Lecture 3 (reproduction) - Exam 5 Flashcards
What is the overview of oogenesis and spermatogenesis?
What are the chromosomes for female and male?
- XX=female
- XY=male
What regulates LH and FSH in male repro?
Hypothalamic GnRH regulates both LH and FSH secretion
What does LH and FSH regulate?
LH and FSH regulate testosterone secretion and sperm production
Fill in
Explain what happens when the environment, drugs and age effect the brain centers for male reproduction. (include the feedback mechanisms)
Testis are the site of what?
Testis is the site of sperm and seminal fluid formation
Leydig (interstitial) cells:
* Where are they located?
* What do they produce?
* What hormone binds to them?
- in interstitium of the testes, between seminiferous tubules
- produce testosterone.
- LH binds to receptors on these cells
Sertoli cells (nurse cells):
* Where are they located?
* What hormone binds to them?
* What do they support?
- located within the seminiferous tubules
- FSH binds to receptors on these cells
- support spermatogenesis
Sertoli cells (nurse cells):
* Contain what receptors? (2)
* produce low levels of what?
* What do they also produce? What does this regulate?
- contain FSH and testosterone receptors
- produce low levels of estradiol
- also produces activin, follistatin, and inhibin that regulate the secretion of FSH.
How are sertoli cells connexted? What do they divide?
Sertoli cells are connected by tight junctions, which divide the intercellular space into a basal compartment and an adluminal compartment.
Where are spermatogina and maturing sperm located? Explain the process
- Spermatogonia are located in the basal compartment and maturing sperm in the adluminal compartment (closest to the lumen).
- Spermatocytes are formed from the spermatogonia and cross the tight junctions into the adluminal compartment; they mature into spermatozoa.
- What is located between the nonproliferating sertoli cells?
- Where does mitosis of the spermatogonia occur?
- The early meiotic cells (primary spermatocytes) move across the junctional complexes into where? What do they do?
- Located between the nonproliferating Sertoli cells are germ cells at various stages of division and differentiation.
- Mitosis of the spermatogonia occurs in the basal compartment of the seminiferous tubule
- The early meiotic cells (primary spermatocytes) move across the junctional complexes into the adluminal compartment, in which they mature into spermatozoa or gametes after meiosis.
How is the Blood-testis barrier (BTB) formed? What is the function of the BTB?
Blood–testis barrier (BTB): formed by tight junctions between Sertoli cells
* Separates sperm from immune system
* Prevents antibodies and other large molecules in the blood from getting to germ cells
* Germ cells are immunologically different from body cells and would be attacked by immune system
MIGHT BE EXTRA-FROM PAST MASTER
What is the process of differenation from spermatogonia (immature) to Spermatoza (mature)?
Spermatocytogeneis (2n to 2n):
1. Spermatogonia (2n) undergoes mitosis
2. Get type A and B spermatogonia-> undergo mitosis again
3. Get primary spematocyte (2n)
Spermiogenesis (2n to 1n):
1. Primary spermatocyte undergoes meiosis 1
2. Get secondary spermatocyte(1n)->do meiosis 2
3. Get early spermatid-> late spermatid-> spermatoza
The hypothalamic-pituitary-testis endocrine axis controls what?
Spermatogenesis
- Where is LH and FSH secreted from? What is it under the control of?
LH and FSH are secreted from the anterior pituitary under the control of GnRH from the hypothalamus.
What does LH stimulate? What does this cause?
LH stimulates Leydig cells to produce testosterone, which diffuses locally into the seminiferous tubules and also enters the systemic circulation.
What does FSH stimulate? what does this cause?
FSH stimulates the Sertoli cells, resulting in the secretion of androgen-binding protein (ABP) into the lumen of the seminiferous tubule
Under the sertoli cells
- ABP increases what?
- FSH also stimulates what? What does this cause?
- ABP increases local concentration of testosterone at the site of spermatogenesis.
- FSH also stimulates the secretion of inhibin from the Sertoli cells, which exerts negative feedback on FSH secretion by the anterior pituitary.
What does testosterone exert?
- Testosterone exerts negative feedback on the secretion of both FSH and LH.
Explain leydig and sertoli cells and their relationship
Leydig cells:
* secrete testosterone into blood and onto seminiferous tubules
* Stimulated by LH from ant. pit.
* Inhibited by excess testosterone
Sertoli cells:
* Secrete ABP to bind and concentrate testosterone in seminiferous tubules
* FSH also stimulates tehe secretions of inhibin from sertoli cells, which has negative feedback to only FSH
What is the spermatic cord?
bundle of fibrous connective tissue containing the ductus deferens, blood and lymphatic vessels, and testicular nerve
Why does the human testes reside in the scrotum?
Human testes reside in the scrotum because of its cooler environment
* Cannot produce sperm at core body temperature of 37°C
* Must be held at about 35°C
What are the three ways to regulate temperature of the testes?
- Cremaster: strips of the internal abdominal oblique muscle
- Dartos fascia: subcutaneous layer of smooth muscle
- Pampiniform plexus: an extensive network of veins from the testes that surrounds the testicular artery and spermatic cord
How does cremater muscle regulates temperature of the testes?
Cremaster: strips of the internal abdominal oblique muscle
* In cold temperatures, contracts and draws testes upward toward body
* In warm temperatures, relaxes suspending testes further from body
How does the dartos fascia regulate temperature of testes?
Dartos fascia: subcutaneous layer of smooth
muscle
* Contracts when cold, wrinkling the scrotum, holding testes against warm body
* Reduces surface area of the scrotum and heat loss
How the pampiniform plexus regulate temperature of testes?
Pampiniform plexus: an extensive network of veins from the testes that surrounds the testicular artery and spermatic cord
* Countercurrent heat exchanger—without the pampiniform plexus, warm arterial blood would heat the testis and inhibit sperm production
* Removes heat from the descending arterial blood
* By the time it reaches the testis, the blood is 1.5° to 2.5°C cooler
What can cause sterility? What is left unaltered?
Prolonged exposure of the testes to elevated temperature, fever, or thermoregulatory dysfunction can lead to temporary or permanent sterility as a result of a failure of spermatogenesis, whereas steroidogenesis is unaltered.
What is the primary sex site and sex acessories?
- Primary: testes
- Accesories: i.e., the epididymis, vas deferens, seminal vesicles, ejaculatory duct, prostate, bulbourethral gland, urethra, penis)
- After formation in the seminiferous tubules, spermatozoa travel where?
- What happens in the epidiymis?
- What accomplishes the movement of sperm?
- travel to the rete testes and, from there, through the efferent ductules to the epididymis
- In epididymis storage, protection, transport, increased motility and maturation of sperm
- Ciliary movement in the efferent ductules, muscle contraction, and the flow of fluid accomplish this movement of sperm.
What is the pathway for erection reflex in males?
- What are the two ejaculatory bodies?
- What is the blood supply and innervation?
- What is around the urethra?
- Corpus cavernosum
- Dorsal vein, artery and nerve
- Urethra is surrounded by corpus spongiosum
What is NO derived from? What does it cause?
- nitric oxide (NO) is derived from the nerve terminals innervating the corpora cavernosa, the endothelial lining of penile arteries, and cavernosal sinuses
- Causes smooth muscle relaxation-> penile erection
What is the psychogenic or reflexogenic pathway?
How is Semen, consisting of sperm and associated fluids expelled?
is expelled by a neuromuscular reflex that is divided into two sequential phases: (1) emission and (2) ejaculation
- Seminal emission moves the sperm and associated fluids how?
- Contraction of the internal bladder sphincter is via what? What does this cause?
- Seminal emission moves the sperm and associated fluids from the cauda epididymis and vas deferens into the urethra.
- Contraction of the internal bladder sphincter (by α1-adrenergic sympathetic stimulation) prevents the ejaculate from traveling up the urethra and into the bladder, known as retrograde ejaculation
What is ejaculation?
Ejaculation is the expulsion of the semen from the penile urethra; it is initiated after emission.
Fill in the innervation
* Emission:
* Secretion:
* Sensory:
* Expulsion:
* Spinal ejaculation (rats):
- Emission: Sympathic
- Secretion: Parasympathetic centers
- Sensory: pudenal nerve afferents
- Expulsion: motor to bulbospongiosus
- Spinal ejaculation (rats): lumbar spinothalamics
- Semen only contains 10% of what? What is the remainder?
- What is the normal volume of semen?
- How many sperm per mL
- semen contains only 10% sperm by volume
- remainder secretions of accessory glands
- normal volume of semen is 3 mL
- 20 to 50 million sperm per mL
Seminal vesicles:
* What are they?
* Empties where?
* Forms how much of semen?
* What does it contain?
* What is it responsible?
- Pair of glands posterior to bladder w sperm
- Empties into ejaculatory duct
- Forms 75% of semen
- Contains fructose (the principal substrate for glycolysis of ejaculated sperm), ascorbic acid, and prostaglandins
- Responsible for coagulation of the semen seconds after ejaculation
Prostate:
* What does it surround?
* How many glands?
* Where does it empty through?
* What does the thin milky secretion includes? What is this responsible for?
- Surrounds urethra and ejaculatory duct just inferior to the bladder
- 30 to 50 compound tubuloacinar glands
- Empty through about 20 pores in the prostatic urethra
- Thin milky secretion (~0.5 mL) includes fibrinolysin, which is responsible for liquefaction of coagulated semen 15-30 minutes after ejaculation, releasing sperm.
Bulbourethral glands:
* Where is it?
* During sexual arousal, what do they produce?
* How does it protect the sperm?
- Near bulb of penis
- During sexual arousal, they produce a clear slippery fluid that lubricates the head of the penis in preparation for intercourse (pre-ejaculatory secretion)
- Protects the sperm by neutralizing the acidity of residual urine in the urethra
What does spermatogenesis produce?
What is spermiogenesis?
- Spermatogenesis produces an abundance of highly specialized, mobile sperm
- spermiogenesis: maturation of the spermatids into sperm cell
- A spermatogonium becomes a mature spermatozoon after going through what?
- How many spermatozoa are produced daily?
- While the immune system normally detects and destroys defective somatic cells, what protects the speem?
- A spermatogonium becomes a mature spermatozoon after going through several rounds of mitotic divisions, a couple of meiotic divisions, and a few weeks of differentiation.
- 200 million spermatozoa are produced daily in the adult human testes, which is about the same number of sperm present in a normal ejaculate.
- While the immune system normally detects and destroys defective somatic cells, the blood–testis barrier isolates advanced germ cells from immune surveillance.
Explain the process of spermatogenesis (picture)
Male germ cells, which undergo extensive morphologic changes in cell shape and, ultimately, meiosis to produce the haploid spermatozoa.
- What does the head of the sperm contain?
- The tail is divided into three regions?
Head:
* Nucleus contains haploid set of chromosomes
* Acrosome—enzyme cap over the apical half of the
nucleus that contains enzymes that penetrate the egg
(acrosome reaction)
Tail:
* Midpiece contains mitochondria around axoneme of the flagella, produces ATP for flagellar movement
What is testosterone converted into in males?
Testosterone is converted to dihydrotestosterone (DHT), the most biologically active androgen, and to estradiol, the most biologically active estrogen (to prevent osteoclast)
What cells produce testosterone and what is it derived from?
Testosterone is primarily synthesized in Leydig cells and is derived from cholesterol, involving many enzymatic steps.
* The adrenal cortex, ovaries, testes, and placenta produce steroid hormones from cholesterol.
* The major steroid produced by the testis is testosterone, but other androgens, such as androstenediol, androstenedione, and DHEA, as well as a small amount of estradiol, are also produced.
What are the different conversions of testosterone in extratesticular sites?
Explain the pathway of hormone release when age, environment and drugs act on the brain centers in females
- Each month a single oocyte (mature egg) develops and is released from where?
- What is a follicle?
- Most follicles in the ovary undergo what? Some develop into what?
- As follicles mature, what also matures? How does this happen?
- Each month a single oocyte (mature egg) develops and is released from one of the ovaries.
- A follicle is the functional structure in which this oocyte develops.
- Most follicles in the ovary undergo atresia; however, some develop into mature follicles, produce steroids, and ovulate.
- As follicles mature, oocytes also mature by entering meiosis, which produces the proper number of chromosomes in preparation for fertilization.
- After rupturing, the follicle becomes a corpus luteum
What does Folliculogensis result in?
in a mature graafian follicle.
Follicular theca cells:
* Under the control of what?
* What does it produce? Where does this go?
- Follicular theca cells under the control of luteinizing hormone (LH)
- Produce androgens that diffuse to the follicular granulosa cells, where they are converted to estrogens via a follicle- stimulating hormone (FSH)-supported aromatization reaction.
Granulosa cell:
* What do they recieve? What do they do with that molecule?
* What do they lack?
- Androgens are diffused to the granulosa cells, where they are converted to estrogens via a follicle- stimulating hormone (FSH)-supported aromatization reaction
- Granulosa cells lack of the enzyme 17α-hydroxylase and cannot convert progesterone to androstenedione (indicated by the X)
Overview of egg and follicle develop
Menstrual cycle
What happens during follucular phase?
- The elevated levels of FSH act on a cohort of follicles recruited 20 to 25 days earlier from the resting pool
- During the midfollicular to late follicular phase, rising estradiol and inhibin from the dominant follicle suppress FSH release inducing atresia in the nonselected follicles.
- The dominant follicle is saved by virtue of its high density of FSH receptors, the accumulation of FSH in its follicular fluid and the acquisition of LH receptors by the granulosa cells
Menstrual cycle
What happens during the ovulatory phase?
- LH surge causes ovulation
- The midcycle surge of LH is short lived (24 to 36 hours) and results from positive feedback by estradiol.
- The mechanism(s) that transforms estradiol from a negative to a positive regulator of LH to induce the LH surge is incompletely understood.
Increase in estrogen (from granulosa cells)-> LH surge-> OVULATION
Menstrual cycle
What happens during the luteal phase?
- As the corpus luteum matures, it increases progesterone production and reinitiates estradiol secretion
- After the demise of the corpus luteum on days 24 to 26, estradiol and progesterone levels plunge, causing the withdrawal of support of the uterine endometrium, culminating within 2 to 3 days in menstruation.
Endometrial cycle
Proliferative phase:
* What does the proliferative phase concides with?
* Under the influence of rising plasma estradiol concentrations, what happens?
* What elongates?
* The endometrium becomes what?
* Estradiol also induces the expression of what?
- Coincides with the mid to late follicular phase of the ovarian cycle.
- Under the influence of rising plasma estradiol concentrations, the stromal and epithelial layers of the uterine endometrium undergo hyperplasia and hypertrophy, increasing in size and thickness.
- The endometrial glands elongate and are lined with columnar epithelium.
- The endometrium becomes vascularized with more spiral arteries developing to provide a rich blood supply to this region.
- Estradiol also induces the expression of progesterone receptors and increases myometrial excitability and contractility.
What happens to increase the power output of sperm?
What is the fertilization window?
Max 3 day window
Explain the process of fertilization (6)
(1) The sperm cell weaves past follicular cells to sperm receptors in the zona pellucida (sperm-binding)
(2) Intracellular calcium rises in the sperm initiating the acrosomal reaction.
(3) Proteolytic enzymes released from the acrosome digest the zona pellucida.
(4) The sperm penetrates the oolemma, stimulating a rise in intracellular calcium in the egg, which initiates the **cortical reaction (block to polyspermy). **
(5) The rise in intracellular calcium initiates the completion of the second meiotic division and generation of the female pronucleus and second polar body.
(6) The sperm head enlarges to become the male pronucleus, which fuses with the female pronucleus.
- What is the maternal and fetal portion of the placenta?
- What is exchanged between the placenta? (picture)
- What carries oxygenated and deoxygenated blood?
- Maternal portion of placenta (decifua basalis)
- Fetal portion of placenta (chorion)
- Oxygenated: umbillical vein and Deoxygenated: umbillical arteries
Explain the process of labor
- Explain how lactation works (picture)
- Suckling inhibits what?
- When does the menstrual cycle resume?
- Suckling inhibits the GnRH pulse generator, which suppresses FSH and LH release and also suppresses the menstrual cycle in most mothers who are breast-feeding.
- Usually resume menstrual cycles about 2 months after giving end of breast-feeding.
