Module 11: Reproduction and Development III Flashcards
What are the 4 phases of the human sex act? Describe each phase.
- Excitement: erotic stimuli prepare for copulation.
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Plateau: changes that started during excitement intensify.
- Increased heart rate, BP, blood flow, respiratory rate
- Orgasm (climax): in both sexes is a series of muscle contractions accompanied by intense pleasurable sensations and increased blood pressure, heart rate and respiration rates
- Resolution: parameters return to normal
Erection in both sexes is a state of _____. Describe what this means.
Vasocongestion. Arterial blood flow into spongy erectile tissue exceeds venous outflow (increased blood flow)
Erotic stimuli are sexually arousing _____, _____ and _____ stimuli, which can vary greatly from person to person.
Tactile, sensory and psychological
What are erogenous zones?
Regions of body with receptors for tactile stimuli
Describe the erection reflex. (5 steps)
- Stimuli excite higher brain centers causing autonomic pathway activation (output).
- The PNS response (ACh) is stimulated while the SNS is inhibited. ACh released from parasympathetic nerves binds muscarinic ACh receptors on endothelial cells, resulting in the production of nitric oxide (NO) in endothelial cells.
- NO then enters smooth muscle cell and causes relaxation of vascular smooth muscle (↑MLCP, ↓Ca2+i).
- Penile arterioles vasodilate, causing an erection.
- Engorgement caused by blood in corporal tissue compresses veins, preventing blood flow back into the veins, maintaining the erection
Climax coincides with _____ and _____. Define each action and the muscle control involved.
Emission, ejaculation.
Emission (sympathetic activation of smooth muscle): the movement of sperm out of the vas deferens and into the urethra, where it is joined by secretions from the accessory glands to make semen.
Ejaculation (somatic [skeletal] muscle): the expulsion of semen (about 3 ml) by a series of rapid muscular contractions accompanied by sensations of pleasure.
Does emission and ejaculation require mechanical stimulation?
No, erection and ejaculation can occur in absence of mechanical stimulation, non-sexual erection occurs in REM sleep
Define erectile dysfunction. Is it defined as a form of infertility?
The inability to achieve or sustain an erection, disrupts the sex act for both men and women. It is not defined as infertility.
What are the 4 causes of erectile dysfunction?
- Diabetes: damage to nerves and vascular
- Cardiovascular disease and atherosclerosis: ED can be an early warning sign of CVD
- Neurological disorders: MS, Parkinson’s, stress, anxiety
- Various drugs, alcohol and tobacco
What is the primary treatment for male ED? Describe the mechanism.
Sildenafil (Viagra) and other PDE5 inhibitors blocks the enzyme PDE5, which converts cGMP to GMP. This activates myosin light chain phosphatase and increases SR Ca2+ reuptake. Reducing the activity of vascular smooth muscle in the body.
Female sexual dysfunction is commonly what? What are 3 treatments?
Low sexual desire.
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Flibanserin (Addyi) helps restore prefrontal cortex control over the brain’s motivation/ reward pathways that enable sexual desire
- Activates the serotonin 1A receptors, increasing NE and dopamine release
- Androgen therapy: given to post-menopausal women, no FDA approved ones
- Bremelanotide, a synthetic hormone given via injection that acts in the hypothalamus, where it targets the melanocortin receptor, believed to be involved in upregulating a woman’s sexual response to appropriate cues
One disadvantage of sexual intercourse for pleasure rather than reproduction is the possibility of _____.
An unplanned pregnancy
What are the 3 categories of contraceptive practice? Which is the most effective?
- Abstinence
- Sterilization (most effective)
- Interventional methods
Define abstinence.
The total avoidance of sexual intercourse, or avoidance at times of expected fertility (cyclical abstinence)
What are the two forms of sterilization for men and women? Why is it recommended that it is only performed when an individual does not want kids?
Tubal ligation (females) or vasectomy (males). Sterilization is not easily reversible but sometimes can be, so it is recommended that the risk isn’t taken.
How does tubal ligation affect the menstrual cycle?
The menstrual cycle still occurs, the egg just gets stuck.
What are the 3 categories of interventional methods?
- Barrier methods
- Implantation prevention
- Hormonal treatments
Give 3 examples of barrier methods. Why do the ones for women have lower rates of pregnancy in women who haven’t delivered a child?
- Sponge
- Cervical cap
- Condoms
Women who haven’t delivered a child have a tighter cervix.
Describe implantation prevention. Give the primary method and its side effects.
Do not prevent fertilization but rather prevent the implantation of a fertilized egg in the uterine wall. Include intrauterine devices (IUD) as well as chemicals that change the properties of the endometrium (progesterone causing an inflammatory response and increased thick mucus)
IUD: plastic devices (some wrapped in copper) that create a mild inflammatory reaction in the endometrium that prevents the implantation of a fertilized egg as well as kill sperm. Side effects range from pain and bleeding to infertility caused by pelvic inflammatory disease and blockage of the fallopian tubes.
Describe how hormonal treatments work. Give 5 examples of current treatments.
Techniques for decreasing gamete production depend on altering the hormonal environment of the body.
- Phytoestrogen pills (the pill), administered daily
- Progesterone injection (monthly)
- Vaginal ring (monthly)
- Back of arm implant
- Transdermal patch
Hormone treatments consist of various combinations of what 2 hormones? How do these hormones work to prevent pregnancy? What 2 things does this result in?
Estrogenandprogesterone, which inhibit gonadotropin secretion (LH and FSH) from the anterior pituitary necessary for ovulation. This:
- Prevents recruitment of dominant follicle
- Progesterone also thickens cervical mucus
Give the 5 male contraceptives in development and how they work.
- RISUG/VasalGel: reversible inhibition of sperm under guidance, administered via injection of polymer gel into vas deferens. Kills the cells due to pH change, charge (alters cell membrane)
- Male hormone contraception: combination progestin/androgen therapy (NES/T), given via topical gel. Progestin stops HPG axis, androgen supplements the lost testosterone. Initial results are a complete suppression of spermatogenesis in 90% of men
- Vaccines: produce antibodies to ovum or sperm (so far unsuccessful)
- Small molecule inhibition: tries to block driver of testis-specific gene expression and post-meiotic chromatin reorganization, which is only involved in spermatogenesis
- Ouabain analogues: ouabain is an aeropoison, prevents sperm from properly swimming
What are the 5 causes of male infertility (VIRSH)? What do they all center around?
- Hormone related
- Infections: STI’s (chlamydia, gonorrhea), prostatitis, mumps
- Varicocele: defective valves in the veins cause pooling of blood in the testis, heating up the sperm
- Retrograde ejaculation: sperm is directed into the bladder rather than the urethra
- Sperm antibodies: produced by either males or females
All are related to sperm abnormalities
What are the 4 causes of infertility in females?
- Damaged fallopian tubes: STI’s, surgery, pelvic tuberculosis
- Ovulation disorders: PCOS (follicles freeze state, appear cystic), hypothalamic dysfunction, premature ovarian insufficiency (run out of follicles at a young age [< 40])
- Endometriosis: endometrium is located where it is not supposed to be
- Uterine/cervical disorders: cervical stenosis, uterine polyps and fibroids
What are the two forms of assisted reproductive technology?
- In vitro fertilization
- Artificial insemination
When is artificial insemination typically used? What are the 3 types?
Typically used if the male has a low sperm count
3 types:
- Intracervical insemination (ICI)
- Intratubual insemination (ITI)
- Intrauterine insemination (IUI)
What is the process for IVF?
Describe sperm capacitation and its role.
Sperm capacitation involves the sheddding of surface molecules (proteins and carbohydrates) allowing them to rapidly swim and penetrate an egg.
Shedding speeds motility and exposes head proteins that aid in insertion
Sperm capacitation is believed to depend on what?
Substances produced in uterus (albumin, lipoproteins, proteolytic enzymes)
Fertilization of egg by sperm occurs by _____, possibly aided by _____ produced by the egg
Chance, chemical attractants
Describe the acrosomal reaction and it’s role.
Acrosomal reaction: sperm must penetrate loosely connected granulosa cells and the zona pellucida layer, which is accomplished via powerful enzymes that dissolve cell junctions and zona pellucida, allowing the sperm to gain access to the secondary oocyte.
How long does the cleavage process (2 to 8 cells) last?
The entire cleavage process (2 to 8 cells) lasts around 5 days
Blastocyst
- How many cells?
- Structure
- When does it implant after ovulation?
- About 100 cells
- Outer cell layer (trophoblast) surrounding an inner cell mass
- Implants approximately 7 days after ovulation
Upon contact between the endometrium and blastocyst, what occurs?
Trophoblasts proliferate and secrete proteolytic enzymes allowing blastocyst to penetrate wall. Endometrial cells will completely surround the implanted blastocyst.
What do the outer and inner cell layers of the blastocyst form during implantation?
Outer cell layer of blastocyst forms an extra embryonic membrane (chorion), enclosing the embryo and forming the placenta.
Inner cell mass forms embryo and other extraembryonic membranes
Describe the structure of the placenta and how it develops.
Outer layer of cells, chorion, that will become placenta begin to form chorionic villi that penetrate vascularized endometrium.
What is human chorionic gonadotrophin secreted by and what is it’s role? How soon is it produced by the blastocyst?
The chorionic villi of developing placenta secrete human chorionic gonadotropin (hCG). Similar to LH, binds LH receptors of corpus luteum, continues hormone secretion, keeping endometrium intact. It is almost immediately produced by blastocyst.
After ___ weeks of development, the placenta takes over hormone production from the _____, and it degenerates
7 weeks, corpus luteum
What is the sequence of events of the initiation of labor? (3)
- Days prior to onset of labor the cervix softens and ligaments holding pelvic bones together loosens under enzymatic control (estrogen or relaxin)
- At the initiation of contractions fetus repositions lower in abdomen putting pressure on and stretching cervix initiating a positive feedback loop
- Labor then begins with spontaneous contractions
Describe the birth process in terms of the signals, starting with the stimulation of oxytocin neuron cell bodies.
- Oxytocin neuron cell bodies in the hypothalamus increase AP frequency
- Oxytocin is secreted from the posterior pituitary
- Increased uterine contractions (progesterone and oxytocin mix)
- Fetus pushes head deeper into the cervix, increasing stretch
- Increased stretch acts as positive feedback loop, increasing oxytocin release and uterine contractions
- Loop continues until baby leaves womb
What is the role of mammary glands? How many lobes are typically there and what do these lobes produce?
Mammary glands secrete milk during lactation. There are 15-20 lobes, which produce milk substance in alveoli or acini, similar in structure to the sweat glands
_____ causes milk ejection “let down reflex”. Describe this reflex.
Oxytocin. Contraction of smooth muscle in breast (myoepithelial) and uterus.
