Mcat Biology Ch. 3 Embryogenesis & Development

The Cortical Reaction involves a specific release of calcium ions with a distinct purpose as described in the correct answer.

The fertilization membrane is a crucial structure that forms after fertilization to protect the zygote and prevent polyspermy. It undergoes changes to become depolarized and impenetrable to prevent additional sperm entry.

Identical (monozygotic) twins occur when a single fertilized egg splits into two embryos. This results in the twins having the same genetic makeup. The incorrect answers describe different scenarios of twin formation that do not apply to identical twins.

Indeterminate cleavage leads to the formation of cells that are totipotent, meaning they have the potential to differentiate into any cell type in the organism.

Determinate cleavage is a type of cleavage in which the developmental fate of the cells is already determined early on, leading to differentiation into specific cell types.

A morula is a solid mass of cells that forms during early development before it progresses into a blastocyst with a hollow cavity.

A blastula is a specific stage in embryonic development that involves the formation of distinct cell types and structures, as described in the correct answer. The incorrect options provided do not accurately define or describe a blastula.

The chorion is a membrane created by trophoblasts that gives rise to the placenta in the development of a fetus.

Chorionic Villi are structures formed by trophoblasts during pregnancy that play a crucial role in supporting maternal-fetal gas exchange. They are not related to brain structures, lung sacs, or liver cells.

The umbilical cord connects the embryo to the placenta, facilitating the exchange of oxygenated and deoxygenated blood between the mother and the developing baby.

The yolk sac supports the embryo until the placenta is fully functional and eventually transforms into the umbilical cord, providing nutrients and oxygen to the developing fetus.

The allantois connects the embryo to the yolk sac and later develops into the umbilical cord to facilitate nutrient and waste exchange between the embryo and the mother.

The amnion is a thin, tough membrane filled with amniotic fluid that acts as a shock absorber during pregnancy, protecting the fetus.

Gastrulation is a crucial stage in embryonic development where the three primary germ layers are formed, leading to the subsequent development of various tissues and organs in multicellular organisms.

The term 'Archenteron' refers to the primitive gut that develops during embryonic development in organisms like cnidarians and echinoderms. It eventually gives rise to the digestive tract in the mature organism.

In deuterostomes like humans, the blastopore develops into the anus, while in protostomes, it develops into the mouth. The incorrect answers provided are inaccurate in describing the developmental fate of the blastopore.

During embryonic development, the ectoderm gives rise to various structures including the integument, epidermis, hair, nails, epithelia of nose, mouth, & lower anal canal, lens of eye, nervous system (including adrenal medulla!), and inner ear.

Mesoderm is one of the three primary germ layers in the early embryo, and it goes on to give rise to various important structures in the body as highlighted in the correct answer. The incorrect answers provided showcase different roles or layers in embryonic development to mislead test takers.

During embryonic development, the endoderm is the innermost layer of cells that gives rise to various internal organs and structures within the body. These include epithelial linings of the digestive and respiratory tracts, pancreas, thyroid, bladder, distal urinary tracts, and parts of the liver.

Neurulation specifically refers to the process of the nervous system development, distinct from other physiological processes mentioned in the incorrect answers.

The notochord plays a critical role in the development of the nervous system by inducing a group of overlying ectoderm cells to form neural folds surrounding the neural groove, eventually leading to the formation of the neural tube.

The neural tube develops into the central nervous system by fusing the neural folds during embryonic development in humans.

Teratogens are substances that can negatively impact the development of the embryo, leading to defects or even death. It is important to be aware of these harmful substances during pregnancy to protect the health of the unborn child.

Specification is just the initial stage where cells are designated to a specific type but can still change, unlike commitment in later stages of cell specialization.

Determination is the stage where cells commit to a specific function after being specified. It is influenced by various factors, such as the secretion of morphogens, and is a crucial step in cell specialization.

Morphogens are signaling molecules that establish concentration gradients in developing tissues, which in turn cause nearby cells to follow a particular developmental pathway, ultimately leading to determination of cell fate.

Differentiation in cell biology refers to the process by which a cell transforms into a specialized type of cell through selective transcription of certain genes. This process allows cells to develop distinct structures and functions.