Reproductive System Reproductive System
Reproductive SystemReproductive System
Cell CycleCell Cycle
• Produces gametes by meiosis
Cell CycleCell Cycle
• Meiosis reduces the number of chromosomes in half
Cell CycleCell Cycle
• Gametes have only 23 chromosomes
Homologous ChromosomesHomologous Chromosomes
• 2 chromosomes that make up a chromosome pair in cells
Homologous ChromosomesHomologous Chromosomes
• Contain similar genes
Homologous ChromosomesHomologous Chromosomes
• The exception is the sex chromosomes
Homologous ChromosomesHomologous Chromosomes
• The female contains two X chromosomes
Homologous ChromosomesHomologous Chromosomes
• The male has an X and a Y chromosome
Homologous ChromosomesHomologous Chromosomes
• The other 22 pairs of chromosomes are called autosomes
Diploid CellDiploid Cell
• A cell with a full set of chromosomes
Haploid CellHaploid Cell
• One with only one chromosome from each pair
Haploid CellHaploid Cell
• Gametes are the only haploid cells
Haploid CellHaploid Cell
• Eggs and spermatoza
Male Reproductive SystemMale Reproductive System
• Testes• A system of ducts• Several supporting structures• Penis
ScrotumScrotum
• Cutaneous outpouching of the abdomen that supports the testes
ScrotumScrotum
• Internally a vertical septum divides it into two sacs, each containing a single testis
TestesTestes
• Paired oval-shaped glands in the scrotum
TestesTestes
• Contain seminiferous tubules ( in which sperm cells are made)
TestesTestes
• Sertoli Cells - Embedded among the spermatogenic cells in the tubules
Sertoli CellsSertoli Cells
• Nourish spermatocytes, spermatids, and spermatozoa
Sertoli CellsSertoli Cells
• Control movements of spermatogenic cells
Sertoli CellsSertoli Cells
• Controls the release of spermatozoa into the lumen of the seminiferous tubule
Sertoli CellsSertoli Cells
• Secretes fluid for sperm transport and the hormone inhibin
Sertoli CellsSertoli Cells
• Inhibin decreases FSH when the rate of spermatogenesis is too high
TestesTestes
• Leydig cells – found in the spaces between adjacent seminiferous tubules secrete testosterone
SpermatogenesisSpermatogenesis
• Process by which seminiferous tubules of the testes produce sperm
SpermatogenesisSpermatogenesis
• Spermatogonia – stem cells
SpermatogenesisSpermatogenesis
• Spermatogonia undergo mitosis to produce future stem cells and primary spermatocytes
SpermatogenesisSpermatogenesis
• Diploid primary spermatocytes undergo meiosis I forming haploid secondary spermatocytes
SpermatogenesisSpermatogenesis
• Meiosis II results in haploid spermatids
SpermatogenesisSpermatogenesis
• Spermiogenesis – maturation of the spermatids into spermatozoa
Mature SpermMature Sperm
• Consist of a head, midpiece, and tail
Mature SpermMature Sperm
• The head contains a specialized lysosome called an acrosome
Mature SpermMature Sperm
• The acrosome has an enzyme that helps penetrate the egg
Mature SpermMature Sperm
• The midpiece is rich in mitochondria for ATP production
Mature SpermMature Sperm
• ATP is essential for the motility of flagellum
Mature SpermMature Sperm
• They are produced at the rate of about 100-300 million per day
Mature SpermMature Sperm
• Have a life expectancy of 48 hours within the female reproductive tract
Hormonal Control of Hormonal Control of SpermatogenesisSpermatogenesis
• At puberty Gonadotropin releasing hormone increases, which stimulates the A.P. secretion of FSH and LH
Hormonal Control of Hormonal Control of SpermatogenesisSpermatogenesis
• FSH initiates spermatogenesis
Hormonal Control of Hormonal Control of SpermatogenesisSpermatogenesis
• LH assists spermatogenesis and stimulates the production of testosterone by the Leydig cells
TestosteroneTestosterone
• Controls the growth, development, functioning, and maintenance of sex organs
TestosteroneTestosterone
• Stimulates bone growth, protein anabolism, increases in muscle size, and sperm maturation
TestosteroneTestosterone
• It increases libido and stimulates the development of secondary sex characteristics
TestosteroneTestosterone
• It reduces LH secretion, which decreases testosterone production
Secondary Male Sex Secondary Male Sex CharacteristicsCharacteristics
• Wide shoulders
Secondary Male Sex Secondary Male Sex CharacteristicsCharacteristics
• Narrow hips
Secondary Male Sex Secondary Male Sex CharacteristicsCharacteristics
• Male hair patters
Secondary Male Sex Secondary Male Sex CharacteristicsCharacteristics
• Thick and oily skin
Secondary Male Sex Secondary Male Sex CharacteristicsCharacteristics
• Enlarged larynx with a deeper voice
DuctsDucts
• The duct system of the testes includes the 1. Seminiferous tubules2. Straight tubules3. Rete Testis4. Epididymis5. Ductus Deferens6. Ejaculatory Duct7. Urethra
EpididymisEpididymis
• Comma-shaped organ that lies along the posterior border of the testis
EpididymisEpididymis
• Sperm are transported out of the testes through the ductus epididymis
Ductus EpididymisDuctus Epididymis
• Lined by stereocilia
Ductus EpididymisDuctus Epididymis
• Site of sperm maturation and storage
Ductus EpididymisDuctus Epididymis
• Sperm may remain in storage here for at least a month
Vas DeferensVas Deferens
• Stores sperm and propels them toward the urethra during ejaculation
Ejaculatory DuctsEjaculatory Ducts
• Formed by the union of the ducts from the seminal vesicles and ducti deferens
Ejaculatory DuctsEjaculatory Ducts
• Function to eject spermatozoa into the prostatic urethra
Male urethraMale urethra
• Serves as a passageway for semen and urine
Seminal VesiclesSeminal Vesicles
• Secretes a viscous alkaline fluid that contains fructose that nourish and promote the fertilizing capability of sperm
Seminal VesiclesSeminal Vesicles
• The alkaline fluid helps neutralize acid in the male urethra and female reproductive tract
Seminal VesiclesSeminal Vesicles
• The fructose is for ATP production by sperm
Prostate GlandProstate Gland
• Secretes a milky, slightly acidic fluid
Bulbourethral GlandsBulbourethral Glands
• Secretes mucus for lubrication and an alkaline substance that neutralizes acid
SemenSemen
• Average volume 2.75 ml
SemenSemen
• Contains 50-150 million spermatozoa/ml
SemenSemen
• The average sperm count has declined from 113 million/ml to 66 million/ml over the past 44 years
SemenSemen
• May be due to estrogens in meat, marijuana, environmental toxins, alcohol, and lead exposure
PenisPenis
• Male organ of copulation that consists of a
1. Root2. Body3. Glans penis4. foreskin
PenisPenis
• Spongy tissue in shaft composed of 1. Two dorsal corpora cavernosa2. Ventral corpos spongiosum
PenisPenis
• Arterioles (which are normally constricted) supply blood to blood sinuses
PenisPenis
• The blood sinuses become filled with blood during erection
ErectionErection
• Mediated by a parasympathetic reflex
ErectionErection
• Neurons and vascular endothelial cells release nitric oxide which leads to arteriolar smooth muscle relaxation
ErectionErection
• This vasodilation increases blood flow into the penis
EjaculationEjaculation
• Propulsion of semen from the urethra to the exterior is a sympathetic reflex
Female Reproductive SystemFemale Reproductive System
• Ovaries• Uterine tubes• Uterus• Vagina• Vulva• Mammary Glands
OvariesOvaries
• Paired glands that are homologous to the testes
OvariesOvaries
• Located in the upper pelvic cavity on either side of the uterus
Ovarian CortexOvarian Cortex
• Contain ovarian follicles and consists of oocytes in various stages of development
Primordial folliclesPrimordial follicles
• Contain the primary oocyte surrounded by a single layer of flattened epithelial cells
Primordial folliclesPrimordial follicles
• Contain 46 chromosomes stuck in prophase of meiosis 1
Primordial folliclesPrimordial follicles
• A woman is born with 2 million primordial follicles
Primordial folliclesPrimordial follicles
• During childhood, most undergo atresia
Primordial folliclesPrimordial follicles
• By puberty, only 400,000 are left
Primordial folliclesPrimordial follicles
• Each month, about 20 primordial follicles mature into primary follicles
Primary folliclesPrimary follicles
• Primary oocyte surrounded by one to several layers of cuboidal epithelial cells that make estrogen
Primary folliclesPrimary follicles
• These epithelial cells are called granulosa cells
Primary folliclesPrimary follicles
• In between the oocyte and granulosa cells is a glycoprotein called the zona pelucida
Primary folliclesPrimary follicles
• Outside the granulosa cells are two layers of connective tissue called
1. Theca externa2. Theca interna
Primary folliclesPrimary follicles
• Many primaries undergo atresia
Primary folliclesPrimary follicles
• Some become secondary follicles
Secondary FolliclesSecondary Follicles
• Have a fluid filled antrum
Secondary folliclesSecondary follicles
• As the menstrual cycle progresses toward midcycle all of the secondaries undergo atresia except one
Secondary folliclesSecondary follicles
• One follicle will become the dominant follicle- the Graafian follicle
Graafian FollicleGraafian Follicle
• The primary oocyte will complete meiosis I and go through part of meiosis II, but pause at metaphase II
Graafian FollicleGraafian Follicle
• It’s now called the secondary oocyte
Graafian FollicleGraafian Follicle
• The follicle expel the secondary oocyte by a process called ovulation
Immature ovumImmature ovum
• Surrounding it is the zona pelucida and a layer of follicular cells called the corona radiata
Corpus luteumCorpus luteum
• Contains the remnants of an ovulated follicle and produces
1. Progesterone2. Estrogen3. Relaxin4. Inhibin
Corpus luteumCorpus luteum
• It eventually degenerates into a corpus albicans
OogenesisOogenesis
• Occurs in the ovaries
OogenesisOogenesis
• It results in the formation of a single haploid secondary oocyte
OogenesisOogenesis
• Meisosis II is not complete until fertilization
Ovarian MedullaOvarian Medulla
• Contains1. Blood vessels2. Lymphatics3. Nerves
Uterine TubeUterine Tube
• Transport ova from the ovaries to the uterus
Uterine TubeUterine Tube
• Normal sites of fertilizaiton
Uterine TubeUterine Tube
• Fimbriae – are projections of the tubes that help capture the ovulated immature ovum
Uterine TubeUterine Tube
• The fallopian tube is the usually the site of fertilization
Uterine TubeUterine Tube
• Ciliated cells and peristaltic contractions help move a secondary oocyte toward the uterus
UterusUterus
• An organ the size and shape of an inverted pear
UterusUterus
• Functions in the transport of spermatozoa, menstruation, implantation of a fertilized ovum, development of a fetus during pregnancy, and labor
UterusUterus
• Cervix – connects the vaginal cavity to the uterine cavity
UterusUterus
• Cervix – firm unless it is softened by relaxin during labor and delivery
Histology of the UterusHistology of the Uterus
1. Perimetrium2. Myometrium3. Endometrium
PerimetriumPerimetrium
• Part of the visceral peritoneum
MyometriumMyometrium
• Consists of three muscle layers and has oxytocin receptors
EndometriumEndometrium
• Divided into the 1. Stratum Functionalis2. Stratum Basalis
EndometriumEndometrium
• Spiral arteries supply the endometrium
CervixCervix
• Secretory cells of the cervix produce a cervical mucus
CervixCervix
• At mid cycle the mucus is thin and receptive to sperm
CervixCervix
• During most of the menstrual cycle the mucus is thick
VaginaVagina
• 10 cm in the adult
VaginaVagina
• Functions as a passageway for spermatozoa and the menstrual flow
VaginaVagina
• It is acidic in order to inhibit microorganisms and sperm
VaginaVagina
• The vaginal orifice in virgins is partially covered by the hymen
VulvaVulva
• External genitalia of the female
VulvaVulva
• It consists of 1. Mons pubs – rounded fatty eminence
overlying the pubic symphysis
VulvaVulva
2. Labia majora – covered with hair
VulvaVulva
3. Labia minora – thinner folds that are devoid of hair, they atrophy after menopause
VulvaVulva
4. Clitoris – homologous to the penis
VulvaVulva
5. Vestibule – cleft between labia minora where vaginal orifice opens to the outside
VulvaVulva
6. Vaginal orifice
VulvaVulva
7. Urethral orifices – between the clitoris and the vaginal orifice
VulvaVulva
8. Hymen
Mammary GlandsMammary Glands
• Milk producing glands that lie over the pectoralis major and serratus anterior muscle
Mammary GlandsMammary Glands
• Milk secreting cells (alveoli) are clustered in small compartments (lobules) within the breasts
Mammary GlandsMammary Glands
1. Alveoli2. Mammary ducts3. Lactiferous ducts4. Lactiferous sinuses5. Nipple
Mammary GlandsMammary Glands
• Function to synthesize milk and secretion and ejection of milk (lactation)
Mammary GlandsMammary Glands
• Areola is the pigmented skin that surrounds the nipple
Mammary GlandsMammary Glands
• Develop at puberty under the stimulation of rising estrogen and progesterone levels
Phases of the Female Phases of the Female Reproductive CycleReproductive Cycle
1. Menstrual cycle2. Preovulatory phase3. Ovulation4. Postovulatory phase
Menstrual CycleMenstrual Cycle
• First five days of cycle
Menstrual CycleMenstrual Cycle
• About 20 small follicles in each ovary begin to develop
Menstrual CycleMenstrual Cycle
• Stratum functionalis layer of the endometrium is shed discharging blood, tissue fluid, mucus, and epithelial cells
Menstrual CycleMenstrual Cycle
• It is shed due to declining progesterone at the end of the previous cycle
Preovulatory phasePreovulatory phase
• Between menstruation and ovulation
Preovulatory phasePreovulatory phase
• Lasting from days 6-13 in a 28 day cycle
Preovulatory phasePreovulatory phase
• Primary follicles develop into secondary follicles
Preovulatory phasePreovulatory phase
• A single secondary follicle develops into a Graafian or mature follicle
Preovulatory phasePreovulatory phase
• Maturing follicles secrete estrogen
Preovulatory phasePreovulatory phase
• The mature follicle continues to increase its estrogen production due to increasing levels of LH
Preovulatory phasePreovulatory phase
• Estrogen stimulates endometrial repair; a new stratum functionalis is formed
OvulationOvulation
• Rupture of the Graafian or mature follicle with release of the secondary oocyte into the pelvic cavity
OvulatationOvulatation
• LH transforms the ruptured follicle into the corpus luteum
OvulationOvulation
• Occurs on day 14
OvulationOvulation
• The high levels of estrogen during the last part of the preovulatory phase exerts a positive feedback on LH and GnRH to cause ovulation
OvulationOvulation
• GnRH promotes release of FSH and LH
OvulationOvulation
• LH surge brings about the ovulation
OvulationOvulation
• Increased body temperature due to progesterone, which increases just prior to ovulation
OvulationOvulation
• Clear cervical mucus due to high estrogen
OvulationOvulation
• Corpus luteum secretes estrogens and progesterone due to LH
Postovulatory phasePostovulatory phase
• Days 15-28
Postovulatory phasePostovulatory phase
• Time between ovulation and the onset of the next menstrual period
Postovulatory phasePostovulatory phase
• Estrogen and progesterone are secreted in large quantities by the corpus luteum
Postovulatory phasePostovulatory phase
• If fertilization and implantatin do not occur, estrogen and progesterone secreted by the corpus luteum inhibit LH
Postovulatory phasePostovulatory phase
• So Corpus luteum loses its support
Postovulatory phasePostovulatory phase
• The copus luteum degenerates and becomes the corpus albicans
Postovulatory phasePostovulatory phase
• The decreased levels of estrogen and progesterone initiatates another menstrual phase
Postovulatory phasePostovulatory phase
• Because estrogen and progesterone levels drop, there is less negative feedback on the Hyp. and A.P.
Postovulatory phasePostovulatory phase
• FSH and LH begin to rise a bit at the end of the cycle, causing another round of follicular development (about 20)
Postovulatory phasePostovulatory phase
• If fertilization and implantation do occur, the corpus luteum is maintained until the placenta takes over
Postovulatory phasePostovulatory phase
• Corpus luteum is maintained by human chorionic gonadotropin (hCG) from the developing placenta
Postovulatory phasePostovulatory phase
• The corpus luteum secretes estrogens and progesterones to support pregnancy and breast development for lactation
Postovulatory phasePostovulatory phase
• Once the placenta begins secreting estrogen and progesterone, the role of corpus luteum becomes minor
Postovulatory phasePostovulatory phase
• Endometrium thickens in anticipation of implantation