic floor, which contract during the ejaculatory process.
  • The prostate also contains some smooth muscles that help expel semen during ejaculation.
  • They are enclosed by transverse fibers of the sphincter urethrae membranaceae muscle.

• Anatomy of the Male Reproductive System

  • The male reproductive system includes external (penis, scrotum, epididymus, and testes) and internal (accessory) organs.
  • Special muscles in the wall of the scrotum contract and relax in order to move the testes near the body.
  • The internal organs of the male reproductive system are called accessory organs.

• Digestive System: Small and Large Intestines

  • The lower gastrointestinal tract includes the small and large intestines, rectum, anus, and accessory organs.
  • The undigested food is sent from the ileum to the colon through the ileocecal valve via peristaltic movements of the muscle.
  • Accessory organs are those that add secretions (enzymes) that catabolize food into nutrients.
  • Accessory organs include salivary glands, the liver, the pancreas, and the gallbladder.
  • Describe the parts of the digestive system from the small intestine through the accessory organs