submandibular

Introduction
Suprahyoid muscle and its embryology
Relation of mylohyoid and digastric muscle
Submandibular gland and duct
Development and histology
Sublingual gland and duct ,it’s development and histology.
Submandibular ganglion and its relations
Clinical anatomy
Blood and nerve supply of submandibular and sublingual duct
Conclusion
References

1. SUBMANDIBULAR REGION MONIKA Department of Public Health Dentistry.

2. Contents : Introduction Suprahyoid muscle and its embryology Relation of mylohyoid and digastric muscle Submandibular gland and duct Development and histology Sublingual gland and duct ,it’s development and histology.

3. Submandibular ganglion and its relations Clinical anatomy Blood and nerve supply of submandibular and sublingual duct Conclusion References

4. INTRODUCTION

5. Submandibular region includes deeper stuctures in the area between the mandible and hyoid bone including the floor of mouth and the root of tongue The submandibular region contains the supra-hyoid muscles, submandibular and sublingual salivary gland and submandibular ganglion

6. SUPRAHYOID MUSCLE The muscles are digastric ,the stylohyoid ,the mylohyoid and geniohyoid First layer formed by digastric and stylohyoid Second layer formed by mylohyoid Third layer formed by geniohyoid and hyoglossus Fourth layer formed by genioglossus

7. Embryology : The endodermal wall of foregut is separated from the surface ectoderm by a layer of mesoderm Soon the mesoderm comes to be arranged in the form of six bars that run dorsoventrally in the side wall of the foregut Each of these bars grows ventrally in the floor of the developing pharynx and fuses with the corresponding bar of the opposite side to form a pharyngeal or branchial arch

8. ARCHE’S DERIVATIVES First arch Anterior belly of digastric ,mylohyoid Second arch Posterior belly of digastric ,stylohyoid

9. SUPRAHYOID MUSCLE

10. Muscle origin Insertion Nerve supply Actions Digastric has two bellies united by intermediate tendon Anterior belly from digastric fossa of mandible Posterior belly from mastoid notch of temporal bone Both heads meet at intermediate tendon which perforates stylohyoid Anterior belly by nerve to mylohyoid Posterior belly : facial nerve Depresses mandible against resistance, elevates hyoid bone Stylohyoid Posterior surface of styloid process Junction of body and greater cornua of hyoid bone Facial nerve Pulls hyoid bone backwards and upwards

11. Muscle Origin Insertion Nerve supply Actions Mylohyoid :Flat triangular muscle Mylohyoid line of mandible Posterior fibers:body of hyoid bone Middle and anterior fibers :median raphe between mandible and hyoid bone Nerve to mylohyoid Elevates floor of mouth in first stage of deglutition, Helps in depression of mandible and elevation of hyoid bone Geniohyoid :short and narrow muscle lies above medial part of mylohyoid Inferior mental spine or genial tubercle Anterior surface of body of hyoid bone C1 through hypoglossal nerve Elevates hyoid bone May depresses mandible when hyoid bone is fixed

12. Relations of posterior belly of digastric : Superficial : mastoid process with the sternocleidomastoid , splenius capitis and longissimus capitis . The stylohyoid The parotid gland with retromandibular vein The submandibular salivary gland and lymph nodes Angle of mandible with medial pterygoid

13. DEEP : the transverse process of atlas with superior oblique and rectus capitis lateralis , Internal carotid , external carotid ,lingual, facial and occipital arteries , Internal jugular vein , Vagus , accessory and hypoglossal cranial nerves, The hyoglossus muscle

14. Upper border : the posterior auricular artery , And the stylohyoid muscle Lower border : occipital artery

15. Relations of mylohyoid Superficial Anterior belly of digastric Superficial part of the submandibular salivary gland Mylohyoid nerve and vessels Submental branch of the facial artery

16. Deep : Hyoglossus with its superficial relations namely Styloglossus , lingual nerve, the submandibular ganglion The deep part of submandibular salivary gland ,the submandibular duct ,the hypoglossal nerve and vena comitans hypoglossi

17. The genioglossus with its superficial relations Sublingual salivary gland ,lingual nerve Submandibular duct ,lingual artery Hypoglossal nerve

18. SUBMANDIBULAR SALIVARY GLAND : The paired  submandibular glands  are major  salivary glands  located beneath the  floor of the mouth situated in the anterior part of digastric triangle . It contains both serous and mucous secreting glandular elements .

19. Each gland weigh about 15 grams and contribute some 60–67% of unstimulated saliva secretion; on stimulation their contribution decreases in proportion as the parotid secretion rises to 50 % . The gland is about the size of walnut

20. It is roughly J shaped being indented by the posterior border of the mylohyoid muscle into superficial and deep part Superficial part : The part of the gland fills the digastric triangle

21. It extends upwards deep to the mandible upto mylohyoid line It has :inferior , lateral , medial surface The gland is partially enclosed between two layers of deep cervical fascia .

22. The superficial layer of fascia covers the inferior surface of the gland and is attached to base of mandible . The deep layer covers the medial surface of the gland and is attached to mylohyoid line of mandible .

23. RELATIONS : The inferior surface is covered by : Skin , platysma ,cervical branch of facial nerve , Deep fascia ,facial vein, submandibular lymph nodes . The lateral surface is related to : The submandibular fossa on the mandible Insertion of medial pterygoid The facial artery

24. The medial surface is related to : Mylohyoid , hyoglossus and styloglossus Inferiorly it overlaps stylohyoid and the posterior belly of the digastric

25. DEEP PART : It is small in size ,lies deep to mylohyoid and superficial to the hyoglossus and the styloglossus . Posteriorly :continuous with the superficial part round the posterior border of mylohyoid Anteriorly :it extends up to the posterior end of sublingual gland

26. SUBMANDIBULAR DUCT : It is thin walled and is about 5 cm long . It emerges at the anterior end of the deep part of the gland and runs forwards on the hyoglossus ,between the lingual and hypoglossal nerve . At the anterior border of the hyoglossus ,the duct is crossed by the lingual nerve and hypoglossal nerve . It opens on the floor of the mouth ,on the summit of sublingual papilla at the side of frenulum of the tongue .

27. DEVELOPEMENT The submandibular salivary glands develop later than the parotid glands and appear late in the sixth week of prenatal development. They develop bilaterally from epithelial buds in the sulcus surrounding the sublingual folds on the floor of the primitive mouth. Solid cords branch from the buds and grow posteriorly, lateral to the developing tongue. The cords of the submandibular gland later branch further and then become canalized to form the ductal part.

28. EMBRYOLOGY

29. The submandibular gland acini develop from the cords’ rounded terminal ends at 12 weeks, and secretory activity via the submandibular duct begins at 16 weeks. Growth of the submandibular gland continues after birth with the formation of more acini. Lateral to both sides of the tongue, a linear groove develops and closes over to form the submandibular duct.

30. HISTOLOGY Lobes contain smaller lobules, which contain  adenomeres , the secretory units of the gland. Each adenomere contains one or more acini, or alveoli, which are small clusters of cells that secrete their products into a duct.

31. The acini of each adenomere are composed of either serous  or  mucous cells , with serous adenomeres predominating. Some mucous adenomeres may also be capped with a  serous demilune , a layer of  lysozyme -secreting serous cells resembling a half moon.

32. Like other  exocrine glands , the submandibular gland can be classified by the microscopic anatomy of its secretory cells and how they are arranged. Because the glands are branched and the tubules forming the branches contain secretory cells, submandibular glands are classified as  branched tubuloacinar glands .

33. Further, because the secretory cells are of both serous and mucous types, the submandibular gland is a mixed gland. Mucous cells secrete mucin which aids in the lubrication of the food bolus as it travels through the esophagus .

34. In addition, the serous cells produce salivary amylase, which aids in the breakdown of starches in the mouth. The submandibular gland's highly active acini account for most of the salivary volume. The parotid and sublingual glands account for the remaining

35. Blood supply The gland receives its blood supply from the facial and lingual arteries drained by common facial and lingual veins. Lymphatic drainage : The lymphatics from submandibular gland first drain into submandibular lymph nodes into deep cervical particularly the jugulo – omohyoid lymph nodes.

36. NERVE SUPPLY It is supplied by branches from the submandibular ganglion . These  are regulated  directly  by the  parasympatheti c nervous system  and  indirectly by the  sympathetic nervous system . Parasympathetic  innervation to the submandibular glands is provided by the  superior salivatory nucleus  via the  chorda tympani , a branch of the  facial nerve , that becomes part of the  trigeminal nerve 's lingual nerve prior to synapsing on the  submandibular ganglion .

37. Increased parasympathethic activity increses the secretion of saliva. The sympathetic nervous system regulates submandibular secretions through  vasoconstriction  of the arteries that supply it.

38. Increased sympathetic activity reduces glandular bloodflow , thereby decreasing the volume of fluid in salivary secretions. Nevertheless, direct stimulation of sympathetic nerves will cause an increase in salivary enzymatic secretions.

39. SUBLINGUAL GLAND This is the smallest of the three salivary gland . It is almond shaped and weighs about 3 to 4g . It lies above mylohyoid , below the mucosa of the floor of the mouth medial to the sublingual fossa of the mandible and lateral to genioglossus .

40. SUBLINGUAL DUCT : They are drained by 8-20 excretory ducts called the ducts of Rivinus . The largest of all, the  sublingual duct  (of Bartholin) joins the submandibular duct to drain through the  sublingual caruncle .

41. The sublingual caruncle is a small papilla near the midline of the floor of the mouth on each side of the lingual frenum . Most of the remaining small sublingual ducts open separately into the mouth on an elevated crest of mucous membrane, the  plica sublingualis , formed by the gland and located on either side of the frenulum linguae .

42. HISTOLOGY The sublingual gland consists mostly of mucous acini capped with  serous demilunes  and is therefore categorized as a mixed mucous gland .

43. DEVELOPEMENT The sublingual salivary glands appear in the eighth week of prenatal development, two weeks later than the other two major salivary glands. They develop from  epithelial  buds in the sulcus surrounding the sublingual folds on the floor of the mouth, lateral to the developing submandibular gland.

44. These buds branch and form into cords that canalize to form the sublingual ducts associated with the gland. The rounded terminal ends of the cords form  acini .

45. HISTOLOGY The sublingual gland consists mostly of mucous acini capped with  serous demilunes  and is therefore categorized as a mixed mucous gland with a mucous product predominating.   Striated  and  intercalated  ducts are also present.

46. BLOOD SUPPLY The gland receives its supply from lingual and submental arteries . NERVE SUPPLY The nerves of the glands are parasympathetic secretory nerves from the chorda tympani . The sympathetic nerves are from the plexus on the facial artery . The sensory nerves are from the lingual nerves .

47. LYMPHATIC DRAINAGE : Its through the submental and submandibular lymph node groups .

48. Submandibular ganglion : This is a parasympathetic peripheral ganglion . It is a relay station for secretomotor fibers to the submandibular and sublingual salivary glands . Topographically , it is related to the lingual nerve but functionally it is connected to the chorda tympani branch of the facial nerve .

49. Location and relations The submandibular ganglion is small and  fusiform  in shape. It is situated above the deep portion of the  submandibular gland , on the hyoglossus muscle , near the posterior border of the  mylohyoid muscle . The ganglion 'hangs' by two nerve filaments from the lower border of the  lingual nerve  (itself a branch of the  mandibular nerve , CN V 3 ).

50. It is suspended from the lingual nerve by two filaments, one anterior and one posterior. Through the posterior of these it receives a branch from the  chorda tympani  nerve which runs in the sheath of the lingual nerve  The submandibular ganglion is the site of synapse for parasympathetic fibers and carries other types of nerve fiber that do not synapse in the ganglion.

51. FIBERS SYMPATHETHIC FIBERS : they are derived from plexus around facial artery . Sensory fibers reach the ganglion through the lingual nerve .

52. Sympathetic fibers

53. Secretomotor fibers superior salivatory nucleus preganglionic fibers arises nervusintermedius facial nerve

54. chorda tympani joins lingual nerve submandibular ganglion relay post ganglionic fibers submandibular and sublingual gland

55. Diseases affecting submandibular and sublingual gland : Classification : Cystic Inflammatory Obstructive Neoplastic diseases

56. Submandibular gland & Sublingual gland : True cyst of the submandibular gland is extremely rare . Ranula : The ranula is so named for its resemblance to a frog’s belly . This appearance is due to the accumulation of saliva beneath the thin mucous membrane of the floor of the mouth

57. The majority of these lesions result from extravasation of gland secondary to trauma or either a mucous extravasation or, less commonly, a mucous retention cyst

58. They are most common in the second decade of life and in females. The most common presentation of ranula is a painless, slow-growing, soft, and moveable mass located in the floor of the mouth. Usually, the lesion forms to one side of the lingual frenum ; however, if the lesion extends deep into the soft tissue, it can cross the midline.

59. The mylohyoid can allow the lesion to occur in the upper neck as a PLUNGING RANULA . When these extravasation cysts extend into the submandibular or submental space, they are called plunging ranula .

60. These cysts commonly extend into the submandibular triangle, occasionally they may extend superiorly into the parapharyngeal space as far as the base of the skull. Inferiorly to the supraclavicular area and upper mediastinum or posteriorly into the retropharyngeal space.

61. The diagnosis of a plunging ranula is of clinical significance for there are many benign as well as malignant lesions that have the same appearance during physical examination. Surgery is the main stay for the management of ranulas . These include incision and drainage, excision of ranula , marsupialization, and marsupialization with packing or complete excision of the sublingual gland.

62. In 1973 Roediger   et al . reported that two cases of plunging ranula were treated by primary excision of the sublingual gland through the mouth.

63. INFLAMMATORY OR REACTIVE CONDITIONS : Acute suppurative infection of the submandibular gland occurs less often than the parotid gland In healthy patients a stone or other underlying local conditions should be suspected and appropriate antibiotics can be obtained .

64. Viral infections which may affect is mumps, cytomegalic inclusion disease ,HIV-associated salivary gland disease . OBSTRUCTIVE DISEASE : Sialolithiasis (salivary calculi or salivary stones ) : Sialoliths are calcified structure that develop within the ductal system of a major or minor salivary glands . It is a both cause and consequence of chronic recurring sialadenitis

65. Occurs in men twice as often as in women . Submandibular gland is the most common site of occurrence accounting to 80% . According to Rauch’s extensive review of 1200 cases of salivary calculi in the german literature , 7% of salivary stones are found in sublingual gland .

66. Etiology : stasis ,infection ,and alteration of duct constituent In the salivary glands changes in pH , mucin content ,and ionic ratios provide an environment conducive to precipitation .

67. Increased incidence of formation of sialoliths in the submandibular gland : The pH of saliva is about 6.8-7.1 . The gland contains a greater concentration of calcium and phosphate salts ,in the form of apatites mainly .

68. The mucous content may become viscous . The duct of the submandibular gland is longer tortuous and situated at lower level than its orifice leading to increased salivary stagnation

69. Signs and symptoms : Patients complain periodic swelling when eating interspersed with periods of remission . Occasionally patients report spontaneous extrusion of small calculi from the ducts

70. The mucosa around the duct is inflamed particularly in the floor of mouth . Treatement : some stones pass spontaneously or following duct dilation majority requires surgical removal

71. Sialadenosis is an unusual non inflammatory ,non neoplastic disorder characterised by salivary glands enlargement ,submandibular glands can be involved . Sialadenitis is the inflammation of the salivary glands that can arise from various infections and non infectious causes .

72. Chronic obstructive sialoadenitis :In the submandibular gland , obstruction is virtually always secondary to stone formation . If removal of the stone does not cure the condition , the gland is excised .

73. Tumors : The majority of tumors occur in parotid gland ; 10 -15 % arise in the minor glands ; 5 – 10 % in the submandibular gland . SUB MANDIBULAR GLAND : Fifty percent of tumors of the submandibular gland are malignant .

74. A pleomorphic adenoma is the most common benign tumor and adenoid cystic carcinoma is the most common malignant tumor .

75. Clinically these lesions appear as a submandibular mass that can be palpated bimanually . Cervical lymphadenopathy and involvement of facial ,lingual ,or hypoglossal nerves are signs of malignancy . Benign tumors are excised with extracapsular dissection and excision of submandibular gland .

76. Tumors of the sublingual gland are rare but 90 % of these tumors are malignant . Pain is indicative of Perineural spread ,can rapidly involve lingual nerve ,the body of the mandible ,and the musculature of the tongue . Radical resection with wide margins is the recommended treatement .

77. Certain autoimmune diseases which affects salivary glands are : Benign lypmphoepithelial lesion or mikulicz disesease Sjogren’s syndrome is a chronic autoimmune disorder that involves the salivary and lacrimal glands .

78. Clinical anatomy For excision of the submandibular salivary gland ,a skin crease incision as a rule ,given more than 1 inch (2.5cm )below the angle of the jaw . The chorda tympani supplying secretomotor fibers to submandibular and sublingual salivary gland lies medial to the spine of sphenoid .

79. Injury to spine may result in loss of secretion from all three salivary glands . Submandibular lymph nodes lie both within and outside the submandibular salivary gland . The gland is to be removed in carcinoma tongue ,if lymph node infected .

80. Cancer of the tongue can metastasise into mandible . A stone in the submandibular duct can be palpated bimanually in the floor of the mouth and can even be seen if sufficiently large .

81. CONCLUSION : The location of major salivary glands ,muscles and ganglion makes it an important region of head and neck . Structure can get affected by any cystic ,obstructive ,inflammatory and neoplastic diseses leading to other pathologies .

82. REFERENCES: HUMAN ANATOMY ,BD CHAURASIA ,5 th edition. ORAL AND MAXILLOFACIAL SURGERY , FONSECA , 2 nd edition. ORAL AND MAXILLOFACIAL SURGERY , S M BALAJI ,2 nd edition. GRAY’S ANATOMY ,2 nd edition. TEXT BOOK OF ORAL PATHOLOGY ,SHAFER’S ,7 th edition.