Block 5 Anatomy The Larynx & Neck

The cricothyroid muscle is supplied by the external laryngeal nerve. The external laryngeal nerve is a branch of the superior laryngeal nerve, which is a branch of the vagus nerve (cranial nerve X). It provides motor innervation to the cricothyroid muscle, which is responsible for tensing the vocal cords and increasing vocal pitch. The other muscles listed are not supplied by the external laryngeal nerve.

During the tonsillectomy, the glossopharyngeal nerve was likely damaged. The glossopharyngeal nerve is responsible for providing sensation to the posterior third of the tongue, as well as controlling the muscles involved in swallowing and the salivary glands. The loss of sensation reported by the boy suggests damage to this nerve, which is commonly associated with tonsillectomy procedures.

When the internal laryngeal nerve is damaged, the general sensation will be lost in the larynx above the vocal cords. The internal laryngeal nerve is responsible for providing sensory innervation to the laryngeal mucosa above the vocal cords. Therefore, damage to this nerve will result in a loss of general sensation in that specific area.

The bullet must have pierced the jugular foramen because it is the only site mentioned in the question that is associated with the symptoms described. The jugular foramen is a large opening in the base of the skull through which several important structures pass, including the glossopharyngeal nerve, vagus nerve, and accessory nerve. Damage to these nerves can lead to the symptoms described, such as paralysis of certain muscles, loss of taste sensation, and hoarseness. Therefore, the bullet must have passed through the jugular foramen to cause these specific effects.

The posterior cricoarytenoid muscle is responsible for opening the vocal cords after they are fully adducted. This muscle contracts to pull the arytenoid cartilages away from the midline, allowing the vocal cords to separate and air to pass through, producing sound during breathing or phonation. The other muscles listed do not have the specific function of opening the vocal cords.

The right sternocleidomastoid muscle is most likely responsible for the boy's condition. The sternocleidomastoid muscle is located in the neck and is responsible for tilting and rotating the head. When the right sternocleidomastoid muscle contracts, it causes the head to tilt towards the right and the right ear to move closer to the right shoulder, which matches the boy's symptoms. The other muscles listed do not have the same actions or location as the sternocleidomastoid muscle, making them less likely to be the cause of the condition.

The laryngeal skeleton moves at the cricothyroid and cricoarytenoid joints. These joints allow for the movement and adjustment of the vocal folds, which are essential for speech and phonation. The cricothyroid joint is responsible for lengthening and tensing the vocal folds, while the cricoarytenoid joint allows for the rotation and sliding of the arytenoid cartilages, which control the opening and closing of the vocal folds. Together, these joints play a crucial role in vocalization and voice production.

During the partial thyroidectomy, the external laryngeal nerve might have been damaged. This nerve innervates the cricothyroid muscle, which is responsible for controlling the tension of the vocal cords. Damage to the external laryngeal nerve can lead to changes in voice quality, such as a monotonous speech of low pitch.

The external laryngeal nerve is responsible for innervating the cricothyroid muscle, which is important for vocal cord tension and voice production. Damage to this nerve can result in a weak voice, which explains the patient's complaint after the surgery.

Paralysis of the posterior cricoarytenoid muscle requires emergency opening of the airway. This muscle is responsible for opening the vocal cords during inhalation, allowing air to flow into the lungs. If this muscle is paralyzed, the vocal cords will remain closed, obstructing the airway and making it difficult to breathe. Therefore, it is crucial to open the airway in such cases to ensure adequate ventilation and prevent respiratory distress.

When the left recurrent laryngeal nerve is damaged, it leads to paralysis of the muscles innervated by this nerve. The posterior cricoarytenoid muscle is the only muscle listed that is innervated by the recurrent laryngeal nerve. Therefore, it is the first muscle to be involved in this situation. The cricothyroid muscle is innervated by the external branch of the superior laryngeal nerve, the lateral cricoarytenoid muscle is innervated by the recurrent laryngeal nerve, the thyroarytenoid muscle is innervated by the recurrent laryngeal nerve, and the thyroepiglottis muscle does not exist.

The correct answer is the thyroid gland. The patient's symptoms of a swelling on the front of the neck and breathlessness, along with the finding of a swelling to the left of the midline that moves up and down on swallowing, are consistent with an enlarged thyroid gland. The thyroid gland is located in the front of the neck and can become enlarged due to conditions such as goiter or thyroid nodules. This can cause compression of nearby structures, leading to symptoms such as breathlessness.

The internal laryngeal nerve pierces the lateral surface of the thyrohyoid membrane.

The cricothyroid membrane is chosen for the incision in an emergency operation for opening the airway. This is because the cricothyroid membrane is a relatively thin and easily accessible area in the neck. It is located between the cricoid cartilage and the thyroid cartilage, making it an ideal location for a quick and effective incision to establish an emergency airway.

The aryepiglottis muscle is responsible for closing the inlet of the larynx during swallowing. It helps to prevent food or liquid from entering the airway by covering the opening of the larynx with the epiglottis. This action ensures that swallowed material goes down the esophagus and into the stomach, instead of going into the trachea and potentially causing choking or aspiration.

Compression of the carotid artery can help control bleeding in cases of a punctured carotid artery. The transverse process of C6 is the correct answer because it is the bony point closest to the carotid artery. Applying pressure to this area can help reduce blood flow and control bleeding. The other options listed are not as close to the carotid artery and would not be as effective in controlling bleeding.

The cricothyroid muscle is responsible for controlling the tension of the vocal cords, and its palsy would result in a change in pitch and voice quality. Therefore, it is not associated with the symptoms mentioned in the question stem.

The vocal folds are found within the space enclosed by the thyroid cartilage. The thyroid cartilage is a large, shield-shaped cartilage that forms the front part of the larynx, or voice box. It is located in the neck and is commonly referred to as the "Adam's apple" in males. The vocal folds, also known as vocal cords, are two folds of mucous membrane that stretch horizontally across the larynx. When air passes through the vocal folds, they vibrate, producing sound. Therefore, the thyroid cartilage acts as a protective housing for the vocal folds and helps in the production of sound.

The sympathetic trunk is not damaged in this case because it is located behind the chest wall, whereas the knife wound is described as being above the clavicle and in the chest wall. Therefore, it is unlikely that the sympathetic trunk would be affected by this injury.