Human reproduction Flashcards
what does sexual reproduction in humans involve?
the fusion of a male gamete with a female gamete
male gamete
sperm
female gamete
egg
function of testes 2
produce sperm
secrete testosterone
what is the scrotum
a pouch to enclose and protect the testes outside of the body
function of scrotum
has a low temperature needed for sperm production (~35ºc)
epididymus
a tube on the surface of each testis
2 functions of the epididymus
stores sperm
where sperm mature
vas deferens
sperm duct
function of vas deferens
a tube to carry sperm to the urethra
3 associated glands with the male reproductive system
seminal vesicles, prostate gland, Cowpers gland
what fluid do the glands of the male reproductive system secrete
seminal fluid
what is semen made of
when seminal fluid combines with sperm
2 things that seminal fluid provides for sperm
food and a medium through which to swim
urethra
a tube down the centre of the penis
function of urethra
carries semen and urine to the outside of the body
function of penis
places semen in the vagina of the female
dna of sperm producing cells
diploid sperm producing cells
how are sperm cells made
these cells divide by meiosis
when does sperm production occur
begins at puberty and continues throughout the life of man
3 functions of testosterone
formation
development of male sex organs
development of male secondary sexual characteristocs
2 secondary male sexual characteristics
deepening of the voice
facial hair
2 functions of the ovary 2
produces eggs
secretes female sex hormones; oestrogen and progesterone
what stimulates the production of female secondary sexual characteristics
oestrogen
fallopian tube =
oviduct
function of fallopian tube
transfers eggs from ovary to uterus
where does fertilisation occur
the fallopian tubes
uterus=
womb
uterus
a thick-walled muscular organ that encloses and protects the developing embryo
endometrium
soft lining of the uterus wall for nourishment and implantaion of the mebryo and placenta formation
cervix
a ring of muscle at the neck of the womb that separate the womb from the vagina
vagina =
birth canal
birth canal
passage leading from the womb to the outside of the body, lined with mucus-secreting cells
when are oestrogen and progesterone important
in the menstrual cycle and during pregnancy
2 secondary sexual characteristics in females
development of the breasts
widening of the hips
the menstrual cycle
a series of changes that occur in the ovary and in the lining of the uterus every 28 days
menarche
start of cycle at puberty
menopause
end of cycle (45-55 years old)
days 1-14
an egg is produced by meiosis in 1 ovary
where does the egg develop
in a fluid-filled sac called the Graafian follicle
what do Graafian follicle cells secrete
oestrogen
around day 14
ovulation occurs
what happens at ovulation
the Graafian follicle bursts and releases the egg into the body cavity
days 15-28 (after ovulation)
the remains of the Graafian follicle develop into the corpus Luteum (yellow body)
what does the corpus luteum secrete?
progesterone and oestrogen
if the egg is not fertilised and implantation does not occur what happens
the corpus luteum begins to break down and stop secreting oestrogen and progesterone
what happens when the levels of oestrogen and progesterone fall?
the cycle is brought to an end and a new cycle begins in the other ovary
4 differences between egg and sperm
sperm: have tails can move may have a y-chromosome are smaller
outside of the membrane of a human egg
zona pellucida
days 1-5 uterus
menstruation occurs, the endometrium breaks down and blood and tissue is shed from the body via the vagina
days 6-28 uterus
the endometrium becomes thick and vascular to prepare it to receive an embryo
day 28 uterus
if fertilisation does not occur and an embryo is not implanted in the lining of the uterus, menstruation begins, this marks the first day of a new cycle
what does the pituitary gland secrete for females
FSH and LH
what do the ovaries secrete
oestrogen and progesterone
FSH stands for
follicle-stimulation hormone
2 functions of FSH
stimulates the formation and development of the graafian follicle and the egg in the ovary
stimulates the secretion of oestrogen by the follicle cells
3 functions of oestrogen
stimulates the lining of the uterus to repair and become thick and vascular
stimulates the secretion of LH
inhibits the secretion of FSH so that no more follicles develop (negative feedback)
LH stands for
luteinising hormone
3 functions of LH
stimulates ovulation
stimulates the development of the corpus luteum from the remains of the graafian follicle
stimulates the corpus leuteum to secrete progesterone (and small amounts of oestrogen
3 functions of progesterone
maintains the thickening of the endometrium
inhibits the secretion of FSH so that no more follicles develop during the cycle (negative feedback)
inhibits the secretion of LH
pathway of the egg
ovary (graafian follicle) - body cavity - fallopian tube
pathway of sperm
testis - epididymus - vas deferens - urethra - vagina - cervix - uterus - fallopian tube
2 things that the sperm do when it reaches an egg
the acrosome releases enzymes to break down the membrane around the egg
the sperm head passes through the membrane of the egg, the tail is left outside
what does the egg form once the sperm is in
it forms an impermeable barrier or fertilisation membrane to prevent entry of more sperm
fertilisation
when the sperm and egg nuclei fuse to form a diploid zygote
how long can sperm live in the female system ?
up to 7 days (average 2 - 3 days)
how long can eggs live for?
up to 48 hours after ovulation
time when fertilisation is likely to occur
the fertile time
how many chromosomes does the fertilised egg have?
46 - 23 from egg and 23 from sperm
how does the fertilised egg move along the fallopian tube towards the uterus
by cilia and muscular contraction
what occurs at the fertilised cell moves
it divides by mitosis and cleavage of the cytoplasm to form a solid ball of cells called the morula
what does the morula do?
the morula moves into the uterus and forms the blastocyst
2 parts of the blastocyst
the outer layer - trophoblast (forms part of the placenta)
the inner mass (forms the embryo)
3 differences in pregnancy to a normal cycle
corpus luteum keeps growing and produces oestrogen and progesterone
endometrium stays thick
menstruation does not occur, menstrual cycle stops
where does the blastocyst stick to?
the endometrium
what do trophoblast cells do?
they produce enzymes that allow the blastocyst to digest its way into the endometrium
implantation
the embedding of the blastocyst in the endometrium
when does implantation occur
about 7-10 days after the implantation
when is the woman considered to be pregnant?
once fertilisation has occured
high levels of progesterone and oestrogen during pregnancy do what?
maintain the growth of the endometrium and the menstrual cycle stops and inhibit secretion of FSH so that eggs are not produced during pregnancy
