Transcript Reproductive System - North Seattle College

Reproductive System
Cell Cycle
• Produces gametes by meiosis
Cell Cycle
• Meiosis reduces the number of
chromosomes in half
Cell Cycle
• Gametes have only 23 chromosomes
Homologous Chromosomes
• 2 chromosomes that make up a
chromosome pair in cells
Homologous Chromosomes
• Contain similar genes
Homologous Chromosomes
• The exception is the sex chromosomes
Homologous Chromosomes
• The female contains two X chromosomes
Homologous Chromosomes
• The male has an X and a Y chromosome
Homologous Chromosomes
• The other 22 pairs of chromosomes are
called autosomes
Diploid Cell
• A cell with a full set of chromosomes
Haploid Cell
• One with only one chromosome from each
pair
Haploid Cell
• Gametes are the only haploid cells
Haploid Cell
• Eggs and spermatoza
Male Reproductive System
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Testes
A system of ducts
Several supporting structures
Penis
Scrotum
• Cutaneous outpouching of the abdomen
that supports the testes
Scrotum
• Internally a vertical septum divides it into
two sacs, each containing a single testis
Testes
• Paired oval-shaped glands in the scrotum
Testes
• Contain seminiferous tubules ( in which
sperm cells are made)
Testes
• Sertoli Cells - Embedded among the
spermatogenic cells in the tubules
Sertoli Cells
• Nourish spermatocytes, spermatids, and
spermatozoa
Sertoli Cells
• Control movements of spermatogenic cells
Sertoli Cells
• Controls the release of spermatozoa into
the lumen of the seminiferous tubule
Sertoli Cells
• Secretes fluid for sperm transport and the
hormone inhibin
Sertoli Cells
• Inhibin decreases FSH when the rate of
spermatogenesis is too high
Testes
• Leydig cells – found in the spaces
between adjacent seminiferous tubules
secrete testosterone
Spermatogenesis
• Process by which seminiferous tubules of
the testes produce sperm
Spermatogenesis
• Spermatogonia – stem cells
Spermatogenesis
• Spermatogonia undergo mitosis to
produce future stem cells and primary
spermatocytes
Spermatogenesis
• Diploid primary spermatocytes undergo
meiosis I forming haploid secondary
spermatocytes
Spermatogenesis
• Meiosis II results in haploid spermatids
Spermatogenesis
• Spermiogenesis – maturation of the
spermatids into spermatozoa
Mature Sperm
• Consist of a head, midpiece, and tail
Mature Sperm
• The head contains a specialized lysosome
called an acrosome
Mature Sperm
• The acrosome has an enzyme that helps
penetrate the egg
Mature Sperm
• The midpiece is rich in mitochondria for
ATP production
Mature Sperm
• ATP is essential for the motility of flagellum
Mature Sperm
• They are produced at the rate of about
100-300 million per day
Mature Sperm
• Have a life expectancy of 48 hours within
the female reproductive tract
Hormonal Control of
Spermatogenesis
• At puberty Gonadotropin releasing
hormone increases, which stimulates the
A.P. secretion of FSH and LH
Hormonal Control of
Spermatogenesis
• FSH initiates spermatogenesis
Hormonal Control of
Spermatogenesis
• LH assists spermatogenesis and
stimulates the production of testosterone
by the Leydig cells
Testosterone
• Controls the growth, development,
functioning, and maintenance of sex
organs
Testosterone
• Stimulates bone growth, protein
anabolism, increases in muscle size, and
sperm maturation
Testosterone
• It increases libido and stimulates the
development of secondary sex
characteristics
Testosterone
• It reduces LH secretion, which decreases
testosterone production
Secondary Male Sex
Characteristics
• Wide shoulders
Secondary Male Sex
Characteristics
• Narrow hips
Secondary Male Sex
Characteristics
• Male hair patters
Secondary Male Sex
Characteristics
• Thick and oily skin
Secondary Male Sex
Characteristics
• Enlarged larynx with a deeper voice
Ducts
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The duct system of the testes includes the
Seminiferous tubules
Straight tubules
Rete Testis
Epididymis
Ductus Deferens
Ejaculatory Duct
Urethra
Epididymis
• Comma-shaped organ that lies along the
posterior border of the testis
Epididymis
• Sperm are transported out of the testes
through the ductus epididymis
Ductus Epididymis
• Lined by stereocilia
Ductus Epididymis
• Site of sperm maturation and storage
Ductus Epididymis
• Sperm may remain in storage here for at
least a month
Vas Deferens
• Stores sperm and propels them toward the
urethra during ejaculation
Ejaculatory Ducts
• Formed by the union of the ducts from the
seminal vesicles and ducti deferens
Ejaculatory Ducts
• Function to eject spermatozoa into the
prostatic urethra
Male urethra
• Serves as a passageway for semen and
urine
Seminal Vesicles
• Secretes a viscous alkaline fluid that
contains fructose that nourish and promote
the fertilizing capability of sperm
Seminal Vesicles
• The alkaline fluid helps neutralize acid in
the male urethra and female reproductive
tract
Seminal Vesicles
• The fructose is for ATP production by
sperm
Prostate Gland
• Secretes a milky, slightly acidic fluid
Bulbourethral Glands
• Secretes mucus for lubrication and an
alkaline substance that neutralizes acid
Semen
• Average volume 2.75 ml
Semen
• Contains 50-150 million spermatozoa/ml
Semen
• The average sperm count has declined
from 113 million/ml to 66 million/ml over
the past 44 years
Semen
• May be due to estrogens in meat,
marijuana, environmental toxins, alcohol,
and lead exposure
Penis
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Male organ of copulation that consists of
a
Root
Body
Glans penis
foreskin
Penis
• Spongy tissue in shaft composed of
1. Two dorsal corpora cavernosa
2. Ventral corpos spongiosum
Penis
• Arterioles (which are normally constricted)
supply blood to blood sinuses
Penis
• The blood sinuses become filled with
blood during erection
Erection
• Mediated by a parasympathetic reflex
Erection
• Neurons and vascular endothelial cells
release nitric oxide which leads to
arteriolar smooth muscle relaxation
Erection
• This vasodilation increases blood flow into
the penis
Ejaculation
• Propulsion of semen from the urethra to
the exterior is a sympathetic reflex
Female Reproductive System
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Ovaries
Uterine tubes
Uterus
Vagina
Vulva
Mammary Glands
Ovaries
• Paired glands that are homologous to the
testes
Ovaries
• Located in the upper pelvic cavity on either
side of the uterus
Ovarian Cortex
• Contain ovarian follicles and consists of
oocytes in various stages of development
Primordial follicles
• Contain the primary oocyte surrounded by
a single layer of flattened epithelial cells
Primordial follicles
• Contain 46 chromosomes stuck in
prophase of meiosis 1
Primordial follicles
• A woman is born with 2 million primordial
follicles
Primordial follicles
• During childhood, most undergo atresia
Primordial follicles
• By puberty, only 400,000 are left
Primordial follicles
• Each month, about 20 primordial follicles
mature into primary follicles
Primary follicles
• Primary oocyte surrounded by one to
several layers of cuboidal epithelial cells
that make estrogen
Primary follicles
• These epithelial cells are called granulosa
cells
Primary follicles
• In between the oocyte and granulosa cells
is a glycoprotein called the zona pelucida
Primary follicles
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Outside the granulosa cells are two
layers of connective tissue called
1. Theca externa
2. Theca interna
Primary follicles
• Many primaries undergo atresia
Primary follicles
• Some become secondary follicles
Secondary Follicles
• Have a fluid filled antrum
Secondary follicles
• As the menstrual cycle progresses toward
midcycle all of the secondaries undergo
atresia except one
Secondary follicles
• One follicle will become the dominant
follicle- the Graafian follicle
Graafian Follicle
• The primary oocyte will complete meiosis I
and go through part of meiosis II, but
pause at metaphase II
Graafian Follicle
• It’s now called the secondary oocyte
Graafian Follicle
• The follicle expel the secondary oocyte by
a process called ovulation
Immature ovum
• Surrounding it is the zona pelucida and a
layer of follicular cells called the corona
radiata
Corpus luteum
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Contains the remnants of an ovulated
follicle and produces
Progesterone
Estrogen
Relaxin
Inhibin
Corpus luteum
• It eventually degenerates into a corpus
albicans
Oogenesis
• Occurs in the ovaries
Oogenesis
• It results in the formation of a single
haploid secondary oocyte
Oogenesis
• Meisosis II is not complete until fertilization
Ovarian Medulla
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Contains
Blood vessels
Lymphatics
Nerves
Uterine Tube
• Transport ova from the ovaries to the
uterus
Uterine Tube
• Normal sites of fertilizaiton
Uterine Tube
• Fimbriae – are projections of the tubes
that help capture the ovulated immature
ovum
Uterine Tube
• The fallopian tube is the usually the site of
fertilization
Uterine Tube
• Ciliated cells and peristaltic contractions
help move a secondary oocyte toward the
uterus
Uterus
• An organ the size and shape of an
inverted pear
Uterus
• Functions in the transport of spermatozoa,
menstruation, implantation of a fertilized
ovum, development of a fetus during
pregnancy, and labor
Uterus
• Cervix – connects the vaginal cavity to the
uterine cavity
Uterus
• Cervix – firm unless it is softened by
relaxin during labor and delivery
Histology of the Uterus
1. Perimetrium
2. Myometrium
3. Endometrium
Perimetrium
• Part of the visceral peritoneum
Myometrium
• Consists of three muscle layers and has
oxytocin receptors
Endometrium
• Divided into the
1. Stratum Functionalis
2. Stratum Basalis
Endometrium
• Spiral arteries supply the endometrium
Cervix
• Secretory cells of the cervix produce a
cervical mucus
Cervix
• At mid cycle the mucus is thin and
receptive to sperm
Cervix
• During most of the menstrual cycle the
mucus is thick
Vagina
• 10 cm in the adult
Vagina
• Functions as a passageway for
spermatozoa and the menstrual flow
Vagina
• It is acidic in order to inhibit
microorganisms and sperm
Vagina
• The vaginal orifice in virgins is partially
covered by the hymen
Vulva
• External genitalia of the female
Vulva
• It consists of
1. Mons pubs – rounded fatty eminence
overlying the pubic symphysis
Vulva
2. Labia majora – covered with hair
Vulva
3. Labia minora – thinner folds that are
devoid of hair, they atrophy after
menopause
Vulva
4. Clitoris – homologous to the penis
Vulva
5. Vestibule – cleft between labia minora
where vaginal orifice opens to the outside
Vulva
6. Vaginal orifice
Vulva
7. Urethral orifices – between the clitoris and
the vaginal orifice
Vulva
8. Hymen
Mammary Glands
• Milk producing glands that lie over the
pectoralis major and serratus anterior
muscle
Mammary Glands
• Milk secreting cells (alveoli) are clustered
in small compartments (lobules) within the
breasts
Mammary Glands
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Alveoli
Mammary ducts
Lactiferous ducts
Lactiferous sinuses
Nipple
Mammary Glands
• Function to synthesize milk and secretion
and ejection of milk (lactation)
Mammary Glands
• Areola is the pigmented skin that
surrounds the nipple
Mammary Glands
• Develop at puberty under the stimulation
of rising estrogen and progesterone levels
Phases of the Female
Reproductive Cycle
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Menstrual cycle
Preovulatory phase
Ovulation
Postovulatory phase
Menstrual Cycle
• First five days of cycle
Menstrual Cycle
• About 20 small follicles in each ovary
begin to develop
Menstrual Cycle
• Stratum functionalis layer of the
endometrium is shed discharging blood,
tissue fluid, mucus, and epithelial cells
Menstrual Cycle
• It is shed due to declining progesterone at
the end of the previous cycle
Preovulatory phase
• Between menstruation and ovulation
Preovulatory phase
• Lasting from days 6-13 in a 28 day cycle
Preovulatory phase
• Primary follicles develop into secondary
follicles
Preovulatory phase
• A single secondary follicle develops into a
Graafian or mature follicle
Preovulatory phase
• Maturing follicles secrete estrogen
Preovulatory phase
• The mature follicle continues to increase
its estrogen production due to increasing
levels of LH
Preovulatory phase
• Estrogen stimulates endometrial repair; a
new stratum functionalis is formed
Ovulation
• Rupture of the Graafian or mature follicle
with release of the secondary oocyte into
the pelvic cavity
Ovulatation
• LH transforms the ruptured follicle into the
corpus luteum
Ovulation
• Occurs on day 14
Ovulation
• The high levels of estrogen during the last
part of the preovulatory phase exerts a
positive feedback on LH and GnRH to
cause ovulation
Ovulation
• GnRH promotes release of FSH and LH
Ovulation
• LH surge brings about the ovulation
Ovulation
• Increased body temperature due to
progesterone, which increases just prior to
ovulation
Ovulation
• Clear cervical mucus due to high estrogen
Ovulation
• Corpus luteum secretes estrogens and
progesterone due to LH
Postovulatory phase
• Days 15-28
Postovulatory phase
• Time between ovulation and the onset of
the next menstrual period
Postovulatory phase
• Estrogen and progesterone are secreted
in large quantities by the corpus luteum
Postovulatory phase
• If fertilization and implantatin do not occur,
estrogen and progesterone secreted by
the corpus luteum inhibit LH
Postovulatory phase
• So Corpus luteum loses its support
Postovulatory phase
• The copus luteum degenerates and
becomes the corpus albicans
Postovulatory phase
• The decreased levels of estrogen and
progesterone initiatates another menstrual
phase
Postovulatory phase
• Because estrogen and progesterone
levels drop, there is less negative
feedback on the Hyp. and A.P.
Postovulatory phase
• FSH and LH begin to rise a bit at the end
of the cycle, causing another round of
follicular development (about 20)
Postovulatory phase
• If fertilization and implantation do occur,
the corpus luteum is maintained until the
placenta takes over
Postovulatory phase
• Corpus luteum is maintained by human
chorionic gonadotropin (hCG) from the
developing placenta
Postovulatory phase
• The corpus luteum secretes estrogens and
progesterones to support pregnancy and
breast development for lactation
Postovulatory phase
• Once the placenta begins secreting
estrogen and progesterone, the role of
corpus luteum becomes minor
Postovulatory phase
• Endometrium thickens in anticipation of
implantation