याद रखने योग्य अवधारणाएँ और फॉर्मूला

Viviparous Animals

  • Give birth to live young.
  • Embryo develops inside mother’s body, nourished by the placenta.
  • Common in mammals, including humans.
  • Some fish, reptiles, and invertebrates also viviparous.

Oviparous Animals

  • Reproduce by laying eggs.
  • Eggs develop and hatch outside the mother’s body.
  • Common in birds, reptiles, amphibians, most fish, and insects.
  • Eggs vary in structure: hard-shelled in birds, leathery in reptiles, jelly-like in fish.

Insemination

  • Deposit of sperm into female reproductive tract.
  • Natural Insemination: Occurs during sexual intercourse in humans and mating in animals.
  • Artificial Insemination (AI): Sperm placed in female tract artificially, used in human fertility treatments and animal breeding.

Fertilization

  • Fusion of sperm and egg to form zygote.
  • Occurs in fallopian tubes (usually).
  • Sperm penetrates egg’s outer layers, leading to zygote formation.
  • Zygote undergoes cell division, moves to uterus for implantation.

Uterus

  • Pear-shaped organ in female pelvis.
  • Comprises endometrium, myometrium, perimetrium.
  • Site for menstrual cycle, implantation, and fetal development.
  • Undergoes changes in response to estrogen and progesterone.
  • Cervical canal + vagina = Birth canal

Implantation

  • Blastocyst (developing embryo) attaches to endometrium.
  • Occurs about a week after fertilization.
  • Trophoblast cells form early placenta, establish nutrient/waste exchange.
  • hCG hormone secreted post-implantation maintains pregnancy.
  • The endometrium is indeed necessary for the implantation of the blastocyst, which is the early stage of embryo development.
  • In the absence of fertilization, the corpus luteum, which forms from the ovarian follicle after ovulation, degenerates. This leads to a decrease in the levels of progesterone, which is essential to maintain the endometrial lining. Without sufficient progesterone, the endometrial lining undergoes disintegration and is shed during menstruation.

Gestation

  • Lasts about 40 weeks, divided into three trimesters.
  • First Trimester: Major organ development.
  • Second Trimester: Rapid fetal growth, movement felt.
  • Third Trimester: Final development, preparation for birth.

Reproductive System

  • Male: Testes (sperm and testosterone production), sperm transportation structures, external genitalia.
  • Female: Ovaries (egg and hormone production), fallopian tubes, uterus, cervix, vagina.
  • Hormonally regulated.
  • Menopause- The time that marks the end of your menstrual cycles
  • Menarche- First menstrual cycle begins at puberty
  • Cyclic menstruation extends between menarche and menopause
  • In non-primate mammals cyclical changes during reproduction are called oestrus cycle

Seminiferous Tubules

  • Located in testes.
  • Site of spermatogenesis (sperm production).
  • Sertoli cells support sperm development; Leydig cells produce testosterone.
  • Hormonally regulated by FSH and LH.
  • Vas deferens receives a duct from seminal vesicle and opens into urethra as the ejaculatory duct.