Reproductive System Flashcards
(444 cards)
1
Q
in humans what is sex determined by?
A
X and Y chromosomes
2
Q
how many chromosomes are in diploid cells?
A
46 or 23 pairs
3
Q
how many chromosomes are found in haploid gametes?
A
23 chromosomes including one of either X or Y
4
Q
what is the role of the Y chromosome in sex determination?
A
determines sex
5
Q
how are haploid gametes created?
A
meiosis
6
Q
how does meiosis differ between spermatocyte and oocyte?
A
cell division in oocyte is uneven and produces one egg cell and the polar bodies to ensure egg receives all essential materials
7
Q
what are 2 abnormalities of sex chromosomes?
A
Turners Syndrome
Klinefelter’s Syndrome
8
Q
what is the genotype of someone with Turners Syndrome?
A
X0 - one X, no Y
9
Q
what is the genotype of someone with Klinefelter’s Syndrome?
A
XXY - two X and one Y
10
Q
what is the phenotype of someone with Turner’s syndrome?
A
female
11
Q
what is the phenotype of someone with Klinefelter’s Syndrome?
A
male (male genitalia, may have feminine characteristics)
12
Q
what does the Y chromosome determine?
A
maleness - presence of testis
13
Q
what gene on the Y chromosome determines presence of testis?
A
SRY gene
14
Q
what is the role of the SRY gene?
A
determines production of TDF
15
Q
what is TDF?
A
testis determining factor
16
Q
what is the role of TDF?
A
causes undifferentiated gonad to become testis
17
Q
what is androgen insensitivity syndrome?
A
partial or complete inability to respond to androgens - genetic makeup is male but due to AIS there is female phenotype
18
Q
what are sex hormones responsible for in development?
A
sex determination
19
Q
what hormone is from the family prostagens?
A
progesterone
20
Q
what hormone is from the family androgens?
A
testosterone
21
Q
what hormone is from the family oestrogens?
A
oestrogen (oestrodiol 17beta)
22
Q
what is the precursor to the sex hormones?
A
cholesterol
23
Q
what type of hormones are sex hormones?
A
steroid
24
Q
what are the main female sex hormones?
A
oestrogen (oestrodiol 17beta)
progesterone
25
what is the main male sex hormone?
testosterone
26
how are oestrogens produced?
cholesterol is converted to progesterone through enzyme action. Progesterone is converted to testosterone and then testosterone to oestrogens via enzyme action for both stages.
27
what occurs in the ampulla of the uterine tube?
fertilisation of the egg
28
what is the role of the fimbria?
uptake of the ovulated ovum from the ovary
29
what are the 2 main functions of the ovary?
gametogenic and endocrine
30
what is gametogenic function?
production of gametes
31
what is the purpose of the endocrine function of the ovaries?
ensures right environment for development of gametes
32
what is the oestrous cycle named after?
oestrus
33
what is oestrus?
behavioral changes associated with sexual receptivity (heat)
34
what is the oestrous cycle formed of?
physiological changes that occur between one oestrus and the next
35
what is the oestrous cycle known as in humans?
menstrual cycle
36
what is the importance of oestrus?
occurs just before ovulation and optimises the chance of successful fertilization
37
what occurs in the follicular phase of the oestrous cycle in the ovary?
primordial follicles grow and develop with the oocyte within them
38
what happens during pro-oestrus?
follicles develop
39
what happens during oestrus?
behavioral changes
40
what happens at ovulation?
oocyte is released from the follicle
41
when does metoestrus occur?
between ovulation and formation of the corpus luteum
42
what occurs during the luteal phase of the oestrous cycle?
corpus luteum is formed from the degraded follicle and then breaks down
43
what is the dominant hormone during the follicular phase of the oestrous cycle?
oestrogen
44
what is the dominant hormone during the luteal phase of the oestrous cycle?
progesterone
45
what oocytes are female mammals born with?
finite number of primary oocytes
46
what stage of development do primary oocytes remain in until ovulation?
arrested state of development in prophase of first meiotic division
47
when does the menopause occur?
when no oocytes remain in the ovary
48
what is the name of the fist oocyte found pre-birth?
oogonium
49
how is the primary oocyte created pre-birth?
growth of the oocyte from oogonium
50
when does the first meiotic division of oocyte occur?
ovulation
51
what does the first meiotic division of oocyte at ovulation produce?
secondary oocyte and a first polar body
52
when does second meiotic division of the oocyte take place?
fertilisation
53
what does the second meiotic division of oocyte at fertilisation produce?
ootid (ovum) and second polar body
54
what cells is the primordial follicle surrounded by?
flat cells
55
what happens during stage 1 of follicular development?
oocyte increases in size
| granulosa cells switch from flat to cuboidal
56
what is formed in stage 2 of follicular development?
zona pellucida
57
what is the zona pellucida?
acellular glycoprotein layer around the oocyte
58
what happens to granulosa cells during stages 3-5 of follicular development?
mitosis to produce 4 layers around the zona pellucida
59
what happens to the cells around the follicles during stages 3-5?
blood capillaries invade cells surrounding follicles (theca interna)
60
what is the theca interna?
connective tissue layer surrounding the granulosa cells
61
what happens during stage 6 of follicular development?
fluid forms in between granulosa cells
62
what is the name for the fluid filled spaces created during stage 6 of follicular development?
antrum
63
what is the name of the follicle at stage 7?
Graafian follicle
64
what happens at stage 7 of follicular development?
liquor folliculi builds up to from antrum
| oocyte is pushed to one side and is surrounded by cumulus oophorus
65
what is the name of the fluid that creates the antrum in follicular development?
liquor folliculi
66
what is the cumulus oophorus?
1-2 layers of granulosa cells which surround the oocyte after the formation of the antrum
67
what happens during stage 8 of follicular development?
innermost layer of cumulus oophorus becomes columnar and forms corona radiata
68
what happens during stage 9 of follicular development?
ovulation has occurred, corpus oophorus remains in place around oocyte. The follicle becomes corpus luteum
69
what is the corpus luteum formed from?
follicle that remains after ovulation
70
what stages of follicular development are hormone independent?
stage 1-5
71
what stages of follicular development are hormone dependent?
stage 6-9
72
what are cyclical events in the ovary coordinated by?
the hypothalamus and hormones from the pituitary gland
73
where do the coordinating hormones of the cyclical events in the ovary come from?
the pituitary gland
74
what part of the pituitary do coordinating hormones of the cyclical events in the ovary come from?
anterior pituitary
75
what hormones are released from the anterior pituitary which control cyclical events in the ovary?
follicle stimulating hormone (FSH)
luteinising hormone (LH)
prolactin (PL)
76
what are FSH and LH formed from?
glycoproteins
77
what cell are FSH and LH secreted from?
gonadotrophs in the anterior pituitary
78
what are FSH and LH known as collectively?
gonadatrophic hormones
79
what type of hormone is prolactin?
peptide
80
what cells is prolactin secreted by?
lactotrophs
81
what factor from the hypothalamus causes release of LH and FSH?
gonadotropin releasing factor (GnRH)
82
what is the effect of GnRH?
tonic or surge release of FSH or LH from the anterior pituitary
83
what is prolactin release controlled by?
prolactin inhibitory factor (PIF) from hypothalamus
84
what is prolactin inhibitory factor (PIF) made from?
dopamine
85
what does an increase in PIF lead to?
decrease of prolactin (PF)
86
how would the tonic release of GnRH be described?
pulsatile
87
in the follicular phase what does increase in frequency of GnRH pulses lead to?
increase of FSH and LH release
88
what does FSH promote?
development and differentiation of follicle
89
what does development and differentiation of follicle lead to the synthesis of?
increased amounts of oestrogen
90
how do the frequency of GnRH pulses differ in the luteal phase?
reduced frequency of GnRH pulses
91
what does a reduced frequency of GnRH pulses during the luteal phase lead to?
fall in FSH and LH secretion
| increase in progesterone synthesis from corpus luteum
92
what hormone is synthesised by the corpus luteum?
progesterone
93
what effect does GnRH have on its own release?
negative feedback
94
what effect does LH and FSH have on GnRH release?
negative feedback
95
what effect does progesterone have on GnRH release?
negative feedback
96
what is the effect of inhibin on LH/FSH?
inhibition of LH/FSH
| particularly FSH to allow LH surge for ovulation
97
what effect does progesterone have on GnRH?
negative feedback
98
what effect does oestrogen have on LH/FSH and GnRH?
negative feedback until just before ovulation where it switches to positive feedback in order to initiate surge release of LH
99
what is the effect of prolactin on PIF?
positive feedback - increased prolactin increases PIF production in order to reduce PIF levels
100
what external factors can influence GnRH production and so production of sex hormones?
```
olfactory
visual
auditory
temperature
stress
```
101
is initial follicle development at all related to hormones?
no - there is continuous follicle growth in early stages irrespective of hormones
102
what leads a follicle to become dominant and lead to ovulation?
slightly increased FSH binding
103
what does increased FSH binding to a developing follicle lead to the secretion of?
increased IGF secretion from follicle which in turn increases FSH binding
104
what type of feedback is there on FSH binding and IGF production in the developing follicle?
positive
105
what hormone is synthesised due to increased FSH binding to a developing follicle?
oestrogen
106
what cells of the follicle secrete oestrogen?
granulosa
107
what type of feedback effect is seen in granulosa cells producing oestrogen in the developing follicle?
positive
108
what is ovulation induced by?
LH surge
109
what is ovulation induced by in spontaneous ovulators?
switch from negative to positive feedback of oestrogen on GnRH leading to surge of LH
110
what is ovulation induced by in induced ovulators?
surge of LH triggered by mating
111
what is positive feedback of oestrogen on GnRH induced by?
prolonged high levels of oestrogen leading to increase in GnRH pulses
112
what receptors does oestrogen act via?
alpha and beta
113
what oestrogen receptors are found in GnRH neurones within the hypothalamus?
beta
114
what is the role of beta oestrogen receptors on GnRH neurones?
mediate negative feedback of oestrogen on tonic GnRH release
115
what receptors does positive feedback of oestrogen on GnRH occur via?
alpha
116
are there alpha oestrogen receptors on GnRH neurones?
no - work through intermediate neurones
117
what neurones may be involved in inducing LH surge due alpha oestrogen receptors?
Kisspeptin - synapse onto GnRH neurones in hypothalamus
118
what does increased frequency of GnRH pulses lead to?
surge release of LH
119
what is the role of PGF 2a?
causes degeneration of the corpus luteum at the end of the luteal phase
120
what does polyoestrus mean?
continually cycles until pregnancy
121
what does seasonally monooestrus mean?
one cycle per season
122
what doe seasonally polyoestrus mean?
series of cycles in a certain season
123
what type of cycle do humans have?
polyoestrus
124
what causes menses?
support for endometrial lining is lost as progesterone level reduces so it is shed
125
what happens during the follicular phase?
endometrium lining grows and develops
| follicle develops
126
what happens during the luteal phase?
endometrium lining grows and develops and is maintained by progesterone
corpus luteum releases progesterone
127
what changes during the oestrus cycle?
biosynthetic activities of follicles and corpus luteum
128
what is the hypothesis for the mechanism for switch from oestrogen to progesterone synthesis?
two cell hypothesis
129
what are theca cells?
those which surround the follicle
130
what are granulosa cells?
those which surround oocyte
131
in what 3 ways do theca and granulosa cells differ?
hormone receptors
steroidogenic (those which are involved in producing hormones) enzyme activity
micro-environment (e.g. blood supply)
132
what does prolactin influence?
switch of follicle to corpus luteum and so production of progesterone
133
how does the micro-environment of granulosa cells influence the hormones they can produce?
no blood supply so cholesterol is reduced - difficult to synthesise any hormones
134
what happens during ovulation?
oocyte is shed from primary follicle and meiosis is resumed
135
what is ovulation triggered by?
LH surge
136
what are the 2 types of ovulation?
spontaneous and induced
137
what does the primary oocyte become after ovulation?
secondary oocyte
138
what happens to the secondary oocyte after ovulation?
enters oviduct
139
what surrounds the secondary oocyte as it enters the oviduct?
corona radiata and cumulus oophorus
140
what is the movement of the secondary oocyte into the oviduct aided by?
the cilia on fimbria
141
what effects does LH have that lead to ovulation?
induces protease and collagenase activity in the follicle
142
what does increased protease and collagenase activity in the follicle lead to?
increase in follicular fluid and so thinning of granulosa cell layer
143
what is the role of the Stigma in ovulation?
blister which bursts and releases oocyte
144
what is the corona radiata formed from?
innermost granulosa cells
145
what makes up the cumulus oophorus?
all granulosa cells
146
where does the first polar body come from?
1st meiotic division of oocyte
147
what is the infundibulum?
open end of oviduct
148
what is the oviduct lined with?
cilliated and secretory epithelium
149
what is the movement of oocyte in the oviduct due to?
action of cilia within the ampulla and muscular contractions in the isthmus
150
what is the ampulla?
first section of the oviduct after the infundibulum
151
where is the oocyte held within the oviduct until fertilization?
ampulla/isthmus junction
152
what is found at the ampulla/isthmus junction which holds the oocyte until fertilisation?
physiological sphincter (no physical presence)
153
when is the ampulla/isthmus junction physiological sphincter closed?
when oestrogen is high
154
when is the ampulla/isthmus junction physiological sphincter open?
when progesterone is high
155
how long does the early embryo take to reach the uterus after fertilisation?
2-3 days
156
why is there a delay of 2-3 days between fertilization and implantation into the uterus?
to ensure that the hormone environment is correct before the embryo arrives and implants
157
what happens to the follicle once the oocyte has been released?
collapses and forms corpus luteum
158
what cells make up the corpus luteum?
granulosa cells and cells of theca interna
159
where do blood vessels invading the corpus luteum originate from?
theca interna
160
what hormone does the corpus luteum begin to synthesise?
progesterone
161
what happens during lutinization?
cells cease dividing and are transformed into lutein cells
162
what do lutein cells contain?
yellow pigment
163
what hormones do thecal cells produce in the corpus luteum?
progesterone and androgens
164
what are thecal cells?
smaller lutein cells
165
what is the role of progesterone released by the corpus luteum?
many roles including decrease in GnRH leading to no LH surges so no more ovulation
166
what do large lutein cells produce?
progesterone
167
in humans what else is produced by the corpus luteum?
oestrogens (particularly oestradiol 17beta)
inhibin
oxytocin
168
what is the role of inhibin released from the corpus luteum?
promotes progesterone synthesis and inhibits FSH/LH
169
what is the role of oxytocin produced by the corpus luteum?
has a role in luteolysis
170
what happens to teh corpus luteum if a pregnancy does not occur?
undergoes luteolysis
171
what does luteolysis enable?
another follicular phase to start
172
what is involved in luteolysis?
ischaemia, leading to progressive cell death. This leads to a fall in progesterone output
173
what is left of the corpus luteum after luteolysis?
whitish scar tissue remains
174
what is the name of the whitish scar tissue that remains after luteolysis?
corpus albicans
175
in non primate species what effect does hysterectomy have on the corpus luteum?
prolongs lifespan
176
in non primate species what effect does injection of homogenised endometrium have on the corpus luteum?
causes luteolysis
177
in sheep what is the effect on the corpus luteum of ligating blood vessels between the uterus and ovary?
prolongs lifespan
178
what factor is thought to trigger luteolysis in non-primates?
prostaglandin F2alpha
179
how is luteolysis thought to occur in non-primates?
prostaglandin (PGF) is synthesised by the uterus and released into uterine veins. Due to the close proximity of the uterine artery to the uterine pedicle, PGF is picked up by the ovarian artery and delivered back to the ovary where it causes luteolysis
180
where is prostaglandin F2alpha synthesised?
endometrium
181
what is prostaglandin F2alpha production stimulated by?
oxytocin from corpus luteum
182
is luteolysis in primates related to prostaglandin?
no
183
what is the possible cause of luteolysis in primates?
low levels of LH in luteal phase are insufficient to maintain corpus luteum which slowly regresses
184
what is the influence of oestrogens on the oviduct?
movement of oocyte:
increased secretions
increased cilia and increased activity
increased muscle activity
185
what is the influence of progestagens (progesterone) on the oviduct?
no oocyte movement:
reduced secretions
cilia number and activity decline
reduced muscle activity
186
what is the influence of oestrogens on the cervix?
allow passage of sperm:
relaxation of cervical muscle
thinner alkaline secretions - allow the penetration of sperm
187
what is the influence of progestagens (progesterone) on the cervix?
stop passage of sperm:
cervix is 'firmer'
thick acidic secretions - prevent secretion of sperm
188
what is the influence of oestrogens on the mammary gland?
primes glandular tissue
189
what is the influence of progestagens (progesterone) on the mammary gland?
stimulates growth of glandular tissue
190
what is the influence of oestrogens on the uterus?
increased myometrium activity
increased number and size of endometrial glands
increased watery secretions
increases synthesis of progesterone receptors in endometrium
191
what is the influence of progestagens (progesterone) on the uterus?
reduced myometrium activity
further glandular growth
increased thick glycoprotein/sugar/amino acid rich secretions
development of spiral arteries in stroma
192
what is the purpose of increased thick glycoprotein/sugar/amino acid rich secretions from the uterus?
provides nutrition for the early embryo
193
what are the 2 functions of the testis?
gametogenic
| endocrine
194
where are the 2 functions of the testis carried out?
seminiferous tubule
| endocrine cells within connective tissue
195
where does spermatogenesis occur?
seminiferous tubules
196
what cells of the seminiferous tubules provide nourishment, control and coordination of spermatogenesis?
sertoli cells
197
what are developing sperm engulfed by that is part of sertoli cells?
adluminal compartments
198
where do developing sperm move from?
basal compartment
199
where are developing sperm shed?
into the lumen of the tubule once they are fully differentiated
200
what forms the blood testis barrier?
junctional complexes between Sertoli cells
201
where does mitosis occur during spermatogenesis?
in basal compartment near basal lamina
202
where does meiosis occur during spermatogenesis?
in the adluminal compartment, on the other side of tight junctions
203
what are developing sperm protected from in the adluminal compartment?
immune system
204
what does the adluminal compartment allow?
a different seminiferous tubular fluid micro-environment for the late stages of spermatogenesis
205
is sperm production temperature sensitive?
yes
206
how is the scrotal temperature maintained several degrees below core temperature?
testis is removed from body core in the scrotum
| heat exchanger in blood supply before it enters the testis
207
what function of the testicular artery makes it an efficient heat exchanger?
is superficial for a long distance
208
what is the name of the muscle which raises and lowers the testicles in response to temperature changes?
cremasteric muscle
209
what is the name of the products of meiosis 2 found in the adluminal compartments?
spermatid
210
do spermatid look like sperm?
no
211
what happens during spermiogenesis?
head, midpiece and tail of sperm are formed
212
what is formed by spermiogenesis?
spermatozoa
213
what happens to spermatozoa?
shed into the lumen of the tubule
214
what are the 3 processed of spermiogenesis?
condensation of nucleus
acrosome formation
flagellogenesis
215
what is the process of condensation of nucleus essential for?
transfer of genetic material
216
what is the process of acrosome formation essential for?
enabling fertilisation
217
what is flagellogenesis?
development of flagellum
218
what is the flagellum of sperm essential for?
independent and rapid movement
219
what are the 4 phases of spermiogenesis?
golgi phase
cap phase
acrosomal phase
maturation phase
220
what happens during the golgi phase of spermiogenesis?
alignment of centrioles and golgi apparatus at either end of the nucleus.
Increase in activity within the cell
DNA becomes condensed
221
what happens during the cap phase of spermiogenesis?
golgi apparatus expands to form a cap over nucleus
| centriole elongates to form flagellum
222
what happens during the acrosomal phase of spermiogenesis?
cap expands to form acrosome
mitochondria migrate to midpiece
residual cytoplasm is removed
223
what is the acrosome?
enzyme filled sac
224
what happens during the maturation phase of spermiogenesis?
last of unnecessary cytoplasm removed in residual bodies
tail begins to elongate
mitochondria wrap around proximal region of tail in midpiece
225
what does the head of the spermatozoa contain?
nucleus with highly condensed chromatin covered by acrosomal cap
226
what does the midpiece of the spermatozoa contain?
packed spiral of mitochondria
227
what is the role of mitochondria in the midpiece of the spermatozoa?
provides ATP for movement of flagellum
228
what is found in the tail of the spermatozoa?
9+2 microtubule arrangement for motility
229
what is the 9+2 tubule arrangement in the spermatozoa tail for?
motility
230
what is the key element that provides motility to spermatozoa?
dynein arms attaching to adjacent microtubules
231
what is the activity of dynein arms in spermatozoa flagellum provided by?
Ca2+ dependent ATPase activity
232
what does hydrolysis of ATP in the flagellum of spermatozoa cause?
microtubules sliding past each other due to a conformational change in dynein
233
how does dynein cause flagella bending?
axoneme is fixed to the sperm head the microtubules sliding past each other due to a conformational change in dynein results in flagellar bending
234
what generates the wave of bending in the spermatozoa flagellum?
sequential activation of dynein arms
235
how long is the spermatogenic cycle in a man?
64 days
236
when do stem cells start to divide in spermatogenesis?
every 16 days
237
when does the cycle of spermatogenesis start in the seminiferous tubule?
at different times along the length of the seminiferous tubule
238
what ensures sperm are produced constantly not periodically?
spermatogenic waves starting at different times along the length of the seminiferous tubule
239
what is testosterone responsible for?
male characteristics
240
what is testosterone secreted by?
Leydig cells
241
where are Leydig cells located in the testis?
interstitial tissue between seminiferous tubules
242
what is most testosterone converted to in tissues?
dihydrotestosterone
243
what is 98% of blood testosterone bound to?
albumin or sex hormone binding protein (SHBP)
244
what anterior pituitary hormone is testosterone release stimulated by?
LH
245
what enhances testosterone?
prolactin
246
where is prolactin released from?
anterior pituitary
247
what does episodic release of LH peak lead to in the male?
release of testosterone 45 minutes later
248
what hormone from the hypothalamus causes release of LH and FSH?
pulses of GnRH
249
what effect does testosterone have on GnRH and LH release?
negative feedback
250
what is the role of prolactin in the male?
enhances binding of LH to Leydig cells
251
what are the 3 effects of testosterone on the foetus?
development of testis
development of genital tract
testicular descent
252
what are the 3 effects of testosterone during puberty?
```
increase in testosterone levels
enlargement of genital tract
anabolic effects
masculine behaviour including libido
secondary sexual characteristics (beard growth etc)
```
253
what are the 3 effects of testosterone in adulthood?
maintenance of sexual activity
maintenance of genital tract
spermatogenesis
254
what happens to testosterone in the seminiferous tubule?
converted to DHT
255
where is there androgen receptors within the seminiferous tubule?
adluminal space where sperm are developing
256
what else is located in the adluminal space?
androgen binding protein
257
what is the role of androgen binding protein?
keeps more testosterone in the space where it is required
258
what is the role of FSH in spermatogenesis?
increased levels of androgen binding protein in adluminal spaces which further focuses testosterone binding
259
what is the role of inhibin?
negative feedback on FSH release
260
what is inhibin produced by in the male?
sertoli cells in response to FSH
261
what vitamin is an essential component of spermatogenesis?
vitamin A
262
what state are sperm in when they are released from seminiferous tubules into the lumen?
immature and immobile
263
what 2 mechanisms carry sperm in fluid to epididymis?
hydrostatic pressure in tubule from fluid produced by Sertoli cells
feeble peristalsis of seminiferous tubule
264
where do sperm enter the epididymis from the seminiferous tubule?
head
265
what is the role of the tail of the epididymis?
sperm storage and exit to ductus defrens
266
what is the movement of sperm through the epididymis due to?
cilia and contractions of smooth muscle due to oxcytocin
267
what are the 4 functions of the epididymis?
storage of spermatozoa until release
sperm concentration (removal of fluid)
maturation
phagocytosis of sperm in times of sexual abstinence or after vasectomy
268
in what condition are sperm when they leave the epididymis?
motile and fertile
269
what are the 3 E's of transport of sperm through the male reproductive tract into the female reproductive tract?
erection
emission
ejaculation
270
what is spermatozoa transported through after leaving the epididymis?
ductus (vans) defrens
271
what transports spermatozoa along the ductus (vans) defrens?
smooth muscle contractions
272
what is added to spermatozoa to make semen?
fluids from accessory glands
273
what are the accessory sex glands?
prostate
seminal vesicles
bulbo-urethral
274
what are the 7 constituents of seminal fluid?
```
high concentration of fructose/sorbitol
buffer
glycoproteins
constituents to stimulate female reproductive tract
coagulants
leukocytes
infective agents (HIV/hepatitis)
```
275
what is the role of fructose/sorbitol in seminal fluid?
energy source
276
what is the role of glycoproteins in seminal fluid?
to coat sperm head
277
what is the role of coagulants in seminal fluid?
after deposition semen may act like slow release gel or form a plug to prevent further penetration of sperm
278
what does the penis provide the means for?
deposition of sperm into the female reproductive tract
279
what type of response is erection?
reflex
280
what makes up the erectile tissue?
2 corpus cavernosa and 1 corpus spongiosum
281
what are the venous sinuses of the penis bound by?
fibroelastic tissue
282
how does erection occur?
vasodilation of arteries lead to increased blood flow
| veins become compressed causing sinuses to fill with blood and penis becomes turgid
283
what type of nervous stimulation causes erection?
parasympathetic stimulation
284
what are helicine arteries?
branches of main artery surrounded by smooth muscle
285
what is vasodilation of helicine arteries in the penis due to?
stimulation by acetylcholine
vasoactive peptide
nitrous oxide
286
what does nitrous oxide cause?
relaxation of the smooth muscle by increasing presence of cyclic GMP
287
how does viagra have its effect?
inhibits phosphodiesterase type 5 (PDE5) enzyme and so prevents breakdown of cGMP so encouraging vasodilation to continue for longer
288
what is the role of cGMP?
relaxation of smooth muscle - vasodilation
289
what is the role of phosphodiesterase type 5 (PDE5)?
breakdown of cGMP leading to contraction of smooth muscle in arteries
290
what is intromission?
thrusting behaviour that resembles a reflex - follows insertion of penis into the vagina
291
what is seminal emission caused by?
increase in sympathetic outflow to:
tail of epididymis
vans defrens
accessory glands
292
what happens during seminal emission?
contents of vans defrens are expelled into the pelvic urethra and provide stimulus for ejaculation
293
what does sympathetic innervation of the neck of the bladder during seminal emission cause?
contraction and prevents urine mixing with semen
294
what causes ejaculation?
further rhythmic contractions of the urethra under somatic control
295
why is semen not mixed evenly?
overlap between emission and ejaculation
296
what are the 3 different fractions of ejaculate?
pre-sperm
sperm
post-sperm
297
where is the ovum held in the oviduct until fertilisation?
ampulla/isthmus junction
298
what effect does age of the gamete have on the stability of the zygote?
older gamete makes zygote more unreliable
299
where is the usual site of deposition of sperm?
vagina
300
what is the pH of the vagina?
low/acidic
301
what may happen to the ejaculate to protect it from acidic conditions within the vagina?
may be coagulated
302
what may the ejaculate form to prevent backflow of sperm?
plug (rats/mice)
303
what are the 2 speeds of sperm transport?
rapid (sperm may be seen in ampulla 5 mins after deposition)
| sustained (sperm may be held up at different points)
304
what is the cervix made of?
connective tissue and muscle
305
what may happen to sperm in the crypts of the cervix?
may become held in crypts
306
what are micelles in the cervix?
strands of mucus
307
what is the role of micelles in the cervix?
help guide sperm through the cervix
308
what does the fluid secreted by the cervix prevent?
infection
309
what is fluid in the cervix like under the influence of oestrogen?
watery, alkaline, hospitable, formation of micelles
310
what is fluid in the cervix like under the influence of progesterone?
thick, acidic, inhospitable
311
what is transport of sperm through cervix aided by?
uterine muscular contractions creating negative pressure
312
what is passage of sperm through the uterus achieved by?
own propulsion aided by currents of fluid set up by action of uterine cilia
313
what is passage of sperm through the uterotubule junction regulated by?
intermittent sphincter
314
what happens to sperm once in the isthmus of oviduct?
become immobile
315
how are sperm attracted to isthmus/ampullary junction?
by chemo attractant from oocyte-cumulous oophorous mass
316
what essential process must happen to sperm for fertilisation to occur?
capacitation
317
what is capacitation due to?
exposure of sperm to environment of female reproductive tract
318
what happens during capacitation?
changes in macromolecular structure of sperm membrane - enabling acrosome reaction
activation
319
what is involved in activation of sperm?
changes in beating pattern of flagellum from wavelike to whiplash
320
what are the 4 stages of fertilization?
get sperm to oocyte
sperm nucleus enters oocyte
activation of oocyte
fusion of pro-nuclei
321
what happens during fertilization?
penetration of cumulus/zona pellucida by swimming action of sperm and acrosome reaction
322
what is the corona radiata designed to do?
guide sperm to zona pellucida
323
what do sperm release to aid attachment to zona pellucida?
hyaluronidase on sperm membrane
324
what do ZP3 receptors do?
bind to proteins on sperm head leading to acrosome reaction
325
where are ZP3 receptors located?
zona pellucida
326
what does binding of sperm to ZP3 receptors cause?
acrosomal membrane and plasma membrane to fuse releasing acrosomal enzymes
327
what does release of acrosomal enzymes cause?
digestion of zona pellucida to allow sperm to reach plasmalemma and attach
328
what is the plasmalemma?
membrane surrounding oocyte
329
what happens once the sperm reach the plasmalemma?
fusion of oocyte and acrosomal membrane so nucleus enters oocyte
330
what process resumes when sperm penetrates zona pellucida with aid of acrosomal enzymes?
meiosis resumes
331
what is the role of cortical granules in the cytoplasm of oocyte?
fuse with plasma membrane and enzymes cause changes in zona pellucida
332
how is polyspermy prevented?
fusion of cortical granules with plasma membrane and action of enzymes
333
what triggers second meiotic division?
fertilization
334
what is sygamy?
formation of diploid nucleus by fusion of sperm and oocyte nuclei
335
what is the role of the zona pellucida once the oocyte is fertilised?
prevents 2 embryos from sticking together
336
what happens during compaction of the embryo?
cells flatten against each other within zona pellucida
337
where in the fallopian tube does fertilization take place?
ampulla
338
why is there a need for time delay between fertilization and arrival/implantation of embryo to endometrium?
need to ensure hospitable environment for embryo so progesterone levels need to rise due to corpus luteum
339
what stage is the embryo at when it reaches uterus?
morula or blastocyst stage
340
what does the time to implantation usually exceed?
life of corpus luteum
341
how does the decline of corpus luteum affect the embryo?
leads to fall in progesterone levels so myometrium contractions increase which can lead to loss of the foetus
342
what prevents luteolysis until the placenta is established?
factors produced by the early embryo
343
what factor is produced by the embryo in humans which prevents luteolysis until the placenta has developed?
human chorionic gonadotrophin (HCG)
344
what must happen to endometrium to allow implantation?
must be oestrogen primed
345
what levels of hormone must be adequate at the time of implantation?
progesterone
346
what is the role of progesterone in aiding implantation?
decreases myometrial activity, increases glandular secretions (proteins, carbohydrates, lipids, steroids and ions)
347
what are the glandular secretions of the uterus essential for in early pregnancy?
early nutrition and implantation
348
what happens to the trophoblast during implantation?
comes into contact with the endometrium
349
what happens to the blastocyst in implantation in humans?
blastocyst penetrates epithelium of endometrium
350
what is the name for the type of implantation which occurs in humans?
interstitial implantation
351
what allows invasion of epithelium by embryo?
proteolytic enzymes from trophoblast and maternal epithelium
352
what does implantation of the embryo lead to the formation of?
the placenta
353
what happens during the adhesion phase of interstitial implantation of the placenta?
microvilli on embryo and epithelium interlock
proteases from endometrium and trophoblast are secreted and lead to the embryo invading through endometrium
increased permeability of blood vessels and oedema around blastocyst
354
what is the decidual cell reaction?
membranes between the cells break down
355
where on the embryo does the decidual cell reaction take place?
syncitiotrophoblast
356
what cells come into direct contact with maternal blood?
trophoblast cells
357
what is exchanged by the placenta?
nutrients, gases and foetal waste
358
what is the role of the placenta as well as nutrient exchange?
immunological barrier to prevent rejection of foetus
359
what 4 hormones are produced by the placenta?
human chorionic gonadotrophin
oestrogen
progesterone
human placental lactogen
360
what is the role of human chorionic gonadotrophin?
prolongs life of cor[us luteum
361
what is the role of oestrogen in the placenta?
stimulates uterine growth and development
362
what is the role of progesterone released by the placenta?
stabilises uterus and prevents myometrial contractions
363
what is the role of human placental lactogen released from the placenta?
growth hormone like activity
364
what are the 5 main human maternal changes during pregnancy?
```
uterus expands
blood volume increases
heart workload increases
kidneys filter more blood
woman gains on average 10-15kg of weight
```
365
what are the 2 main requirements for parturition?
coordinated contractions of myometrium to expel foetus
| softening and reduced resistance of cervix
366
is the mechanism of parturition common to all mammals?
yes
367
what aspect of parturition differs within species?
the trigger
368
how is parturition initiated in the goat?
levels of circulating hormones change
369
how do levels of hormones change in the goat to initiate parturition?
progesterone and oestrogen switch (progesterone increases, oestrogen decreases)
levels of prostaglandin rise
370
is there change in hormone levels in humans to initiate parturition?
no change in oestrogen:progesterone ratio
| prostaglandin levels do not change until well into labour
371
describe the initiation of parturition in the goat
foetus produces steroids from adrenal gland
leads to increased oestrogen production in the placenta
PGF2alpha synthesis increases so myometrial excitability increases
oxytocin release is enhanced by distention of cervix and vagina
372
what provides the initial stimulus for initiation of parturition in the goat?
the foetus
373
what is the effect of increased oestrogen release from the placenta on the myometrium during labour?
increase in excitation and calcium
increased oxytocin receptors
increased PGF2alpha release
374
what is the role of oxytocin?
amplifies effects of oestrogen on myometrium
375
what is the effect of PGF2alpha?
softening of cervix
376
what is thought to initiate parturition in humans?
changes in local receptor populations
377
what happens during stage 1 of parturition?
overt uterine contractions
positioning of the foetus
dilation of the cervix
transition leading to stage 2
378
what happens during transition to stage 2?
contractions of the myometrium change
379
what happens during stage 2 of parturition?
expulsion of foetus
380
when does stage 2 of parturition start?
full dilation of cervix
381
what hormone is the uterus highly sensitive to during stage 2?
oxytocin
382
what is oxytocin release enhanced by?
vaginal stimulation
383
what happens during stage 3 of parturition?
expulsion of placenta
| involution of uterus
384
what is the goal of involution of the uterus?
prevents excessive blood loss
385
what type of tissue are mammary glands formed of?
glandular tissue
386
how is glandular tissue arranged to form mammary glands?
alveoli that in turn are arranged in clusters
387
what are milk secreting cells formed of?
single layer of epithelial cells surrounded by myoepithelial cells
388
what is the hormonal stimulus for lactation?
sudden decline in oestrogen and progesterone and increased secretion of prolactin
389
where do epithelial cells secrete milk into?
alveoli/lumen
390
what is lactation maintained and initiated by?
prolactin from anterior pituitary
391
what is required to initiate and maintain lactation?
suckling to stimulate hormone release
392
what is milk release stimulated by?
action of oxytocin on myoepithelial cells
393
what happens during the milk ejection reflex?
contraction of myoepithelial cells to expel milk from alveoli
394
where is oxytocin secreted from?
posterior pituitary
395
what is milk ejection reflex and maintenance of lactation initiated by?
mechanical stimulation of nipple
396
what does milk production require?
prolactin and suckling
397
what does milk ejection require?
oxytocin
398
can milk ejection occur without stimulation of the nipple?
yes - is a conditioned reflex
399
define contraception
the prevention of pregnancy and disease
400
what are the 2 main contraceptive options?
hormonal and barrier
401
how does a lot of hormonal contraception work?
negatively feeds back on/inhibits GnRH and LH/FSH so that ovulation does not occur
402
what is the mode of action of the combined pill?
negative feedback on gonadotrophins (GnRH) to inhibit ovulation
403
what are the advantages of the combined pill?
high efficacy
regular/controlled menstruation
acne may improve
404
what are the disadvantages of the combined pill?
low risk venous thrombosis
breast/cervical carcinoma
can't be used while lactating as partially suppresses lactation
405
why does the combined pill suppress lactation?
oestrogen inhibits milk production
406
what is the mode of action of the progesterone only pill?
makes cervical mucous hostile to sperm
407
what are the advantages of the progesterone only pill?
can be used in lactating women
408
what are the disadvantages of the progesterone only pill?
less effective than combined pill
| need for meticulous timing
409
what is the mode of action of the morning after pill?
delays ovulation beyond lifespan of sperm
| prevents sperm transport
410
what are the advantages of the morning after pill?
95% success if used within 24 hours
411
what are the disadvantages of the morning after pill?
lower success if delayed to 72hrs
| provides no protection for rest of cycle
412
what is the mode of action of progesterone devices (IUD, implant or injection)?
similar to progesterone pill but may also prevent ovulation
413
what are the advantages of progesterone devices (IUD, implant or injection)?
high efficacy
cost effective
prevents ovulation
414
what are the disadvantages of progesterone devices (IUD, implant or injection)?
requires medical intervention
| prolonged amenorrhea may follow cessation
415
what are the 2 main options for male contraception?
testosterone/progesterone combinations
| blocking testosterone temporarily
416
how would testosterone/progesterone combinations aid prevention of pregnancy?
suppression of gonadotrophins and prevention of sperm production
417
how would blocking testosterone aid prevention of pregnancy?
inhibition of sperm production by lowering systemic testosterone
418
what is a disadvantage of blocking testosterone to prevent pregnancy?
fails to suppress spermatogenesis in all men
419
what is lactational amenorrhea?
breastfeeding can act as a contraceptive in 60-70% of lactating mothers
420
how does lactation act as a contraceptive?
suppresses follicular development
disrupts pulsatile action of GnRH - no LH surge
interferes with corpus luteum function
421
what is the mode of action of the copper coil?
prevents fertilization as toxic to sperm
422
what is the mode of action of the hormonal coil?
local progesterone release impairs implantation and fertilization
423
after what age does female fertility decline?
35
424
what are the 3 main classes of disorder that contribute to most infertility cases?
disorders of female tract
disorders of ovulation
poor quality spermatozoa
425
are many cases of infertility explained?
no - high proportion don't have a known cause
426
what is ART?
assistive reproductive technologies
427
what does ART include?
```
fertility drugs
intra uterine insemination
in vitro fertilisation
in vitro maturation
intracytoplasmic sperm injection
embryo testing
cryopreservation
```
428
what are fertility drugs used to overcome?
anovulation
429
what is the role of anti-oestrogens?
block oestrogen receptors in hypothalamus and pituitary which release negative feedback of oestrogen and so increases release of FSH and LH leading to increased likelihood of LH surge and ovulation
430
what is the role of gonadotrophins?
stimulates follicular growth
431
what are gonadotrophins often used in conjunction with?
IVF treatment cycles
432
how is the natural cycle suppressed during IVF?
administration of GnRH agonist
433
what is the role of the GnRH agonist in suppressing the natural cycle in IVF?
prevents endogenous LH surge and premature ovulation
434
how does ovulation hyperstimulation occur during IVF?
using recombinant FSH followed by injection of LH or human chorionic gonadotrophin to mature follicles
435
how are eggs collected for IVF?
needle passes through vaginal wall and into follicle to retrieve egg
436
what happens when eggs are fertilized during IVF?
incubated in sperm harvested from male partner in vitro for 24-48 hours
437
when does embryo transfer occur?
at 4 cell stage
438
how is the embryo placed in the uterus?
transcervical catheter
439
what is administered to aid egg implantation after embryo transfer?
progesterone
440
what happens during cryopreservation?
any remaining fertilised oocytes/embryos may be frozen for later use
441
what are the 2 key reasons for embryo testing?
preimplantation genetic screening to check for chromosome abnormalities
pre implantation tissue typing for saviour siblings
442
what are the 4 main dangers of ART?
multiple births
ovarian hyperstimulation syndrome
lower birth weight
congenital abnormalities
443
what is the purpose of mitochondria replacement?
targets diseases caused by faulty mitochondria
444
what happens during pronuclear transfer?
parent and donor eggs are fertilized by father
parents nuclear material removed and transferred into donor egg (nuclear material removed) which is healthy
then implanted as with IVF
