Embryology Flashcards
How many chromosomes do the typical
(diploid) cells of the body have?
Typical (diploid) cells of the body have 46
chromosomes
How many chromosomes does each gamete
have?
What is the average length of PARTURITION?
Each gamete has 23 chromosomes.
► Prenatal period
 How long is the embryonic
period?
 How long is the fetal period?
DAY 1: What is the conceptus (developing
human) called?
Parturition means the length of the
pregnancy. The average length of parturition
is 280 days after the last menstrual period.
► Prenatal period
 Embryonic period – first 8 weeks
 Fetal period – remaining 30
weeks
DAY 1: The egg is one cell = ZYGOTE.
DAY 3: What is the conceptus called?
DAY 3: The egg has begun to divide =
MORULA. It is in this stage when it first enters
the uterus.
DAY 7: What is the conceptus called?
DAY 7: The egg is thousands of cells =
BLASTOCYST. It is in this stage when it begins
to implant into the uterus (week one) by
burrowing into it like a parasite.
DAY 60: What is the conceptus called.
DAY 60: The egg has now developed into a
FETUS
When a conceptus first enters the uterus, it is
in what stage?
Fertilization occurs when?
MORULA
Implantation occurs when?
Implantation occurs on about day 21 of the
menstrual cycle.
Fertilization occurs on about day 14 of the
menstrual cycle.
Embryology Flashcards
BLASTOCYST
The blastocyst contains what two cell types?
Which one forms the placenta?
What is hCG?
Where is it made?
What does it do?
What happens if it is not present?
Do the capillaries within a chorionic villus of
the placenta contain blood from the mother
or from the fetus?
Why is this important?
What condition is when the placenta implants
low and covers part of the cervix, so that a Csection must be performed?
What are the three primary germ layers, and
what do they give rise to?
1. Outer cells are the =TROPHOBLAST, which
forms the PLACENTA (note that the placenta is
made by the baby, not the mom)
2. The inner cells are the INNER CELL MASS,
which becomes the EMBRYO and surrounding
structures.
hCG (human chorionic gonadotrophin),
secreted by the trophoblast cells.
- This hormone maintains the corpus
luteum, which makes the progesterone
that maintains the uterine lining to grow.
- If no hCG, there will be menses.
- hCG is the hormone which is measured in a
pregnancy test. It will be in sufficient
quantities to be measured within about
one week after a missed period.
The trophoblast gives rise to the CHORION,
which have CHORIONIC VILLI that burrow into
the uterus. The capillaries within a chorionic
villus of the placenta contain blood from the
fetus ONLY, not the mother.
Therefore, this tissue can be used for genetic
testing for birth defects.
The placenta can implant anywhere in the
uterus. If it implants really low and covers
part of the cervix = PLACENTA PREVIA.
ECTODERM  skin and nervous system
MESODERM  muscles, bones, and blood
ENDODERM  the GI tract and other organs
brain
The anterior part of the neural tube becomes
what?
The posterior part of the neural tube becomes spinal cord
what?
Embryology Flashcards
What is the condition where the anterior part
of the neural tube does not fuse?
ANENCEPHALY (“without a brain”).
- The head ends at the eyebrows, and there
is no cerebrum.
- The brainstem still works, so the heart
beats for a few days.
- This can be detected by ultrasound.
What is the condition where the posterior
part of the neural tube does not fuse? Dietary
lack of what substance tends to cause this?
SPINA BIFIDA
- The baby can be paralyzed from the waist
down. Can be caused by lack of folic acid
When does the heart form?
When does the heart start to pump blood?
The most common birth defects involve
_____?
The heart forms in the third week.
The heart starts to pump at the start of the
fourth week.
The most common birth defects involve the
heart and circulation
Fetal Alcohol Syndrome
What is the most common cause of mental
retardation in the United States?
When can male and female fetuses first be
distinguished by their genitals?
What is a chemical, physical, or biological
agents that can induce birth defects called?
What organ does not develop until the 9 th
month?
Because that organ is not developed until the
9th month, what do premature babies lack?
What hormone triggers childbirth
contractions (smooth muscles of the
myometrium)?
3 months
A TERATOGEN
Lungs
Premature babies lack the slippery
SURFACTANT secretion in the lungs.
OXYTOCIN, which causes contraction of
smooth muscles of the myometrium.
- It is not know why this happens; maybe
the amount of fat deposition in the baby,
or the amount of surfactant.