reproduction in humans Flashcards
how is a human formed
through sexual reproduction
male gamete fuses with the female gamete forming a zygote
what are the female gametes
egg
made in the 2 ovaries
ovaries
organs that produce female gametes (egg)
oviducts
tubes leading from the ovaries to the uterus; also known as fallopian tubes
uterus
the organ in which a fetus develops before birth; also known as the womb
has thick walls made of muscle
size of fist
can stretch when woman is pregnant
lining of uterus contains large spaces filled with the mothers blood
cervix
a narrow opening leading from the uterus to the vagina
guards the uterus narrow opening with muscles
vagina
opening from the uterus to the outside of the body
testes
sing. testis
organs in which the male gamete (sperm or spermatoza) are made
scrotum
the sac that contains the testes
2 sacs
sperm duct
a tube that transports sperm from the testis to the urethra
join up from the testes with the urethra just below the bladder
penis
organ containing the urethra, through which urine and sperm are carried
prostate gland
organ that produces a nutritious fluid in which sperm are transported
where sperm duct joins with urethra
makes a fluid called semen which the sperm can swim in
eggs in woman
eggs are being formed before she is born
at birth, she has thousands of partly developed eggs inside her
when a girl reaches puberty
some of these eggs begin to mature, usually one at a time
ovulation
the egg bursting from the ovary and into the funnel at the end of the oviduct
happens once a month in a woman’s reproductive life
epididymis
part of testis where sperm is stored
sperm
developed from the cells in the walls of the tubules
made continually through puberty and onwards
production is very sensitive to heat
if too hot the cells will not develop into sperm
thats why the testes are outside the body -> colder
can only swim at a rate of 4mm per min
what type of cells are eggs and sperm
haploid cells
a single set of 23 chromosomes in its nucleus
how are eggs and sperm cells made
when cells in the ovaries and testes divide by meiosis
flagellum
plural: flagella
a long whip-like tail structure found on sperm cells, used for swimming
acrosome
a structure containing digestive enzymes, in the head of a sperm cell
fertilisation
- after ovulation egg is caught in funnel of oviduct
- slowly, egg travels to the uterus
- cilia lining the oviduct help sweep it along.
- muscles of the wall of the oviduct also help it move, by gently ripling
- if egg is not fertilised by a sperm in 8-24 hours, it dies
- this means the sperm must reach the egg while it is still near the beginning of the oviduct for fertilisation to be successful.
- when sperm reaches jelly coat of egg, acrosome is activated
- acrosome released digestive enzymes that digest the jelly coat
- only the head of the sperm goes into the cytoplasm, flagellum is left
- as soon as the sperm enter the egg, the egg membrane and jelly coat become impenetrable , so that no sperm can get in
- nucleus of sperm fuses with the egg (fertilisation)
- unsuccessful sperm die
how does sperm travel out of the penis
when muscles in the walls of the tubes containing sperm contract rythmically
wave of contraction begins in the testes, travels along the sperm ducts and into the penis
sperm are squeezed along the tubes, out of the man’s urethra and into the woman’s vagina
abt 1 mil are deposited, so more likely one will make it
semen
made in the prostrate gland
contains sugars, and other nutrients to provide the sperm with energy.
semen is deposited at the top of the vagina, near the cervix
implantation
attachment of the embryo (which has 16 or 32 cells) to the lining of the uterus
uterus is thick and spongy lining, embryo sinks into it
embryo
a balls of cells that is produced by repeated division of the zygote
placenta
as the embryo grows in the uterus wall so does the placenta.
its an organ that connects the growing fetus to its mother, in which the blood of the fetus and mother are brought close together so that materials can be exchanged between them
soft, dark red
has finger like projections called villi
villi fit closely to the uterus wall
embryo’s life support system
contains capillaries filled with fetus’s blood
mother and fetus blood dont mix, but bc of the placenta wall being thin they are brought close together
fetus
after 11 weeks the embryo has developed most of its organs
umbilical cord
a structure contaning blood vessels that connects the fetus to the placenta
arteries take blood into the placenta, vein returns the blood to the fetus
what diffuses from the mothers blood into the fetus’s blood
oxygen and dissolved nutrients dissolve across the placenta wall into the fetus’s blood and are then carried along the umbilical cord to the fetus.
what diffuses from the fetus’s blood into the mother’s blood
carbon dioxide and other excretory substances diffuse to the mother blood through the placenta wall
what can also cross the placenta wall
toxins, such as alcohol and carbon monoxide
some pathogens such as viruses that cause rubella can also pass across the placenta to the fetus
how big is the placenta by birth
12cm in diameter, 3 cm thick
amniotic sac
a tough membrane that surrounds a developing fetus in the uterus
makes amniotic fluid
amniotic fluid
liquid secreted by the amniotic sac which supports and protects the fetus
fetus floats in it and is able to move freely which helps the muscles and skeleton develop correctly
when fetus is ready to be born
after nine months
contractions of muscles in the uterus wall often cause the amniotic sac to break
releasing the amniotic fluid (water breaking) flows into the vagina
what are the functions of the reproductive organs affected by
hormones
main male: testosterone, secreted in testes
main female: oestrogen and progesterone, secreted in the ovaries
adolescence
quantity of testosterone increases
when a person approaches sexual maturity
male: sperm produced
female: ovulation
puberty
the time at which sexual maturity is reached
what does oestrogen do
causes breasts, pubic hair to grow and hips to widen
what does testosterone do
growth of facial hair, pubic hair, broadening of shoulders, general muscular development and deepening of the voice.
follicle
a structure within an ovary, in which an egg develops
menstruation
the loss of broken down uterus lining through the vagina
abt 5 days
before egg is released…
uterus wall becomes spongy and think with lots of blood vessels
what are the recurring events of the menstrual cycle controlled by.
4 hormones
oestrogen
progesterone
FSH
LH
where are FSH and LH secreted
by a small gland attached to the base of the brain called the pituitary gland
what does FSH do
follicle stimulating hormone
causes a follicle to develop in the ovary with a developing female gamete inside it
corpos luteum
a structure that develops from the empty follicle after an egg has been released from an ovary; also known as a yellow body.
what does LH do
luteinising hormone
causes ovulation to happen
sexually transmitted infections
STI
are infections caused by bacteria or viruses that can be passed from one person to another during sexual contact.
HIV
AIDS
AIDS
acquired immune deficiency syndrome
caused by HIV
destroys white blood cells and therefore reduces the ability of the immune system to defend against other pathogens
usually dies of several illnesses
HIV
human immunodeficiency virus
infect white blood cells in a type T cells
over a long period of time
slowly destroys T cells
several years after infection with the virus the T cells are so low they cant defend against pathogens
abt 10 year after initial infection, an untreated person develops AIDS.
T cells
strongest defense against pathogens
preventing HIV transmission
no danger of:
talking
shaking hands
drinking from the same cups
only become infected through direct contact with body fluids.
HIV transmission through sexual contact
HIV can live in the fluid inside the vagina, rectum, urethra.
during sexual contact can easily mix body fluids.
more sexual partners= higher chance
use a condom to prevent or have one sexual partner
HIV transmission through blood contact
transferred directly from one person’s blood to another’s
1970s-1980s transfusions containing HIV.
during child birth blood may come into contact with the baby.
can be reduced if mother takes antiretroviral drugs
hypodermic needles shared- inject drugs.
HIV transmission through breast feeding
if a woman is infected it can get into her breast milk
reduced chances if woman takes antiretroviral drugs during her pregnancy and while breast feeding.
