Unit 4 - Human Reproduction Flashcards
Evolution
How life changes over time by processes that change the genetic composition of populations
Ecology
How organisms interact with each other
Structure and function
How the physical structures in an organism relate to their functions
Energy and matter transformation
How energy and matter are transformed by biological processes to make life possible
Hormones
Signaling molecules that communicate messages within cells, and to different parts of your body
Protein or polypeptide hormones
Made of chains of amino acids
Protein hormone examples
Insulin, HGH (human growth hormone), oxytocin
Steroid hormones
Derived from lipids, specifically cholesterol
Steroid hormone examples
Testosterone, estrogen, progesterone, cortisol
Amine hormones
Derived from a single amino acid, and some function like protein hormones and some more like steroids
Amine hormone examples
Catecholamines like epinephrine (act like protein)
Why do we care about the molecular structure of hormones?
The molecular structure of hormones determines where their receptors are located, and therefore, how these hormones function
Forms of chemical signaling
Autochrome, signaling across gap junctions, paracrine, endocrine
Autocrine signaling
A cell targets itself; hormones can also do this type
Signaling across gap junctions
A cell targets a cell connected by gap junctions; this is primarily what your nervous system uses
Paracrine signaling
A cell targets a nearby cell; hormones can do this type
Endocrine signaling
A cell targets a distant cell through the bloodstream; hormones are especially important for this type!
Where in the body are hormones involved?
Hormones are the communication component of the endocrine system - the network of glands and organs that use hormones to send messages to parts of the body via the circulatory system
What critical processes do hormones regulate?
Blood sugar (insulin and glucagon), growth, mating and reproduction, and metabolism and appetite
Where are hormones produced?
In the GLANDS of the endocrine system
Hypothalamus gland
“Primary master control”; controls other glans that make hormones, body temp, hunger, mood, sleep, sex drive
Pituitary gland
“Secondary master control”; controls other glands that make growth hormones
Parathyroid gland
Controls amount of calcium in the body
Pancreas gland
Controls blood sugar levels
Thyroid gland
Controls metabolism and heart rate
Adrenal gland
Controls sex drive and sleep
Pineal gland
Controls sleep
Ovaries (gland)
Control female reproduction
Testes (gland)
Control male reproduction
Where do hormones travel?
Endocrine signaling targets cells in distant tissues and organs
How do hormones travel?
They move from where they are secreted (endocrine cell in a gland) to where they need to communicate their message (target cell) through the circulatory system
How do hormones communcate their message and induce a response?
For hormones to function as signals, cells need to receive the signal, which depends on which cells have receptors for the signals
What is targeting function?
Not all cells have receptors (an aspect of cell structure) for every hormones
Non-lipid-soluble hormones signaling
(Like protein and amine hormones) Bind to receptors on the cell surface, usually directly stimulate a cytoplasmic response, which is often carried out by a series of molecular interactions called a signal transduction
Signal transduction steps
Reception, transduction, and response
Reception step of signal transduction
Hormone (signaling molecule) binds to receptor on cell surface
Transduction step of signal transduction
Signal is relayed through other molecules via a series of chemical reactions
Response step of signal transduction
The cellular response to the hormone is activated and carried out
Lipid soluble hormones signaling
Typically get their message across by directly stimulating a gene regulation response
Lipid soluble hormone signaling steps
Lipid-soluble hormone diffuses through plasma membrane, hormone binds with receptor in cytoplasm forming a receptor-hormone complex, receptor-hormone complex enters the nucleus and triggers gene transcription, and transcribed mRNA is translated into proteins that alter cell activity
Hormones that don’t pass through cell membranes
Usually initiate a response in the cytoplasm. Typically protein hormones because they are not lipid soluble and cell membranes are made of lipids
Protein hormone signaling examples
Initiating a signal transduction to alter the activity of an enzyme in the cytoplasm, or initiating a signal transduction to move a molecule from one part of the cell to another
Hormones that do pass through cell membranes
Usually directly affect the expression of genes, and therefore the production of proteins in a cell. Typically steroid hormones because they are lipid soluble and can pass through the membranes made up of lipids
Steroid hormone signaling examples
Turn off a gene (stop making proteins), turn on a gene (start making proteins), turn up gene expression (make more proteins), or turn down gene expression (make fewer proteins)
Hormone cascade
A series of hormone actions in which a hormone stimulates another cell to release another hormone
Cells that make and release hormones
Endocrine cells
Tropic hormones
Hormones that regulate (either by stimulating or inhibiting) the release of other hormones
How are hormones regulated?
Often by feedback loops
Positive feedback
A change in a parameter in one direction triggers a response that moves that parameter in the same direction. Aka the enhancement or amplification of an effect caused by its own influence on the process that gives rise to it. Build build build build release
Positive feedback example
Account balance grows -> more interest earned
Negative feedback
A change in a parameter in one direction triggers a response that moves that parameter in the opposite direction. The counter action of an effect by its own influence on the process that gives rise to it. Change detected, back to set point, change detected, back to set point
Negative feedback example
Body temperature rises, body sweats more, body temperature drops
Which type of feedback is mostly in biology?
Negative feedback loops because they are really good at maintaining set points
Spermatogenesis
Sperm creation
Where is sperm produced
In seminiferous tubules
Seminiferous tubules
Tube structures coiled inside the testes
Where do sperm mature?
In the epididymis (~3 weeks of travel from seminiferous tubules through epididymis)
Epididymis
A mass of coiled tubes right next to the testes
Vas Deferens
Another tube, which sperm travel leave the epididymis to travel through upon ejaculation
How long does spermatogenesis take?
Full process takes about 8 weeks and is occurring constantly, regulated by hormones
How is spermatogenesis regulated by hormones?
Sertoli cells nurture sperm development and Leydig cells produce testosterone
First step of spermatogenesis within seminiferous tubules
Luteinizing hormone (LH) binds to its receptor on Leydig cells and stimulates production and secretion of testosterone
Second step of spermatogenesis within seminiferous tubules
Follicle-stimulating hormone (FSH) binds to its receptor on Sertoli cells and weakly stimulates spermatogenesis
Third step of spermatogenesis within seminiferous tubules
Testosterone from Leydig cells bind to receptors in nuclei of Sertoli cells and also weakly stimulate spermatogenesis
Fourth step of spermatogensis within seminiferous tubules
The binding of FSH to its receptor increases the expression of testosterone receptors. Thus, spermatogenesis is strongly stimulated only when both FSH and testosterone are present in Sertoli cells!
Where does LH and FSH for spermatogensis come from?
GnRH released from hypothalamus stimulates the release of LH and FSH, marking the beginning of puberty
How is spermatogenesis regulated by a negative feedback loop?
There is a range of “optimal” sperm levels in the testes, so hormones react to extremes in either direction to regulate back to this range. (~20 million/mL)
What happens when sperm levels reach the higher end of the optimal range?
The higher levels of testosterone in the blood will inhibit the hypothalamus from releasing GnRH and inhibit the pituitary gland from releasing LH and FSH, which slows down sperm production and lowers the levels of testosterone in the blood. Higher levels of inhibin in the blood also inhibit the pituitary hormones
What happens when sperm levels drop below the lower end of this optimal range?
The lower levels of testosterone in the blood can’t block the release of GnRH, LH, and FSH anymore. The Sertoli cells also stop producing inhibin, resulting in increased release of GnRH, LH, and FSH and an increase in the signals that Sertoli cells need to stimulate sperm production, including the increase of testosterone levels in the blood
Secondary sex characteristics
Features that distinguish between the sexes, but are not directly part of the reproductive system
Testosterone effects on secondary sex characteristics
More hair, deep voice, more muscle, broad shoulders, and narrow hips
What do testosterone supplements do?
Increase secondary sex characteristics, but they also block the body’s messages that signal spermatogenesis to take place
Basic female reproductive steps
- Eggs mature in the ovaries
- Every month (usually) one egg is released into the fallopian tube
- If it’s not fertilized by sperm, the egg is shed from the body through the vagina, along with the lining of the uterus, during menstruation. If it’s fertilized by sperm, the embryo will implant into the lining of the uterus
Oogenesis
The production of eggs
Oogenesis details
All the eggs a female will ever have are generated before birth and exist in the ovaries in an immature stage until puberty. After puberty, each month the eggs mature in the ovaries inside of follicles in preparation for potential fertilization
What is PCOS?
Polycystic Ovarian Syndrome. A hormonal disorder or imbalance relatively common among women of reproductive age (6-12%)
PCOS symptoms
Irregular periods, excess body hair, acne, fertility issues
What happens with PCOS?
Multiple cysts (polycystic) develop in ovaries as a result of failure to ovulate. The cysts are basically partially developed follicles that never released their eggs as they should have (hence the irregular periods and infertility)
How is PCOS treated?
Multiple ways doctors treat it, depending on which symptoms are most important to the patient. Many people are able to successfully manage their PCOS and achieve pregnancy
How is the irregular menstrual cycle symptom of PCOS treated?
Combination birth control pills, progestin therapy
How is the no ovulation symptom of PCOS treated?
Various medications to stimulate the ovaries
How is the excessive hair growth symptom of PCOS treated?
Birth control pills, various medications, electrolysis or laser hair removal
Ovarian and uterine cycles
Both ovaries and uterus are involved in the female reproductive process, each have their own cycles simultaneously together called the “menstrual cycle”, which affect each other and are both regulated by hormones. On average, about 28 days, but lots of variation
What is the job of ovaries?
To produce and release a mature egg that can be fertilized
What does the ovarian cycle control?
How the egg matures and when the egg is released from the ovary into the fallopian tube
What hormones impact the ovaries/ovarian cycle?
Ovarian cycle is regulated by hormones secreted by the hypothalamus and pituitary gland, and the ovaries also produce their own hormones to send messages to other parts of the body
What are the phases of the ovarian cycle?
Two distinct phases, separated by the event of ovulation (the release of an egg from an ovary)
What mainly happens in the ovaries during follicular phase of ovarian cycle?
~5-20 follicles develop in preparation to release a mature egg in the event of ovulation
What mainly happens in the ovaries during ovulation?
A single follicle releases a single mature egg into the fallopian tube
What mainly happens in the ovaries during the luteal phase?
The follicle that just released the egg becomes the “corpus luteum”, which releases important hormones in preparation for potential fertilization
Follicular phase ovarian hormone effects
Follicles produce low levels of estradiol that inhibit GnRH secretion by the hypothalamus, keeping LH and FSH levels low
Follicular phase pituitary hormone effect
LH and FSH stimulate several follicles to grow
Follicular phase estradiol hormone
Low levels, inhibitory effect! But levels increase as follicles develop
Ovulation phase ovarian hormone effects
Growing follicles begin to produce high levels of estradiol, which stimulate GnRH secretion by the hypothalamus, LH and FSH levels rise, resulting in ovulation about a day later
Ovulation phase pituitary hormone effect
LH and FSH stimulate maturation of one of the growing follicles
Ovulation phase estradiol hormone
Higher levels, stimulatory effect!
Luteal phase ovarian hormone effects
The corpus luteum secretes estradiol and progesterone that block GnRH production by the hypothalamus and LH and FSH production by the pituitary, and cause the endometrium to further develop
Luteal phase pituitary hormone effect
LH stimulates growth of a corpus luteum from follicular tissue left behind after ovulation
Luteal phase estradiol hormone
Higher levels, inhibitory effect!
Luteal phase explanation
The corpus luteum releases estrogen and progesterone during the luteal phase, but as the corpus luteum degenerates throughout the luteal phase, estrogen and progesterone levels also start to drop. If the structure goes away, so does the function… As long as there is no embryo implantation, then hormone levels are back to where we started, and the cycle starts all over again
What’s the job of the uterine cycle?
To prepare and maintain a suitable uterine environment for a potential embryo and fetus
What does the menstrual cycle include?
Not just menstruation!
What hormones regulate the menstrual cycle?
The ovarian hormones progesterone and estrogen
What mainly happens in the uterus during the follicular phase?
The period. The tissue of the uterine lining sheds from the body, which thins out the lining, called menstruation. The lining starts to thicken towards the end of the follicular phase. By definition, the first day of a new cycle is the first day of bleeding
What mainly happens in the uterus during ovulation?
Not a whole lot, but the uterine lining continues to thicken from the surge in estrogen
What mainly happens in the uterus during the luteal phase?
The high levels of estrogen and progesterone from the corpus luteum further thicken and vascularize the uterine lining and maintain it at this level so it is ready for a potential embryo implantation
When is the potential pregnancy window?
After ovulation
Why is the potential pregnancy window after ovulation?
The progesterone and estrogen secreted by corpus luteum helps build the uterine lining to make a comfy environment for the potential embryo.
Follicular phase uterine hormone effects
Ovarian hormone effects - Follicles produce low levels of estradiol that inhibit GnRH secretion by the hypothalamus, keeping LH and FSH levels low, and cause endometrial arteries to constrict, resulting in menstruation
Ovulation phase uterine hormone effects
Ovarian hormone effects - Growing follicles produce low levels of estradiol, which stimulate GnRH secretion by the hypothalamus, LH and FSH levels rise, resulting in ovulation about a day later, and cause the endometrium to thicken
Luteal phase uterine hormone effects
Ovarian hormone effects - The corpus luteum secretes estradiol and progesterone that block GnRH production by the hypothalamus and LH and FSH production by the pituitary, and cause the endometrium to further develop
What happens if there is no implantation of an embryo by the time the corpus luteum degenerates?
Progesterone and estrogen from the CL (which were maintaining the uterus) drop, and the uterine lining is shed along with the unfertilized egg through menstruation
Period poverty
Refers to the “prevalent phenomenon of being unable to afford products such as pads, tampons, or liners to manage menstrual bleeding” as well as “inadequate access to toilets, hand-washing receptacles, and hygienic waste management
Why does period poverty exist?
Unnecessary stigma rooted in myths, falsehoods, and misconceptions, the result of forced shame upon a natural biological process that women experience
Why is period poverty an issue of concern?
Causes menstruators to use mentally and physically unsafe alternatives, such as rags, paper towels, toilet paper, used pads of cardboard, increasing risk of irritation and urogenital infections. Linked to increased anxiety, depression, and distress. Prevents low-income menstruators from bleeding with dignity, and can cause menstruators to miss school and work, and therefore negatively impact girls’ education and economic well-being
Why does the UN recognize period poverty a human rights issue?
It is intrinsically related to human dignity because “menstruation-related teasing, exclusion and shaming also undermine the principle of human dignity”
What is contraception?
Aka birth control. Various medications, procedures, devices, and behaviors that are implemented to prevent pregnancy as a result of sexual intercourse
What are the two ways contraceptives can work?
Either by creating a physical barrier between various anatomical structures involved in reproduction, or by using disrupting processes involved in reproduction
Barrier/physical methods of birth control
Interfere with physical reproductive anatomy or structures, both male and female methods
Female condoms
Female condoms are placed inside the vagina to form a physical barrier between the vagina walls and penis (or other penetrating object) during intercourse
Male condoms
Male condoms are placed over the penis to form a physical barrier between the skin of the penis and the environment
Diaphragms
The diaphragm fits over the cervical opening, preventing sperm from entering the uterus
Sponges
A soft sponge that absorbs spermicide and also creates a physical barrier between the vagina and cervix
Spermicides
Spermicide can be used together with other methods like the diaphragm and sponge
The copper IUD
Small T-shaped flexible plastic structure wrapped with copper wire, where the copper creates a toxic environment for sperm and egg, preventing pregnancy. Does not contain or release hormones, can remain in place for up to 10 years, and can be removed at any time
Sterilization types
Tubal ligation and vasectomy
Tubal ligation
Fallopian tubes are cut, ties, or blocked off to permanently prevent an egg from being fertilized
Vasectomy
The vas deferens is cut and sealed off to prevent sperm from being present in the semen. Can be reversible, but are typically considered permanent
Hormonal methods of birth control
Interfere with hormone cycles to prevent ovulation or fertilization. Female methods only so far
The pill
~90% effective with typical use. Consistent and high estrogen/progesterone levels prevent ovulation
How do the three weeks of the pill work?
One week of placebo pills (no hormones), two weeks of hormone pills. A person usually bleeds during the week of placebo pills due to the sudden drop in progesterone, which simulates the uterine contractions and tissue breakdown, but it’s not a TRUE menstrual period because there was/is no ovulation
Two main types of birth control pills
Combination pills (estrogen and progestin) or “mini-pill” (progestin only)
Emergency contraception
Works mainly by delaying or preventing ovulation immediately. Does not affect an embryo that has already been implanted. Emergency birth control pills contain either levonorgestrel (Plan-B, others, can get over the counter) or ulipristal acetate (Ella, prescription-only).
What is Plan B’s mechanism of operation?
Prevention of ovulation
The ring and the patch
~90% effective with typical use. These options slowly release continuous doses of hormone into the blood to prevent ovulation. Work similarly to the pill, and typically need to be replaced monthly
The hormonal IUD and the implant
~99% effective when used correctly. Continuous release of hormones that thicken the cervical mucus, preventing sperm from reaching egg, can prevent ovulation, and thins uterine lining. Can remain in place for up to 5 years and can be removed at any time
The Shot
Depo-Provera (injection). ~99% effective with typical use. Contains progesterone to suppress ovulation and thicken cervical mucus to prevent fertilization. Shot given every three months to be effective
What info can help us to either decrease or increase chances of pregnancy?
The female cycle length and dates, including periods of menstruation, day of ovulation, how long an egg is viable after ovulation, and how long sperm are viable after ejaculation inside a female reproductive system
What is the calendar, rhythm, or fertility-awareness method?
Using this knowledge as a form of birth control or family planning
Why do we hear that someone can get pregnant at any time?
Usually the idea stems from the fact that the calendar method relies on the unpredictability of female cycles, but cycles can be somewhat unpredictable. We also can’t calculate the day of ovulation with confidence until a cycle is completed, we can only estimate it based on the previous cycle
Can a person get pregnant after having sex on their period?
Yes, it is definitely possible
Where does fertilization happen?
In the fallopian tube
Steps of implantation
Sperm and egg fuse together to form a zygote, fertilized egg travels from the fallopian tube to the uterus and finds a comfy spot to implant. This takes several days, and the cells of the embryo are undergoing rapid cell division. After about a week, the embryo “hatches” out of its protective covering and implants within the uterine lining
What happens with hormones during implantation?
At about day 4, the embryo starts releasing the hormone HCG, which targets the corpus luteum and prevents it from degenerating for the first several weeks of pregnancy (until the placenta takes over) so that the corpus luteum keeps producing estrogen and progesterone, which maintains the uterine lining
Gestation
Lasts ~260-280 days/~39-40 weeks/~9 months. Often discussed in thirds (or trimesters) each about 3 months long
At how many weeks is a baby considered premature?
Before 37 weeks is considered pre-term, but with proper care, most babies born after 34 weeks survive
At how many weeks is a baby considered overdue?
At 42 weeks
First step of labor and birth
As baby enters final stage of growth, it physically stretches the uterus to its limits, which triggers the release of stress hormones in the mother’s body. Baby exerts pressure on cervix and walls of uterus
Second step of labor and birth
The release of stress hormones trigger release of estrogens, so estrogen levels rise
Third step of labor and birth
Estrogen inhibits production of progesterone, so progesterone levels finally drop. Estrogen always causes the uterus to be more sensitive to the hormone oxytocin
Fourth step of labor and birth
Oxytocin binds to receptors on uterine wall, which induces more contractions
Fifth step of labor and birth
As a result of contractions, baby is pushed further down and presses against cervix
Sixth step of labor and birth
Pressure causes cervix to stretch and widen, “dilating”. Nerves impulses from this activity travel to hypothalamus
Seventh step of labor and birth
After receiving nerve signals, hypothalamus signals the pituitary to release more oxytocin, which causes the uterus to contract again… and the whole cycle starts over!
What is Pitocin and when is it used?
A synthetic form of oxytocin used when labor isn’t moving quickly enough (can be harmful to mother and baby) or to induce labor for overdue babies
What is labor’s feedback loop?
An ongoing positive feedback, one of the few biological examples, and only stopped by the delivery of the baby
What’s in breastmilk?
Fats, carbohydrates, protein, vitamins/minerals, anti-infective factors
What kinds of anti-infective factors are in breastmilk?
Immunoglobulin, white blood cells, whey proteins that can kill pathogens, and oligosaccharides
Colostrum
Special milk secreted in first 2-3 days after delivery with higher concentration of vitamins and proteins compared to mature milk. Only produced in small amounts (40-50 mL) , but that’s all baby needs. Deep yellow color
Transition milk
By third day, milk has fully “come in” and baby is taking 300-400 mLs every 24 hours, amounts increasing as baby grows. Transition milk still contains characteristics of colostrum. Color changing to more white
Mature milk
After two weeks, milk is “mature” with lower concentrations of some vitamins and protein compared to colostrum, but higher in fat
Alveoli
Hollow spaces for milk to pool
Milk-secreting cells
Surround the alveoli
Ducts
Allow milk to flow from alveoli to nipple
Lobule
A bunch of alveoli that feed into the same duct
Prolactin hormone
Stimulates milk production. Suckling stimulates prolactin release, so stopping breastfeeding/suckling stops production of prolactin, which stops production of milk. Also influences GnRH, FSH, and LH to prevent ovulation and menstruation, which is how breastfeeding can act as a form of birth control
Oxytocin hormone
Stimulates milk release/ejection. Makes milk that is already in the alveoli actually flow and be available to baby. Release stimulated by touching, smelling, seeing, thinking about baby. Negative emotions or pain can inhibit oxytocin release and make it more difficult to breastfeed
What is postpartum?
The period of time after giving birth when the previously pregnant body changes drastically, very tired and sore. Takes 4-6 weeks to feel like self again, longer if had c-section
Physical changes during postpartum
Contractions shrink uterus (6-8 weeks), sore muscles from labor, bleeding and discharge (couple weeks to months), vaginal or c-section scar soreness/pain/ discomfort/numbness, and breast enlargement from rapidly filling milk
Hormonal changes during postpartum
Rapid and drastic changes occurred during labor/delivery, new hormones now circulating and and fluctuating from breastfeeding, may influence post-partum moods and behavior, but still a challenging and inconclusive field of research
Hormones and postpartum depression
Very difficult to attribute exact cause of conditions like postpartum depression to hormones, but many studies suggest they may be linked in some way. Estriol thought to be particularly important
Hormones and postpartum bonding
Hormone cortisol thought to be particularly important in mothers responding to baby smells, cries. Oxytocin might be important in reducing stress response in mothers. Oxytocin and testosterone important in father’s responding. Some evidence of hormones influencing adopted parent behavior as well
