Reproduction Flashcards
External/ Internal male genitals
- External: penis, prepuce, muscles
- Internal: testes, epididymis, ductus deferens, accessory seminal glands
Male reproductive system: spermatogenesis, ejaculation, development + maintenance of 2ndary sexual characteristics.
Endocrine control: androgens synthesis (hypothalamopituitary control)
Neural control: erection + ejaculation
Hormones
- Testosterone: produced by Leydig’s cells, controlled by LH-RH + LH, through hypothalamopituitary axis.
Seminiferous tubules -> ABP, Sertoli cells + metabolized to DHT -> maintains spermatogenesis. - Sertoli cells: spermiocytogenesis + spermiomorphogenesis
- FSH: with sertoli cells => ABP production + spermatogenesis
- ABP: produced by sertoli cells, -> epididymis for maturation of spermatozoa
- Inhibin: paracrine effect, autocrine + endocrine action
- MIF: development of male gender, (-) feedback on FSH, (+) feedback on LH
- LH: endogenous testosterone production
- Acrosin: for penetration of oocyte
Spermatogenesis
FSH + testosterone can reach layer of germ cells, 60-70 days.
1. Spermatocytogenesis: primordial germ cells -> haploid spermatid
2. Soermiomorphogenesis: spermatid -> spermatozoa
- Golgi phase: golgi complex -> acrosomal granule -> acrosomal vesicle
- Cap phase: acrosomal cap-over nucleus, chromatin condenses, flagellum develops from axoneme
- Acrosomal phase: spermatid re-orientates, further condensation of chromatin. Connective piece: flagellum -> nucleus
- Maturational phase: residual cytoplasmic body sheds, cell linkage lost, cell -> lumen of tubule.
Final maturation: motility of flagellum + lecithin cover.
Blood-Testes barrier
Junction bw Sertoli cells: separates developing spermatozoa + immune system => prevents testicular cells from contacting lymphoid tissue.
Autoantigenic cells:
1. Immunological tolerance by “leakage” of sperm antigens
2. Immunomodulatory mechanisms within testes
3. Immunomodulation distal to testes (T-suppressor cells in epididymis, seminal plasma).
Male Accessory Sexual glands
Seminal plasma => vehicle for spermatozoa
Semen = plasma seminalis + spermatozoa
1. Seminal vesicles: smooth m elements, lobes (ca), secretion: fructose, citric acid, phosphate, prostaglandins (=> uterine contr)
Role: energy supply, activation of spermatozoa
2. Prostate: lobes, secretion: glycoproteins, Zn, Cl
Role: induction of sperm mobility
3. Cowper’s gland = Bulbourethralis: lobular tubuloalveolar bodies (ca), smooth m walls, secretion: acidic liquid
Role: damages sperm cells, decreases motility, cleaning urethra, barrier => prevention of sperm flowing back (su)
4. Ampulla: tubuloalveolar gll (su), ampulla
Bull -> fructose + citric acid
Stallion -> high [ergothionine] + low [inositol]
Vitality + Motility of spermatozoa
Epididymis: high partial P of CO2 + high density of sperms => “dormant” state
Activation: fructose + high partial P of O2
2 types of mvms: mass mvm (diffusion), individual mvm (non-directional specific way)
- Female reproductive -> rheotaxis (semen -> tuba), capacitation: pH + enzymatic => maturation proc for spermatozoa
Male sexual reflexes
- Erection: Swelling of penis + protrusion from prepuce. Duration: period since urethra is rinsed by the secretion of bulbourethral gland.
- Intromission: introduction + intromission -> vagina
Swelling of erectile t (via pudendal a), ensure venal return from erectile t. - Ejaculation: afferentation from mechanical stimulation, during copulatory mvms: aff nn -> lumbar center => ejaculation.
Efferent branches: (a) hypogastric plexus -> S -> ductus deferens + accessory glands. Contractions => propelling of sperm -> urethra
(b) Motor impulse via pudendal n => contr of bulbocavernosus, ischiocavernosus, urethra: transmit ejaculation -> female sexual ducts
Ru: single, synchronized
Others: multiphase, asynchronous steps.
Cycle of uterine tube
Proestrus: increased perfusions, by estrogen => infundibulum becomes rigid, enlargement of the tube (reception of egg)
Metestrus: by progesterone => stop the increased blood flow, accelerated transport of the ovumisthmus is opened
Cycle of uterus
Proestrus + estrus: proliferate phase, due to estrogen, increased blood supply
Metestrus: secretory phase, progesterone, thick mucosa, glands achieve their max secretory capacity
Diestrus: no fertilization, involution phase, supf layer of endometrium dies, elements undergo resorption
Anestrus: resting state, thin endometrium
Cucle of cervix
Proestrus + estrus: follicular phase, tonicity of cervical mm, cervical ducts -> “gate” for the transport of spermatozoa + mucus production
Anestrus: mucus production decrease (separation of cervical duct + outer environment => protection of embryo), if no fertilization => involution phase is terminated => new cycle
Cycle of the vagina
Proestrus + estrus: increased blood supply + thickness, mucus secretion -> copulation + fertilization, increased ratio of keratinized cells => protection from strong mechanical effect of penis
Metestrus + diestrus: progesterone- dominant, hyperemia + swelling decrase, secretion gradually stops
Hormonal changes during estrus
Regulation via the hypothalamopituitary axis.
- Tonic center: GnRH secretion
Patterns of GnRH secretion: tonic releasing phase (ensure plasma levels), pulsatile releasing phase (peak every 24h), preovulatory GnRH surge: neural restructuring => (+) feedback
Estrogen: depends on follicular activity, low after ovulation, P4 on CNS => NO estrus behaviour
- Follicular phase: only 1 reaches follicular rupture. High E2 + low P4 => estrus behaviour
- Luteal phase: PRL + increase P4 levels
- Luteolysis: vena uterine => PGF2 α -> corpus luteum degenerates => corpus albicans => P4 levels drop. Events resulting in luteolysis: oxytocin receptors, production of PGF2 α
- LH surge: => ovulation + formation of corpus luteum. FSH decrease
Decreased P4 + increased E2 => ripening of selected follicle
- Ovulation: rising E2 levels + low P4 levels
Hormones + Hormonal effects of ovary
- Estrogen: 1. Low plasma estrogen levels, 2. Follicles = atretic parallel to the decreasing levels of estrogen, 3. Follicular phase: progesterone levels decrease (luteolysis), high E2 + lack of P4 => estrus behaviour, 4. Estrogen levels decrease + elevation of PRL
- Progesterone: 1. Luteal phase: PRL + increasing plasma P4 => ovulation, 2. Luteolysis: PGF2 α => atrophy of corpus luteum. P4 decrease.
FSH -> synthesis of estrogen + maturation of follicles, increased levels during follicular phase
LH -> synthesis of progesterone + estrogen, receptors (initial phase: theca cells, later: granulosa cells => formation of corpus luteum.
“ Two cells- two hormones”: theca + granulosa cells are independent hormone producing cells, in tertiary follicles their no increase. Basal membr -> barrier (LDL molecules cannot pass, HDL pass).
Elevation of cAMP levels -> increase cholesterol uptake -> pregnenolone -> ER -> progesterone -> aldrostenedione -> granulosa cells => testosterone / estrogen by aromatases.
Fertilization
Ovulated egg -> cumulus-oocyte complex (via fimbriae) -> oviduct (for 3 days) -> ampulla => fertilization
Maturation of spermium = capacitation + acrosome reaction: decapacitating factors are degraded by enzymes => sperm activated => penetration => fertilization:
- Hyaluronidase/ CPE -> dissolves corona radiate
- Acrosin -> penetration of zona pellucida
- Sperm cells -> perivitelline space. Fusion of membranes of 2 cells
- Decreased permeability of zona pellucida -> against polyspermy
- “Zona reaction”: decreases sperms’ accepting ability of ovum
Postfertilization: sperm’s head -> egg’s cytoplasm. Nucleus of sperm disappears => decondensation => chromatin of sperm + egg are encapsulated into a common membrane (pronucleus).
Embryogenesis, Pregnancy
Implantation of blastula -> uterus. Nidation: better supply + beginning of organogenesis.
Pregnancy is maintained by P4 => progesterone inhibits luteolysis (bitch: P4 levels remain high, others: corpus luteum is transformed to CL gravidatis). Early embio secretes interferon => no luteolysis.
- hormones: LH + P4 increase => prep of mammary gland, P4 => safety of embryo, prep mammary gl, Estrogen/oxytocin: inhibits new fertilization, Relaxin: relaxes birth canal for parturition
