A. First Lunar Month
1. Germ layers differentiate by the 2nd week (In cases of multiple congenital anomalies, the structures that will be affected are those that arise out of the same germ layer.)
a. Entoderm – develops into the lining of the GIT, the respiratory tract, tonsils, thyroid (for basal metabolism), parathyroid (for calcium metabolism), thymus glands (for development of immunity), bladder and urethra
b. Mesoderm – forms into the supporting structures of the body (connective tissues, bones, cartilage, muscles and tendons), heart, circulatory system, blood cells, reproductive system, kidneys and ureters
c. Ectoderm – responsible for the formation of the nervous system, the skin, hair and nails, the sense organs and mucous membrane of the anus and mouth.
2. Fetal membranes (amnion and chorion) appear by the second week
3. Nervous system very rapidly develops by the 3rd week (Dizziness is said to be the earliest sign of pregnancy because as the fetal brain rapidly develops, glucose stores of the mother are depleted, thus causing hypoglycemia in the latter)
4. Fetal heart begins to form as early as the 16th day of life (To the question, “When does the fetal heart begin to beat?”, the answer is the first lunar month. But to the question “When can fetal heart tones be first heard?”, the answer is fifth month.)
5. The digestive and respiratory tracts exist as a single tube until the 3rd week of life when they start to separate.
B. Second Lunar Month
1. All vital organs are formed by the end of the 8th week.
2. Placenta develops fully.
3. Sex organs (ovaries and testes) are formed by the 8th week. (To the question, “When is sex determined?”, the answer is at the time of conception.)
4. Meconium (first stools) are formed in the intestines by the 5th-8th week.
C. Third Lunar Month
1. Kidneys are able to function – urine formed by the 12th week
2. Buds of milk teeth form
3. Beginning bone ossification
4. Fetus swallows amniotic fluid
5. Feto-placental circulation is established by selective osmosis; no direct exchange between fetal and maternal blood
D. Fourth Lunar Month
1. Lanugo appears
2. Buds of permanent teeth form
3. Hearth beats audible with fetoscope
E. Fifth Lunar Month
1. Vernix caseosa appears
2. Lanugo covers entire body
3. Quickening (fetal movements) felt
4. Fetal heart beats very audible
F. Sixth Lunar Month
1. Skin markedly wrinkled
2. Attains proportions of full term baby
G. Seventh Lunar Month
1. Alveoli begin to form (28th weeks gestation is said to be the lower limit
of prematurity; if born, cries, breathes, but usually dies)
H. Eighth Lunar Month
1. Fetus is viable
2. Lanugo begins to disappear
3. Nails extend to ends of fingers
4. Subcutaneous fat deposition begins
I. Night Lunar Month
1. Lanugo and vernix disappear
2. Amniotic fluid volume somewhat decreases
J. Tenth Lunar Month – all characteristics of the normal newborn
No comments:
Post a Comment