Forming a new life Flashcards
What is fertilization?
Fertilization, or conception, is the process by which sperm and ovum combine to create a single cell called zygote, which then duplicates itself by cell division to produce cells that make up a baby.
What are dizygotic twins?
Dizygotic twins, or fraternal twins, are the result of two separate eggs being fertilized by two different sperm to form two unique individuals.
What are monozygotic twins?
Monozygotic twins result from the cleaving of one fertilized egg and are generally genetically identical, though they can differ outwardly due to the interaction between genes and environmental influences.
What is Deoxyribonucleic Acid (DNA)?
DNA is the ‘stuff’ in heredity.
What are chromosomes?
Chromosomes are coils of DNA that consist of smaller segments called genes.
What occurs during the first month of prenatal development?
During the first month, growth is more rapid than at any other time during life; the embryo reaches a size 10,000 times greater than the zygote, measuring about ½ inch in length.
What happens by the end of the second month of prenatal development?
By the end of the second month, the embryo becomes a fetus, measuring less than 1 inch long and weighing only 1/3 ounce, with developed facial parts and limbs.
What developments occur by the end of the third month?
By the end of the third month, the fetus weighs about 1 ounce and measures about 3 inches in length, with fingernails, toenails, eyelids, vocal cords, lips, and a nose.
What changes occur by the end of the fourth month?
The fetus now measures 8 to 10 inches and weighs about 6 ounces, with the mother possibly feeling the fetus kicking, known as quickening.
What is notable about the fetus at 5 months?
At 5 months, the fetus weighs about 12 ounces to 1 pound and measures about 1 foot, with definite sleep-wake patterns and active movements.
What developments occur by the end of the sixth month?
By the end of the sixth month, the fetus is about 14 inches long and weighs 1 1/4 pounds, with fat pads under the skin and the ability to hear.
What happens by the end of the seventh month?
The fetus is about 16 inches long and weighs 3 to 5 pounds, with fully developed reflex patterns and the ability to cry, breathe, and swallow.
What is the size and weight of the fetus at 8 months?
The 8-month-old fetus is 18 to 20 inches long and weighs between 5 and 7 pounds, with movements becoming more limited due to cramped living quarters.
What occurs by the end of the ninth month?
By the end of the ninth month, the fetus stops growing, averaging 7½ pounds and 20 inches in length, with organ systems operating more efficiently.
What is the germinal stage?
The germinal stage lasts from fertilization to about 2 weeks, during which the zygote divides, becomes complex, and implants in the uterus.
What occurs during the embryonic stage?
The embryonic stage lasts from about 2 to 8 weeks, during which organs and major body systems develop rapidly, a process known as organogenesis.
What is the fetal stage?
The fetal stage begins at about 8 weeks and is characterized by rapid growth and the development of organs and body systems until birth.
