Question

Which of the following organs is differentiated, first during development?
A. Heart
B. Skin
C. Brain
D. Neural tube

Answer 1

Hint: In humans, the zygote or embryo undergoes spatial and temporal changes that culminate in embryogenesis, which includes stages such as gastrulation, germ layer formation, histogenesis, neurulation, and organogenesis. Following this, the heart is the first organ to differentiate and develop, beginning to beat and pump blood around 21 or 22 days.

Step by step solution:
Embryogenesis, or the first eight weeks of development after fertilization, is a highly complex process. It's incredible that in eight weeks, we go from a single cell to an organism with a multi-level body plan. During this stage, the circulatory, excretory, and nervous systems all begin to develop.
Organogenesis is the stage of embryonic development that begins after gastrulation and lasts until birth. The three germ layers formed during gastrulation create the internal organs of the organism during organogenesis.

Each of the three germ layers' cells differentiates a process in which less-specialized cells become more specialized by expressing a specific set of genes. Cell signaling cascades drive cell differentiation.
The heart is the first organ to develop in the embryo amid the development of the body. There are numerous changes that occur during embryonic development. The embryonic cells, or stem cells, multiply and develop. They multiply rapidly enough to allow the formation of the entire human body. Body parts and major organs start growing gradually.

The cardiogenic region is formed by cardiac myoblasts and blood islands in the splanchnopleuric mesenchyme on each side of the neural plate. It is a horseshoe-shaped area near the embryo's head. Following cell signaling, two strands begin to emerge as tubes in this region by day 19, with a lumen developing within them. By day 21, these two endocardial tubes have migrated toward one another and fused to create a single primitive heart tube, the tubular heart. Legs and digits are formed by the end of the second month of pregnancy. Most of the major organ systems are formed by the end of the first trimester which is 3 months.

So, option A is correct.

Note: The neural tube is responsible for the formation of the brain and spinal cord. Vertebrates have a neural crest that develops into a variety of structures, including bones, muscles, and central nervous system components. The differentiation of the ectoderm into the neural crest, neural tube, and surface ectoderm is known as neurulation, and the embryo in this stage is known as the neurula.