Fetal Development and Pregnancy Flashcards
1
Q
Describe oogenesis.
A
- Production or development of an ovum (divides to give rise to embryo)
- Begins during embryological and fetal development of the female
2
Q
Describe oogenesis in relation to the cell cycle.
A
- All potential eggs are established as an embryo: start to undergo first meiotic division to replicate DNA, but stop before its finished
- After onset of puberty, 1 oocyte matures q28 days and completes the first meiotic division
- 2 unequal cells – secondary oocyte and a small polar body
- Contain 22 autosomes and 1 X chromosome
- After ovulation, second meiotic division begins – completes only if fertilized
3
Q
Describe spermatogenesis.
A
- Production or development of mature sperm
- Spermatogonium – primitive sperm cells produced in the testes at onset of puberty
4
Q
Describe spermatogenesis in relation to the cell cycle.
A
- First meiotic division – 2 haploid secondary spermatocytes are formed
- Each contains 22 autosomes and 1 sex chromosome
- Secondary spermatocytes divide results in 4 sperm
5
Q
Describe the ovum during fertilization.
A
- Fimbria of uterine tubes pulls ovum into tube
- Corpus luteum on the ovary produces progesterone
- Two protective layers: zona pellucida and corona radiate
- Viable for approx. 24 hours after ovulation
6
Q
Describe the sperm during fertilization.
A
- Approx. 1tsp of semen = 200-500 million sperm
- Tail of sperm contain mitochondria
- Head of sperm contain enzymes that help get past those protective layers of the ovum
- Viable for up to 5 days
7
Q
What happens during ovulation?
A
- Sperm and ovum meet in ampulla (outer third) of the uterine tube
- Chemical reaction prevents more than one sperm from entering the ovum – called the zona reaction
- Restores the diploid number to form zygote
8
Q
What are embryo (until 8 weeks gestation) susceptible to?
A
Teratogens:
- Infections: Rubella, toxoplasma, TORCH
- Environmental exposures: heat, toxins
- Chemical exposures: alcohol, medications
9
Q
Structure of the placenta?
A
- Derived from the trophoblast cells of the blastocyst, has 2 layers.
- Circulation begins around day 17
- Large network of blood vessels that invades maternal circulation
- Facilitates embryonic blood circulating by day 21
- Intervillous spaces
- Maternal blood provides oxygen and nutrients
- Exchanges waste and carbon dioxide from the fetus
10
Q
Functions of the placenta?
A
- Endocrine
- Immune barrier (semipermeable membrane)
11
Q
List additional information about the placenta.
A
- Maternal side is rough and convoluted
- Dull red in color due to maternal blood
- Fetal side is shiny and smooth
- Weighs about 1lb at term
- Until week 16 the placenta grows in thickness and circumference
- Remainder of pregnancy only grows in circumference
- Viral infections can influence thickness of placenta
- Contains approx. 500mL of blood at term
- Blood in the intervillous space is replenished 3-4 times every minute
12
Q
Where is amniotic fluid produced? How much amniotic fluid is present at term?
A
- Produced by fetal kidneys & lungs at 10 weeks
- At term, approximately 1000 mL
13
Q
What is the purpose of amniotic fluid?
A
- Maintains constant temperature
- Cushions fetus
- Allows movement and development of fetal limbs
- Provide vitamins, proteins, IgG, electrolytes
- Antibacterial properties
- Important to fetal lung development
14
Q
Describe Polyhydramnios.
A
- Too much amniotic fluid
- Risk of cord prolapse upon rupture
15
Q
Describe Oligohydramnios.
A
- Too little amniotic fluid
- Risk of poor fetal lung development;
fetal demise
