Infrahyoid Muscles Overview

Overview

This lecture covers the infrahyoid muscles of the neck, focusing on their origins, insertions, innervations, blood supply, and actions.

Infrahyoid Muscle Group Overview

• Infrahyoid muscles are located below the hyoid bone and lower the hyoid bone and larynx.
• Main muscles include omohyoid, sternohyoid, sternothyroid, and thyrohyoid.

Omohyoid Muscle

• Originates from the upper border of the scapula.
• Inserts on the lower border of the hyoid bone.
• Innervated by branches of cervical spinal nerves C1-C3.
• Blood supplied by infrahyoid artery, lingual artery, and superior cervical artery.
• Depresses the hyoid bone.

Sternohyoid Muscle

• Originates from the posterior surface of the sternum and inner end of the clavicle.
• Inserts on the lower border of the hyoid bone.
• Depresses the hyoid bone and larynx.
• Supplied by the superior thyroid artery.

Sternothyroid Muscle

• Originates from the posterior surface of the sternum.
• Inserts on the thyroid cartilage (Adam’s apple).
• Depresses the thyroid cartilage and larynx.
• Innervated by branches of cervical spinal nerves C1-C3 and possibly the hypoglossal nerve.
• Supplied by the superior thyroid artery.

Thyrohyoid Muscle

• Originates from the thyroid cartilage.
• Inserts on the lower border and greater cornua of the hyoid bone.
• Elevates the thyroid cartilage and depresses the hyoid bone.
• Innervated by the hypoglossal nerve and cervical spinal nerves C1-C2.
• Supplied by the superior thyroid artery.

Key Terms & Definitions

• Infrahyoid Muscles — muscles below the hyoid bone that lower the hyoid and larynx.
• Hyoid Bone — a small bone in the neck supporting tongue movement and swallowing.
• Thyroid Cartilage — the largest laryngeal cartilage, also known as the Adam’s apple.
• Innervation — the nerve supply to a muscle.
• Blood supply — arteries providing oxygenated blood to the muscles.

Action Items / Next Steps

• Review textbook diagrams of the infrahyoid muscles and their attachments.
• Memorize origins, insertions, innervations, and blood supply for each muscle.