4.1 HUMAN REPRODUCTION Flashcards
(114 cards)
1
Q
label male systems
A
2
Q
label female systems
A
3
Q
scrotum
A
sacs of skin that accomodate the testes
4
Q
testes
A
2 male gametes, where the male gametes (spermatzoa) are made. also produce testosterone
5
Q
vas deferens
A
straight tube (40 cm long) carries sperm to the urethra, most sperm stored here
6
Q
epididymis
A
very long coiled tube (6m long) sperm mature here before entering the vas deferens
7
Q
seminal vesicle
A
secrete mucus and watery alkaline fluid containing nutrients (fructose)
8
Q
prostate gland
A
secretes mucus and an alkaline fluid into the ejaculatory duct. helps to neutralise the acidity of the vagina
9
Q
urethra
A
tube that carries urine from the bladder and semen out of the penis
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
11
Q
spermatogenesis
A
is the formations of spermatozoa in testes. takes place in seminferous tubules. the walls of the seminiferous tubules have germinal epithelial cells
12
Q
what do the walls of seminiferous tubules have
A
germinal epithelial cells
13
Q
ovaries
A
2 female gonads where the female gametes are made (ova)
secretes oestrogen and progesterone
14
Q
fallopian tubes
A
also called oviducts
tubes are about 12cm long carry the ova from the ovaries to the uterus
15
Q
uterus
A
where a foetus develops during pregnancy
has muscular walls which contract during labour
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
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
18
Q
vagina
A
a muscular tube containing elastic tissue, strectches during childbirth and sexual intercourse
19
Q
whats gametogenesis
A
formation of haploid (n) gametes
20
Q
stages of spermatogenesis
(5)
A
- germinal epithelial cells (2n) divide by mitosis to form spermatogonia cells (2n)
- spermatogonia grow and increase in size forming the primary spermatocytes (2n)
- these undergo the first meiotic division to form haploid secondary spermatocytes (n)
- undergo a second meiotic division to form spermatids (n)
- spermatids attach to sertoli cells and mature and differentiate into spermatozoa
21
Q
spermatogenesis
(simple forms)
A
spermatagonia
primary spermatocyte
secondary spermatocyte
spermatid
spermatozoa (sperm)
22
Q
sertoli cells
A
or nurse cells
secrete a fluid to nourish the spermatids and protect them from the males immmune system
23
Q
laydig cells
A
secreting testosterone
24
Q
three sections of a sperm cell
A
head
mid-piece
tail
25
head of sperm
acrosome: specialised lysosome containing hydrolytic enzymes (fertilisation)
nucleus: haploid (n) contains the paternal chromosomes
26
mid-piece
mitochondria: provide ATP for movement of the flagellum
centrioles: form the sperm flagellum, and involved in cell division of the embryo after fertilisation
27
tail
a single flagellum
made from microtubules
propels sperm forwards
28
oogenesis
formation of the secondary oocyte, takes place in the ovaries,
involves both mitosis and meiosis
29
when does oogenesis start
before the birth of a female
30
stages of oogenesis before puberty
**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
31
stages of oogenesis after puberty
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)
32
what's ovulation
release of the secondary oocyte from an ovary (day 14)
33
oogenesis simple form
germinal epithelial
oogonia
primary oocyte
secondary oocyte + first polar body
ovulation
fertilisation
ovum+ second polar body
ovum+ sperm
zygote
34
label graafian follicle
35
label primary oocyte
36
what happens after ovulation if fertilisation has occurred
the corpus luteum secretes hormones which aid embryo development and prevent further ovulation during the pregnancy
37
what needs to happen for sexual intercourse to take place
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
38
what causes the penis to become erect
after the arterioles dilate and the venules constrict the spongy tissue of the penis becomes engorged with blood causing it to become erect
39
what does the force of ejaculation do
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
40
what happens with semen after sexual intercourse
semen containing spermatazoa will be deposited at the top of the vagina
41
what happens to the sperm when its in the female reproductive tracts
undergo capacitation before they can fertilitse a secondary oocyte
42
what initiates capacitation
seminal fluid and secretions from the female reproductive tract
43
how long does capacitation take
7 hours
44
what is capacitation
the removal of cholesterol and glycoproteins from the cell membrane covering the acrosome in the sperm head
45
what does capacitation do
refers to the change that spermatazoa undergo in the female genital tract that allow them to fertilise a secondary oocyte
46
what does cholesterol increase
increases the permeability of the membrane in front of the acrosome
47
what is responsible for the production of male sex hormones
laydig cells
48
what does the acrosome reaction allow
the sperm to penetrate the egg
49
explain the acrosome reaction
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
what enzyme are released from the acrosome
protease enzyme
(hydrolase)
51
when does the cortical reaction happen
once the sperm has fertilised.
happens very quickly
52
explain first step of cortical reaction
(what is it triggered by?)
the membranes of the cortical granules fuse with the oocyte membrane. triggered by Ca+
53
explain implantation
-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
what happens after the membranes of cortical granules have fused with the oocyte membrane
(cortical reaction)
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
what does fertilisation result in
a diploid zygote, which undergoes continuous mitosis for 8-10 days. cell numbers increase exponentially during this stage e.g. cleavage
55
what is cleavage
repeated mitotic divisions without growth
56
what does cleavage form
produces a solid ball of cells
57
what do solid ball of cells form
a hollow ball at the centre (blastocyst)
58
what is a blastocyst
fluid-filled, hollow ball of cells
59
structure of the blastocyst
-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
what does the inner cell mass develop into
the embryo
61
what does trophoblast develop into
the placenta
62
what happens following implantation
2 membranes form. (chorion and amnion) these surround the foetus in a fluid-filled sac for protection.
63
what are the roles of the 2 membranes
protects from mechanical shock and maintains foetal temperature
64
what do chorion form
growths called chorionic villi that form the bases of the placenta
65
what do chorion do
secrete hCG which prevents the corpus luteum from breaking down
66
what do the villi gain
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
adpatations if chorionic villi
microvili
increase SA
68
importance of intervillous spaces
foetal and mothers blood DO NOT MIX
69
other name for intervillous space
lacuna
70
what does the umbilical cord develop from
the placenta
71
what does umbilical cords contain
blood vessels
72
role of the umbilical cord
blood of the foetus comes to the placenta through here
73
how does the blood come from the foetus
through 2 umbilical arteries
74
explain blood pathway mother and foetus
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
importance of counter-current flow
ensures the concentration gradient is maintained across the entire gas exchange surface. never reach equillibirum, exchange is more efficient
75
explain counter-current flow in blood flow
-maternal and foetul blood flows in opposite direction to each other
76
what does umbilical arteries carry
deoxygenated blood
low in nutrients
high in waste products
77
what does umbilical veins contain
oxygenated blood
high in nutrients
low in waste products
78
what are the adaptions for exchange
(blood mother and foetus)
-blood in uterine arteries at high pressure
-large capillary network in placenta
-chorionic villi highly folded
-blood flows into the lacuna very frequently
79
what are the 3 roles of the placenta
-as an endocrine organ
-exchange of gases and nutrients
-acts as a physical barrier
80
how is the placenta an endocrine organ
secretes hormones to support pregnancy
81
what hormones do the placenta secrete
HCG, oestrogen and progesterone
82
how is the placenta adapted to exchange gases and nutrients
distance between both circulations is small to allow effective exchange
83
how does the placenta act as a physical barrier
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
explain the immunological protection a placenta supplies
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
what are the limits to immunological protection of the placenta
-sometimes the foetus is rejected resulting in miscarriage
-sometimes Rhesus disease develops
-placenta doesn't always provide immunological protection to foetus
86
what are some examples of unwanted substances that can cross the placenta
some microbes (HIV)
some drugs (nicotine and heroin)
87
facts about menstrual cycle
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
4 hormones that control the menstrual cycle and where are they secreted from
-follicle stimulating hormone (FSH) and lutenising hormone (LH) secreted from anterior pituitary gland
-oestrogen and progesterone
(secreted from the ovaries)
89
4 phases of cycle
- follicular phase
- ovulation
- luteal
-menstruation
90
explain what happens in the follicular phase
-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
explain ovulation
-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
when does ovulation happen
midway through the cycle
(day 14)
93
explain the luteal phase
- 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
explain menstruation
-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
function of FSH
stimulates follicular growth in ovaries
-stimulates oestrogen secretion (from developing follicles)
96
function of LH
surge causes ovulation
results in the formation of the corpus luteum
97
function of oestrogen
thickens uterine lining (endometrium)
inhibits FSH and LH for most of the cycle (prevent follicles from developig)
stimulated FSH and LH release pre-ovulation
98
function of progesterone
thickens uterine lining (endometrium)
inhibits FSH and LH
99
when is pregnancy measured from
the first day of the last period until the birth of the baby
100
how long is pregnancy
37-42 weeks is normal
101
what is amniocentesis
a prenantal diagnostic test in which a small amount of amniotic fluid is removed to determine any genetic abnormality
102
function of amniotic fluid
-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
explain hormones in early pregnancy
-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
what does HCG do
(early pregnancy)
maintains the corpus luteum for first 16 weeks
105
what does the corpus luteum secretes
(early pregnancy)
secretes progesterone to maintain the endometrium
106
what does the endometrium contribute to
(early pregnancy)
contributes to the structure of the placenta
107
hormones in pregnancy after 16 weeks
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
effects of oestrogen in pregnancy
-inhibits FSH secretion (no more follicles develop)
-inhibits LH secretion (no more ovulation)
-stimulates the growth of the uterus (accomadates the growing foetus)
109
effects of progesterone in pregnancy
-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
explain hormones and birth
-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
explain lactation and hormones
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
hormones in spermatogenesis
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
