Which of the following bones of the skull gives passage to a nerve arising from the brain & x20; - INI-CET EXAM -2025

INI-CET EXAM -2025

Applied Anatomy

Medium

Appeared in: INI-CET EXAM -2025

Explanation

The image in option A is the sphenoid bone, distinguished by its unique butterfly or bat-like shape.
The sphenoid bone is a critical component of the cranial floor, forming a central wedge that articulates with many other cranial bones.
It houses numerous openings for the passage of cranial nerves. Key among these are the optic canal for the optic nerve (CN II), and the superior orbital fissure for the oculomotor (CN III), trochlear (CN IV), ophthalmic branch of the trigeminal (CN V1), and abducens (CN VI) nerves.
Other important openings include the foramen rotundum and foramen ovale, which transmit the maxillary (CN V2) and mandibular (CN V3) divisions of the trigeminal nerve, respectively.

Option B: The image shows the ethmoid bone. While it does give passage to the olfactory nerve filaments (CN I) through its cribriform plate, it transmits only one of the twelve cranial nerves.
Option C: The image shows the temporal bone. It transmits the facial (CN VII) and vestibulocochlear (CN VIII) nerves via the internal acoustic meatus. However, the sphenoid bone provides passage for a greater number of cranial nerves.
Option D: The image shows the occipital bone. It contains the foramen magnum for the spinal cord and has the hypoglossal canal for the hypoglossal nerve (CN XII). Like the other options, it is technically correct but is not the best answer as the sphenoid transmits more nerves.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy of the cranial bones and their foramina as background academic context rather than a clinical decision trigger.
Understanding the foramina of the skull base is crucial for diagnosing injuries. A fracture of the sphenoid bone can damage the optic nerve, leading to blindness, or the nerves controlling eye movement, causing double vision (diplopia) and droopy eyelids (ptosis).
Tumors at the base of the skull, such as pituitary adenomas in the sella turcica of the sphenoid, can compress nearby cranial nerves, leading to specific neurological deficits that help pinpoint the lesion's location.
What if? If a patient presents with loss of sensation in the lower jaw and difficulty chewing after a facial trauma, a fracture involving the foramen ovale in the sphenoid bone should be suspected, as this could injure the mandibular nerve (CN V3).

How to Approach the Question

First, carefully examine each image to identify the specific skull bone being depicted. Recognize their characteristic shapes: A (Sphenoid - butterfly), B (Ethmoid - complex, between orbits), C (Temporal - side of skull), D (Occipital - back/base with large hole).
Next, analyze the question, which asks for a bone that allows a nerve from the brain to pass through. This refers to cranial nerves passing through foramina.
Recall or deduce the major cranial nerves associated with each bone. You should remember that all major parts of the cranial floor have openings for nerves and vessels.
Recognize that this question has multiple technically correct answers. In such cases, you must select the 'best' or most significant answer. The bone that transmits the most or a particularly diverse set of cranial nerves is often the intended answer.
Compare the options. The sphenoid bone (A) transmits nerves for vision, eye movement, and facial sensation (CN II, III, IV, V, VI). The other bones transmit fewer nerves. Therefore, the sphenoid bone is the most comprehensive answer.

Concept Tested & Keywords

Qa7cQjMVyjBzJ2RAISe737

E6 Anatomy Applied Ashalatha 4e p. 279-281

E6 Physiology Ganong 27e Vol 2 Part 3 p. 40-42