The Reproductive system
The male system
We've all been bombarded with pictures and diagrams of the male reproductive system--but instead of looking at too many diagrams, it will be better to focus on the concepts and processes that happen within the male system.
The parts of the male reproductive system include:
the scrotum, testes, the penis, the epididymis, the ductus deferens & ejaculatory duct, the urethra, seminal vesicles, the prostate gland, bulbourethral glands, and spermatic fluids
The parts of the male reproductive system include:
the scrotum, testes, the penis, the epididymis, the ductus deferens & ejaculatory duct, the urethra, seminal vesicles, the prostate gland, bulbourethral glands, and spermatic fluids
Those structures provide a good "map" of the route of sperm during the male sexual response. Before understanding the pathway, what really happens during the male sexual response? First, there is an erection that happens because the erectile tissue of the penis starts to fill with blood. It is started by basically anything--touch, sights, sounds, and mechanical stimulation. It starts to fill with blood because of nitric oxide which is released by the parasympathetic system. Basically, nitric oxide causes the erection. As the corpora cavernosa expands, drainage veins in the penis are put on "lock down" and very little blood is able to leave, thus maintaining the erection. The corpus spongiosum is what surrounds the urethra and keeps it open (for the ejaculate pathway) despite all of the pressure in surrounding tissues. Ejaculation is the "propulsion" of semen from the ducts in the male system. Sympathetic nerves during ejaculation are responsible for the contraction of reproductive ducts contracting to expel fluids. They also cause the bladder muscle to constrict which prevents urination. Furthermore, the bulbospongiosum muscles contract and the semen is released out of the urethra. That is the entire sexual response!
The exact pathway the ejaculatory fluid takes through the male system is: starting at the epididymis tail, then into the vas deferens, up the spermatic cord into the pelvic cavity, over the ureter (by the prostate behind the bladder), at this location--the seminal vesicles join with the vas deferens to form the ejaculatory duct which passes through the prostate and into the urethra of the penis.
Those structures provide a good "map" of the route of sperm during the male sexual response. Before understanding the pathway, what really happens during the male sexual response? First, there is an erection that happens because the erectile tissue of the penis starts to fill with blood. It is started by basically anything--touch, sights, sounds, and mechanical stimulation. It starts to fill with blood because of nitric oxide which is released by the parasympathetic system. Basically, nitric oxide causes the erection. As the corpora cavernosa expands, drainage veins in the penis are put on "lock down" and very little blood is able to leave, thus maintaining the erection. The corpus spongiosum is what surrounds the urethra and keeps it open (for the ejaculate pathway) despite all of the pressure in surrounding tissues. Ejaculation is the "propulsion" of semen from the ducts in the male system. Sympathetic nerves during ejaculation are responsible for the contraction of reproductive ducts contracting to expel fluids. They also cause the bladder muscle to constrict which prevents urination. Furthermore, the bulbospongiosum muscles contract and the semen is released out of the urethra. That is the entire sexual response!
The exact pathway the ejaculatory fluid takes through the male system is: starting at the epididymis tail, then into the vas deferens, up the spermatic cord into the pelvic cavity, over the ureter (by the prostate behind the bladder), at this location--the seminal vesicles join with the vas deferens to form the ejaculatory duct which passes through the prostate and into the urethra of the penis.
HOW THE SCROTUM WORKS: What is the scrotum for? It houses the testes, but also protects them by keeping them warm or cool--whichever is needed for sperm survival. When the environment is cold, the scrotum will pull up tight to retract the testes closer to the body, keeping the sperm at a good temperature. When the temperature is too hot, the scrotum will relax and expand to increase surface area to release heat, cooling the testes.
The exact pathway the ejaculatory fluid takes through the male system is: starting at the epididymis tail, then into the vas deferens, up the spermatic cord into the pelvic cavity, over the ureter (by the prostate behind the bladder), at this location--the seminal vesicles join with the vas deferens to form the ejaculatory duct which passes through the prostate and into the urethra of the penis.
Those structures provide a good "map" of the route of sperm during the male sexual response. Before understanding the pathway, what really happens during the male sexual response? First, there is an erection that happens because the erectile tissue of the penis starts to fill with blood. It is started by basically anything--touch, sights, sounds, and mechanical stimulation. It starts to fill with blood because of nitric oxide which is released by the parasympathetic system. Basically, nitric oxide causes the erection. As the corpora cavernosa expands, drainage veins in the penis are put on "lock down" and very little blood is able to leave, thus maintaining the erection. The corpus spongiosum is what surrounds the urethra and keeps it open (for the ejaculate pathway) despite all of the pressure in surrounding tissues. Ejaculation is the "propulsion" of semen from the ducts in the male system. Sympathetic nerves during ejaculation are responsible for the contraction of reproductive ducts contracting to expel fluids. They also cause the bladder muscle to constrict which prevents urination. Furthermore, the bulbospongiosum muscles contract and the semen is released out of the urethra. That is the entire sexual response!
The exact pathway the ejaculatory fluid takes through the male system is: starting at the epididymis tail, then into the vas deferens, up the spermatic cord into the pelvic cavity, over the ureter (by the prostate behind the bladder), at this location--the seminal vesicles join with the vas deferens to form the ejaculatory duct which passes through the prostate and into the urethra of the penis.
HOW THE SCROTUM WORKS: What is the scrotum for? It houses the testes, but also protects them by keeping them warm or cool--whichever is needed for sperm survival. When the environment is cold, the scrotum will pull up tight to retract the testes closer to the body, keeping the sperm at a good temperature. When the temperature is too hot, the scrotum will relax and expand to increase surface area to release heat, cooling the testes.
What is semen, exactly?
Semen is an interesting body fluid--you probably have not thought about it because most people, don't really think about semen. But in anatomy, your job is to learn it all! Semen is not all sperm, contrary to popular belief. About 95% of semen is fluids from ducts and glands in the reproductive system that give the sperm something to exist in and be transported out with. Only 5% of semen is made up of sperm cells! In the semen, there is fructose to nourish the sperm. There are also some proteins that help to activate the sperm, which are secreted (proteins) by the prostate gland. Without the prostate gland secretions, sperm would not be able to "swim". About 1/3 of semen volume is from the prostate. Before ejaculation, the bulbourethral glands secrete a clear mucus that clears the urethra of urine traces to make sure the pathway is safe and neutralized for sperm. Semen also contains prostaglandins that act on the female system if it is deposited there. Prostaglandins make cervical mucus more fluid (make it easier for sperm to swim through) and stimulates a "reverse peristalsis" of the uterine muscles--bringing the fluids into the uterus rather than expelling them through the vagina. Seminalplasmin is an interesting addition to semen because it is a natural antibiotic chemical, keeping semen from being a transporter of bacteria.
Watch the video below to learn about spermatogenesis--how sperm are made!
Watch the video below to learn about spermatogenesis--how sperm are made!
The brain-testicular axis
So, what is it? The brain-testicular axis is basically the communication between the brain and the testes with hormones. It includes activity from the hypothalamus, anterior pituitary gland, and the testes. The hormones involved are Gonadotropin Releasing Hormone (GnRH), gonadotropins (FSH & LH), and testicular hormones (testosterone). All hormones are made from cholesterol. The hypothalamus releases GnRH, which targets the anterior pituitary and "tells" it to make Follicle Stimulating Hormone & Luteinizing Hormone (luteinizing hormone term is used for females because there is an egg release. In males, it is referred to as ICSH for "interstitial cell stimulating hormone, referring to the interstitial cells in the testes that make testosterone). FSH in males causes support cells of the seminiferous tubules (sustentacular cells) to release antigen-binding protein. When the testosterone from the interstitial cells combines with the ABP, spermatogenesis is triggered in the testes.
When levels of testosterone are high, it triggers a feedback to the anterior pituitary telling it that no more testosterone is needed. It is self-regulatory! Testosterone, beyond the reproductive system, targets all accessory organs and without it, they would "atropy" or die off. It is also the basis of sex drive in both male and female sexes (in the female, it comes from the anterior pituitary).
When levels of testosterone are high, it triggers a feedback to the anterior pituitary telling it that no more testosterone is needed. It is self-regulatory! Testosterone, beyond the reproductive system, targets all accessory organs and without it, they would "atropy" or die off. It is also the basis of sex drive in both male and female sexes (in the female, it comes from the anterior pituitary).
The female system
The female reproductive system consists of internal genitalia (ovaries and ducts) as well as external genitalia (vulva). The ovaries are the primary organs of the FRS.
Commonalities between the male & female systems:
1. Male bulbourethral gland & female vestibular gland = secrete mucus
2. Male scrotum is homologous to the female labia majora
3. Male ventral penis is homologous to the female labia minora
4. Male penis is homologous to the female clitoris
When they are homologous, these parts of the reproductive systems come from the same tissues when the fetus is developing. They start as "urogenital folds" and depending on genetics and hormones, will develop into testes/external system or ovaries/internal system.
Commonalities between the male & female systems:
1. Male bulbourethral gland & female vestibular gland = secrete mucus
2. Male scrotum is homologous to the female labia majora
3. Male ventral penis is homologous to the female labia minora
4. Male penis is homologous to the female clitoris
When they are homologous, these parts of the reproductive systems come from the same tissues when the fetus is developing. They start as "urogenital folds" and depending on genetics and hormones, will develop into testes/external system or ovaries/internal system.
the ovarian cycle
The ovarian cycle is complicated--which is why it is such a good idea to look at graphs and charts while learning about it. It will help you to visualize and understand the process.
1. Follicular phase: period of follicle growth
During this phase, promordial follicle grows to become a primary follicle, which then grows to a secondary follicle. During this phase, the zona pellucida forms, which is the "shell" around the oocyte. This is the barrier sperm have to get through for fertilization. The secondary follicle then becomes a vesticular (grafien) follicle. At this point, the antrum of the granulosa cell (holds the oocyte) expands. This full size follicle cell "bulges" out of the ovary and results in ovulation. If you look at the image below of the ovary, you can see how the oocyte gets bigger and bigger. That is all happening in this phase. Ovulation marks the movement to the next phase of the cycle.
2. Ovulation during Midcycle
This part of the cycle has very high levels of luteinizing hormone (LH) which is responsible for basically, kicking the oocyte out of the ovary.
3. Luteal phase: period of corpus luteum activity
After ovulation, the oocyte has left the follicle and the follicle is left behind in the ovary. This follicle grows and is the source of hormones that dictate fertility and menstruation. The leftover follicle is called the corpus luteum and it is responsible for secreting progesterone and estrogen. If pregnancy doesn't happen in 10 days, the corpus luteum dies off and leaves a scar within the ovaries. It then turns into corpus albicans which produces no hormones. If pregnancy does occur, then the corpus luteum remains to make hormones to "maintain the uterus" for the pregnancy until about 3 months in, where the placenta takes over.
1. Follicular phase: period of follicle growth
During this phase, promordial follicle grows to become a primary follicle, which then grows to a secondary follicle. During this phase, the zona pellucida forms, which is the "shell" around the oocyte. This is the barrier sperm have to get through for fertilization. The secondary follicle then becomes a vesticular (grafien) follicle. At this point, the antrum of the granulosa cell (holds the oocyte) expands. This full size follicle cell "bulges" out of the ovary and results in ovulation. If you look at the image below of the ovary, you can see how the oocyte gets bigger and bigger. That is all happening in this phase. Ovulation marks the movement to the next phase of the cycle.
2. Ovulation during Midcycle
This part of the cycle has very high levels of luteinizing hormone (LH) which is responsible for basically, kicking the oocyte out of the ovary.
3. Luteal phase: period of corpus luteum activity
After ovulation, the oocyte has left the follicle and the follicle is left behind in the ovary. This follicle grows and is the source of hormones that dictate fertility and menstruation. The leftover follicle is called the corpus luteum and it is responsible for secreting progesterone and estrogen. If pregnancy doesn't happen in 10 days, the corpus luteum dies off and leaves a scar within the ovaries. It then turns into corpus albicans which produces no hormones. If pregnancy does occur, then the corpus luteum remains to make hormones to "maintain the uterus" for the pregnancy until about 3 months in, where the placenta takes over.
how the ovarian cycle starts & works
During childhood, a girl will have growing ovaries. They will secrete very small amounts of estrogen and the release of GnRH (gonadotropin-releasing hormone) from the hypothalamus will be inhibited. When puberty approaches, the GnRH is released which targets the anterior pituitary to release FSH (follicle-stimulating hormone) and LH (luteinizing hormone). These two hormones act on the ovaries. All of this occurs until a menarche (first menstruation) happens.
Day 1: GnRH from the hypothalamus stimulates FSH & LH from the anterior pituitary
Next several days: FSH & LH mature the follicle in the ovary. The follicle begins to produce estrogen which lowers FSH & LH.
Day 14: Estrogen levels increase and they cause positive feedback on anterior pituitary--LH surge happens which triggers ovulation.
Post-ovulation: The oocyte has left the follicle, follicle becomes corpus luteum. This structure produces estrogen, inhibin, and progesterone (to maintain lining of uterus). FSH & LH are shut off.
Days 26-28: Decline of ovarian hormones and FSH & LH are back on. If there is no pregnancy, then progesterone levels fall and the uterine lining is compromised without the help of progesterone. A new cycle will start. If there is pregnancy, then progesterone levels stay up and there is no "period" or new cycle.
Day 1: GnRH from the hypothalamus stimulates FSH & LH from the anterior pituitary
Next several days: FSH & LH mature the follicle in the ovary. The follicle begins to produce estrogen which lowers FSH & LH.
Day 14: Estrogen levels increase and they cause positive feedback on anterior pituitary--LH surge happens which triggers ovulation.
Post-ovulation: The oocyte has left the follicle, follicle becomes corpus luteum. This structure produces estrogen, inhibin, and progesterone (to maintain lining of uterus). FSH & LH are shut off.
Days 26-28: Decline of ovarian hormones and FSH & LH are back on. If there is no pregnancy, then progesterone levels fall and the uterine lining is compromised without the help of progesterone. A new cycle will start. If there is pregnancy, then progesterone levels stay up and there is no "period" or new cycle.
the female sexual response
Like the male sexual response starts off with the parasympathetic nervous system, so does the female sexual response. The parasympathetic nerve impulses cause arteries in erectile tissue of the vulva to dilate. Blood flow increases, erectile tissues become swollen, and the vagina expands as well as elongates to prepare for coitus. The parasympathetic stimuli activate vestibular glands that secrete mucus into the vestibule of the vulva. The highest point of female stimulation is orgasm which causes reflexes where the muscles of the perineum and walls of uterus contract in a rhythm. These contractions help to get the sperm into the uterus.
conditions of the female reproductive system
Pelvic Inflammatory Disease: infection of the uterus and fallopian tubes
This usually comes from STD's (chlamydia, gonorrhea). It can cause permanent damage to the uterine structures and fertility. Someone who has high numbers of sexual partners, recurrent STD's, or someone who douches is at higher risk. The most common symptom is lower abdominal pain accompanied by a fever, unusual discharge, painful urination, as well as irregular menstrual cycles. The image below shows the effects of PID on fertility. The disease can cause changes in the tubes from too much bacteria or inflammation that can block sperm from reaching an egg.
This usually comes from STD's (chlamydia, gonorrhea). It can cause permanent damage to the uterine structures and fertility. Someone who has high numbers of sexual partners, recurrent STD's, or someone who douches is at higher risk. The most common symptom is lower abdominal pain accompanied by a fever, unusual discharge, painful urination, as well as irregular menstrual cycles. The image below shows the effects of PID on fertility. The disease can cause changes in the tubes from too much bacteria or inflammation that can block sperm from reaching an egg.
Endometriosis: endometrial tissues (usually found in uterus) are found outside of the uterus (i.e. on the ovaries)
This is a very interesting condition, only because, we never think that uterine tissues could ever grow on a bladder, intestines, or on a cervix. It is an absurd idea to think about, but it is real. It causes pain before and during periods, with sexual activity, infertility, and very heavy or irregular bleeding. Lower back pain is also common with diarrhea or constipation. The visual below is graphic, but shows clearly, what endometriosis looks like.
This is a very interesting condition, only because, we never think that uterine tissues could ever grow on a bladder, intestines, or on a cervix. It is an absurd idea to think about, but it is real. It causes pain before and during periods, with sexual activity, infertility, and very heavy or irregular bleeding. Lower back pain is also common with diarrhea or constipation. The visual below is graphic, but shows clearly, what endometriosis looks like.
Dysmenorrhea: painful menstruation
Caused by: high levels of hormone prostaglandin (this is the hormone that is present during childbirth that causes contractions). Primary dysmenorrhea usually occurs in healthy women and not related to any other problems. It could very well be a genetic condition. Secondary dysmenorrhea is caused by another disease or abnormality of the uterus. This condition is felt right before a woman menstruates until that menstruation cycle is over.
Caused by: high levels of hormone prostaglandin (this is the hormone that is present during childbirth that causes contractions). Primary dysmenorrhea usually occurs in healthy women and not related to any other problems. It could very well be a genetic condition. Secondary dysmenorrhea is caused by another disease or abnormality of the uterus. This condition is felt right before a woman menstruates until that menstruation cycle is over.
conception & pregnancy
For fertilization to occur, the timing must be JUST right. An oocyte is only viable for 24 hours, whereas sperm are viable from 24-72 hours. Sexual intercourse must occur 3 days before ovulation and 24 hours after ovulation--no more. Fertilization occurs when the sperm combines with the egg, then forms a zygote.
Pre-embryonic development:
The first cleavage of the combined sperm and egg produces two daughter cells. These are called blastomeres. It is then called a morula after 72 hours (16+ divisions). By day 5, the pre-embryo has about 100 cells (this is now called a blastocyst). This special group of cells is a fluid filled sphere with a single layer of trophoblasts and a cell mass in the center. The trophoblasts eventually create the placenta, and the inner cells become the embryonic disc.
Implantation: this begins 6 to 7 days after ovulation when the trophoblasts have a chance to adhere to the uterine wall (endometrium). Two layers form in the trophoblast layer. This implanted blastocyst will eventually be covered by endometrial material and the implantation phase is complete by 14 days after ovulation. Remember learning earlier that if pregnancy occurs, then the corpus luteum does not change into corpus albicans, and remains to create hormones? The trophoblastic cells secrete Human Chorionic Gonadotropin hormone that keeps the corpus luteum intact and "alive" until the 3rd month when the placenta takes over.
Placentation: the placenta forms from embryonic trophoblasts and maternal endometrial tissues. It is fully formed by month 3. The placenta secretes human placental lactogen, human chorionic thyrotropin, and relaxin.
Gastrulation: during week 3, the two layered embryonic disk becomes a 3 layered embryo.
EFFECTS OF PREGNANCY:
*The placenta secretes human placental lactogen, stimulating breast maturation and fetal growth
*Human chorionic thyrotropin increases maternal metabolism
*Parathyroid hormones rise, ensuring positive calcium balance
*GI tract: morning sickness from elevated estrogen & progesterone
*Increased urine output from fetal pressure and to handle additional fetal wastes
*Increase in blood volume and more chance of vericose veins from problems with venous return in legs
*CHADWICKS SIGN - vagina has purple hue and areola of breasts darken, weight gain of about 29 lbs
Pre-embryonic development:
The first cleavage of the combined sperm and egg produces two daughter cells. These are called blastomeres. It is then called a morula after 72 hours (16+ divisions). By day 5, the pre-embryo has about 100 cells (this is now called a blastocyst). This special group of cells is a fluid filled sphere with a single layer of trophoblasts and a cell mass in the center. The trophoblasts eventually create the placenta, and the inner cells become the embryonic disc.
Implantation: this begins 6 to 7 days after ovulation when the trophoblasts have a chance to adhere to the uterine wall (endometrium). Two layers form in the trophoblast layer. This implanted blastocyst will eventually be covered by endometrial material and the implantation phase is complete by 14 days after ovulation. Remember learning earlier that if pregnancy occurs, then the corpus luteum does not change into corpus albicans, and remains to create hormones? The trophoblastic cells secrete Human Chorionic Gonadotropin hormone that keeps the corpus luteum intact and "alive" until the 3rd month when the placenta takes over.
Placentation: the placenta forms from embryonic trophoblasts and maternal endometrial tissues. It is fully formed by month 3. The placenta secretes human placental lactogen, human chorionic thyrotropin, and relaxin.
Gastrulation: during week 3, the two layered embryonic disk becomes a 3 layered embryo.
EFFECTS OF PREGNANCY:
*The placenta secretes human placental lactogen, stimulating breast maturation and fetal growth
*Human chorionic thyrotropin increases maternal metabolism
*Parathyroid hormones rise, ensuring positive calcium balance
*GI tract: morning sickness from elevated estrogen & progesterone
*Increased urine output from fetal pressure and to handle additional fetal wastes
*Increase in blood volume and more chance of vericose veins from problems with venous return in legs
*CHADWICKS SIGN - vagina has purple hue and areola of breasts darken, weight gain of about 29 lbs
Labor & childbirth
Labor begins after weeks of high estrogen that causes weakness in the myometrium of the uterus. As birth approaches, the levels of oxytocin and prostaglandin rise in the mother and causes strong uterine contractions. Emotional and physical stress sets off a positive feedback system that pumps out more oxytocin.
Stage 1: Dilation
This lasts from the onset of labor until the cervix is dilated 10 cm. Beginning contractions occur about every 15-30 minutes and last about 10 to 30 seconds. Then, the amnion ruptures (water breaking) and engagement occurs as the infant moves into the pelvis.
Stage 2: Expulsion
This stage lasts from full dilation until delivery of the child is complete. The contractions in this stage happen every 2-3 minutes and last for a minute long. Crowning occurs, but only when the very largest measurement of the head is protruding from the vulva.
Stage 2/3: Delivery of Placenta
This happens within 30 minutes of birth. All fragments of the placenta must be removed to make sure the mother does not bleed out.
AFTER BIRTH:
Transitional period: Unstable period for first 6-8 hours after birth. The baby is active at first, with increased heart rate, irregular respirations, and falling temperature. Activity then goes away and sleep/wake periods go on/off every 3 hours. The second active stage is noted with regurgitation of mucus and debris.
Lactation: prolactin is released to encourage milk production in the mother's breasts. Estrogen, progesterone, and lactogen stimulate the hypothalamus to make prolactin releasing hormone, forcing more prolactin to be made. The first milk the baby has is called the colostrum and it is the most nutritious feeding the baby will ever have from the breasts.
Stage 1: Dilation
This lasts from the onset of labor until the cervix is dilated 10 cm. Beginning contractions occur about every 15-30 minutes and last about 10 to 30 seconds. Then, the amnion ruptures (water breaking) and engagement occurs as the infant moves into the pelvis.
Stage 2: Expulsion
This stage lasts from full dilation until delivery of the child is complete. The contractions in this stage happen every 2-3 minutes and last for a minute long. Crowning occurs, but only when the very largest measurement of the head is protruding from the vulva.
Stage 2/3: Delivery of Placenta
This happens within 30 minutes of birth. All fragments of the placenta must be removed to make sure the mother does not bleed out.
AFTER BIRTH:
Transitional period: Unstable period for first 6-8 hours after birth. The baby is active at first, with increased heart rate, irregular respirations, and falling temperature. Activity then goes away and sleep/wake periods go on/off every 3 hours. The second active stage is noted with regurgitation of mucus and debris.
Lactation: prolactin is released to encourage milk production in the mother's breasts. Estrogen, progesterone, and lactogen stimulate the hypothalamus to make prolactin releasing hormone, forcing more prolactin to be made. The first milk the baby has is called the colostrum and it is the most nutritious feeding the baby will ever have from the breasts.