Human Reproduction MCQ Quiz - Objective Question with Answer for Human Reproduction - Download Free PDF

Key Points

• Appearance of hair on the head of a human embryo typically occurs during the 5th month of pregnancy.
• By the 5th month, the embryo develops lanugo, which is fine, soft hair that covers the body, including the head.
• Lanugo plays a crucial role in helping to regulate the fetus’s body temperature within the womb.
• This hair gradually disappears before birth or shortly after birth, as it is replaced by vellus or terminal hair.

Important Points

• The development of hair follicles begins early in the embryonic stage, but visible hair growth on the head starts during the 5th month.
• The growth of hair is part of the overall development of the fetus, including skin and appendages.
• Lanugo is a temporary protective mechanism for the fetus and is not permanent.
• Proper fetal development during this phase is crucial and can be influenced by maternal nutrition, health, and genetics.

The correct answer is They are fraternal twins.

Concept:

• Twins are classified into two main types: monozygotic (identical) and dizygotic (fraternal).
• Monozygotic twins develop from a single fertilized egg that splits into two embryos, leading to identical genetic material. These twins are always of the same sex.
• Dizygotic or fraternal twins occur when two separate eggs are fertilized by two different sperm cells. As a result, they share approximately 50% of their genetic material, similar to regular siblings, and can be of the same or different sexes.

Explanation:

• They are monozygotic twins: This is incorrect because monozygotic twins are genetically identical and always of the same sex. 
• They are fraternal twins: This is correct. Fraternal twins are the result of two separate eggs being fertilized by two different sperm cells. They can be of different sexes, as in this case, where the twins are a boy and a girl.
• They were conceived through in vitro fertilization: This is incorrect. While in vitro fertilization (IVF) can increase the likelihood of twins, there is no indication in the question that IVF was involved. Twins can occur naturally as well.
• They have 75% identical genetic content: This is incorrect. Fraternal twins share 50% of their genetic material, the same as any other siblings. 

The correct answer is Menarche 

Explanation: 

• The reproductive cycle in the female primates (e.g. monkeys, apes and human beings) is called menstrual cycle.
• The first menstruation begins at puberty and is called menarche.
• In human females, menstruation is repeated at an average interval of about 28/29 days, and the cycle of events starting from one menstruation till the next one is called the menstrual cycle.
• Menarche usually occurs between the ages of 9 and 15, though the average age is around 12 or 13. Various factors can influence the timing of menarche, including genetics, nutritional status, overall health, and environmental factors.

Other Options:

• Menopause: Menopause is the stage in a woman’s life when menstrual periods permanently stop, and she is no longer able to conceive naturally. This typically occurs between the ages of 45 and 55, with the average age being around 51. Menopause is diagnosed after a woman has gone 12 consecutive months without a menstrual period. This stage marks the end of the reproductive years and is associated with a decrease in the production of hormones such as estrogen and progesterone by the ovaries.
• Diapause: Diapause refers to a period of suspended or delayed development in insects, some invertebrates, and certain fish or plants that allows them to survive unfavorable environmental conditions.
• Ovulation: Ovulation is the process in the menstrual cycle where a mature egg is released from one of the ovaries. Typically, this occurs around the midpoint of the menstrual cycle, about 14 days before the start of the next menstrual period in a typical 28-day cycle. After its release, the egg travels down the fallopian tube, where it may be fertilized by sperm. If fertilization does not occur, the egg disintegrates, and the menstrual period follows as the uterine lining sheds.

Concept:

• Gametogenesis is the process of forming mature reproductive cells, or gametes, in both males and females. 
• Female gametogenesis, or oogenesis, starts early in fetal development and involves extended periods of meiotic arrest.
• Male gametogenesis, or spermatogenesis, begins at puberty and proceeds continuously throughout a male's reproductive lifespan.

Fig: Spermatogenesis and Oogenesis

Explanation:

• A. The reductive division for the human female gametogenesis starts earlier than that of the male gametogenesis: This statement is correct. In females, oogenesis starts during fetal development, with primary oocytes entering the first meiotic division and undergoing arrest in prophase I until puberty. Meanwhile, spermatogenesis in males starts at puberty.
• B. The gap between the first meiotic division and the second meiotic division is much shorter for males compared to females: This statement is correct. In males, once spermatogenesis begins, it proceeds rapidly through both meiotic divisions without long delays. In females, after the first meiotic division (which completes at ovulation), the second meiotic division is only completed upon fertilization, leading to a prolonged gap.
• C. The first polar body is associated with the formation of the primary oocyte: This statement is incorrect. The first polar body is produced during the first meiotic division of the primary oocyte, not during its initial formation.
• D. Luteinizing Hormone (LH) surge leads to disintegration of the endometrium and onset of menstrual bleeding: This statement is incorrect. The LH surge triggers ovulation and the formation of the corpus luteum. Menstrual bleeding is caused by the fall in progesterone and estrogen levels, which happens when the corpus luteum degenerates if pregnancy does not occur.

The correct answer is A, C, D and E Only

Concept:

• Human pregnancy is a complex process divided into three trimesters, each contributing significantly to the development of the fetus. By the end of the embryonic phase (around 8 weeks), major organ systems begin to form.
• First month: In the first month, the heart begins to form and function.
  • The first sign of growing foetus may be noticed by listening to the heart sound carefully through the stethoscope.
• Second month: By the end of the second month, the foetus develops limbs and digits.
• Third month end: By the end of the third month, the major organ systems. For example, the limbs and external genital organs are well-developed.
• Fifth month: The first movements of the foetus and appearance of hair on the head are usually observed during the fifth month.
• Sixth month: By the end of the sixth month, the eyelids separate and the eyes begin to open and, the body is covered with fine 

Explanation:

• Statement A: "In human pregnancy, the major organ systems are formed at the end of 12 weeks" is correct. By 12 weeks, the major organ systems are developed.
• Statement B: "In human pregnancy the major organ systems are formed at the end of 8 weeks" is incorrect. During the embryonic phase (first 8 weeks), the major organ systems begin to form and not developed.
• Statement C: "In human pregnancy heart is formed after one month of gestation" is correct. The heart is one of the first organs to form, and its development starts early. By the end of the fourth week, the primitive heart tube begins to beat and pump blood, establishing early circulation.
• Statement D: "In human pregnancy, limbs and digits develop by the end of the second month" is correct. Limb buds appear during the fourth week, and by the end of the second month (8 weeks), digits begin to form as part of the embryonic development process.
• Statement E: "In human pregnancy the appearance of hair usually observed in the fifth month" is correct. Hair follicles start to develop by the fifth month of gestation, and fine hair called lanugo covers the fetus's skin to protect it.

The correct answer is Male gamete.

Key Points

• Sperm or spermatozoa is a gamete (sex cell) produced in the male reproductive system.
• It is a mobile cell with one goal - to fertilize a female egg.
• Each sperm contains the entire genome of the male that produced it.
• Combined with the female genome contained in the egg, a zygote is formed - a single pluripotent stem cell containing the fused male and female genomes.
• Sperm cells were first described in the late 17th century by Antonie van Leeuwenhoek.

Additional Information

• Isogamete:
  • Isogamete is a gamete that is similar in shape, size, and behavior to another gamete with which it can produce a zygote.
  • They are also known as homogametes.
• Female gamete:
  • Female gametes are produced in the ovary. It is called an egg or egg.
  • Each month, the female produces one egg during her menstrual cycle.
• Gamete:
  • A gamete is a haploid cell that fuses with another haploid cell during fertilization in sexually reproducing organisms.
  • Gametes are reproductive cells of an organism, also known as sex cells.

The correct answer is Testes.

Key Points

• Testosterone is the only male sex hormone present in the human body, which causes physical changes in puberty, increases bone density and muscle mass, growth of facial, pubic, and body hair, deepening of the voice, and also responsible for sexual and reproductive development.
• Testosterone is the main sex hormone in men, which is naturally produced in the testes and in small amounts by the adrenal glands.
• Testosterone belongs to a class of male hormones called androgens, which are also known as steroids.
• The production of male sex hormones is mainly controlled by the hypothalamus and pituitary gland.
• The testosterone levels gradually decrease with age, which results in impotence, shrinking of testes, low sperm count, depression, mood swings, irritability, etc.

Additional Information

• The pituitary gland is a small pea-sized gland that plays a major role in regulating vital body functions and general wellbeing.
  • It is referred to as the body's 'master gland' because it controls the activity of most other hormone-secreting glands. 
  • The pituitary gland is a small gland that sits in the sella turcica, a bony hollow in the base of the skull, underneath the brain and behind the bridge of the nose.
• Adrenal glands, also known as suprarenal glands, are small, triangular-shaped glands located on top of both kidneys.
  • Adrenal glands produce hormones that help regulate your metabolism, immune system, blood pressure, response to stress and other essential functions.
• The ovary is an organ found in the female reproductive system that produces an ovum.
  • When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm.
  • There is an ovary found on each side of the body.

Key Points

• The placenta is an organ that develops in the uterus during pregnancy.
• It facilitates the supply of oxygen and nutrients to the embryo.
• It removes carbon dioxide and excretory/waste materials produced by the embryo.
• Placenta acts as an endocrine tissue and produces hormones:
  • Human chorionic gonadotropin (hCG)
  • Human placental lactogen (hPL)
  • Estrogens
  • Progestogens
• These hormones work together to control the growth and development of the placenta and the fetus.
• They act on the mother to support the pregnancy and prepare for childbirth.
• Placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo.

Explanation:

• Androgen is the male sex hormone that is secreted by the Leydig cells of the testis in males.
• It plays an important role in spermatogenesis process.
• It also helps in developing male secondary sexual characters.

Hence, the correct answer is option 3.

Concept:

• Vigorous contraction of the uterus at the end of pregnancy causes expulsion/delivery of the foetus. This process of delivery of the foetus (childbirth) is called parturition.

Explanation:

• Foetal Ejection reflex - 
• The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex.
• This triggers the release of oxytocin from the maternal pituitary.
• Oxytocin then acts on the uterine muscle and causes stronger uterine contractions, which in turn stimulates the further secretion of oxytocin.
• The stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger and stronger contractions.
• This leads to the expulsion of the baby out of the uterus through the birth canal – parturition.

Additional Information

• Prolactin: It is also called lactotrophic hormone. It regulates the growth and milk formation of mammary glands.
• Estrogen, or oestrogen: It is a sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics.
• Relaxin as the name suggests is used to keep the smooth muscles of the uterus relaxed. It is secreted in large amounts during parturition.

The correct answer is option 2.

Concept: 

• It is to be noted that the male reproductive organ system produces, maintains, and transfers sperm (male reproductive cells) and protective fluid (semen).
• It produces and secretes sex hormones for males.
• It helps to maintain secondary sexual characteristics in human males.

Explanation:

Option 1: 

• The epididymis is the male sex accessory duct.
• The main function of the epididymis is to store the sperms for maturation and transport it to vas deferens. It is a coiled tube attached to both the testes through vasa efferentia. It connects the testes to vas deferens.
• Therefore, this is the incorrect answer.

​Option 2: ​

• The epididymis is made up of three parts, namely: (i) Caput (ii) Corpus (iii) Cauda.
• The epididymis stores the sperms for some time only.
• From cauda epididymis, a partially coiled tube called vas deferens.

• The vas deferens is a continuation of the cauda epididymis (tail part of epididymis).

• It is about 40 cm long and slightly coiled at first, but becomes straight as it enters the abdominal cavity through the inguinal canal.

• Here, it passes over the urinary bladder, curves around the ureter and joins a duct from seminal vesicle and opens into the urethra as the ejaculatory duct. These ducts store and transport the sperms from the testis to the outside through urethra.

• Therefore, the correct answer is option 2.

  

• Efferent ductules are small, highly convoluted and delicate tubules that connect rete testis cavities with the head of the epididymis.
• Therefore, this is the incorrect answer.

Option 4: 

• The ureter is a narrow tube that originates from the kidney and reaches the bladder.
• Urine is transported from the kidneys to the urinary bladder via the ureters.
• Therefore, this is the incorrect answer.

Key Points

• Prostate gland -
  • It is one of the male accessory gland that is located below the urinary bladder in front of the rectum.
  • It produces seminal fluid that forms a part of  semen. 
  • This fluid helps in nourishing the sperms.
• Leydig cells - 
  • Leydig cells or interstitial cells are found in between the seminiferous tubules of the testes.
  • These cells synthesize and secrete testicular hormones called androgens.
• Ejaculatory duct - 
  • It is one of the ducts of male reproductive system.
  • It is formed when the vas deferens ascends up into the abdomen and loops over the urinary bladder and is joined by a duct from seminal vesicle.
  • This ejaculatory duct may store and transport sperm into the urethra.
• Penis - 
  • It is the external genitalia in human males.
  • It consists of a special tissue that helps in erection to facilitate insemination.

Corrected Table:

Hence, the correct answer is option 1. 

Concept:

• Spermatogenesis is the process by which sperm are produced in the testis in males.
• In the testis, at puberty sperms are produced from the immature germ cells called spermatogonia.
• Spermatogenesis takes place under the influence of the hypothalamic hormone - Gonadotropin Releasing Hormone (GnRH).
• Sperms (spermatozoa) thus produced are the microscopic haploid male gametes. During the process of fertilization, the union of male and female gametes gives rise to a diploid zygote.
• A sperm is a slender, motile and flagellated structure that is about 60µ in length.
• A sperm comprises a head, a middle piece and a tail.​

​

Important Points

• Head -
  • ​The haploid nucleus of sperm is present in the sperm head.
  • The nucleus comprises a vacuole.
  • The anterior portion of the nucleus is covered by a cap-like structure called the acrosome.
  • The acrosome covers the anterior two-thirds of the nucleus.
  • The acrosome is filled with an enzyme that helps in the fertilization of the ovum.
• Midpiece -
  • ​The middle region of the sperm comprises of compact helical mass of mitochondria.
  • The mitochondria provide energy for the movement of the tail.
  • This in turn facilitates sperm motility which is essential for fertilization.
  • Thus the middle piece of the sperm in Human Reproduction helps to produce energy for sperm motility.
• ​Tail - 
  • ​The sperm tail facilitates the movement of the sperm cell by moving in a whip-like manner.
• ​A plasma membrane envelops the whole body of the sperm.
• The plasma membrane helps protect the sperm against extracellular injuries.

Additional Information

• ​The Sertoli cells are present in the seminiferous tubules of the testis.
• They provide nourishment to the developing sperm and are hence also known as nurse cells.

So the correct answer is option 3 (to produce energy for sperm motility).

Concept:

• Fertilization is the process of fusion of the cytoplasm and pronuclei of the male (sperm) and female (ovum) gametes.
• Fertilization takes place in the ampulla region of the fallopian tube.
• During fertilization, once the sperm enters the secondary oocyte, the second meiotic division gets completed in the secondary oocyte.
• The secondary oocyte is now known as the matured ovum.
• The union of male and female gametes gives rise to a diploid zygote.

Important Points

EMBRYONIC DEVELOPMENT:

• The zygote formed during fertilization undergoes rapid mitotic division.
• These divisions are referred to as cleavage divisions.
• The cleavage divisions take place during the passage of the zygote from the fallopian tube to the uterus.
• The daughter cells arising out of cleavage are known as blastomeres.
• Successive cleavage divisions give rise to a ball of blastomeres.
• The blastomeres are enclosed by zona pellucida. This structure is referred to as morula.
• Morula is differentiated into an inner mass of cells that is surrounded by an outer layer of cells.
• The next embryonic stage is called a blastula.
• The blastula is formed by the dynamic rearrangement of blastomeres. This rearrangement of blastomeres gives rise to the formation of a central cavity called the blastocoel.
• Blastocoel is filled with fluid. 
• Once the zona pellucida (outer envelope) disintegrates, it facilitates rapid growth of the blastula.
• The blastocoel expands due to an increase in fluid content. This stage is referred to as a blastocyst.
• The blastocyst comprises an inner cell mass and a thin outer wall called a trophoblast that is separated from each other by the blastocoel.
• The inner cell mass (embryoblast or blastodermic vesicle) forms the body of the embryo. The trophoblast forms the fetal portion of the placenta.
• At this stage, the embryo gets implanted in the endometrium. Implantation takes place with the help of the placenta.
• Blastula later gets converted to the next embryonic stage called gastrula by gastrulation.
• Gastrula is the two-layered stage comprising ectoderm and endoderm.
• At the end of embryonic development, a fetus with three germinal layers - ectoderm, mesoderm and endoderm - is formed.

  ​

• Thus, the correct sequence of embryonic development is as follows:

Fertilization → Second meiotic division → Zygote → Cleavage → Morula → Blastula → Blastocyst (comprises of inner cell mass and trophoblast) → Gastrula

Hence, the correct answer is option 1 (Cleavage → Morula → Blastocyst → Trophoblast and inner cell mass).

Concept:-

• Sperm: it is a male reproductive cell. Each day about 300 million sperm complete spermatogenesis. The human sperm cell is about 70 µm long.
• The nucleus in the head – contains the 23 chromosomes.
• It is the head that blinds to the egg at fertilization.

Ovum: it is a maternal haploid gamete and is primarily concerned with receiving the sperm and is determined to develop into a fully developed multicellular organism after fertilization or without fertilization.

Explanation:

• Hyaluronidase: it is a family of enzymes that degrade hyaluronic acid. It is found in human testes, in bacterial cultures as a by-product, or in the heads of leeches and snake venoms.
• Hyaluronidase enzyme break down the outer membrane of the ovum called zona pellucida.

Additional Information

• Glucocerebrosidase: is a normal component of cell membranes. As senescent cells are degraded, macrophages engulf the cellular debris as a part of routine cell turnover.
• Protease: enzymes involved in the degradation of proteins are called proteases or proteolytic enzymes.
• Amylase: amylases are starch degrading enzymes.

Concept-

After fertilization, the fertilized egg undergoes rapid mitotic divisions are called cleavage.

• Cleavage produces a solid ball of small blastomeres and the embryo now looks like a mulberry is known as a morula.
• The morula, later on, changes into a blastula. The blastula of mammals is called a blastocyst.
• An embryo with about 64 cells is formed within the cell mass. This cavity is called blastocoel and an embryo is called a blastocyst which is composed of an outer envelope of cells, the trophoblast, and inner cell mass.

Explanation-

• As a result of cleavage activities, the zygote moves towards the uterus and forms 2,4,8,16 daughter cells called blastomeres.
• The embryo with 8 to 16 blastomeres is called a morula.