The Reproductive System

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The Reproductive System
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What is the primary function of the reproductive
system?

• To produce gametes
• To produce reproductive hormones
• To promote growth
• To promote maturation

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Male Anatomy

• Sex organs consist of gonads,internal accessory
  ducts and glands and external reproductive
  structures known as genetalia.
• Male Gonads - produce gametes and hormones
• Testes (means witness in latin, men in ancient
  Rome placed on hand on genitals) -sperm producing
• From the testes - sperm go to epididymis gt ductus
  deferens gturethra
• Accessory sex glands are seminal vesicles,
  prostate, and bulbourethral which empty
  secretions into the ducts during ejaculation

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The ______ is (are) responsible for producing
semen.

• testes
• seminal vesicles
• prostate gland
• b and c

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Seminiferous tubules

• Coiled tubes in 250-300 compartments
• Leave the testis and join the epididymis, a
  single duct that forms a coiled cord
• Seminiferous tubules (sperm factory) have 2 types
  of cells
• Spermatocytes
• Sertoli cells

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• Scrotum -viable sperm cannot be produced at core
  body temperature so the scrotum provide a
  temperature 3 degrees C lower.
• The scrotum also responds to temperature to
  maintain a fairly constant temperature.
• Testes each contain seminiferous tubules that act
  as sperm factories
• The tubules converge to form a straight tubule
  that conveys sperm to the rete testis, and then
  they leave through the efferent ductules and
  enter the epididymis

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Duct system

• Epididymis - immature sperm are moved through the
  duct.
• Takes 20 days - sperm gain the ability to swim
• When smooth muscle of epididymis contracts,
  expelling sperm to the ductus deferens
• Sperm can be stored for many months - if longer
  they are phagocytized.

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Ductus deferens

• Propels sperm from storage site in the epididymis
  into the urethra
• Vasectomy cutting the vas in the scrotal sac.
  Sperm no longer reach exterior

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Accessory glands

• Seminal vesicles, bulbourethral glands, prostate
  gland
• 1. Seminal vesicles lie on the posterior wall of
  the bladder
• Secretion is 60 of volume of sperm an alkaline
  fluid of fructose sugar, ascorbic acid, a
  coagulating enzyme, and prostaglandins.
• Sperm and seminal fluid mix in a duct and enter
  the urethra

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Prostate gland

• Encircles urethra inferior to the bladder
• Made of tubular alveolar glands in smooth muscle
• Secretion is 1/3 of semen volume
• Contains citrate, a nutrient, enzymes, and an
  antigen that activates sperm
• Empties directly into urethra

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Bulbourethral gland

• Produce mucus prior to ejaculation of sperm
• Empties secretions into the urethra through a
  duct

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Spermatogenesis and meiosis

• Spermatagonia in the seminiferous tubules enlarge
  to form a primary spermatocyte -gtsecondary
  spermatocyte -gtspermatids -gtsperm
• During the change from spermatocyte to spermatid,
  the 46 chromosomes (23 pairs) of the spermatocyte
  divide, so that 23 go to one spermatid and the
  other 23 to the second.
• During meiotic division, the male Y chromosome
  goes to one spermatid and becomes the male sperm,
  and the female X goes to another and becomes a
  female sperm. The sex is determined by which of
  these fertilizes the ovum.

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Spermiogenesis - streamlining

• 1. Undergoes a streamlining process called
  spermiogenesis. Sheds its excess cytoplasm and
  forms a tail
• 3. Result sperm has
• head - genetic
• midpiece - metabolic (mitochondria ATP)
• tail - locomotor region
• 4. Sustentacular cells form the blood-testis
  barrier, nourishing spermatogenic cells, move
  them to lumen of tubules, and secrete fluid for
  sperm transport

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As many as _______ sperm are made each day.

• 300
• 3000
• 400 million
• 750 trillion

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Sperm

• Semen ejaculated is 3.5 ml or 120 million sperm
• So about 400 million sperm are present in several
  ml
• When falls below 20 million infertility
• Majority of abnormal sperm infertility

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Male hormonal regulation

• GnRH, from hypothalamus, stimulates the ant.
  pituitary to release FSH and LH into the blood.
• Testosterone is secreted by the interstitial
  cells of Leydig in the testes when stimulated by
  LH. This provides negative feedback
• To initiate spermatogenesis, both FSH and
  testosterone are needed

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Male hormonal function

• Testosterone is secreted in the 7 week old embryo
  and continues for 10 weeks, then is turned off
  until puberty. Remains high until about age 50
  and then decreases by 50
• Testosterone involved in
• muscle development
• Increases bone matirx
• Changes the pelvis by making it longer
• Increases BMR by up to 15
• Voice, baldness, skin

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If testosterone were ineffective during
development of a males rain, what might be the
outcome?

• The brain would develop without any noticeable
  difference from other males.
• The brain might have a female orientation.
• Gender identity may be ambiguous.
• Both b and c are possible.

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Female system

• Ovaries - female gonads are the primary
  reproductive organ
• Dual purpose
• 1. Female sex hormones - estrogens and
  progesterone
• 2. Forms gametes

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Ovaries

• Paired ovaries flank uterus
• Each ovary held in place by ligaments
• Every 28 days, gonadotropic hormones from the
  ant. pituitary cause -
• 8-12 follicles to grow in the ovaries
• 1 matures and ovulates on the 14th day
• Ovulation a ripening follicle ejects its oocyte

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Female duct system
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• Falopian tube extends from ovary to the uterus
• Distal end expands and forms ampulla where
  fertilization occurs
• Ends in infundibulum, a funnel with fimbriae that
  drape over ovary
• Cilia propels oocyte into the falopian tube and
  toward the uterus

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Uterus

• Hollow, thick-walled organ that receives and
  retains a fertilized ovum
• Body major portion
• Fundus rounded superior region
• Cervix narrow neck/outlet that projects into
  vagina
• Supported by mesentary and ligaments

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Uterine wall

• 3 layers perimetrium, myometrium, endometrium
• Perimetrium - outer serous layer
• Myometrium - mid layer of smooth muscle
• Endometrium - mucosal lining

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Endometrium

• Straight artery that serve basalis and spiral
  arteries
• Thin walled veins
• 2 strata
• Functionalis -undergoes cyclic changes in
  response to blood levels of ovarian hormones and
  is shed during menstration
• Basalis - forms a new layer after menstration

functionalis
basalis
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Female Physiology-Oogenesis

• Oogenesis - the beginning of the egg. 1 year to
  complete
• Before birth -oogonia or diploid stem cells of
  ovaries multiply by mitosis, then enter a growth
  phase.
• This creates 500,000 primary oocytes

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• By birth, a females lifetime supply of primary
  oocytes - 2 million of them- are in cortex of the
  immature ovary.
• Remain suspended through childhood until age
  10-14
• Puberty, 400,000 oocytes remain.
• 1st and 2nd meiotic divisions occur in ovary
  after puberty
• Some are activated monthy by hormones and 1 is
  selected to continue meiosis I

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• Each month 1 primary ooctye completes meiosis I,
  producing a large secondary oocyte
• Meiosis II of the secondary oocyte produces a
  functional ovum, but meiosis II does not occur
  unless the secondary oocyte is penetrated by
  sperm

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Ovarian cycle

• Rhythmical changes leading to the maturation of a
  single ovum - 28 days
• 2 phases
• 1. Follicular growth- follicle growth of ovary.
  Day 1-14
• 2. Luteal phase - corpus luteum activity. Day
  14-28

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Follicular phase

• Follicular growth - several primary follicles
  mature to
• 2. Secondary or mature follicle
• Growing follicle produces estrogen
• The growth of this follicle is stimulated by FSH
  that is stimulated by estrogen
• 4. Fluid-filled cavity forms called the antrum.
  

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Luteal phase

• After expulsion of the ovum from the follicle,
  (day 15-28), the follicle enlarges and fills with
  a fluid or luteinizes to form a corpus luteum
• that secretes progesterone and estrogen, but
  mainly progesterone
• Dependent upon LH secreted by the ant.pit.
• If fertilization does not occur, the luteum
  degenerates in about 10 -12 days

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Ovulation

• Ovary wall ruptures and expels the oocyte
• lt2 of ovulations, more than 1 oocyte is
  ovulated can result in multiple births
• Fraternal twins nonidentical twins are
  different oocytes
• Identical twins fertilization of a single
  oocyte by a single sperm followed by separation
  of the fertilized eggs daughter cells

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Hormonal regulation of the ovarian cycle

• Hormonal controls at puberty
• A hypothalmic releasing hormone
  gonadodtropin-releasing hormone (GnRH),
• The anterior pituitary sex hormones FHS, LH
  that are released in response to GnRH
• The ovarian hormones, estrogen and progesterone,
  secreted by the ovaries in response to the female
  sex hormones from the anterior pituitary
• These hormones are not secreted constantly, but
  at differing rates during different times of the
  cycle

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Hormonal interactions during ovarian cycle
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• A. Pituitary gonadotropins - LH and FSH
  regulate the events of the ovarian cycle
• B. Estrogens and progesterone cause changes in
  the uterus
• High estrogen levels are responsible for a surge
  in LH/FSH

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Menstrual cycle

• 1. Days 1-5 Menstrual phase uterus sheds all
  but the deepest endometrium
• Gonadotropins are rising and ovarian hormones are
  low. FSH begins to rise
• 2. Days 6-14 Proliferative phase
• Endometrium rebuilds with rising estrogen.
  Glands enlarge, spiral arteries increase
  endometrium becomes thick and well-vascularized.
• Estrogens induce synthesis of progesterone
  receptors
• Rising estrogen causes cervical mucus to thin and
  form channels that will facilitate sperm passage
• Ovulation at end of this stage in response to gt LH

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• Days 15-28 Secretory phase endometrium prepares
  for inplantation.
• Rising levels of progesterone cause spiral
  arteries to coil. Uterine glands enlarge and
  secrete glycoproteins that sustain the embryo
  until it has implanted.
• Increasing progesterone cause mucus to form a
  plug that blocks sperm
• If no ferttilization, corpus luteum degenerates,
  LH declines, progesterone declines
• With no hormonal support, spiral arteries kink,
  dont get oxygen setting the stage for
  menestration

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The menstrual and proliferative phases overlap
the follicular phase and ovulation in ovarian
cycle.
Uterine secretory phase corresponds to the
ovarian luteal phase.
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Effects of estrogen and progesterone

• 1. Estrogen promotes ovulation.
• 2. At puberty, it stimulates the growth of
  reproductive organs and the growth spurt that
  promotes appearance of secondary sex
  characteristics (breasts, fat, pubic hair,
  calcium uptake).
• 3. Progesterone cooperates with estrogen in
  breast maturation and regulation of the uterine
  cycle. In pregnancy - prepares breast for
  lactation

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Estrogen

• Increased osteoblastic activity
• Increased protein deposition
• Increased metabolic rate
• Skin texture

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The pill

• Estrogen or progesterone given during the first
  half of the monthly cycle inhibit ovulation

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Menopause

• After about 400 of the primordial follicles grow
  to mature follicles and ovulate
• Ovulation stops
• Estrogen levels fall

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Progesterone

• Promotes secretory changes in the uterine
  endometrium
• Breast swelling and development of the alveoli