Human Reproduction and Genetics notes:

1. Male Reproductive System:

• Structure and functions:

• Testes: primary male sex organs, responsible for spermatogenesis and testosterone production.

• Epididymis: coiled tubes where sperm mature and gain the ability to fertilize.

• Vas deferens: transport sperm from the epididymis to the ejaculatory duct.

• Seminal vesicles, prostate gland, and bulbourethral glands: secrete fluids that mix with sperm to form semen.

• Penis: organ of copulation; delivers semen into the female reproductive tract.

• Spermatogenesis:

• Process of sperm formation in the seminiferous tubules of the testes.

• Involves meiotic cell division, resulting in the formation of haploid sperm cells.

• Regulated by hormones such as FSH (follicle-stimulating hormone) and LH (luteinizing hormone).

• Structure and Functions of Sperm:

• Consists of a head, containing the genetic material, a midpiece with mitochondria for energy production, and a tail for motility.

[Reference: NCERT Biology Class 11, Chapter 3 - “Human Reproduction”]

2. Female Reproductive System:

• Structure and Functions:

• Ovaries: primary female sex organs, responsible for producing eggs (ova) and female hormones (estrogen and progesterone).

• Uterine (Fallopian) tubes: transport ova from the ovaries to the uterus.

• Uterus: muscular organ where the fertilized egg implants and develops into a fetus during pregnancy.

• Cervix: the opening of the uterus that connects to the vagina.

• Vagina: muscular tube leading from the uterus to the external opening.

• Oogenesis:

• Process of egg formation in the ovaries.

• Involves meiotic cell division, resulting in the formation of haploid ova.

• Unlike spermatogenesis, only one functional ovum is produced each month.

• Regulated by hormones such as FSH and LH.

• Structure and Functions of Ovum:

• Larger than sperm, contains abundant cytoplasm and nutrients for early embryonic development.

• Enclosed within a protective zona pellucida, which prevents polyspermy.

[Reference: NCERT Biology Class 11, Chapter 3 - “Human Reproduction”]

3. Menstrual Cycle:

• Different Phases:

• Menstrual phase: Shedding of the uterine lining (menstruation).

• Follicular phase: Development and maturation of the ovarian follicle, culminating in ovulation.

• Ovulatory phase: Rupturing of the mature follicle, releasing the ovum into the fallopian tube.

• Luteal phase: Formation and functioning of the corpus luteum, which secretes progesterone. If fertilization doesn’t occur, the corpus luteum degenerates, leading to a decline in hormone levels and the onset of the next menstrual cycle.

• Hormonal Regulation:

• Primarily controlled by FSH, LH, estrogen, and progesterone.

• Estrogen and progesterone play crucial roles in preparing the uterus for implantation and maintaining pregnancy.

[Reference: NCERT Biology Class 11, Chapter 3 - “Human Reproduction”]

4. Fertilization:

• Process involving the union of a sperm and an ovum, resulting in the formation of a zygote.
• Occurs in the fallopian tube.
• Steps of Fertilization:
• Acrosomal reaction: Enzymes from the sperm’s acrosome help it penetrate the zona pellucida.
• Sperm entry: A single sperm enters the ovum, leading to the completion of meiosis and fusion of genetic material.
• Zona pellucida reaction: The zona pellucida undergoes changes that prevent the entry of additional sperm (block to polyspermy).
• The fertilized zygote undergoes cell division as it travels toward the uterus.

[Reference: NCERT Biology Class 12, Chapter 3 - “Reproduction in Organisms”]

5. Pregnancy:

• Stages:

• Embryonic Development: First 8 weeks of development, during which major organ systems are formed.

• Fetal Development: From 9 weeks until birth, involving growth, maturation, and refinement of body structures.

• Placenta Formation and Functions:

• Specialized organ that develops during pregnancy.

• Facilitates exchange of oxygen, carbon dioxide, nutrients, waste products, and hormones between the maternal and fetal circulatory systems.

• Also produces hormones that support pregnancy, such as human chorionic gonadotropin (hCG) and progesterone.

• Hormonal Changes:

• Increased production of progesterone and estrogen, which help maintain the uterine lining and support fetal development.

• Human chorionic gonadotropin (hCG) maintains the corpus luteum and stimulates progesterone production.

[Reference: NCERT Biology Class 12, Chapter 3 - “Reproduction in Organisms”]

6. Parturition:

• Process of childbirth, leading to the delivery of the baby.

• Stages:

• Dilation of the cervix to allow the passage of the baby.

• Expulsion of the baby through uterine contractions.

• Delivery of the placenta.

• Hormonal Control:

• Estrogen and progesterone levels decrease, leading to uterine contractions.

• Oxytocin, a hormone produced by the pituitary gland, stimulates and coordinates uterine contractions.

[Reference: NCERT Biology Class 11, Chapter 3 - “Human Reproduction”]

7. Contraception:

• Methods used to prevent unwanted pregnancies.

• Different Methods:

• Barrier methods: Physical barriers, such as condoms and diaphragms, prevent the meeting of sperm and ovum.

• Hormonal methods: Birth control pills, injections, implants, and transdermal patches use synthetic hormones to prevent ovulation or alter cervical mucus to inhibit sperm entry.

• Intrauterine devices (IUDs): Small devices inserted into the uterus to prevent implantation.

• Sterilization: Surgical methods that permanently block the fallopian tubes (tubectomy) or vas deferens (vasectomy).

• Mechanism of Action:

• Barrier methods physically block the sperm from reaching the ovum.

• Hormonal methods prevent ovulation, alter the uterine lining to prevent implantation, or thicken cervical mucus to deter sperm penetration.

• IUDs release substances that create an environment in the uterus that is unfavorable for implantation.

• Sterilization physically cuts off the pathways for sperm or eggs.

[Reference: NCERT Biology Class 11, Chapter 3 - “Human Reproduction”]

8. Sexually Transmitted Infections (STIs):

• Infections spread primarily through sexual contact.

• Common STIs:

• HIV: Human Immunodeficiency Virus, which can lead to AIDS if untreated.

• Syphilis: Caused by the bacterium Treponema pallidum, characterized by stages of skin lesions and systemic involvement.

• Gonorrhea: Caused by the bacterium Neisseria gonorrhoeae, leading to inflammation of the genitourinary tract.

• Modes of Transmission:

• Primarily through unprotected sexual intercourse (vaginal, anal, or oral).

• Some STIs can also be transmitted through blood transfusions, sharing contaminated needles, or from mother to child during pregnancy or childbirth.

• Prevention:

• Abstinence from sexual activity or practicing safe sex with condoms.

• Regular testing, prompt treatment, and partner notification are crucial for STI prevention and control.

[Reference: NCERT Biology Class 12, Chapter 3 - “Reproduction in Organisms”]

9. Assisted Reproductive Techniques:

• Medical interventions used to aid couples with fertility issues.

• Techniques:

• In Vitro Fertilization (IVF): Ova and sperm are combined in a laboratory dish, and the resulting embryos are transferred to the female’s uterus.

• Intrauterine Insemination (IUI): Sperm are directly placed into the woman’s uterus around the time of ovulation to increase the chances of fertilization.

• Surrogacy: A woman (the surrogate) carries and gives birth to a baby for another couple who cannot conceive or carry a pregnancy.

• Advantages and Limitations:

• Assisted reproductive techniques have helped many couples achieve parenthood but can be costly, emotionally demanding, and have varying success rates.

[Reference: NCERT Biology Class 12, Chapter 3 - “Reproduction in Organisms”]

10. Developmental Biology:

• Study of the processes involved in the development of an organism from a fertilized egg.

• Basic Concepts:

• Germ Layer Formation: The embryo consists of three germ layers: ectoderm, mesoderm, and endoderm, which give rise to various tissues and organs.

• Organogenesis: Process by which tissues and organs develop from the germ layers.

• Fetal Growth: Involves overall growth and maturation of the developing organism.

• Congenital Anomalies:

• Birth defects that occur during embryonic or fetal development.

• Can be caused by genetic factors, environmental factors (teratogens), or a combination of both.

[Reference: NCERT Biology Class 12, Chapter 5 - “Principles of Inheritance and Variation”]

11. Genetics:

• Study of genes, heredity, and variation in organisms.

• Role of Genes in Sex Determination:

• In humans, sex is determined by a pair of sex chromosomes (X and Y).

• Females have two X chromosomes (XX), while males have one X