Regents Prep: Living Environment: Reproduction:
Human Reproductive System

Male System
The structure and function of the human male reproductive system, is very similar to that of many other mammals.   The male system is designed to make sperm or male gametes and is adapted to provide for the delivery of these gametes to the female to allow for fertilization.

Male Reproductive System 

Male Reproductive System Structures

1.   testes -- produces sperm and the hormone testosterone

2.  scrotum -- pouch enclosing the testes keeping the sperm at an optimum temperature for development 

3.  vas deferens -- tube carrying sperm away from the testes

4.  prostate gland -- the largest of several glands which add lubricating and other fluids to the sperm 

-- this combination of sperm and fluids is called semen

5.  urethra -- tube through the penis carrying sperm to the outside of the body

6.  penis -- adaptation for internal fertilization of the female

Female System
The structure and function of the human female reproductive system, is very similar to that of many other mammals.   It is designed to produce female gametes or eggs, allow for internal fertilization, support the internal development of the embryo and fetus, and provide nutrition through milk for the newborn.  

Female Reproductive System

Female Reproductive System Structures

1.  ovary -- (females have two of these) -- produce female gametes or eggs and the hormone estrogen

2.  oviduct (fallopian tube) -- carries the egg away from the uterus

 -- internal fertilization normally occurs here

3.  uterus -- implantation and development of the embryo and fetus before birth occurs here

4.  vagina or birth canal -- entry point for sperm from the male and exit tube for the baby when it is born

Endocrine Interactions
Human reproduction and development are influenced by factors such as gene expression, hormones, and the environment. The reproductive cycle in both males and females is regulated by several different hormones.   Some of these hormones include:

testosterone --  produced by the testes in the male and stimulates the development of male secondary sex characteristics (like facial hair and deeper voice).
estrogen -- produced by ovaries in the female and stimulates the development of female secondary sex characteristics (wider hips and mammary glands) as well as starting the thickening of the uterus lining in preparation for a possible pregnancy after the egg is released by the female each month.
progesterone -- produced by yellow tissue called corpus luteum in the empty ovarian follicle (place in ovary producing and releasing the egg) -- this hormone maintains the thickness of the uterus lining in case fertilization occurs and development of a fetus occurs.

In human females of reproductive age, these hormones interact in a cyclic pattern called the menstrual cycle.  This pattern of events repeats itself on average every 28 days unless a pregnancy or other disruption occurs.   A graphic representation and written description of the stages of the human menstrual cycle is provided below.

                                 Human Menstrual Cycle

Note the influence of the hormone progesterone in beginning the thickening of the uterus lining and the role of the hormone estrogen in maintaining the thickness of that lining.   Ovulation or release of the egg occurs at the midpoint of this cycle, while the uterine lining thins and is shed (menstruation) when the level of estrogen begins to decline to a large extent.

Menstrual Cycle Stages

1. follicle stage (10-14 days average duration)

  •  production of ova/eggs occurs in tiny cavities in the ovary called follicles
  • enlarging follicle produces estrogen which causes the uterus to get ready for embryo implantation (uterus thickens its lining)

2. ovulation (1 day)

  • follicle enlarges and ruptures ovary wall
  • egg is released to the oviduct (usually only 1 is released at a time)

3. corpus luteum stage (10 -14 days average duration)

  •  yellow tissue fills the follicle after ovulation called the corpus luteum
  • "yellow body" secretes progesterone which maintains the thickness of the uterus in case a pregnancy occurs

4. menstruation (3-5 days average duration)

  • periodic shedding of the thickened lining of the uterus which occurs if fertilization does not occur

 
 

 

Created by James M. Buckley, Jr.
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