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Question 1
Correct
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All of the following are features of Turner's syndrome except:
Your Answer: The ovaries are usually well developed
Explanation:Turner syndrome patients have malfunctioning or streak ovaries due to which they can never conceive. It affects females, who will have a short stature, widely spaced nipples, webbed neck and karyotyping shows 45XO.
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This question is part of the following fields:
- Embryology
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Question 2
Incorrect
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Normal physiological gut herniation occurs at how many weeks gestation?
Your Answer: 5 weeks
Correct Answer: 8 weeks
Explanation:At about 8-12 weeks gestation, normal physiological herniation of the fetal bowel occurs. The midgut protrudes into the base of the umbilicus, and undergoes a 90-degree anticlockwise rotation. When the abdominal cavity enlarges enough to fit the developing midgut, the intestines undergo another 180-degree rotation before returning to the abdominal cavity.
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This question is part of the following fields:
- Embryology
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Question 3
Incorrect
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Which structure is the primary mechanism for shunting blood away from the fetal pulmonary circulation?
Your Answer: Ductus Venosus
Correct Answer: Foramen Ovale
Explanation:Blood enters the right atrium of the fetal heart and most passes through the foramen ovale into the left atrium. From there it is pumped through the aorta. The foramen ovale is the major structure for bypassing the fetal pulmonary circulation. Some of the blood in the right atrium does enters the right ventricle and then into the pulmonary artery however most of this passes through the ductus arteriosus into the aorta thus bypassing the fetal pulmonary circulation.
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This question is part of the following fields:
- Embryology
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Question 4
Correct
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Several mechanisms have been proposed as to what causes closure of the Ductus Arteriosus (DA) at Parturition. Which of the following is the most important in maintaining the patency of the DA during pregnancy?
Your Answer: PGE2
Explanation:Prostaglandin E1 and E2 help maintain the patency of the DA during pregnancy. PGE2 is by far the most potent and important. It is produced in large quantities by the placenta and the DA itself.
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This question is part of the following fields:
- Embryology
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Question 5
Incorrect
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When does Oocytogenesis complete?
Your Answer: Ovulation
Correct Answer: Birth
Explanation:During the early fetal life, oogonia proliferate by mitosis. They enlarge to form primary oocyte before birth. No primary oocyte is form after birth. The primary oocyte is dormant is the ovarian follicles until puberty. As the follicle matures, the primary oocyte completes its first meiotic division and gives rise to secondary oocyte. During ovulation the secondary oocytes starts the second meiotic division but is only completed if a sperm penetrates it. This 1st and 2nd meiotic division is known as ootidogenesis.
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This question is part of the following fields:
- Embryology
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Question 6
Incorrect
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Regarding the closure of the ductus arteriosus (DA) after birth which of the following most accurately describes the mechanisms leading to closure of the DA?
Your Answer: Increased arterial pO2, decreased bradykinin & decreased Prostaglandin E2
Correct Answer: Increased arterial pO2, increased bradykinin & decreased Prostaglandin E2
Explanation:Normal closure of the ductus arteriosus (DA) is brought about by a number of mechanisms. Upon delivery the new born babies first breath inflates the lungs and this causes a rise in pO2. Oxygen is known to cause constriction of the DA in vivo and in vitro. In addition the decreased vascular resistance means the pressure within the lumen of the DA drops aiding closure. In addition on inflation of the lungs, the lungs produce bradykinin which stimulates smooth muscle constriction of the ductus. The most important factor is thought to be the drop in Prostaglandin E2. Prostaglandin E2 maintains patency of the Ductus in the unborn child but after birth is metabolised in the lungs and its levels fall rapidly within 3 hours of birth.
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This question is part of the following fields:
- Embryology
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Question 7
Incorrect
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In fetal circulation:
Your Answer: The foramen ovale connects the two ventricles
Correct Answer: Most of the blood entering the right atrium flows into the left atrium
Explanation:Circulation in the foetus: 1. Deoxygenated fetal blood is conducted to the placenta via the two umbilical arteries. The umbilical arteries arise from the internal iliac arteries.
2. Gas exchange occurs in placenta.
3. Oxygenated blood from the placenta passes through the single umbilical vein and enters the inferior vena cava (IVC).
4. About 50% of the blood in the IVC passes through the liver and the rest bypasses the liver via the ductus venosus. The IVC also drains blood returning from the lower trunk and extremities.
5. On reaching the heart, blood is effectively divided into two streams by the edge of the interatrial septum (crista dividens) (1) a larger stream is shunted to the left atrium through the foramen ovale (lying between IVC and left atrium) (2) the other stream passes into right atrium where it is joined by blood from SVC which is blood returning from the myocardium and upper parts of body. This stream therefore has a lower partial pressure of oxygen.
6. Because of the large pulmonary vascular resistance and the presence of the ductus arteriosus most of the right ventricular output passes into the aorta at a point distal to the origin of the arteries to the head and upper extremities. The diameter of the ductus arteriosus is similar to the descending aorta. The patency of the ductus arteriosus is maintained by the low oxygen tension and the vasodilating effects of prostaglandin E2;
7. Blood flowing through the foramen ovale and into left atrium passes into the left ventricle where it is ejected into the ascending aorta. This relatively oxygen rich blood passes predominantly to the head and upper extremities. -
This question is part of the following fields:
- Embryology
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Question 8
Incorrect
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All of the following may result from a bicornuate uterus except:
Your Answer: Abnormal fetal lie
Correct Answer: Congenital anomalies of the baby
Explanation:Literature review shows that bicornuate uterus is associated with increase risk of spontaneous abortion in about 36% of patients. There is also an increased risk of preterm birth, malpresentation and fetal growth retardation.
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This question is part of the following fields:
- Embryology
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Question 9
Incorrect
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Which one of the following statements is related to testicular feminization syndrome?
Your Answer: Kalman's syndrome is a recognized cause
Correct Answer: There are usually normal testes
Explanation:Androgen insensitivity (testicular feminization) syndrome is a rare inherited form of male pseudo hermaphroditism that occurs in phenotypically normal women with adequate breast development, normal external genitalia, a vagina of variable depth, absent uterus, and sparse or absent pubic hair and axillary hair. Testosterone levels are normal or elevated.
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This question is part of the following fields:
- Embryology
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Question 10
Incorrect
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Regarding feto-maternal blood circulation, which of the following statements is false?
Your Answer: Deoxygenated fetal blood arrives at the placenta via 2 umbilical arteries
Correct Answer: At term the placenta receives 70% of uterine blood flow
Explanation:The placenta is important for regulating feto-maternal blood circulation, ensuring that the two circulatory systems do not come into direct contact. The placenta receives 70-80% of the uterine blood flow into the decidual spiral arteries where nutrient, waste and gaseous exchange with fetal blood takes place via the villous core fetal vessels. Deoxygenated blood arrives at the placenta via two uterine arteries while oxygenated, nutrient-rich blood is circulated back to the foetus via a single umbilical vein. The pressure in the umbilical vein is about 20 mmHg.
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This question is part of the following fields:
- Embryology
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Question 11
Incorrect
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From which germ layer does the myenteric plexus of the GI tract developed:
Your Answer: Neural tube of Ectoderm
Correct Answer: Neural crest of Ectoderm
Explanation:During the 5th week, the neural crest cells migrate along each side of the spinal cord where they form ganglions located dorsolateral to the aorta. Some of these cells migrate ventrally and form neurons in the preaortic ganglia as the celiac and mesenteric ganglia.
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This question is part of the following fields:
- Embryology
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Question 12
Incorrect
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Which pharyngeal arch is closest to the head of the embryo?
Your Answer: 2nd
Correct Answer: 1st
Explanation:The arches are numbered according to their proximity to the head i.e. the 1st is the closest to the head end of the embryo and the 6th closest to the tail end as shown by the diagram below the table
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This question is part of the following fields:
- Embryology
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Question 13
Incorrect
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Question 14
Incorrect
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Which one of the following statements is true regarding androgen insensitivity syndrome?
Your Answer: They have testes that should be kept to produce hormones
Correct Answer: They have no uterus
Explanation:Androgen insensitivity syndrome means that patients are phenotypically males but they are resistant or insensitive to male androgen hormones. They do not have a uterus. Due to insensitivity to androgens these patients often have female traits but their genetic makeup is of male, 46XY.
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This question is part of the following fields:
- Embryology
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Question 15
Incorrect
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The external carotid artery develops from which pharyngeal arch?
Your Answer: 4th
Correct Answer: 1st
Explanation:The maxillary arteries and the external carotid arteries develop from the first pharyngeal arch. The stapedial arteries arise from the second, the common carotid artery and the internal carotid arteries from the third and the arch of the aorta and the right subclavian artery from the forth arch.
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This question is part of the following fields:
- Embryology
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Question 16
Incorrect
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Branches V2 and V3 of the trigeminal nerve develop from which pharyngeal arch?
Your Answer: 3rd
Correct Answer: 1st
Explanation:Trigeminal nerve has three divisions, the first is the ophthalmic division that does not originate from any of the pharyngeal arches, the second and third divisions, namely, the maxillary and the mandibular region develop from the first pharyngeal arch.
Pharyngeal Arches:
1st = Trigeminal V2 & V3 (CN V)
2nd = Facial (CN VII)
3rd = Glossopharyngeal (CN IX)
4th and 6th = Vagus (CN X) -
This question is part of the following fields:
- Embryology
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Question 17
Incorrect
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Commonest cause of precocious puberty is:
Your Answer: Granulosa cell tumour
Correct Answer: Idiopathic
Explanation:Precocious puberty can be defined as secondary sexual characteristics that occur before the age of 8 years in females and 9 years in males. In 80-90% of individuals it is idiopathic. Other causes include CNS anomalies and tumours, increased exposure to sex hormones/steroids, pituitary gonadotrophin secreting tumours and ovarian tumours etc.
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This question is part of the following fields:
- Embryology
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Question 18
Incorrect
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In the non-pregnant state which of the following hormones is secreted by the corpus luteum?
Your Answer: LH
Correct Answer: Progesterone
Explanation:The Corpus Luteum is a temporary endocrine structure that secretes two steroid hormones: 1. Progesterone (17a Hydroxyprogesterone) and 2. Oestradiol. The corpus luteum also secretes Inhibin A. In the menstrual cycle if fertilisation doesn’t occur the corpus luteum stops secreting progesterone and degenerates into a corpus albicans. If fertilisation occurs hCG signals the corpus to continue progesterone production and it is then termed the corpus luteum graviditatis
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This question is part of the following fields:
- Embryology
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Question 19
Incorrect
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All of the following statements are true regarding Turner's syndrome except?
Your Answer: Are usually less than 5 feet tall
Correct Answer: The streak ovaries should be removed surgically due to 25% tendency to be malignant
Explanation:Girls with Turner’s syndrome (45,X) are not at risk for malignancy. Patients with feminizing testicular syndrome with XY chromosome composition and patients with mixed gonadal dysgenesis are at risk for malignancy, and bilateral gonadectomy is performed.
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This question is part of the following fields:
- Embryology
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Question 20
Incorrect
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How many days after fertilisation does the morula form?
Your Answer:
Correct Answer: 4
Explanation:When there are about 12-32 blastomeres, the developing human is referred to as morula. It enters the uterine cavity around the 4th day after fertilization.
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This question is part of the following fields:
- Embryology
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