Anatomy and physiology of larynx

1. Anatomy and
Physiology of Larynx
Dr. Krishna Koirala
2019-03-18

2. • Situated in the midline neck between 3rd - 6th
cervical vertebral level
• Consists of a framework of cartilages,
connected by ligaments and membranes,
lined by a mucous membrane and moved by
muscles

3. Anatomical components
–Cartilaginous skeleton
–Intrinsic muscles
–Extrinsic muscles
–Mucosal lining

6. Larynx (Anterior)

7. Larynx (Posterior)

8. Larynx (Posterior)

9. Larynx (Lateral)

10. Larynx (Superior)

11. Larynx (superior)

12. Larynx (sagittal section)

13. Larynx (sagittal section)

14. Larynx (coronal section)

15. Vocal fold

17. Vocal fold

18. Laryngeal Cartilages
Single (3) Paired (3)
Epiglottis Arytenoid
Thyroid Corniculate (cartilages of
Santorini)
Cricoid ( Signet ring like
cartilage)
Cuneiform (cartilages of
Wrisberg)

19. Cartilages (anterior)

20. Cartilages (posterior)

21. Cartilages (posterior)

22. Cartilage Histology
• Elastic
– Epiglottis, corniculate, cuneiform & apex of
arytenoid
– Little or no calcification
• Hyaline
– Thyroid, cricoid & remaining arytenoid
– Calcify as age advances
• Ossification begins by 25-30 yr & is completed by 60 yr

23. Indirect Laryngoscopy

25. Flexible Laryngoscopy
LEFT RIGHT

27. Laryngeal cavity
1. Laryngeal inlet
2. Laryngeal Vestibule
3. Laryngeal Ventricle
4. Rima glottis
5. Subglottis

28. Membranes & Ligaments
• Extrinsic
– Connect thyroid cartilage & epiglottis with hyoid
bone and cricoid cartilage with trachea
• Intrinsic
– Connect cartilages of larynx to each other
– Alter the position, shape and tension of the vocal
folds

29. Extrinsic
• Thyrohyoid
membrane
• Hyoepiglottic
ligament
• Cricotracheal
ligament

30. Intrinsic

31. 1. Quadrangular membrane
 Aryepiglottic ligament , Vestibular ligament
2. Crico-vocal membrane
 Vocal ligament ,Cricothyroid membrane
3. Thyroepiglottic ligament

32. Anatomical Divisions
A. Supraglottis: laryngeal
inlet to apex of ventricle
B. Glottis: apex of ventricle to
10 mm below
C. Subglottis: lower glottic
border to lower cricoid
border

33. A. Supraglottis
- Epiglottis, Aryepiglottic folds ,Ventricular
bands ,Laryngeal ventricle
B. Glottis
-True vocal cords , Anterior commissure,
Posterior commissure
C. Subglottis

34. Intrinsic Muscles
A. Acting on vocal cords
• Abduction  Posterior crico - arytenoid
• Adduction  Lateral crico-arytenoid
Transverse inter-arytenoid
Thyro-arytenoid externa
• Tension + lengthening  Cricothyroid
• Relaxation + shortening  Vocalis

35. B. Acting on laryngeal inlet
Opener  Thyroepiglottic
Closer  Oblique inter-arytenoid,
Aryepiglottic

36. Extrinsic Muscles
• Primary Elevators Secondary Elevators
 Stylopharyngeus  Mylohyoid
 Salpingopharyngeus  Stylohyoid
 Palatopharyngeus  Geniohyoid
 Thyrohyoid  Digastric
• Depressors
– Sternohyoid  Sternothyroid  Omohyoid

37. Posterior cricoarytenoid

38. Lateral cricoarytenoid

39. Transverse Inter-arytenoid

40. Cricothyroid

41. Thyroarytenoid externa + Vocalis

42. Oblique Inter-arytenoid

46. Shape of Glottis

47. Shape of Glottis
Quiet Respiration Forced Inspiration

48. Inspiration

49. Shape of Glottis
Normal voice Whisper

50. Normal phonation

51. Whisper

52. Mucous Membrane
• Stratified squamous epithelium
– Epiglottis (anterior surface + upper half of
posterior surface), upper part of aryepiglottic folds
& vocal cords
• Pseudo-stratified ciliated columnar (respiratory)
epithelium
– Rest of laryngeal mucous membrane

53. Nerve Supply
• Superior Laryngeal Nerve
– Internal: sensation to supraglottis & glottis
– External: motor to cricothyroid muscle
• Recurrent Laryngeal Nerve
– Sensation to subglottis
– Motor to all intrinsic muscles but cricothyroid

54. Blood Supply
• Arterial supply
– Laryngeal b/o of superior & inferior thyroid
• Venous drainage
– Superior thyroid vein  internal jugular vein
– Inferior thyroid vein  innominate vein

55. Lymphatic Drainage
• Supraglottis: via thyrohyoid membrane into
upper deep cervical nodes & thyroid gland
• Subglottis: via cricothyroid membrane into
pretracheal + lower deep cervical nodes
• Glottis: has no lymphatics

56. Functions of Larynx
1. Protection of lower airway
2. Phonation (voice production)
3. Passage of air into lungs for respiration
4. Chest fixation by glottic closure

57. Protection of lower airway
• 3-level below-upward closure (Tier Mechanism)
– Vocal cords
– Ventricular bands
– Aryepiglottic folds
• Cessation of respiration
– Mediated by glossopharyngeal nv & deglutition
centre
• Cough reflex

58. Voice Production
1. Voice activating air reservoir in lungs -
affects voice intensity
2. Voice generation: affects voice pitch
3. Voice resonation: affects voice quality
4. Voice articulation: affects voice quality

59. Voice Production

60. Theories of voice production
• Puff Theory
– Puffs of air emitted through glottis
– Puffs of air set up vibratory activity of glottis
• Neurochronaxic Theory
– Each vibratory cycle initiated by nerve impulse to
vocalis muscle via recurrent/vagus nerve
– Frequency of voice dependent upon rate of
impulses delivered
• Aerodynamic Myoelastic Theory

61. Voice generation
• Aerodynamic myoelastic theory
– Vocal cords kept approximated  Subglottic blast
of air opens vocal cords from below upwards &
causes their passive vibration, producing sound 
Bernoulli's effect closes vocal cords below upwards
 Cycle repeated

62. Aerodynamic myoelastic theory (opening
phase)

63. Aerodynamic Myoelastic theory (closing
phase)

64. Voice generation
 High pitch = short, thin, tense
less elastic vocal cords
 Low pitch = long, bulky, relaxed,
More elastic vocal cords
 Falsetto voice = tense vocal cords
with small phonatory gap

65. Falsetto voice

66. Chest fixation
• Closure of glottis helps in raising intra-thoracic &
intra-abdominal pressure required for coughing ,
vomiting , defecation, micturition ,climbing , weight-
lifting , labour etc.