Examples of acoelomates include animals in the phylum Platyhelminthes, also known as flatworms. Triploblasts that do not develop a coelom are called acoelomates, and their mesoderm region is completely filled with tissue, although they do still have a gut cavity. The coelom also provides space for the diffusion of gases and nutrients, as well as body flexibility, promoting improved animal motility. Organs housed within the coelom can grow and move freely, which promotes optimal organ development and placement. Primarily, the coelom provides cushioning and shock absorption for the major organ systems. The evolution of the coelom is associated with many functional advantages. In some animals, such as mammals, the part of the coelom called the pleural cavity provides space for the lungs to expand during breathing. It houses many organs such as the digestive system, kidneys, reproductive organs, and heart, and contains the circulatory system. This epithelial cell-lined coelomic cavity represents a space, usually filled with fluid, which lies between the visceral organs and the body wall. Presence or Absence of a Coelomįurther subdivision of animals with three germ layers (triploblasts) results in the separation of animals that may develop an internal body cavity derived from mesoderm, called a coelom, and those that do not. This germ layer gives rise to all muscle tissues (including the cardiac tissues and muscles of the intestines), connective tissues such as the skeleton and blood cells, and most other visceral organs such as the kidneys and the spleen. The mesoderm is the third germ layer it forms between the endoderm and ectoderm in triploblasts. The ectoderm develops into the outer epithelial covering of the body surface, the central nervous system, and a few other structures. The endoderm gives rise to the lining of the digestive tract (including the stomach, intestines, liver, and pancreas), as well as to the lining of the trachea, bronchi, and lungs of the respiratory tract, along with a few other structures.
Infection by rubella virus: In adults, rubella (German measles) is a relatively mild disease, but if the virus passes from an infected mother to her embryo, it may have severe consequences.Each of the three germ layers is programmed to give rise to particular body tissues and organs.Children born with this disorder may have cognitive deficits, developmental delays, behavioral issues, and distinctive facial features. Alcohol consumption: Exposure of the embryo to alcohol from the mother’s blood can cause fetal alcohol spectrum disorder.If the embryo survives and goes on to develop and grow as a fetus, it is likely to have birth defects.Įnvironmental exposures are known to have adverse effects on the embryo include: They may cause the embryo to die and be spontaneously aborted (also called a miscarriage). Genetic defects or harmful environmental exposures during this stage are likely to have devastating effects on the developing organism. Events that occur in the embryo lay the foundation for virtually all of the body’s different cells, tissues, organs, and organ systems. The embryonic stage is a critical period of development. Genetic and Environmental Risks to Embryonic Development
The neural tube also develops a bulge at one end, which will later become the brain. Most of the neural tube will eventually become the spinal cord. The convergence of the neural plate borders also results in the formation of a neural tube. The neural plate then starts to fold inward until its borders converge. It begins when a structure of differentiated cells called a neural plate forms from the ectoderm.
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