Mandible and Hyoid Bones gross features.pptx

This presentation is brief overview of Mandible and Hyoid bones

1. MANDIBLE DR. ABDUL RAUF MEMON ANATOMY DEPARTMENT LUMHS JAMSHORO

2. MANDIBLE H orseshoe shaped bone of viscerocranium. L argest bone of viscerocranium. Besides the bones of the middle ear, mandible is only mobile bone in the  skull.

3. Unlike other bones of the skull, the mandible doesn’t articulate with the surrounding bones via sutures, It articulates rather by synovial joint called the  temporomandibular joint . Joint allows it to be attached to skull while at same time produce various translatory and rotatory movements. These movements allow complex actions like chewing and speaking.

4. BODY Body is horizontal portion. It consists of two parts:  Alveolar part Base of mandible

5. ALVEOLAR PART OF BODY OF MANDIBLE It is the upper portion of the body. It consists of two bony lamellae: T hick buccal lamella , Thin lingual lamella. They are parallel to each other, They form shallow trench on the upper surface of the alveolar part. Lamellae are connected by interalveolar septa, These septae cut the trench into sockets which house the mandibular teeth .

6. BASE OF BODY OF MANDIBLE It  is inferior part of body It has several anatomical landmarks. M andibular symphysis: Fibrous tissue in the midline, It ossifies by the first year of life. It unites the left and right halves of the mandible in order to form a single, symmetrical bone. 

7. MENTAL PROTUBERANCE B ony triangular prominence at midline of body.

8. MENTAL TUBERCLE P aired bony prominence on each side of the mental protuberance .

9. OBLIQUE LINE Crest extend from ramus to body of mandible. provides insertion point for depressor anguli oris

10. MENTAL FORAMEN Opening inferior to second mandibular premolar tooth It provides passage for mental nerve and vessels.

11. INTERNAL SURFACE OF THE BASE OF MANDIBLE DIGASTRIC FOSSA Paired depression on lower margin Located on each side of the midline .

12. MENTAL SPINES Paired bony eminences on the midline. P rovide attachment for the genioglossus and  Geniohyoid  muscles .

13. SUBMANDIBULAR FOSSA P aired depression on each side of the mental spines It houses submandibular gland .

14. SUBLINGUAL FOSSA D epression located superior to the mental spines It lodges sublingual gland .

15. MYLOHYOID LINE P aired oblique crest on the sides Provides attachment to mylohyoid muscle

16. Mylohyoid groove

17. MANDIBLE C onsists of two parts Body, Rami.

18. Digastric fossa

19. RAMUS It is vertical part of the mandible. It unites with the body at angle of mandible (i.e. gonial angle ). Angle can range from 110° to 130° Angle can vary depending on the age, sex and ethnicity. Angulation is larger in men usually.

20. SUPERIOR PART OF THE RAMUS It consists of two  processes: Coronoid process (anterior process) Condylar process (posterior process ). Incisure between them is called the mandibular notch Notch crossed by the masseteric nerve and vessels. 

21. MEDIAL SURFACE OF THE RAMI Pterygoid tuberosity: Rough area for the insertion of the  medial pterygoid muscle . I nferior alveolar ( M andibular ) foramen: Starting point of the mandibular canal which is traversed by the  inferior alveolar nerve  and its branches. M ylohyoid sulcus: C ontains the mylohyoid artery and nerve.

22. POSTEROLATERAL ASPECT OF RAMUS MASSETERIC TUBEROSITY Rough surface for insertion of masseter muscle .

23. Muscles that originate from the mandible Buccinator muscle Buccinator ridge of mandible Mentalis muscle Incisive fossa of mandible Depressor labii inferioris muscle Oblique line of mandible Depressor anguli oris muscle Mental tubercle and oblique line of mandible Anterior belly of digastric muscle Digastric fossa Genioglossus muscle Superior mental spine Geniohyoid muscle Inferior mental spine Mylohyoid muscle Mylohyoid line

24. Muscles that insert to the mandible Lateral pterygoid muscle Pterygoid fossa Temporalis muscle Apex and medial surface of coronoid process of mandible Medial pterygoid muscle Medial surface of ramus (pterygoid tuberosity) and angle of mandible Masseter muscle Lateral surface of ramus and angle of mandible Platysma Lateral surface of ramus and angle of mandible

25. CLINICALS Alveolar bone resorption occurs when the teeth are lost There is a lack of structures to support the bone There is increased pressure upon the bone due to chronic denture wearing .

26. MANDIBULAR FRACTURES Intra- and extracapsular condylar fractures are the most frequent mandibular fractures They usually result due to car accidents or indirect force due to violence. Other  mandibular fracture areas include Body, Angle, Symphysis, Ramus, Alveolus Coronoid process In decreasing order of frequency.

27. MANDIBULAR FRACTURES A  mandibular fracture  rarely occurs in isolation. Fracture on one side is frequently associated with a fracture on the contralateral side. Therefore, if one fracture is observed, another should be searched for. E.g.: F ractured neck of the mandible is often observed in conjunction with a fracture of the contralateral mandibular body .

28. FRACTURES OF THE  CORONOID PROCESS  

29. FRACTURES OF THE NECK OF THE MANDIBLE  

30. FRACTURES OF THE  ANGLE OF THE MANDIBLE

31. FRACTURES OF THE  BODY OF THE MANDIBLE  

32. TOOTH APLASIA It  is common in, Third   molars, Premolars Lateral   incisors. This can lead to gaps in the teeth and an uneven alveolar ridge .

33. OSTEORADIONECROSIS It  is a disorder that occurs due to cancer treatment Bone disintegrates because of radiation .

34. OSTEOMYELITIS  is an infection that can cause chronic sequestrations and bone disintegration within the mandible. It is irreversible and the mandible often needs resecting .

35. CYST FORMATION M ost often happens in the mandible where the molars sit. There are many types of cyst Common symptom is large bone resorption and bone weakening if the cyst is left untreated .

36. HYOID  BONE It   is a ‘U’ shaped bone Located in the anterior neck. It lies at the base of the mandible (approximately at the level of C3), Here it acts as a site of attachment for the anterior neck muscles .

37. STRUCTURE OF THE HYOID BONE BODY : Central  part of the bone. It has, Anterior convex surface, Posterior concave surface.

38. GREATER HORN: Projects from each end of the body in a posterior, superior and lateral direction. It acts as a site of attachment for numerous neck muscles .

39. LESSER HORN: Arises from superior aspect of hyoid bone, near the origin of the greater horn. It projects superoposteriorly (toward the styloid process of the temporal bone ). S tylohyoid ligament attaches to the apex of the lesser horn .

40. MUSCULAR ATTACHMENTS It is unique in the fact that, It does not articulate with any other bones, It is suspended in place by the  muscles and ligaments  that attach to it.

41. Oral Cavity and Pharynx Suprahyoid Infrahyoid Middle pharyngeal constrictor Hyoglossus Genioglossus Digastric Stylohyoid Geniohyoid Mylohyoid Thyrohyoid Omohyoid Sternohyoid

42. LIGAMENTS Three main  ligaments   attached to the hyoid bone Stylohyoid, Thyrohyoid, Hyoepiglottic . They support the position of the hyoid in the neck .

43. Stylohyoid ligament It extends From styloid process of temporal bone To the lesser horn of the hyoid bone .

44. Thyrohyoid membrane originates from the superior border of thyroid cartilage Attaches to the posterior surface of the hyoid bone and the greater horns .

45. Hyoepiglottic ligament Connects, Hyoid bone To anterior aspect of epiglottis .

46. FRACTURE OF THE HYOID BONE It is well protected by mandible and  cervical spine , Due to it fractures are relatively rare . Hyoid bones fractures are characteristically associated with  strangulation It is found in 1/3 of all homicides by strangulation. It is therefore a significant post-mortem finding. It is also result of  trauma , with clinical features of Pain on speaking, Odynophagia Dyspnoea .