12th Zoology



The union of the egg and the sperm is called fertilization. It results in
the production of a single diploid cell called zygote.

At the time of ovulation, the ovum is fully matured and it enters the
infundibulum of the uterine tube and passes into the ampulla. Fertilization of
the ovum occurs in the ampulla of the uterine tube. One spermatozoan pierces
the egg membrane, zona pellucida and enters the ovum. Polygamy (entry of
more sperms) is avoided by the formation of fertilization membrane around
the ovum.

In vitro fertilization (Test tube babies)

The so called test tube babies are produced by the technique of in
vitro fertilization. (In vitro = outside the body, as against in vivo = within the body). This technique is being increasingly used in couples who are not
able to achieve fertilization in the normal way

Gonadotropins are administered to the woman to stimulate growth
of follicles in the ovary. Just before ovulation, the ovum is removed (using an
aspirator) and is placed in a suitable medium. Spermatozoa are added to the
medium. Fertilization and early development of the embryo takes place in
this medium.

The process is carefully monitored. When the embryo is at the
8-celled stage, it is put inside the uterine endometrium. Successful
implantation takes place in about 20 percent of such trials. The techniques
are complex and need a team of well trained experienced personnel with
high degree of skill.

The success rate is only about 20% and 2 or 3 attempts may be necessary. It is also very expensive. The first success with this technique was achieved by Steptoe and Edwards of UK in 1978. However successful ‘test tube babies’ have been produced in many countries including India.

Gamete Intra fallopian transfer (GIFT)

It is a newer method in which the fertilized ova are introduced into
the fallopian tube from where they naturally pass to the uterus for
implantation. This method is considered to have a higher success rate than
IVF. An even newer technique is the introduction of a single sperm into the
ovum by microinjection.

Related Topics in Zoology:

Bio Zoology All Important Topics

  1. Human Physiology Introduction

  2. Nutrition

  3. Carbohydrates Poly hydroxyaldehydes (or) ketones

  4. Proteins (Polypeptides)

  5. Lipids

  6. Vitamins – Functions Of Vitamins

  7. Deficiency of Vitamin

  8. Minerals – Water – Role of water

  9. Balanced diet

  10. Obesity

  11. Digestive System

  12. Dental Caries (Tooth decay)

  13. Root Canal Treatment

  14. Peptic ulcer

  15. Hernia and Types

  16. Appendicitis (Appendix)

  17. Gall Stones

  18. Hepatitis

  19. Fractures – Types of fractures

  20. Mechanism of fracture

  21. Dislocation of joints

  22. Arthiritis

  23. Rickets and Osteomalacia – Orthopedics

  24. Muscles

  25. Mechanism of muscle contraction

  26. Types of muscle contraction

  27. Myasthenia Gravis

  28. Respiration – Process of pulmonary respiration

  29. Mechanism of Breathing

  30. Regulation of Respiration

  31. Pneumonia Tuberculosis Symptoms Treatment

  32. Bronchitis – Acute bronchitis, Chronic Bronchitis Causes

  33. Circulatory System – Functioning of Human heart

  34. Cardiac Cycle

  35. Coronary blood vessel and its significance

  36. Myocardial infarction

  37. Angina pectoris

  38. Angiogram – Angioplasty

  39. Atherosclerosis

  40. Heart block Echo cardiography Heart Valves

  41. Rheumatic Heart Disease (RHD), ICCU – (Intensive Coronary Care Unit)

  42. Blood Pressure

  43. Heart transplantation

  44. Pulse rate

  45. Cardio Pulmonary Resuscitation (CPR)

  46. Blood – Composition of plasma – Blood cells

  47. Clotting of Blood or Haemostasis

  48. Thrombosis

  49. Nervous system Co-ordination systems

  50. The Brain – Fore Brain, Midbrain, Hindbrain

  51. Memory

  52. Sleep – Types of sleep

  53. Stroke – Brain haemorrhage

  54. Alzheimer – Meningitis (Brain fever)

  55. Conditioned reflex

  56. Electroencephalography EEG

  57. Right and Left brain concept

  58. Spinal cord functioning

  59. Chemical co-ordination – Functions of Endocrine glands

  60. Hypothalamus

  61. Pituitary gland – hormone

  62. Hormones of Neurohypophysis – vasopressin

  63. Thyroid gland

  64. Parathyroid Gland

  65. Pancreas

  66. Adrenal gland

  67. Gonads

  68. Receptor Organs – Eye

  69. Photochemistry of Retinal visual Pigments

  70. Errors of refraction

  71. Optometry – Retinopathy

  72. Cataract – Lens Replacement – Glaucoma – Nyctalopia

  73. Eye Infections and Eye Care

  74. Ear

  75. Mechanism of hearing

  76. Defects of the ear

  77. Hearing Aid – Noise pollution

  78. Skin and functions of skin

  79. Melanin functions

  80. Effects of solar radiation / UV radiation – Skin grafting

  81. Dermatitis

  82. Tongue – Mechanism of Stimulation

  83. Excretion Ureotelism Nephron

  84. Mechanism of urine formation

  85. Renal Failure, Dialysis, Kidney Machines

  86. Kidney stone – Kidney transplantation

  87. Diabetes mellitus

  88. Functioning of male reproductive system

  89. Functioning of female reproductive system

  90. Ovulation and fate of the ovum – Menstrual cycle

  91. Fertilization

  92. Birth control

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