Reproductive System Flashcards
What is sex?
Need 2 individuals
produce germ cells which fuse to produce offspring
What is a characteristic of early fetal life with regards to the gonads?
during early fetal life, gonads are undifferentiated
How does embryonic sex differentiation occur?
Primordial germ cells form, which circulate in vasculature, and migrate through the tissues, they colonize on the genital ridge to form indifferent gonads
main form of differentiation - gene differentiation
- expression of genes in area of Y chromosome (sex determining region)
- testis differentiation factor is the gene that develops the testis
- default is female
What parts do testis and ovaries originate/differentiate from?
cortex -> ovary
medulla -> testis (through transient expression of genes testis differentiation factor (TDF) coming from sex determining region Y (SRY))
What is the main difference between the two chromosome composition for males and females?
Male - XY
Female - XX
What is specialized about birds chromosomes?
In males it is two XX’s and in females it is XY’s
TDF?
testis differentiation factor is the gene that develops the testis, female is the default
What is located beside the genital ridge?
Wolffian duct (will turn into male organs)
Mullerian duct (will turn into female organs)
Are both ducts present beside the genital ridges before differentiation?
Yes, both the wolffian duct (male) and mullerian duct (female) are present in the embryo initially
In what case is TDF not expressed (in the case of a female)?
If there is no Y chromosome, TDF is not expressed
Draw the main diagram from repro I
Draw
Refer to slides
How many/what are the centers does the hypothalamus have that contain GnRH neurons?
2 centers
Tonic center: basal secretion of GnRH
Surge center: ovulatory cycles and female behaviour
During sex differentiation in the perinatal period, what happens in the brain for both females and males?
Males:
Estradiol is released by the placenta and embryonic adrenals, the estradiol binds to carrier in the blood and doesn’t enter the brain
Testosterone is released by the embryo testes diffuse into the brain where it is converted to estradiol
Presence of estradiol in the brain inactivates the surge center = male brain
Females: No presence of estradiol (since testosterone is not being produced and it cannot convert to estradiol since it doesn’t exist) the surge center will remain
What is the major function of the male reproductive system?
Produce and deliver spermatozoa to the female
What are the testis the site of?
Spermatogenesis
What is the function of the epididymis?
Final maturation of sperm, stored in tail of epididymis
What is the sperm mixed with?
Excretion of accessory glands and delivered out of the penis into the female reproductive tract
Draw out the steps to overall sperm production
refer to slides Repro II
What is the ideal temperature for testes?
Need to be kept 4-6 C below core temperature for spermatogenesis (why they hang out of the body)
When are testes dropped?
during late gestation or early life
How are testes dropped?
drop via inguinal canal in scrotal sac, some cases where testes cannot descend due to malfunction in these things
How are the testes temperature controlled in later life?
controlled by veins of the pampiniform plexus (in spermatic cord) forming a countercurrent heat exchanger, veins wrapped around the arteries to lower temperature
Where are testes located?
scrotum
What is the scrotum?
Skin sac from the abdominal cavity with a layer of smooth muscle (tunica dartos)
What is present on the inside of the scrotum?
Layers of connective tissue (scrotal fascia and parietal vaginal tunic)
What is covering the testes?
A layer of vascularized connective tissue (tunica albuginea and visceral vaginal tunic) that projects septa in the testes, smooth muscle cover the septa (help move immature sperm)
What are the ways of moving the testes closer or further from the body to maintain temperature?
Under skin (tunica darcas) - smooth muscle that will contract/relax to move the testes
In between parietal/visceral vaginal tunic that allows for further movement
Where are seminiferous tubules located?
Lobule of the testes
Label the testes diagram
slide 10 of repro II
What are the two major parts of the testes
seminiferous tubules and the interstitium
What are the seminiferous tubules?
Site of sperm production. Ducts collect sperm to rete testis in the center = tubes that bring the sperm to the epididymis
What is the interstitium (between seminiferous tubules)
composed of connective tissue, nerve, blood vessels, and leydig cells which produce testosterone
Label the sperm transitioning between the interstitium and seminiferous tubules
Slide 12 Repro II
What are the differences between a boar reproductive tract?
- testis structure similar to bull - more pronounced interstitium (leydig cells produce wider array of angrodens plus estrogens)
- testis location against the abdominal cavity reduces efficiency of heat exchange
- large seminal vesicles - large volume of ejaculate
- large bulbourethral glands - gel portion
- copious ejaculate - prolonged ejaculation
- smaller sperm reserves
Label the male repro diagram
slide 16 repro II
understand the diagram showing the multiplication of cells during spermatogenesis?
slide 21 repro II
What are the steps to meiosis?
- interphase: replication of DNA
- prophase I
- leptotene: condensation of chromatin
- zyogotene: pairing of homologues (forming tetrad)
- pachytene: crossing-over and recomb
- diplotene: synaptonemal complexes dissociate
- diakinesis: chiasma disappear and homologues begin to repel
- metaphase I: homologue centromere binds to spindle fiber
- anaphase I: homologous pairs separate and begin to move
- telophase: chromosomes migrate to each pole, cell division. 1 chromosome of pair in each cell
- prophase II: spindle fibers rearrange and chromosomes recondense
- metaphase II: chromosomes align along spindle equator
- anaphase II: sister chromatids separate and move to opposite poles
- telophase II: daughter cell nucleus has one set of chromosomes
What is the function of sertoli cells?
blood testis barrier. provide nutrients and several factors to control spermatogenesis
pump fluid during final maturation of sperm
What is a specialized feature of sertoli cells?
basal/luminal and adluminal compartments
What do sertoli cells produce?
androgen binding protein and inhibin
What do sertoli cells express?
FSH receptors (regulated by FSH)
What is spermiogenesis in contact with?
sertoli cells
What are the steps to spermiogenesis?
- nuclear condensation
- formation of the acrosomal cap (derived from golgi)
- development of a tail
- the distal centriole provides a template for accretion of cytoskeletal elements comprising the contractile lattice of the tail
- mitochondria become concentrated into the sheath of the middle piece
Label the sperm diagram
Slide 29 repro II
What are leydig cells where are they located?
interstitial cells that are highly perfused - located in the spaces between tubules
What do leydig cells synthesize
androgens - testosterone
What do leydig cells express
LH receptors
What are the stages of the motility of the sperm in each part of the pelvic urethra?
Head of the epididymis: immotile infertile
Body of the epididymis: Acquisition of potential to be motile fertile
Tail of the epididymis: upon dilution the sperm are motile and fertile
Sperm in which part of the tail of epididymis can be transported to ejaculatory position?
Distal tail
What are the accessory glands of the male reproductive tract?
Ampular gland, vesicular glands, prostate, bulbourethral gland
What is function of ampular gland?
Absent in boar/dogs, elargement of the ductus defferent
What does the vesicular gland secrete?
Fructose (sperm energy), vitamins and prostaglandins (motility and survival), proteins for coagulation
What does prostate gland secrete?
alkaline substance to enhance motility
What does bulbourethral gland secrete?
Alkaline substances to neutralize acidity and mucus to lubricate vagina during copulation
How many days does it take for spermatozoa to be transited through the system?
Spermatocytogenesis (spermatogonia to spermatids) - 47 days
Spermiogenesis (spermatid to spermatozoan) - 14 days
Spermatogenesis - 61 days (4.5 cycles)
epididymal transit - 10-12 days
What are the steps to arousal?
- sensory stimulation (optic, olfactory, tactile and auditory)
- stimulation of nerves in the supraoptic and paraventricular nuclei
- release of oxytocin from the posterior pituitary
- contraction of smooth muscle in distal tail of epididymis and ductus deferens
- transport of spermatozoa into an ejaculatory position
What are the steps to ejaculation?
- intromission
- sensory stimulation of glans penis (temperature and pressure)
- sudden and powerful contraction of urethralis, bulbospongiosus and ischiocavernosus muscles
- expulsion of semen
What are the ingredients used for cryopreservation of ejaculate?
Nutrient
- egg yolk
- whole homogenized milk
Buffer
- citrate
- sodium phosphate
Antimicrobials
- penicillin/streptomycin (bacteria)
- minosin (mycoplasma)
Cryoprotectant
- 6-12% glycerol (if to be frozen)
Draw out the endocrine control in the male reproductive system?
slide 44 repro ii
What is the structure of GnRH?
decapeptide
How is GnRH released, how does it travel?
Released in a pulsatile manner in the median eminence
Travels via the portal blood system to the anterior pituitary
What is the end of the feedback loop for GnRH?
In the hypothalamus, GnRH neurons receive information about internal and external stimulus
What type of receptor are GnRH receptors? and how do they work?
G protein-coupled receptors, upon binding, can stimulate both Galphaq and Galphas, in pituitary, leads to release/synthesis of gonadtropins (LH and FSH)
What tissues are GnRHRs present in?
Pituitary, ovary, prostate and placenta
What type of proteins are LH and FSH?
glycoprotein hormones composed of 2 subunits: common alpha subunit and specific beta subunit
What are LH and FSH produced by?
Gonadotropes
What are the characteristics of the LH receptor?
G protein coupled receptor
activates Galphas = increase in cAMP
binds both LH and hCG
What are the characteristics of the FSH receptor?
G protein coupled receptor signaling via Galphas
What type of protein is inhibin and activin?
glycoprotein composed of 2 subunits
What is inhibin produced by?
sertoli cells in males and granulosa cells in females
What does inhibin inhibit?
FSH
What does activin stimulate?
FSH
What do inhibin and activin act in conjunction with?
GnRH
What are gonadal sex hormones derived from?
stepwise conversion of cholesterol, lipophylic with nuclear (intracellular) receptor
What does the steroid derivation into sex hormones depend on?
Type of steriod depends on the presence of specific enzyme substrate in the cell
What is the stepwise conversion of estradiol?
Pregnenolon
Progesterone
Testosterone
Estradiol - aromatization of the ring by the enzyme aromatase
What are the type of receptors used in steroids?
NHRs. effect on gene transcription
How many target organs are there for sex steroids?
Many target organs, since steroids diffuse in virtually any cell of the body receptors are widely distributed
What type of receptor does testosterone use?
androgen receptor
What are the receptors for estrogens?
2 receptor types:
ERalpha - stimulates txn
ERbeta - inhibits txn
main difference - locations, effects of drugs will depend on ability to bind and activate ER alpha or ER beta
What is a specialized feature of estrogen receptors?
receptors require coactivators/regulatory molecule to mediate their actions on target gene promoters
What is the missing link in the GnRH loop?
Kisspeptin, GnRH neurons do not express ERs but kisspeptin neurons do
What are the external reproductive organs of the female repro system?
vulva and clitoris, heat signal
What are the internal reproductive organs of the female repro system?
Ovaries - oocyte formation
Oviducts - transport of oocyte + fertilization
Uterus - transport of spermatozoa, implantation, support for fetal development
Cervix - passage between uterus and vagina
Vagina - receptacle for male penis
What are the broad ligaments made of?
mesovarium + mesosalpinx + mesometrium = broad ligament
Label the female repro system diagram
Slide 4 repro IV
What are the external genitalia of the female repro system and what re their functions?
Labia major (female equivalent to scrotum) + labia minor = vulva
- closure that minimizes entrance to vagina
- labia can swell with blood during estrus (visual signal) (pigs/dogs)
Clitoris - erectile tissue equivalent to the male penis, high density of sensory nerve endings
Urethra opening
Vaginal opening
What is the main function of the vagina
Receive the penis during copulation, inner part is highly secretory (close to cervix)
Resident bacteria on surface secrete lactic acid, resistance to infection
What is the outer part of the vagina made up of?
stratified squamous epithelium resistant to mechanical stress, keratinization is some species
Label the diagram of the vagina
Slide 9 repro IV
What is the function of the cervix?
Marks the separation between vagina and uterus, regulates passage from/to uterus, protects fetus during pregnancy