human reproduction

• Puberty is the period during which adolescents start to develop secondary sexual characteristics
• In men, testosterone is the main reproductive hormone produced in the testes, stimulating sperm production
• In women, estrogen is the main reproductive hormone produced by the ovaries
• The menstrual cycle consists of four stages
• Stage 1: Menstruation - period of bleeding due to the breakdown of the uterus lining
• Stage 2: Uterus lining builds up again to prepare for a fertilized egg
• Stage 3: Ovulation - egg is released from the ovary
• Stage 4: Maintaining the uterus lining until the end of the cycle
• The average length of a menstrual cycle is around 28 days
• Menstruation lasts about four days
• Uterus lining builds up for around ten days up to day 14
• Ovulation takes place in a single day
• Stage 4 stretches from day 14 to day 28
• Hormones involved in the menstrual cycle
• Estrogen: produced in the ovaries, stimulates the uterus lining to grow
• Progesterone: also produced in the ovaries, maintains the uterus lining
• Luteinizing hormone (LH) and Follicle Stimulating Hormone (FSH): produced in the pituitary gland
• Interactions of hormones in the menstrual cycle
• Estrogen inhibits FSH
• FSH stimulates ovaries to produce estrogen
• High estrogen levels stimulate the release of LH, causing ovulation
• Progesterone inhibits both LH and FSH