The Reproductive Systems

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The Reproductive Systems

• The male and female reproductive systems
• -produce gametes, that is, sperm and egg
  cells, and
• -ensure the union of gametes in
  fertilization
• - in women, the uterus provides the site
  for the developing embryo/fetus until it is
  sufficiently developed to survive outside the womb

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MEIOSIS

• The cell division process of meiosis produces the
  gametessperm or egg cells.
• In meiosis, one cell with the diploid number of
  chromosomes (46 for humans) divides twice to
  form four cells, each with the haploid number of
  chromosomes.
• Haploid means half the usual diploid number, so
  for humans the haploid number is 23.

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SPERMATOGENESIS

• Spermatogenesis is the process of meiosis as it
  takes place in the testes,.
• Within each testis are seminiferous tubules that
  contain spermatogonia, which are stem cells that
  generate sperm.
• A spermatogonium divides by mitosis to form two
  cells, one of which will remain in place as a
  stem cell, while the other differentiates
  (specializes) to become a primary permatocyte
  that will undergo meiosis .

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Role of Hormones

• Follicle-stimulating hormone (FSH) from the
  anterior pituitary gland initiates sperm
  production.
• Testosterone,secreted by the testes when
  stimulated by luteinizing hormone (LH) from the
  anterior pituitary, promotes the maturation of
  sperm.
• Inhibin, also produced by the testes,
  decreases the secretion of FSH.
• For each primary spermatocyte, four
  functional sperm cells are produced.

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Sperm Ova production

• Sperm production begins at puberty (10 to 14years
  of age), and millions of sperm are formed each
  day in the testes. Although sperm production
  diminishes
• with advancing age, there is usually no complete
  cessation, as there is of egg production in women
  at menopause

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OOGENESIS

• Oogenesis is the process of meiosis for egg cell
  formation
• it is regulated by hormones
• - FSH initiates the growth of ovarian
  follicles, each of which contains an oogonium, a
  stem cell for egg cell production .
• This hormone also stimulates the follicle
  cells to secrete estrogen, which promotes the
  maturation of the ovum.

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Notice

• for each primary oocyte that undergoes
  meiosis, only one functional egg cell is
  produced. The other three cells produced are
  called polar bodies. They have no function,
• and will simply deteriorate.
• A mature ovarian follicle actually contains the
  secondary oocyte.
• The second meiotic division will take place if
  and when the egg is fertilized

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Oogenesis

• The production of ova begins at puberty (10 to
  14years of age) and continues until menopause (45
  to 55years of age), when the ovaries atrophy and
  no longer respond to pituitary hormones.
• During this 30- to 40-year span, egg production
  is cyclical, with a mature ovum being produced
  approximately every 28 days
• Actually, several follicles usually begin to
  develop during each cycle.
• However, the rupturing (ovulation) of the first
  follicle to mature stops the growth of the others

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Fertilization

• It is union of nuclei of sprm ovum
• The haploid egg and sperm cells produced by
• meiosis each have 23 chromosomes.
• When fertilizaTion occurs, the nuclei of the egg
  and sperm merge,and the fertilized egg (zygote)
  has 46 chromosomes, the diploid number.
• Thus, meiosis maintains the diploid number of the
  human species by reducing the number of
  chromosomes by half in the formation of
• gametes

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MALE REPRODUCTIVE SYSTEM

• The male reproductive system consists of
• 1- two testes
• 2- series of ducts epididymis, ductus deferens,
  ejaculatory duct, and urethra .
• 3- the reproductive glands
• seminal vesicles, prostate gland, and
  bulbourethral glands.

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TESTES

• The testes are located in the scrotum, a sac of
  skin between the upper thighs.
• The temperature within the scrotum is about 34c,
  slightly lower than body temperature, which is
  necessary for the production of viable sperm.
• In the male fetus, the testes develop near the
  kidneys, then descend into the scrotum just
  before birth. Cryptorchidism is the condition in
  which the testes fail to descend, and the result
  is sterility unless the testes are surgically
  placed in the scrotum.

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Testis

• Each testis is about 1.5 inches long by 1 inch
  wide (4 cm by 2.5 cm) and is divided internally
  into lobes
• Each lobe contains several seminiferous tubules,
  in which spermatogenesis takes place.
• Among the spermatogonia of the seminiferous
  tubules are sustentacular (Sertoli) cells,
  which produce the hormone inhibin when stimulated
  by testosterone.

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Testis

• Between the loops of the seminiferous tubules are
  interstitial cells, which produce testosterone
  when stimulated by luteinizing hormone (LH) from
  the anterior pituitary gland.
• Besides its role in the maturation of sperm,
  testosterone is also responsible for the male
  secondary sex characteristics, which begin to
  develop at puberty .

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sperm cell

• A sperm cell consists of several parts
• - The head contains the 23 chromosomes.
• -On the tip of the head is the acrosome, which
  is similar to a lysosome and contains enzymes to
  digest the membrane of an egg cell.
• - Within the middle piece are mitochondria that
  produce ATP.
• -The flagellum provides motility. It is the
  beating of the flagellum that requires energy
  from ATP.
• Sperm from the seminiferous tubules enter a
  tubular network called the rete testis, then
  enter the epididymis, the first of the
  reproductive ducts.

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EPIDIDYMIS

• The epididymis (plural epididymides) is a tube
  about 20 feet (6 m) long that is coiled on the
  posterior surfaceof each testis.
• within the epididymis the sperm complete their
  maturation, and their flagella become functional.
• Smooth muscle in the wall of the epididymis
  propels the sperm into the
• ductus deferens.

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DUCTUS DEFERENS

• Also called the vas deferens,
• It extends from the epididymis in the scrotum on
  its own
• side into the abdominal cavity through the
  inguinal
• canal.
• This canal is an opening in the abdominal wall
• for the spermatic cord, a connective tissue
  sheath
• that contains the ductus deferens, testicular
  blood
• vessels, and nerves.
• Because the inguinal canal is an opening in a
  muscular wall, it is a natural weak spot, and
  it is the most common site of hernia formation in
  men

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• Once inside the abdominal cavity, the ductus
  deferens extends upward over the urinary bladder,
  then down the posterior side to join the
  ejaculatory duct on its own side .
• The smooth muscle layer of the ductus deferens
  contracts in waves of peristalsis
• as part of ejaculation

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EJACULATORY DUCTS

• Each of the two ejaculatory ducts receives sperm
  from the ductus deferens and the secretion of the
  seminal vesicle on its own side.
• Both ejaculatory ducts empty into the single
  urethra

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SEMINAL VESICLES

• The paired seminal vesicles are posterior to the
  urinary bladder .
• Their secretion contains fructose to provide an
  energy source for sperm and is
• alkaline to enhance sperm motility.
• The duct of each seminal vesicle joins the
  ductus deferens on that side to form the
  ejaculatory duct.

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PROSTATE GLAND

• A muscular gland just below the urinary bladder,
  it is 3 cm by 4 cm by 2 cm, about the size of a
  walnut).
• It surrounds the first inch of the urethra as
  it emerges from the bladder .
• The glandular tissue of the prostate secretes an
  alkaline fluid that helps maintain sperm
  motility.
• The smooth muscle of the prostate gland
  contracts during ejaculation to contribute to the
  expulsion of semen from the urethra

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BULBOURETHRAL GLANDS

• Also called Cowpers glands, about the size of
  peas and are located below the prostate gland
  they empty into the urethra.
• Their alkaline secretion coats the interior of
  the urethra just before ejaculation,which
  neutralizes any acidic urine that might be
  present.
• the secretions of the male reproductive glands
  are alkaline. This is important because the
  cavity of the female vagina has an acidic pH
  created by the normal flora .

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URETHRA

• The urethra is the last of the ducts through
  which semen travels,
• - and its longest portion.
• Circumcision is the surgical removal of the
  foreskin
• This is a common procedure performed on male
  infants,

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SEMEN

• Semen consists of sperm and the secretions of the
  seminal vesicles, prostate gland, and
  bulbourethral glands
• its average pH is about 7.4. During ejaculation.
• approximately 2 to 4 mL of semen is expelled.
• Each milliliter of semen contains about 100
  million sperm cells

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CONTRACEPTION

• There are several methods of contraception, or
• birth control some are more effective than
  others.
• SterilizationSterilization in men involves a
• relatively simple procedure called a vasectomy.
• The ductus (vas) deferens is accessible in the
  scrotum, in which a small incision is made on
  either side. The ductus is then sutured and cut.
• Although sperm are still produced in the
  testes, they cannot pass the break in the ductus,
  and they simply die and are reabsorbed.

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Sterilization in women

• Sterilization in women is usually accomplished by
  tubal ligation, the suturing and severing of the
  fallopian tubes by way of a small incision in the
  abdominal wall.
• Ova cannot pass the break in the tube, nor can
  sperm pass from the uterine side to fertilize an
  ovum.
• When done properly, these forms of surgical
  sterilization are virtually 100 effective.

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Oral contraceptives

• Birth control pills contain progesterone and
  estrogen in varying proportions. They prevent
  ovulation by inhibiting the ecretion of FSH and
  LH from the anterior pituitary gland.
• When taken according to schedule, birth control
  pills are about 98 effective

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PROSTATIC HYPERTROPHY

• Prostatic hypertrophy is enlargement of the
• prostate gland.
• Benign prostatic hypertrophy is a common
  occurrence in men over the age of 60 years.
• The enlarged prostate compresses the urethra
• within it and may make urination difficult or
  result in urinary retention.
• A prostatectomy is the surgical removal of part
  or all of the prostate.
• Newer surgical procedures may preserve sexual
  function.
• Medications are available to shrink enlarged
  prostate tissue.

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Cancer of the prostate

• is the second most common cancer among men (lung
  cancer is first). Most cases occur in men over
  the age of 50
• years.
• Treatment may include surgery to remove
• the prostate, radiation therapy, or hormone
  therapy to reduce the patients level of
  testosterone