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Now I have enough information to provide comprehensive answers to both questions.

Question 11: Arterial Supply of the Marked Region

Answer: (a) Anterior Cerebral Artery & Middle Cerebral Artery

Explanation

The image shows a medial (sagittal) view of the brain with an arrow pointing to the corpus callosum - the large white commissure connecting the two cerebral hemispheres.
The corpus callosum receives its blood supply from:
  1. Anterior Cerebral Artery (ACA) - the primary supplier. The ACA travels anteriorly and then curves posteriorly around the corpus callosum (giving rise to the pericallosal artery and callosomarginal artery). These branches supply the genu, body, and splenium of the corpus callosum from its superior surface. The A2 segment (between the anterior communicating artery and corpus callosum) gives off lenticulostriate arteries that also supply adjacent structures.
  2. Middle Cerebral Artery (MCA) - contributes via deep perforators to portions of the corpus callosum, especially in the region of the genu.
"The anterior cerebral arteries travel anteriorly and then turn posteriorly with leptomeningeal branches... A series of small lenticulostriate arteries originate from the A1 and A2 segments of the anterior cerebral artery." - Goldman-Cecil Medicine
Why not the others?
  • Option (b) ACA + PCA: The posterior cerebral artery (PCA) supplies the splenium of corpus callosum, but the primary supply is ACA + MCA.
  • Option (c) ACA + Anterior Communicating Artery: The AComA is a connecting vessel, not a direct cortical supplier.
  • Option (d) PCA + MCA: This combination does not primarily supply the corpus callosum.

Question 12: Structure Deep to the Marked Area (Dashed Circle on Skull)

Answer: (b) Lesser wing of sphenoid

Explanation

The dashed circle on the lateral skull marks the PTERION - the H-shaped sutural junction where four bones meet:
  • Frontal bone
  • Parietal bone
  • Temporal (squamous) bone
  • Greater wing of sphenoid
The pterion is the thinnest part of the skull (only ~2-3 mm thick).
Deep (internal) relations of the pterion include:
  1. Anterior division of the Middle Meningeal Artery (most clinically important - lies in a groove on the inner surface of the skull here)
  2. Superior middle cerebral vein
  3. MCA (Middle Cerebral Artery)
  4. Lesser wing of sphenoid forms part of the inner table at this region, along with the sylvian fissure
However, the question specifically asks about the structure "deep to" (endocranial surface). The lesser wing of sphenoid forms the posterior boundary of the anterior cranial fossa and the anterior clinoid process - its posterior free edge lies deep to the pterion region.
"The pterion is the region over the temple where the frontal, parietal, temporal, and sphenoid bones meet." - Neuroanatomy Through Clinical Cases, 3rd Ed.
Clinical importance of pterion:
  • A blow to this region can rupture the middle meningeal artery → extradural (epidural) hematoma
  • Pterional craniotomy is used for clipping anterior circulation aneurysms and accessing the cavernous sinus
Why not the others?
  • (a) Posterior clinoid process: Located at the dorsum sellae, far medial and posterior
  • (c) Sella turcica: The midline fossa for the pituitary gland - not related to the lateral pterion
  • (d) Carotid canal: Located in the petrous temporal bone at the skull base, medial to the pterion
The handwritten notes in the image correctly list the deep relations of the pterion: anterior division of middle meningeal artery, superior middle cerebral vessels, MCA - consistent with answer (b).
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