conception Flashcards
4 step sexual response cycle
applies to both sexes
excitement
plateau
orgasm
resolution
excitement
Heightened sexual awareness/arousal and blood flow to erectile tissues (erection of the penis in males; erection of clitoris in females); vaginal and Bartholin’s gland secretions lubricate the female; male scrotum tightens and male secretes a lubricating fluid (bulbourethral glands)
plateau
Intensification of excitement phase responses, plus body responses (increased heart rate, respiratory rate, BP, muscle tension)
orgasmic
Male ejaculates semen; feeling of intense pleasure for sexual partners (orgasm); females may under multiple orgasms in
succession
resolution
Genitalia and body systems return to pre-arousal state; general feeling of relaxation; refractory period for males to repeat the cycle (varying length)
what mediates erection and ejaculation
spinal reflexes
hardening of the normally flacid penis to permit its entry to the vagina
erection
emptying the spem and excessory sex gland secreitons (semen) into the urethra
ejaculation- emmision phase
forceful expulsion of semen from the penis
ejaculation- expulsion phase
how is erection accomplished
engorgement fo the penis erectile tissue with blood as a result of marked parasympatheticaly induced vasodialation of the penile arterioles and mechanical compression of the veins
how is the emmision phase accomplished
sympathetically induced contraciton of the smooth muscle in the walls of the ducts and accesory sex glands
how is the expulsion phase accomplished
motor neuron induced contraction of the skeletal muscles are the base of the penis
where si the erection generating centre
lower spinal chord
how is the erection generating centre triggered
mechanically by touch sensitive glans penis; higher brain centres facilitate or inhibit this spinal reflex
spinal reflexive dialation of the penile arterioles
non adrenogenic neurons release NO to relax the arterioles and blood enters the erectile tisssues
engorgement
vacocongestion
how quickly is erection achieved
5-10 seconds
erection reflex summary
Lower spinal cord is the site of the
erection generating center;
mechanically triggered by the touchsensitive glans penis; higher brain
centers facilitate or inhibit this spinal
reflex
Spinal reflexive dilation of the penile
arterioles; non-adrenergic neurons
release nitric oxide (NO) to relax the
arterioles and blood enters the
erectile tissues
Draining veins are compressed by
engorgement (vasocongestion),
creating a closed system
what does vasocongestion lead to
creating a closed system
what undergoes vasocongestion
draining veins are compressed by engorgement/ vasoconstriction
vascular component of the penis- erection
- Increase in blood flow due to decreased arterial resistance results in some erection
- Venous compression to trap blood volume enhances penile rigidity (tumescence)
tumerscence
penile rigidity
corpus spongiosum
Open system
High flow
Low pressure
Does not impinge on urethra
corpus cavernosum
- Closed system
- Outflow obstructed
- Low flow
- High pressure
remedy for erectile dysfunction
inhibit cGMP breadown to maintain relaxation of corpus cavernosum by inhibiting phosphodiesterase type 5
how is the emisison phase accomplished
Sympathetic control leads to sequential contractions of smooth muscles of the reproductive tract and accessory glands to deliver things to the posterior urethra
what is delivered to the posterior urethra
1) prostate gland delivers fluid
2) epididymis and vas deferens (ductus deferens) deliver spermatozoa
3) seminal vesicle delivers fluid (all combined = semen)
what prevents retrograde ejaculation
Sphincter at the bladder neck contracts to prevents retrograde ejaculation and to prevent urine from being mixed with semen
what triggers nerve impulses that activate
skeletal muscles at the base of the penis
urethra filling with semen
what increases the system pressure in the penis and what does this lead to
Rhythmic contractions increase the system pressure, leading to forcible expulsion of semen outside of the body via the urethra
average semen voluem
1.5-6 ml with many million sperm per ml
what happens when male ejaculation occurs during sexual intercourse with female that has recently ovulated
oocyte fertilization by a single spermatozoan and pairing of the haploid genomes to
form a diploid zygote is the moment of conception
when must fertilization occur
within 24 hrs of oculation
why is semen temporarily clotted
to remain in the vagina it then liquifies to release the sperm
what happens to sperm in the female reproductive tract
Spermatozoa undergo an enhanced maturation process called “capacitation” in the female reproductive tract; they exhibit hypermotility and become competent to fertilize an ovum
what propells the spermatozoa to the oviduct
Spermatozoa are also propelled to the oviduct by contractions of the female reproductive tract
what helps spermatozoa and oocyte meet
evidence of chemo attractants bw the two
how many sperm reach the ovum
very few
what causes acrosome reaction anad what is it
Physical binding of sperm head with zona pellucida (ZP) leads to the
“acrosome reaction” and acrosomal enzymes are released to drill through the ZP
what happens when spermatozoan fuses its plasma membrane with the oocyte membrane
its nucleus is released into the cytoplasm
what does sperm fusion trigger
ca signalling cascade in the oocyte cytoplasm which triggers;
a) Triggers the completion of MII
b) Releases cortical granules into the space between the membrane and ZP; inactivates ZP binding proteins (blocks polyspermy)
when does conception occur
Within an hour, the oocyte and sperm nuclei fuse to form a diploid zygote
what happens as acrosome drills throug the ovum membrane
its acrosomal membrane becomes disrupted
IVF female oocyte fertilization
stimulated by exogenous hormone sequence
ivf
Collection of ovulated oocytes (stimulated by exogenous hormone sequence in the female) and semen from separate partners
* Fertilization (conception) under lab conditions;
* Monitor the early embryo development and selection for re-implantation in the prepared uterus (secretory phase of the cycle; prepared endometrium + hormone administration to be sure)
ICSI
Direct injection of the spermatozoan nucleus into an isolated MII oocyt
ART
assited reproductive technologies
therapeutic option for heterosexual couples experiencing infertility, and a fertility
option for same-sex couples, surrogate pregnancies, etc.
