Chapter 3 Conception and Prenatal Development Prenatal State of Development ends with the birth of the newborn infant The period that begins with conception and o Greatest point of opportunity risk vulnerability and resilience o Opportunity is afforded when a genetically healthy couple who have mutual affection conceive a child o Risk begins as the egg and sperm move toward each other and the developing baby gets exposed to harmful agents that can distort the fetus o Vulnerability derives from genetic factors o Resilience having this flexibility makes it possible to overcome many all the risks Conception Ancient Hindus believed 3 things were necessary to have a baby 1 Father contributed white semen to form child s bones 2 Mother provided red semen to produce the skin hair and iris of eyes 3 The rest was left to God to provide the expression of the face the child s sight hearing speech and movements Hippocrates Father of modern medicine Dr Martin Barrie came to conclusion that sperm and egg must unite to form fetus Female Reproduction o Menstrual Cycle they regulate timing of hormonal secretions and the processes i ii iii iv v vi Cycle begins with the onset of the menstrual period 4 5 days of bleeding Toward the end of the period a hormonal secretion from the pituitary gland stimulates the growth of several immature eggs in one of the two ovaries The eggs respond by starting to develop but only one egg ripens in each cycle if there are two twins As the egg ripens the ovary sends out a hormone progesterone which stimulates the endometrium linin of the uterus to prepare for the arrival of the fertilized egg Ovulation and 14 days after the first day of the cycle the egg breaks through the ovary wall Implantation the fertilized egg gets transported toward the uterus by hair like appendages with the lining of the fallopian tube where fertilization takes place and then lodges itself into the wall of the uterus The mature egg goes to the surface of the ovary o Ovarian Reserve o Menopause 50 Male Reproduction The remaining viable eggs The end of the repeating menstrual cycle usually at age o Sperm is produced in the testes o Scrotum is a sac that contains the testicles outside of the body where two oval shaped glands suspended into o 200 400 million sperm cells which each ejaculation of semen o There is not much of a schedule as for women however the sperm will enter the uterus and then most arrive to the fallopian tube where they will begin to eat away the coating of the egg for penetration o When the egg gets penetrated a chemical reaction prevents another sperm to enter and prenatal development has begun Infertility 75 of women fail to become pregnant after one month of unprotected intercourse 37 after six months and 20 after one year Infertile Women s fertility drops with age Men s fertility increases to 25 levels off unable to conceive after one year of sexual relations 1 in 6 couples from 26 36 and then decreases Male Infertility o Common problem is overheating of the testicles The testicles can produce live healthy sperm at a temperature below normal body temperature The cooling of the testicles is from the scrotum Showers not baths Baths overheat the testicles Long distance bike riding can be bad from the heat generated by the seat and up against the testicles Men should not have laptops in their laps Decreases sperm count o Accidental injury to the nerves and blood vessels of the testicles Injury causes the development of scar tissue blood clots and adhesions that can negatively impact these structures o Marijuana and alcohol Semen volume is reduced and sperm cells become over activated in ejaculation with the use of marijuana swim too hard fast wearing themselves out before reaching fallopian tubes With prolonged use of alcohol males reduce semen volume and many irreversible changes in testicular function and malformed sperm o Semen Analysis Medical way to count healthy live sperm from ejaculation Female Infertility o Endometriosis A buildup in the fallopian tubes of sloughed off endometrial cells from the uterus Common cause of infertility in women More likely to happen to women in later years An ovary develops a small cyst on its o Polycystic Ovary Syndrome surface as a result of ovulation The surface becomes overwhelmed which leads to irregularity in menstrual periods Present at birth but symptoms don t show until adolescence 10 of women are effected Can become pregnant but high rate of miscarriage and complications o Prolonged use of alcohol results in reduction of luteinizing hormone and follicle stimulating hormone o Cervical Hostility o Corpus Luteum can fail o Ovarian Cancer Prenatal Development Prenatal Stage of Development fertilization to birth Last on average 266 days Trimesters Better way of measuring prenatal development three month periods the period of time from the date of a Period of the zygote ovum germinal period i First two weeks of prenatal stage ii Cells being to divide at a very rapid rate and cells begin to differentiate into distinct layers to form organs b Period of the embryo i Third week to the eighth week ii All major organ system of the baby are formed EXCEPT genitals c Period of the fetus fetal Period of the Zygote Ovum o The first 3 days the fertilized egg stays in fallopian tube o Cell divides into two cells at 36 hours then several more divisions o By 72 hours it has developed into a ball of cells which moves toward o Blastocyst beginning of second week where there is a hollow fluid uterus filled balls of cells Seven to nine days after fertilization blastocyst embeds itself into endometrial lining of uterus RISKY PROCESS Failure rate is 50 o Implantation o Failure to implant can result from inadequate hormonal preparation of the endometrium or abnormal development of blastocyst Period of the Embryo o Placenta organ that sustains the baby by allowing oxygen and nutrients from blood to give to baby and get rid of wastes containing two arteries and one vein where the placenta is attached to the baby It is a tube o Umbilical Cord o By the fourteenth day the balls become ectoderm brain spinal cord nerves and skin mesoderm skeletal systems muscles heart and kidneys and endoderm digestive tract respiratory system pancreas and liver and now is referred to as an embryo o Organogenesis o Critical period o At the end of this period organisms take human form and systems organ systems developing time when organ is developing most rapidly function o By the
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