The ectoderm is the outermost germ layer and is the first layer to form from a fertilized egg. The functions of the ectoderm include hormone regulation by the adenohypophysis, acting as a barrier against external involvement, and homeostasis. The ectoderm develops into: 
- outer skin (epidermis) and associated structures (hair, nails, sweat glands, mammary glands)
- Nervous tissue and sense organs
-pituitary gland
- adrenal medulla
- eye lens

The middle germ layer is the mesoderm it develops into:
- dermis of skin
-cellular lining of blood vessels, lymphatic vessels, body cavities
-muscle tissue
-connective tissue (including bone, cartilage,blood)
-Adrenal cortex
-hear
-internal reproductive organs
-kidneys and uterus
-spleen

This is the inner germ layer it develops into:
- Cellular lining of respiratory tract, digestive tract, urinary bladder, urethra 
-liver (most)
Gallbladder
-pancreas
-thymus
Tonsils (partial)
-parathyroid glands
- thyroid glands

• Ectopic pregnancy(tubal pregnancy) is a condition that can occur at this stage of pregnancy. This is when implantation occurs outside of the uterus. In most cases, surgery is required to remove the embryo/fetus.

• Estrogen and progesterone rise and cause your milk ducts to grow in number and size.
• your nipples darken and areolas become larger
• your Montgomery glands secrete oil to lubricate your nipple
• your body begins making colostrum
• Stage 2 lactogenesis: this stage starts about 2 or 3 days post partum
• - Once your baby and placenta are delivered, a sudden drop in your estrogen and progesterone causes the hormone prolactin to take over
• Prolactin is a hormone that produces milk
• You’ll notice milk production increases dramatically
• Your breasts are of engorged
• Stage 3 lactogenesis: This describes the rest of the time you lactate
• Generally continues as long as milk is removed from your breast
• The more milk is removed, the more milk you body makes to replace it

• Ayyasy, M. Zhafran. “Cannabis and male fertility : A systematic review.” Journal of Advance Research in Medical & Health Science (ISSN: 2208-2425), vol. 9, no. 5, 2023, pp. 15–20, https://doi.org/10.53555/nnmhs.v9i5.1664.
• Brents, Lisa K. “Marijuana, the Endocannabinoid System and the Female Reproductive System.” The Yale Journal of Biology and Medicine, U.S. National Library of Medicine, 27 June 2016, www.ncbi.nlm.nih.gov/pmc/articles/PMC4918871/#:~:text=Overall%20findings%20from%20human%20and,the%20gonadotropins%2C%20follicle%20stimulating%20hormone.
• Canada, Health. “Government of Canada.” Canada.Ca, Gouvernement du Canada, 14 Mar. 2023, www.canada.ca/en/health-canada/services/drugs-medication/cannabis/about.html.
• Colbourne, Helen. Inquiry into Biology. Alberta Education, Specialized Services for Students with Visual Impairment, 2017.
• Donaldson-Evans, Catherine. “Pregnancy.” What to Expect, 5 Oct. 2023, www.whattoexpect.com/pregnancy/.
• “Marijuana Use during Pregnancy: Is It Safe?” YouTube, YouTube, 19 July 2021, https://www.youtube.com/watch?v=qz4AGm5kPlQ. Accessed 22 Oct. 2023.
• Pruthi , Sandhya. “Pregnancy Week by Week In-Depth.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 4 Nov. 2022, www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/hlv-20049471. 
• Biology , O. Editors. (2023, April 28). Chorion - definition and examples - biology online dictionary. Biology Articles, Tutorials & Dictionary Online. https://www.biologyonline.com/dictionary/chorion 
  
  

The amnion is a transparent, fluid-filled sac that forms from the cells of the embryonic disk and surrounds the embryo during pregnancy. The amnion is penetrated with only the umbilical cord. The amniotic fluid serves to allow free fetal movement, cushion the embryo, and protect it against physical shocks, trauma and fluctuating temperature. The amniotic fluid also serves as a source of nutrients, hormones and antibodies, as well as a repository for water products produced by a developing fetus. It plays a critical role in the development of organs and body systems (i.e. the lungs and the respiratory system).

The yolk sac- also known as the umbilical vesicle,  is a small sac attached to the abdominal area of the embryo. It is the site for the initial formation of blood cells in the embryo and plays a role in the development of the circulatory system. It also contributes to the formation of the digestive tract.

The allantois is the foundation of the umbilical cord. It helps regulate gas and liquid exchange. By the second month after conception, most of the allantois degenerates while the remnant tissue develops into the urinary bladder. 

The chorion is the external membrane that encloses all other extra-embryotic structures and the embryo. The chorion plays a key role in the exchange of blood and gases between mother and fetus, helps to eliminate fetal waste and develops into the fetal part of the placenta. The placenta is a flat, circular organ by which the embryo/fetus is anchored to the uterine wall. The placenta is rich in blood vessels and serves to provide oxygen and nutrients to the developing embryo. The placenta will not fully develop until at around 10 weeks after fertilization.

This phase starts on day 1 of menstruation and lasts until ovulation. During this period, estrogen makes the endometrial lining of the uterus thicken up in preparation for a potential pregnancy. The secretion of estrogen creates a negative feedback loop to the hypothalamus and the pituitary, resulting in decreased secretion of FSH. Right before ovulation, however, estrogen initiates a positive feedback loop, making the pituitary extremely sensitive to the GnRH signal. This results in a surge of FSH and LH secretions,  which triggers ovulation.

This phase starts following ovulation and lasts until the next mensuration. During this period, progesterone acts in a negative feedback loop, signaling to the pituitary to secrete less LH. This results in menstruation.