Reproductive System (Pregnancy)

Question 1

Spermatogenesis

Answer 1

This is process of developing sperm from germ cells found in the seminiferous tubules of your testes. It starts off with a diploid cell (2n), primary spermatocyte, 2 rounds of meiosis which leads you to 4 haploid sperm cells.
- Interstitial Cells: LH is released from the pituitary gland and produces testosterone.
- Seminiferous Tubules: This is the site of spermatogenesis.
Sertoli Cells: FSH targets sertoli cells to nourish and support developing sperm cells.

Question 2

Oogenesis

Answer 2

The process where 4 haploid daughter cells (1 egg + 3 polar bodies) is produced from a primary oocycte in the ovaries by going through 2 rounds of Meiosis (FSH, LH, Corpus Luteum secretes progesterone, follicle secretes estrogen in order to thicken endometrium lining

Question 3

Menstruation Cycle

Answer 3

• Flow (Days 1-5): This is when estrogen and progesterone levels are low. It is the beginning of your cycle (menstruation) and your endometrium lining begins to shed.
• Follicular (Days 6-13): This is when FSH stimulates the follicles and estrogen is released from it. This is when your follicles begin development.
• Ovulatory (Day 14): The secondary oocycte bursts out from the the ovary and the remaining follicle cell turns into a corpus luteum and LH stimulates ovulation to happen which drop estrogen levels.
• Luteal (Days 15-28): This is when the endometrium and corpus luteum thicken and the uterus prepares to receive an egg. The corpus luteum secretes estrogen and progesterone, and if fertilization doesn’t occur the levels of estrogen and progesterone decrease leading to uterine contractions which lead to menstruation.

Question 4

Fraternal vs. identical Twins

Answer 4

Identical: This is a single egg fertilized by one sperm that splits into two.
Fraternal: This is two different eggs fertilized by two different sperm.

Question 5

Development

Answer 5

1. Ovaries (Oogenesis: 1 egg + 3 polar bodies) and Testes (Spermatogenesis: 4 sperm).
2. Ovulation (Egg is released after LH spike) and Ejaculation (Release of sperm)
3. Egg (Fallopian Tube) and Sperm (Fallopian Tube)
4. Fertilization (Union of egg and sperm in fallopian tube)
5. Zygote (46 chromosomes are immediately formed after union of egg and sperm)
6. Rapid Cell Division
7. Blastocyst (Bundle of cels after multiple divisions)
8. Implantation (In endometrium lining)
9. Gastrulation ( When an embryo changes from a single layer to multiple layers)
10. Fetus (Development continues - 8 weeks)
11. Birth (40 weeks)

Question 6

Layers of a Gastrula

Answer 6

• Ectoderm: Outer layer, skin, hair, finger nails, sweat glands, nervous system, brain, peripheral, lens, retina, cornea, ear.
• Mesoderm: Middle layer, muscle, blood and blood vessel, connective tissue/cartilage/bone, kidneys, and reproductive systems.
• Endoderm: Inner layer, Liver, pancreas, thyroid, parathyroid, bladder, digestive lining and respiratory system.

Question 7

Fetal Development Support

Answer 7

• Chorion Layer: Outer most layer of cells, that produces HCG that maintains the corpus luteum for the first three months of pregnancy. The maintenance of the corpus luteum keeps levels of estrogen and progesterone level high in order to prevent menstruation.
• Amnion Layer: This develops within the chorion layer and it is a fluid filled sac that insulates and protects the developing embryo (amniotic fluid).
• Yolk Sac: It is the original source of fetal red blood cells, lining of the digestive tract. It provides the embryo with nourishment and gas exchange before the placenta develops.
• Allantois: Gives rise to the umbilical cord.

The placenta is fully developed at the end of the first trimester (chorion + endometrium). It acts as the lung (gas exchange), kidney (waste exchange) and small intestine (nutrient exchange). When the placenta is fully formed the placenta will produce progesterone and estrogen to prevent uterine contractions and to prevent another pregnancy.