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Question 1
Correct
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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, 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 2
Correct
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In the non-pregnant state which of the following hormones is secreted by the corpus luteum?
Your 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 3
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 4
Correct
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Ootidogenesis refers to which process during Oogenesis?
Your Answer: 1st and 2nd Meiotic Divisions
Explanation:Oogonium become Primary Oocyte via Growth/Maturation. This process is called oocytogenesis Primary Oocyte undergoes 2 meiotic divisions to become Ootids. This process is called Ootidogenesis Ootids differentiate into Ovum
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This question is part of the following fields:
- Embryology
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Question 5
Incorrect
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The second meiotic division of the oocyte is normally completed:
Your Answer: At the stage of the primary follicle
Correct Answer: After the sperm penetrates the secondary oocyte
Explanation:Upon penetration, if all is normally occurring, the process of egg-activation occurs, and the oocyte is said to have become activated. This is thought to be induced by a specific protein phospholipase c zeta. It undergoes its secondary meiotic division, and the two haploid nuclei (paternal and maternal) fuse to form a zygote.
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This question is part of the following fields:
- Embryology
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Question 6
Correct
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All of the following statements are true about Androgen insensitivity syndrome except:
Your Answer: The chromosomal sex is 46XX
Explanation:Patients suffering from androgen insensitivity syndrome have 46XY chromosomes. Due to insensitivity to androgens, they have female characteristics e.g. scant pubic or body hairs, enlarged mammary glands, and a small penis.
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This question is part of the following fields:
- Embryology
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Question 7
Correct
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Which structure is the primary mechanism for shunting blood away from the fetal pulmonary circulation?
Your 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 8
Correct
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From which germ cell layer does the GI tract initially develop?
Your Answer: Endoderm
Explanation:The GI tract forms from the endoderm. The endoderm grows laterally and then ventrally finally folding on its self to form the gut tube.
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This question is part of the following fields:
- Embryology
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Question 9
Correct
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Which one of the following changes are in the correct sequence regarding female puberty?
Your Answer: Thelarche, maximal growth velocity, menarche
Explanation:Thelarche means appearance of the breast tissue under the influence of oestrogen from the ovaries. It heralds the onset of puberty among girls. It is followed by an increase in growth velocity followed by menarche which is the time of first menstrual bleeding.
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This question is part of the following fields:
- Embryology
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Question 10
Correct
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From which germ layer does the myenteric plexus of the GI tract developed:
Your 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 11
Correct
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Commonest cause of precocious puberty is:
Your 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 12
Correct
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A 15 year old girl is being investigated for primary amenorrhoea. She has normal FSH,LH and E2 levels on hormone profiling and normal secondary sexual characteristics. An ultrasound shows no uterus. What is the likely diagnosis?
Your Answer: Rokitansky-Kuster-Hauser syndrome
Explanation:Mullerian agenesis occurs in 1 in 5000 to 1 in 40000 girls. The Mullerian system does not develop which results in an absent uterus and upper vagina. This condition is also known as Rokitansky-Kuster-Hauser syndrome, The ovarian function is normal and so the most common presentation is amenorrhea in the presence of an otherwise normal pubertal development.
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This question is part of the following fields:
- Embryology
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Question 13
Incorrect
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Which one of the following statements best suits Androgen insensitivity syndrome?
Your Answer: Oestrogen replacement therapy is not indicated because they have enough oestrogens to produce breast development
Correct Answer: Gonadectomy must be performed after puberty because of the increased risk of malignancy
Explanation:Androgen insensitivity syndrome patients have 46XY chromosomes. They are males by genotype but appear as female because of insensitivity to male hormones. It is advisable to perform gonadectomy in these patients after puberty because these patients are at increased risk of developing malignancy.
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This question is part of the following fields:
- Embryology
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Question 14
Incorrect
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Question 15
Correct
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Ootidogenesis refers to which process during Oogenesis?
Your Answer: 1st and 2nd Meiotic Divisions
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 16
Correct
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Which pharyngeal arch is closest to the head of the embryo?
Your 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 17
Correct
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From which germ cell layer does the GI tract initially develop?
Your Answer: Endoderm
Explanation:GI Tract initially forms via gastrulation from the endoderm of the trilaminar embryo around week 3. It extends from the buccopharyngeal membrane to the cloacal membrane. Later in development there are contributions from all three germ cell layers.
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This question is part of the following fields:
- Embryology
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Question 18
Correct
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How many days after fertilisation does the morula form?
Your 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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Question 19
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 20
Incorrect
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Which one of the following statements regarding Turner's syndrome is true?
Your Answer: Genetically is 46 XO
Correct Answer: Usually presents with primary amenorrhea
Explanation:Turner syndrome patients present with primary amenorrhea, have non functional or streak ovaries and cant conceive. They are 45X genetically.
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This question is part of the following fields:
- Embryology
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