Human Reproduction Class 12 Notes Biology Chapter 3

By going through these CBSE Class 12 Biology Notes Chapter 3 Human Reproduction, students can recall all the concepts quickly.

Human Reproduction Notes Class 12 Biology Chapter 3

→ Human are sexually reproducing and viviparous. The reproductive events in humans indude formation of gametes (gametogenesis) i.e.; sperms in. males and ovum in females, transfer of sperms into the female genital tract (insemination) and fusion of male and female garnets (fertilization) leading to formation of zygote.

→ After the formation and development of blastocyst and its attachment to the uterine wall (implantation), embryonic development (gestation) and delivery of the baby (parturition).

→ The male reproductive system is located in the pelvis region. It includes a pain of testes alongwith accessory ducts, glands and the external genitalia.

→ 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. The female reproductive also has a pair of memory glands which are integrated structurally and functionally to support the processes of ovulation, fertilisation, pregnancy, birth and child care.

→ The primary sex organs: the testis in the males and the ovaries in the females produce gametes i.e.; sperms and ovum, respectively, by the process called gametogenesis.

→ In testis, the inmature male cells (spermatogonia) produce sperms by spermatogenesis that begins at puberty.

→ After the process of spermiogenesis, sperm heads become embedded in the Sertoli cells. There are finally released from the seminiferous tubules by the process called spermiation.

→ Sperm is composed of a head, neck, a middle piece and a tail. A plasma membrane envelops the whole body of sperm.

→ The process of formation of a mature female gamete is called oogenesis which is markedly different from spermatogenesis. Oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogania) are formed within each fetal ovary, no more oogania are formed and added after birth.

→ 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 28/29 days, and the cycle of events starting from one menstruation till the next one is called menstrual cycle.

→ Rapid secretion.of L,H leading to its maximum level during mid cycle called LH surge induces rupture of Graafian follicle and thereby the ,release of ovum (ovulation). The ovulation (ovulatory phase) is followed by the luteal phase during which the remaining parts of the Graafian foil ice transform as the corpus luteum.

→ The corpus luteum secretes large amounts of progesteron which js essential for maintenance of the endometrium. During pregnancy all events of the menstrual cycle stops and therefore there is no menstruation.

→ In human beings, menstrual cycles cedses around 50 years of age. This is temed as menopause. Cyclic mensuration is an indicator of normal reproductive life between menache to menopause.

→ Fertilization is the process of fusion of a sperm. During this process, 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. This ensures that only one sperm can.fertilise an ovum.

→ The mitotic division starts as the zygote moves through the isthmus of the. oviduct towards the uterus and forms 2, 4, 8, 16 daughter cells called blastomeres. The embryo with 8 to 16 blastomeres is called a morula.

→ The trophoblast layer than gets attached to the endometrium and the inner cell mass gets differentiated as the embryo. After attachment, the uterine cells divide and covers the blastocyst. As a result, the blastocyte becomes embedded in the endometrium of the uterus. This is implantation and it leads to pregnency.

→ The average duration of human pregnancy is about 9.5 months which is called the gestation period. Vigorous contraction of the uterus at the end of pregnancy causes expulsion/delivery of the fetus. The process of delivery of the fetus is called parturition.

→ The mammery glands of the female undergo differentiation during pregnancy and starts producing milk towards the end of pregnancy by the process called lactation. The milk produced during the initial few days of lactation is called colostrum

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