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SubjectsBiology
आरोपण, गर्भावस्था और अपरा निर्माण
In this Class 12 Biology topic from Chapter 2: Human Reproduction, students learn how the blastocyst attaches to the uterine lining during implantation and how pregnancy begins and progresses. The topic explains the formation of the placenta from maternal and embryonic tissues, its role in exchanging oxygen, nutrients, and wastes, and its function as an endocrine organ. It also connects placental hormones with the maintenance of pregnancy and fetal development.
TOPIC PRACTICE
Up to 6 questions from this page. Select your focus, then start.
The endometrium is the innermost, glandular lining of the uterus. During the menstrual cycle, it thickens under hormonal influence and becomes receptive to implantation. If pregnancy does not occur, its functional layer is shed during menstruation. The myometrium is the muscular middle layer, the perimetrium is the outer covering, and the epidermis belongs to skin; therefore B is correct.
The embedding of a blastocyst into the endometrium is called implantation. After cleavage, the embryo forms a blastocyst, which attaches to and penetrates the uterine lining so that pregnancy can become established. Ovulation is the release of a secondary oocyte from the ovary, fertilization is the fusion of sperm and oocyte, and parturition means childbirth. Therefore, option A is correct.
The foetus is connected to the placenta by the umbilical cord. It contains fetal blood vessels that carry blood to and from the placenta, allowing exchange of oxygen, nutrients, carbon dioxide, and metabolic wastes across the placental interface. The fallopian tube transports the oocyte, the vas deferens carries sperm, and the cervix is the lower part of the uterus. Hence, option A is correct.
The placenta secretes human chorionic gonadotropin, or hCG, especially during early pregnancy. hCG maintains the corpus luteum, which continues producing progesterone; progesterone helps maintain the endometrium and supports the developing embryo. Insulin comes mainly from pancreatic beta cells, thyroxine from the thyroid gland, and melatonin from the pineal gland. Therefore, option A is correct.
The gestation period is the interval during which the developing embryo and foetus are carried in the uterus. In this question it is represented as the period from fertilisation to birth, although clinical dating commonly counts about 40 weeks from the first day of the last menstrual period. Menstrual bleeding, sperm formation, and ovulation are separate events. Thus, option A is correct.
Human pregnancy is conventionally described as about nine calendar months. Clinically, its average duration is approximately 40 weeks or 280 days when counted from the first day of the last menstrual period. If counted from fertilisation, it is closer to 38 weeks because fertilisation occurs roughly two weeks after that dating point. Therefore, option C is correct.
QUIZ COMPLETE
