Paranasal sinuses present at bih ?
**Core Concept**
The paranasal sinuses are air-filled cavities within the bones of the skull, which develop from the ectodermal outpouchings of the nasal cavity. The development and maturation of these sinuses are crucial for understanding their presence at birth and throughout life.
**Why the Correct Answer is Right**
The maxillary sinuses are the only paranasal sinuses present at birth, while the frontal, anterior ethmoid, and sphenoid sinuses develop later. This is due to the gradual expansion and pneumatization of the surrounding bone. The maxillary sinuses are formed from the maxillary process, which is a part of the first pharyngeal arch. The early development of the maxillary sinuses allows for proper drainage and ventilation of the nasal cavity, facilitating normal respiratory function.
**Why Each Wrong Option is Incorrect**
**Option A:** The frontal sinuses typically begin to pneumatize around 2-3 years of age and reach full development by late adolescence.
**Option B:** The anterior ethmoid sinuses start to develop around 2-3 years of age and continue to expand throughout childhood.
**Option C:** The sphenoid sinuses begin to form around 5-6 years of age and reach full development by early adolescence.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the paranasal sinuses continue to develop and change throughout childhood and adolescence, and their anatomy can vary significantly between individuals.
**Correct Answer: A. Maxillary sinuses.