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. 

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.

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 SPECIES…SOME OF US MUST REPRODUCE!

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.

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:

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.

Male Reproductive System

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.

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.

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.

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. 

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.

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.

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.

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.

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.

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.

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

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.

Female Reproductive System

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

Female Reproductive System

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

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

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

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.

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.

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

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.

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.

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.