Question 1

In humans, muscle is derived from which embryonic layer?

Accepted Answer

Answer reason: Muscle tissues originate from mesoderm: skeletal muscle from paraxial mesoderm (somites) and smooth/cardiac muscle from splanchnic mesoderm. Ectoderm and endoderm give rise to other tissues.

Question 2

In identical twins sharing a common chorion, how many placentas are present?

Accepted Answer

Answer reason: Monochorionic (shared chorion) twins have a single placenta; two placentas occur with dichorionic twins, which may appear fused.

Question 3

What is a fertilized egg known as?

Accepted Answer

Answer reason: A fertilized egg cell is termed a zygote. An oocyte is an unfertilized egg, the corpus luteum is an ovarian structure after ovulation, and a fetus is a later developmental stage.

Question 4

The placenta is closely attached to the embryo by a tube called?

Accepted Answer

Answer reason: The fetus is connected to the placenta by the umbilical cord, which carries fetal blood to and from the placenta for exchange of gases and nutrients. The neural tube and spinal cord are components of the nervous system, and the fallopian tube connects ovary to uterus, not to the placenta.

Question 5

What is the name of the condition caused by premature closure of the sagittal suture?

Accepted Answer

Answer reason: Premature fusion of the sagittal suture (sagittal synostosis) produces a long, narrow skull—scaphocephaly (dolichocephaly).

Question 6

Maternal ethanol use during pregnancy can lead to the development of which condition in offspring?

Accepted Answer

Answer reason: Alcohol is a teratogen; prenatal exposure causes fetal alcohol syndrome. The other options are chromosomal disorders not caused by maternal ethanol use.

Question 7

From which embryonic structure is the vertebral column derived?

Accepted Answer

Answer reason: The vertebral column forms around the notochord; sclerotomes of paraxial mesoderm, induced by the notochord, develop into vertebrae. The notochord remnant becomes the nucleus pulposus.

Question 8

Renal agenesis is associated with which condition?

Accepted Answer

Answer reason: Fetal urine is the main source of amniotic fluid; in renal agenesis no urine is produced, leading to oligohydramnios (Potter sequence).

Question 9

The placenta originates from which structure?

Accepted Answer

Answer reason: The placenta forms from the fetal chorion frondosum together with the maternal decidua basalis. Decidua vera (parietalis) and decidua capsularis do not form the placenta.

Question 10

The vertebral column is derived from which embryonic structure?

Accepted Answer

Answer reason: The vertebral column develops from mesodermal sclerotomes induced by the notochord; the notochord also persists as the nucleus pulposus. Endoderm forms gut lining and the nerve cord forms the CNS.

Question 11

Normally, how many arteries and veins does the umbilical cord contain?

Accepted Answer

Answer reason: The typical umbilical cord contains two umbilical arteries carrying deoxygenated blood from the fetus and one umbilical vein carrying oxygenated blood from the placenta.

Question 12

Which fetal structure closes functionally immediately after birth?

Accepted Answer

Answer reason: At the first breath, pulmonary blood flow and left atrial pressure rise, pressing the septum primum against the septum secundum and functionally closing the foramen ovale immediately. The ductus arteriosus closes hours to days later; the ductus venosus and umbilical arteries close over the ensuing hours to days.

Question 13

What is the average length of the umbilical cord?

Accepted Answer

Answer reason: The umbilical cord is typically about 50–60 cm long at term; among the choices, 55 cm best represents the average length.

Question 14

Tuft of hair is seen in which type of neural tube defect?

Accepted Answer

Answer reason: A tuft of hair and skin dimple over the lumbosacral area are classic cutaneous markers of spina bifida occulta; cystica presents with a sac-like protrusion, and the others are unrelated.

Question 15

At which site does the closure of the neural tube begin?

Accepted Answer

Answer reason: Neural tube closure initiates near the future cervical region (around the 5th somite) and proceeds cranially and caudally.

Question 16

What is the normal length of a fetus at 16 weeks?

Accepted Answer

Answer reason: At 16 weeks the fetus is about 15–16 cm crown-to-heel; 15 cm is the closest option.

Question 17

What is a newborn human baby called?

Accepted Answer

Answer reason: A newborn is termed a neonate from birth to 28 days of life. Fetus is in utero before birth; zygote is the fertilized egg; embryo is early intrauterine stage.

Question 18

Oxygenated blood is carried to the fetus by which vessel?

Accepted Answer

Answer reason: In fetal circulation, the umbilical vein carries oxygenated, nutrient-rich blood from the placenta to the fetus; the umbilical arteries return deoxygenated blood to the placenta.

Question 19

During intra-uterine life of fetal development, by what week do the majority of testicles descend into the scrotum?

Accepted Answer

Answer reason: Testicular descent into the scrotum typically occurs in late second to early third trimester, with most reaching the scrotum by about 28 weeks.

Question 20

What is the name of the congenital condition characterized by incomplete fusion of the lip or palate?

Accepted Answer

Answer reason: Failure of embryologic fusion of the orofacial structures produces a cleft. Among the options, cleft palate names this congenital defect; 'congenital fusion' is incorrect and 'cleft lip' refers only to the lip.

Question 21

The cell from which human body develops is known as -?

Accepted Answer

Answer reason: Human development begins at fertilization when the sperm and ovum unite to form a diploid zygote. This single totipotent cell undergoes cleavage and differentiation to produce the embryo and ultimately the entire body. The ovum and sperm are gametes, and the ovary is an organ, not the developmental cell itself.

Question 22

Fertilized Egg is known as?

Accepted Answer

Answer reason: A fertilized egg is termed a zygote, formed at the moment the sperm nucleus fuses with the oocyte nucleus. An oocyte refers to the unfertilized female gamete. The corpus luteum is an ovarian structure that forms after ovulation and secretes progesterone. The term fetus applies later in development, typically from the 9th week of gestation onward.

Question 23

Which organ are first develop in embryo?

Accepted Answer

Answer reason: The heart is the first functional organ to form in human embryogenesis. Cardiogenesis begins in the third week, and the primitive heart tube starts beating and circulating blood by about day 22–23. The brain and neural tube form very early but are not functional organs at this time, and lungs and kidneys develop later. Therefore, the earliest organ to develop and function is the heart.

Question 24

First organ developed in Embryo?

Accepted Answer

Answer reason: The heart is the first functional organ to form during embryogenesis. Cardiac progenitors create the primitive heart tube in week 3, which begins spontaneous contractions by about day 22–23. This early circulation is essential to support rapidly growing tissues, preceding full development of other organs such as the brain, liver, and kidneys.

Question 25

Neural tube defect occurs due to deficiency of?

Accepted Answer

Answer reason: Neural tube defects result from failure of neural tube closure in early embryogenesis, most strongly linked to folate (vitamin B9) deficiency. Adequate maternal folic acid before conception and in the first trimester markedly reduces the risk of spina bifida and anencephaly. While B12 deficiency can contribute to megaloblastic changes, folate deficiency is the classic and primary association with NTDs.

Question 26

Which the following deficiency leads to neural tube defects, during pregnancy-?

Accepted Answer

Answer reason: Folic acid deficiency in early pregnancy impairs DNA synthesis and cell division required for neural tube closure by day 28 post-conception, leading to defects such as spina bifida and anencephaly. Periconceptional folic acid supplementation reduces neural tube defect risk substantially. Iron, calcium, and zinc are important in pregnancy but are not the primary factors preventing neural tube defects.

Question 27

Which organ first develops in the fetus?

Accepted Answer

Answer reason: The heart is the first functional organ to form in the embryo. Cardiogenesis begins in the third week of gestation, and the primitive heart tube starts beating by about day 22–23 to establish circulation. Other organs such as the brain, liver, kidneys, and lungs differentiate later and become functional after the heart.

Question 28

First organ developed in embryo?

Accepted Answer

Answer reason: The cardiovascular system is the first to form and function in the embryo. A primitive heart tube arises from mesoderm and begins beating and circulating blood by about day 22–23 (week 3). The neural tube forms earlier but does not constitute a functioning organ yet; kidneys and liver differentiate later (around weeks 5–6 and beyond). Therefore, the first organ developed is the heart.

Question 29

Blood is produced in first 6 months of fetus in?

Accepted Answer

Answer reason: During fetal development, hematopoiesis begins in the yolk sac (weeks 3–8) and then shifts primarily to the liver from about 6 weeks until around 6–7 months of gestation. The spleen contributes between roughly 10–28 weeks. Bone marrow becomes the dominant site late in gestation and after birth. Therefore, in the first six months of fetal life, the liver is the main site of blood production.

Question 30

Umbilical cord normally contains two arteries and one vein?

Accepted Answer

Answer reason: The normal umbilical cord contains two umbilical arteries and one umbilical vein. The arteries carry deoxygenated blood from the fetus to the placenta, while the single vein returns oxygenated, nutrient-rich blood to the fetus. A single umbilical artery is an anatomic variant and may be associated with congenital anomalies, but the typical configuration is 2 arteries and 1 vein.

Question 31

Placenta develops from both maternal and fetal tissues?

Accepted Answer

Answer reason: The placenta has a fetal component (chorion frondosum derived from trophoblast and extraembryonic mesoderm) and a maternal component (decidua basalis of the endometrium). These layers interface to allow nutrient, gas, and waste exchange across the placental barrier without direct mixing of maternal and fetal blood. Therefore, it develops from both maternal and fetal tissues.

Question 32

Oxygenated blood is carried to the fetus by _______?

Accepted Answer

Answer reason: In fetal circulation, oxygenated blood from the placenta returns to the fetus through the single umbilical vein. The two umbilical arteries carry deoxygenated blood from the fetus back to the placenta for gas exchange. Therefore, only the umbilical vein carries oxygenated blood to the fetus.

Question 33

Normal length of human placenta is.......?

Accepted Answer

Answer reason: At term, the umbilical cord—the structure commonly queried in such items—has an average length of about 50 cm. The placenta itself is roughly 15–20 cm in diameter and ~2–3 cm thick, not matching the choices. Thus, the best available answer corresponding to expected obstetric measurements is 50 cm.

Question 34

The earliest hematopoiesis occurs in?

Accepted Answer

Answer reason: Primitive hematopoiesis begins in the yolk sac blood islands around the third week of embryogenesis. The fetal liver then becomes the major site, followed by the spleen, and finally the bone marrow takes over in late gestation and postnatally. Therefore, the earliest site is the yolk sac.

Question 35

The umbilical cord consists of ........?

Accepted Answer

Answer reason: A normal umbilical cord contains two umbilical arteries and one umbilical vein embedded in Wharton’s jelly. The arteries carry deoxygenated blood and waste from the fetus to the placenta, while the single vein returns oxygenated, nutrient-rich blood to the fetus. Variants like a single umbilical artery are abnormalities associated with fetal anomalies, but the typical configuration is 2 arteries and 1 vein.

Question 36

Which of these organs supplies blood for the embryo?

Accepted Answer

Answer reason: The placenta functions as the exchange organ between mother and fetus, delivering oxygenated blood and nutrients to the embryo via the umbilical vein. While fetal hematopoiesis occurs primarily in the liver early and later in the bone marrow, these organs do not supply maternal-derived oxygenated blood to the embryo. The kidney is not involved in supplying blood.

Question 37

The umbilical vein first delivers blood to which organ?

Accepted Answer

Answer reason: In fetal circulation, the umbilical vein carries oxygenated blood from the placenta toward the fetus. It first enters the liver via the left portal vein and passes through the hepatic sinusoids or bypasses partially via the ductus venosus to the inferior vena cava. Thus, the initial organ receiving umbilical venous blood is the liver.

Question 38

In renal agenesis, amniotic fluid is?

Accepted Answer

Answer reason: From mid-gestation onward, most amniotic fluid volume comes from fetal urine production. In bilateral renal agenesis, fetal kidneys are absent, so urine is not produced. This leads to oligohydramnios, i.e., decreased amniotic fluid, often associated with Potter sequence. Therefore, the amniotic fluid is decreased.

Question 39

What is the first organ that develops in foetus?

Accepted Answer

Answer reason: Neurulation begins around week 3, when the neural plate forms and folds into the neural tube, giving rise to the brain and spinal cord. This occurs earlier than development of the lungs (lung bud ~week 4), liver (hepatic diverticulum ~week 4), and kidneys (metanephros ~week 5). Although the heart is the first functional organ, it is not among the choices; thus the earliest developing option is the brain.

Question 40

Amniotic fluid is mainly formed by?

Accepted Answer

Answer reason: By mid-gestation the fetal kidneys produce large volumes of urine that are excreted into the amniotic cavity, making fetal urine the principal source of amniotic fluid. Earlier in pregnancy, small amounts come from transmembranous diffusion of maternal plasma and fetal lung fluid, but these are not the main contributors later on. The placenta and yolk sac are not primary producers of amniotic fluid.

Question 41

Pharyngeal pouch 3 gives rise to?

Accepted Answer

Answer reason: The third pharyngeal pouch forms the thymus from its ventral wing and the inferior parathyroid glands from its dorsal wing. The palatine tonsil derives from the second pouch, not the third. The superior parathyroids arise from the fourth pouch, and the thyroid gland develops from a midline endodermal diverticulum of the floor of the primitive pharynx. Therefore, the unambiguous derivative listed is the thymus.

Question 42

The permanent kidney develops from?

Accepted Answer

Answer reason: The definitive or permanent kidney arises from the metanephros, which forms from the interaction of the ureteric bud with the metanephric mesenchyme. The pronephros is rudimentary and nonfunctional in humans. The mesonephros functions transiently in early fetal life and contributes to parts of the male reproductive tract via the mesonephric (Wolffian) duct. The Wolffian duct gives rise to the ureteric bud but does not itself form the kidney parenchyma.

Question 43

Meckel’s diverticulum is remnant of?

Accepted Answer

Answer reason: Meckel’s diverticulum is a true diverticulum of the ileum resulting from persistence of the vitelline (omphalomesenteric) duct, which normally obliterates during early fetal life. It may contain ectopic gastric or pancreatic mucosa and can present with painless lower GI bleeding or inflammation mimicking appendicitis. The allantois remnant forms the urachus, not the Meckel’s diverticulum, and the notochord and umbilical cord are unrelated to this structure.

Question 44

Patient with bicornuate uterus. Associated anomalies are?

Accepted Answer

Answer reason: A bicornuate uterus is a Müllerian duct fusion anomaly. The Müllerian and mesonephric (renal) systems develop in close proximity, so congenital uterine malformations are frequently associated with renal tract abnormalities such as renal agenesis, ectopia, or duplication. Cardiac, gastrointestinal, and respiratory anomalies are not classically linked to Müllerian defects. Therefore, renal anomalies are the most likely association.

Question 45

Primary brain vesicle is?

Accepted Answer

Answer reason: During early neural development, the brain forms three primary vesicles: the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain). These are the initial subdivisions of the neural tube that later differentiate into secondary vesicles and mature brain regions. Since all listed structures are primary vesicles, the correct choice is 'All of above.

Question 46

Fertilization normally occurs in which part of fallopian tube?

Accepted Answer

Answer reason: Fertilization typically occurs in the ampulla of the uterine (fallopian) tube, which is the widest segment near the ovary. Its spacious lumen and extensive mucosal folds facilitate the meeting of sperm and oocyte. Ciliary action and tubal peristalsis in the ampulla support gamete transport and fusion. The infundibulum primarily captures the ovulated oocyte, and the isthmus and uterine cavity are usually distal to the usual fertilization site.

Question 47

The placenta is orginated from?

Accepted Answer

Answer reason: The placenta develops from the chorion frondosum (fetal component) interacting with the maternal decidua basalis. Decidua vera (parietalis) lines the remainder of the uterus and does not contribute to the placenta, and decidua capsularis overlies the embryo without forming placental tissue. Myocardium is unrelated. Therefore, chorion frondosum is the correct origin listed.

Question 48

Which of the following is the first Organ that develop in embryonic stage?

Accepted Answer

Answer reason: The heart is the first functional organ to develop in the embryo. The primitive heart tube forms from mesoderm around days 18–19 and begins beating and circulating blood by about day 22–23 of gestation. Neural tissue and the brain begin early patterning but are not functional organs at this stage, while the liver and kidneys differentiate later (weeks 5–10).

Question 49

Oxygenated blood is carried to the fetus by?

Accepted Answer

Answer reason: In fetal circulation, oxygenation occurs in the placenta, not the fetal lungs. The single umbilical vein carries oxygenated, nutrient-rich blood from the placenta to the fetus and directs much of it toward the inferior vena cava via the ductus venosus. In contrast, the two umbilical arteries return deoxygenated blood from the fetus back to the placenta. Therefore, oxygenated blood reaches the fetus through the umbilical vein.

Question 50

The umbilical cord develops from?

Accepted Answer

Answer reason: The definitive umbilical cord forms from the connecting stalk that contains the allantois and umbilical vessels, with contributions from the yolk sac (vitelline structures) early in development. Extraembryonic mesoderm forms Wharton’s jelly, while the amnion merely covers the cord. The chorion contributes primarily to the placenta, not the cord. Thus, yolk sac and allantois best describe the structures from which the umbilical cord develops.

Train with a large NCLEX question bank and jump into a full exam-style simulator

Embryology NCLEX Practice Test

Continue Learning