human repro Flashcards
what is fertilization
fusion of the nuclei from a male gamete (sperm cell) and a female
gamete (egg cell)
where does fertilization occur
in the oviducts in the females
what are the adaptions of sperm and its function
flagellum (tail) - enables it to swim
contains enzymes in the head region (acrosome) - to digest through the jelly coat and cell membrane of an egg cell
contains many mitochondria - to provide energy from respiration for locomotion
what are the adaptions of egg cells and its function
cytoplasm containing energy - provides energy for the dividing zygote after fertilization
jelly-like coating that changes after fertilization - forms an impenetrable barrier after fertilization to prevent other sperm nuclei from entering the cell
what type of nucleus do gametes have
haploid nucleus
describe the parts of a sperm cell from top to bottom
acrosome
haploid nucleus
midpiece containing mitochondria
flagellum
what is the prostate gland and what does it do
produces fluid called semen that provide sperm cells with nutrients
what is the sperm duct/vas deferens and what does it do
sperm passes through the sperm duct to be mixed with fluids produced by the glands before being passed into the urethra for ejaculation
what is the urethra and what does it do
urethra is a tube that runs down the centre of the penis which can carry urine or sperm, a ring of muscle in the urethra prevents the urine and semen from mixing
what are the testis and what does it do
contained in a bag of skin (scrotum) and produces sperm (male gamete) and testosterone (hormone)
what is the scrotum and what does it do
sac supporting the testes outside to ensure sperm are kept at a lower temperature optimum for their production
what is the penis and what does it do
passes urine out of the body from the bladder and allows semen to pass into the vagina of a woman, during sexual intercourse
what is the oviduct
connects the ovary to the uterus and is lined with ciliated cells to push the released ovum down it, fertilization occurs here
what is the ovary
contains ova (female gametes) which will mature and develop when hormones are released
what is the uterus
muscular bag with a soft lining where the fertilised egg (zygote) will be implanted and develop into a fetus
what is the cervix
ring of muscle at the lower end of the uterus to keep the developing fetus in place during pregnancy
what is the vagina
muscular tube that leads to the inside of the woman’s body, where the males penis will enter during intercourse and sperm is deposited
compare the size of a sperm cell and an egg cell
sperm: 45 nanometers
egg cell: 0.2mm
compare the structure of a sperm cell and an egg cell
sperm: head structure and flagellum, many structural adaptations
egg cell: round cell with few physical adaptations and covered in jelly coating
compare the mobility of a sperm cell and an egg cell
sperm: locomotive
egg: not locomotive
compare the number of sperm cells and egg cells in a human body
sperm: millions produced everyday in huge numbers (around 100 million per day)
egg: thousands of immature eggs in each ovary but only 1 released each month
after fertiliation in the oviduct where does the zygote move to
the uterus
how long does the travel from oviduct to uterus take and what happens to the zygote
This takes about 3 days, during which time the zygote will divide several times to form a ball of cells known as an embryo
where does the embryo finally reach and what is this called
sinks into the uterine lining and is called implantation
what is the gestation period for humans
9 months
when does the development of major organs take place
within the first 12 weeks
how does the embryo get nutrition from the mother
diffusion through the placenta
what does the embryo become after all the organs are in place
once the organs are in place and the placenta has formed the embryo is called a fetus
what is the amniotic sac
what does it contain
what does it do
fetus is surrounded by an amniotic sac which contains amniotic fluid
protects the fetus during development by cushioning it from bumps
what is the umbilical cord, what does it do
umbilical cord joins the fetus’s blood supply to the placenta for exchange of nutrients and removal of waste products
how does the fetus develop in the gestation period
gains the mother’s glucose, amino acids, fats, water and oxygen from the mother’s blood
how is the placenta wall adapted for diffusion
large surface area and thin wall
name the 6 stages of child birth
- Amniotic sac breaks
- Muscles in the uterus wall contract
- Cervix dilates (gets wider)
- Baby passes out through the vagina
- Umbilical cord is tied and cut
- Afterbirth is delivered
how does the placenta protect the baby from toxins
acts a barrier between the baby and pathogens
why should pregnant women avoid smoking
nicotine can pass across the placenta
does the umbilical cord being cut hurt
no as there are no nerves in it only blood vessels
what is afterbirth
The placenta detaches from the uterus wall shortly after birth and is pushed out due to contractions in the muscular wall of the uterus – known as the afterbirth
what are secondary sexual characteristics
changes that occur during puberty as children become adolescents
what are secondary sexual characteristics controlled by
hormones
oestrogen - females
Testosterone - males
what are female secondary sexual characteristics
breasts develop
body hair grows
menstrual cycle begins
hips get wider
what are male secondary sexual characteristics
growth of penis and testes
growth of facial and body hair
muscles develop
voice breaks
testes begin to produce sperm
how long is the average menstrual cycle
28 days
what is ovulation
the release of an egg, occuring about halfway through the menstrual cycle (14th day)
after release, the egg travels down the oviduct to the uterus
what causes menstruation
if the released egg isnt fertilized, the breakdown of the thickened lining of the uterus is stimulated which is what causes the bleeding (menstruation)
how long does the bleeding (menstruation) last
5-7 days
describe the uterine lining from day 1 to day 7
uterine lining sheds and becomes thins
describe the uterine lining from day 7 to 14
lining builds up and thickens
describe the uterine lining from day 14 to 28
lining continues to build up and maintains
describe the uterine lining on day 28
uterine lining sheds and becomes thins as the new cycle begins
what is the menstrual cycle controlled by
controlled by hormones released from the ovary and the
pituitary gland in the brain
what does FSH stimulate and where is it secreted from
stimulates egg maturation in the follicles of the ovary
stimulates follicles in the ovaries to secrete estrogen
stimulates the ovaries to start releasing estrogen
secreted by the pituitary gland and causes the egg to mature in the ovary
what does LH stimulate and where is it secreted from
the pituitary gland secretes LH when estrogen levels have peaked
LH causes ovulation to occur and also stimulates the ovary to produce progesterone
what are the roles of estrogen
-stimulates the uterus to develop a lining (to replace the lining lost during menstruation)
-post-ovulation, inhibits FSH and LH production in the pituitary gland
what are the roles of progesterone
-maintains and thickens lining of the uterus
-inhibits FSH and LH production
when do oestrogen levels rise and until when
what happens when estrogen levels rise
day 1 to 14
uterine wall thickens and egg matures
when do progesterone levels rise and until when
what happens when progesterone levels rise
day 1 to 14
cause the uterine lining to thicken further a fall in progesterone
levels cause the uterine lining to break down (menstruation / ‘period’)
where is oestrogen and progesterone produced
ovary
what is an STI
an infection that is transmitted through sexual
contact
what is HIV
a pathogen that causes an STI
HIV infection could lead to aids
how can HIV be spread
sharing needles with an infected person
blood transfusions with infected blood
mother to fetus through the placenta
mother to baby via breastfeeding
how can HIV be controlled
Limiting the number of sexual partners
having protected sex
getting tested
raising awareness
where is progesterone released from during pregnancy
placenta
corpus luteum
all the steps that occur after fertilization up until the fetus is formed
-zygote divides by mitosis to form an embryo
-hollow ball of cells move to the uterus down the oviduct
through muscle contraction and relaxation
-implants into the uterine lining
-development of placenta
-folicle becomes corpus luteum
-corpus luteum secretes progesterone
-progesterone maintains the endometrium
-progesterone inhibits the release of fsh and hence inhibits menstruation
outline the processes of labour and birth
amniotic sac breaks
amniotic fluid is released
contraction of uterus
cervix dilates
baby passes through vagina
umbilical cord is cut
afterbirth is delivered
how will the composition of a pregnant woman’s blood change as it passes through the placenta
concentration of dissolved nutrients will decrease
concentration of urea will increase
