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Constrictor muscles are muscles that contract a cavity or orifice or compress an organ. In the context of anatomy, the pharyngeal constrictor muscles are a group of three muscles – superior, middle, and inferior – that form the outer circular layer of the pharynx and play a pivotal role in swallowing. The pharyngeal constrictor muscles have multiple variants, and the superior constrictor can merge with the middle and inferior constrictor muscles. The inferior pharyngeal constrictor muscle is the thickest of the three outer pharyngeal muscles and is active during swallowing, breathing, and speech.
| Characteristics | Values |
|---|---|
| Definition | A muscle that contracts a cavity or orifice or compresses an organ |
| Types | Superior, middle, and inferior constrictor muscles |
| Function | The constrictor muscles propel food smoothly from the oral cavity into the oesophagus |
| Location | The pharyngeal constrictor muscles form the outer circular layer of the pharynx |
| Activation | The constrictor muscles contract involuntarily in a sequence known as peristalsis |
| Innervation | Innervated by the vagus nerve (pharyngeal plexus) |
| Blood supply | External carotid artery branches, including the ascending pharyngeal, facial, lingual, and maxillary arteries |
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What You'll Learn
The three types of pharyngeal constrictor muscles
A constrictor muscle is a muscle that contracts a cavity or orifice or compresses an organ. The pharyngeal constrictor muscles form the outer circular layer of the pharynx and are pivotal in swallowing. There are three types of pharyngeal constrictor muscles: the superior, middle, and inferior constrictor muscles.
The superior constrictor muscle originates from the pterygoid process, the posterior end of the mandible's mylohyoid line, and the pterygomandibular raphe. It inserts onto the pharyngeal tubercle of the skull base and the pharyngeal raphe, a midline tendinous seam where the constrictor muscles converge. Contraction of this muscle narrows the upper pharyngeal segment and closes the nasopharynx during swallowing.
The middle constrictor muscle arises from the greater and lesser horns of the hyoid bone and the stylohyoid ligament. It also inserts onto the median pharyngeal raphe, blending with superior and inferior constrictor fibres. This muscle constricts the middle pharyngeal portion during swallowing.
The inferior constrictor muscle is subdivided into the thyropharyngeus superiorly and the cricopharyngeus inferiorly. The thyropharyngeus originates from the thyroid cartilage, whereas the cricopharyngeus arises from the cricoid cartilage and merges with the oesophageal muscle. Both segments attach to the median pharyngeal raphe. The inferior constrictor compresses the lower pharynx. The coordinated movements of the constrictor muscles allow them to propel food smoothly from the oral cavity into the oesophagus.
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The role of constrictor muscles in swallowing
Constrictor muscles are those that contract a cavity or orifice or compress an organ. In the context of swallowing, the pharyngeal constrictor muscles play a pivotal role. The pharyngeal tube is highly muscular, with the pharyngeal constrictor muscles forming the outer circular layer of the pharynx. This layer consists of three constrictor muscles: the superior, middle, and inferior constrictors.
The superior constrictor muscle originates from the pterygoid process, the posterior end of the mandible's mylohyoid line, and the pterygomandibular raphe. During swallowing, it contracts to narrow the upper pharyngeal segment and close the nasopharynx. The middle constrictor muscle arises from the greater and lesser horns of the hyoid bone and the stylohyoid ligament. It inserts onto the median pharyngeal raphe, blending with the superior and inferior constrictor fibres. This muscle constricts the middle pharyngeal portion during the act of swallowing.
The inferior constrictor muscle is subdivided into the thyropharyngeus superiorly and the cricopharyngeus inferiorly. The thyropharyngeus originates from the thyroid cartilage, while the cricopharyngeus arises from the cricoid cartilage and merges with the oesophageal muscle. Both segments attach to the median pharyngeal raphe. The coordinated movements of the inferior constrictor muscle allow it to compress the lower pharynx and smoothly propel food from the oral cavity into the oesophagus.
The pharyngeal constrictor muscles work in conjunction with other muscles and nerves to facilitate the complex process of swallowing. The stylopharyngeus muscle, for example, is the only pharyngeal muscle innervated by cranial nerve IX. It originates from the styloid process of the temporal bone and inserts onto the thyroid cartilage. The contraction of this muscle elevates the pharynx and larynx, aiding in swallowing. The pharyngeal muscles receive dual innervation from the glossopharyngeal nerve (cranial nerve IX) and the vagus nerve (cranial nerve X), enabling the synchronous propulsion of food from the oral cavity to the oesophagus.
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The superior constrictor muscle
Originating from the medial end of the thyroid cartilage and the adjacent part of the cricoid cartilage, this muscle passes superiorly and posteriorly, inserting into the pharyngeal raphe, which is a fibrous band that runs longitudinally down the middle of the pharyngeal wall. When contracted, the superior constrictor muscle narrows the pharyngeal cavity, helping to propel food and liquid down into the esophagus. This muscle works in coordination with the other constrictor muscles of the pharynx, as well as the tongue and soft palate, to ensure efficient and safe swallowing.
Dysfunction of the superior constrictor muscle can lead to swallowing disorders known as dysphagia. This may manifest as difficulty initiating a swallow, food or liquid leaking into the nasal cavity (nasopharyngeal regurgitation), or food getting stuck in the throat. Assessment of the superior constrictor muscle function may be done through endoscopic evaluation or imaging techniques such as a modified barium swallow study. Treatment for dysphagia often involves swallowing therapy with a speech-language pathologist, who can provide exercises and strategies to improve the coordination and strength of the swallowing muscles, including the superior constrictor muscle.
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The middle constrictor muscle
The blood supply to the middle constrictor muscle is provided by several arteries, including the ascending pharyngeal artery, which is a branch of the external carotid artery, and the inferior thyroid artery, which arises from the thyrocervical trunk. Innervation of this muscle is provided by the pharyngeal branch of the vagus nerve (CN X), which carries motor fibres that control the muscle's contraction, and the glossopharyngeal nerve (CN IX), which provides sensory innervation.
In summary, the middle constrictor muscle plays a crucial role in the complex process of swallowing. Through its coordinated contractions with other muscles, it helps propel food through the pharynx and prevent aspiration into the nasal cavity or airway. Its actions also aid in the protection of the larynx during swallowing, preventing food or liquid from entering and potentially causing choking or aspiration pneumonia. Understanding the anatomy and function of the middle constrictor muscle is important in clinical contexts, particularly when dealing with disorders related to swallowing, such as dysphagia, or when performing surgical procedures in the head and neck region.
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The inferior constrictor muscle
A constrictor muscle is a type of muscle that contracts to narrow or close a passage or opening in the body. These muscles often work in opposition to dilator muscles, which function to widen or open passages. Constrictor muscles are found throughout the body and play important roles in various physiological processes. One example of a constrictor muscle is the inferior constrictor muscle, which is located in the neck and plays a crucial role in swallowing.
Now, let's focus on the inferior constrictor muscle in more detail:
During the act of swallowing, the inferior constrictor muscle contracts, narrowing the lower part of the pharynx. This contraction is essential for preventing food or liquid from entering the larynx or trachea, a process known as the swallowing reflex, or more specifically, the pharyngeal phase of swallowing. The pharyngeal phase involves a coordinated sequence of muscle contractions that propel the bolus (chewed and moistened food) from the pharynx into the esophagus while safeguarding the airway.
In summary, the inferior constrictor muscle is a vital component of the swallowing mechanism, contributing to the complex choreography of muscles that ensures food reaches the stomach safely while protecting the airways.
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Frequently asked questions
A constrictor muscle is one that contracts a cavity or orifice or compresses an organ.
Some examples of constrictor muscles include the superior, middle, and inferior pharyngeal constrictor muscles.
The superior constrictor muscle narrows the upper pharyngeal segment and closes the nasopharynx during swallowing.
The middle constrictor muscle constricts the middle pharyngeal portion during swallowing.
The inferior constrictor muscle is the thickest of the three outer pharyngeal muscles and it helps to move the lower part of the pharynx during swallowing.
