Middle deft upper lip due to failure of fusion b/w
**Question:** Middle deft upper lip due to failure of fusion between
A. Ectoderm and mesoderm
B. Lips and tongue
C. Ectoderm and neural crest cells
D. Buccinator and orbicularis oris muscles
**Correct Answer:** C. Ectoderm and neural crest cells
**Core Concept:** During embryonic development, the upper lip is formed by fusion of structures derived from different germ layers. The upper lip is composed of ectoderm and neural crest cells. Ectoderm contributes to the epidermis and sensory structures, while neural crest cells form the muscles, blood vessels, and nerves.
**Why the Correct Answer is Right:** The correct answer (C) refers to the fusion of ectoderm and neural crest cells, which are involved in the formation of the upper lip. Ectoderm contributes to the epidermis and sensory structures, while neural crest cells form the muscles, blood vessels, and nerves in the upper lip.
**Why Each Wrong Option is Incorrect:**
A. Ectoderm and mesoderm: Mesoderm contributes to the skeletal system, blood vessels, and connective tissues. It is not involved in the formation of the upper lip.
B. Lips and tongue: The tongue is formed separately during embryonic development and does not form a part of the upper lip.
D. Buccinator and orbicularis oris muscles: These are the muscles responsible for mouth opening and closing, respectively, and do not form part of the upper lip.
**Why Each Wrong Option is Incorrect:**
A. Ectoderm and mesoderm: Mesoderm contributes to the skeletal system, blood vessels, and connective tissues. It is not involved in the formation of the upper lip.
B. Lips and tongue: The tongue is formed separately during embryonic development and does not form a part of the upper lip.
D. Buccinator and orbicularis oris muscles: These are the muscles responsible for mouth opening and closing, respectively, and do not form part of the upper lip.
**Clinical Pearl:** A thorough understanding of embryonic development is essential for understanding the anatomy and clinical implications, such as cleft lip and palate, which can occur due to genetic mutations affecting neural crest cell development.