Human Anatomy, First Edition McKinley & O'Loughlin

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Human Anatomy, First EditionMcKinley
O'Loughlin

• Chapter 28
• The Reproductive System

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Reproductive Systems

• Main function propagation of the species
• To achieve this goal
• Must ensure sexual maturation
• Produce gametes (n).
• Male and female structures are homologues
• derived from common developmental tissues

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Homologous structures
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Comparison of the Female and Male Reproductive
Systems

• Primary sex organs called gonads.
• ovaries in females
• testes in males
• Produce gametes which unite to form a new
  individual.
• oocytes
• sperm
• Gonads produce large amounts of sex hormones
  which affect maturation, development, and changes
  in the activity of the reproductive system
  organs.
• estrogen and progesterone in the female
• androgens (esp. testosterone) in the male

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Comparison of the Female and Male Reproductive
Systems

• Both have accessory reproductive organs
• duct systems
• carry gametes away from the gonads
• toward the site of fertilization in females
• to the outside of the body in males
• Fertilization occurs when male and female gametes
  meet
• copulation, coitus, sexual intercourse
• Restores the diploid number (2n)

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Comparison of the Female and Male Reproductive
Systems

• Primarily nonfunctional and dormant until
  puberty.
• At puberty, external sex characteristics become
  more prominent.
• breast enlargement in females
• fat distribution patterns in both sexes
• pubic hair in both sexes
• reproductive organs become fully functional
• gametes mature
• gonads secrete sex hormones
• Both reproductive systems produce gametes.

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Comparison of the Female and Male Reproductive
Systems

• Puberty
• Initiated by hypothalamus
• Secretes GnRH (gonadotropin-releasing hormone
• Stimulates release of FSH and LH
• Prior to puberty, not present
• Stimulate gonads to produce
• Sex hormones
• gametes

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Comparison of the Female and Male Reproductive
Systems

• Female typically produces and releases a single
  oocyte monthly.
• Male produces 100,000,000s of (sperm) daily.
• male gametes are stored for a short time
• if they are not expelled from the body within
  that period, they are resorbed

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Perineum

• Diamond-shaped area between the thighs that is
  circumscribed anteriorly by the pubic symphysis,
  laterally by the ischial tuberosities, and
  posteriorly by the coccyx.
• 2 distinct triangle bases
• formed by an imaginary horizontal line extending
  between the ischial tuberosities of the ossa
  coxae.
• Anterior triangle, or urogenital triangle
• contains the urethral and vaginal orifices in
  females
• contains the base of the penis and the scrotum in
  males.
• Posterior triangle, or anal triangle
• location of the anus in both sexes.

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Anatomy of the Female Reproductive System

• Peritoneum folds around the various pelvic organs
  and creates two major dead-end recesses, or
  pouches.
• anterior vesicouterine pouch forms the space
  between the uterus and the urinary bladder
• posterior rectouterine pouch forms the space
  between the uterus anteriorly and the rectum
  posteriorly
• Primary sex organs of the female are the ovaries.
  
• Accessory sex organs include
• uterine tubes
• uterus,
• vagina,
• clitoris
• mammary glands.

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• Mesovarium
• Double folds of peritoneum
• Attaches ovaries to broad ligament
• Broad ligament
• Peritonium
• Drapes over the uterus
• Ovarian ligament
• Ovary to uterus
• Suspensory ligament
• Ovary to pelvic wall

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Ovarian Follicles

• Within the cortex are thousands of ovarian
  follicles.
• Consist of
• Follicle cells
• granulosa cells
• nurse cells that support the oocyte
• a type of oocyte.
• Several different kinds of ovarian follicles,
  each representing a different stage of
  development.
• Oogenesis
• maturation of a primary oocyte to a secondary
  oocyte.

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Before Birth

• The process of oogenesis occurs in a female fetus
  before birth. At this time, the ovary contains
  primordial germ cells called oogonia, which are
  diploid cells, meaning they have 23 pairs of
  chromosomes.
• During the fetal period, the oogonia start the
  process of meiosis, but they are stopped at
  prophase I. At this point, the cells are called
  primary oocytes.
• At birth, the ovary of a female child is
  estimated to contain approximately 1.5 to 2
  million primordial follicles within its cortex.
• The primary oocytes in the primordial follicles
  remain arrested in prophase I until after
  puberty.

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From Puberty to Menopause

• During childhood ovaries are inactive, and no
  follicles develop.
• Atresia occurs, in which some primordial
  follicles regress or break down.
• By the time she reaches puberty only about
  400,000 primordial follicles remain.
• At puberty, the hypothalamus releases GnRH
  (gonadotropin-releasing hormone), which
  stimulates the anterior pituitary to release FSH
  (follicle-stimulating hormone) and LH
  (luteinizing hormone).
• The levels of FSH and LH vary in a cyclical
  pattern and produce a monthly ovarian cycle.
• The three phases of the ovarian cycle are the
  follicular phase, ovulation, and the luteal
  phase.

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The Three Phases of the Ovarian Cycle

• Follicular phase occupies days 113 of an
  approximate 28-day ovarian cycle.
• Ovulation occurs on day 14 of a 28-day ovarian
  cycle and is defined as the release of the
  secondary oocyte from a vesicular follicle.
• only one ovary ovulates each month
• Luteal phase occurs during days 1528 when the
  remaining follicle cells in the ruptured
  vesicular follicle turn into a corpus luteum.
• secretes progesterone and estrogen that stabilize
  and build up the uterine lining, and prepare for
  possible implantation of a fertilized oocyte
• has a life span of about 1013 days if the
  secondary oocyte is not fertilized
• it regresses and becomes a corpus albicans
• the uterine lining to be shed as menstruation
• menarche

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After Menopause

• The time when a woman is nearing menopause is
  called perimenopause.
• estrogen levels begin to drop, and
• a woman may experience irregular periods, skip
  some periods, or have very light periods
• When a woman has stopped having monthly menstrual
  cycles for 1 year and is not pregnant, she is
  said to be in menopause.
• The age at onset typically is between 45 and 55
  years
• follicles stop maturing, and significant amounts
  of estrogen and progesterone are no longer being
  secreted
• a womans endometrial lining does not grow, and
  she no longer has a menstrual period

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Uterine Tubes

• The uterine tubes, also called the fallopian
  tubes or oviducts, extend laterally from both
  sides of the uterus toward the ovaries.
• In these tubes, the secondary oocyte is
  fertilized, and the pre-embryo begins to develop
  as it travels toward the uterus.
• Usually it takes the pre-embryo about 5 to 6 days
  to reach the lumen of the uterus.
• Parts lined with mucosa (simple ciliated
  columnar ep), muscularis, serosa
• Infundibulum
• Ampulla
• Isthmus
• Interstitial segment

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The Uterus Serves Four Functions

• Site for implantation.
• pre-embryo implants into the inner uterine wall
  and becomes connected to the uterine lining
• Supports, protects, and nourishes the developing
  embryo/fetus
• forms a vascular connection with the mothers
  uterine wall that later develops into the
  placenta
• Ejects the fetus at birth after maternal oxytocin
  levels increase to initiate the uterine
  contractions of labor.
• Site for menstruation.
• if an oocyte is not fertilized or after a baby is
  expelled, the muscular wall of the uterus
  contracts and sheds its inner lining as
  menstruation

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Regions of the Uterus

• Fundus
• Body
• Isthmus
• Cervix
• Cervical canal
• Internal os
• External os

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Support of the Uterus

• Pelvic floor muscles
• Pelvic diaphragm
• Urogenital diaphragm
• Round ligaments
• Lateral uterus, through inguinal canal, to labia
  majora
• Maintain anteverted position
• Transverse cervical ligaments
• Lateral cervix and vagina to pelvic wall
• Uterosacral ligaments
• Inferior uterus to sacrum

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Wall of the Uterus

• Composed of three concentric tunics
• Perimetrium
• Myometrium
• Endometrium
• The outer tunic of most of the uterus is a serosa
  called the perimetrium.
• continuous with the broad ligament
• The myometrium is the thick, middle tunic of the
  uterine wall formed from three intertwining
  layers of smooth muscle.
• in the nonpregnant uterus, the muscle cells are
  less than 0.25 millimeters in length
• during the course of a pregnancy, smooth muscle
  cells increase both in size and in number

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Uterine (Menstrual) Cycle and Menstruation

• The menstrual phase occurs approximately during
  days 15 of the cycle. This phase is marked by
  sloughing of the functional layer and lasts
  through the period of menstrual bleeding.
• The proliferative phase follows, spanning
  approximately days 614. The initial development
  of the functional layer of the endometrium
  overlaps the time of follicle growth and estrogen
  secretion.
• The last phase is the secretory phase, which
  occurs at approximately days 1528. During the
  secretary phase, increased progesterone secretion
  from the corpus luteum results in increased
  vascularization and development of uterine
  glands.
• If the oocyte is not fertilized, the corpus
  luteum degenerates, and the progesterone level
  drops dramatically.
• Without progesterone, the functional layer lining
  sloughs off, and the next menstrual phase begins.

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Vagina

• The vagina is
• thick-walled, fibromuscular tube
• forms the inferior-most region of the female
  reproductive tract
• measures about 10 centimeters in length in an
  adult female.
• The vagina connects the uterus with the outside
  of the body anteroventrally
• functions as the birth canal.
• Also the copulatory organ of the female
• Serves as the passageway for menstruation.
• The vaginal wall is heavily invested with both
  blood vessels and lymphatic vessels.
• The vaginas relatively thin, distensible wall
  consists of three tunics
• an inner mucosa, a middle muscularis, and an
  outer adventitia

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External Genitalia

• The external sex organs of the female, are
  collectively called the vulva.
• The mons pubis is an expanse of skin and
  subcutaneous connective tissue immediately
  anterior to the pubic symphysis.
• covered with pubic hair in postpubescent females
• labia majora
• labia minora
• Contain the vestibule
• Urethral orifice
• Vaginal oriface
• Clitoris located at the anterior regions of the
  labia minora
• glans
• prepuce-an external fold of the labia minora that
  forms a hoodlike covering over the clitoris.

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Mammary Glands

• Each mammary gland, or breast, is located within
  the anterior thoracic wall and is composed of a
  compound tubuloalveolar exocrine gland.
• Breast milk contains proteins, fats, and a sugar
  to provide nutrition to infants.
• The nipple is a cylindrical projection on the
  center of the breast. It contains multiple tiny
  openings of the excretory ducts that produce
  breast milk.
• The areola is the pigmented rosy or brownish ring
  of skin around the nipple. Its surface often
  appears uneven and grainy due to the numerous
  sebaceous glands immediately internal to the
  surface.
• The color of the areola may vary, depending upon
  whether or not a woman has given birth. In a
  nulliparous woman (a woman who has never given
  birth), the areola is rosy or light brown in
  color.
• In a parous woman (a woman who has given birth),
  the areola may change to a darker rose or brown
  color.

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Anatomy of the Male Reproductive System

• Primary organs gonads are the testes
• Accessory sex organs include
• a complex set of ducts and tubules leading from
  the testes to the penis
• a group of male accessory glands
• the penis, which is the organ of copulation

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Scrotum

• Skin covered sac
• Raphe external midline seam
• Continues on inferior surface of the penis, and
  to anus.
• Components of scrotal wall.
• Skin
• Fascia
• Dartos muscle
• External spermatic fascia
• Cremaster muscle
• Internal spermatic fascia
• Tunica vaginalis.

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Scrotum

• Male gametes are sensitive to elevated
  temperatures
• often exhibit abnormal or completely curtailed
  development
• Gamete development occurs outside the body
• Scrotum a skin-covered sac that houses
• male gonads
• first portion of the duct system
• site of early sperm maturation and development,
  reside outside the body proper.
• Testes exposed to elevated temperatures
• Skin of the scrotal sac becomes thin
• result of dartos muscle relaxation.
• The cremaster muscle relaxes
• allows the testes to move inferiorly away from
  the body
• The testes temperature becomes less than normal
  body temperature.
• The opposite occurs if the testes are exposed to
  cold.

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Testes

• Small, oval organ
• Housed in the scrotum
• Produces
• Sperm
• androgens.
• Coverings
• Serous membrane called tunica vaginalis
• Parietal layer
• Visceral layer.
• Tunica albuginea
• Forms internal septa
• 250 lobules per testis
• Each lobule has up to 4 seminiferous tubules
• Two types of cell
• Sustentacular cells
• Germ cells
• Interior is called mediastinum testis.

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Testes

• Blood-testis barrier
• Tight junctions between sustentacular cells
• Spern develop in the semineferous tubules
• Interstitial spaces surround the seminiferous
  tubules.
• Contain interstitial (Leydig) cells
• produce hormones called androgens.
• Several types of androgens
• most common one is testosterone.
• the adrenal cortex secretes a small amount of
  androgens
• the vast majority of androgen release is via
  interstitial cells in the testis
• beginning at puberty.
• These hormones cause males to develop the classic
  characteristics
• axillary and pubic hair
• deeper voice
• sperm production.

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Testes

• Series of tubes
• Seminiferous tubules
• Straight ducts
• Rete testis
• Efferent ductule
• Epididymis
• Ductus deferens

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Spermatic Cord

• The blood vessels and nerves to the testis travel
  from within the abdomen to the scrotum in a
  multilayered structure called the spermatic cord.
• Layers
• Contain
• Testicular artery
• Pampiniform plexus
• Autonomic nerves

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Developmemt of sperm

• Called spermatogenesis
• Occurs in the seminiferous tubules
• Process
• Spermatogonium
• Primary spermatocyte
• Secondary spermatocyte
• Spermatid
• Spermiogenesis
• Spermatid matures into spermatozoon

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Epididymis

• The epididymis is a comma-shaped structure
  composed of an internal duct and an external
  covering of connective tissue.
• Its head lies on the superior surface of the
  testis, while the body and tail are posterior to
  the testis.
• Internally, the epididymis contains a long,
  convoluted duct of the epididymis, which is
  approximately 4 to 5 meters in length.
• Sperm must reside in the epididymis for a period
  of time to become mature and fully motile.
• If they are expelled too soon, they lack the
  motility necessary to travel through the female
  reproductive tract and fertilize an oocyte.
• If sperm are not ejected from the male
  reproductive system in a timely manner, the old
  sperm degenerate in the epididymis.

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Ductus Deferens

• When sperm leave the epididymis, they enter the
  ductus deferens, also called the vas deferens.
• The ductus deferens is a thick-walled tube that
  travels within the spermatic cord, through the
  inguinal canal, and within the pelvic cavity
  before it reaches the prostate gland.
• The ampulla of the ductus deferens unites with
  the proximal region of the seminal vesicle to
  form the terminal portion of the reproductive
  duct system, called the ejaculatory duct.

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Urethra

• Transports semen from the ejaculatory duct to the
  outside of the body.
• Subdivided into
• prostatic urethra that extends through the
  prostate gland
• membranous urethra that travels through the
  urogenital diaphragm
• penile urethra that ends through the penis
• Sperm leave the body through the urethra.

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Accessory Glands

• The vagina has a highly acidic environment to
  prevent bacterial growth.
• Sperm cannot survive in this type of environment,
  so an alkaline secretion called seminal fluid is
  needed to lessen the acidity of the vagina and
  bring pH values closer to neutral.
• As the sperm travel through the reproductive
  tract (a process that can take several days),
  they are nourished by nutrients within the
  seminal fluid.
• The components of seminal fluid are produced by
  accessory glands
• seminal vesicles
• prostate gland
• bulbourethral glands

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Seminal Vesicles

• The paired seminal vesicles are located on the
  posterior surface of the urinary bladder adjacent
  to the ampulla of the ductus deferens.
• Each seminal vesicle is an elongated, pouchlike
  hollow organ approximately 58 centimeters long.
• It is the proximal portion of each seminal
  vesicle that merges with a ductus deferens to
  form the ejaculatory duct.
• The seminal vesicles secrete a viscous,
  whitish-yellow alkaline fluid containing both
  fructose and prostaglandins.
• The fructose is a sugar that nourishes the sperm
  as they travel through the female reproductive
  tract, while the prostaglandins promote the
  widening and slight dilation of the external os
  of the cervix.

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Prostate Gland

• A compact encapsulated organ that weighs about 20
  grams and is shaped like a walnut, measuring
  approximately 2 cm by 3 cm by 4 cm.
• Located immediately inferior to the bladder.
• Secretes a slightly milky fluid that is weakly
  acidic and rich in citric acid, seminalplasmin,
  and prostate-specific antigen (PSA).
• citric acid is a nutrient for sperm health
• seminalplasmin is an antibiotic that combats
  urinary tract infections
• PSA acts as an enzyme to help liquefy semen
  following ejaculation

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Bulbourethral Glands

• Paired, pea-shaped
• Also called Cowpers glands
• Location
• within the urogenital diaphragm
• on each side of the membranous urethra.
• Each gland has a short duct
• projects into the base of the penis
• enters the spongy urethra.
• secretory product
• clear, viscous mucin (forms mucus when mixed with
  water).
• mucin protects the urethra
• serves as a lubricant during sexual intercourse.

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Semen

• Combination of seminal fluid from the accessory
  glands and sperm.
• Called the ejaculate (when released during
  ejaculation)
• normally about 3 to 5 milliliters
• contains approximately 200 to 500 million
  spermatozoa.
• Average transit time about 2 weeks
• from release of sperm into the lumen of the
  seminiferous tubules, passage through the duct
  system, and appearance in the ejaculate.
• Sperm count can vary, spemen amount usually
  remains the same.

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Aging and the Reproductive Systems

• Our reproductive systems are basically
  nonfunctional for several years following birth.
  When we reach puberty, hormonal changes in the
  hypothalamus and anterior pituitary gland
  stimulate the gonads to begin producing sex
  hormones.
• Thereafter, changes occur in many body
  structures, the reproductive organs mature, and
  gonads begin to produce gametes.
• Gametes stop maturing in females in their 40s or
  50s, and menopause occurs.
• A reduction in hormone production that
  accompanies menopause causes some atrophy of the
  reproductive organs and the breasts.
• The vaginal wall thickness decreases, as do
  glandular secretions for maintaining a lubricated
  and moist lining.
• The uterus shrinks and atrophies, becoming much
  smaller than it was before puberty.

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