Cricoid cartilage

The cricoid cartilage /ˌkraɪkɔɪd ˈkɑːrtɪlɪdʒ/, 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 site for muscles, cartilages, and ligaments involved in opening and closing the airway and in producing speech.

Cricoid cartilage
Gray1194
Anterolateral view of head and neck (cricoid cartilage labeled at center left)
Larynx external en
Antero-lateral view of the ligaments of the larynx (cricoid cartilage visible near bottom center)
Details
Precursor4th and 6th branchial arch
Identifiers
LatinCartilago cricoidea
MeSHD003413
TAA06.2.03.001
FMA9615
Anatomical terminology

Structure

The cricoid cartilage sits just inferior to the thyroid cartilage in the neck, at the level of the C6 vertebra, and is joined to it medially by the median cricothyroid ligament and postero-laterally by the cricothyroid joints. Inferior to it are the rings of cartilage around the trachea (which are not continuous – rather they are C-shaped with a gap posteriorly). The cricoid is joined to the first tracheal ring by the cricotracheal ligament, and this can be felt as a more yielding area between the firm thyroid cartilage and firmer cricoid.

It is also anatomically related to the thyroid gland; although the thyroid isthmus is inferior to it, the two lobes of the thyroid extend superiorly on each side of the cricoid as far as the thyroid cartilage above it.

The posterior part of the cricoid is slightly broader than the anterior and lateral parts, and is called the lamina, while the anterior part is the band; this may be the reason for the common comparison made between the cricoid and a signet ring. The slender ventral half, and the most caudal of the palpable laryngeal landmarks, is also referred to as the anterior cricoid arch.[1]

Composition

It is made of hyaline cartilage, and so can become calcified or even ossified, particularly in old age.

Function

The function of the cricoid cartilage is to provide attachments for the cricothyroid muscle, posterior cricoarytenoid muscle and lateral cricoarytenoid muscle muscles, cartilages, and ligaments involved in opening and closing the airway and in speech production.

Clinical significance

When intubating a patient under general anesthesia prior to surgery, the anesthesiologist will press on the cricoid cartilage to compress the esophagus behind it so as to prevent gastric reflux from occurring: this is known as the Sellick manoeuvre. The Sellick Manoeuvre is typically only applied during a Rapid Sequence Induction (RSI), an induction technique reserved for those at high risk of aspiration.

The Sellick maneuver was considered the standard of care during rapid sequence induction for many years.[2] The American Heart Association still advocates the use of cricoid pressure during resuscitation using a BVM, and during emergent oral endotracheal intubation.[3] However, recent research increasingly suggests that cricoid pressure may not be as advantageous as once thought. The initial article by Sellick was based on a small sample size at a time when high tidal volumes, head-down positioning, and barbiturate anesthesia were the rule.[4]

Cricoid pressure may frequently be applied incorrectly.[5][6][7][8][9] Cricoid pressure may frequently displace the esophagus laterally, instead of compressing it as described by Sellick.[10][11] Several studies demonstrate some degree of glottic compression[12][13][14] reduction in tidal volume and increase in peak pressures.[15] Based on the current literature, the widespread recommendation that cricoid pressure be applied during every rapid sequence intubation is quickly falling out of favor.

Gastric reflux could cause aspiration if this is not done considering the general anesthesia can cause relaxation of the gastroesophageal sphincter allowing stomach contents to ascend through the esophagus into the trachea.

A medical procedure known as a cricoidectomy can be performed in which part or all of the cricoid cartilage is removed. This is commonly done to relieve blockages within the trachea.[16]

Fractures of the cricoid cartilage can be seen after manual strangulation also known as throttling.

Additional images

Larynx detailed

Cricoid cartilage.

Illu larynx

Larynx

Gray950

The cartilages of the larynx. Posterior view.

Gray952

Ligaments of the larynx. Posterior view.

Gray953

Sagittal section of the larynx and upper part of the trachea.

Slide4e

Cricoid cartilage

See also

References

  1. ^ Vashishta, Rishi (7 December 2017). "Larynx Anatomy". Medscape. Retrieved 15 July 2018.
  2. ^ Salem MR, Sellick BA, Elam JO. The historical background of cricoid pressure in anesthesia and resuscitation. Anesth Analg 1974;53(2):230-232.
  3. ^ American Heart Association (2006). Textbook of Advanced Cardiac Life Support. Dallas, TX: American Heart Association.
  4. ^ Maltby, J. M., & Berialt, M. T. (2002). Science, pseudoscience and Sellick. Canadian Journal of Anesthesia, 49(5), 443-447
  5. ^ Escott MEA, Owen H, Strahan AD, Plummer JL. Cricoid pressure training: how useful are descriptions of force? Anaesth Intensive Care 2003;31:388-391
  6. ^ Owen H, Follows V, Reynolds KJ, Burgess G, Plummer J. Learning to apply effective cricoid pressure using a part task trainer. Anaesthesia 2002;57(11):1098-1101
  7. ^ Walton S, Pearce A. Auditing the application of cricoid pressure. Anaesthesia 2000;55:1028-1029
  8. ^ Koziol CA, Cuddleford JD, Moos DD. Assessing the force generated with the application of cricoid pressure. AORN J 2000;72:1018-1030
  9. ^ Meek T, Gittins N, Duggan JE. Cricoid pressure: knowledge and performance amongst anaesthetic assistants. Anaesthesia 1999;54(1):59-62.
  10. ^ Smith, K. J., Dobranowski, J., Yip, G., Dauphin, A., & Choi, P. T. (2003). Cricoid pressure displaces the esophagus: an observational study using magnetic resonance imaging. Anesthesiology, 99(1), 60-64;
  11. ^ Smith, K. J., Ladak, S., Choi, Pt L., & Dobranowski, J. (2002). The cricoid cartilage and the oesophagus are not aligned in close to half of adult patients. Canadian Journal of Anesthesia, 49(5), 503-507.
  12. ^ Palmer, JHM, Ball, D.R. The effect of cricoids pressure on the cricoids cartilage and vocal cords: An endoscopic study in anaesthetized patients. Anaesthesia (2000): 55; 260-287
  13. ^ Hartsilver, E. L., Vanner, R. G. Airway obstruction with cricoids pressure. Anesthesia (2000): 55: 208-211
  14. ^ Haslam, N., Parker, L., and Duggan, J.E. Effect of cricoid pressure on the view at laryngoscopy. Anesthesia (2005): 60: 41-47
  15. ^ Hocking, G., Roberts, F.L., Thew, M.E. Airway obstruction with cricoids pressure and lateral tilt. Anesthesia (2001), 56; 825-828
  16. ^ Michihiko Sonea1; Tsutomu Nakashimaa1; Noriyuki Yanagita (1995) "Laryngotracheal separation under local anaesthesia for intractable salivary aspiration: cricoidectomy with fibrin glue support" The Journal of Laryngology & Otology:Cambridge University Press

External links

Cardiopulmonary nerves

Cardiopulmonary nerves are splanchnic nerves that are postsynaptic and sympathetic. They originate in cervical and upper thoracic ganglia and innervate the thoracic cavity.All major sympathetic cardiopulmonary nerves arise from the stellate ganglia and the caudal halves of the cervical sympathetic trunks below the level of the cricoid cartilage. Parasympathetic cardiopulmonary nerves arise from the recurrent laryngeal nerves and the thoracic vagus immediately distal to them. These interconnect with the sympathetic cardiopulmonary nerves to form the ventral and dorsal cardiopulmonary plexuses.

Cartilage

Cartilage is a resilient and smooth elastic tissue, a rubber-like padding that covers and protects the ends of long bones at the joints, and is a structural component of the rib cage, the ear, the nose, the bronchial tubes, the intervertebral discs, and many other body components. It is not as hard and rigid as bone, but it is much stiffer and much less flexible than muscle.The matrix of cartilage is made up of chondrin.

Because of its rigidity, cartilage often serves the purpose of holding tubes open in the body. Examples include the rings of the trachea, such as the cricoid cartilage and carina.

Cartilage is composed of specialized cells called chondrocytes that produce a large amount of collagenous extracellular matrix, abundant ground substance that is rich in proteoglycan and elastin fibers. Cartilage is classified in three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in relative amounts of collagen and proteoglycan.

Cartilage does not contain blood vessels (it is avascular) or nerves (it is aneural). Nutrition is supplied to the chondrocytes by diffusion. The compression of the articular cartilage or flexion of the elastic cartilage generates fluid flow, which assists diffusion of nutrients to the chondrocytes. Compared to other connective tissues, cartilage has a very slow turnover of its extracellular matrix and does not repair.

Cricoarytenoid articulation

The cricoarytenoid articulation (or joint) is a joint connecting the cricoid cartilage and the arytenoid cartilage.

Cricoid pressure

Cricoid pressure, also known as the Sellick manoeuvre or Sellick maneuver, is a technique used in endotracheal intubation to try to reduce the risk of regurgitation. The technique involves the application of pressure to the cricoid cartilage at the neck, thus occluding the esophagus which passes directly behind it.Cricoid pressure should not be confused with the "BURP" (Backwards Upwards Rightwards Pressure) manoeuvre, which is used to improve the view of the glottis during laryngoscopy and tracheal intubation, rather than to prevent regurgitation. As the name implies, the BURP manoeuvre requires a clinician to apply pressure on the thyroid cartilage posteriorly, then cephalad (upwards) and, finally, laterally towards the patient's right.

Cricoidectomy

A cricoidectomy is the surgical excision of the cricoid cartilage. The excision can often be performed under local anaesthetic and can either be partial or total. The procedure may be necessary as a treatment of pulmonary aspiration, to prevent progression to aspiration pneumonia. As the cricoid cartilage is the narrowest part of the trachea, it is also a common point of a blockage or narrowing (stenosis).

Cricothyroid articulation

The cricothyroid articulation (or joint) is a joint connecting the cricoid cartilage and the thyroid cartilage. It plays a key role in adjusting human voice pitch by changing the tension of the vocal cords. This tension is controlled mostly by the endolaryngeal vocalis and the extralaryngeal cricothyroid muscles which change vocal fold

tension by narrowing the cricothyroid space created by rotation and gliding movements in horizontal and vertical direction allowed for by the cricothyroid articulation.

Cricothyroid ligament

The cricothyroid ligament (also known as the cricothyroid membrane or Cricovocal membrane ) is composed of two parts:

the median cricothyroid ligament along the midline (a thickening of the cricothyroid membrane) and

the lateral cricothyroid ligaments on each side (these are also called conus elasticus).The median cricothyroid ligament is a flat band of white connective tissue that connects the front parts of the contiguous margins of the cricoid and thyroid cartilages. It is a thick and strong ligament, narrow above and broad below. Each lateral ligament is known as the conus elasticus.

The lateral cricothyroid ligament is overlapped on either side by laryngeal muscles.

The conus elasticus (which means elastic cone in Latin) is the lateral portion of the cricothyroid ligament.

The lateral portions are thinner and lie close under the mucous membrane of the larynx; they extend from the upper border of the cricoid cartilage to the lower margin of the vocal ligaments, with which they are continuous. The vocal ligaments may therefore be regarded as the free borders of each conus elasticus, and extend from the vocal processes of the arytenoid cartilages to the angle of the thyroid cartilage about midway between its upper and lower borders.

These anatomical structure have been called in many different ways in the past, thus generating confusion.

Cricothyroid muscle

The cricothyroid muscle is the only tensor muscle of the larynx aiding with phonation. It attaches to the anterolateral aspect of the cricoid and the inferior cornu and lower lamina of the thyroid cartilage, and its action tilts the thyroid forward to help tense the vocal cords. Not to be confused with the posterior cricoarytenoid muscles, which are the only muscles directly responsible for opening (abducting) the space between the vocal cords to allow for respiration.

Cricotracheal ligament

The cricotracheal ligament connects the cricoid cartilage with the first ring of the trachea.

It resembles the fibrous membrane which connects the cartilaginous rings of the trachea to each other.

Laryngeal cavity

The laryngeal cavity (cavity of the larynx) extends from the laryngeal inlet downwards to the lower border of the cricoid cartilage where it is continuous with that of the trachea.It is divided into two parts by the projection of the vocal folds, between which is a narrow triangular opening, the rima glottidis.

The portion of the cavity of the larynx above the vocal folds is called the vestibule; it is wide and triangular in shape, its base or anterior wall presenting, however, about its center the backward projection of the tubercle of the epiglottis.

It contains the vestibular folds, and between these and the vocal folds are the ventricles of the larynx.

The portion below the vocal folds is called the infraglottic cavity. It is at first of an elliptical form, but lower down it widens out, assumes a circular form, and is continuous with the tube of the trachea.

Laryngeal cleft

A laryngeal cleft or laryngotracheoesophageal cleft is a rare congenital abnormality in the posterior laryngo-tracheal wall. It occurs in approximately 1 in 10,000 to 20,000 births. It means there is a communication between the oesophagus and the trachea, which allows food or fluid to pass into the airway.

Larynx

The larynx (), commonly called the voice box, is an organ in the top of the neck of tetrapods involved in breathing, producing sound, and protecting the trachea against food aspiration. The larynx houses the vocal folds, and manipulates pitch and volume, which is essential for phonation. It is situated just below where the tract of the pharynx splits into the trachea and the esophagus. The word larynx (plural larynges) comes from a similar Ancient Greek word (λάρυγξ lárynx).

Lateral cricoarytenoid muscle

The lateral cricoarytenoid (also anterior cricoarytenoid) muscles extend from the lateral cricoid cartilage to the muscular process of the arytenoid cartilage. By rotating the arytenoid cartilages medially, these muscles adduct the vocal cords and thereby close the rima glottidis, protecting the airway. (Their action is antagonistic to that of the posterior cricoarytenoid muscles.) The lateral cricoarytenoid muscles receive innervation from the recurrent laryngeal branch of the vagus nerve (CN X).

Oliver's sign

Oliver's sign, or the tracheal tug sign, is an abnormal downward movement of the trachea during systole that can indicate a dilation or aneurysm of the aortic arch.

Oliver's sign is elicited by gently grasping the cricoid cartilage and applying upward pressure while the patient stands with his or her chin extended upward.

Due to the anatomic position of the aortic arch, which overrides the left main bronchus, a downward tug of the trachea may be felt if an aneurysm is present. It is also seen in light anesthesia.

The sign was first described by English military surgeon William Silver Oliver in 1878.

Posterior cricoarytenoid muscle

The posterior cricoarytenoid muscles are small, paired muscles that extend from the posterior cricoid cartilage to the arytenoid cartilages in the larynx.

Submental lymph nodes

The submental lymph nodes (or suprahyoid) are situated between the anterior bellies of the digastric muscle.

Their afferents drain the central portions of the lower lip and floor of the mouth and the apex of the tongue.

Their efferents pass partly to the submandibular lymph nodes and partly to a gland of the deep cervical group situated on the internal jugular vein at the level of the cricoid cartilage.

Suspensory ligament of thyroid gland

The suspensory ligament of the thyroid gland, or Berry's ligament, is a suspensory ligament that passes from the thyroid gland to the trachea.The posterior layer of the thyroid capsule is thick. On either side, it forms suspensory ligament for the thyroid gland known as the suspensory ligament of Berry. The ligaments are attached chiefly to the cricoid cartilage, and may extend to the thyroid cartilage.

Trachea

The trachea, colloquially called the windpipe, is a cartilaginous tube that connects the pharynx and larynx to the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from the larynx and branches into the two primary bronchi. At the top of the trachea the cricoid cartilage attaches it to the larynx. This is the only complete tracheal ring, the others being incomplete rings of reinforcing cartilage. The trachealis muscle joins the ends of the rings and these are joined vertically by bands of fibrous connective tissue – the annular ligaments of trachea. The epiglottis closes the opening to the larynx during swallowing.

The trachea develops in the second month of development. It is lined with an epithelium that has goblet cells which produce protective mucins (see Respiratory epithelium). An inflammatory condition, also involving the larynx and bronchi, called croup can result in a barking cough. A tracheotomy is often performed for ventilation in surgical operations where needed. Intubation is also carried out for the same reason by the inserting of a tube into the trachea. From 2008, operations have experimentally transplanted a windpipe grown by stem cells, and synthetic windpipes; however, a successful method for this method of transplant does not currently exist and development of such a method remains theoretically daunting.The word "trachea" is used to define a very different organ in invertebrates than in vertebrates. Insects have an open respiratory system made up of spiracles, tracheae, and tracheoles to transport metabolic gases to and from tissues.

Vocal process

In the human larynx, the vocal process is the anterior angle of the base of the arytenoid cartilage, as it projects horizontally forward and gives attachment to the vocal ligament.

The arytenoids are paired cartilages with a medial and a lateral process each. The medial process is called the vocal process because it is the attachment for the vocal ligament. The lateral process is the attachment of one of the major intrinsic muscles of the vocal folds and consequently named the muscular process.As the concave bases of the arytenoid cartilages move on the two convex articular surfaces on the cricoid cartilage (at the cricoarytenoid articulations), the vocal processes are brought closer to each other, which permits the vocal folds to make contact (adduct) and abduct.Just above the vocal process is a shallow depression, the oblong fovea of the arytenoid cartilage. Together they constitute the insertion for the vocalis muscle.Vocal process granulomas are rare and benign lesions that occur in 0.9–2.7% of adults with a voice disorder. Most occurrences and forms of vocal process granulomas regress spontaneously without any specific treatment, even large ones.

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