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Incompatible blood. http://emedicine.medscape.com/article/797150-overview. FASD. Premature birth. http://www.marchofdimes.com/baby/long-term-health-effects-of-premature-birth.aspx# http://preemies.about.com/od/preemiehealthproblems/a/longtermimpact.htm. Chapter 16. Section 16.3 -2
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Incompatible blood • http://emedicine.medscape.com/article/797150-overview
Premature birth • http://www.marchofdimes.com/baby/long-term-health-effects-of-premature-birth.aspx# • http://preemies.about.com/od/preemiehealthproblems/a/longtermimpact.htm
Chapter 16 Section 16.3 -2 Embryonic and Fetal Development
Morphogenesis • The development of an organism or part of an organism. • Involves 2 process: • Growth – increase in size. • Differentiation – cell specialization.
Trimesters • The nine months of pregnancy are divided into 3 trimesters. • First Trimester – from conception until the end of the third month. • Second Trimester – from the fourth month to the end of the sixth month. • Third Trimester – from the seventh month until birth.
First Trimester (1-12 weeks) • Conception until the end of the third month. • Fertilization occurs. • Inner cells of the blastocyst have reorganized into a flattened disk made up or 2 layers. • Later this 2 layer structure turns into a 3 three layered structure called a gastrula, this process is called gastrulation.
The three layers of the gastrula are the ectoderm, mesoderm and endoderm. • Each of these layers will give rise to specific organs and structures. • Ectoderm (outer layer) gives rise to: • Skin, hair, finger nails, sweat glands • Nervous system, brain • Lens, retina, cornea • Inner ear, cochlea, semicircular canals
Mesoderm (middle layer) gives rise to: • Muscles • Blood vessels and blood • Kidneys, reproductive structures • Connective tissue, cartilage, bone • Endoderm (inner layer) gives rise to: • Liver, pancreas, thyroid, parathyroid • Urinary bladder • Lining of digestive system • Lining of respiratory tract
By the end of the first month, the embryo is about 1 cm long. • Many of the important organs and systems are beginning to develop. • The 4 chambered heart has formed, brain is visible and limb buds with tiny fingers and toes have developed.
By the ninth week the embryo is known as a fetus. • Arms and legs begin to move and a sucking reflex is evident.
Second trimester (14 – 24 weeks) • At the beginning the fetus is about 8 cm long. • All organs have formed, but not quite fully developed. • Organ development continues and fetus increases in size. • Movement of fetus occurs.
Soft hair covers the entire body. • By the sixth month eyelids and eyelashed form. • Bone cells replace cartilage that originally formed the skeleton. • At the end the fetus is about 34 cm long.
Third Trimester (25 – 40 weeks) • Baby grows rapidly. • All organs are fully developed but must enlarge. • Mass must increase. • At the end before birth, the infant is approximately 51 cm long.
Human sex determination • The sex of the baby is determined genetically. • Females have two ‘X’ chromosomes. • Males have an ‘X’ and a ‘Y’ chromosome. • The gene for sex determination is found on the Y chromosome and is called the SRY (sex-determining-region of the Y chromosome).
If the Y chromosome is present then the SRY gene is also present. • All fetuses are identical until the sixth or seventh week. • At this time if the SRY is present it will initiate the formation of testes in males which produce testosterone and cause the male characteristics to develop. • If the SRY is absent female characteristics will develop.
The balance of hormones in the bloodstream is extremely important during fetal development. • Males and females produce both estrogen and testosterone. • Males have more testosterone, and females have more estrogen but the other hormones are present as well. • If there is an abundance of male sex hormones during fetal development the fetus may have the outward characteristics of a male but have female DNA or vice versa. (Hermaphrodites)
Teratogens • Teratogen - Any chemical, infectious disease, or environmental agent that might interfere with the normal development of a fetus or embryo. • Ex. Social Drugs Medications Diseases Alcohol Thalidomide Rubella Cigarettes Seizure medication Herpes Cocaine
What’s next? Do: Study booklet 16.3 part 1& 2 • Monday • 16.3 part 2 • Tuesday • Quiz on 16.3 part 1& 2 & 16.3 part 3 • Wednesday • Health unit demos & concept map • Thursday • Review… jeopardy? • Friday • Unit B Exam: Reproduction & Development