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biology > 4.1 human reproduction > Flashcards

4.1 human reproduction Flashcards

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1
Q

where are gametes produced?

A

special paired glands called gonads

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2
Q

what are the male gametes and where are they produced?

A

spermatozoa in the testis

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3
Q

what are the female gametes and where are they produced?

A

ova in the ovaries

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4
Q

what is the process of the formation of spermatozoa called?

A

spermatogenesis

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5
Q

where does spermatogenesis take place?

A

in the seminiferous tubules of the testes

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6
Q

what are Sertoli cells and where are they found?

A

found in the seminiferous tubules
secrete a fluid to nourish the spermatids and protect them from the male immune system

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7
Q

what are interstitial cells and where are they found?

A

found in the wallet of seminiferous tubules
secrete testosterone which stimulates spermatogenesis

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8
Q

what are the 2 parts to the head of the sperm called and what is their function?

A

acrosome - a specialised lysosome containing hydrolytic enzymes for fertilisation
nucleus - haploid (n), contains the paternal chromosomes

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9
Q

what are the 2 parts to the mid-piece of the sperm called and what is their function?

A

mitochondria - provide ATP for movement of the flagellum
centrioles - form the sperm flagellum and involved in cell division of the embryo after fertilisation

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10
Q

tail:
what is it called?
what does it do?
what is it made from?

A

flagellum
propels the sperm forwards
made from microtubules (9+2 arrangement)

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11
Q

what happens during sexual intercourse? (5)

A
  • movements of the penis result in contraction of smooth muscle in the walls of the epididymis, vas deferens and the penis.
  • this causes the ejaculation of semen
  • the force of ejaculation propels some sperm through the cervix into the uterus
  • the sperm swim through the uterus into the oviducts by their tails
  • out of the millions deposited only a small number of sperm reach the ovum in the fallopian tube.
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12
Q

what is ovulation?

A

the release of the secondary oocyte from an ovary

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13
Q

what happens after ovulation if no fertilisation has occurred?

A

once the secondary oocyte has been released into the fallopian tube the empty Graafian follicle becomes the corpus luteum. this will regress (break down)

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14
Q

what happens after ovulation if fertilisation has occurred?

A

the corpus luteum secretes hormones which:
- aid embryo development
- prevent further ovulations during pregnancy

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15
Q

where does fertilisation take place?

A

anywhere in the fallopian tube

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16
Q

what are the 3 stages of fertilisation?

A

capacitation
acrosome reaction
cortical reaction

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17
Q

what is capacitation?
what does this do?

A

the removal of cholesterol & glycoproteins from the cell membrane covering the acrosome in the sperm head
increases the permeability of the membrane in front of the acrosome

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18
Q

what is the acrosome reaction?

A

the exocytosis of protease enzymes and the fusion of the sperm membrane and the oocyte membrane

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19
Q

what is the cortical reaction?

A

Ca2+ causes the membranes of the cortical granules to fuse with the oocyte membrane and this secretes its contents to harden the zona pellucida and change it into a fertilisation membrane

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20
Q

what happens after the cortical reaction?

A

meiosis II within the secondary oocyte will re-commence to form an ovum and a second polar body

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21
Q

what happens when the nucleus of the ovum fuses with the nucleus of the sperm?

A

forms a zygotic nucleus (2n)

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22
Q

what does the fertilisation membrane prevent?

A

further penetration of sperm - prevents polyspermy

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23
Q

structure of the secondary oocyte from the outside in

A

corona radiata
zona pellucida
perivitelline space
plasma membrane
cortical granules
cytoplasm
nucleus

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24
Q

what are the corona radiata and what do they do?

A

cells that surround the secondary oocyte and provide it with nutrients

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25
what are the cortical granules and what do they do?
they are secretory organelles with the oocyte, prevent the entry of more than 1 sperm
26
what is oogenesis?
the formation of the secondary oocyte
27
where does oogenesis take place?
in the ovaries
28
when does oogenesis take place?
starts before the birth of a female, in their developing ovaries
29
what processes are involved in oogenesis?
mitosis and meiosis 1 and 2
30
in short terms, what happens before puberty during oogenesis? (4)
- germinal epithelium divide by mitosis to form oogonia and more germinal epithelium cells - oogonia undergo mitosis many times and enlarge to form primary oocytes - germinal epithelium cells divide by mitosis to form follicle cells - primary oocytes are enclosed by a ball of follicle cells and together they form the primary follicles
31
in short terms, what happens after puberty during oogenesis? (3)
- the primary oocytes in the primary follicles undergo the first meiotic division due to the hormones released - a polar body and a secondary oocyte is formed - the polar body will degenerate
32
in short terms, what is the rest of the oogenesis process (after puberty)? (5)
- the secondary oocyte begins the second stage of meiosis but stops at metaphase 2 - the secondary follicle matures into the Graafian follicle - at ovulation the secondary follicle bursts and releases the secondary oocyte into the fallopian tube - the secondary oocyte completes meiosis once fertilisation has taken place - an already fertilised ovum is produced and a polar body which degenerates
33
what is spermatogenesis?
the formation of spermatozoa
34
where does spermatogenesis take place?
in the seminiferous tubules in the testes
35
in short terms, what is the process of spermatogenesis? (5)
- germinal epithelium cells divide by mitosis to form spermatogonia cells - spermatogonia grow and increase in size forming primary spermatocytes - these undergo the first meiotic division to form secondary spermatocytes - these undergo the second meiotic division to form spermatids - spermatids attach to Sertoli cells and mature and differentiate into spermatozoa
36
what does fertilisation result in?
the formation of a diploid zygote
37
what is a blastocyst?
a hollow ball of cells that is formed from the continuous mitosis of the diploid zygote
38
what is cleavage?
when the cell numbers increase exponentially during mitosis in implantation
39
what are the trophoblast?
the cells around the outside of the blastocyst
40
what is an embryo blast?
the distinctive inner cell mass when the trophoblast divides
41
in simple terms, what is the process of implantation?
- the diploid zygote undergoes continuous mitosis - cleavage - blastocyst is formed - the trophoblast divides to make an embryo blast on one side - this process is occurring as the zygote travels down the fallopian tube to the uterus - the blastocyst implants itself into the endometrium of the uterus after about 3 days
42
how long does the diploid zygote undergo continuous mitosis for?
approx. 8-10 days
43
what are trophoblastic villi and what do they do?
finger-like protrusions that develop on the trophoblast which penetrate the endometrium
44
what is the benefit of trophoblastic villi?
increase the surface area for the absorption of nutrients from the endometrium
45
in short terms, explain the development of the placenta
- the trophoblast develops into the chorion - the chorion secretes hCG - cells of the chorion move into the trophoblastic villi to form chorionic villi - the villi gain capillaries which connect to the umbilical arteries and the umbilical vein. - these vessels connect the embryo to the uterus wall via the umbilical cord
46
what does hCG do?
prevent the breakdown of the corpus luteum
47
what is the chorion?
the outer membrane of the embryo
48
what is there an exchange between at the placenta?
maternal blood and foetal blood
49
what components are exchanged at the placenta? give examples of each
gases (oxygen and carbon dioxide) nutrients (glucose, amino acids, fatty acids, glycerol) waste (urea)
50
how does exchange take place between the placenta? (5)
osmosis, active transport, diffusion, facilitated diffusion, pinocytosis
51
what is the mechanism called in which exchange works?
counter current flow
52
what happens in counter current flow?
the maternal blood and foetus blood flow in opposite directions to ensure a concentration gradient is maintained
53
what is rhesus disease?
if a rhesus negative mother has a rhesus positive foetus, her immune system will make antibodies to the protein which results in the destruction of the red blood cells of the foetus
54
what determines if the mother is rhesus negative or rhesus positive?
the rhesus factor - if the protein is present on red blood cells or not (present = positive)
55
what is the role of the placenta?
secrete hCG, oestrogen and progesterone to support pregnancy
56
how does the placenta act as a physical barrier?
protects the foetus capillaries from damage by the mothers high blood pressure
57
what 4 hormones control the menstrual cycle?
FSH LH progesterone oestrogen
58
what does FSH do? (2)
- stimulates follicular growth in ovaries - stimulates oestrogen secretion
59
what does LH do? (2)
- surge causes ovulation - results in the formation of a corpus luteum
60
what does oestrogen do? (3)
- thickens endometrium - inhibits FSH and LH for most of the cycle - stimulates FSH and LH release pre-ovulation
61
what does progesterone do? (2)
- thickens endometrium - inhibits FSH and LH
62
where is each hormone secreted from?
FSH and LH - anterior pituitary gland oestrogen and progesterone- ovaries
63
what are the 4 phases of the menstrual cycle?
- follicular phase - ovulation - luteal phase - menstruation
64
in short terms, describe the follicular phase
- FSH is secreted from the anterior pituitary and stimulates growth of ovarian follicles - the Graafian follicle produces oestrogen - oestrogen inhibits FSH secretion to prevent other follicles developing (negative feedback) - oestrogen acts on the endometrium to stimulate its repair following menstruation (thickens)
65
in short terms, describe ovulation
- midway through the cycle, oestrogen stimulates the anterior pituitary to secrete (LH) - there is a large surge of LH and a lesser surge of FSH (positive feedback) - LH causes the Graafian follicle to rupture from the ovary and release its secondary oocyte
66
in short terms, describe the luteal phase
- the Graafian follicle develops into a slowly degenerating corpus luteum - the corpus luteum secretes high levels of progesterone, as well as lower levels of oestrogen - oestrogen act on the uterus to thicken the endometrium - progesterone maintains the endometrium - oestrogen and progesterone also inhibit secretion of FSH and LH from the pituitary gland which prevents any follicles from developing (negative feedback)
67
in short terms, describe the menstruation
- no implantation = falling FSH and LH levels cause the corpus luteum to degenerate - progesterone levels fall, the endometrium breaks down and is lost during menstruation - FSH secretion is no longer inhibited, and another menstrual cycle is initiated
68
what is the amnion?
when the embryo blast of the implanted blastocyst develops into a membrane
69
what components are in the amniotic fluid? (6)
- water - urea - salts - some protein - trace sugars - sloughed cells from foetus
70
what is the function of amniotic fluid? (5)
- maintains foetus temperature - provides lubrication - contributes to lung development - allows movement (bones and muscle can function before birth) - acts as a shock absorber (protects foetus from physical injury)
71
explain the role of hormones in early pregnancy
- the developing embryo (blastocyst) secretes hCG from the chorionic villi - hCG maintains the corpus lute for the first 16 weeks - the corpus lute secrets progesterone - progesterone maintains the endometrium - the endometrium contributes to the structure of the placenta
72
explain the role of hormones in later pregnancy
- the placenta starts to secret both oestrogen and progesterone - the levels of both hormones will remain high in the blood plasma until the end of pregnancy
73
explain the role of hormones during birth
- just before birth oestrogen levels will increase while progesterone levels decrease - this results in the contraction of the uterus wall (myometrium layer) - oxytocin is no longer inhibited - oxytocin is secreted from the posterior pituitary gland and causes the myometrium to contract - a positive feedback mechanism is in place as contractions cause further oxytocin secretion - therefore, contractions become stronger and more frequent
74
explain the role of hormones during lactation
- as progesterone levels decrease, prolactin is no longer inhibited - prolactin is secreted from the anterior pituitary gland during and after birth - it stimulates the mammary glands to produce milk - milk is released when oxytocin causes the muscles around the milk ducts to contract

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