UNIT B: Human Body Systems

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UNIT B Human Body Systems

• Chapter 8 Human Organization
• Chapter 9 Digestive System
• Chapter 10 Circulatory System and Lymphatic
  System
• Chapter 11 Respiratory System
• Chapter 12 Nervous System
• Chapter 13 Urinary System
• Chapter 14 Reproductive System Section 14.3

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Chapter 14 Reproductive System
UNIT B
Chapter 14 Reproductive System
In this chapter you will learn about the male and
female reproductive systems, the ovarian and
uterine cycles, and disorders of the reproductive
systems.
What different events must occur before
fertilization? What is the function of the
umbilical cord?
Cord blood banking. Cord blood can be used to
treat diseases such as leukemia, lymphoma, and
other blood and immune system disorders. After an
umbilical cord blood sample is collected, it is
stored in a cord blood bank. There are both
private and public banks.
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14.3 Ovarian and Uterine Cycles
UNIT B
Section 14.3
Chapter 14 Reproductive System

• The menstrual cycle is a cyclical pattern that
  ensures an oocyte is released at the same time
  the uterus is most receptive to a fertilized
  oocyte.
• It consists of two cycles
• Ovarian cycle (takes place in the ovaries)
• Uterine cycle (takes place in the uterus)

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The Ovarian Cycle
UNIT B
Section 14.3
Chapter 14 Reproductive System

• Ovarian Cycle
• An ovary contains many follicles, each of which
  contains an immature oocyte
• A female is born with all the ovarian follicles
  she will ever have (about 700 000)
• Only about 400 follicles will mature to release
  an oocyte
• The ovarian cycle occurs as a follicle develops
  from a primary to a secondary to a vesicular
  (Graafian) follicle

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UNIT B
Section 14.3
Chapter 14 Reproductive System
Figure 14.7 Ovarian cycle. a. A single follicle
goes through six stages in one place within the
ovary. As a follicle matures, layers of follicle
cells surround the developing oocyte. Eventually,
the mature follicle ruptures, and the secondary
oocyte is released. The follicle then becomes the
corpus luteum, which eventually disintegrates.
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UNIT B
Section 14.3
Chapter 14 Reproductive System

• As the follicle matures in the ovarian cycle,
  oogenesis occurs.
• Oogenesis reduces the chromosome number from 46
  to 23
• If a sperm enters the secondary oocyte,
  fertilization occurs and the full number of
  chromosomes is restored

Figure 14.7 Ovarian cycle. b. During oogenesis,
the chromosome number is reduced from 46 to 23.
Fertilization restores the full number of
chromosomes.
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UNIT B
Section 14.3
Chapter 14 Reproductive System

• Phases of the Ovarian Cycle
• The ovarian cycle is divided into two phases.

• Follicular phase
• Follicle-stimulating hormone (FSH) produced by
  the anterior pituitary promotes the development
  of a follicle in the ovary
• The ovary secretes estrogen and some progesterone
• Elevated estrogen levels inhibit secretion of FSH
  to end the follicular phase

Figure 14.8 Hormonal control of ovaries.
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UNIT B
Section 14.3
Chapter 14 Reproductive System

• Luteal phase
• Increased estrogen causes a secretion of GnRH
  from the hypothalamus
• GnRH causes a surge in luteinizing hormone (LH)
  from the anterior pituitary, which causes
  ovulation
• LH promotes the development of the corpus luteum,
  which secretes progesterone and estrogen
• Progesterone inhibits LH, causing degeneration of
  the corpus luteum
• Low levels of estrogen and progesterone cause
  menstruation

Figure 14.8 Hormonal control of ovaries.
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The Uterine Cycle
UNIT B
Section 14.3
Chapter 14 Reproductive System

• The female sex hormones estrogen and progesterone
  affect the endometrium, causing the uterus to
  undergo a series of cyclical events known as the
  uterine cycle
• The uterine cycle is closely linked with the
  ovarian cycle
• Average length of uterine cycle 28 days (varies)

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UNIT B
Section 14.3
Chapter 14 Reproductive System

• Days 1 to 5
• Low levels of estrogen and progesterone cause the
  endometrium to disintegrate and its blood vessels
  to rupture
• Blood and tissues pass out of the vagina
  (menstruation)

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Figure 14.9
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UNIT B
Section 14.3
Chapter 14 Reproductive System

• Days 6 to 13
• Increased estrogen production by a new ovarian
  follicle causes the endometrium to thicken and
  become vascular (proliferative phase)

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Figure 14.9
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UNIT B
Section 14.3
Chapter 14 Reproductive System

• Day 14
• Ovulation usually occurs in the ovary

Figure 14.9
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UNIT B
Section 14.3
Chapter 14 Reproductive System

• Days 15 to 28
• Increased progesterone production by the corpus
  luteum causes the endometrium to thicken and the
  uterine glands to mature, producing a thick mucus
  secretion (secretory phase)

Figure 14.9
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UNIT B
Section 14.3
Chapter 14 Reproductive System

• Endometrium is now prepared to receive the
  developing embryo
• If an embryo does not implant, the corpus luteum
  degenerates and the low levels of estrogen and
  progesterone result in the endometrium breaking
  down during menstruation

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Figure 14.9
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UNIT B
Section 14.3
Chapter 14 Reproductive System
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Menstruation
UNIT B
Section 14.3
Chapter 14 Reproductive System

• Menstrual flow is a combination of endometrium,
  mucus, and blood descending from the uterus and
  through the vagina.
• The arteries that supply the uterine lining
  constrict and the capillaries weaken
• Blood from the damaged vessels detaches layers of
  the uterine lining in random patches
• Fibrolysin is an enzyme released by dying cells
  to prevent blood from clotting
• Abdominal camping, moodiness, and breast
  tenderness are normal during the menstrual period

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Fertilization and Pregnancy
UNIT B
Section 14.3
Chapter 14 Reproductive System

• If fertilization occurs, an embryo begins
  development as it travels down to the uterus
• The embryo implants into the uterine wall several
  days after fertilization (implantation is the
  beginning of pregnancy)

Figure 14.10 Implantation. a. Site of
implantation of an embryo in the uterine wall. b.
A scanning electron micrograph showing an embryo
implanted in the endometrium on day 12 following
fertilization.
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UNIT B
Section 14.3
Chapter 14 Reproductive System

• Placenta
• Originates from the maternal and fetal tissues
• Sustains the developing embryo
• Site of exchange of molecules between fetal and
  maternal blood
• Produces human chorionic gonadotropin (HCG),
  which maintains the corpus luteum until the
  placenta makes its own estrogen and progesterone
• Pregnancy tests detect the presence of HCG in the
  blood or urine by 10 days after fertilization
• Produces estrogen and progesterone to shut down
  the anterior pituitary so that no new follicle in
  the ovary matures and maintains the endometrium
  so that the corpus luteum is no longer needed

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Birth
UNIT B
Section 14.3
Chapter 14 Reproductive System

• The onset of labour occurs when uterine
  contractions occur every 10 to 15 minutes, and
  last at least 40 seconds.
• Positive feedback regulates labour (this cycle
  repeats itself until the baby is born)
• Uterine contractions are induced by the
  stretching of the cervix
• Cervical stretching causes oxytocin release from
  the posterior pituitary, which stimulates uterine
  contractions
• Uterine contractions push the fetus downward, and
  the cervix stretches even more

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Birth
UNIT B
Section 14.3
Chapter 14 Reproductive System

• Delivery occurs after the following events
• Uterine contractions become stronger and more
  frequent
• The amnion (containing amniotic fluid) ruptures,
  causing water to flow out of the vagina
  (breaking water)
• A mucus plug from the cervical canal leaves the
  vagina

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Lactation
UNIT B
Section 14.3
Chapter 14 Reproductive System

• Once the baby is delivered, the hormone prolactin
  is secreted from the anterior pituitary.
• Prolactin is needed for milk production, which
  takes a few days to begin
• Before milk production, the breasts produce
  colostrum, a milky fluid rich in protein,
  including antibodies
• When a breast is suckled, a nerve impulse travels
  from the nipples to the hypothalamus, which
  causes the pituitary to release oxytocin
• Oxytocin causes contraction of the lobules in the
  breast, so that milk flows out of the ducts (milk
  letdown)

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Menopause
UNIT B
Section 14.3
Chapter 14 Reproductive System

• Menopause occurs when the ovarian and uterine
  cycles cease (usually between the ages of 45 and
  55).
• Ovaries become unresponsive to FSH and LH and no
  longer secrete estrogen or progesterone
• A woman has completed menopause (and become
  infertile) after menstruation has been absent for
  a year
• Hormonal changes in menopause produce hot
  flashes, dizziness, headaches, insomnia, and
  depression

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Check Your Progress
UNIT B
Section 14.3
Chapter 14 Reproductive System

1. Summarize the events that occur during the two
   phases of the ovarian cycle.
2. Distinguish between the proliferative phase and
   the secretory phase of the uterine cycle and the
   hormones that promote each.
3. Describe the changes that occur in the ovarian
   and uterine cycles during menstruation,
   pregnancy, birth, lactation, and menopause.

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UNIT B
Section 14.3
Chapter 14 Reproductive System
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UNIT B
Section 14.3
Chapter 14 Reproductive System
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