Reproduction in Human Beings | Biology for Grade 10 PDF Download

➢  Pubertal Changes (Secondary Sexual Characters) in Male:

• Widening of shoulders.
• Deepening of voice.
• Growth of hairs under chest, armpits and around the pubic area.
• The appearance of beard and moustaches.
• Growth of sex organs, [Testes & Penis].
• Increased activity of sweat and sebaceous glands.
• Oily skin and appearance of pimples.
• Darkening in skin colour of the genital area.

➢  Pubertal Changes (Secondary Sexual Characters) in Female:

• Widening of pelvis and hips.
• High pitch voice.
• Growth of hairs under armpits and around the pubic area.
• Initiation of the menstrual cycle.
• Growth of mammary glands (breasts).
• Darkening in skin colour of the genital area.
• Maturation of secondary sex organs like fallopian tubes, uterus.

The male reproductive system consists of portions that produce the germ cells and other portions that deliver the germ cells to the site of fertilization.

• The formation of germ cells or sperms takes place in the testis. These are located outside the abdominal cavity in the scrotum because sperm formation requires a lower temperature [13°C] than the normal body temperature.
  
• Testes secrete a male sex hormone called testosterone. In addition to regulating the formation of sperms, testosterone brings about changes in appearance seen in boys at the time of puberty. These changes are called secondary sexual characters.
• The sperms formed are delivered through the vas deferens which unites with a tube coming from the urinary bladder. The urethra thus forms a common passage for both the sperms and urine. Hence urethra is also known as a urinogenital tract.
• Along the path of the vas deferens, glands like the prostate gland and the seminal vesicle add their secretions so that the sperms are now in a fluid that makes their transport easier and this fluid also provides nutrition.
  Structure of Sperm
• The sperms are tiny bodies consisting of mainly genetic material and a long tail that helps them move towards the female germ cell (ovum).
  
  Question for Reproduction in Human Beings

  Try yourself:In human males, the testes lie in the scrotum, because it helps in the:

  • A.

    process of mating
  • B.

    formation of sperm
  • C.

    easy transfer of gametes
  • D.

    secretion of estrogen

  Explanation

  In human males, testes descend into a muscular bag called the scrotum, which lies outside the body cavity, before birth and remains there for rest of the life because sperm production occurs at a temperature lower than the body temperature. Thus, the correct answer is option B.

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The male reproductive system consists of :

• Testicles (testes): A pair of oval-shaped organs masked in a pouch called the scrotum. They are responsible for the production of sperms and the male hormone testosterone.
• Scrotum: It is a sac-like organ that hangs below the penis and behind it. It is the houses of the testicles, or testes, and maintains a temperature that is required for the production of sperm by it.
• Vas deferens: The sperms produced in testes are stored in a tube called the epididymis. Here the sperms get matured and pass to the urethra through the muscular tube called vas deferens.
• Accessory glands: This includes three glands, namely seminal vesicles, prostate gland, and Cowper’s gland. The secretions from the three glands mix to form a fluid called semen. Semen nourishes the sperm, increases the volume and helps in lubrication.
• Penis: The penis is a cylindrical tube that serves as both a reproductive organ and an excretory organ. It delivers sperms into the vagina during sexual intercourse.

Female Reproductive System

• The female germ cells or eggs are made in the ovaries. They are also responsible for the production of female sex hormones, i.e., Oestrogen and Progesterone.
• When a girl child is born, the ovaries already contain thousands of immature eggs. On reaching puberty, some of these start maturing. One egg is produced every month by one of the ovaries.
• The egg is carried from the ovary to the womb through a thin oviduct or fallopian tube.

Female Reproductive System

• The two oviducts unite into an elastic bag-like structure known as the uterus.
• The uterus opens into the vagina through the cervix.
• The sperms enter through the vaginal passage during sexual intercourse. They travel upwards and reach the oviduct where they may encounter the egg.
• The fertilized egg (zygote) gets implanted in the lining of the uterus.

The female reproductive system consists of :

• A pair of ovaries: Ovaries produce and store ovum in them. They also produce a female hormone called estrogen.
• Fallopian tubes (Oviducts): They are the site of fertilization. They connect the ovaries with the uterus.
• Uterus: Uterus is the site of development for the embryo.
• Vagina: It is the part that connects the cervix to the external female body parts. It is the route for the penis during coitus as well as a fetus during delivery.

The mother's body is designed to undertake the development of the child:

• The uterus prepares itself every month to receive and nurture the blood to nourish the growing embryo. The lining thickens and is richly supplied with blood to nourish the growing embryo.
• The embryo gets nutrition from the mother's blood with the help of a special tissue called the placenta. This is a disc that is embedded in the uterine wall. It contains villi.
• On the mother's side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo.
• The developing embryo will also generate waste substances that can be removed by transferring them into the mother's blood through the placenta.
• The development of the child inside the mother's body takes approximately nine months. The child is born due to rhythmic contractions of the muscles in the uterus, called labour pain.
  
  Question for Reproduction in Human Beings

  Try yourself:Which of the following statements are incorrect?

  • A.

    The umbilical cord is the conduit between the foetus and the placenta.
  • B.

    The placenta can exchange materials between the foetus and the mother.
  • C.

    Antibodies cannot reach the foetus through the mother’s placenta.
  • D.

    All of the above.
  • E.

    None of the above

  Explanation

  Antibodies from the mother's body are transported to the foetus through the mother placenta as that is the main connection between them. So, option C is the answer.

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• Menopause: The permanent stoppage of menstruation at about the age of 45 years is termed menopause.
• The menstrual cycle is also called the ovarian cycle.
• In the human female, ovulation starts only after puberty and occurs once a month and midway through the menstrual cycle.
• The menstrual cycle is absent before puberty and temporarily stopped during pregnancy.
• The menstrual cycle occurs only in the primates among mammals.
• Parthenogenesis: A primitive type of sexual reproduction in which unfertilized eggs develop to form haploid adult organisms. It is found in female aphids, drones (males) of honey bees and termites, and certain lizards.
• In freshwater sponges (Spongilla), internal buds are formed within the parent body. Such buds are called gemmules. The gemmules, on the arrival of favourable conditions, develop into a sponge colony.
• After fertilization, the membrane appears around the egg to prevent further entry of sperms. It is called monospermy. After the entry of sperm, the ovum completes its maturation division.
• Amniocentesis: Amniocentesis is a prenatal diagnostic technique to determine the genetic disorders, if any, of the foetus. Unfortunately, the useful technique of amniocentesis is being misused to kill the normal female foetuses as it can help to detect the sex of the foetus also. The determination of sex by amniocentesis has been banned.

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