Human Reproduction and development in detail from start to end:
  • extension refers to quantitative changes; development mention to qualitative changes; maturity is the end or goal or growth and development.
  • Heredity and environment determine rowing and maturing
  • Chromosomes which are order in 23 pairs, are found within the nucleus of every one cell in the body. Each
  • chromosome is construct up of long strands of DNA
  • Each chromosome carries a number of genes that carries of the hereditary traits.
  • Genes are dominant or recessive. The dominant gene determines the trait. Recessive gene lingers on from generation to generation but it will disclose soon.

Each person normally has one pair of chromosomes in each cell. The Y chromosome is present in males, who have one X and one Y chromosome, while females have two X chromosomes.

In multiple birth;
  • may Identical twins or triplets happen when a single egg is fertilized and then later splits. These freshly divided embryos are identical. Children that are identical multiples will look like each other and be the same.
  • Fraternal multiples develop from separate eggs that are fertilized by an unlike sperm. Because these are different eggs and different sperm, the genetic material is varied. These children won’t look identical and can be different from each other

The principle that control the process of heredity are:
  • The principle of reproduction
  • The principle of variation
  • The principle of chance
  • The principle of Linked traits
  • The principle of dominance and recessiveness.




Stages of Development:
life cycle of human being is unpredictability divided into periods or stages with each period being a part of the whole. Human development occur in an order and sequential pattern that is always predictable as changes are taking place in every stage of life. Prenatal Period This period starts from fertilization to birth. It begins as soon as the sperm unites with the egg cell. Such union of the sperm cell and the egg cell within the mother's body result in a new cell called zygote. The prenatal development last for about 266-280 days or around nine months. From single fertilized cell, it multiplies rapidly into 32 cells after 32 hours of fertilization until it grows to form like ball mass consisting about 200 billion of cells and soon differentiate into tissues, organs, systems and other body parts.

There are three stages in prenatal period:
  • Germinal Stage
  • Embryonic Stage
  • Fetal Stage

  1. GERMINAL STAGE (1-2 weeks):
    In humans, the first 1 to 2 weeks of prenatal life after fertilization, in which the fertilized egg (zygote) migrates to the uterus and becomes implanted in the endometrium. The embryonic stage follows the germinal stage
  2. EMBRYONIC STAGE (3-8 weeks)
    This stage last until the eighth week of conception. Oxygen and nutrients are passed on from the mother to the embryo thus setting the stage for rapid development. All the essential features of the body, both external and internal, are established at this stage. Eyes and spinal cord appears in about 21 days; heart is formed in about 24 days; arms and legs in about 28 days; features of the face take shape at about 42 days. The embryo is about 1 and 1 half inches long but already has the beginning of basic body organs and limbs and look like a human being.
    This stage is one of rapid change but it is the most critical period of prenatal development because the embryo is vulnerable to damage, defect and miscarriage. During this stage, almost all birth defects occur and if they from abnormally, the defect will be permanent. The embryo may develop webbed toes and fingers, blindness and deafness Caused by his mother with German measles, Detects or the heart, nose, mouth, anus, and other parts of the limb
  3. FETAL STAGE (9-40 weeks):
    The fetal, the third and last stage of the prenatal period, begins after eight weeks (two months) after conception and the last until birth. The developing organism is known as fetus. The seven month, the fetus resembles an old person with red wrinkled skin. On the seventh and eight months, the fetus often changes Its position During the fetal stage, the baby's brain develops and the body adds size and weight, until the fetus reaches full-term development.