MCAT Biology : Developmental Physiology

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #1 : Gastrulation And Embryonic Germ Layers

The kidneys arise from which of the three embryonic germ layers?

Possible Answers:

Notochord region

Ectoderm

None of these choices are correct

Mesoderm

Endoderm

Correct answer:

Mesoderm

Explanation:

The three embryonic germ layers are the ectoderm, mesoderm, and endoderm. The mesoderm gives rise to bone, muscle, the urinary system, and the kidneys. Ectoderm develops into the nervous system, dermis, hair, nails, eyes, and ears. The endoderm develops into the lining of internal organs, such as the lungs and the gastrointestinal tract. The notochord is not an embryonic layer and, like the kidneys, arises from the mesoderm.

Example Question #2 : Gastrulation And Embryonic Germ Layers

What happens during the process of gastrulation?

Possible Answers:

The blastomeres undergo compaction

The ectoderm differentiates into epithelial tissue

The epiblast and hypoblast are created

The three primary germ layers are created

The cell divides into the eight-cell stage

Correct answer:

The three primary germ layers are created

Explanation:

The process of gastrulation generates the three primary germ layers (ectoderm, endoderm, mesoderm). This is one of the most important steps of development.

The eight-cell stage signals the beginning of compaction, during which the cells of the blastula adhere to each other and prepare for further divisions. The epiblast and hypoblast are generated before gastrulation, but after implantation. Differentiation occurs long after the primary germ layers are formed.

Example Question #1 : Gastrulation And Embryonic Germ Layers

A new born is assesed to have congenital nerve conduction defects. From which germ layer would this problem originate?

Possible Answers:

Blastula

Gastrula

Endoderm

Ectoderm

Mesoderm

Correct answer:

Ectoderm

Explanation:

The correct answer is the ectoderm. The ectoderm is responsible for generating nervous tissue and glial cells, among other features.

Ectoderm differntiates into the epidermis, nervous system, eye lens, and hair.

Mesoderm differentiates into muscle, cardiac and skeletal systems, blood, and spleen.

Endoderm differentiates into the lining of internal organs, like the digestive tract and respiratory tract.

Example Question #1 : Gastrulation And Embryonic Germ Layers

Which cell type is occasionally called "the fourth germ layer" due to its migratory properties and critical developmental importance?

Possible Answers:

Neural crest

Cardiomyocytes

Beta cells

Hepatocytes

Correct answer:

Neural crest

Explanation:

The ectoderm is the outer layer of the embryo, which gives rise to the external ectoderm and the neuroectoderm. The neuroectoderm can further be divided into the neural crest and the neural tube. The neural crest migrates from the neural tube early in development. While both external ectoderm and the neural tube form an epithelial layer, the neural crest does not and is actually a highly migratory cell lineage. Furthermore, the neural crest is required for innervation of endodermal organs (forming the enteric nervous system), craniofacial features, innervation of the diaphragm for breathing, and many more critical features. Due to its structural and migratory properties, and its importance in development, the neural crest is often referred to as the "fourth germ layer."

Cardiomyocytes refer to cardiac muscle cells, while hepatocytes are liver cells. Beta cells are found in the pancreas and secrete insulin.

Example Question #61 : Biology

Which of the following structures does not arise from the ectoderm?

Possible Answers:

Nervous system

Epidermis

Lungs

Lens of the eye

Correct answer:

Lungs

Explanation:

The ectoderm gives rise to the nervous system, epidermis, lens of the eye, and the inner ear. 

The lungs are derived from the endoderm. Most epithelial linings are located toward the superficial regions of the body, and arise from the ectoderm. The linings of the respiratory and digestive tracts, however, are embedded deep within the body and are derived from the endoderm.

Example Question #1 : Gastrulation And Embryonic Germ Layers

Which of the following structures does not arise from the endoderm?

Possible Answers:

Liver

Pancreas

Muscles

Lungs

Correct answer:

Muscles

Explanation:

The endoderm gives rise to most of the internal organs, including the lining of the digestive tract, the liver and pancreas, and the respiratory system.

Muscles and bones are derived from the mesoderm.

Example Question #61 : Biology

Which of the following structures does not arise from the mesoderm?

Possible Answers:

Respiratory system

Genitourinary system

Musculoskeletal system

Circulatory system

Correct answer:

Respiratory system

Explanation:

The mesoderm gives rise to muscles, bones, the circulatory system, the gonads, and the kidneys. Think of the mesoderm as the means by which your body gets around on a daily basis: muscles and bones, heart to pump blood, and kidneys to excrete waste.

The respiratory system arises from the endoderm.

Example Question #11 : Gastrulation And Embryonic Germ Layers

From which of the following germinal layers does the retina of the eye originate?

Possible Answers:

Endoderm

Ectoderm

Somites, which are not associated with a germ layer

Mesoderm

Correct answer:

Ectoderm

Explanation:

The retina of the eye originates as an outpouching of the diencephalon. The diencephalon is one of the five secondary vesicles in the early development of the neural tube, which is derived from the ectodermal germ layer.

The ectoderm gives rise to the epidermis, central nervous system, inner ear, and the lens of the eye.

Somites are small regions of specialized mesoderm, which give rise to the skeletal muscles and bones of the body.

Example Question #91 : Mcat Biological Sciences

From which of the following germ layers does the circulatory system arise?

Possible Answers:

Ectoderm

Endoderm

Mesoderm

Neural crest

Correct answer:

Mesoderm

Explanation:

The circulatory system arises from the mesoderm. Other mesoderm structures include the muscles, bones, gonads, and kidneys.

The ectoderm gives rise to the epidermis, nervous system, and lens of the eye. The neural crest originates from ectoderm cells.

The endoderm gives rise to several internal organs, including the liver and pancreas, as well as the linings of the digestive and respiratory tracts.

Example Question #11 : Gastrulation And Embryonic Germ Layers

Which embryonic structure is a precursor to the spinal cord?

Possible Answers:

Notochord

Blastocoel

Neural tube

Spemann's organizer

Correct answer:

Neural tube

Explanation:

The neural tube is a structure derived from the ectoderm that is found in chordates. The neural tube is formed by the closing of the neural folds, and runs along the dorsal-ventral axis of the developing embryo. Cells within the neural tube give rise to the neural crest. Additionally, the mature neural tube continues to develop into the central nervous system.

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