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A2 BIOLOGY > 4.1 HUMAN REPRODUCTION > Flashcards

4.1 HUMAN REPRODUCTION Flashcards

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1
Q

label male systems

A
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2
Q

label female systems

A
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3
Q

scrotum

A

sacs of skin that accomodate the testes

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4
Q

testes

A

2 male gametes, where the male gametes (spermatzoa) are made. also produce testosterone

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5
Q

vas deferens

A

straight tube (40 cm long) carries sperm to the urethra, most sperm stored here

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6
Q

epididymis

A

very long coiled tube (6m long) sperm mature here before entering the vas deferens

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7
Q

seminal vesicle

A

secrete mucus and watery alkaline fluid containing nutrients (fructose)

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8
Q

prostate gland

A

secretes mucus and an alkaline fluid into the ejaculatory duct. helps to neutralise the acidity of the vagina

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9
Q

urethra

A

tube that carries urine from the bladder and semen out of the penis

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10
Q

penis

A

contains erectile tissue, which fills blood causing the penis to become erect. inserted into the vagina during sexual intercourse before the ejaculation of semen

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11
Q

spermatogenesis

A

is the formations of spermatozoa in testes. rakes place in seminferous tubules. the walls pf the seminiferous tubules. the walls of the seminiferous tubules have germinal epithelial cells

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12
Q

what do the walls of seminiferous tubules have

A

germinal epithelial cells

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13
Q

ovaries

A

2 female gonads where the female gametes are made (ova)
secretes oestrogen and progesterone

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14
Q

fallopian tubes

A

also called oviducts
tubes are about 12cm long carry the ova from the ovaries to the uterus

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15
Q

uterus

A

where a foetus develops during pregnancy
has muscular walls which contract during labour

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16
Q

endometrium

A

the inner most layer of the uterus. the site of embryo implantation. contains blood vessels and glands. gets shed during menstruation

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17
Q

cervix

A

the narrow entrance to the uterus from the vagina. a ring of muscle which can open/close. often blocked by a plug of mucus

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18
Q

vagina

A

a muscular tube containing elastic tissue, strectches during childbirth and sexual intercourse

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19
Q

whats gametogenesis

A

formation of haploid (n) gametes

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20
Q

stages of spermatogenesis
(5)

A
  1. germinal epithelial cells (2n) divide by mitosis to form spermatogonia cells (2n)
  2. spermatogonia grow and increase in size forming the primary spermatocytes (2n)
  3. these undergo the first meiotic division to form haploid secondary spermatocytes (n)
  4. undergo a second meiotic division to form spermatids (n)
  5. spermatids attach to sertoli cells and mature and differentiate into spermatozoa
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21
Q

spermatogenesis
(simple forms)

A

spermatagonia
primary spermatocyte
secondary spermatocyte
spermatid
spermatozoa (sperm)

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22
Q

sertoli cells

A

or nurse cells
secrete a fluid to nourish the spermatids and protect them from the males immmune system

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23
Q

laydig cells

A

secreting testosterone

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24
Q

three sections of a sperm cell

A

head
mid-piece
tail

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25
Q

head of sperm

A

acrosome: specialised lysosome containing hydrolyte enzymes (fertilisation)
nucleus: haploid (n) contains the paternal chromosomes

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26
Q

mid-piece

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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27
Q

tail

A

a single flagellum
made from microtubules
propels sperm forwards

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28
Q

oogenesis

A

formation of the secondary oocyte, takes place in the ovaries,
involves both mitosis and meiosis

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29
Q

when does oogenesis start

A

before the birth of a female

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30
Q

stages of oogenesis before puberty

A
  1. during development of a foetus, germinal epithelium (2n) divide by mitosis to form oogonia (2n) and more germinal epithelial cells (2n)
  2. oogonia undergo mitosis many times and enlarge to form primary oocyte
  3. primary oocytes starts to undergo meiosis, remain prophase 1 throughout childhood
  4. germinal epithelial cells divide by mitosis to form follicle cells(2n)
  5. primary oocytes enclosed by a ball of follicle cells, forms the primary follicles
  6. females are born with millions of primary follicles in their ovaries
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31
Q

stages of oogenesis after puberty

A

1.hormones released cause the primary oocytes in primary follicles to undergo first meitoic division (every month)
2. a smaller cell called a polar body (N) is formed, secondary oocyte formed (n)
3. secondary oocyte is larger, contains most of the cytoplasm
4. polar body degenerates
5.secondary oocyte is enclosed in a secondary follicle (graafian follicle if it matures)
6. only one primary follicle starts to develop and mature into a Graafian follicle
7. secondary oocyte within the graafian follicle begins meiosis 11 but stops at metaphase 11 unless fertilisation has taken place
8. graafian follicle migrates to the surface of the ovary where it bursts, releasing secondary oocyte into a fallopian tube during ovulation
9. secondary oocyte (n) completes meiosis 11 once fertilisation has taken place
10. an ovum (n) is produced (already fertilised) a smaller polar body (which degenerates)

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32
Q

what’s ovulation

A

release of the secondary oocyte from an ovary (day 14)

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33
Q

oogenesis simple form

A

germinal epithelial
oogonia
primary oocyte
secondary oocyte + first polar body
ovulation
fertilisation
ovum+ second polar body
ovum+ sperm
zygote

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34
Q

label graafian follicle

A
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35
Q

label primary oocyte

A
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36
Q

what happens after ovulation if fertilisation has occurred

A

the corpus luteum secretes hormones which aid embryo hormone development prevent further ovulation during the pregnancy

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37
Q

what needs to happen for sexual intercourse to take place

A

the penis must become erect to be inserted to the vagina.
physical and psychological effects cause the arterioles that enter the penis to dilate and the venules to constrict

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38
Q

what causes the penis to become erect

A

after the arterioles dilate and the venules constrict the spongy tissue of the penis becomes engorged with blood causing it to become erect

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39
Q

what does the force of ejaculation do

A

propels sperm through the cervix into the uterus. the sperm swim through the uterus into the oviducts, only a small number of sperm reach the ovum in the fallopian tube

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40
Q

what happens with semen after sexual intercourse

A

semen containing spermatazoa will be deposited at the top of the vagina

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41
Q

what happens to the sperm when its in the female reproductive tracts

A

undergo capacitation before they can fertilitse a secondary oocyte

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42
Q

what initiates capacitation

A

seminal fluid and secretions from the female reproductive tract

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43
Q

how long does capacitation take

A

7 hours

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44
Q

what is capacitation

A

the removal of cholesterol and glycoproteins from the cell membrane covering the acrosome in the sperm head

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45
Q

what does capacitation do

A

refers to the change that spermatazoa undergo in the female genital tract that allow them to fertilise a secondary oocyte

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46
Q

what does cholesterol increase

A

increases the permeability of the membrane in front of the acrosome

47
Q

what is responsible for the production of male sex hormones

A

laydig cells

48
Q

what does the acrosome reaction allow

A

the sperm to penetrate the egg

49
Q

explain the acrosome reaction

A

when the sperm reaches the secondary oocyte the acrosome will rupture. protease enzyme are released from the acrosome that digest the zona pellucida. the sperm membrane and the oocyte membrane fuse. sperm head enters the secondary oocyte. meisosis 11 within the secondary oocyte will re-commence to form an ovum and a second polar body. the nucleus of the ovum will fuse with the nucleus of the sperm to form a zygotic nucleus

50
Q

what enzyme are released from the acrosome

A

protease enzyme
(hydrolase)

51
Q

when does the cortical reaction happen

A

once the sperm has fertilised.
happens very quickly

52
Q

explain first step of cortical reaction
(what is it triggered by?)

A

the membranes of the cortical granules fuse with the oocyte membrane. triggered by Ca+

53
Q

explain implantation

A

-the trophoblast divide to make a distinctive inner cell mass (embryoblast) on one side. this is occuring as the zygote travels down the fallopian tubes to the uterus
the blastocyst implants itself into the endometrium of the uterus after about 3 days

53
Q

what happens after the membranes of cortical granules have fused with the oocyte membrane
(cortical reaction)

A

secretes the contents causing the zona pellucida to harden and to change into a fertilisation membrane. fertilisation membrane is hard because which prevents further penetration from sperm

54
Q

what does fertilisation result in

A

a diploid zygote, which undergoes continuous mitosis for 8-10 days. cell numbers increase exponentially during this stage e.g. cleavage

55
Q

what is cleavage

A

repeated mitotic divisions without growth

56
Q

what does cleavage form

A

produces a solid ball of cells

57
Q

what do solid ball of cells form

A

a hollow ball at the centre (blastocyst)

58
Q

what is a blastocyst

A

fluid-filled, hollow ball of cells

59
Q

structure of the blastocyst

A

-outer covering of cells surrounding the blastocyst is called the trophoblast
-inner cell mass
-trophoblast forms villi, secretes enzymes that enable implantation
-trophoblast also secretes the hormone hCG which maintain the corpus luteum

60
Q

what does the inner cell mass develop into

A

the embryo

61
Q

what does trophoblast develop into

A

the placenta

62
Q

what happens following implantation

A

2 membranes form. (chorion and amnion) these surround the foetus in a fluid-filled sac for protection.

63
Q

what are the roles of the 2 membranes

A

protects from mechanical shock and maintains foetal temperature

64
Q

what do chorion form

A

growths called chorionic villi that form the bases of the placenta

65
Q

what do chorion do

A

secrete hCG which prevents the corpus luteum from breaking down

66
Q

what do the villi gain

A

capillaries which connect to the umbilical arteries and the umbilical veins. these vessels connect the embryo to the uterus wall via the umbilical cord

67
Q

adpatations if chorionic villi

A

microvili
increase SA

68
Q

importance of intervillous spaces

A

foetal and mothers blood DO NOT MIX

69
Q

other name for intervillous space

A

lacuna

70
Q

what does the umbilical cord develop from

A

the placenta

71
Q

what does umbilical cords contain

A

blood vessels

72
Q

role of the umbilical cord

A

blood of the foetus comes to the placenta through here

73
Q

how does the blood come from the foetus

A

through 2 umbilical arteries

74
Q

explain blood pathway mother and foetus

A

once exchange of material has taken place across the placenta with the maternal blood it is returned to the foetus via one umbilical vein

75
Q

importance of counter-current flow

A

ensures the concentration gradient is maintained across the entire gas exchange surface. never reach equillibirum, exchange is more efficient

75
Q

explain counter-current flow in blood flow

A

-maternal and foetul blood flows in opposite direction to each other

76
Q

what does umbilical arteries carry

A

deoxygenated blood
low in nutrients
high in waste products

77
Q

what does umbilical veins contain

A

oxygenated blood
high in nutrients
low in waste products

78
Q

what are the adaptions for exchange
(blood mother and foetus)

A

-blood in uterine arteries at high pressure
-large capillary network in placenta
-chorionic villi highly folded
-blood flows into the lacuna very frequently

79
Q

what are the 3 roles of the placenta

A

-as an endocrine organ
-exchange of gases and nutrients
-acts as a physical barrier

80
Q

how is the placenta an endocrine organ

A

secretes hormones to support pregnancy

81
Q

what hormones do the placenta secrete

A

HCG, oestrogen and progesterone

82
Q

how is the placenta adapted to exchange gases and nutrients

A

distance between both circulations is small to allow effective exchange

83
Q

how does the placenta act as a physical barrier

A

a physical barrier to protect the foetal cappillaries from damage by the mothers higher blood pressure. also protects from fluctuations of mothers b.p

84
Q

explain the immunological protection a placenta supplies

A

chorionic villi cells fuse together, so white blood cells from the maternal circulation cannot get into the foetal blood. antibodies from the maternal blood pass via the placenta to provide passive immunity

85
Q

what are the limits to immunological protection of the placenta

A

-sometimes the foetus is rejected resulting in miscarriage
-sometimes Rhesus disease develops
-placenta doesn’t always provide immunological protection to foetus

86
Q

what are some examples of unwanted substances that can cross the placenta

A

some microbes (HIV)
some drugs (nicotine and heroin)

87
Q

facts about menstrual cycle

A

happens if fertilisation doesn’t occur
usually 28 days
first day (0) when blood leaves the vagina due to the breakdown of the endometrium

88
Q

4 hormones that control the menstrual cycle and where are they secreted from

A

-follicle stimulating hormone (FSH) and lutenising hormone (LH) secreted from anterior pituitary gland
-oestrogen and progesterone
(secreted from the ovaries)

89
Q

4 phases of cycle

A
  • follicular phase
  • ovulation
  • luteal
    -menstruation
90
Q

explain what happens in the follicular phase

A

-FSH is secreted from the anterior pituitary gland
- this stimulates the Graafian follicle to produce oestrogen (thecal cells)
-oestrogen inhibits FSH secretion to prevent other follicles developing (negative feedback)
-oestrogen triggers the repair of the endometrium following menstruation (thickens)

91
Q

explain ovulation

A

-oestrogen stimulates the anterior pituitary to secrete LH
-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 oocuty (ovulation)
- the graafian follicle becomes the corpus luteum

92
Q

when does ovulation happen

A

midway through the cycle
(day 14)

93
Q

explain the luteal phase

A
  • the corpus luteum secretes high levels of progesterone as well as lower levels of oestrogen
    -oestrogen act on the uterus to thicken the endometrium lining
    -progesterone maintains the endometrium lining
    -oestrogen and progesterone also inhibit secretion of FSH and LH from the pituitary gland, preventing any follicles from developing (negative feedback)
94
Q

explain menstruation

A

-if implantation doesn’t pccur, falling FSH and LH levels cause the corpus luteum to degenerate
-progesterone levels fall, endometrium lining breaks down and is lost during menstruation
-oestrogen levels are also low so FSH secretion is no longer inhibited and another cycle initiated

95
Q

function of FSH

A

stimulates follicular growth in ovaries
-stimulates oestrogen secretion (from developing follicles)

96
Q

function of LH

A

surge causes ovulation
results in the formation of the corpus luteum

97
Q

function of oestrogen

A

thickens uterine lining (endometrium)
inhibits FSH and LH for most of the cycle
stimulated FSH and LH release pre-ovulation

98
Q

function of progesterone

A

thickens uterine lining (endometrium)
inhibits FSH and LH

99
Q

when is pregnancy measured from

A

the first day of the last period until the birth of the baby

100
Q

how long is pregnancy

A

37-42 weeks is normal

101
Q

what is amniocentesis

A

a prenantal diagnostic test in which a small amount of amniotic fluid is removed to determine any genetic abnormality

102
Q

function of amniotic fluid

A

-maintains foetal temperature
- provides lubrication
-contributes to lung fevelopment
-allows movement (bones and muscles can function before birth)
-acts as a shock absorber (protects foetus from physical injury)

103
Q

explain hormones in early pregnancy

A

-developing embryo secretes HCG (from chorionic villi)
which maintains the corpus luteum for first 16 weeks
the corpus luteum secretes progesterone to maintain the endometrium

104
Q

what does HCG do
(early pregnancy)

A

maintains the corpus luteum for first 16 weeks

105
Q

what does the corpus luteum secretes
(early pregnancy)

A

secretes progesterone to maintain the endometrium

106
Q

what does the endometrium contribute to
(early pregnancy)

A

contributes to the structure of the placenta

107
Q

hormones in pregnancy after 16 weeks

A

placenta will start to secrete both oestrogen and progesterone
levels of both hormones will remain high in the blood plasma until the end of pregnancy

108
Q

effects of oestrogen in pregnancy

A

-inhibits FSH secretion (no more follicles develop)
-inhibits LH secretion (no more ovulation)
-stimulates the growth of the uterus (accomadates the growing foetus)

109
Q

effects of progesterone in pregnancy

A

-inhibits FSH secretion (no more follicles develop)
-inhibits LH secretion (no more ovulation)
-inhibits oxytocin (prevents contraction of the smooth muscle within the myometrium of the uterus and the milk duct)

110
Q

explain hormones and birth

A

-just before birth, oestrogen levels increase, progesterone levels decrease.
-results in contraction of the uterus wall (myometrium layer)
-oxytocin no longer inhibited
-oxytocin is secretion from the prosterior pituitary gland, also causes the myometrium to contract
-a positive feedback mechanism is in place, contractions cause further oxytocin secretion
-contractions stronger, more frequent

111
Q

explain lactation and hormones

A

as progesterone levels decrease, prolactain is no longer inhibited
prolactin is secreted from the anterior pituitary gland during and after birth
stimulated mammary glands to produce milk
milk is released when oxytocin causes the muscles around the milk ducts to contract

112
Q

hormones in spermatogenesis

A

LH stimulates the cells of laydig/interstitial cells to secrete testosterone
FSH and testosterone cause the sertoli cells to initiate meiosis of the primary spermatocytes and differentiate to make spermatazoa
however the inhibitor effects of testosterone on the pituitary gland. similar to the effect of oestrogen on FSH secretion in females

A2 BIOLOGY (4 decks)

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