Temporal bone : important questions and answers

 

Temporal: It is an important bone because

·       Whole internal ear

·       Whole middle ear

·       Bony part of external auditory meatus lies within it .

SN: Only cartilaginous part of external auditory meatus and auricle lies outside the temporal bone 

1.    Anatomical  point :

·       Convex squamous part is directed laterally

·       Apex of petrous part is directed medially , forward, and upward

·       Zygomatic process is directed anteriorly

2.   Morphological type : pneumatic irregular bone

3.   Ossification : both intramembranous and intracartilaginous

·       Squmous part and tympanic part is ossify from membrane

·       Rest of the temporal bone is ossify from cartilage

4.   Development :

     Petrous part of temporal bone is derived from paraxial mesoderm

    Rest of the part of temporal bone is derived from neural crest

5.    Parts: It has

Three parts:

                          i.          Squamous part

                        ii.          Petro-mastoid part

                     iii.          Tympanic part

Three processes:

It has three processes :

                          i.          Zygomatic process

                        ii.          Mastoid process

                     iii.          Styloid process

 

Squamous part : it has two surfaces

External surface: 

i)               whole external  surface is attached by origin of temporalis muscle except mandibular fossa and zygomatic process

ii)             external surface bears groove for middle temporal artery

iii)        Suprameatal triangle : a triangle just below the external auditory meatus

iv)         Importance of suprameatal triangle : mastoid antrum lies 1.25 cm deep to it

Internal surface:

Impressions of temporal lobe of cerebrum

Groove for middle meningeal artery

Squamous part has two borders

·       Superior border articulate with inferior border of parietal bone

·       Antero-inferior border : articulate with greater wing of sphenoid bone

 

Petrous part:    It has

Apex: is directed medially, forward and upwards

Base: attached with squamous and mastoid part

Petrous part : 3 borders:

1.     Anterior border: articulate with greater wing of sphenoid   

2.    Superior border:  lodges superior petrosal sinus and attachment of tentorium cerebella except medial part

3.    Posterior border:

Medial part of posterior border is lodge by inferior petrosal sinus  and

Lateral part of posterior border forms jugular foramen by articulating with condylar part of occipital bone

3 surfaces of petrous part : anterior, posterior and inferior

Anterior surface of petrous part :

1.    This surface  is irregular for sulci and gyri of temporal lobe of cerebrum

2.    Trigeminal impression ( a depressed area near the apex ): lodge trigeminal ganglion

3.    Arcuate eminence: an elevated area behind the trigeminal impression, it is caused by superior semicircular canal of internal ear

4.   Tegmen tympani:  a thin plate of bone situated in between arcuate eminence and squamous part of temporal bone.

From antero- posteriorly , tegment tympani forms

1.     Roof of tensor tympani

2.    Roof of middle ear cavity

3.    Roof of mastoid antrum

Posterior surface of petrous part of temporal bone:

Bear orifice of internal auditory meatus :  Structure passing through the foramen

Structures entrance into internal auditory meatus :

·       Motor root of facial nerve

·       Labyrinthine artery

Structures exit from the internal auditory meatus:

·       sensory root of facial nerve

·       vestibulocochlear nerve

·       labyrinthine vein

Inferior surface of petrous part of temporal bone:

From antero posteriorly

1.     Near apex: attachment of levator veli palatine muscle and cartilaginous part of auditory tube

2.    External or lower opening of carotid canal

3.    Jugular fossa

 

Mastoid part

It forms the posterior part of temporal bone. It has

Two surfaces: external and internal

Two borders: superior and posterior

1 process: mastoid process

                                               External surface of mastoid part

It is attached with following muscles: muscles are arrange from above, downwards and forwards

                          i.          Auricularis posterior

                        ii.          Origin of occipital belly of occipito frontalis muscle

                     iii.          Insertion of sternocleidomastoid

                      iv.          Insertion of splenius capitis

                        v.          Insertion of longissimus capitis

Internal surface of mastoid part

Sigmoid sulcus : a deep groove which lodge sigmoid sinus

Two borders of mastoid part  :

·       superior border articulate with inferior border of parietal bone

·       posterior border articulate with inferior border of squamous part of occipital bone

Tympanic part

·       A thin plate of bone lies between the squamous and mastoid parts

·       Anterior surface form non articular part of mandibular fossa

·       Posterior surface forms greater part of external auditory meatus

Processes of temporal bone

 

                                                                                             i.          Zygomatic process :

·       medial surface and lower border of zygomatic process give origin of masseter muscle

·       Superior border of zygomatic process attached with temporal fascia

·       Anterior end of zygomatic process articulate with temporal process of zygomatic bone

                                                                                               ii.          Mastoid process :

External surface of mastoid process is attached with

a)   Insertion of sternocleidomastoid

b)   Insertion of splenius capitis

c)    Insertion of longissimus capitis

Mastoid notch: a deep notch at the medial surface of mastoid process gives origin of posterior belly of digastric muscle

Mastoid foramen near the posterior border of mastoid part of temporal bone : it transmit an emissary vein which connect sigmoid sinus with posterior auricular vein

                                                                                                 iii.          Styloid process

Muscles:

·       origin of styloglossus,  stylohyoid and stylopharyngeus

Ligaments:

·        stylohyoid and stylomandibular ligament

Stylomastoid foramen:

·       It is situated in between mastoid process and styloid process

It transmitted

·       Facial nerve exit

·       Entrance stylomastoid branch of posterior auricular artery 

 

 

 

 

Parietal bone : important viva questions and answers

 

Parietal bone

1.      Anatomical points:

·   Superior border is longest, thickest and serrated,

·   Superior border  lies in median plane

·   External surface is convex

·    ** Anterior  inferior angle is acute and internally marked by groove for anterior  division of middle meningeal vessel 

2.      Morphological type : Flat bone

3.      Structure of bone : inner and outer table(compact bone )  and middle diploe (spongy bone)

4.      Ossification : intra membranous ossification

5.      Development : neural crest

6.      Parts:  identify

·        four borders:

a)       superior border : longest, thickest and serrated and internally marked by a sulcus known as sagittal sulcus which lodges superior sagittal sinus , Granular pit present side of sagittal sulcus which lodge arachnoid granulation

b)     inferior border irregular and serrated and internally marked by posterior division of middle meningeal artery (at the middle of inferior border )

c)      anterior and posterior border are straight and serrated

·        superior border is articulated with opposite parietal bone formed sagittal suture

·        Anterior border is articulated with frontal bone formed coranal suture

·        Posterior border is articulated with occipital bone formed lambdoid  suture

·        Inferior border is articulated with

a)      Greater wing of sphenoid bone

b)      Squamous part of temporal bone

c)       Petrous part of temporal bone .

·        What is pterion ?

·        Ans : union between four bones

a)      Frontal bone

b)     Anterior inferior angle of parietal bone

c)      Greater wing of sphenoid

d)     Squamous part of temporal bone  

e)     What is the importance of pterion ?

f)       Internal surface of pterion is lodged by anterior division of middle meningeal artery 

·        Four angles :

a)      Anterior superior angle forms bregma

b)     Posterior superior angle forms Lambda ( in children it is called pesterior frontanelle )

c)      Anterior inferior angle forms pterion and internally marked by groove for anterior division of middle meningeal artery

d)     Posterior inferior angle forms asterion and internally a groove present which lodges sigmoid sinus

External Surface of parietal bone :

·        parietal tuberosity : maximum transverse diameter of skull measures by these points

·        Superior and inferior temporal line

Internal surfaces of parietal bone :

·        impression of sulci and gyri of cerebrum

·        impression of anterior division of middle meningeal artery at internal surface of anterior inferior angle

·        impression of posterior division of middle meningeal artery at middle of inferior border

·        sagittal sulcus near the superior border

·        sulcus for sigmoid sinus near the posterior inferior angle

7.      Identify the groove for middle meningeal vessels: identify, origin of middle meningeal vessels,

8.      Through which opening, middle meningeal vessel is enter into cranial cavity? 

Ans: Foramen spinosum

 

Mandible : important viva questions and answers

 

Mandible

1.    Anatomical points

·       Horse-shoe shaped , convex body is directed forward

·       Inferior border lies horizontally

·       Rami of manbible are directed upward

2.    Morphological type: flat bone  

3.    Ossification: both intra membranous and intra cartilaginous

·       Part of ramus behind the opening of mandibular foramen is ossify from the cartilage

·       rest of the mandible is ossify from the membrane

4.    Development: neural crest

5.    Parts: body, ramus

Body:

·       Two surfaces: external and internal

·       Two borders: superior and inferior border

External surface of body of mandible:

Identify following points: 

symphysis menti

Mental protuberance

Mental tubercle

Mental foramen

External oblique line

Incisive fossa

Internal surface of body of mandible

Mylohyoid line and mylohyoid groove

Mandibular foramen and lingual

Groove for lingual nerve

Submandibular and sublingual fossa

Two upper and two lower genial tubercles

Lower border of body of mandible:

Thick and  rounded lower border of body of mandible continuous with lower border of ramus

Two Digastrics fosse are situated near the median plane

Origin of anterior belly of digastrics are attached here

Whole inferior border is attached with platysma and investing layer of deep cervical fascia

Superior border(alveolar part )  of body of mandible

It bears 16 sockes, 8 on each side  which lodge the roots of teeth

1.    Medial or 1^st incisor (I)

2.   Lateral or 2^nd incisor

3.   Canine (C)

4.   1^st premolar (P)

5.   2^nd premolar

6.   1^st molar (M)

7.   2^nd molar

8.   3^rd or last molar

Dental formula: IPCM/2123

Ramus of mandible:

Two surfaces:

Lateral surface: insertion of masseter muscle

Upper and posterior part is related with parotid gland

and medial surface :

Insertion of medial pterygoid muscle: below and behind the medial surface of mandible

mandibular foramen: transmit inferior alveolar nerve branch of mandibular nerve and inferior alveolar vessels

lingual: a sharp thin process of mandibular foraman it is attached with sphenomandibular ligament

myolohyoid groove contain myolohyoid nerve and vessels

 

4 borders :

Anterior

Posterior

Upper

Lower

Two processes

1.    Coronoid

2.   Condyloid

 

6.   Show the bony attachment of following muscles

·       Muscles of mastication:  Show their  attachment with their nerve supply

·       Buccinator, myolohyid, geniohyoid and genioglossus, anterior belly of digastrics muscle, platysma etc.

7.   Relation:

Relation of salivary glands: show the location of following gland on the bone and mention their types and nerve supply

·       Parotid gland

·       Submandibular gland

·       Sublingual gland

Relation of Nerves : show the location on the bone

·       Auriculotemporal nerve

·       Messeteric nerve

·       Marginal mandibular nerve of facial nerve

·       Lingual nerve

·       Myolohyoid nerve

8.    Foramen and structures passing through it:  

·       mandibular formamen,

·       mental foramen

9.   Joints:

1.     Temparomandibular joint (mention their type, articular surfaces, movement, peculiarity )  

2.    Dentoalveolar joint(type) ,

3.    Symphysis menti (type)