7. Coitus & Conception (workbook) Flashcards
what is coitus?
the act of sexual intercourse that results in the deposition of sperms in the vagina at the level of the cervix
from the cervix, where do the sperm travel?
a proportion of sperm enters the uterus and reaches the uterine tubes (fallopian tubes) where they may encounter an ovum (oocyte) released from the ovary
what is conception?
fertilisation of the ovum by a sperm and the subsequent establishment of pregnancy
what does sexual excitement that leads to the act of coitus involve in both sexes?
genital and systemic (e.g. raise in BP) changes in both genders
what are the different phases of genital and systemic changes leading to the act of coitus?
EPOR (like explore) excitement phase plateau phase orgasmic phase resolution phase
what is the climax of sexual excitement in males accompanied by?
ejaculation
immediately after ejaculation, what happens to the semen?
the semen first coagulates due to the action of clotting factors (fibrinogen and vesiculae)
why is the semen required to coagulate>
to prevent the sperms from being physically lost from the vagina
what happens to the semen after coagulation by clotting factors?
it then liquifies by the action of enzymes derived from prostatic secretions (fibrinolysis)
what happens to the majority of the sperms?
doesn’t enter the cervix of uterus - are lost by leakage from the vagina
what happens to the sperm which enter the uterus?
travel a distance of 15-20cm to reach the uterine tube
how long does it take the sperm to enter the uterus (15-20cm uterine tube)?
a few hours
what is transport of sperms to the uterine tube a result of?
probably the result of their own propulsive capacity and the fluid currents caused by the action of ciliated cells in the uterine tract
during the passage of sperms through the uterus to the uterine tube, what happens to the sperm?
the sperm undergo a further series of maturational changes
what are the further maturational changes that a sperm undergoes through its passage in the uterine tube?
capacitation and acrosomal reaction
what does capacitation and acrosomal reaction result in?
results in sperm acquiring a full capacity to fertilise the ovum
where do the sperm maturation changes first begin?
during their transport from the testis to the epididymis
where do sperm maturation changes continue after transport from testis to epididymis?
during their storage at epididymis until ejaculation
can newly ejaculated spermatozoa fertilise an oocyte? why?
newly ejaculated spermatozoa cannot fertilise an oocyte until capacitation has occurred
where does capacitation normally occur?
within the female genital tract, but it can be induced in vitro
what promotes the change in the sperm cell membrane?
removal of a glycoprotein coat
what happens to the tail of the sperm? (the changes)
from waves to whip-like thrashing movement
why does the tail of sperm have to change to whip-like thrashing movement?
to propel the sperm along and the spermatozoa also become responsive to signals from the oocyte
how long does capacitation take?
several hours
what does a capacitated sperm comes into contact with?
oocyte zona pellucida
what happens when a capacitated sperm comes into contact with oocyte zona pellucida?
the membranes fuse and this marks the commencement of the acrosomal reaction
what happens during acrosomal reaction?
the acrosome swells and liberates its contents by exocytosis
what facilitates the penetration of zona pellucida by the sperm?
proteolytic enzymes
how long does it take for proteolytic enzymes to penetrate the zona pellucida?
about 15mins
what are both capacitation and acrosomal reactions induced by?
an influx of calcium and rise in cAMP in the spermatozoa
