Reacción en cadena de la polimerasa (PCR)

The four main functions of larynx are respiration, protection of lower respiratory tract, phonation and fixation of the chest.

pRoteCtion of LoweR AiRwAyS

Larynx protects the lower respiratory tract in following ways:

„ _{Sphincteric closure of laryngeal opening: During swallowing}

food entry into air passage is prevented by the closure of three successive sphincters, so no food or vomitus can enter the larynx. The sphincters are following:

 _{Laryngeal inlet}  _{False cords}  _{True cords}

„ _{Cessation of respiration: When food comes in contact with}

the oropharynx, reflex generated by afferent fibers of ninth nerve ceases the respiration temporarily.

„ _{Cough reflex: Coughing dislodges and expels any foreign}

particle that comes in contact with respiratory mucosa. Larynx acts as a watchdog of lungs and immediately starts “barking” at the entry of any foreign body.

phonAtion AnD SpeeCh

„ _{Aerodynamic myoelastic theory of voice production: Like a}

wind instrument, larynx produces voice.

„ _{Speech: There are three phases in the production of speech:}

pulmonary, laryngeal and supraglottis/oral.

 Pulmonary phase: It creates energy flow with inflation of

lungs and expulsion of air. It provides a column of air to the larynx. The subglottic air pressure is generated by the exhaled air from the lungs with the help of contrac- tion of thoracic and abdominal muscles.

 Laryngeal phase: Vocal folds vibrate to create sound

that is then modified in the next phase. The air pres- sure opens the adducted cords and small puffs of air are released. Vocal fold vibrations are not the result of

The air pressure produced by the lungs controls the intensity of sound. The frequency of vocal cord vibrations controls the pitch of sound. Different frequencies are produced with changes in length, breadth, elasticity and extension of vocal folds.

ReSpiRAtion

The adduction of vocal cords during expiration and abduction of vocal cords during inspiration regulate the flow of air into the lungs.

fixAtion of CheSt

Closed larynx helps in the fixation of chest wall, which facilitates the action of various thoracic and abdominal muscles. This func- tion plays an important role during digging, pulling and climbing, coughing, vomiting, defecation, micturition and childbirth.

AnAtomy of tRACheobRonChiAL

tRee

tRACheA AnD bRonChi

Trachea is a dynamic organ. It expands and contracts longitu- dinally in response to the demands of respiration, swallowing and gravity. Trachea is about 10–12 cm long and extends from lower border of cricoid cartilage of larynx to the carina (level of V thoracic vertebra), where trachea divides into right and left main bronchi. Trachea has two parts—cervical and thoracic. As the bronchi divide, they become progressively smaller. The tracheobronchial tree conducts air from the upper respiratory tract to pulmonary alveoli.

Right main bronchus is wider shorter, and more vertical than left bronchus and hence more common site of foreign bodies.

„ _{Eparterial bronchus: Eparterial means above the artery. It is}

the right upper lobe bronchus that passes over the right pulmonary artery. The left upper lobe bronchus passes under the left pulmonary artery.

A deep bronchoscopic biopsy (5 mm cup forceps) from eparterial right upper lobe divider (spur)/secondary carina can involve right pulmonary artery and results in disastrous bleeding.

tRACheAL CARtiLAgeS

Trachea is supported by “U” shaped hyaline cartilages (16–20 in number) which have membranous interconnections. Posterior dehiscent portion of tracheal cartilages are closed by fibrous tAbLe 3 length of vocal cords in male and

female children and adults

Females Males Children Adults Children Adults length of vocal

cords in mm

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tissue. The fibrous membranous part contains smooth and trachealis muscle fibers. As the bronchi divide, the cartilages become progressively smaller and less complete, until the alveoli are formed. Alveoli do not have any cartilage.

muCoSA

Ciliated respiratory epithelium lines the tracheobronchial tree. This specialized membrane not only conditions the inspired air (including warming and humidifying) but also traps and expels small foreign bodies (1–5 mm particles), which are propelled back up to the pharynx and then swal- lowed. Larger foreign particles may trigger cough reflex.

bRonChopuLmonARy SegmentS (figS 15 to 17)

The bronchoscopist regards the lungs as being divided according to internal bronchial distribution, rather than by external fissures. The bronchoscopist needs an extended internal anatomic nomenclature that correlates closely with the endobronchial system and the locations description can be reliably described to another bronchoscopist. As s/he progresses to the more peripheral bronchopulmonary tree an “a” represents anterior segment and “b” posterior segments. A lesion in a sub-sub-subsegmental (fifth-order) bronchus in the left lung could be designated as LB1b1b.

fig. 15: Tracheobronchial tree and bronchopulmonary segments as seen through the bronchoscope. Right: RmB, right main bron-

chus; PS, posterior spur of carina; RUl, right upper lobe bronchus; Rll, right lower lobe bronchus; ml, middle lobe bronchus; 1, apical; 2, posterior; 3, anterior; 4, lateral of middle lobe; 5, medial of middle lobe; 6, apical of inferior lobe; 7, medial basal; 8, anterior basal; 9, lateral basal; and 10, posterior basal. left: lmB, left main bronchus; 1, apical; 2, posterior; 3, anterior; 4, superior lingual; 5, inferior lingual; 6, apical of lower lobe; 8, anterior basal; 9, lateral basal; and 10, posterior basal

fig.16 : lateral view of left lung showing bronchopulmonary

segments

fig. 17: lateral view of right lung showing bronchopulmonary

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mm diameter are 10th to 14th generation bronchi. • The right main bronchus is shorter, wider and nearly vertical

than the left. Therefore inhaled foreign bodies are more common in right main bronchus than the left.

• Aspiration is common into the posterior bronchus of the right upper lobe (Fig. 18).

tAbLe 4 Nomenclature of segmental lobules of pulmonary lobes

Lobes S e g m e n t a l

lobules Number

Right bronchus (Rb) and Lung

Right upper lobe (RUl)

Apical RB1 of RUl

Posterior RB2 of RUl Anterior RB3 of RUl Right middle lobe

(Rml)

lateral RB4 of Rml

medial RB5 of Rml Right lower lobe

(Rll) Superior (apical) RB6 of Rll medial basal RB7 of Rll Anterior basal RB8 of Rll lateral basal RB9 of Rll Posterior basal RB10 of Rll

Left bronchus (Lb) and Lung

left upper lobe (lUl)

Apical/Posterior lB1/2 of lUl

Anterior lB3 of lUl lingula of lUl Superior lB4 of lingula lUl

Inferior lB5 of lingula lUl

fig. 18: Aspiration into the posterior bronchus of the right upper

lobe in a patient in coma lying in right lateral position

Contd...

1. Dimension of larynx: Anteroposterior depth of male glottis is 24 mm.

2. ventricle of morgagni: It is the laryngeal ventricle that is situated in between true and false cords of larynx.

3. elastic cartilages: The auricular, epiglottis, corniculate, cuneiform cartilages and apices of the arytenoid cartilages are elastic and do not undergo calcification.

4. hyaline cartilages: The thyroid, cricoid and greater part of arytenoid cartilages are hyaline and undergo calcification. 5. wrisberg’s cartilage: This cuneiform fibroelastic cartilage is situated in aryepiglottic fold and does not undergo calcification. 6. Cricoid cartilage: It develops from VI branchial arch.

7. thyroid angle: In male, it is 90° _{while in female it is 120}°_.

8. broyle’s ligament: This is a small ligament which connects both vocal cords at the anterior commissure to the thyroid cartilage.

9. epithelium of vocal cords: It is nonkeratinizing stratified squamous.

10. hidden areas of the larynx: The infrahyoid epiglottis, anterior commissure, subglottis, ventricle and apex of pyriform fossa are not properly visible with indirect laryngoscopy. The direct laryngoscopy examination is required to rule out malignancies of these areas.

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11. Laryngeal spaces: The pre-epiglottic and paraglottic spaces may be invaded by carcinoma arising in the laryngeal mucosa. Edema of Reinke’s space causes polypoid degeneration of vocal cords.

12. Reinke’ space: This potential space with scanty subepithelial connective tissues lies under the epithelium of vocal cords and superficial to its elastic layer. It is limited above and below by the arcuate lines, anteriorly by anterior commissure and posteriorly by vocal process of arytenoids. Edema of Reinke’s space results in fusiform swelling of the membranous vocal cords.

13. Delphian node: Prelaryngeal lymph node in the region of the thyroid isthmus.

14. motor nerve supply of larynx: The recurrent laryngeal nerve supplies all the intrinsic muscles of the larynx except the cricothyroid (tenses the vocal cord), which is innervated by superior laryngeal nerve. Both these nerves are branches of vagus nerve. Therefore paralysis of recurrent laryngeal nerve does not affect cricothyroid.

15. Sensory nerve supply of larynx: The recurrent laryngeal nerve innervates laryngeal mucosa below the vocal fold whereas superior laryngeal nerve innervates laryngeal mucosa above the vocal fold.

16. galen’s anastomosis: It is the anastomosis between the branches of superior and recurrent laryngeal nerves (branches of vagus nerve).

17. non recurrent-recurrent laryngeal nerve (inferior laryngeal nerve): It is often associated with anomalous retro- esophageal right subclavian artery.

18. Adductors of vocal cord: They are lateral cricoarytenoid, thyroarytenoid, and interarytenoid muscles. 19. tensor of vocal cord: There is only one tensor muscle of the vocal cord and that is cricothyroid.

20. posterior cricoarytenoid muscle: This is the only abductor muscle of the larynx. It is supplied by recurrent laryngeal nerve.

21. glottic chink: In cadaveric position of the vocal cords vocal chink is 14 mm. In full abduction it is about 19 mm. During the whisper, the position of vocal cord is paramedian.

22. vocal cord palsy: It is commonly caused by lesions of recurrent laryngeal nerve. Because of the intrathoracic course of left recurrent laryngeal nerve left vocal cord palsy is twice more common than right vocal cord palsy.

23. tracheobronchial tree and larynx: Rate of topical absorption is highest.

fuRtheR ReADing

1. Armstrong WB, Netterville JL. Anatomy of larynx, trachea and bronchi. Otolaryngol Clin North Am. 1995;28:685-99. 2. Meller SM. Functional anatomy of the larynx. Otolaryngol Clin North Am. 1984;17:3-12.

3. Sasaki CT, Issacson G. Functional anatomy of the larynx. Otolaryngol Clin North Am. 1988;21:595-612. 4. Stocks J. Respiratory physiology during early life. Monaldi Arch Chest Dis. 1999;54:358-64.

We should give everyone his due. What is not edible for a man, give to a cow; what is not edible for a cow, give to a dog; what is not edible for a dog; throw into a lake for fishes to eat. But never waste.

—Mother Sarada Devi.

¯Surface anatoMy

 Mastoid, Mandible, Hyoid, Thyroid and Cricoid Carti- lages, Trachea, Thyroid gland, Sternocleidomastoid and Trapezius muscles, Carotid arteries, Internal jugular vein, Chassaignac’s Triangle

¯_{triangleS of neck}

 anterior Triangle: Submental, Submandibular, Carotid and Muscular

 Posterior Triangle: Occipital and Supraclavicular (Subcla- vian)

¯cervical faScia

 Superficial Cervical Fascia

 Deep Cervical Fascia: Superficial (Investing) layer, Middle (visceral Pretracheal) layer and deep (Prever- tebral) layer and Carotid Sheath.

¯_{lyMph noDeS of heaD anD neck}

 Submental, Submandibular, Parotid, Post auricular, Occipital, Facial, Malar, Superficial Group of Lateral Cervical, Deep Group, Internal Jugular Chain, Spinal accessory Chain, Transverse Cervical Chain, Scalene Nodes, Anterior Cornical Nodes, Anterior Jugular Chain, Prelaryngeal, Pretracheal, Paratracheal Nodes

 Classification

 Levels of Cervical Lymph Nodes  anterior Compartment Nodes

 Ho’s Triangle in Supraclavicular zone or Fossa ¯neck DiSSection

 Classification of Neck Dissection  Radical Neck Dissection (RND)

 Structures removed, Structures not removed, Incisions, Contraindications

 Modified Neck Dissection  Selective Neck Dissection  Extended Neck Dissection ¯thyroiD glanD

 Blood Supply and related laryngeal Nerves

 Superior Thyroid artery, external laryngeal Nerve and Joll’s Triangle

 Inferior Thyroid artery, recurrent laryngeal Nerve and Beahr’s Triangle  venous drainage  lymphatic drainage ¯parathyroiD glanDS ¯_DevelopMent  Thyroid Gland

 Thyroglossal Cyst or Fistula  ectopic Thyroid

¯clinical highlightS