Human Reproduction Class 12 Notes Biology Chapter 3 - CBSE

Chapter:3

What are Human Reproduction?

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    The Male Reproductive System

    It consists of the primary sex organs (a pair of testes):

    • Scrotum – a pouch in which testes are situated
    • Testicular lobules
    • Seminiferous tubules – contains Spermatogonia and Sertoli cells- contains Leydig cells

    Accessory Ducts

    • ➥ Rete testis
    • ➥ Vasa efferentia
    • ➥ Epididymis
    • ➥ Vas deferens
    • ➥ Urethra

    Accessory Glands

    • ➥ A pair of seminal vesicles
    • ➥ Prostate gland
    • ➥ Bulbourethral gland

    These glands secrete seminal plasma rich in fructose, calcium and certain enzymes. Secretions of bulbourethral glands also help in lubrication of penis.

    External Genitalia

    • The penis is the external genitalia in human males.
    • It is made up of special erectile tissue that helps in erection of the penis to facilitate insemination.
    • The enlarged tip of the penis is called glans penis covered by foreskin.

    The Female Reproductive System

    It consists of the primary sex organ that is a pair of ovaries.

    • Secondary sex organs- the duct system consisting of a pair of fallopian tube , a uterus , cervix and vagina
    • External genitalia
    • Mammary glands

    Ovaries

    • ➥ Produce female gametes called ova.
    • ➥ Covered by a thin epithelium, enclosing the ovarian stroma.
    • ➥ Stroma is divided into 2 regions i.e. Cortex (outer) and Medulla (inner).

    Gametogenesis

    The process of formation of gametes is called gametogenesis. It is of two types:

    Spermatogenesis in males Oogenesis in females
    The process of formation of sperms in males is called spermatogenesis The process of formation of a mature female gamete is called oogenesis

    Structure of sperm composed of head, neck, middle piece and a tail.

    Menstrual Cycle

    The cyclic changes that occur in the reproductive organs of primate females is called menstrual cycle

    The events in a menstrual cycle can be studied under four phases:

    • Menstrual Phase
    • Follicular Phase
    • Ovulatory Phase
    • Luteal Phase

    Fertilization

    The process of fusion of a sperm with an ovum is called fertilization.

    Implantation

    • Zygote moves towards uterus → Blastomeres (2, 4, 8,16 daughter cells) → morula (8-16 blastomeres) → Blastocyst
    • Blastocyst gets embedded in ndometrium of uterus.

    Pregnancy And Embryonic Development

    • Placenta secretes hormones like hCG, hPL, estrogens, progesterones (to maintain pregnancy).
    • Inner cell mass differentiates into an outer layer called ectoderm, middle mesoderm and an inner layer endoderm.

    Parturition

    • Gestation period – 9 months.
    • Parturition – the process of delivery of the foetus (childbirth).

    Lactation

    • Production of milk towards the end of pregnancy is called lactation.
    • The milk produced during the initial few days is called colostrum that is rich in IgG antibody.