Development of human laryngeal cartilages.
MATERIALS AND METHODS: The present study was carried out on 40 human foetuses from 75 mm C.R.L. to 220 mm C.R.L. The foetuses were collected from Operation Theatres, Labour Room and Obstetric wards of Department Of Gynaecology And Obstetrics, Government Medical College, Jammu and various nursing homes operating in and around Jammu City after approval from Institutional Ethical Committee and written parental informed consent. Foetuses with Congenital Malformations were excluded from the study. Foetuses were preserved in 10% formalin and their Crown Rump length measured with Vernier Calliper. Assessment of the age of the foetuses was done according to the rule as described by Hamilton, Boyd and Mossman (5) (Table-1). Out of 40 foetuses dissected 15 foetuses were female and 25 were male. Two paramedian incisions were given on the anterior surface of the neck, skin was removed and larynx was removed enbloc along with epiglottis and some part of base of tongue. The tissue was fixed in 10% Formalin for 7 to 10 days and prepared for microtomy by Paraffin wax embedding method. 7 micron thick step sections (every 5th) were taken for fixation and staining. Staining was done by Harris Haematoxylin and Eosin stain (H & E) and Masson's Trichrome stain.
OBSERVATION: The human foetuses were divided into four groups (Table-2)
Group-1 (75 mm C.R.L-125 mm C.R.L)
Nine foetuses were dissected in this group. Ventricular shape ranges from circular to longitudinal depending upon the plane of section. The Thyroid and cricoid cartilages are observed which are well established. Small laminae of thyroid cartilages (fig-1) with their cornu are observed on each side of ventricular cavity. Ventral fusion of thyroid lamina is observed at 112 mm C.R.L. Mesenchymal condensation of tissue in the region of the arytenoids is seen in foetus of 112 mm C.R.L., which is above the cricoids cartilage on each side of the ventricular cavity. Due to these arytenoids masses, ventricular cavity assumes the shape of the letter T. A little amount of Mesenchymal condensation of epiglottic cartilage is observed in the epiglottic region at the top of the T shape ventricular cavity at 112 mm C.R.L (fig-2) There is no observance of the accordion effect which means that the hyoid, thyroid and the cricoids cartilage are in the close vicinity and may be overlapping one another.
Group-2 (128 mm C.R.L.-145 mm C.R.L.)
Eleven foetuses were dissected in this group. This group shows fully formed ventricular cavity. The size of thyroid laminae and cricoids cartilages has increased with well established perichondrium. Densely packed chondrocytes are seen which are uniformly scattered all over the cartilage within the perichondrium. No cell nests observed. The chondrification of the cricoids cartilage is well advanced than that of the thyroid cartilages and thyroid cartilages chondrify earlier to arytenoids. So developmental gradient of the cartilages is caudo-cranial. The condensation of the epiglottic cartilages shows progressive enlargement which is more in the centre as compared to the tapering ends. Arytenoid cartilages show more maturity. Among the cartilages cricoid cartilage appears better developed then the thyroid cartilage in all the foetuses. (fig-3)
Group-3 (146 mm-168 mm C.R.L.)
Eight foetuses were dissected in this group which showed fully developed ventricular cavity. The cartilages are more mature as compared to the previous group. The cricoid, thyroid and arytenoids are fully developed. The two laminae of thyroid show full maturity and ventral fusion are observed in some foetal specimens. The arytenoid shows caudo-cranial order of maturity. The epiglottic cartilages are better developed and more mature then the previous group. (Fig-4) All the cartilages shows well formed perichondrium within which uniformly scattered large mature chondrocytes are seen. Mesenchymal condensation for corniculate and cuneiform cartilages is observed a little above the arytenoids on both sides of the ventricular cavity. (fig-5)
Group-4 (170 mm-220 mm C.R.L)
Twelve foetuses were dissected in this group showing same features as the previous group as regards the ventricular cavity. All the cartilages are well developed at this stage and have attained full maturity.(fig-6) The cartilages formed show the elongation of 'Accordion'. The two laminae of thyroid have acquired semicircular shape and their ventral fusion is observed clearly. The cricoid is seen in the form of lamina which is quite larger than thyroid cartilage. The two arytenoids are observed to be larger among the paired cartilages. Epiglottis is fully mature and has attained its final shape. (Fig-7) The corniculate cartilages make their appearance as small pieces of cartilages articulating with the apices of the arytenoids cartilages. Faint impression of the small bars of cartilages called as cuneiform cartilages are observed one in each aryepiglottic fold.
DISCUSSION: The present study elucidates the sequential development of laryngeal cartilage under light microscopy. On reviewing the literature regarding the development of laryngeal cartilages, controversial reports were available. In the present study, well formed laminae of thyroid and cricoids cartilages are found at 12 weeks of intrauterine life. Major portions of the cartilages were chondrified. This was in accordance with the observation of Meena Negi & Chandrama Anand(1987), (6) Manoukian J.J & Tan A.K. (1997) (7), Love(Jr)(1983)(3), Lisser(1911)(8), Tucker & Tucker(1975) (9) & Hast M.H. (1970) (10).
Besides Hast M.H.(1970) (10), Love(Jr)(1983) & Tucker & Tucker(1975) (9) reported that major topography of the foetal larynx was complete between 8-16 weeks of intrauterine life. The present study reveals the Mesenchymal condensation for Arytenoid cartilages and epiglottic cartilages at 16 weeks of intrauterine life which is supported by the findings of Meena Negi and Chandrama Anand (1987) (6). However Tucker & Tucker (1975) (9) saw them at 8th& 6th weeks of intrauterine life respectively, whereas Hast M.H. (1970) (10) reported the cricoids and epiglottic development at the beginning of 3rdmonth and 2ndmonth respectively. According to them the cuneiform cartilages appear at 28 weeks of intrauterine life, but in the present study, they were seen at 26 weeks of intrauterine life, our finding being consistent with the findings of Meena Negi and Chandrama Anand(1970) (6)
Manoukian J.J. & Tan J.J (1997) (7)noticed the epiglottic maturation during 17-28 weeks of intrauterine life with simultaneous development of corniculate and cuneiform cartilages. The development and maturation of epiglottis, cricoids and corniculate cartilages in the present study is seen at 18-20 weeks of intrauterine life and this finding is consistent with findings of Meena Negi and Chandrama Anand(1987) (6).
The present study shows ventral fusion of thyroid laminae at 16 weeks which is not coinciding with findings of Tucker & Tucker(1975) (9) and Manoukian J.J. & Tan A.K.(1997) (7) who observed it at 12 weeks of intrauterine life, but the rule of elongation of 'Accordian' described by them is seen in present study. Caudocranial order of maturity of laryngeal cartilages as observed by Meena Negi and Chandrama Anand (1987) (6) was seen in the present study.
SUMMARY: The present study shows the different stages in the development of laryngeal cartilages in 40 human foetuses varying from 75 mm C.R.L. to 220 mm C.R.L. In the present study thyroid and cricoids cartilages are first to appear and are well formed at 12 weeks of gestation. Ventral fusion of thyroid lamina is seen at 16 weeks of gestation. The Mesenchymal condensation of arytenoids and epiglottic cartilages is seen at 16 weeks of gestation which starts chondrification at 12 weeks and 19 weeks of gestation respectively. Corniculate and cuneiform cartilages are seen at 26 weeks of gestation. All the cartilages show caudo-cranial order of maturity. No congenital anomaly in the form of immaturity of cartilages, thickening of cricoids cartilage, cleft in the cartilages is seen. The Anatomy of larynx is extremely important for Anaesthesiologists for mastering skills of advance airway management and in assessing risk factors for laryngeal injury during tracheal intubation. Laryngeal structures are frequently manipulated while inserting an endotracheal tube. The endolaryngeal structures are subject to insult during this procedure. Understanding of laryngeal injury requires knowledge of laryngeal anatomy of which developmental anatomy forms an important part. Major skeleton of larynx is formed from laryngeal cartilages, so study of the development of laryngeal cartilages is important.
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[1.] Sanjay Raina
[2.] Rachna Magotra
[3.] Shayama K Razdan
[4.] Ashwini K Sharma
PARTICULARS OF CONTRIBUTORS:
[1.] Demonstrator, Post graduate department of Anatomy, Govt. Medical college Jammu,
[2.] Assistant Professor, Post graduate department of Anatomy, Govt. Medical college Jammu
[3.] Professor and Ex H.O.D., Post graduate department of Anatomy, Govt Medical college Jammu
[4.] Lecturer, Post graduate department of Anatomy, Govt Medical college Jammu
NAME ADRRESS EMAIL ID OF THE CORRESPONDING AUTHOR:
Dr. Rachna Magotra, 737, Subash Nagar, Jammu.
Date of Submission: 09/07/2013.
Date of Peer Review: 09/07/2013.
Date of Acceptance: 10/07/2013.
Date of Publishing: 20/07/2013
Table--1 Showing Division of Foetuses in Four Groups GROUP CROWN RUMP NUMBER OF NO. LENGTH (CRL) FETUSES in mm I 75 to 125 09 II 128 to 145 11 III 146 to 168 08 IV 170 to 220 12 Table--2 Showing Crown Rump Length of Embryos Along With Their Estimated Ages S. CROWN-RUMP ESTIMATED AGE SEX NUMBER OF NO. LENGTH (mm) (In days) CASES STUDIED 1 75 86 M 2 2 97 101 M 1 3 100 103 F 2 4 112 111 F 1 5 115 113 F 1 6 120 116 M 1 7 125 120 M 1 8 128 122 M 1 9 130 123 M 1 10 134 126 M 2 11 135 127 F 2 12 136 127 F 1 13 140 130 M 1 14 142 131 F 1 15 143 132 M 1 16 145 133 F 1 17 146 134 M 1 18 150 136 M 2 19 158 142 M 2 20 160 143 F 1 21 168 148 F 2 22 170 150 M 1 23 172 151 F 1 24 176 154 M 1 25 180 156 M 1 26 187 161 M 2 27 190 163 F 2 28 200 170 M 2 29 220 183 M 2
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|Title Annotation:||ORIGINAL ARTICLE|
|Author:||Raina, Sanjay; Magotra, Rachna; Razdan, Shayama K.; Sharma, Ashwini K.|
|Publication:||Journal of Evolution of Medical and Dental Sciences|
|Date:||Jul 22, 2013|
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