The inferior pharyngeal constrictor muscle is a

skeletal muscle Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...

of the

neck The neck is the part of the body in many vertebrates that connects the head to the torso. It supports the weight of the head and protects the nerves that transmit sensory and motor information between the brain and the rest of the body. Addition ...

. It is the thickest of the three outer

pharyngeal muscles The pharyngeal muscles are a group of muscles that form the pharynx, which is posterior to the oral cavity, determining the shape of its lumen, and affecting its sound properties as the primary resonating cavity. The pharyngeal muscles (involunt ...

. It arises from the sides of the cricoid cartilage and the thyroid cartilage. It is supplied by the

vagus nerve The vagus nerve, also known as the tenth cranial nerve (CN X), plays a crucial role in the autonomic nervous system, which is responsible for regulating involuntary functions within the human body. This nerve carries both sensory and motor fibe ...

(CN X). It is active during

swallowing Swallowing, also called deglutition or inglutition in scientific and medical contexts, is a physical process of an animal's digestive tract (e.g. that of a human body) that allows for an ingested substance (typically food) to pass from the mou ...

, and partially during

breathing Breathing (spiration or ventilation) is the rhythmical process of moving air into ( inhalation) and out of ( exhalation) the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxy ...

and

speech Speech is the use of the human voice as a medium for language. Spoken language combines vowel and consonant sounds to form units of meaning like words, which belong to a language's lexicon. There are many different intentional speech acts, suc ...

. It may be affected by Zenker's diverticulum.

Structure

The inferior pharyngeal constrictor muscle is composed of two parts. The first part (and more superior) arises from the thyroid cartilage (thyropharyngeal part), and the second part arises from the cricoid cartilage (cricopharyngeal part). * On the ''thyroid cartilage'', it arises from the oblique line on the side of the

lamina Lamina may refer to: People * Saa Emerson Lamina, Sierra Leonean politician * Tamba Lamina, Sierra Leonean politician and diplomat Science and technology * Planar lamina, a two-dimensional planar closed surface with mass and density, in mathem ...

, from the surface behind this nearly as far as the posterior border and from the inferior horn of the thyroid cartilage. * From the ''cricoid cartilage'', it arises in the interval between the

cricothyroid muscle The cricothyroid muscle is the only tensor muscle of the larynx aiding with phonation. It is innervated by the superior laryngeal nerve. Its action tilts the thyroid forward to help tense the vocal cords, thus increasing the pitch of the voice ...

in front, and the articular facet for the inferior horn of the thyroid cartilage behind. From these origins, the fibers spread backward and medially to insert with the muscle of the opposite side into the fibrous pharyngeal raphe in the posterior median line of the

pharynx The pharynx (: pharynges) is the part of the throat behind the human mouth, mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates ...

. The thyropharyngeal part mainly uses type 2 fibres (anaerobic), while the cricopharyngeal part mainly uses type 1 fibres (aerobic). Fibre type may change after birth. The inferior fibers are horizontal and continuous with the circular fibers of the

esophagus The esophagus (American English), oesophagus (British English), or œsophagus (Œ, archaic spelling) (American and British English spelling differences#ae and oe, see spelling difference) all ; : ((o)e)(œ)sophagi or ((o)e)(œ)sophaguses), c ...

; the rest ascend, increasing in obliquity, and overlap the middle pharyngeal constrictor muscle. The cricopharyngeal part is synonymous with the upper esophageal sphincter (UES), which controls the opening of the cervical esophagus. It is sometimes referred to as the cricopharyngeal inlet.

Nerve supply

The inferior pharyngeal constrictor muscle can be supplied by branches from the pharyngeal plexus, the

recurrent laryngeal nerve The recurrent laryngeal nerve (RLN), also known as nervus recurrens, is a branch of the vagus nerve ( cranial nerve X) that supplies all the intrinsic muscles of the larynx, with the exception of the cricothyroid muscles. There are two recur ...

, the external branch of the superior laryngeal nerve, or a combination of these (the recurrent laryngeal nerve being the most common innervation of the cricopharyngeal part). All these branches and nerves come from the

(CN X).

Variation

The inferior pharyngeal constrictor muscle can merge with superior pharyngeal constrictor, or posterior part of pharyngobasilar fascia.

Function

The inferior pharyngeal constrictor muscle has a broad role in moving the lower part of the

Swallowing

As soon as a bolus of food is received in the

, elevator muscles relax, and the pharynx descends. The inferior pharyngeal constrictor muscle, along with the other constrictors, contract upon the bolus, and convey it downward into the

. During

, they contract and cause

peristalsis Peristalsis ( , ) is a type of intestinal motility, characterized by symmetry in biology#Radial symmetry, radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an wikt:anterograde, anterograde dir ...

in the pharynx.

Breathing

The inferior pharyngeal constrictor muscle is partially used during

and

. It helps to keep the

open, particularly during

sleep Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain Sensory nervous system, sensory activity is inhibited. During sleep, there is a marked decrease in muscle activity and interactions with th ...

Clinical significance

Zenker's diverticulum

Uncoordinated muscle contraction, cricopharyngeal spasm, or impaired relaxation of the inferior pharyngeal constrictor muscle are currently considered the main factors in development of a Zenker's diverticulum. Zenker's diverticulum develops between the two muscular bellies (the thyropharyngeal part and the cricopharyngeal part) in a small gap called Killian's dehiscence. A diverticulum can form where a balloon of mucosa becomes trapped outside the pharyngeal boundaries. Food or other materials may reside here, which may lead to infection. Motor incoordination of the cricopharyngeal part can cause difficulty

. In extreme cases, this can be related to retrograde cricopharyngeal dysfunction (R-CPD) which causes the inability to burp; this is in part due to the muscle not being able to relax.

Botox Botulinum toxin, or botulinum neurotoxin (commonly called botox), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endi ...

or a cricopharyngeal myotomy are used to treat the condition.

Radiological damage

The inferior pharyngeal constrictor muscle may be damaged by chemotherapy-intensity modulated radiotherapy. This may lead to

dysphagia Dysphagia is difficulty in swallowing. Although classified under " symptoms and signs" in ICD-10, in some contexts it is classified as a condition in its own right. It may be a sensation that suggests difficulty in the passage of solids or l ...

, causing continued use of a

feeding tube A feeding tube is a medical device used to provide nutrition to people who cannot obtain nutrition by mouth, are unable to swallow safely, or need nutritional supplementation. The state of being fed by a feeding tube is called gavage, enteral f ...

rather than independent

Additional images

Image:Gray385.png, Muscles of the neck. Lateral view. Image:Gray957.png, Side view of the larynx, showing muscular attachments. Image:Slide5iiii.JPG, Inferior pharyngeal constrictor muscle Image:Slide1kuku.JPG, Deep dissection of larynx, pharynx and tongue seen from behind

References

External links

* () {{Authority control Muscles of the head and neck Pharynx