3.10 Menstrual Cycle

Understand the roles of oestrogen and progesterone in the menstrual cycle. 

 1. Endocrine glands = produce hormones (chemical messengers) which are released into the blood from a gland and travel to a target organ. The main glands in the Menstrual cycle are the ovaries. "Endocrine gland ----> (hormones) --> target tissue ---> effect."

2. Endometruim = is the process of cell division of the human embryo that occurs during early stages of development. It exactly spans from the first moment of fertilization to the end of the 8th week of development.




3.  Menstrual cycle =  Lasts about 28 days
Main features of the menstrual cycle.

• The start of the cycle, day 1, is when bleeding from the vagina begins. This is caused by the loss of the lining of the uterus, with a little blood. This is called menstruation or having a period.
  
• By the end of about day 5, the loss of blood stops. The lining of the uterus begins to re-grow and an egg cell starts to mature in one of the ovaries.
  
• At about day 14, the mature egg cell is released from the ovary. This is called ovulation. The egg cell travels through the egg tube towards the uterus.
  
• If the egg cell does not meet with a sperm cell, the lining of the uterus begins to break down and the cycle repeats.