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.