//M3//QN1//SUB//DL0

Mention the main reprodutive events in humans.

//X

The reproductive events in humans include -
(i) Formation of gametes (gametogenesis), i.e., sperms in males and ovum in females,
(ii) Transfer of sperms into the female genital tract (insemination).
(iii) Fusion of male and female gametes (fertilisation).
(iv) Formation of zygote.
(v) Formation and development of blastocyst
(vi) Attachment of blastocyst to the uterine wall (implantation).
(vii) Embryonic development (gestation) and
(viii) Delivery of the baby (parturition).

//M0//QN2//SUB//DL0//EQ

Draw a labeled diagram of male pelvis showing reproductive system.

//X

//M3//QN3//SUB//DL0//EQ

Describe the structure of a seminiferous tubule

OR
Explain the internal structure of testes.
OR
Explain the internal structure of Seminiferous tubules in male.

//X

Structure of testis: Each testis has about 250 compartment called testicular lobules.
Each testicular lobule contains one to three highly coiled seminiferous tubules in which sperms are produced.
Seminiferous tubule: Each seminiferous tubule is lined internally by two types of cells: male germ cells (spermatogonia) and sertoli cells.
Male germ cells :
(i) They are arranged in 4 to 8 layers.
The male germ cells undergo meiotic divisions finally leading to sperm formation.
(ii) Sertoli cells (provide nutrition to the germ cells)
They are placed between developing sperms.
(iii) Leydig cells (interstitial cells)
The regions outside the seminiferous tubules called interstitial spaces, contain small blood vessels and interstitial cells or leydig cells.
Leydig cells synthesise and secrete testicular hormones called androgens.
Other immunologically competent cells are also present in interstitial spaces.

//M2//QN4//SN//DL0

Write a short note on the structure of testes.

//X

Number : 1 pair of testes in an individual.
(1) Location : The testes are situated outside the abdominal cavity within a pouch called scrotum.
(2) Shape : In adults, each testis is oval in shape.
(3) Size : Length is about 4 to 5 cm and a width of about 2 to 3 cm.
(4) Structure : The testis is covered by a dense covering.
Each testis has about 250 compartments called testicular lobules.
Each lobule contains one to three highly coiled seminiferous tubules in which sperms are produced.
Male hormones androgens also called testosterone are produced in testes.

//M2//QN5//SUB//DL0

Give a brief account of human male external genitalia (Penis).

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The penis is the male external genitalia.
It is made up of special tissue that helps in erection of the penis to facilitate insemination.
The enlarged end of penis called the glans penis is covered by a loose fold of skin called foreskin.

//M0//QN6//SN//DL0//EQ

Write a short note on male accessory glands.

OR
What are the component of seminal fluid ?

//X

There are three accessory glands.
It includes one pair of seminal vesicle, one prostate gland and one pair of bulbourethral gland.
The combined secretions of these glands are responsible for formation of semen.
(1) Seminal vesicle : A pair of seminal vesicle is present near the base of bladder. Vas deferens joins with seminal duct and forms ejaculatory duct.
Seminal fluid is a thick, viscous, fluid, rich in nutrients like fructose, vitamin C, calcium and some enzymes.
It produces 60% fluid of semen.
(2) Prostate gland : The prostate gland, located behind the bladder, produces a milky alkaline secretion, that helps maintain and increase sperm viablity.
The prastate gland opens into the urinogenital tract by several small ducts.
(3) Bulbourethral gland : A pair of bulbourethral glands are located under the prostate gland on either side of the urethra.
Like the prostate gland, it secretes a basic alkaline fluid, which helps in the lubrication of the penis during intercourse. Also, helps the penis to become sticky.

//M4//QN7//SN//DL0//EQ

Draw a well labeled diagram of human male reproductive system which is associated with transport of sperms. OR Write a short note on male accessory ducts.

//X

The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens.
The seminiferous tubules of the testis open into the vasa efferentia through rete testis.
The vasa efferentia leaves the testis and open into epididymis located along the posterior surface of each testis.
The epididymis leads to vas deferens that ascends to the abdomen and loops over the urinary bladder.
It receives a duct from seminal vesicle and opens into urethra as the ejaculatory duct.
These ducts store and transport the sperms from the testis to the outside through urethra.
The urethra originates from the urinary bladder and extends through the penis to its external opening called urethral meatus.

//M0//QN8//SUB//DL0//EQ

Draw a well labelled diagram representing sectional view of female pelvis showing reproductive system.

//X

//M2//QN9//SN//DL0

Write a short note on human female ovaries.

OR
Describe female primary sex organ.

//X

Ovaries are the primary female sex organs.
The ovaries are located one on each side of the lower abdomen.
Each ovary is about 2 to 4 cm in length, 2 cm wide and 1 cm thick.
It is connected to the pelvic wall and uterus by ligaments.
Each ovary is covered by a thin epithelium which encloses the ovarian stroma.
The stroma is divided into two zones – a peripheral cortex and an inner medulla.
Ovary produces the female gamete (ovum) and several steroid hormones (ovarian hormones).

//M3//QN10//SN//DL0

Write a short note on oviduct, associated with ovum transport.

OR
Explain about female accessory ducts.

//X

The oviducts (fallopian tubes), uterus and vagina constitute the female accessory ducts.
(1) Structure of Oviducts :
Each fallopian tube is about 10-12 cm long.
It extends from the periphery of each ovary to the uterus.
(2) Infundibulum : The part closer to the ovary is the funnel-shaped infundibulum.
(3) Fimbriae : The edges of the infundibulum possess finger-like projections called fimbriae, which help in collection of the ovum after ovulation.
(4) Ampulla : The infundibulum leads to a wider part of the oviduct called ampulla.
(5) Isthmus : The last part of the oviduct, isthmus has a narrow lumen and it joins the uterus.

//M0//QN11//SUB//DL0//EQ

Draw a labeled diagram of a section through ovary.

//X

//M3//QN12//SN//DL0

Write a short note on female external genitalia.

//X

It includes mons pubis, labia majora, labia minora, hymen, clitoris
(a) Mons Pubis : It is a cushion of fatty tissue covered by skin and pubic hair.
(b) Labia majora : These are fleshy folds of tissue, which extend down from the mons pubis and surround the vaginal opening.
(c) Labia minora : These are paired folds of tissue under the labia majora.
(d) Hymen : The opening of the vagina is often covered partially by a membrane called “hymen”.
(e) Clitoris : It is a tiny finger-like structure which lies at the upper junction of the two
labia minora above the urethral opening.
Clitoris differs from penis due to absence of
reproductive duct.

//M4//QN13//SUB//DL0//EQ

Draw a labelled diagram of human female reproductive system and explain uterus / womb.

//X

Structure of Uterus :
The uterus is single and it is also called womb.
The shape of the uterus is like an inverted pear.
It is supported by ligaments attached to the pelvic wall.
The wall of the uterus has three layers:

(i) Perimetrium : The external thin membranous perimetrium.

(ii) Myometrium : The middle thick layer of smooth muscle, myometrium.

(iii) Endometrium : inner glandular layer called endometrium that lines the uterine cavity.

The endometrium undergoes cyclic changes during menstrual cycle while the myometrium exhibits strong contraction during delivery of the baby.
The uterus opens into vagina through a narrow cervix.
The cavity of the cervix is called cervical canal which along with vagina forms the birth canal.

//M0//QN14//SUB//DL0//EQ

With a labelled diagram describe the structure of mammary gland.

OR
Write the structure of mammary gland (Diagram is not required).

//X

A functional mammary gland is a characteristic of all female mammals.
The mammary glands are paired structures (breasts) that contain glandular tissue and variable amount of fat.
The glandular tissue of each breast is divided into 15-20 mammary lobes containing clusters of cells called alveoli.
The cells of alveoli secrete milk, which is stored in the cavities (lumens) of alveoli.
The alveoli open into mammary tubules.
The tubules of each lobe join to form a mammary duct.
Several mammary ducts join to form a wider mammary ampulla which is connected to lactiferous duct through which milk is sucked out.

//M4//QN15//SUB//DL0

Explain human female reproductive system. (Diagram not required)

//X

The female reproductive system consists of a pair of ovaries alongwith a pair of oviducts, uterus, cervix, vagina and the external genitalia located in pelvic region.
(i) Ovary : Ovaries are the primary female sex organs that produce the female gamete (ovum) and several steroid hormones (ovarian hormones).
The ovaries are located one on each side of the lower abdomen.
Each ovary is about 2 to 4 cm in length and is connected to the pelvic wall and uterus by ligaments.
Each ovary is covered by a thin epithelium which encloses the ovarian stroma.
The stroma is divided into two zones – a peripheral cortex and an inner medulla.
(ii) Oviduct : The fallopian tubes, uterus and vagina constitute the female accessory ducts.
Each fallopian tube is about 10-12 cm long and extends from the periphery of each ovary to the uterus (Figure 2.3b), the part closer to the ovary is the funnel-shaped infundibulum.
The edges of the infundibulum possess finger-like projections called fimbriae, which help in collection of the ovum after ovulation.
The infundibulum leads to a wider part of the oviduct called ampulla.
The last part of the oviduct, isthmus has a narrow lumen and it joins the uterus.
(iii) Uterus : The uterus is single and is also called womb.
The shape of the uterus is like an inverted pear. It is supported by ligaments attached to the pelvic wall.
The uterus opens into vagina through a narrow cervix.
The cavity of the cervix is called cervical canal which alongwith vagina forms the birth canal.
The wall of the uterus has three layers of tissue.
The external thin membranous perimetrium, middle thick layer of smooth muscle, myometrium and inner glandular layer called endometrium that lines the uterine cavity.
The endometrium undergoes cyclic changes during menstrual cycle while the myometrium exhibits strong contraction during delivery of the baby.
(iv) External genitalia : The female external genitalia include mons pubis, labia majora, labia minora, hymen and clitoris.

//M2//QN16//SN//DL0//EQ

Write a short note on sperm (With a labelled diagram).

OR
Draw a labelled diagram of sperm.

//X

The sperm is a microscopic structure composed of a head, neck, a middle piece and a tail.
A plasma membrane envelops the whole body of sperm.
(i) Head : The sperm head contains an elongated haploid nucleus, the anterior portion of which is covered by a cap-like structure, acrosome.
The acrosome is filled with enzymes that helps in fertilisation with the ovum.
(ii) Middle Piece : The middle piece possesses numerous mitochondria, which produce energy for the movement.
(iii) Tail : Tail that facilitate sperm motility essential for fertilisation.
The human male ejaculates about 200 to 300 million sperms during a coitus, of which, for normal fertility, at least 60 per cent sperms must have normal shape and size and at least 40 per cent of them must show vigorous motility.

//M0//QN17//SUB//DL0//EQ

Write two major functions each of testis and ovary.

//X

Functions of testis :
(1) Testis produces spermatozoa which are male gametes.
(2) In testis, the male sex hormone testosterone is produced.
Functions of ovary :

(1) The ovary produces ovum by the process of oogenesis.

(2) Graafian follicles in the ovary produce a female sex hormone called estrogen.

//M0//QN18//SUB//DL0//EQ

Draw a labeled diagram of a Graafian follicle.

//X

//M2//QN19//SUB//DL0//EQ

How spermiogenesis and spermiation differ from each other?

OR
Define spermiogenesis and spermiation.

//X

Spermiogenesis : It is a process by which spermatids are transformed into spermatozoa or mature sperm cells.
Spermiation : It is the process of releasing spermatozoa from the seminiferous tubules.

//M4//QN20//SN//DL0//EQ

What is spermatogenesis? Briefly describe the process of spermatogenesis.

OR
Write a short note on hormonal regulation of spermatogenesis.
OR
Explain the structure of sperm and define spermiogenesis and spermiation.OR Name the hormones involved in regulation of spermatogenesis.
OR
Explain the process of spermatogenesis

(Diagram is not required).

OR
According to spermatogenesis (i) Development of sperm from primary spermatocytes. Explain it. (ii) Role of hormones which are secreted from anterior part of pituitary gland. (iii) Structure of sperm (Diagram is not necessary)

//X

Spermatogenesis is a process by which mature sperm cells are produced from immature male germ cells (spermatogonia) in testes. It begins at puberty.
There are following three steps in the formation of spermatids from spermatogonia.
The spermatogonia (sing. spermatogonium) are present on the inner wall of seminiferous tubules.
(1) Proliferative Phase : They multiply by mitotic division and increase in number.
Each spermatogonium is diploid and contains 46 chromosomes.
Some of the spermatogonia called primary spermatocytes, periodically undergo meiosis.
(2) Growth Phase : Some of the spermatogonia increase in size by accumulating nourishing materials from the germinal cells and are called primary spermatocyte.
(3) Maturation Phase : A primary spermatocyte completes the first meiotic division (reduction division) leading to formation of two equal, haploid cells called secondary spermatocytes, which have only 23 chromosomes each.
The secondary spermatocytes undergo the second meiotic division to produce four equal, haploid spermatids. The number of chromosome in each spermatid is 23.
The middle part of the sperm contains thousands of mitochondria providing energy for movement.
Effect of hormone : Spermatogenesis starts at the age of puberty due to significant increase in the secretion of gonadotropin releasing hormone (GnRH). This is a hypothalamic hormone.
The increased levels of GnRH then act at the anterior pituitary gland and stimulate secretion of two gonadotropins – luteinising hormone (LH) and follicle stimulating hormone (FSH).
LH : LH acts at the Leydig cells and stimulates synthesis and secretion of androgens. Androgens, in turn, stimulate the process of spermatogenesis.
FSH : FSH acts on the Sertoli cells and stimulates secretion of some factors which help in the process of spermiogenesis.
Spermiogenesis : The spermatids are transformed into spermatozoa (sperms) by the process called spermiogenesis.
Mature sperm contains head, neck, middle part & tail.
Sperm contains haploid nucleus, which has anterior cap like structure (acrosome), rich in enzyme and helps in the fertilisation with ovum.
After spermiogenesis, sperm heads become embedded in the sertoli cells, and are finally released from the seminiferous tubules by the process called spermiation.

//M4//QN21//SUB//DL0//EQ

What is oogenesis? Give a brief account of oogenesis. (Chart is required). Explain oogenesis up to development of primary follicle & ovulation with chart / without chart.

OR
Explain the development of mature gamete in female.

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The process of formation of a mature female gamete is called oogenesis.
It is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each fetal ovary; no more oogonia are formed and added after birth.
These cells (oogonia) start dividing and enter into prophase-I of the meiotic division and get temporarily arrested at that stage, called primary oocytes.
Each primary oocyte then gets surrounded by a layer of granulosa cells and is called the primary follicle. A large number of these follicles degenerate during the phase from birth to puberty. Therefore, at puberty only 60,000 - 80,000 primary follicles are left in each ovary.
At puberty, the primary follicles get surrounded by more layers of granulosa cells and a new theca and are called secondary follicles.
The secondary follicle soon transforms into a tertiary follicle which is characterised by a fluid filled cavity called antrum. The theca layer is organised into an inner theca interna and an outer theca externa.
It is at this stage that the primary oocyte within the tertiary follicle grows in size and completes its first meiotic division. It is an unequal division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body.
The secondary oocyte retains bulk of the nutrient rich cytoplasm of the primary oocyte.
The tertiary follicle further changes into the mature follicle or Graafian follicle.
The secondary oocyte forms a new membrane called zona pellucida surrounding it.
The Graafian follicle now ruptures to release the secondary oocyte (ovum) from the ovary by the process called ovulation.
During fertilisation, sperm fuses with secondary Oocyte which stimulates its division, releasing secondary polar body.

//M2//QN22//SUB//DL0

Can you identify major differences between oogenesis and spermatogenesis?

//X

Spermatogenesis

Oogonesis

Spermatogenesis starts at Puberty and continues till death.

(1)

Oogenesis is initiated during the embryonic development stage and get temporarily arrested, then at puberty starts again, till menopause it continues.

(1)

It is continuous process forming millions of sperms.

(2)

From puberty to menopause, every month one egg is released.

(2)

Primary spermatocyte forms in proliferative phase.

(3)

Primary oocyte forms in proliferative phase.

(3)

After meiosis, Primary spermatocyte gives rise to four equal sized spermatids.

(4)

Primary oocyte undergoes meiosis and give rise to one larger secondary oocyte and smaller polar body.

(4)

This process remains continue (after first meiosis).

(5)

This process remains inhibited till the fertilization (after first meiosis).

(5)

Spermiogenesis is seen.

(6)

Metamorphosis is not seen.

(6)

Sperm contains tail for the mobility in reproductive tract.

(7)

Egg does not contain any locomotory structure like tail.

(7)

//M2//QN23//SUB//DL0

Human female experience two major events during her life. Describe these two events. (1) Menarche (2) Menopause

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Menstruation begins between 10 – 15 years of age in women, it is called menarche.
A women's menstual cycle ends around the age of 50 called menopause.
(1) Onset of menstruation (Menarche):
The onset of menstruation indicates that the female reproductive system has matured and is ready to conceive.
The ovary has the capacity to produce mature ovum.
They are well developed lead to fertilisation of ovum with sperm.
(2) Cessation of menstruation (Menopause):
This process occurs around the age of 50.
The release of mature ovum is inhibited.
The level of sex hormone also decreases.
Even the uterus is not capable of fetal growth and development.

//M0//QN24//SUB//DL0//EQ

Name the functions of the following :

(a) Corpus luteum (b) Endometrium (c) Acrosome (d) Sperm tail (e) Fimbriae

//X

(a) Corpus luteum - It secretes progesterone. Progesterone is essential for the maintenance of the endometrium.
(b) Endometrium - Implantation of the fertilised ovum and many events of pregnancy take place in the endometrium.
(c) Acrosome - It is filled with enzymes that hydrolyze egg membrane, thus, helping the sperm in penetration of ovum during fertilisation of the ovum.
(d) Sperm tail -  It provides motility to sperm.
(e) Fimbriae - After ovulation, fimbriae helps in the collection of the ovum.

//M0//QN25//SUB//DL0

Identify True/False statements. Correct each false statement to make it true.

//X

False. Androgens are produced by Leydig's cells
(b) Spermatozoa get nutrition from sertoli cells.
Ans. True.
(c) Leydig cells are found in the ovary.
Ans. False. Leydig cells are found out side the seminiferous tubules of the testis (Intertitial space).
(d) Leydig cells synthesize androgens.
Ans. True.
(e) Oogenesis takes place in the corpus luteum.
Ans. False. Oogenesis takes place in the ovary.
(f) Menstrual cycle ceases during pregnancy.
Ans. True.
(g) Presence or absence of a hymen is not a reliable indicator of virginity or sexual experience.
Ans. True.

//M0//QN26//SUB//DL0//EQ

Write a brief note on menstrual cycle in detail. (Diagram is not required)

OR
Explain the cyclic reproductive events that only occurs in female of primates. (Diagram is not required)

//X

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.
The first menstruation begins at puberty and is called menarche.
The changes in the ovary and the uterus endometrium are induced by changes in the levels of pituitary secretion of gonadotropin hormones.
Menstrual cycle is well understood by taking a cycle of 28 days which can be divided into three main phases.
(i) Menstrual phase (1 - 5 days):
The cycle starts with this phase, when menstrual flow occurs and it lasts for 3-5 days.
The menstrual flow results due to breakdown of endometrial lining of the uterus and its blood vessels which forms liquid that comes out through vagina.
Menstruation only occurs if the released ovum is not fertilised.
Lack of menstruation may be indicative of pregnancy.
However, it may also be caused due to some other underlying causes like stress, poor health etc.
(ii) Follicular phase / Proliferative phase
(Day 6 - 14):
The menstrual phase is followed by the follicular phase.
During this phase, the primary follicles in the ovary grow to become a fully mature Graafian follicle and simultaneously the endometrium of uterus regenerates through proliferation.
These changes in the ovary and the uterus are induced by changes in the levels of pituitary and ovarian hormones.
The secretion of gonadotropins (LH and FSH) increases gradually during the follicular phase, and stimulates follicular development as well as secretion of estrogens by the growing follicles.
(iii) Ovulatory phase (Day 14):
Both LH and FSH attain a peak level in the middle of cycle (about 14th day).
Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge induces rupture of Graafian follicle and thereby the release of ovum (ovulation).
(iv) Luteal phase / Secretory phase (Day 15-28):
The ovulation (ovulatory phase) is followed by the luteal phase during which the remaining parts of the Graafian follicle transform into the corpus luteum.
The corpus luteum secretes a large amount of progesterone which is essential for maintenance of the endometrium. Such an endometrium is necessary for implantation of the fertilised ovum and other events of pregnancy.
During pregnancy all events of the menstrual cycle stop and there is no menstruation.

//M2//QN27//SN//DL0//EQ

Write a short note on fertilisation (Till the formation of zygote).

//X

The process of fusion of a sperm with an ovum is called fertilisation.
The fusion of sperm and ovum takes place at ampullary isthmus junction in oviduct.
During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane that block the entry of additional sperms. Thus, it ensures that only one sperm can fertilise an ovum.
The secretions of the acrosome help the sperm enter into the cytoplasm of the ovum through the zona pellucida and the plasma membrane. This induces the completion of the meiotic division of the secondary oocyte.
The second meiotic division is also unequal and results in the formation of a second polar body and a haploid ovum (ootid).
Soon the haploid nucleus of the sperms and that of the ovum fuse together to form a diploid zygote.

//M3//QN28//SUB//DL0//EQ

Explain - the sex of the baby is determined by the father and not by the mother.

OR
In our society the women are often blamed for giving birth to daughters. Can you explain why this is not correct?

//X

The sex of the baby has been decided after completion of fertilisation.
The chromosome pattern in the human female is XX and in the male is XY.
All the haploid gametes (ova) produced by the female have the sex chromosome X whereas, in the male gametes (sperms) the sex chromosome could be either X or Y, hence, 50 per cent of sperms carry the X chromosome while the other 50 per cent carry the Y.
After fusion of the male and female gametes the zygote would carry either XX or XY depending on whether the sperm carrying X or Y fertilised the ovum.
The zygote carrying XX would develop into a female baby and XY would form a male.
That is why, scientifically it is correct to say that the sex of the baby is determined by the father and not by the mother.

//M2//QN29//SUB//DL0

What is placenta? Give its importance.

//X

Placenta is a structural and functional unit between developing embryo (foetus) and maternal body.
(1) The chorionic villi and uterine tissue become interdigitated with each other and jointly form placenta.
(2) The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo.
Importance: The placenta facilitate the supply of oxygen and nutrients to the embryo and also removal of carbon dioxide and excretory/waste materials produced by the embryo.
Placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progesterone, etc.

//M4//QN30//SUB//DL0//EQ

Explain implantation and embryonic development.

//X

After implantation, (attachment of developing embryo to the uterine wall) finger-like projections appear on the trophoblast called chorionic villi which are surrounded by the uterine tissue and maternal blood.
The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo.
The placenta facilitate the supply of oxygen and nutrients to the embryo and also removal of carbon dioxide and excretory/waste materials produced by the embryo.
Placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progesterone, etc.
In the later phase of pregnancy, a hormone called relaxin is also secreted by the ovary.
hCG, hPL and relaxin are produced in women only during pregnancy.
During pregnancy, the levels of other hormones like estrogens, progesterone, cortisol, prolactin, thyroxine, etc., are increased several-folds in the maternal blood.
Increased production of these hormones is essential for supporting the fetal growth, metabolic changes in the mother and maintenance of pregnancy.
Embryonic development :
Immediately after implantation, the inner cell mass (embryo) differentiates into an outer layer called ectoderm and an inner layer called endoderm.
A mesoderm soon appears between the ectoderm and the endoderm.
These three layers give rise to all tissues (organs) in adults.
The inner cell mass contains certain cells called stem cells which have the potency to give rise to all the tissues and organs.
The human pregnancy lasts 9 months.
In human beings, after one month of pregnancy, the embryo’s heart is formed. The first sign of growing foetus may be noticed by listening to the heart sound carefully through the stethoscope.
By the end of the second month of pregnancy, the foetus develops limbs and digits.
By the end of 12 weeks (first trimester), most of the major organ systems are formed, for example, the limbs and external genital organs are well-developed.
The first movements of the foetus and appearance of hair on the head are usually observed during the fifth month.
By the end of about 24 weeks (end of second trimester), the body is covered with fine hair, eyelids separate, and eyelashes are formed.
By the end of nine months of pregnancy, the foetus is fully developed and is ready for delivery.

//M4//QN31//SUB//DL0//EQ

The zygote passes through several developmental stages till implantation, describe each stage briefly with suitable diagrams.

//X

The zygote is formed at the ampullary-isthmus junction of the fallopian tube when the union of secondary oocyte and spermatozoa occurs. The zygote undergoes various divisions and changes before it reaches the uterus for implantation.
The figure shows the various stages of development of a zygote as it passes through the oviduct and uterus: 
(a) The zygote divides into a two-celled stage via division or 1st cleavage while the zygote is still in the isthmus of the oviduct.
(b) Several more mitotic divisions or cleavages occur in the 2 celled stage to form a 2, 4, 8 and finally a 16-celled stage of the zygote. The 16 celled stage is called the morula and various cells formed after cleavage are called blastomeres.
(c) Morula then changes into a blastocyst after a few more divisions and this stage contains a fluid filled cavity in the embryo. The blastomeres become arranged and line up into an outer layer of cells called the trophoblast and an inner mass of cells. The fluid filled cavity is called blastocoel.
(d) Implantation of the embryo occurs at this blastocyst stage by the help of trophoblast layer which embeds itself into the uterine endometrium.

//M0//QN32//SUB//DL0//EQ

What is parturition? Which hormones are involved in induction of parturition?

OR
Explain parturition and lactation.

//X

Parturition is the process of giving birth to a baby as the development of the foetus gets completed in the mother’s womb.
The hormones involved in this process are oxytocin and relaxin.
Oxytocin leads to the contraction of smooth muscles of myometrium of the uterus, which directs the full term foetus towards the birth canal.
Effects of hormones :
(1) Oxytocin : Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex.
This triggers release of oxytocin from the maternal pituitary. Oxytocin acts on the uterine muscle and causes stronger uterine contractions, which in turn stimulates further secretion of oxytocin.
(2) Relaxin :
On the other hand, relaxin hormone causes relaxation of the pelvic ligaments and prepares the uterus for child birth.
The stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger and stronger contractions. This leads to expulsion of the baby out of the uterus through the birth canal – parturition.
Soon after the infant is delivered, the placenta is also expelled out of the uterus.

//M2//QN33//SUB//DL0

Why do doctors recommend breastfeeding during the initial period of infant growth?

//X

Lactation :
The mammary glands of the female undergo differentiation during pregnancy and start producing milk towards the end of pregnancy by the process called lactation. This helps the mother in feeding the newborn.
The milk produced during the initial few days of lactation is called colostrum which contains several antibodies absolutely essential to develop resistance for the new-born babies.
Colostrum contains many antibodies which has mainly IgA.
Breast-feeding during the initial period of infant growth is recommended by doctors for bringing up a healthy baby.

//M1//QN34//FB//DL0

Fill in the blanks:

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Sexually
(b) Humans are _________ (oviparous, viviparous, ovoviviparous)
Ans. Viviparous
(c) Fertilisation is _______ in humans (external/internal)
Ans. Internal
(d) Male and female gametes are _________ (diploid/haploid)
Ans. Haploid
(e) Zygote is _________ (diploid/haploid)
Ans. Diploid
(f) The process of release of ovum from a mature follicle is called _________ .
Ans. Ovulation
(g) Ovulation is induced by a hormone called _____ .
Ans. LH
(h) The fusion of male and female gametes is called _______ .
Ans. Fertilisation
(i) Fertilisation takes place in _________ .
Ans. Ampullary region of oviduct
(j) Zygote divides to form _________ which is implanted in uterus.
Ans. Blastocyst
(k) The structure which provides vascular connection between foetus and uterus is called _________ .
Ans. Placenta

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How many eggs are released by a human ovary in a month? How many eggs do you think would have been released if the mother gave birth to identical twins? Would your answer change if the twins born were fraternal?

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One ovum is released by a human ovary in a month. Identical twins are developed from a single egg. Hence, only one egg would have been released when the mother gave birth to identical twins. If the twins are fraternal then they must have been developed from two eggs.

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What are the major functions of male accessory ducts and glands?

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(1) Male accessory ducts include vasa efferentia, epididymis. vas deferens and rete testis. They transport and temporarily store spermatozoa.
(2) Male accessory glands include seminal vesicles, bulbourethral gland, and prostate gland. These glands secrete fluids that lubricate the female reproductive system and sperms.

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Write two major functions each of testis and ovary.

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Testis :
(i) Produce sperms by process of spermatogenesis.
(ii) Produce male sex-hormone testosterone.
Ovary :
(i) Produce ovum by oogenesis.
(ii) Produce female sex-hormone such as estrogen and progesterone.

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How many eggs do you think were released by the ovary of a female dog which gave birth to 6 puppies?

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Dogs are species which has poly ovulatory where one ovary releases more than one ovum at the time of ovulation.
Therefore six eggs were released by the ovary of a female dog which gave birth to the six puppies.