MCAT Biology : Developmental Physiology

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #31 : Systems Biology And Tissue Types

Which of the following is not a property of the trophoblast?

Possible Answers:

Gives rise to the embryo

Secretes factors to make the blastocoel

Cells that form the outer layer of the blastula 

Gives rise to the placenta

Correct answer:

Gives rise to the embryo

Explanation:

The blastula consists of a hollow sphere of cells (blastomeres) surrounding an inner fluid cavity called the blastocoel. There are two regions of the blastula: the inner cell mass (embryoblast) and the trophoblast. The inner cell mass gives rise to the primitive endoderm and epiblast, serving as the site of the developing embryo. The trophoblast cells form the outer ring of the blastocyst and combine with the maternal endometrium to form the placenta.

The inner cell mass, or embryoblast, gives rise to the cells that become the fetus.

Example Question #15 : Developmental Stages And Events

What is a blastula?

Possible Answers:

Precursor to the morula

Sphere of cells surrounding a blastocel

Structure that gives rise to embryonic cleavage

Solid ball of cells within the zona pellucida

Correct answer:

Sphere of cells surrounding a blastocel

Explanation:

A blastula is a sphere of cells (blastomeres) surrounding a fluid blastocoele. The blastula stage of embryogenesis begins with the appearance of the blastocoel. The blastocoel is a fluid filled cavity that contains amino acids, proteins, growth factors, and other components neccessary for cellular differentiation. The blastocoel allows blastomeres to move during gastrulation.

A morula is a solid ball of cells within the zona pellucida and is a precursor to the blastula.

Example Question #1 : Fetal Circulation

What fetal organs is blood shunted away from during gestation?

Possible Answers:

The lungs and liver

The lungs and kidneys

The liver and spleen

The kidneys and spleen

The lungs and intestines

Correct answer:

The lungs and liver

Explanation:

Oxygen diffuses from maternal blood to fetal blood through the placenta. Within the womb, the lungs are not able to work properly and so blood is rerouted through the foramen ovale and the ductus arteriosus. The liver is also underdeveloped, and not ready to perform the functions it will do in adulthood. The placenta takes over for the liver during gestation, and so blood is shunted away from the liver by the ductus venosus. This prevents oxygen that could be useful in other places from being wasted in the liver.

Example Question #1 : Fetal Circulation

The ductus arteriosus functions as a blood shunt during fetal development. Which circulatory components does the ductus arteriosus connect?

Possible Answers:

It shunts blood from the left atrium to the right atrium

It shunts blood from the right atrium to the left atrium

It shunts blood from the aorta to the pulmonary artery

It shunts blood away from the fetal liver

It shunts blood from the pulmonary artery to the aorta

Correct answer:

It shunts blood from the pulmonary artery to the aorta

Explanation:

The ductus arteriosus shunts blood from the pulmonary artery to the aorta in order to bypass the lungs, since the fetal lungs are not active.

The foramen ovale shunts blood from the right atrium to the left atrium, serving as another method to bypass the lungs. The ductus venosus shunts blood away from the fetal liver. There is no shunt from the aorta to the pulmonary artery, and there is no shunt from the left atrium to the right atrium.

Example Question #1 : Fetal Circulation

What is erythroblastosis fetalis?

Possible Answers:

A fatal condition in which the zygote implants in an area other than the uterine lining

A severe estrogen deficiency, resulting in partially developed reproductive organs

A dangerous syndrome that can result from mother/baby Rh factor incompatibility

A syndrome in which the mother's hormones fail to engage, resulting in loss of pregnancy

The process by which fetal erythrocytes grow and mature

Correct answer:

A dangerous syndrome that can result from mother/baby Rh factor incompatibility

Explanation:

Erythroblastosis fetalis is a rare conditon in which the mother's anti-Rh antibodies enter the fetal bloodstream and attach to fetal erythrocytes. If not caught, it can result in "blue-baby syndrome." Erythroblastosis is only present in patients negative for the Rh factor, and carrying Rh positive fetuses. 

Example Question #21 : Developmental Physiology

During what stage of pregnancy does a fetus's heart begin to beat?

Possible Answers:

The fetus's heart does not begin to beat until after delivery.

First trimester

Fourth trimester

Second trimester

Third trimester

Correct answer:

First trimester

Explanation:

A pregnancy consists of three trimesters, each of which is approximately 12 weeks. The fetus's heart, brain, spinal cord, and other organs begin to form in approximately the fifth week of pregnancy—in the first trimester.

Example Question #1 : Gastrulation And Embryonic Germ Layers

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

Possible Answers:

muscles

lining of the respiratory system

lining of the digestive system

epidermis

nervous system

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 #1 : 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:

I

IV

V

III

II

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 #1 : Gastrulation And Embryonic Germ Layers

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

Possible Answers:

Cytoderm

Mesoderm

Ectoderm

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:

A disruption of the mesoderm during development

A disease affecting the ectoderm germ layer

An abnormality has occurred in the development of the endoderm

There is not enough information to determine a likely cause

Genetic abnormalities in both the mesoderm and ectoderm

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.

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