MCAT Biology : Gastrulation and Embryonic Germ Layers

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

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Example Question #1 : Gastrulation And Embryonic Germ Layers

The mesoderm germ layer eventually gives rise to the formation of the __________.

Possible Answers:

lining of the respiratory system

lining of the digestive system

nervous system

muscles

epidermis

Correct answer:

muscles

Explanation:

The mesoderm gives rise to the muscles among other structures. The other answers are derived from the ectoderm or endoderm.

Example Question #2 : Gastrulation And Embryonic Germ Layers

The thyroid gland arises from this embryonic layer __________.

I.  neuroectoderm

II.  ectoderm

III.  mesoderm

IV.  endoderm

V.  ectoderm with contributions from mesoderm

Possible Answers:

IV

I

II

III

V

Correct answer:

IV

Explanation:

Many of the glandular structures—both exocrine and endocrine—arise from endoderm. In particular, both the thyroid and parathyroid glands bud off from the pharyngeal mucosa, which of course is endodermal in character. Of course, like all tissues, there are mesodermal components of the gland in the way of connective tissues and blood vessels. The response indicating a mesodermal component invites you to make a wrong selection because you could remember that there are mesodermal-derived tissues everywhere, but you could not specifically recall the origin of the thyroid tissue, itself.  

Example Question #3 : Gastrulation And Embryonic Germ Layers

Which of the following is NOT a major germ layer formed during gastrulation?

Possible Answers:

Cytoderm

Ectoderm

Mesoderm

Endoderm

Correct answer:

Cytoderm

Explanation:

The correct answer is cytoderm.

There are three major germ layers formed during gastrulation: the ectoderm, mesoderm, and endoderm. Major structures form from these germ layers over the course of embryogenesis and development.

Example Question #1 : Gastrulation And Embryonic Germ Layers

A newly born child is having difficulty breathing and digesting food. A close medical examination has revealed an improperly formed inner lining to the digestive and respiratory systems. Which of the following is the most likely cause of the medical problem?

Possible Answers:

An abnormality has occurred in the development of the endoderm

Genetic abnormalities in both the mesoderm and ectoderm

A disruption of the mesoderm during development

A disease affecting the ectoderm germ layer

There is not enough information to determine a likely cause

Correct answer:

An abnormality has occurred in the development of the endoderm

Explanation:

Gastrulation is the formation of the three layers of the embryo: ectoderm, endoderm, and mesoderm. The endoderm gives rise to the lining of the digestive system and respiratory system. A defect in these tissues suggests a problem of that germ layer during development. The ectoderm gives rise to the nervous system and epidermis. The mesoderm gives rise to the muscle and skeletal systems.

Example Question #5 : Gastrulation And Embryonic Germ Layers

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

Possible Answers:

None of these choices are correct

Ectoderm

Notochord region

Endoderm

Mesoderm

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 ectoderm differentiates into epithelial tissue

The blastomeres undergo compaction

The three primary germ layers are created

The epiblast and hypoblast 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 #2 : 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:

Endoderm

Gastrula

Ectoderm

Blastula

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 #83 : Mcat Biological Sciences

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

Possible Answers:

Beta cells

Hepatocytes

Cardiomyocytes

Neural crest

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 #9 : Gastrulation And Embryonic Germ Layers

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 #4 : Gastrulation And Embryonic Germ Layers

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

Possible Answers:

Lungs

Muscles

Pancreas

Liver

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.

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