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Halving of chromosomal number takes place during gametogenesis and regaining the 2n number occur as a result of fertilisation

Halving of chromosomal number takes place during gametogenesis by meosis and regaining the 2n number occur as a result of fertilisation by fusion of male and female gametes.

Vasa efferentia, Vas deferens.

● Rapid release of luteinising hormone ruptures Graafian follicle and release ovum (ovulation). 

● Corpus luteum secretes large amount of progesterone hormone that is essential for maintenance of the endometrium required for implantation of blastocyst leading to pregnancy. 

● Placenta produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (h PL). Relax in is also produced during later phase of pregnancy. Level of other hormones like estrogens, progestogens, cortisol, prolactin and thyroxine also increases which is essential for supporting fetal growth, metabolic changes in mother and maintenance of pregnancy. 

● Parturition signals originate from the fully developed foetus and the placenta induce mild uterine contractions which triggers release of oxytocin from pituitary. Oxytocin acts on the uterine muscle causing stronger uterine contractions.

Umbilical cord connects placenta with the foetus. It helps in the transport of nutrients, respiratory gases and metabolic wastes to and from mother and foetus.

Umbilical cord transports nutrients and respiratory gases and metabolic wastes to and from mother and foetus.

The figure is of blastula/blastocyst. 

A—Trophoblast.

Ovulation rupture of Graafian follicle and the subsequent release of the egg from the ovary.

The female reproductive system perform the following functions: 

(i) It forms the female gamete, i.e., the egg. 

(ii) It receives the male gamete, i.e., sperm, for fertilisation. 

(iii) It provides the site for fertilisation. 

(iv) It provides suitable conditions for the development of foetus. 

(v) It produces hormones that control the stages of ovulation and maintain pregnancy.

The organs which together form the female reproductive system are ovaries, fallopian tubes, uterus, cervix, vagina, mammary gland and vulva.

Name of cells- Sertoli cells.

Location-They are found lining-up the inner surface of seminiferous tubules.

The human testes are Present Scrotum.

For spermatogenesis,it is essential to maintain temperature 2-2.5°C lower than, internal body temperature. So, the human testes are located outside the abdominal cavity.

(d) None of the above

Oogenesis is the process of development of the female gamete or ovum or egg in the ovaries. During foetal development, certain cells in the germinal epithelium of the foetal ovary divide by mitosis and produce millions of egg mother cells or oogonia. No more oogonia are formed or added after biThe oogonial cells start dividing and enter into Prophase-I of meiotic division-I to form the primary oocytes which are temporarily arrested at this stage. The primary oocytes then get surrounded by a single layer of granulosa cells to form the primordial or primary follicles. A large number of follicles degenerate during the period from birth to puberty, so at puberty only 60,000 to 80,000 follicles are left in each ovary.rth.

The primary follicle gets surrounded by many layers of granulosa cells and a new theca layer to form the secondary follicle. A fluid filled Oogenesis space, the antrum develops in the follicle and gets transformed into a tertiary follicle. The theca layer gets organized into an inner theca interna and an outer theca externa. At this time, the primary oocyte within the tertiary follicle grows in size and completes its first meiotic division and forms the secondary oocyte.

It is an unequal division resulting in the formation of a large haploid secondary oocyte and a first polar body. The first polar body disintegrates. During fertilization, the secondary oocyte undergoes second meiotic division and produces a large cell, the ovum and a second polar body. The second polar body also degenerates. The tertiary follicle eventually becomes a mature follicle or Graafian follicle. If fertilisation does not take place, second meiotic division is never completed and the egg disintegrates. At the end of gametogenesis in females, each primary oocyte gives rise to only one haploid ovum.

1. Ovaries are the primary female sex organ producing eggs (ovum).

2. They are located one on each side of lower abdomen (pelvis). 

3. The ovary is attached in pelvic wall uterus by an ovarian ligament called mesovarium. 

4. It is an elliptical structure of 2-4 cm long 

5. Each ovary is covered by thin cuboidal germinal epithelium encloses ovarian stroma. 

6. Below germinal epithelium is a dense connective tissue called tunica albuginea. 

7. The stroma is differentiated into outer cortex and inner medulla. 

8. The cortex is dense and granular due to follicular cells at varying development stages. 

9. The medulla is a loose connective tissue with blood vessels, lymph vessels and nerve.

(A) 

(i) Corpus luteum—d 

(ii) Secondary oocyte—c 

(iii) Antrum—b 

(iv) Primary follicle—e 

(v) Blood vessels—a

(B) Changes in the primary oocyte: 

● Each primary oocyte gets surrounded by a single layer of granulosa cells and is known as primary follicle. 

● Primary follicle get surrounded by more layers of granulosa cells and a new theca and form secondary follicle. 

● A secondary follicle transforms into tertiary follicle characterised by a fluid-filled space, the antrum. 

● Primary oocyte undergoes first meiotic division and produces two unequal haploid cells—a large haploid secondary oocyte and a tiny first polar body. 

● The tertiary follicle further changes into the mature Graafian follicle. 

● The secondary oocyte forms a new membrane called zona pellucida around it.

Male reproductive system

• Seminiferous tubule
• Vas deferens
• Epididymis

Female reproductive system

• Vagina
• Cervix
• Uterus

Colostrum, a nutrient rich fluid produced by the human female immediately after giving birth, is loaded with immune, growth and tissue repair factors.

It acts as a natural antimicrobial agent to actively stimulate the maturation of the infant’s immune system.

 Milk produced during initial days of lactation, antibodies to give resistance.

Single egg was released in case of identical twins.

Haploid nucleus, acrosome.

 Ovarian follicles.

 Leydig cells the cells which secrete androgens.

The secretions of the bulbourethral glands help in the lubrication of the penis.

Production and maturation of gametes will take place after puberty (Secondary sexual maturity)

(a) 200 million

1. amnion 

2. Chorion 

3. allantois 

4. Yolk nac

Menstrual cycle: The menstrual or ovarian cycle occurs approximately once in every 28/29 days during the reproductive life of the female from menarche (puberty) to menopause except during pregnancy. The cycle of events starting from one menstrual period till the next one is called the menstrual cycle during which cyclic changes occurs in the endometrium every month. Cyclic menstruation is an indicator of normal reproductive phase.

Menstrual cycle comprises of the following phases:

1. Menstrual phase 

2. Follicular or proliferative phase 

3. Ovulatory phase 

4. Luteal or secretory phase

1. Menstrual phase: The cycle starts with the menstrual phase when menstrual flow occurs and lasts for 3-5 days. Menstrual flow is due to the breakdown of endometrial lining of the uterus, and its blood vessels due to decline in the level of progesterone and oestrogen. Menstruation occurs only if the released ovum is not fertilized. Absence of menstruation may be an indicator of pregnancy. However it could also be due to stress, hormonal disorder and anaemia.

2. Follicular or proliferative phase: The follicular phase extends from the 5th day of the cycle until the time of ovulation. During this phase, the primary follicle in the ovary grows to become a fully mature Graafian follicle and simultaneously, the endometrium regenerates through proliferation. These changes in the ovary and the uterus are induced by the secretion of gonadotropins like FSH and LH, which increase gradually during the follicular phase. It stimulates follicular development and secretion of oestrogen by the follicle cells.

3. Ovulatory phase: Both LH and FSH attain peak level in the middle of the cycle (about the 14th day). Maximum secretion of LH during the mid cycle called LH surge induces the rupture of the Graafian follicle and the release of the ovum (secondary oocyte) from the ovary wall into the peritoneal cavity. This process is called as ovulation.

4. Luteal or secretory phase: During luteal phase, the remaining part of the Graafian follicle is transformed into a transitory endocrine gland called corpus luteum. The corpus luteum secretes large amount of progesterone which is essential for the maintenance of the endometrium. If fertilization takes place, it paves way for the implantation of the fertilized ovum.

The uterine wall secretes nutritious fluid in the uterus for the foetus. So, this phase is also called as secretory phase. During pregnancy all events of menstrual cycle stop and there is no menstruation. In the absence of fertilization, the corpus luteum degenerates completely and leaves a scar tissue called corpus albicans. It also initiates the disintegration of the endometrium leading to menstruation, marking the next cycle.

In the absence of fertilization, the corpus luteum degenerates completely and leaves a scar tissue called corpus albicans. It also initiates the disintegration of the endometrium leading to menstruation, marking the next cycle.

(a) It helps to supply oxygen and nutrients to the foetus.
(b) It helps in the removal of CO₂ and other waste product formed by the foetus.
(c) Acts as endocrine gland by secreting hormone like human placental lactogen, human chorionic gonadotropin, estrogen and progesteron which are necessary to maintain pregnancy.

The finger like projections of the trophoblast produced after implantation are called chronic villi. Chroionic villi and uterine tissue become interdigitated with each other and jointly form the placenta.

The hormones secreted by human placenta are;

• Human chorionic gonadotropin
• Progesterone
• Human placental lactogen
• Estrogen

(A)

(B) (i) During pregnancy 

(ii) During menstruation.

Progesterone.

Corpus luteum

(a) Secondary spermatocyte – 16 chromosome

(b) spermatids -16 chromosome

Mesoderm germ layer from which gonad develops.

The process of formation of male and female gamete in the gonads is called gametogenesis.

Hyaluronidase; Acrosome

Spermatogonia undergo the process of spermatogenesis while Sertoli cells help spermiation.

The process of formation of spermatids is called spermatogenesis. It occurs in spermatogonia of seminiferous tubules. The process of release of mature sperms is called spermiation.

Progesterone is known as the pregnancy hormone. It is called so because it prepares the uterus for implantation of the blastocyst to the uterine wall and helps in the formation of placenta. Corpus luteum and placenta are the two sources of this hormone.

Cells of seminiferous epithelium –provide nutrition to developing germ cells.

Colostrum ..