Tag: Important Facts About Osteology Of Head & Neck

Important Facts About Osteology Of Head & Neck

Important Facts About Osteology Of Head & Neck


IMPORTANT FACTS ABOUT OSTEOLOGY OF HEAD & NECK

  • The skull forms the cranial end of the axial skeleton.  It is composed of 22 bones of which 8 bones are present in calvaria (brain case) and 14 bones in facial skeleton.
  • Mandible is the only mobile bone in skull. It is the strongest bone of body.

SKULL BONES: 

  1. BONES OF CRANIUM 
  2. BONES OF FACE

 BONES OF CRANIUM  (8)                  

 PAIRED

   UNPAIRED

PARIETAL

FRONTAL

TEMPORAL

OCCIPITAL

SPHENOID

ETHMOID

BONES OF FACE (14)

PAIRED

UNPAIRED

ZYGOMATIC

MANDIBLE

MAXILLA

VOMER

NASAL

LACRIMAL

PALATINE

INFERIOR CONCHAE

  • Cribriform plate is thinnest and is a part of ethmoid.
  • Greater wing of sphenoid presents  following foramina: Foramen rotundum, foramen ovale, foramen spinosum,  canaliculus  innominatus,  and emissary sphenoidal foramen (Foramen of Vesalius).
  • Optic canal (foramen) is enclosed by lesser wing of sphenoid and body of sphenoid.
  • Emissary veins pass through-
  1. Foramen ovale and Foramen of Vesalius (emissary sphenoidal foramen): Connecting cavernous sinus with pterygoid venous plexus.
  2. Foramen coecum: From nasal mucosa to superior sagittal sinus.
  3. Anterior condylar canal (hypoglossal canal) and carotid canal: Connecting sigmoid sinus with IJV.
  4. Posterior condylar canal: Connecting sigmoid sinus with suboccipital venous plexus.
  5. Mastoid foramen: Connecting sigmoid sinus with posterior auricular or occipital vein.
  6. Parietal foramen: Connects superior sagittal sinus with scalp veins.
  7. Foramen lacerum: Connects cavernous sinus with pharyngeal venous plexus.
  • Maxillary nerve passes through foramen rotundum, pterygopalatine fossa and inferior orbital fissure to reach the orbit.
  • Arcuate eminence in petrous part of temporal bone is caused by superior semicircular canal.
  • Cartilaginous part of auditory tube (Eustachian tube) lies inferior to spheno-petrosal synchondrosis.
  • Sternberg’s canal is persistent lateral craniopharyngeal canal, lies anteromedial to foramen rotundum. It can communicate with sphenoid sinus to create a potential path of spread of infection to sphenoid sinus. Congenital intra-sphenoid meningocele and encephalocele may arise through this canal.
  • Craniofacial angle is 130 degree.
  • Dorello canal is an opening to cavernous sinus that transmits abducent nerve underneath the superior petrosal sinus.
  • Anterior fontanelle (bregma) is closed by 18 months and posterior fontanelle (lambda) by 2-6 months.
  • Cranial vault of adult is bilamellar i.e. consists of an outer table of compact bone and an inner table of compact bone. In b/w these two tables of compact bone there is intervening cancellous and vascular portion called diploe.
  • Veins draining the dipole are called diploic veins, which are valveless,with very thin wall of endothelium supported by some elastic tissue.
  • Cranial vault in unilamellar at birth without any diploe and diploic vein.
Exam Question
 
  1. The skull forms the cranial end of the axial skeleton.  It is composed of 22 bones of which 8 bones are present in calvaria (brain case) and 14 bones in facial skeleton.
  2. Mandible is the only mobile bone in skull. It is the strongest bone of body.
  3. Cribriform plate is thinnest and is a part of ethmoid.
     
  • Greater wing of sphenoid presents  following foramina: Foramen rotundum, foramen ovale, foramen spinosum,  canaliculus  innominatus,  and emissary sphenoidal foramen (Foramen of Vesalius).
  • Optic canal (foramen) is enclosed by lesser wing of sphenoid and body of sphenoid.
  • Arcuate eminence in petrous part of temporal bone is caused by superior semicircular canal.
  • Cartilaginous part of auditory tube (Eustachian tube) lies inferior to spheno-petrosal synchondrosis.
  • Clinically Sternberg’s canal is important as it is clinically associated with:Craniofacial angle is 130 degree.
  1. Infection to sphenoid sinus or cranial fossa.
  2. Congenital intrasphenoid meningocele (encephalocele).
  3. Lateral sphenoidal sinus ‘spontaneous’ CSF leak.
  • Dorello canal is an opening to cavernous sinus that transmits abducent nerve underneath the superior petrosal sinus.
  • Anterior fontanelle (bregma) is closed by 18 months and posterior fontanelle (lambda) by 2-6 months.
  • Premature closure of foramen ovale results in Right ventricular hypertrophy.
  • Maxillary bone does not articulate with Sphenoid.
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Important Facts About Osteology Of Head & Neck

IMPORTANT FACTS ABOUT OSTEOLOGY OF HEAD & NECK

Q. 1

Which of the following skull fractures is called a ‘Motorcyclist’s fracture’?

 A

Ring fracture of base of skull

 B

Hinge fracture of base of skull

 C

Comminuted fracture of skull

 D

Depressed fracture of skull

Q. 1

Which of the following skull fractures is called a ‘Motorcyclist’s fracture’?

 A

Ring fracture of base of skull

 B

Hinge fracture of base of skull

 C

Comminuted fracture of skull

 D

Depressed fracture of skull

Ans. B

Explanation:

Hinge fracture is also known as motor cyclist’s fracture.

Ref: The Essentials of Forensic Medicine and Toxicology By Dr K S Narayan Reddy, 28th Edition, Page 211; Guide to Forensic Medicine and Toxicology By B. Jain, 2004, Page 98; Oxford Handbook of Forensic Medicine By Jonathan P. Wyatt, Page 145; Lawyers Guide to Forensic Medicine By Bernard Knight, 2nd Edition, Page 202


Q. 2

Which of the measurement correlates with the sub occipitofrontal diameter of fetal skull?

 A

9.4 cm

 B

10 cm

 C

11.3 cm

 D

12 cm

Q. 2

Which of the measurement correlates with the sub occipitofrontal diameter of fetal skull?

 A

9.4 cm

 B

10 cm

 C

11.3 cm

 D

12 cm

Ans. B

Explanation:

Sub Occipitofrontal diameter is measured from below the occipital protuberance to the centre of the sinciput. It measures 10cm. It is the diameter which distends the vulva in a normal vertex presentation.
 
Diameters of fetal skull:
  • Occipitofrontal: It follows a line extending from a point just above the root of the nose to the most prominent portion of the occipital bone. 11.5cm
  • Biparietal : It is the greatest transverse diameter of the head, which extends from one parietal boss to the other. 9.5cm.
  • Bitemporal: It  is the greatest distance between the two temporal sutures. 8cm.
  • Occipitomental: It extends from the chin to the most prominent portion of the occiput. 12.5cm.
  • Suboccipitobregmatic: It  follows a line drawn from the middle of the large fontanel to the undersurface of the occipital bone just where it joins the neck. 9.5cm.
Ref: Midwifery  By Pauline M. Sellers pag 111. , Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 4. Fetal Growth and Development. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.

Q. 3

Which is the longest diameter of fetal skull?

 A

Biparietal

 B

Bitemporal

 C

Occipitomental

 D

Mentovertical

Q. 3

Which is the longest diameter of fetal skull?

 A

Biparietal

 B

Bitemporal

 C

Occipitomental

 D

Mentovertical

Ans. D

Explanation:

Mentovertical is the distance between the tip of the mentum or chin and the most distant point of the vertex. It is the longest diameter of the fetal skull and is 14cm long. It is the diameter of engagement in a brow presentation.
 
Diameters of fetal skull:
  • Occipitofrontal: It follows a line extending from a point just above the root of the nose to the most prominent portion of the occipital bone. 11.5cm
  • Biparietal: It is the greatest transverse diameter of the head, which extends from one parietal boss to the other. 9.5cm.
  • Bitemporal: It  is the greatest distance between the two temporal sutures. 8cm.
  • Occipitomental: It extends from the chin to the most prominent portion of the occiput. 12.5cm.
  • Suboccipitobregmatic: It  follows a line drawn from the middle of the large fontanel to the undersurface of the occipital bone just where it joins the neck. 9.5cm.
Ref: Clinical Obstretics (10Th Edn.)  By S. Gopalan,  page 66, Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 4. Fetal Growth and Development. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.

Q. 4

About skull of newborn, all of the following statements are TRUE, EXCEPT:

 A

Paranasal sinuses are absent

 B

Absent diploic spaces

 C

Middle ear ossicles are of same size as in adults

 D

Mastoid process is not completely formed

Q. 4

About skull of newborn, all of the following statements are TRUE, EXCEPT:

 A

Paranasal sinuses are absent

 B

Absent diploic spaces

 C

Middle ear ossicles are of same size as in adults

 D

Mastoid process is not completely formed

Ans. A

Explanation:

All paranasal sinuses are present to varying degrees in newborn. Ethmoid sinuses are first to fully develop followed in order by maxillary, sphenoid and frontal sinuses. 
 
The auditory ossicles malleus, incus and stapes reach the adult size as early as sixth month of fetal life. The oval window and round window are the same size in the newborn infant as in the adult. The tympanic membrane completes its full growth by birth. 
 
Mastoid process is not completely formed by birth, so the facial nerve coming out of the stylomastoid foramen is not protected by the mastoid process. Hence it can be pressed by forceps in case of forceps delivery leading to temporary facial paralysis.
 

Q. 5

Skull consists of….bones­

 A

20

 B

22

 C

24

 D

28

Q. 5

Skull consists of….bones­

 A

20

 B

22

 C

24

 D

28

Ans. B

Explanation:

B i.e. 22 


Q. 6

Skull of a male differs from that of a female by all of the following except:

 A

Capacity greater than 1500 c.c

 B

Muscular markings over occiput are less marked

 C

Orbits square

 D

Frontal eminence small

Q. 6

Skull of a male differs from that of a female by all of the following except:

 A

Capacity greater than 1500 c.c

 B

Muscular markings over occiput are less marked

 C

Orbits square

 D

Frontal eminence small

Ans. B

Explanation:

B i.e. Muscular markings over occipit are less marked


Q. 7

Shortest skull diameter:  

March 2013

 A

Biparietal

 B

Mentovertical

 C

Bitemporal

 D

Bimastoid

Q. 7

Shortest skull diameter:  

March 2013

 A

Biparietal

 B

Mentovertical

 C

Bitemporal

 D

Bimastoid

Ans. D

Explanation:

Ans. D i.e. Bimastoid

Fetal skull

  • Shortest diameter of fetal skull: Bimastoid (7.5 cm)
  • Largest diameter of fetal skull: Mentovertical (14 cm)

Q. 8

Caucasian skull is:

BHU 10

 

 A

Elongated

 B

Square

 C

Narrow

 D

Round

Q. 8

Caucasian skull is:

BHU 10

 

 A

Elongated

 B

Square

 C

Narrow

 D

Round

Ans. D

Explanation:

Ans. Round


Q. 9

Sylvian point is related to ‑

 A

Squamous part

 B

Petrous part

 C

Tympanic part

 D

Mastoid part

Q. 9

Sylvian point is related to ‑

 A

Squamous part

 B

Petrous part

 C

Tympanic part

 D

Mastoid part

Ans. A

Explanation:

Ans. is ‘a’ i.e., Squamous part

The pterion is situated in the floor of temporal fossa.

It is an H-shaped suture, where four bones meet each other :‑

i) Greater wing of sphenoid

ii) Squamous temporal

iii) Frontal

iv) Anterioinferior angle of parietal

Central point of pterion is known as Sylvian point. the cranium is very thin ” at this point. Its immediate deep relations are frontal branch of middle meningeal artery, its accompanying vein and stem of lateral sulcus of brain. Fracture at this point may injure middle meningeal artery or/and vein and give rise to extradural hemorrhage.


Q. 10

Point (arrow) shown in the skull depicts: 

 A

Inion

 B

Stephanion

 C

Pterion

 D

Bregma

Q. 10

Point (arrow) shown in the skull depicts: 

 A

Inion

 B

Stephanion

 C

Pterion

 D

Bregma

Ans. C

Explanation:

Ans:C.)Pterion.

Pterion

  • It is located in the temporal fossa.
  • It is the junction between four bones:
    • the parietal bone
    • the squamous part of temporal bone
    • the greater wing of sphenoid bone
    • the frontal bone.
  • The pterion is known as the weakest part of the skull.
  • The anterior division of the middle meningeal artery runs underneath the pterion. Consequently, a traumatic blow to the pterion may rupture the middle meningeal artery causing an epidural haematoma.

Bregma

  • The bregma is located at the intersection of the coronal suture and the sagittal suture on the superior middle portion of the calvaria. It is the point where the frontal bone and parietal bones meet.The bregma is known as the anterior fontanelle during infancy.

Inion

  • The inion is the tip of external occipital protuberance, the midline bony prominance in the occipital bone where the ligamentum nuchae and trapezius muscle attaches.

Stephanion

  • The point where the upper temporal line cuts the coronal suture is named the stephanion.

Q. 11

Metopic sutures closes at ‑

 A

6 months

 B

3 yrs

 C

6 yrs

 D

60 yrs

Q. 11

Metopic sutures closes at ‑

 A

6 months

 B

3 yrs

 C

6 yrs

 D

60 yrs

Ans. C

Explanation:

Ans. is ‘c’ i.e., 6 years 

Infant’s skull consists of following sutures :-

  1. Coronal suture
  2. Saggital suture
  3. Lambdoid suture
  4. Metopic suture (median frontal suture).
  • Coronal suture: This is placed between the frontal bone and the two parietal bones. The suture crosses the cranial vault from side to side and runs downwards and forwards.
  • Sagittal suture: It is placed in the median plane between the two parietal bones.
  • Lambdoid suture: It lies posteriorly between the occipital and the two parietal bones, and it runs downwards and forwards across the cranial vault.
  • Metopic suture: This is occasionally present in about 3 to 8% individuals. It lies in the median plane and separates the two halves of the frontal bone. Normally it fuses at 6 years of age.

Q. 12

Mobile bone of skull ‑

 A

Maxilla

 B

Mandible

 C

Ethmoid

 D

Sphenoid

Q. 12

Mobile bone of skull ‑

 A

Maxilla

 B

Mandible

 C

Ethmoid

 D

Sphenoid

Ans. B

Explanation:

Ans. is ‘b’ i.e., Mandible 


Q. 13

Dorello’s canal transmits in tip of temporal bone

 A

Middle maningeal artery

 B

Mandibular nerve

 C

Superior alveolar branch of maxillary

 D

Abducent nerve

Q. 13

Dorello’s canal transmits in tip of temporal bone

 A

Middle maningeal artery

 B

Mandibular nerve

 C

Superior alveolar branch of maxillary

 D

Abducent nerve

Ans. D

Explanation:

Dorello canal is an opening to cavernous sinus that transmit abducent nerve underneath the superior petrosal sinus.


Q. 14

All of the following tatements about Sternberg canal are true, Except?

 A

Located anterior & medial to Foramen Rotundum

 B

Located posterior & lateral to Foramen Rotundum

 C

Represents persistant craniopharyngeal canal

 D

Cause of intrasphenoidal meningocele

Q. 14

All of the following tatements about Sternberg canal are true, Except?

 A

Located anterior & medial to Foramen Rotundum

 B

Located posterior & lateral to Foramen Rotundum

 C

Represents persistant craniopharyngeal canal

 D

Cause of intrasphenoidal meningocele

Ans. B

Explanation:

Sternberg’s canal (persistent lateral craniopharyngeal canal)

  • Originally described by Sternberg in 1888 and was reported to be constantly present in children at the age of 3-4 yrs. He described an incudence of 4% in adults.
  • It is caused by incomplete fusion of greater wing of sphenoid with presphenoid at a point where primordial sphenoid portions fuse.
  • It lies anterior & medial to foramen rotundum in parasellar region in middle cranial fossa.
  • It can communicate with sphenoid sinus, pterygopalatine fossa, nasopharynx, or pass straight through the bone to emerge at the base of skull.
  • Clinically Sternberg’s canal is important as it is clinically associated with:Craniofacial angle is 130 degree.
    1.  Infection to sphenoid sinus or cranial fossa.
    2.  Congenital intrasphenoid meningocele (encephalocele).
    3.  Lateral sphenoidal sinus ‘spontaneous’ CSF leak.

 




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