The Human Reproductive System

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The Human Reproductive System

• The gonads-testes and ovaries-are endocrine
  glands that secrete sex hormones.  However, the
  primary function of the gonads is not to produce
  hormones but to produce and store gametes-sperm
  and eggs. 

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Objectives

• 1. Identify the major structures of the male and
  female reproductive system. 2. Describe the
  function of each structure of the male and female
  reproductive system.

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Reproductive System

• The Reproductive System, unlike other systems we
  have studied, IS NOT ESSENTIAL to the survival of
  an INDIVIDUAL.
• What the Reproductive System is important to is
  the Survival of the SPECIES.  Reproduction is
  absolutely essential to the continuation of the
  SPECIESSOME OF US MUST REPRODUCE!

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Review

• The ways in which the Gametes are released make
  possible the fusion of Sperm (Male Gametes) and
  Egg (Female Gametes) in the process of
  FERTILIZATION.  From a Fertilized Egg, or ZYGOTE,
  come all the cells in a human body.

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SEXUAL DEVELOPMENT

• For the First SIX Weeks after fertilization,
  human male and female Embryos are Identical in
  appearance.
• During the SEVENTH Week of development, major
  changes occur

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7th week changes

• A.  The TESTES, which are the PRIMARY
  Reproductive Organs of a MALE, begin to produce
  Steroid Hormones (Sex) known as ANDROGENS.  The
  tissue of the Embryo responds to these hormones
  by developing into the MALE REPRODUCTIVE ORGANS.
•     B.  The OVARIES, or the PRIMARY Reproductive
  Organs of a FEMALE Embryo, produce Steroid
  Hormones (Sex) known as ESTROGENS. The tissue of
  the Embryo responds to these hormones by
  developing into the FEMALE REPRODUCTIVE ORGANS.
• . Neither Testes or Ovaries are capable of
  producing Active Reproductive Cells (GAMETES)
  until PUBERTY.

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Male Reproductive System
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THE MALE REPRODUCTIVE SYSTEM

• 1. Males begin to produce Sperm during Puberty,
  the adolescent stage of development when changes
  in the body make reproduction possible.
• 2. At this time, the concentration of the hormone
  Testosterone is high enough to stimulate sperm
  production.  Testosterone is the Main Androgen
  (Male Sex Hormone) produced by the Testes.
• 3. The TESTES develop within the Abdominal
  Cavity, just before birth the Testes descend
  through a canal into an EXTERNAL SAC called the
  SCROTUM.

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Male Reproductive System

• 4. The Testes (two egg-shaped structures) remain
  in the Scrotum, outside the body, where the
  temperature is about 3 degrees C Cooler than the
  body internal temperature (27 degrees C).
• 5. Sperm development in the Testes Requires the
  Lower Temperature.

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Male Reproductive System

• 6. The Testes are clusters of hundreds of Tiny
  Tubules called SEMINIFEROUS (sehm-uh-NIHF-er-uhs)
  TUBULES, which means "SEED BEARING".  Sperm Form
  through Meiosis in the specialized lining of this
  extensive network of tubules.
• 7. As the Pituitary Gland begins to release FSH
  and LH, these Hormones stimulate the Testes to
  make the PRINCIPAL MALE SEX HORMONE TESTOSTERONE.
  
• 8. Cells that respond to Testosterone are found
  all over the body.
• 9. Testosterone produces a number of SECONDARY
  SEX CHARACTERISTICS that appear in Males at
  Puberty Voice Deepens, Beard Grows, and Body
  Hair.

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Male Reproductive System

• 10. FSH and Testosterone stimulate the
  development of Sperm.  When large numbers of
  sperm have been produced in the Testes, the
  development process of Puberty is completed - THE
  REPRODUCTIVE SYSTEM IS NOW FUNCTIONAL. 

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Sperm Development

• 1. Sperm are derived from Special Cells within
  the Testes that go through the process of MEIOSIS
  to form HAPLOID NUCLEI found in Mature Sperm. 
  The Chromosome number drops from 46 to 23, Four
  sperm cells result from each cell that begins
  meiosis.
• 2. A Mature Sperm consists of THREE Regions
•     A.  HEAD - which contains the Nucleus (The 23
  Chromosomes) and enzymes that help the sperm
  penetrate the protective layers that surround and
  Egg Cell.
•     B.  MID PIECE - packed with energy releasing
  Mitochondria (Energy Source).  The Mitochondria
  supply the energy that is required for sperm to
  reach an Egg.
•     C.  TAIL Consists of a Single, Powerful
  FLAGELLUM that propels the Sperm.

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Male Reproductive System

• 4. Although most Sperm remain stored in each
  Epididymis, some leave the Epididymis and pass
  into through the VAS DEFERENS, a duct that
  extends from the Epididymis.
• 5. Each Vas Deferens enters the Abdominal Cavity,
  where it loops around the Urinary Bladder and
  merges with the Urethra.  In a Male, both Urine
  and Sperm exit the body through the Urethra.
• 6. In the Urethra, Sperm Mix with Fluids that are
  secreted by Three Exocrine Glands- the Seminal
  Vesicles, Bulbourethral Glands, and the Prostate
  Gland- to produce SEMINAL FLUID -which Protects
  and Nourishes the Sperm.

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Male Reproductive System

• THE COMBINATION OF SPERM AND SEMINAL FLUID IS
  KNOWN AS SEMEN
• BETWEEN 100 AND 200 MILLION SPERM ARE PRESENT IN
  1 milliliter OF SEMEN OR ABOUT 5 MILLION SPERM
  PER DROP!
• The Penis is the Male Reproductive Organ that
  makes it possible for Sperm to be delivered to
  the body of the Female.

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Male Reproductive System

• 300 - 400 million Sperm are released in the
  Reproductive Tract of a Female during a single
  Ejaculation the chances of a Single Sperm
  Fertilizing and Ovum (Egg OR Female Gamete), if
  one is available, are quit GOOD
• Most sperm are Killed by the Acidic Environment
  of the Female Reproductive Track. Only a few
  Sperm reach the site of Fertilization.

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Female Reproductive System

• The Ovaries are located in the Lower Abdominal
  Cavity the Ovaries USUALLY produce only ONE EGG
  or OVUM per month.
• In addition to producing eggs, the female
  reproductive system has another important job to
  perform - EACH TIME AN EGG IS RELEASED, THE BODY
  MUST BE PREPARED TO NOURISH A DEVELOPING EMBRYO.

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Female Reproductive System

• Puberty in females starts with changes in the
  Hypothalamus that causes the release of FSH and
  LH from the Pituitary Gland.
• FSH (follicle stimulating hormone) stimulates
  cells within the Ovaries to produce the Hormone
  ESTROGEN.
• Estrogen causes the reproductive system to
  complete its development, and also produce
  SECONDARY SEX CHARACTERISTICS - Enlargement of
  Breast and Reproductive Organs, Widening of the
  Hips, and growth of Body Hair.

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Female Reproductive System

• Each Ovary contains about 400,000 PRIMARY
  FOLLICLES, which are clusters of cells
  surrounding a single ovum (egg).
• 2. During her lifetime fewer than 500 Ova (Eggs)
  will actually be released, averaging one egg
  about every 28 days.
• When a Follicle has completely matured, the Ovum
  (Egg) is released.  THIS PROCESS IS CALLED
  OVULATION

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Female Reproductive System

• If TWO Eggs mature, Fraternal, or Non Identical
  Twins may result.
• Ovulation begins at Puberty and USUALLY
  continues until a female is in her late forties,
  when MENOPAUSE occurs.
• During Ovulation the Follicle literally ruptures,
  and the Ovum is swept from the Ovary into one of
  the TWO FALLOPIAN TUBES.  The Fallopian Tubes
  provide a way for an egg to travel from the Ovary
  to the Uterus.

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Female Reproductive System
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Female Reproductive System

• IT IS DURING ITS JOURNEY THROUGH THE FALLOPIAN
  TUBE THAT AN EGG CAN BE FERTILIZED.  An Egg must
  be fertilized within 48 hours of its release -
  after that, the egg begins to break down. 
  Unfertilized eggs dissolve in the Uterus.
• After a FEW DAYS, the Ovum passes from the
  Fallopian Tube into the UTERUS

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Female Reproductive System

• Leading from the Uterus (CERVIX) to the outside
  of the body is a muscular tube called the VAGINA
  or Birth Canal.

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Menstrual Cycle

• THE MENSTRUAL CYCLE IS THE SERIES OF CHANGES THAT
  OCCUR IN THE UTERUS EACH MONTH.
• The Menstrual Cycle has FOUR Stages THE
  FOLLICULAR PHASE, OVULATION, THE LUTEAL PHASE AND
  MENSTRUATION
• These Stages are Regulated by the Hormones of the
  Endocrine System

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Menstrual Cycle

• During the 1st Stage-THE FOLLICULAR PHASE, the
  Egg Matures, and the Lining of the Uterus GROWS
  THICKER, many tiny Blood Vessels grow into the
  thickened lining, in preparation for receiving a
  Fertilized Egg.
• The development of an Egg in this stage of the
  Cycle takes about 14 DAYS

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Menstrual Cycle

• The 2nd Stage, OVULATION, the shortest phase in
  the Cycle (3-4 DAYS), is the release of an egg
  from a ruptured follicle. Following Ovulation, an
  egg is swept into a fallopian tube, where it
  travels toward the uterus awaiting
  fertilization.  The Egg has enough stored
  nutrients to survive about 48 hours.

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Menstrual Cycle

• The 3rd Stage, LUTEAL PHASE, lasts about 14 Days,
  the Cells of the Ruptured Follicle grow larger
  and fill the cavity, forming a New Structure
  called a CORPUS LUTEUM.  The Corpus Luteum begins
  to secrete large amounts of PROGESTERONE and
  ESTROGEN.  The Increase levels cause the
  Pituitary Gland to stop Secreting LH and FSH.

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Menstrual Cycle

• Progesterone causes the lining of the Uterus to
  become even thicker
• The Lining is prepared to receive the Embryo four
  or five days after the Egg is released from the
  Ovary.
• An Embryo that settles into the lining of the
  uterus, the Corpus Luteum continues to release
  Hormones that causes the Uterus to maintain its
  thickened lining.
• Most of the time, no embryo arrives, and the
  Corpus Luteum begins to produce Less and Less
  Estrogen and Progesterone

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Menstrual Cycle

• The Decrease in Levels of Estrogen and
  Progesterone causes the Blood Vessels in the
  uterine lining to begin closing and then Break.
• The Cells of the Uterine lining DO NOT receive
  adequate blood supply and come loose from the
  inside of the uterus
• The mixture of Blood and the Cells that made up
  the lining of the uterus is called MENSTRUAL
  FLUID.

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Menstrual Cycle

• The passage of this Fluid through the Vagina and
  out of the body is called MENSTRUATION OR THE
  MENSTRUAL PERIOD THE LAST STAGE. IT USUALLY LASTS
  FROM THREE TO SEVEN DAYS.  At the end of the
  Period, a NEW Cycle Begins- THE FOLLICULAR PHASE.
  
• The AVERAGE Menstrual Cycle is 28 DAYS LONG.

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Menstrual Period

• Almost ALL Women START their Menstrual Period 14
  DAYS AFTER Ovulation occurs.
• The length of the First stage of the cycle, the
  period when the Follicle is growing, DIFFERS from
  women to women.