The inferior pharyngeal constrictor muscle is a

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

of the

neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...

. 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 (involunta ...

. It arises from the sides of the

cricoid cartilage The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...

and the

thyroid cartilage The thyroid cartilage is the largest of the nine cartilages that make up the ''laryngeal skeleton'', the cartilage structure in and around the trachea that contains the larynx. It does not completely encircle the larynx (only the cricoid cartilage ...

. It is supplied by the

vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right ...

(CN X). It is active during

swallowing Swallowing, sometimes called deglutition in scientific contexts, is the process in the human or animal body that allows for a substance to pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. Swallowing i ...

, and partially during

breathing Breathing (or ventilation) is the process of moving air into and from the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxygen. All aerobic creatures need oxygen for cellular ...

and

speech Speech is a human vocal communication using language. Each language uses Phonetics, phonetic combinations of vowel and consonant sounds that form the sound of its words (that is, all English words sound different from all French words, even if ...

. It may be affected by

Zenker's diverticulum A Zenker's diverticulum, also pharyngeal pouch, is a diverticulum of the mucosa of the human pharynx, just above the cricopharyngeal muscle (i.e. above the upper sphincter of the esophagus). It is a pseudo diverticulum (not involving all layers of ...

Structure

The inferior pharyngeal constrictor muscle is composed of two parts. The first part (and more superior) arises from the

(thyropharyngeal part), and the second part arises from the

(cricopharyngeal part). * On the ''thyroid cartilage'', it arises from the oblique line on the side of the

lamina Lamina may refer to: Science and technology * Planar lamina, a two-dimensional planar closed surface with mass and density, in mathematics * Laminar flow, (or streamline flow) occurs when a fluid flows in parallel layers, with no disruption betwee ...

, 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. Structure The cricothyroid muscle orig ...

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 The pharyngeal raphe is a raphe that serves as the origin and insertion for several of the pharyngeal constrictors (thyropharyngeal part of the inferior pharyngeal constrictor muscle, middle pharyngeal constrictor muscle, superior pharyngeal const ...

in the posterior median line of the

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struc ...

. 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) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...

; the rest ascend, increasing in obliquity, and overlap the

middle pharyngeal constrictor muscle The middle pharyngeal constrictor is a fan-shaped muscle located in the neck. It is one of three pharyngeal constrictors. Similarly to the superior and inferior pharyngeal constrictor muscles, the middle pharyngeal constrictor is innervated by a ...

. The cricopharyngeal part is synonymous with the

upper esophageal sphincter The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...

(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 is supplied by branches from the pharyngeal plexus, and the

recurrent laryngeal nerve The recurrent laryngeal nerve (RLN) 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 recurrent laryngeal nerves, right and ...

. These come from the

(CN X). This is similar to the superior pharyngeal constrictor muscle and the

Variation

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

pharyngobasilar fascia As it descends it diminishes in thickness, and is gradually lost. It is strengthened posteriorly by a strong fibrous band, which is attached above to the pharyngeal spine on the under surface of the basilar portion of the occipital bone, and pas ...

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 radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, which ...

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 sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...

Clinical significance

Zenker's diverticulum

Uncoordinated muscle contraction,

cricopharyngeal spasm Cricopharyngeal spasms occur in the cricopharyngeus muscle of the pharynx. Cricopharyngeal spasm is an uncomfortable but harmless and temporary disorder. Signs and symptoms * Sensation of a 'lump' in the back of the throat * Throat feels swolle ...

, or impaired relaxation of the inferior pharyngeal constrictor muscle are currently considered the main factors in development of a

. Zenker's diverticulum develops between the two muscular bellies (the thyropharyngeal part and the cricopharyngeal part) in a small gap called

Killian's dehiscence Killian's dehiscence (also known as Killian's triangle) is a triangular area in the wall of the pharynx between the cricopharyngeus and thyropharyngeus which are the two parts of the inferior constrictors(also see Pharyngeal pouch). It can be seen ...

. 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 cricopharyngeus 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 (BoNT), is a neurotoxic protein produced by the bacterium '' Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromus ...

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 disease#Terminology, condition in its own right. It may be a sensation that suggests difficulty in the passag ...

, causing continued use of a

feeding tube Eating (also known as consuming) is the ingestion of food, typically to provide a heterotrophic organism with energy and to allow for growth. Animals and other heterotrophs must eat in order to survive — carnivores eat other animals, her ...

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