Osteology Question and Answers

Norma Verticalis

Question 1. Anterior fontanelle.
Answer:

Coronal suture:

• This is placed between frontal Lone and the two parietal bones

Sagittal suture:

• It is placed between two parietal bone

Read And Learn More: BDS Previous Examination Question And Answers

Significance:

• It closes at 18 months of age
• It allows growth of brain
• If fontanelles fuse early, brain growth is stunted
• If anterior fontanelle is bulging, there is raised intracranial pressure
• If fontanelle is depressed, it shows decreased intracranial pressure
• This indicates dehydration
• During parturition, it helps to determine the position of vertex

Question 2. Metopic suture

Answer:

• It has a rare occurrence

Site:

• It lies in the median plane
• It separates the two halves of the frontal bone

Incidence:

• This is occasionally present in about 3-8 % individuals

Question 3. Name the bones meeting at bregma
Answer:

• Two parietal bones and
• Frontal bone and

Question 4. Anterior fontanelle.
Answer:

Coronal suture:

• This is placed between frontal bone and the two parietal

bones Sagittal suture:

• It is placed between two parietal bone

Anterior fontanelle:

• It is a meeting point between the coronal and sagittal suture

Norma Occipitalis

Question 1. External occipital protuberance
Answer:

Site:

• It is an median prominence in the lower part of norma occipitalis

Significance:

• It marks the junction of the head and neck
• The most prontinent part of it is inion
• It is easily felt at the point where the back of the neck becomes continuous with the scalp

Attachments:

• Upper part
• Gives origin to the trapezius

Lower part:

• Gives attachment to the upper end of the ligamentum nuchae.

Question 2. Superior nuchal lines
Answer:

• They are curved bony ridged passing laterally from the external occipital protuberance

Attachments:

• Medial one-third: gives origin to trapezius
• Lateral part: provides insertion to sternocleidomastoid above and splenius capitis below

Question 3. Superciliary arch
Answer:

Location & Appearance:

• It is a rounded, curved elevation situated just above the medial part of each orbit
• Prominent in males

Attachments:

• Medial part: gives origin to corrugators supercilli

Normal Lateralis

Question 1. Mastoid process.
Answer:

• It is nipple-like large projection from the lower part of the mastoid temporal bone
• It forms lateral wall of mastoid notch

Location:

• Posteroinferior to the external acoustic meatus

Occurrence:

• During 2nd year of life

Structures Present:

• Tympanomastoid fissure: on the anterior aspect of the base of mastoid process
• Mastoid foramen: at near occipitomastoid suture

Structures Attached:

• Sternocleidomastoid, splenius capitus & longissimus capitus inserted from before backwards on posterior part of lateral surface of mastoid process
• Posterior belly of digastrics – from mastoid notch

Relations:

1. Tympanomastoid fissure

1. Transmits auricular branch of vagus nerve

2. Mastoid foramen – transmits

1. Emissary vein connecting the sigmoid sinus with the posterior auricular vein
2. Meningeal branch of occipital artery

Question 2. Give the position, connection and branches of pterygopalatine ganglion.
Answer:

Pterygopalatine Ganglion:

Situation:

It is the largest parasympathetic ganglion

Branches:

Connections:

Question 3. Zygomatic arch
Answer:

• It is horizontal bar

Location:

• Sympathetic root

Formation:

• Anterior 1/3rd: by the temporal process of zygomatic bone
• Posterior 2/3rd: by zygomatic process of temporal bone

Parts:

• Jugal point: At the anterior end of upper border
• Anterior & posterior root: At the posterior end
• Articular tubercle: At the junction of anterior & posterior root
• Postglenoid tubercle: Behind the articular fossa

Attachments:

Temporal fascia: Outer & inner parts of superior border of arch

Masseter: To the medial & lower border of arch

Lateral ligament of TMJ: To tubercle of root of arch

Question 4. Pterion
Answer:

• It is H-shaped suture present in the anterior part of the floor of temporal fossa
• It is meeting point of four bones
  • Frontal
  • Parietal
  • Greater wing of sphenoid
  • Temporal

Location:

• 4 cm above the midpoint of zygoma
• 2.5 cm behind the frontozygomatic suture

Relations:

• Structures related to it are:
  • Middle meningeal vein
  • Anterior division of the middle meningeal artery
  • Stem of the lateral sulcus of brain

Question 5. Name bones meeting at pterion
Answer:

• Frontal
• Parietal
• Greater wing of sphenoid
• Temporal

Question 6. Surgical importance of pterion
Answer:

• Pterion is the thin part of skull
• In road side accidents, the anterior division of middle meningeal artery may be ruptured leading to clot formation between the skull bone & the duramater or extradural haemorrhage

Result:

• Clot compresses the motor area of brain leading to paralysis of the opposite side

Prevention: Use of helmet

Question 7. Mastoid process
Answer:

• It is nipple-like large projection from the lower part of the mastoid temporal bone
• It forms lateral wall of mastoid notch

Location:

• Posteroinferior to the external acoustic meatus

Occurrence:

• During 2nd year of life

Structures Present:

Tympanomastoid fissure: On the anterior aspect of the base of mastoid process

Mastoid foramen: At/ near occipitomastoid suture

Structures Attached:

• Sternocleidomastoid, splenius capitus & longissimus capitus- inserted from before backwards on posterior part of lateral surface of mastoid process
• Posterior belly of digastrics – from mastoid notch

Question 8. Name muscles attached to mastoid process.
Answer:

• Sternocleidomastoid, splenius capitus & longissimus capitus- inserted from before backwards on posterior part of lateral surface of mastoid process
• Posterior belly of digastrics – from mastoid notch

Question 9. Mastoid groove
Answer:

• The mastoid part of the temporal bone lies just behind the external acoustic meatus
• It is continuous with the squamous temporal bone
• A partially obliterated squamomastoid suture may be visible just in front of & parallel to the roughened area of muscular insertions known as mastoid groove.

Question 10. Stylomastoid foramen
Answer:

Location:

• It is located posterior to the styloid process

Structures passing through it:

• Facial nerve
• Stylomastoid branch of posterior auricular foramen

Question 11. Piriform fossa/ piriform recess
Answer:

• It is a small cavity or pocket between the lateral walls of the pharynx on each side & upper part of the larynx
• It is also called Pyriform fossa or Pyriform sinus

Question 12. Suprameatal triangle of McEwan’s
Answer:

• Suprameatal triangle is small depression present posteroinferior to the external auditory meatus.
• It forms the lateral wall of the tympanic or mastoid antrum.

Boundaries:

• Superior – supramastoid crest
• Anterior – posteriosuperior margin of the external auditory meatus
• Posterior – vertical tangent to the posterior margin of the meatus.

Norma Basalis

Question 1. Foramen magnum
Answer:

• Foramen magnum is largest foramen of the skull
• Opens into posterior cranial fossa-upwards and into vertebral canal- downward
• It is oval in shape
• It is overlapped on each side by the occipital condyles

Structures Passing Through It:

• Anterior part-3 structures
  • Apical ligament of dens
  • Vertical band of cruciate ligament
  • Membrana tectoria
• Posterior part-2 structures
  • Lower part of medulla oblongata
  • 3 meninges
• Through subarachnoid space- 9 Structures
  • Spinal accessory nerves -2
  • Vertebral arteries – 2
  • Sympathetic plexus around the vertebral arteries -2
  • Posterior spinal arteries – 2
  • Anterior spinal artery – 1

Question 2. Structures passing through foramen magnum
Answer:

• Anterior part-3 structures
  • Apical ligament of dens
  • Vertical band of cruciate ligament
  • Membrana tectoria
• Posterior part-2 structures
  • Lower part of medulla oblongata
  • 3 meninges
• Through subarachnoid space-9 Structures
  • Spinal accessory nerves -2
  • Vertebral arteries – 2
  • Sympathetic plexus around the vertebral arteries -2
  • Posterior spinal arteries – 2
  • Anterior spinal artery – 1

Question 3. Foramen of middle cranial fossa
Answer:

Question 4. Diploic veins
Answer:

• The diploic veins are large, thin-walled valveless veins that channel in the diploë between the inner and outer layers of the cortical bone in the skull.
• They develop fully by the age of two years.
• The diploic veins drain this area into the dural venous sinuses.
• The four major types of diploic veins found on each side of the head are frontal, anterior temporal, posterior temporal, and occipital diploic veins.

Types:

Question 5. Auditory tube
Answer:

• The auditory tube connects the middle ear with the nasopharynx anteriorly
• The sulcus tube which is a groove between the posteromedial margin of the greater wing of the sphenoid & the petrous temporal bone lodges the cartilaginous part of the auditory tube

Question 6. Pterygomaxillary fissure
Answer:

• It is a triangular interval formed by the divergence of the maxilla from the pterygoid process of the sphenoid
• It connects infratemporal with the Pterygopalatine fossa
• It transmits terminal part of internal maxillary artery

Question 7. pterygopalatine fossa.
Answer:

Location:

• Lies deep to the pterygomaxillary fissure

Boundaries:

1. Anterior
   • Posterior surface of maxilla
2. Posterior
   • Pterygoid process
   • Greater wing of sphenoid
3. Medial
   • Perpendicular place of palatine bone
4. Floor
   • Union of anterior & posterior walls

Contents:

• Maxillary nerve & its branches
• 3rd part of maxillary artery & its branches
• Pterygopalatine ganglion with its branches

Question 8. Name contents of pterygopalatine fossa
Answer:

3 contents:

• Maxillary nerve & its branches
• 3rd part of maxillary artery & its branches
• Pterygopalatine ganglion with its branches

3 ganglion:

• Sphenopalatine
• Pterygopalatine
• Ganglion of hay fever

3 structures transversing in posterior wall:

• Maxillary nerve
• Nerve of pterygoid canal
• Pharyngeal branch through pterygoid canal

3 structures passing through inferior orbital fissure

• Infraorbital nerve
• Zygomatic nerve
• Orbital branches of the ganglion

3 structures through inferior opening:

• Anterior palatine nerve & greater palatine vessels
• 2 Posterior palatine nerve & lesser palatine vessels

3 structures through medial opening:

• Nasopalatine nerve & sphenopalatine vessels
• Medial posterosuperior nasal branches
• Lateral posterosuperior nasal branches

3 roots of the ganglion:

• Sensory
• Sympathetic
• Secretomotor

Question 9. Pterygopalatine ganglion
Answer:

• It is largest parasympathetic ganglion

Roots:

Branches:

• Posteriorly, the groove leads to the bony part of the auditory tube, which lies within the petrous temporal bone

Parts:

1. Osseous part-36 mm long
2. Fibro-cartilaginous part-24 mm long

Arterial Supply:

• Middle meningeal artery
• Artery of the pterygoid canal
• Ascending pharyngeal branch of external carotid artery

Venous Drainage:

• Pterygoid & pharyngeal Venous plexus

Function:

• Maintains equilibrium of air pressure

Question 10. Foramen magnum
Answer:

• Foramen magnum is largest foramen of the skull
• Opens into posterior cranial fossa-upwards and into vertebral canal- downward
• It is oval in shape
• It is overlapped on each side by the occipital condyles

Question 11. Jugular foramen
Answer:

• It is large & elongated.
• It is placed at the posterior end of the petro-occipital suture

Structures passing through it:

• Anterior part:
  • Inferior petrosal sinus
  • Meningeal branch of ascending pharyngeal artery
• Middle part:
  • Glossopharyngeal nerve
  • Vagus nerve
  • Accessory nerve
• Posterior part:
  • Internal jugular vein
  • Meningeal branch of occipital artery

Question 12. Foramen lacerum.
Answer:

• It is short, wide canal, 1 cm long
  • Bounded by
• Posterolaterally: by apex of the petrous temporal bone
• Medially:
  • Basiocciput
  • Body of the sphenoid
• Anteriorly
  • Root of the pterygoid process
  • Greater wing of the sphenoid bone

Structures passing through it:

• Lower part
  • Meningeal branch of ascending pharyngeal artery
  • Emissary vein
• Upper part
  • Internal carotid artery
  • Venous & sympathetic plexuses around it
• Anterior part
  • Nerve of the pterygoid canal

Question 13. Superior orbital fissure
Answer:

• It is situated at the posterior part of the junction between the roof & lateral wall of the orbit
• It is an oblique, roughly triangular space bounded
  • Above by the lesser wing
  • Below by the greater wing
  • Medially by the body of the sphenoid

Structures passing through it:

• Lateral part:
  • Nerves: lacrimal, frontal, trochlear
  • Vein: superior ophthalmic
  • Arteries: meningeal branch of lacrimal artery, anastomotic branch of middle meningeal artery
• Middle part:
  • Upper & lower division of oculumotor nerve
  • Nasociliary nerve
  • Abducent nerve
• Medial part:
  • Inferior ophthalmic vein
  • Sympathetic nerves from the plexus around internal carotid artery

Question 14. Structures passing through foramen ovale
Answer:

Male:

• Mandibular nerve
• Accessory meningeal artery
• Lesser petrosal nerve
• Emissary vein

Question 15. Structures passing through foramen spinosum
Answer:

Structures passing through foramen spinosum are:

• Middle meningeal artery
• Meningeal branch of mandibular nerve
• Posterior trunk of middle meningeal vein

Question 16. Structures passing through superior orbital fissure
Answer:

• Lateral part
  • Nerves: lacrimal, frontal, trochlear
  • Veins: superior ophthalmic
  • Arteries: meningeal branch of lacrimal artery, anastomotic branch of middle meningeal artery
• Middle part
  • Upper and lower division of oculomotor nerve
  • Nasociliary nerve
  • Abducent nerve
• Medial part
  • Inferior ophthalmic vein
  • Sympathetic nerves from the plexus around internal carotid artery

Question 17. Structures passing through anterior condylar canal
Answer:

• Hypoglossal nerve
• Meningeal branch of the hypoglossal nerve
• Meningeal branch of ascending pharyngeal artery
• Emissary vein

Question 18. Foramen ovale
Answer:

• Foramen ovale is large and oval in shape

Location:

Posterolateral to the upper end of the posterior border of lateral pterygoid plate

Structures passing through it:

Male:

• Mandibular nerve
• Accessory meningeal artery
• Lesser petrosal nerve
• Emissary vein

Cervical Vertebrae

Question 1. Atlanto-occipital joint
Answer:

• Altanto-occipital joint is synovial joint

Articular surfaces:

• Above-occipital condyles
• Below-superior anterior facets of the atlas vertebrae

Ligaments:

• Fibrous capsule
  • Surrounds the joint
• Anterior atlanto-occipital membrane
  • Extends from anterior margin of the foramen magnum to the upper border of the anterior arch of the atlas
• Posterior atlanto-occipital membrane
  • Extends from posterior margin of the foramen magnum to the upper border of the posterior arch of the atlas

Arterial supply:

• Vertebral artery

Nerve supply:

• First cervical nerve

Movements:

• Flexion- around transverse axis
• Extension around transverse axis
• Lateral bending – around anteroposterior axis

Question 2. Atlanto-axial joint
Answer:

Types of joint:

Ligaments:

• Laterally
  • Capsular ligament
  • Lateral part of the anterior longitudinal ligament
  • Ligamentum flavum
• Medially
  • Loose capsular ligament
  • Transverse ligament

Movements:

• Rotatory around a vertical axis

Significance:

• Cruciate ligament of median atlantoaxial joint ruptures in judicial hanging

Question 3. Dens.
Answer:

• It is the typical feature of second cervical vertebrae called axis

Appearance:

• It is strong tooth-like process projecting upwards from the body of axis

Significance:

• It represents the centrum of atlas which has fuse with centrum of axis
• Death in execution by hanging is due to dislocation of dens following rupture of transverse ligament of dens

Relations:

• Superior surface of body of axis fuses with dens
• Easch side is encroached by superior articular facets

Surfaces:

• Inferior surface: Has prominent anterior margin
• Anterior surface: Has median ridge on each side

Attachments:

Anteriorly: Articulates with anterior arch of atlas

Posteriorly: With transverse ligament of atlas

At apex: Provides attachment to apical ligament

On each side below apex: To alar ligament

Question 4. Typical features of atlas
Answer:

• It is ring shaped

• It has following features
  • Short anterior arch marked by medial anterior tubercle
  • Long posterior arch forming 2/5th of the ring
  • Lateral masses
• Its upper & lower surfaces bears superior articular facet & inferior articular facet
  • Transverse process
• It can be felt on the surface of the neck between angle of mandible & mastoid process

Question 5. Altlanto-occipital joint
Answer:

• Altanto-occipital joint is synovial joint

Articular surfaces:

• Above occipital condyles
• Below-superior anterior facets of the atlas vertebrae.

Ligaments:

• Fibrous capsule
• Anterior atlanto-occipital membrane
• Posterior atlanto-occipital membrane

Arterial supply:

• Vertebral artery

Nerve supply:

• First cervical nerve

Movements:

• Flexion – around transverse axis
• Extension – around transverse axis
• Lateral bending – around anteroposterior axis

Question 6. Atlanto-axial joint
Answer:

• It is joint between atlas and axis vertebrae

Ligaments:

• Laterally
  • Capsular ligament
  • Lateral part of the anterior longitudinal ligament
  • Ligamentum flavum
• Medially
  • Loose capsular ligament
  • Transverse ligament

Movements:

• Rotatory around a vertical axis

Question 7. Foramen transversarium
Answer:

• Foramen transversarium is specific to cervical vertebrae
• Anterior and posterior tubercles are on either side of the foramen on each tranverse process
• Anterior tubercle on sixth vertebrae is called carotid tubercle
• It separates carotid artery from vertebral artery

Relations:

• Foramen transversarium transmits
  1. Vertebral artery
  2. Vertebral veins
  3. Branch from the inferior cervical ganglion
• Anterior tubercle gives origin to
  1. Scalenus anterior
  2. Longus capitis
  3. Oblique part of longus colli
• Posterior tubercle gives origin to
  • Scalenus medius
  • Scalenus posterior
  • Levator scapulae
  • Splenius cervicis
  • Longissimus cervicis
  • Iliocostalis cervicis

Question 6. Features of axis vertebrae
Answer:

• Axis is the second cervical vertebra
• It is identified by dens or odontoid process, typical feature of it

Surfaces:

• Superior surface of body – fused with dens
• Inferior surface – Has prominent anterior margin, Presents inferior vertebral notch
• Anterior surface – has median ridge on each side

Features:

• Pedicle – overlapped by superior articular processes
• Laminae – thick and strong
• Articular facets – large, flat and circular, overhangs foramen transversarium
• Transverse processes – very small
• Spine- large, thick and very strong

Maxilla

Question 1. Maxilla
Answer:

• It is second largest bone of the face
• It is paired bone
• It contributes in the formation of face, nose, mouth, orbit, infratemporal and pterygopalatine fossa

Features:

• It is pyramidal in shape
• Apex is directed medially & base directed laterally

Surfaces:

Hyoid Bone

Question 1. Hyoid bone- general features, attachments and development
Answer:

General features:

• It is U-shaped bone
• Location
  • In the anterior midline of the neck between the chin and thyroid cartilage

Parts:

• Body-central part
  • Has anterior and posterior surfaces
  • Has upper and lower borders
• Greater cornua
  • Flattened from above downwards
  • Has upper and lower surfaces, medial and lateral border and a tubercle
• Lesser cornua
  • These are small conical pieces of bone projecting from junction of the body and greater cornua

Attachments:

Development:

 

Question 2. Hyoid bone
Answer:

• It is U-shaped bone

Location:

• In the anterior midline of the neck between the chin and thyroid cartilage

Parts:

• Body- central part
• Greater cornua
• Lesser cornua

Development:

Question 3. Muscles attached to hyoid bone
Answer:

Question 4. Body of hyoid bone
Answer:

• It is central part of hyoid bone
• Has anterior and posterior surfaces
• Has upper and lower borders

Attachments:

Mandible

Question 1. Ramus of mandible
Answer:

• It is quadrilateral in shape
• It extends vertically upwards from posterior part of body

Surfaces:

1. Lateral
   • It is flat & bears a number of oblique ridges
2. Medial
   • It presents mandibular foramen which leads to mandibular canal
   • Anterior margin of it contains tongue shaped projection called lingula
   • Mylohyoid groove begins just below mandibular foramen

Borders:

1. Upper border

• It is thin & curved downwards
• It contains condylar and coronoid process
• Mandibular notch lies between them

1. Condylar process
   • Its upper expanded part called head joins with fossa of temporal bone to form temporomandibular joint
   • Constriction below it is called neck
   • Its anterior end presents a depression called the pterygoid fovea
2. Coronoid process
   • It is flat triangular upward projection

2. Lower border

• It is continuous with base of mandible
• Junction between lower & posterior border forms angle of mandible

3. Anterior border

• It is thin

4. Posterior border

• It is thick

Attachments:

Question 2. Relations of ramus of mandible
Answer:

Muscles Related to Ramus of Mandible:

Nerves related to ramus of mandible:

Vessels Related to Ramus of Mandible:

Question 3. Pterygomandibular raphe
Answer:

• It is ligamentous band of the buccopharyngeal fascia

Question 4. Ligaments of mandible
Answer:

1. Sphenomandibular ligament

Location:

• It lies on the deep plane away from the fibrous capsule of TMJ

Attachments:

• Superiorly to the spine of sphenoid
• Inferiorly to the lingula of mandibular foramen

2. Stylomandibular ligament

Extend:

• From lateral surface of the styloid process of temporal bone
• Up to angle and adjacent parts of posterior border of the ramus of mandible

Question 5. Name four arteries related to the ramus of the mandible
Answer:

• Maxillary artery
• Superior temporal artery
• Massetric artery
• Inferior alveolar artery
• Mylohyoid artery
• Mental artery
• Facial artery

Question 6. Name the attachments of pterygomandibular raphe
Answer:

The pterygomandibular raphe is attached immediately behind the third molar tooth in continuation with the origin of the superior constrictor

• Muscles attached to it are:
  • Superior constrictor muscle of pharynx
  • The buccinator muscle

Question 7. Ligaments attached to the surface of mandible
Answer:

• Sphenomandibular ligament
• Lateral ligament of temporomandibular joint

Question 8. Stylomandibular ligament
Answer:

• It is accessory ligament of temporomandibular joint
• It is derived from investing layer of deep cervical fascia

Extend:

• From lateral surface of the styloid process of temporal bone
• Up to angle & adjacent parts of posterior border of the ramus of mandible

Question 9. Sphenomandibular ligament
Answer:

• It is accessory ligament of TMJ
• It is remnant of dorsal part of Meckel’s cartilage

Location:

• It lies on a deep plane away from the fibrous capsule of TMJ

Attachments:

• Superiorly: To the spine of sphenoid
• Inferiorly: To the lingua of mandibular foramen

Relations: It is related

• Laterally to
  • Lateral pterygoid muscle
  • Auriculotemporal nerve
  • Maxillary artery
• Medially to
  • Chorda tympani nerve
  • Wall of pharynx

Question 10. Significance of Pyriform fossa
Answer:

• Pyriform fossa lies between quadrate membrane & medial side of thyroid cartilage
• It is transverse by internal laryngeal nerve
• It is used to smuggle out precious stones, diamonds, etc
• Thus it is called smuggler’s fossa
• Tumours in it causes dysphagia

Question 11. Name the bones ossified in the membrane
Answer:

• Frontal Parietal
• Temporal
• Mandible
• Palatine
• Nasal
• Vomer
• Zygomatic
• Maxilla

Question 12. Name different types of sutural joints
Answer:

• Based on the structure of their articular surfaces, there are 5 types of sutural joints:
  1. Plane suture
  2. Squamous suture
  3. Serrate suture
  4. Denticulate suture
  5. Schindylesis

Question 13. Laws of ossification
Answer:

Ossification occurs by two processes

1. Endochondrial ossification

• It involves cartilage as precursor
• Example: healing of fractures treated with plaster of Paris

2. Intramembranous ossification

• It is direct laying down of bone into the primitive connective tissue
• Example: healing of fractures treated with open reduction and internal fixation

Question 14. 4 nerves related to mandible.
Answer:

Question 15. Name any four muscles attached to ramus of mandible.
Answer: