Sinus which is not present at bih is?
**Core Concept**
The development and anatomy of paranasal sinuses is a key concept in understanding the embryology of the head and neck region. The sinuses play a crucial role in sound modification and filtering of the air we breathe. Each sinus has a distinct development timeline, with some present at birth and others developing later.
**Why the Correct Answer is Right**
The frontal sinus is the last of the paranasal sinuses to develop and is not present at birth. It begins to form around 2-5 years of age and continues to grow and develop until early adulthood. The frontal sinus is located in the frontal bone of the skull and is responsible for producing mucus that helps to humidify the air we breathe. The development of the frontal sinus is influenced by the growth of the frontal bone and the expansion of the cranial cavity.
**Why Each Wrong Option is Incorrect**
**Option A:** Sphenoid sinus - The sphenoid sinus is present at birth and begins to develop during fetal life, making it an incorrect answer. The sphenoid sinus is located in the sphenoid bone and plays a crucial role in the drainage of mucus from the nasal cavity.
**Option B:** Ethmoid sinus - The ethmoid sinus is also present at birth and consists of multiple small air cells that are located in the ethmoid bone. It is responsible for producing mucus that helps to humidify the air we breathe, making it an incorrect answer.
**Option C:** Maxillary sinus - The maxillary sinus is the largest of the paranasal sinuses and is present at birth. It is located in the maxillary bone and plays a crucial role in the drainage of mucus from the nasal cavity, making it an incorrect answer.
**Clinical Pearl / High-Yield Fact**
The development of the paranasal sinuses is influenced by the growth of the surrounding bones and the expansion of the cranial cavity. Understanding the timeline of sinus development is crucial for diagnosing and managing sinus-related disorders.
**Correct Answer:** C. Maxillary sinus is the largest of the paranasal sinuses and is present at birth.