Muscles of the neck

Summary

In this detailed lecture, Dr. Morton explores the anatomy of the neck muscles, organized by their locations within the cervical fascia. He discusses the platysma in the superficial fascia, the sternocleidomastoid and trapezius in the deep investing fascia, and the scalene muscles in the prevertebral fascia. Each muscle's actions, innervation, and clinical significance are highlighted, emphasizing their roles in neck movement and stability. The discussion also touches on the relationship between these muscles and the overall anatomy of the trunk, providing a comprehensive understanding of their functions and interconnections.

Takeaways

• 😀 The neck muscles can be categorized based on their location within different layers of cervical fascia.
• 🧠 The platysma muscle, found in the superficial fascia, wrinkles the skin of the neck and is innervated by the facial nerve (cranial nerve VII).
• 💪 The sternocleidomastoid muscle turns the head to the opposite side and flexes the neck on the same side, innervated by the spinal accessory nerve (cranial nerve XI).
• 🏋️ The trapezius muscle elevates the scapula, shrugs the shoulders, and extends the head and neck.
• 📏 The scalene muscles (anterior, middle, and posterior) are responsible for elevating the first two ribs and assist in lateral flexion of the neck.
• 🔌 The brachial plexus and phrenic nerve exit between the anterior and middle scalene muscles, highlighting their importance in innervating the upper limb and diaphragm.
• 🗺️ The infrahyoid muscles (sternohyoid, sternothyroid, omohyoid, and thyrohyoid) help depress and support the hyoid bone during swallowing.
• 🧬 The infrahyoid muscles are innervated by the ansa cervicalis from the cervical plexus (C1 to C5).
• 🍊 The head and neck's stability is compared to an orange on a toothpick, illustrating the role of certain muscles in maintaining balance.
• 🏅 Somatic body wall muscles and branchial arch muscles both contribute to the function and stability of the neck, with different origins and attachments.

Q & A

What is the primary focus of Dr. Morton's discussion on neck muscles?

Dr. Morton focuses on the muscles of the neck, categorized by their location within different layers of cervical fascia.

Which muscle is located in the superficial fascia and what is its function?

The platysma muscle is located in the superficial fascia, and its function is to tense and wrinkle the skin of the neck.

How is the platysma muscle innervated?

The platysma muscle is innervated by the facial nerve (cranial nerve VII) through its cervical branch.

What are the main actions of the sternocleidomastoid muscle?

The sternocleidomastoid muscle turns the head to the opposite side and flexes the neck on the same side.

Which nerve innervates the sternocleidomastoid and trapezius muscles?

Both the sternocleidomastoid and trapezius muscles are innervated by the spinal accessory nerve (cranial nerve XI).

What role do the scalene muscles play in respiratory function?

The scalene muscles elevate the first and second ribs, which helps increase the volume of the thoracic cavity during inhalation.

Which muscles are included in the pretracheal fascia, and what are their actions?

The infrahyoid muscles (sternohyoid, sternothyroid, omohyoid, thyrohyoid) are included in the pretracheal fascia and primarily function to depress and support the hyoid bone.

What anatomical structures exit between the anterior and middle scalene muscles?

The phrenic nerve and the brachial plexus exit between the anterior and middle scalene muscles.

What is the significance of the analogy comparing the head and neck to an orange on a toothpick?

This analogy illustrates the need for muscular support to stabilize the head and neck, which can be prone to instability without proper muscle function.

How are the scalene muscles innervated?

The scalene muscles are innervated by branches from the ventral rami of cervical nerves C4 to C8.