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Correct answer is (c) Fetal ejection REFLEX

Easiest explanation: Parturition is INITIATED by the FETUS and the PLACENTA. LEADING to oxytocin signaling and uterine contractions. This reflex is called fetal ejection reflex.

The correct choice is (a) immunity

The explanation: The antibodies in the COLOSTRUM help the body of the baby, which has been EXPOSED to the EXTERNAL world full of different antigens, the ability to fight. This is called immunity.

Right answer is (c) Antibodies

To elaborate: The colostrum is produced by the MAMMARY GLANDS for the first few DAYS after the baby is born. The purpose is to protect the baby from the antigens it will be exposed after entering the world for the first time. Hence it is enriched with antibodies.

Right choice is (b) Colostrum

Best explanation: The first couple of days after the onset of lactation, the milk PRODUCED from the MAMMARY GLANDS is yellowish and rich in nutrients and ANTIBODIES for the newborn baby. This is CALLED colostrum.

The correct answer is (a) lactation

The best I can EXPLAIN: Mammary gland cells develop the POTENTIAL to produce milk towards the end of pregnancy. This PROCESS is TERMED as lactation.

Right answer is (c) Signal from fetus and PLACENTA → Release of oxytocin → Uterine contractions → RISE in oxytocin SECRETION → Powerful contractions → Parturition

The explanation: Parturition starts with the signal released by the fetus and the placenta. These act on the pituitary to release oxytocin. Oxytocin acts as a stimulant leading to contractions of the uterine muscles. The uterine contractions feedbacks to release more oxytocin from the pituitary. This results in more powerful contractions of the uterus until the baby is DELIVERED in the process of parturition.

Correct choice is (b) OXYTOCIN

For explanation I would say: Oxytocin is the stimulant released from anterior pituitary to increase contractions of the UTERINE wall. DECREASED levels of oxytocin can result in the inability to push the baby out. In such scenarios, the patient is injected with intravenous oxytocin to induce uterine contractions to deliver the baby.

Right ANSWER is (a) neuroendocrine mechanism

The explanation is: Two major processes induce the contractions of the UTERINE wall during parturition. The hormones SECRETED from the PITUITARY and placenta alongside the reflexes induced by the oxytocin function to stimulate the muscle continuously. Thus this is a neuroendocrine PROCESS.

The correct OPTION is (c) parturition

Explanation: Parturition, ALSO known as CHILDBIRTH, is the process in which vigorous contraction of the UTERUS is induced, leading to the expulsion of a fetus. It includes preparation of myometrium and cervix during PREGNANCY, uterine preparation, uterine contraction, and involution.

Correct option is (a) Mesoderm

The best explanation: HEART is the first ORGAN to develop in the fetus. It is DERIVED from the mesodermal cells. After GASTRULATION, this DIFFERENTIATES into mesothelium, endothelium, and myocardium.

The correct answer is (b) stem CELLS

The best I can explain: The stem cells are a POPULATION of cells within the inner CELL mass that POSSESS the ability to GIVE rise to an entire organism. They have a property called stemness, which gives them this ability.

Right answer is (b) potency

The explanation is: Development is the PROCESS that LEADS to the FORMATION of an organism from the zygote. Potency is the ability of a cell to DIFFERENTIATE into another cell type. Stemness is the potential of a cell to divide indefinitely and also differentiate to multiple DIFFERENT cell types.

The CORRECT choice is (c) Mesoderm

Easiest explanation: ECTODERM and endoderm are the first layers that arise as a result of the differentiation of the IMPLANTED BLASTOCYST. Eventually, a third layer separating ectoderm from the endoderm arises. This layer is called mesoderm.

Correct option is (a) ectoderm, endoderm

The explanation: The PROCESS of implantation is FOLLOWED by the RAPID differentiation of the inner mass of cells of the blastocyst. These cells DIFFERENTIATE into the outer layer of ectoderm and the inner layer of endoderm. Mesoderm arises later.

The correct answer is (d) Lactation

The explanation: The MATERNAL increase in the hormones is RESPONSIBLE for the development and GROWTH of the fetus, maintenance of pregnancy, and the changes in metabolism in mother essential for the proper nourishment of fetus. Lactation is not a part of pregnancy. It occurs after the BABY has been DELIVERED.

Right OPTION is (c) second TRIMESTER

For explanation I would say: Trimesters are periods of THREE MONTHS’ post-pregnancy. Fetal movements can be observed STARTING five months’ post-pregnancy i.e., during the second trimester.

Right CHOICE is (b) FIRST trimester

To explain I would say: Limbs and digits, ALONG with EXTERNAL GENITALIA, are formed during the first trimester. This is a period of 12 weeks after pregnancy.

The correct choice is (a) Progesterone

To EXPLAIN I would SAY: To use hormone as a detector for PREGNANCY, the hormone should be released only during pregnancy. Such hormones are HPL, hCG, and relaxin. Progesterone is not specific to pregnancy and hence cannot SERVE the purpose.

Right option is (a) HEART

To EXPLAIN I would SAY: The heart is the first organ to form in the developing fetus. It is formed after one month of pregnancy. The BRAIN takes more time to develop.

Correct option is (c) Relaxin

To EXPLAIN: hCG, hPL, and relaxin are released only during pregnancy. hCG and hPL are released by the PLACENTA. The ovary RELEASES relaxin.

Correct CHOICE is (b) False

The explanation is: Exocrine glands are glands with ducts that pour their secretions via a duct. ENDOCRINE glands DIRECTLY release their secretions into the bloodstream or onto a tissue. In this SENSE, the placenta is an endocrine gland as it lacks ducts.

Right OPTION is (a) Relaxin

For explanation: Placenta is ALSO an endocrine gland. It PROVIDES various hormones like hCG (Human Chorionic Gonadotrophin), hPL (Human Placental Lactogen), Estrogen, and Progesterone. Relaxin is not a placental HORMONE. It is released from the ovary.

Correct option is (c) Supply of carbon dioxide to the FETUS

To explain I WOULD say: Placenta connects the maternal system to the fetal system. It provides nutrients for the fetus. It also removes the excretory products that would be harmful to it. It also provides a GASEOUS exchange by providing oxygen and removing carbon dioxide.

The CORRECT choice is (b) Umbilical cord

The explanation is: Placenta provides nutrition and a medium for the removal of wastes for the fetus. This occurs VIA the umbilical cord, which connects the fetus to the placenta. The cord remains attached even after the birth and NEEDS to be REMOVED surgically.

Right choice is (c) Placenta

To ELABORATE: Trophoblasts PROJECT CHORIONIC VILLI into the endometrium to derive nutrition from the uterine wall. The uterine tissue, in turn, surrounds it along with the blood vessels. These two tissues interdigitate to form the placenta.

The correct ANSWER is (C) Blastocoel

Easy explanation: The CELL divisions after the morula STAGE are slightly asymmetric. This leads to the formation of a cavity in the blastula. This cavity is called blastocoel and is critical for the migration of cells that occurs during gastrulation.

The correct answer is (d) Morula

The explanation is: Zygote divides rapidly via the PROCESS of cleavage. Each DIVISION doubles the number of CELLS. The 8 to 16 cell stage embryo starts attaining a bolus shape and is hence called a morula. The morula LATER transforms into a blastula and then a blastocyst.

The correct choice is (C) Covering of the blastomere by the uterine wall

To ELABORATE: Fertilization is the fusion of male and female gametes. Cleavage is the rapid divisions that LEAD to the formation of a zygote. Implantation is the process that leads to the covering of the blastomere by the uterine endometrium.

Correct option is (c) inner cell MASS

The explanation: The trophoblast, along with the UTERINE cell WALL, gives rise to the PLACENTA. The inner cell mass, on the other hand, differentiates to form the embryo.

The correct option is (d) EMBRYO

For explanation: INNER cell mass is the INTERNAL layer of blastomere. Upon attachment of blastomere, the inner cell mass undergoes differentiation to form the embryo.

Correct option is (b) Trophoblast

Explanation: The blastomere is COMPOSED of an INTERNAL INNER mass of cells and an external layer of cells CALLED the trophoblast. The trophoblast attaches to the ENDOMETRIUM and forms the fetal part of the placenta.

The CORRECT option is (b) Trophoblast

Easiest EXPLANATION: BLASTOCYST is formed from blastomeres. It is organized into an outer layer of cells CALLED trophoblast and an inner layer of cells called inner CELL mass.

The correct answer is (c) BLASTOMERES

To elaborate: Zygote undergoes cleavage PRODUCING an exponential increase in cell MASS. These new daughter cells formed are called blastomeres. They form a blastula with a BLASTOCOEL cavity ENCLOSED in between.

Right choice is (B) CLEAVAGE

Best explanation: As the zygote is formed, it passes through ISTHMUS towards the uterus. Through the PASSAGE, it UNDERGOES rapid mitotic divisions. This is called cleavage.

Correct option is (d) Zona radiata

Explanation: The egg nuclei and CYTOPLASM is ENVELOPED by VARIOUS layers which prevent DESICCATION and provides nourishment and suitable habitat for the DEVELOPMENT of the egg. The sperm has to break these barriers to reach the egg nuclei.

Right OPTION is (b) False

The best explanation: The HUMAN males have XY as their sex chromosomes. Thus upon undergoing meiosis, the PROBABILITY of sperm having an X chromosome is the same as that of having a Y chromosome. There is no natural bias here. The lower sex RATIO hence cannot be accounted to such a biological phenomenon.

The correct choice is (b) SPERM has Y chromosome

Explanation: The sex in humans is determined by the sex chromosome that the male GAMETE carries. The females are XX hence MEIOSIS RESULTS in all ova having X chromosome. Males are XY and 50% sperms have X and 50% have Y. Thus the DETERMINING factor that makes a baby male is Y chromosome in the sperm.

Right ANSWER is (c) SPERM: 23; Egg: 23; Zygote: 46

To ELABORATE: Sperm and egg are haploid CELLS hence have only one set of chromosomes. Zygote on the other hand is DIPLOID thus has 46 chromosomes.

Right option is (b) diploid ZYGOTE

The best explanation: The FUSION of sperm and EGG restores the chromosome number. The new cell is called zygote having the potential to develop into a new ORGANISM.

Correct OPTION is (B) Zona pellucida

To elaborate: The sperm contacts the egg cell at zona pellucida. The zona pellucida then UNDERGOES chemical changes which renders egg insusceptible to further encounters with another sperm. This is ESSENTIAL to ensure that only a single sperm fertilizes the egg.