Mod.A Embryology Lec7

Question 1

Life span:

Answer 1

I- Prenatal life (280 days, 40 wks, 10lunar months)
1- Preembronic stage: from fertilization to end of the 1st week .
2- Embryo: from 2nd week to end of 8th week.
3- Fetus: from 3rd month to delivery.

II- Postnatal life:
1- Neonatal: from birth to end of 2nd week.
2- Infancy: from 3rd week to end of 1st year.
3- Childhood: from 2nd year to 12-16 years (age of puberty).
4- Adolescence: 6 years after puberty.
5- Adulthood: from 20 year to 60 years.
6- Old age: More than 60 years.

Question 2

1st month of fetal growth

Answer 2

by the end of the first month, the embryo is about

0.25 cm long . The heart, which is no larger than a poppy seed, has begun beating.

Question 3

2nd month of fetal growth

Answer 3

Second Month the embryo is about 2.5 cm long and has distinct, slightly webbed fingers. Veins are clearly visible.
The heart has divided into right and left chambers

Question 4

3rd month of fetal growth

Answer 4

by now the fetus is 6.25 to 7.5 cm long and is

fully formed. He has begun swallowing and kicking. All organs and muscles have formed and are beginning to function.

Question 5

4th month of fetal growth

Answer 5

the baby is covered with a layer of thick,
downy hair called lanugo. His heartbeat can be heard
clearly. This is when mother may feel the baby first kick

Question 6

5th month of fetal growth

Answer 6

a protective coating called vernix caseosa begins

to form on baby’s skin. By the end of this month, the baby will be nearly 20 cm long and weigh almost 450g.

Question 7

6th month of fetal growth

Answer 7

eyebrows and eyelids are visible. The baby’s
lungs are filled with amniotic fluid, and he has started
breathing motions. If you talk or sing, he can hear you.

Question 8

7th month of fetal growth

Answer 8

by the end of the seventh month, the baby

weighs about 1.5 kg and is about 30 cm long. His body is well-formed. Fingernails cover his fingertips

Question 9

8th month of fetal growth

Answer 9

the baby is gaining about ¼ kg per week, and
layers of fat are piling on. He has probably turned head-down in preparation for birth. He weighs between 1.8 kg and 2.7 kg .

Question 10

9th month of fetal growth

Answer 10

the baby is a hefty 2.7 to 4 kg and measures

between 47.5 and 55 cm . As he becomes more crowded, mothers may feel him move around less.

Question 11

Delivery (defintion, when it occurs)

Answer 11

Parturition (childbirth) is the process during which the
fetus, placenta, and fetal membranes are expelled from
the mother.

It occurs 40 weeks after onset of the last menstruation or, more accurately 38 weeks after fertilization (it is only
accurate for the regular periods 28 days).

Question 12

Stages of labor

Answer 12

1st stage:

Uterine contraction start, labor pains & the cervix dilates,
with bulging of the bag of water which raptures releasing
amniotic fluid.

2nd stage:

Delivery of the baby, the umbilical cord is tied and cut.

3rd stage:

Delivery of the placenta and membranes (afterbirth).

Question 13

Causes of congenital malformations

Answer 13

Genetic factors
Chromosomal anomalies
Gene mutations

Environmental factors
Multifactorial inheritance
Unknown causes

Question 14

type of genetic factors chromosomal abnormalities

Answer 14

A-Numerical abnormalities:
Monosomy(of sex chromosome), Trisomy(of both sex and autosomes)

• —Structure abnormalities:

Question 15

Monosomy

Answer 15

Loss of an autosome is fatal.

Loss of sex chromosome→ death in 99% of cases . The remaining 1% → Turner syndrome 45XO

Question 16

Characters of turner syndrome

Answer 16

short stature, wide chest, spaced nipples,
primary amenorrhea due to
ovarian dysgenesis, and congenital
heart malformation

Question 17

Trisomy

Answer 17

Trisomy of autosomes:

Trisomy 13 → Patau’s syndrome.

Trisomy 21 or Down’s syndrome or mongolism 47XX or 47XY

Trisomy 17-18 →Edward’s syndrome

Trisomy of sex chromosome

Kleinfilter’s syndrome 47XXY.
Triple X syndrome,47XXX.
Super male 47XYY

Question 18

Environmental factors causing chromosomal abnormalities

Answer 18

1- Viruses
German measles, CMV, herpes simplex , varicella, HIV.
Others teratogenes; toxoplasmosis and syphilis,

2- Chemical and drugs:
smoking, caffeine, alcohol, cocaine, CNS drugs ,
thalidomide, hormones, anti thyroid drugs, cortisone ,
some antibiotics as tetracycline and streptomycin

3- Heavy metals as mercury, lead.

4- Physical agents as radiation , fever.

5- Maternal factors as diabetes mellitus, external
trauma, uterine malformations, and
oligohydramnios

0thers→ retinoid , anticoagulants, ACE, and cytotoxic
drugs.