Developmental Anatomy — MCQs

Developmental Anatomy Indian Medical PG Practice Questions and MCQs

Question 91: Root completion of permanent teeth occurs:

A. 1-1½ years after eruption
B. 2-3 years after eruption (Correct Answer)
C. 6 months after eruption
D. None of the options

Explanation: **2-3 year after eruption** - **Root development** continues for approximately **2 to 3 years** after a permanent tooth erupts into the oral cavity. - During this period, the **root canal space narrows** due to further deposition of dentin, and the **apical foramen closes**. *1-1 ½ year after eruption* - This timeframe is generally too short for complete **apical closure** and **root maturation** of most permanent teeth. - While significant development occurs, the final stage of **root completion** typically extends beyond 1.5 years post-eruption. *6 months after eruption* - Six months is a considerably **short period** for permanent tooth root completion. - At this stage, the **root apex** is usually still wide open, and the tooth is particularly vulnerable due to its **immature root structure**. *None of the options* - This option is incorrect as **2-3 years after eruption** accurately describes the typical timeframe for root completion of permanent teeth. - The process of root maturation is well-documented in **dental development**.

Question 92: The most common site for a thyroglossal cyst is

A. Suprahyoid
B. Subhyoid (Correct Answer)
C. Floor of mouth
D. Level of cricoid

Explanation: ***Subhyoid*** - The **thyroglossal duct** normally descends from the foramen cecum at the base of the tongue to the future thyroid gland location, usually in front of the trachea [1], [2]. - The most common site for a **thyroglossal cyst** to persist due to incomplete regression of this duct is in the **subhyoid region**, just below the hyoid bone. - Accounts for approximately **65-75%** of all thyroglossal cysts. *Suprahyoid* - While thyroglossal cysts can occur anywhere along the embryological descent path of the thyroid gland, the **suprahyoid region** (above the hyoid bone) is the second most common location, accounting for about 20-25% of cases [2]. - Cysts in this region might be closer to the base of the tongue but are not the most frequent site. *Floor of mouth* - A thyroglossal cyst would be an **extremely rare finding** in the floor of the mouth, as this is significantly higher than the typical path of the thyroglossal duct [3]. - Lesions in the floor of the mouth are more commonly ranulas or dermoid cysts. *Level of cricoid* - Cysts at the **level of the cricoid cartilage** would be considered a less common presentation for a thyroglossal cyst. - This location is lower than the usual subhyoid presentation, although still along the general path of the descending thyroid gland.

Practice by Chapter

Prenatal Development

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Postnatal Growth and Development

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Age-Related Anatomical Changes

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Developmental Abnormalities

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Principles of Teratology

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Developmental Basis of Congenital Anomalies

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Molecular Aspects of Development

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Genetic Factors in Developmental Anatomy

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Environmental Influences on Development

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Clinical Aspects of Developmental Anatomy

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