Transcript Reproductive_System

REPRODUCTION
Reproductive system functions in gamete
 Production
 Storage
 Nourishment
 Transport
Fertilization
 Fusion
zygote
of male and female gametes to form a
Cellular Reproduction
Mitosis – exact duplication of genetic material to
produce daughter cells which are genetically
identical to parent cell.
Mitosis produces all the somatic cells of the body
(non-gametes),
Diploid Cell – 46 Chromosomes
Gametes (sperm and eggs).
Sexual Reproduction
Meiosis – division which reduces the number
of chromosomes to produce haploid (half the
number of chromosomes) gametes.
Two division phases: produces 4 sperm in
males and 1 egg in females
Crossover magnifies the genetic variability.
MALE REPRODUCTIVE
SYSTEM
COMPONENTS
testes: produce spermatozoa (male
reproductive cells) and androgens (male
hormones)
 ducts: epididymis, vas (ductus) deferens,
urethra (prostatic, membranous, spongy)
 accessory glands: prostate, seminal vesicles,
bulbourethral (Cowper’s)
 supporting structures: scrotum, penis

FIGURE 28.1 THE MALE REPRODUCTIVE
SYSTEM
Figure 28.1
FIGURE 28.3 THE MALE REPRODUCTIVE
SYSTEM IN ANTERIOR VIEW
Figure 28.3
DEVELOPMENT
testes develop inside the abdominal cavity;
descend and exit via the inguinal canals
prior to birth
 need to exit the abdominal cavity due to high
temperature that prevents sperm formation
 failure to descend: cryptorchidism, causes
sterility
 high temperature causes infertility;
pampiniform plexus of testicular vein cools
testis

LOCATION AFTER BIRTH

located in the scrotum (sac attached to the
perineum)

cradled by cremaster muscle (extension of the
internal oblique muscle)

connected via spermatic cord: made of
testicular artery and vein, vas deferens, nerves
TESTICULAR STRUCTURE
fibrous tunica albuginea covers the outside;
inward extensions, called septa, create
lobules within the testes
 seminiferous tubules within the lobules
produce spermatozoa (s. spermatozoon)
 interstitial cells of Leydig are found in the
spaces between the seminiferous tubules

FIGURE 28.4 THE STRUCTURE OF THE
TESTES
Figure 28.4
SPERMATOGENESIS

Seminiferous tubules
 Contain
 Stem
spermatogonia
cells involved in spermatogenesis
 Contain
sustentacular cells
 Sustain
and promote development of sperm
FIGURE 28.5 THE SEMINIFEROUS TUBULES
Figure 28.5a, b
FIGURE 28.5 THE SEMINIFEROUS TUBULES
Figure 28.5c
SPERMATOGENESIS

process of sperm formation
-spermatogonium - primary
spermatocyte
(first meiotic division)
-two secondary spermatocytes (second
meiotic division)
-four spermatids - four spermatozoa

Spermiogenesis: the process of differentiation of
spermatids into spermatozoa
FIGURE 28.8 SPERMIOGENESIS AND
SPERMATOZOON STRUCTURE
Figure 28.8
PATH FOLLOWED BY SPERMATOZOA
1. produced by cells inside the walls of the seminiferous tubules
2. move outside the testis in the epididymis (very long, thin, highly
coiled tube) where they complete maturation in a few days
3. expelled into the vas deferens during ejaculation
4. travel out of scrotum via the inguinal canal into the pelvic cavity to
the posterior side of the urinary bladder
5. joined by secretions via duct from the seminal vesicle
6. pass through prostate gland via ejaculatory duct which opens in
the prostatic urethra (are joined by prostatic secretions)
7. now part of semen pass through the membranous urethra
8. then spongy urethra (joined by secretions of bulbourethral
glands)
9. exit through the urethral meatus
10. then through the urethral orifice to the outside.
FIGURE 28.9 THE EPIDIDYMUS
Figure 28.9
PRODUCTION OF ANDROGENS (MAINLY
TESTOSTERONE)
testosterone is produced by the interstitial cells of Leydig
testosterone production, almost nil before puberty, increases
dramatically at puberty
Some of the functions of testosterone:
- activates anabolic processes
-prior to birth, and after, controls development of male sexual
structures
- controls behavior in both sexes
- supports sperm formation
- controls development of male secondary sex
characteristics:
- widening of shoulders
- increased musculature
- growth of facial hair, pubic and axillary hair
- enlargement of larynx and vocal cords
HORMONES AND MALE REPRODUCTIVE
FUNCTION

FSH (Follicle stimulating hormone)


Targets sustentacular cells to promote
spermatogenesis
LH (leutinizing hormone)

Causes secretion of testosterone and other androgens
GnRH (Gonadotropin releasing hormone)
 Testosterone


Most important androgen
FIGURE 28.12 HORMONAL FEEDBACK AND THE
REGULATION OF THE MALE REPRODUCTIVE
FUNCTION
Figure 28.12
ACCESSORY GLANDS
Seminal Vesicles:
- located on the posterior surface of the urinary bladder
adjacent to the ampulla of the ductus deferens
-elongated, pouch-like hollow organ approximately 5-8cm
long
-proximal end merges with the ductus deferens to form the
ejaculatory duct
-secrete a viscous, whitish-yellow alkaline fluid containing
both fructose and prostaglandins
-fructose nourishes the sperm as they travel through the
female reproductive tract
-prostaglandins promote the widening and slight dilation of
the external orifice of the cervix
Prostate Gland
-compact encapsulated organ that weighs about
20g and is shaped like a walnut, measuring
approximately 2x3x4cm
-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 nutrient for sperm health
-seminalplasmin is an antobiotic that
combats urinary tract infections
-PSA acts as an enzyme to help liquefy
semen following ejaculation
Bulbourethral Glands (Cowper’s gland)
-paired, pea-shaped, located within the urogenital
diaphragm on each side of the
memranous
urethra
-each gland has a short duct that projects into the
base of the penis and enters the spongy
urethra
-secretes a clear, viscous mucin that forms
mucus when mixed with water
-mucin protects the urethra and serves as a
lubricant during sexual intercourse
FIGURE 28.10 THE DUCTUS DEFERENS
AND ACCESSORY GLANDS
Figure 28.10a-e
STRUCTURE OF PENIS

corpus spongiosum around the urethra

two corpora cavernosa on dorsal side

glans penis: enlargement at distal end covered
by prepuce (skin fold)
FIGURE 28.11 THE PENIS
Figure 28.11
Erection: filling the corpora cavernosa and corpus
spongiosum with blood by increased blood flow in
the supply arterioles and decreased drainage
through the venules.
Controlled by parasympathetic system.
Ejaculation: peristaltic contractions in the walls of
ducts (epididymis, vas deferens) propel
spermatozoa and contractions of smooth muscle
fibers in the walls of accessory glands squeeze
out secretions.
Controlled by sympathetic system.
Infertility: < 20,000,000 spermatozoa/ml (normal
20,000,000 - 50,000,000)
COMPARISON OF MALE AND FEMALE
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 females
-androgens in the male
COMPARISON OF MALE AND FEMALE
REPRODUCTIVE SYSTEMS
1.
2.
Primarily nonfunctional and dormant until puberty.
At puberty, external sex characteristics become
more prominent.
1.
2.
3.
4.
5.
Breast development in females
Pubic hair in both sexes
Reproductive organs becomes fully functional
Gametes mature
Gonads secrete sex hormones
COMPARISON OF MALE AND FEMALE
REPRODUCTIVE SYSTEMS
3. Both reproductive systems produce gametes
4. Female typically produces and releases a
single oocyte monthly.
5. Male produces 100,000,000’s of sperm
daily.
-Male gametes are stored for a short
time.
-If they are not expelled from the body within
that period, they are reabsorbed.
Reproductive System Homologous
Female
Organs
Male organ
homologous
Common Functions
Ovary
Testis
Produce gametes and sex
hormones
Clitoris
Glans of Penis
Contains autonomic nervous
system axons that stimulate
arousal and sexual climax
feelings
Labia majora
Scrotum
Protect and cover some
reproductive structures
Vestibular
glands
Bulbourethral
glands
Secretes mucus for lubrication
PERINEUM
1.
2.
3.
4.
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 are formed by an
imaginary horizontal line extending between the
ischial tuberosities of the ossa coxae.
Anterior triangle, called the urogenital triangle,
contains the urethral and vaginal orifices in
females and the base of the penis and the
scrotum in males.
Posterior triangle, called the anal triangle, is the
location of the anus in both sexes.
FEMALE REPRODUCTIVE
SYSTEM
COMPONENTS





ovaries: produce precursors of ova (female
reproductive cells )
Fallopian tubes (uterine tubes, oviducts): carry
female reproductive cells/zygote/mass of
embryonic cells toward uterus
uterus: holds, nourishes and protects developing
embryo/fetus
vagina: tubular structure connecting the uterus to
the outside
vulva (pudendum): external genitalia
FIGURE 28.13 THE FEMALE
REPRODUCTIVE SYSTEM
Figure 28.13
OVARIES
almond sized and shaped, located against
the lateral walls of the upper pelvic cavity
 supporting ligaments:
- suspensory ligament: between ovary
and lateral wall of pelvic cavity
- ovarian ligament: between ovary and
fundus of uterus
- part of the sheet-like broad ligament
(mesovarium)

FIGURE 28.14 THE OVARIES AND THEIR
RELATIONSHIPS TO THE UTERINE TUBE AND
UTERUS
Figure 28.14a, b
OVARIAN STRUCTURE




covered by germinal epithelium: layer of simple cuboidal epithelium
surrounded by fibrous tunica albuginea (same as testes)
two regions:
- outer cortex
- inner medulla
- ovarian follicles are found in the cortex:
- follicle: central cell called oocyte surrounded by supporting granulosa cells
- types of follicles (based on developmental stage):
- primordial: primary oocyte surrounded by one layer of
squamous cells
- primary: primary oocyte surrounded by one layer of cuboidal
cells
- secondary: primary oocyte surrounded by two or more
layers of cells
- Graafian: very large with fluid filled space in the center;
secondary oocyte pushed at the edge
OOGENESIS
Prior to birth
- oogonia multiply mitotically (about 3/4 million)
- oogonia - become primary oocytes - start first
meiotic div., stop at prophase
Primordial follicles - Primary follicles
Birth
- female is born with ~ 3/4million primary follicles
containing primary oocytes that have started the
first meiotic division but have stopped at the
prophase
OOGENESIS
Puberty
- each month ~24 follicles get activated, one survives (most
follicles die by atresia); the primary oocyte completes the
first meiotic division
- primary oocyte - secondary oocyte (and tiny, first polar body) second meiotic div. starts but stops at metaphase
Primary follicle - Secondary follicle - Graafian follicle
- Graafian follicle ruptures at ovulation releasing the
secondary oocyte in the pelvic cavity; the secondary oocyte
is directed inside the Fallopian tube by the fimbriae and
moves toward the uterus.
OOGENESIS
Possible outcomes:
- secondary oocyte is contacted by spermatozoa: the oocyte is
activated and completes the second meiotic division
forming an ovum (and a tiny, second polar body); the ovum
and one of the spermatozoa unite (fertilization) to form the
zygote (first cell of the new organism). The zygote starts to
divide right away and by the time it reaches the uterine
cavity it is a mass of cells that undergo implantation (attach
to the uterine wall)
- secondary oocyte does not come in contact with
spermatozoa: it will disintegrate on its way to the uterus
FALLOPIAN TUBES (UTERINE TUBES,
OVIDUCTS)
- have fimbriae (finger-like) surrounding funnel
shaped opening next to the ovary
- attach to the fundus of the uterus
UTERUS

Muscular organ
 Mechanical
protection
 Nutritional support
 Waste removal for the developing embryo and fetus

Supported by the broad ligament and 3 pairs of
suspensory ligaments
UTERUS
Parts:
- fundus (bottom): back (deep, proximal) part
- corpus (body): central part
- cervix (neck): end part that attaches to the vagina
Wall structure:
- perimetrium: thin outer layer
- myometrium: thick, middle muscular layer
- endometrium: thin inner lining
- has two layers:
- endometrium basalis: permanent, against the
myometrium
- endometrium functionalis: shed during
menstruation; faces the uterine cavity
FIGURE 28.19 THE UTERINE WALL
Figure 28.19b
UTERUS
Supporting ligaments:
- part of sheet-like broad ligament (mesometrium)
- round ligament
- cardinal ligaments: lateral, main support
- utero-sacral ligament
Blood supply:
- uterine arteries branch from the internal iliac arteries
- the endometrium basalis is penetrated by straight arterioles
- from the straight arterioles branch spiral arterioles that enter
the endometrium functionalis; the spiral arterioles break
during menstruation causing bleeding
HORMONAL FACTORS THAT CONTROL THE
MENSTRUAL CYCLE:
Follicle stimulating hormone (FSH):
-starting at puberty, activates a couple of dozens of primary
follicles each month causing them to continue development
Luteinizing hormone (LH):
-triggers ovulation and, following that, it maintains the corpus
luteum
Progesterone:
- when at high levels in the blood, together with estrogen,
inhibits the release of gonadotropic hormones by the
pituitary gland and prevents the start of a new menstrual
cycle
- maintains the endometrium functionalis and prevents its
shedding
HORMONAL FACTORS THAT CONTROL THE
MENSTRUAL CYCLE:
Estrogen:
- promotes tissue growth
- activates osteoblasts
- promotes the development of the female secondary sex
characteristics:
- distribution of adipose tissue on the body with:
- enlargement of the breasts
- widening of the hips
- distribution of hair: axillary and pubic hair
- when at high levels in the blood, together with progesterone,
inhibits the release of gonadotropic hormones by the pituitary
gland and prevents the start of a new menstrual cycle
FIGURE 28.25 THE HORMONAL
REGULATION OF OVARIAN ACTIVITY
Figure 28.25
MENSTRUAL CYCLE:
CONSISTS OF TWO CYCLES
uterine cycle:
- a series of monthly changes in the wall of the uterus of a
nonpregnant female that prepare the endometrium functionalis
for implantation
- if there is no implantation, the shedding of the endometrium
functionalis
ovarian cycle:
- monthly activation and the continued development into
secondary follicles of about two dozens ovarian follicles, usually
with only one surviving, completing development into a
Graafian follicle and then rupturing releasing a secondary
oocyte in the pelvic cavity.
FIGURE 28.26 THE HORMONAL REGULATION OF THE
FEMALE REPRODUCTIVE CYCLE
Figure 28.26a-c
FIGURE 28.26 THE HORMONAL REGULATION OF THE
FEMALE REPRODUCTIVE CYCLE
PLAY
Animation: Regulation of the Female Reproductive Cycle
Figure 28.26d-f
PHASES OF THE MENSTRUAL CYCLE
Menstrual phase:
- last about 5 days
-
uterine cycle:
- small patches of the endometrium functionalis get
sloughed off from the uterine wall, one a time, with spiral
arterioles rupturing and causing bleeding.
- By the end of the fifth day only a thin, smooth layer of
endometrium, the endometrium basalis, is left.
-
ovarian cycle:
- at this time the levels of progesterone and estrogen in the
blood
are low allowing the pituitary to release follicle
stimulating
hormone (FSH).
- The FSH activates over twenty four primary follicles in the ovaries
causing them to continue development. All but one follicle fail to
complete development, undergo atresia, with the surviving follicle
acquiring additional layers of supporting cells thus becoming a
secondary follicle.
Preovulatory (postmenstrual) phase:
- variable in length; lasts from day 5 to about day 13
-
uterine cycle:
- a new endometrium functionalis starts to grow out of the basalis
layer.
-
ovarian cycle:
- the surviving follicle becomes a Graafian follicle.
- The primary oocyte, within the follicle, completes the first meiotic
division and produces two daughter cells, a tiny first polar body,
which will be lost and a large secondary oocyte.
- The secondary oocyte starts the second meiotic division but
stops
at metaphase.
- Toward the end of this period there is a sudden increase in the
production of luteinizing hormone (LH) by the pituitary
gland
causing the Graafian follicle to complete its maturation and to rupture.
Ovulation:
- occurs around day 14.
-
The Graafian follicle ruptures releasing the
secondary oocyte in the pelvic cavity.
-
The secondary oocyte, in most instances, is
directed inside the Fallopian tube (with help
from the fimbriae) and starts traveling
toward the uterus.
Postovulatory (premenstrual) phase:
- ovarian cycle:
- under the influence of the luteinizing hormone (LH) the
mass of tissue of the former Graafian follicle that
remained in the ovary is transformed into a yellow
body called the corpus luteum.
- The corpus luteum starts producing large amounts of
progesterone and estrogen causing their blood levels
to increase dramatically.
-
uterine cycle:
- under the influence of progesterone the
endometrium functionalis layer continues its
preparation for implantation:
- becomes thicker and accumulates large deposits of
glycogen while numerous spiral arterioles grow into
it from the endometrium basalis layer.
Postovulatory (premenstrual) phase:
-
if the secondary oocyte, while traveling toward the uterus, is
met and contacted by spermatozoa then it will complete the
second meiotic division and will form a second polar body
and an ovum (egg).
-
Following fertilization the egg will form a zygote (first cell of
the new organism), the zygote will start dividing mitotically
right away and upon reaching the uterus the mass of cells
will attach itself to the endometrium functionalis layer that
lines the uterine cavity (implantation).
Postovulatory (premenstrual) phase:
-
At the site of contact between the embryonic mass and the
uterine wall a new structure, called the placenta, will start
growing immediately.
-
The placenta will start producing human chorionic
gonadotropic hormone (HCGH) which mimics in its effects
the luteinizing hormone.
-
HCGH will maintain the corpus luteum functional allowing it
to continue to produce large amounts of progesterone and
estrogen for several months.
Postovulatory (premenstrual) phase cont…:
-
The high levels of progesterone and estrogen in the blood
will inhibit the pituitary gland preventing it from releasing
gonadotropic hormones (FSH and LH) thus the production
and following that the blood level of LH will decrease.
-
However, since the HCGH is assuming the function of LH
the corpus luteum will continue to function producing large
amounts of progesterone and estrogen.
-
The high levels of progesterone in the blood will maintain
the endometrium functionalis layer in place preventing its
shedding.
Postovulatory (premenstrual) phase:
-
The lack of FSH production due to the inhibition of the
pituitary prevents the start of a new ovarian cycle.
-
The high levels of progesterone help maintain the
endometrium functionalis layer thus preventing the start of
a new uterine cycle.
-
Thus, the high blood levels of progesterone and estrogen
prevent the start of a new menstrual cycle during
pregnancy.
-
The corpus luteum stops functioning during the second half
of pregnancy, at that time the production of estrogen and
progesterone is taken over by the placenta.
Postovulatory (premenstrual) phase cont…:
-
if the secondary oocyte is not met by spermatozoa it will
soon disintegrate while traveling toward the uterus.
-
The high levels of progesterone and estrogen in the blood
will inhibit the pituitary gland and prevent the release of LH.
-
Without LH the corpus luteum can not continue to function
and it starts to degenerate.
-
It stops producing the progesterone and estrogen, changes
to a whitish color, it is now called the corpus albicans, and
shrinks to a small scar that is left in the mass of the ovary.
Postovulatory (premenstrual) phase cont…:
-
The levels of progesterone and estrogen in the blood
decline with the following consequences:
- the endometrium functionalis layer can not be
sustained, due to lack of progesterone, and starts
to
shed one piece at a time: a new uterine cycle begins.
- the low blood levels of estrogen and progesterone
allow the pituitary to become disinhibited and
to
start releasing FSH.
- The FSH activates a couple of dozens of ovarian
follicle thus starting a new ovarian cycle.
- this way a new menstrual cycle begins.
FIGURE 28.20 THE UTERINE CYCLE
Figure 28.20
MENSTRUAL CYCLE PROBLEMS
- climacteric : period of irregular menstrual
cycling that precedes menopause.
- menopause: complete cessation of menstrual
cycles; associated with aging.
- amenorrhea: lack of menstrual cycles; often
caused by insufficient adipose tissue in the
body resulting from starvation or excessive
physical exercise.
VAGINA
-
tubular structure that connects the uterus to the
outside.
-
Attaches to the cervix of the uterus at the proximal
end.
-
Forms an attachment fold called the fornix.
-
The vaginal mucosa has folds (rugae).
-
The mucosa stores significant amounts of glycogen
which, following processing, produces lactic acid.
VAGINA CONT…
-
The lactic acid makes the vaginal
environment acidic this way preventing the
growth of pathogens.
-
The acidic environment is inhospitable,
however, to the spermatozoa and has to be
neutralized by the alkaline semen.
-
The distal end of the vagina opens, through
the vaginal orifice in the vestibule of the
vulva (pudendum).
VULVA (PUDENDUM): EXTERNAL FEMALE
GENITALIA
Structure:
mons pubis (mons veneris):
- pad of adipose tissue located anterior to the symphysis pubis.
- two pairs of folds:
- labia majora: lateral, large, filled with adipose tissue, covered with
hair
- labia minora: medial, thin, hairless
clitoris:
- small, penis-like structure containing two corpora cavernosa, covered
by a prepuce-like skin fold.
- Located at the anterior end of the labia minora.
- The urethra does not pass through it and it has no corpus
spongiosum.
vestibule:
- space bordered by the labia minora; its walls contain glands that produce
lubricating secretions:
- many small, lesser vestibular glands
- a couple of large, greater vestibular glands (Bartholin’s
glands)
FIGURE 28.22 THE FEMALE EXTERNAL
GENITALIA
Figure 28.22
MAMMARY GLANDS
-
located in the pectoral region superficial to the
pectoralis major muscles.
-
supported by strands of connective tissue called
suspensory ligaments (Cooper’s ligaments;
‘Cooper’s droop’: sagging of the breasts due to
stretching of the Cooper’s ligaments.
-
made of 15 - 20 functional masses of milk
producing tissue (lobes) separated by masses of
adipose tissue.
MAMMARY GLANDS CONT…
- inside the lobes there are lobules that
contain grape-like masses of secretory cells
called alveoli which produce milk.
- the milk flows to wide ducts, lactiferous ducts
(sinuses), where it is stored before release.
- the lactiferous ducts open through the papilla
(nipple) to the outside; the papilla is
surrounded by the areola, a dark, pigmented
area.
FIGURE 28.23 THE MAMMARY GLANDS
Figure 28.23a-c
LACTATION
production and release of milk
- milk production is controlled by the
hormone
prolactin
- milk release from the lactiferous ducts is
controlled by the hormone oxytocin;
- when there is tactile stimulation of the breast
by the infant trying to feed, the stimulation
causes the release of oxytocin from the
neurohypophysis;
-the oxytocin travels via the blood the walls of the
lactiferous ducts causing their
constriction thus
expelling the milk (milk let down) from the breast.