Embryology quiz

Questions reviewed by:

Mr David Kilroy MVB CVMA MRCVS
David Bainbridge VetMB MA PhD MRCVS

1

In the embryo, what structure does the falciform ligament contain?

	The mesonephric duct
	The common bile duct
	The umbilical vein
	The ductus venosus
	The yolk sac
Please select an option Incorrect. The mesonephric duct drains the embryological form of the kidney, the mesonephros. In the male it develops into the Wolffian duct which develops into the epididymis, vas deferens and seminal vesicles. In females the mesonephric duct regresses. The falciform ligament in the adult, which carries the round ligament of the liver in its free border, is the remnant of ventral mesogastrium that conveyed the umbilical vein from the umbilicus to the liver in the foetus. WikiVet Article: liver. Incorrect. The common bile duct enters the duodenum at the major duodenal papillae (with the pancreatic duct) on the dorsal surface of the duodenum. The falciform ligament in the adult, which carries the round ligament of the liver in its free border, is the remnant of ventral mesogastrium that conveyed the umbilical vein from the umbilicus to the liver in the foetus. WikiVet Article: liver. Correct!. The falciform ligament in the adult, which carries the round ligament of the liver in its free border, is the remnant of ventral mesogastrium that conveyed the umbilical vein from the umbilicus to the liver in the foetus. WikiVet Article: liver. Incorrect. The ductus venosus links the umbilical vein to the caudal vena cava. The falciform ligament in the adult, which carries the round ligament of the liver in its free border, is the remnant of ventral mesogastrium that conveyed the umbilical vein from the umbilicus to the liver in the foetus. WikiVet Article: liver. Incorrect. The yolk sac is an extraembryonic membrane which outpockets from the foetal midgut. It acts as a primitive placenta and allows the development of the vitelline circulation within the embryo. The falciform ligament in the adult, which carries the round ligament of the liver in its free border, is the remnant of ventral mesogastrium that conveyed the umbilical vein from the umbilicus to the liver in the foetus. WikiVet Article: liver.

2

During development, the intestines rotate around the cranial mesenteric artery. Through how many degrees do they rotate in the dog?

	270 degrees
	90 degrees
	45 degrees
	360 degrees
	180 degrees
Please select an option Correct! The early gut is a straight tube but later rotates through 270 degrees so that the adult configuration is attained. WikiVet Article: small intestine development. Incorrect. The early gut is a straight tube but later rotates through 270 degrees so that the adult configuration is attained. WikiVet Article: small intestine development. Incorrect. The early gut is a straight tube but later rotates through 270 degrees so that the adult configuration is attained. WikiVet Article: small intestine development. Incorrect. The early gut is a straight tube but later rotates through 270 degrees so that the adult configuration is attained. WikiVet Article: small intestine development. Incorrect. The early gut is a straight tube but later rotates through 270 degrees so that the adult configuration is attained. WikiVet Article: small intestine development.

3

In the adult, what structure does the septum transversum form?

	The greater omentum
	The parietal peritoneum
	The lesser omentum
	The ventral portion of the diaphragm
	The mediastinum
Please select an option Incorrect. The septum transversum, or caudal wall of the pericardial cavity, is formed of unsplit mesoderm. This structure, which is conspicuous in early embryos, extends from the ventral body wall and is the beginning of the diaphragm; however, it gives rise only to its ventral portion. There are also muscular contributions to the diaphragm from other sources. WikiVet Article: liver. Incorrect. The septum transversum, or caudal wall of the pericardial cavity, is formed of unsplit mesoderm. This structure, which is conspicuous in early embryos, extends from the ventral body wall and is the beginning of the diaphragm; however, it gives rise only to its ventral portion. There are also muscular contributions to the diaphragm from other sources. WikiVet Article: liver. Incorrect. The septum transversum, or caudal wall of the pericardial cavity, is formed of unsplit mesoderm. This structure, which is conspicuous in early embryos, extends from the ventral body wall and is the beginning of the diaphragm; however, it gives rise only to its ventral portion. There are also muscular contributions to the diaphragm from other sources. WikiVet Article: liver. Correct! The septum transversum, or caudal wall of the pericardial cavity, is formed of unsplit mesoderm. This structure, which is conspicuous in early embryos, extends from the ventral body wall and is the beginning of the diaphragm; however, it gives rise only to its ventral portion. There are also muscular contributions to the diaphragm from other sources. WikiVet Article: liver. Incorrect. The septum transversum, or caudal wall of the pericardial cavity, is formed of unsplit mesoderm. This structure, which is conspicuous in early embryos, extends from the ventral body wall and is the beginning of the diaphragm; however, it gives rise only to its ventral portion. There are also muscular contributions to the diaphragm from other sources. WikiVet Article: liver.

4

What is the temporal sequence of events in the formation of a mature mammalian kidney?

5

What determines gonadal differentiation in to a male?

	Presence of Mullerian ducts
	Presence of mullerian inhibitory substance (MIS)
	Absence of SRY gene
	Presence of SRY gene
	Presence of mesonephric ducts
Please select an option Incorrect. Presence of Mullerian ducts does not influence gonadal differentiation, they are primative structures present in the early embryo which will develop further or regress later in development. The correct answer is gonadal differentiation is determined by the presence of the SRY gene of the Y chromosome (sex determining region of the Y chromosome) which encodes “testicular determining factor” protein (TDF). Lack of SRY gene (i.e. XX females) leads to ovarian differentiation. WikiVet Article: genital development Incorrect. Mullerian inhibitory substance is produced by the testes and induces development of the mesonephric (Wolffian) duct system in to epididymis and vas deferens and causes regression of paramesonephric (Mullerian) duct. The correct answer is gonadal differentiation is determined by the presence of the SRY gene of the Y chromosome (sex determining region of the Y chromosome) which encodes “testicular determining factor” protein (TDF). Lack of SRY gene (i.e. XX females) leads to ovarian differentiation. WikiVet Article: genital development Incorrect. Lack of the SRY gene (i.e. in XX females) leads to ovarian differentiation. The correct answer is gonadal differentiation is determined by the presence of the SRY gene of the Y chromosome (sex determining region of the Y chromosome) which encodes “testicular determining factor” protein (TDF). WikiVet Article: genital development Correct! Gonadal differentiation is determined by the presence of the SRY gene of the Y chromosome (sex determining region of the Y chromosome) which encodes “testicular determining factor” protein (TDF). Lack of SRY gene (i.e. XX females) leads to ovarian differentiation. WikiVet Article: genital development Incorrect. Presence of mesonephric ducts does not influence gonadal differentiation, they are primative structures present in the early embryo which will develop further or regress later in development. The correct answer is gonadal differentiation is determined by the presence of the SRY gene of the Y chromosome (sex determining region of the Y chromosome) which encodes “testicular determining factor” protein (TDF). Lack of SRY gene (i.e. XX females) leads to ovarian differentiation. WikiVet Article: genital development

6

From which germ layer is the heart derived?

	Paraxial mesoderm
	Non neural ectoderm
	Splanchnic mesoderm
	Endoderm
	Intermediate mesoderm
Please select an option Incorrect. The axial skeleton and dermal muscle of the body are derived from paraxial mesoderm. The heart and tissue around the gut are derived from splanchnic mesoderm. WikiVet Article: gastrulation. Incorrect. The epidermis of the skin is derived from non neural ectoderm. The heart and tissue around the gut are derived from splanchnic mesoderm. WikiVet Article: gastrulation. Correct! The heart and tissue around the gut are derived from splanchnic mesoderm. WikiVet Article: gastrulation. Incorect. The pharynx, lungs, liver and lining of the gut are derived from endoderm. The heart and tissue around the gut are derived from splanchnic mesoderm. WikiVet Article: gastrulation. Incorrect. Parts of the reproductive system and the kidneys are derived from intermediate mesoderm. The heart and tissue around the gut are derived from splanchnic mesoderm. WikiVet Article: gastrulation.

7

Which pair of aortic arches form the internal carotid arteries?

	Fourth arches
	Second arches
	Sixth arches
	Third arches
	First arches
Please select an option Incorrect. The left fourth aortic arch contributes to the arch of the aorta. The right fourth aortic arch forms the proximal segment of the right subclavian artery. The third arches form the internal carotid arteries. WikiVet Article: aortic arches. Incorrect. The second arches degenerate completely. The third arches form the internal carotid arteries. WikiVet Article: aortic arches. Incorrect. The proximal segment of the right sixth aortic arch forms part of the right pulmonary artery while the distal segment atrophies. The proximal segment of the left sixth arch forms part of the pulmonary artery while the distal segment forms the ductus arteriosus. The third arches form the internal carotid arteries. WikiVet Article: aortic arches. Correct! The third aortic arches form the internal carotid arteries. WikiVet Article: aortic arches. Incorrect. The first arches degenerate completely. The third arches form the internal carotid arteries. WikiVet Article: aortic arches.

8

In the foetus, the ductus venosus shunts blood between which two structures?

	Umbilical vein and caudal vena cava
	Pulmonary artery and aorta
	Right ventricle and left ventricle
	Right atrium and left atrium
	Umbilical vein and portal vein
Please select an option Correct! The ductus venosus bypasses the liver by linking the umbilical vein to the caudal vena cava. The flow of blood is controlled by a sphincter, enabling the proportion travelling to the heart via the liver to be altered. WikiVet Article: foetal circulation. Incorrect. The ductus arteriosus connects the pulmonary artery to the aorta and allows equivalent ventricular function in the foetus. The ductus venosus bypasses the liver by linking the umbilical vein to the caudal vena cava. The flow of blood is controlled by a sphincter, enabling the proportion travelling to the heart via the liver to be altered. WikiVet Article: foetal circulation. Incorrect. There is no physiological shunt between the right and left ventricle in the foetus. The ductus venosus bypasses the liver by linking the umbilical vein to the caudal vena cava. The flow of blood is controlled by a sphincter, enabling the proportion travelling to the heart via the liver to be altered. WikiVet Article: foetal circulation. Incorrect. The foramen ovale is an opening between the two atria enabling blood to be channelled from the right to left atrium thereby bypassing the lungs. The ductus venosus bypasses the liver by linking the umbilical vein to the caudal vena cava. The flow of blood is controlled by a sphincter, enabling the proportion travelling to the heart via the liver to be altered.WikiVet Article: foetal circulation. Incorrect. There is no physiological shunt between the umbilical vein and the portal vein in the foetus. The ductus venosus bypasses the liver by linking the umbilical vein to the caudal vena cava. The flow of blood is controlled by a sphincter, enabling the proportion travelling to the heart via the liver to be altered. WikiVet Article: foetal circulation.