Problem 33 - Anatomy and Physiology of Animals

Question

Describe the muscles of the anterior neck.

Step-by-Step Solution

Answer

The anterior neck muscles are primarily the suprahyoid, infrahyoid, and anterior vertebral groups, all with distinct roles in the movement and stabilization of the neck and hyoid bone.

Step 1: Identify Major Muscle Groups

The anterior neck muscles are divided into several groups based on their location and function. The main groups include the suprahyoid muscles, infrahyoid muscles, and the anterior vertebral muscles.

Step 2: Review Suprahyoid Muscles

The suprahyoid muscles, located above the hyoid bone, include the mylohyoid, geniohyoid, stylohyoid, and digastric muscles. These muscles are primarily responsible for elevating the hyoid bone and play a role in swallowing.

Step 3: Examine Infrahyoid Muscles

The infrahyoid muscles, found below the hyoid bone, consist of the sternohyoid, omohyoid, sternothyroid, and thyrohyoid muscles. These muscles function to depress the hyoid bone and larynx during swallowing and speech.

Step 4: Understand Anterior Vertebral Muscles

The anterior vertebral muscles include the longus colli, longus capitis, rectus capitis anterior, and rectus capitis lateralis muscles. These muscles assist in flexing the neck and stabilizing the cervical spine.

Key Concepts

Suprahyoid Muscles

The suprahyoid muscles are situated above the hyoid bone, an important bone in the neck.
They consist of four key muscles: mylohyoid, geniohyoid, stylohyoid, and digastric.
These muscles are crucial in the process of swallowing and play a significant role in elevating the hyoid bone.

• The mylohyoid muscle forms the floor of the mouth and assists in elevating the tongue.
• The geniohyoid muscle, when contracted, pulls the hyoid bone upwards and forwards.
• The stylohyoid muscle extends from the styloid process of the temporal bone to the hyoid bone, facilitating the elevation during swallowing.
• The digastric muscle has two bellies, connected by an intermediate tendon, assisting in the opening of the mouth.

Together, these muscles work harmoniously to ensure effective swallowing and speech production.

Infrahyoid Muscles

Located below the hyoid bone, the infrahyoid muscles are vital for movements of the hyoid and play a role in speech and swallowing.
This group includes the sternohyoid, omohyoid, sternothyroid, and thyrohyoid muscles.

• The sternohyoid muscle helps lower the hyoid bone after elevation.
• The omohyoid muscle, with its characteristic bending, aids in pulling down the hyoid bone.
• The sternothyroid muscle acts specifically to depress the larynx.
• The thyrohyoid muscle serves a dual role, not only lowering the hyoid but also elevating the thyroid cartilage.

Together, these muscles help coordinate the complex mechanisms of speech and swallowing by managing the position of the hyoid and laryngeal structures.

Anterior Vertebral Muscles

The anterior vertebral muscles are crucial for neck flexion and cervical spine stabilization.
This group comprises the longus colli, longus capitis, rectus capitis anterior, and rectus capitis lateralis muscles.

• The longus colli muscle flexes and rotates the neck, providing essential support to the cervical spine.
• The longus capitis muscle helps in flexing the head on the neck and stabilizing the skull.
• The rectus capitis anterior muscle assists in flexing the head forward.
• The rectus capitis lateralis muscle stabilizes the head laterally and aids in lateral flexion.

These muscles collaborate to maintain posture and enable daily head and neck movements such as nodding, turning, and looking around.