Class 8, Science, Chapter-6, Lecture-2, Sexual Reproduction (Notes)
MALE REPRODUCTIVE SYSTEM:
- Testes: – (i) Produces sperm
(ii) Secrets male hormone (Testosterone) - Scrotum: – Protects testes
- Vas deferens: – carries sperm from testes to urethra
- Urethra: – ejaculates sperm or urine
- Penis: – carries sperms into the vagina
FEMALE REPRODUCTIVE SYSTEM:
- Ovary: – (i) Produces ovum
(ii) Secrets female hormones (Oestrogen and Progesterone) - Fallopian tube: – carries fertilisation
- Uterus: – carries foetus
- Cervix: – receives sperm
- Vagina: – receives penis
In unisexual animals:
GONADS (the primary sex organs) produce gametes.
TESTES (Male gonads) produces sperm.
OVARY (Female gonads) produces ovum.
FERTILISATION IN HUMAN BEINGS:
- During copulation, sperms are introduced inside the vagina.
- The sperms move through cervix and uterus and reach oviduct.
- If an ovum is present in the oviduct, it fuses with one sperm and forms zygote.
DEVELOPMENT OF EMBRYO:
- In the fallopian tube, the zygote undergoes cell division to form embryo.
- Implantation: The embryo moves down and reaches the uterus and gets attached to its inner wall.
- A special tissue called placenta develops between uterine wall and the embryo.
- Gestation: The foetus develops inside uterus to a child.
- Parturition: A fully developed child moves out of uterus through vaginal opening.
OVULATION:
The release of ovum from the ovary into the oviduct is termed as ovulation.
MENSTRUATION:
The breakdown and removal of the inner, thick and soft lining of the uterus along with its blood vessels in the form of vaginal bleeding is called menstrual flow or menstruation.
MENSTRUAL CYCLE:
The cycle of events taking place in the ovaries and uterus every twenty eight days and marked by the menstrual flow, is called menstrual cycle.
MENARCHE:
The beginning of menstruation at puberty in a female human being is termed menarche.
MENOPAUSE:
The stoppage of menstrual flow around the age of 50 years in a female human being is termed as menopause.
COPULATION:
The process of introducing male gamete inside the female genital tract is called copulation.
IMPLANTATION:
The embedding of embryo in the thick lining of the uterus is called implantation.
PLACENTA:
A special tissue that develops between the uterus wall and the embryo through which exchange of nutrients, oxygen and wastes between the embryo and the mother takes place is called the placenta.
GESTATION:
The development of foetus inside the uterus till birth is called gestation.
PARTURITION:
The birth of the fully developed foetus through the vaginal opening is termed as parturition.
METHODS OF PREVENTING PREGNANCY:
- Barrier methods
Physical devices such as condom, diaphragm and cervical caps prevent the entry of sperm in the female genital tract during copulation. - Chemical methods
Oral pills inhibit the production of gametes by the action on hypothalamus, pituitary and the ovaries.
Vaginal pills kill the sperms that enter the vagina. - Surgical methods
Vasectomy in males:– a small portion of vas deferens is surgically removed or tied.
Tubectomy in females:– a small portion of fallopian tube is surgically removed or tied. - Use of IUCDs (Intrauterine Contraceptive Devices) such as copper – T prevent implantation in the uterus.
SEXUALLY TRANSMITTED DISEASES:
An infectious disease which is spread from an infected person to a healthy person by sexual contact is called sexually transmitted disease (STD).
Examples– Bacterial Infections - Gonorrhoea, Syphilis
Viral Infections - Warts, AIDS
SYMPTOM OF SEXUALLY TRANSMITTED DISEASES:
Burning sensation at urination and urethral discharge
Prevention from STD: Use of condom during sex.
When the egg is not fertilised:
In human females, ovary release on egg every month. The uterus prepares itself by making the inner lining thick and spongy for the nourishment of the fertilised egg.
If egg is not fertilized, it leaves for about one day after which the lining breaks and moves out through vagina as blood and mucous.