Anatomy: Muscles of the Head and Neck

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Questions and Answers

Explain the functional relationship between agonist and antagonist muscles during a bicep curl.

During a bicep curl, the bicep muscle acts as the agonist, causing the flexion. The triceps muscle acts as the antagonist, relaxing to allow the movement and controlling the extension.

How do the origin and insertion points of a muscle contribute to its specific action?

The origin is the fixed attachment point, providing a stable base, while the insertion is the movable attachment point that is pulled towards the origin during muscle contraction, resulting in movement.

What is the role of synergistic muscles in movements, and provide an example related to breathing?

Synergistic muscles assist the agonist by stabilizing joints or providing additional force. During deep inhalation, the scalenes act as synergists, assisting the external intercostals in lifting the ribs.

Explain why facial expressions often lead to wrinkles, referencing specific facial muscles in your explanation.

<p>Facial muscles like the frontalis and orbicularis oris attach to the skin. Repeated contractions crease the skin over time, resulting in wrinkles.</p> Signup and view all the answers

How do the diaphragm and internal intercostal muscles work together during exhalation?

<p>During exhalation, the diaphragm relaxes and moves upward, decreasing the volume of the thoracic cavity. The internal intercostals contract to pull the ribs downward, further reducing thoracic volume and forcing air out of the lungs.</p> Signup and view all the answers

Describe the opposing actions of the external and internal oblique muscles during torso rotation.

<p>The external oblique on one side and the internal oblique on the opposite side work together to produce torso rotation. For example, to rotate to the right, the left internal oblique and right external oblique contract.</p> Signup and view all the answers

Explain how suprahyoid and infrahyoid muscles coordinate to facilitate swallowing.

<p>Suprahyoid muscles elevate the hyoid bone and larynx during the initial phase of swallowing, while infrahyoid muscles then depress the hyoid bone and larynx, returning them to their resting position after swallowing.</p> Signup and view all the answers

How does the coordinated action of the sternocleidomastoid muscles enable head movement?

<p>Unilateral contraction of the sternocleidomastoid turns the head to the opposite side, while bilateral contraction flexes the neck. Together they allow the head to nod or turn from side to side.</p> Signup and view all the answers

Describe how the iliocostalis, longissimus, and spinalis muscles work together to maintain an erect posture.

<p>These muscles run along the vertebral column and contract to extend the spine. The iliocostalis stabilizes the spine laterally, the longissimus extends the thoracic region, and the spinalis helps maintain posture along the spine.</p> Signup and view all the answers

How do the masseter and temporalis muscles contribute to chewing, and what is the role of the buccinator in this process?

<p>The masseter and temporalis muscles elevate the mandible to close the jaw for biting and chewing. The buccinator compresses the cheeks to keep food between the teeth during chewing, preventing it from escaping into the vestibule of the mouth.</p> Signup and view all the answers

Flashcards

Agonist Muscle

Does the main movement during muscle action.

Synergistic Muscle

Helps with the main movement, assisting the agonist muscle.

Antagonistic Muscle

Does the opposite movement of the agonist. Returns limb to original position.

Muscle Origin

The point where the muscle starts, typically not moving during contraction.

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Muscle Insertion

The point where the muscle ends, moves when the muscle contracts

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Frontalis

Raises eyebrows.

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Orbicularis Oculi

Closes the eyes.

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Orbicularis Oris

Closes the lips.

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Diaphragm (inhale)

Moves down to create space for air in lungs.

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Rectus Abdominis

Straight muscle in the front that assists you in sit-ups.

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Study Notes

  • Muscles facilitate bone movement, relying on joints to function.
  • A muscle must cross a joint in order to produce movement.

Muscle Types

  • Agonist muscles execute the primary movement.
  • Synergistic muscles assist in the movement.
  • Antagonistic muscles perform the opposite movement.

Muscle Attachment Points

  • Origin: The muscle's starting point that remains stationary.
  • Insertion: The muscle's ending point that moves upon contraction.

Head and Neck Muscles

  • Facial muscles enable expressions due to their attachment to the skin.
  • Frontalis raises eyebrows.
  • Temporalis lifts the jaw.
  • Masseter aids in chewing by lifting the jaw.
  • Buccinator assists with sucking and chewing.
  • Orbicularis oculi closes the eyes.
  • Orbicularis oris closes the lips.

Mastication Muscles

  • Temporalis & Masseter: Help chew by lifting the jaw.
  • Buccinator pushes food inside the mouth.

Tongue Muscles

  • Styloglossus pulls the tongue up and back
  • Hyoglossus pulls the tongue down and back

Breathing Muscles (Inhalation)

  • Diaphragm moves downward, creating space for air.
  • External intercostals lift the ribs, expanding the chest cavity.
  • Scalenes also assist in lifting the ribs during deep breathing.

Breathing Muscles (Exhalation)

  • Internal intercostals pull the ribs down, forcing air out.
  • Diaphragm relaxes, moving upward to expel air.

Abdominal Muscles

  • Protect the stomach, facilitate body movement, and aid forceful exhalation.
  • Tendinous Intersection creates the "six-pack" appearance.
  • Linea Alba is a white line located in the middle of the abs.
  • Rectus Abdominis is the straight muscle in the front, assisting in sit-ups.
  • Transverse Abdominis runs sideways, facilitating body twisting.
  • External Oblique is located on the side, aiding bending and twisting motions.
  • Internal Oblique works in opposition to the external oblique for twisting.

Swallowing and Speaking Muscles

  • Suprahyoid muscles (above the hyoid bone) lift the throat to aid swallowing.
  • Digastric helps open the mouth.
  • Mylohyoid & Stylohyoid assist in lifting the throat during swallowing.
  • Infrahyoid muscles (below the hyoid bone) push the throat down.
  • Sternohyoid & Sternothyroid lower the throat.
  • Thyrohyoid & Omohyoid assist in controlling throat movement.

Neck and Head Muscles

  • Platysma pulls the jaw down.
  • Sternocleidomastoid turns the head and bends the neck.
  • Scalenes lift the ribs during deep breathing.
  • Splenius Capitis & Semispinalis Capitis move the head backward.

Back Muscles (Vertebral Column Muscles)

  • Iliocostalis helps maintain an upright posture.
  • Longissimus is the longest muscle, aiding in back movement.
  • Spinalis runs along the spine, contributing to posture.

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