Development of Skull - NEET PG Anatomy

The development of skull is an important topic for the NEET PG exam because it provides a foundation for understanding the anatomy of the head and neck region. It is relevant for various specialties such as neurology, neurosurgery, otolaryngology, and plastic surgery, among others. Understanding the development of the skull helps diagnose and treat conditions related to the skull and face, such as congenital anomalies, trauma, and cranial neuralgias.

Therefore, it’s vital that you pay attention to this high-yield topic of anatomy for NEET PG Preparation. Read this blog further and get a quick overview of the development of skull.

• Intramembranous ossification occurs in the skull bones. Gaps between developing bones → Known as fontanelles. Fontanelles are covered by a fibrous membrane.
• Anterior fontanelle:
  • It is located between the frontal bone (anteriorly) and the parietal bone (posteriorly). It is the last to disappear. It disappears at the age of 18-24 months after birth. After fusion, a bregma suture is formed.
• Posterior fontanelle:
  • It is located between the parietal bone (anteriorly) and the occipital bone (posteriorly). It is the 1^st fontanelle to disappear. It disappears at the age of 2-3 months after birth. After fusion, lambda suture if formed.
• Posterolateral fontanelle:
  • It is also known as the mastoid fontanelle. It is located between the parietal bone (superiorly), occipital bone (posteriorly) and temporal bone (anteriorly). It is the 3^rd fontanelle to disappear. It disappears by the age of 6-18 months after birth (average → 12 months). After fusion, asterion suture is formed.
• Anterolateral fontanelle:
  • It is also known as the sphenoidal fontanelle. It is located between the frontal bone (anteriorly), parietal bone (postero-superiorly), temporal bone (postero-inferiorly) and greater wing of sphenoid (inferiorly). It is the 2^nd fontanelle to disappear. It disappears about 6 months after birth. After fusion, pterion suture is formed.

• Pterion is a H-shaped suture formed after ossification of the anterolateral fontanelle.
• Relations of the pterion:
  • Anteriorly → Frontal bone
  • Postero-superiorly → Parietal bone
  • Postero-inferiorly → Temporal bone
  • Inferiorly → Greater wing of sphenoid bone
• Pterion is the weakest point of the skull. Deep to the pterion, there is the anterior branch of the middle meningeal artery. In case of a fracture of the pterion, this anterior branch of the middle meningeal artery may get injured and bleed, leading to extradural or epidural hemorrhage.

Important Information:

• Maxillary artery is a branch of the external carotid artery.
• Middle meningeal artery is a branch of the 1^st part of maxillary artery. It divides into an anterior and a posterior branch. The anterior branch of the middle meningeal artery lies deep to the pterion.
• Middle meningeal artery enters the skull in the middle cranial fossa through the foramen spinosum.

Also Read: PHARYNGEAL ARCHES - NEET PG Anatomy

• On CT scan, we can find an ominous sign → Biconvex shadow. It is an extradural / epidural bleed → It occurs outside the dura mater. It occurs due to the collection of blood (due to bleeding from the anterior division of middle meningeal artery) deep to the pterion.
• Patients with extradural hemorrhage:
  • Lose consciousness immediately after bleed.
  • Might gain consciousness → Lucid interval
  • Once again have the loss of consciousness → And we might lose the patient.

• Pterion is also lying over another important structure → Sylvian Point
• Sylvian point is the beginning of the stem of the lateral sulcus (Sylvian sulcus) of the brain.
• Lateral sulcus separates the frontal lobe of the cerebrum from the parietal lobe of the cerebrum.

Also read:

Gametogenesis - Definition, Stages and Types - NEET PG Anatomy

Inguinal Canal & Spermatic Cord - NEET PG Anatomy

Development of the Nervous System - NEET PG Anatomy

SKULL AT BIRTH

Structures at adult size (At birth)	Structures not at adult size (At birth)
Tympanic membrane	Tegmen tympani (roof of the middle ear cavity)
Tympanic cavity	Mastoid process (appears after birth of the baby)
Ear ossicles (malleus, incus & stapes)	External ear and external auditory canal
Tympanic (mastoid) antrum	Eustachian tube
Internal ear: Cochlea, vestibule, semicircular canals	Orbit

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Also Read: Fetal Veins, Portal vein formation, Derivatives of the embryonic veins - NEET PG Anatomy