Control of testicular function and sperm physiology Flashcards
1
Q
main physiological function of the testes
A
- production and release of testosterone
- spermatogenesis
2
Q
what controls the functions of the testes
A
HPG-axis
3
Q
hypothalamus role in HPG axis for testicular function
A
GnRH neurons
- cell bodies in the preoptic acre of the H extend to the median eminence and release GnRH into the pituitary portal blood system
- GnRH is released in regular pulses
4
Q
how is GnRH released
A
regular pulses
5
Q
where are GnRH neurons
A
in the hypothalamus, extend to the medien eminence
6
Q
what releases GnRH
A
GnRH neurons in the preoptic acre of hypothalus
7
Q
pituitary role in HPG axis for testicular function
A
release of LH and FSH from gonadotroph cells in the anterior pituitary in response to GnRH in regular pulses
8
Q
what stimulates release of LH and FSH from gonadotrophs in anterior pituitary
A
GnRH
9
Q
where is LH and FSH released from for testicular function
A
gonadotrophs in the anterior pituitary
10
Q
how are LH and FSH released
A
regular pulses
11
Q
GnRH stimulates the release of
A
FSH and LH
12
Q
LH in males
A
stimulates production of testosterone in testes
13
Q
FSH reproductive role in males
A
stimulates growth and maturation of the testes and spermatogenesis
14
Q
why are testes located outside body
A
for optimum temperature of 35 degrees celsius
15
Q
Anatomy of the testes
A
densley packed network of tubules feeding from testes to the epididymis to the vas deferens
16
Q
what surrounds seminiferous tubulues
A
Leydig cells
17
Q
where are leydig cells
A
surrounding the seminiferous tubulues
18
Q
where does the epididymis lead to
A
vas deferens
19
Q
what simulates the leydig cells
A
LH
20
Q
what do leydig cells release
A
testosterone and other androgens
21
Q
what effect does LH have on leydig cells
A
synthesis and release of testosterone and other androgens
22
Q
main precursor of testosterone
A
pregnenolone
23
Q
what is pregnenolone
A
precursor of testosterone
24
Q
how is pregnenolone formed
A
conversion of cholesterol to pregnenolone by use of cholesterol desmolase, stimulated by LH
25
rate limiting step in formation of testosterone
cholesterol to pregnenolone, by cholesterol desmolase enzyme
26
enzyme for rate limiting step of testosterone formation
cholesterol desmolase
27
cholesterol desmolase
enzyme for rate limiting step of testosterone formation
28
effects of testosterone
- male hormone
- anabolic
- development of primary and secondary sexual characteristics
- libido & sexual behaviour
- stimulates spermatogenesis
29
where does spermatogenesis occur
within the seminiferous tubulues
30
what do seminiferous tubules contains
- spermatogonial stem cells
| - sertoli cells
31
what do sertoli cells do
provide support, nutrition, protection and regulation for spermatogenesis
32
what cells provide support, nutrition, protection and regulation for spermatogenesis
sertoli cells
33
where are sertoli cells
seminiferous tubulues
34
what do spermatogonial stem cells produce
sperm
35
when does spermatogenesis begin
puberty
36
what are the divisions of spermatogenesis
mitosis followed by meiosis
37
rate of sperm production
120 million per day /// 1,500 per second
38
spermatocytogenesis
division of spermatogonial stem cells by mitosis to produce spermatocyte cells and replace themselves
39
DNA content of spermatogonial stem cells
diploid, 46
40
what division do spermatogonial stem cells under go
mitosis - to replace themselves and produce spermatocyte cells
41
how many subtypes of spermatogonial stem cells
3
42
what are the subtypes of spermatogonial stem cells
Type A dark
Type A pale
Type B
43
what do Type A dark spermatogonial stem cells do
replicate by mitosis to provide constant supply of type Ad and type Ap
44
what do Type A pale spermatogonial stem cells do
replicate by mitosis to provide type b cells
45
what do type b spermatogonial stem cells do
divide by mitosis into primary spermatocyte
46
dna content of primary spermatocyte
diploid
47
which spermatogonial stem cells divide to produce primary spermatocyte
Type B
48
spermatidogenesis
meiosis of primary spermatocytes to produce spermatids
49
dna content of spermatids
haploid, 23
50
what divides to produce spermatids
primary spermatocytes
51
spermiogenesis
4 phase process that converts symmetrical spermatids into mature sperm
52
4 phase process that converts symmetrical spermatids into mature sperm
spermiogenesis
53
4 phases of spermiogenesis
- golgi phase
- cap phase
- acrosome phase
- maturation phase
54
golgi phase
- golgi apparatus creates vesicle of enzymes around nucleus on the side that is bound to the sertoli cell
- mitochondria simultaneously moves to other side of the cell
- centriole starts to form an axoneme
55
what is an axoneme
cytoskeletel core of the tail
56
Cap phase
- spermatid DNA condensed in nucleus, excess removed
- golgi surrounds nucleus and enzyme vesicle to form acrosomal cap
- acrosomal cap covers front half of condensed nucelus surrounding sertoli cells
57
what part of does acrosomal cap cover
acrosomal cap covers front half of condensed nucelus surrounding sertoli cells
58
which stage forms the acrosomal cap
cap phase
59
acrosome phase
- axoneme extends into lumen of SFT to become tail
| - temporary cytoskeleton called manchettes bind to nucles to support tail growth
60
what are manchettes
temporary cytoskeleton that bind to nucleus to support tail growth of sperm
61
maturation phase
- excess cytoplasm is phagocytosed by sertoli to produce mature sperm
- mitochondira move to central section of cell called middle piece
62
where do mitochondria go in maturation of sperm
middle piece
63
are mature sperm in SFT motile
no
64
where do mature sperm gain motiltiy
in the epididymis
65
where are mature sperm stored
epididymis
66
what happens to sperm at epididymis
stored and gain motility
67
what regulates sertoli cells
FSH
68
functions of sertoli cells
- form blood-teste barrier
- release androgen binding protein
- release inhibin for feedback on the pituitary
- secrete supporting fluid into the lumen
- phagocytose residual cyctoplasm from spermiogenesis
- release range of proteins such as GDNF and AMH
69
What forms the blood teste barrier
sertoli cells
70
what releases androgen binding protein
sertoli cells
71
what releases inhibin for feedback on the pituitary
sertoli cells
72
what phagocytoses residual cytoplasm from spermiogenesis
sertoli cells
73
where is the blood testi barrier
between blood and the seminiferous tubules
74
how is blood testi barrier formed
tight junctions between sertoli cells form barrier between lumen of SFT and blood vessels
75
purpose of blood teste barrier
- allow sertoli cells to control lumen within the environment
- protects developing sperm from toxins
- separates sperm from autoimmune system
76
why are sperm susceptible to toxins
bc they proliferate so rapidly
77
why must sperm be seperated from the autoimmune system and how
because they are no longer recognised by the body, blood teste barries
78
why is androgen binding protein released
spermatogenesis requires very high levels of testosterone around the developing sperm
79
how does ABP maintain high levels of testosterone for spermatogenesis
binds to testosterone in th elumen making it less lipophillic so it cannot leave. this makes T concentrate in the lumen for increased fertililty
80
what does the binding of ABP to testosterone stimulate
spermatogenesis
81
what does testosterone suppress
LH secretion
82
purpose of inhibin
produced by the sertoli cells to suppress FSH secretion by feedback on the pituitary
83
prolactin in males
immune function, metabolism and male fertility
84
how does prolactin effect male fertility
- increases LH receptor expression on leydig cells
- this increases testosterone release
- increased T = increased spermatogenesis
85
where is prolactin released in males for increasing fertility
pituitary
86
what two systems work closely together to maintain male reproductivity
Leydig cells and seminiferous tubules
87
stages of sperm transport to fertility
difficult journery
- ejaculation
- cervix
- uterus & falloptin tubes
88
ejaculation
deposition of sperm in the vagina
89
cervix in sperm transport
mucuous barrier and crypts that act as sperm reservoirs, sperm motility is important
90
uterus and fallopian tubes in sperm transport
mild contraction to propel the sperm towards th egg
91
where does fetilisation occur
ampullary region of fallopian tube
92
what happens in the ampullary region of the fallopian tube
fertilisation
93
where does sperm capacitation occur
uterus
94
what is sperm capacitation
- chloesterol and glycoproteins are removed from the sperm cell surface by enzymes such as heparin
- sperm is 'switched on' by calcium influx
95
why are cholesterol and glycoproteins removed from sperm cell surface
they limit ion transfer on sperm cell surace
96
how are cholesterol and glycoproteins removed from sperm cell surface
enzymes such as heparin
97
what does heparin do
removed cholesterol and glycoproteins from sperm cell surface
98
how does calcium influx effect sperm
upregulated ion transfer gives mitochondira burst of energy
99
purpose of sperm capacitation
hyperactivity for increased motility
100
acrosome reaction
- interaction with ZP3 protein on the oocyte membrane prevents cross-species fertilisation
- acrosome releases hyaluronidase and acrosin to break through egg coating to allow fertilisation
101
what protein prevents cross species fertilisation and how
ZP3, extremely species specific
102
where is ZP3
ooctye membrane
103
what does ZP3 do
prevents cross species fertilisation
104
what hydrolytic enzymes are released in the acrosome reaction
hyaluronidase and acrosin
105
what type of enzymes are hyaluronidase and acrosin
hydrolytic
106
purpose of hyaluronidase and acrosin
hydrolyse egg coating to allow fertilisation
107
what triggers the acrosome reaction
sperm coming in contact with the oocyte
108
ooctye activation
cortical granules are released and membrane becomes impermeable to other sperm
- male & female pronuclei is formed
109
when is male and female pronuclei formed
ooctye activation
110
when does oocyte activation occur
after fertilisation
111
levels at which teste function can be distrubed
- genetic
- hypothalamic
- pituitary
- target tissue
112
genetic distrubance of tests function
Klinefelter syndrome
113
Klinefelter syndrome
disturbance of teste function at genetic level
114
what is Klinefelter syndrome
male has XXY chromosome
115
syndrom where male has XXY chromosome
Klinefelter syndrome
116
possible effect of Klinefelter syndrome
hypogonadism and reduced fertility
| range of effects, some wont show symptoms
117
hypothalamic disturbance of testes function
Kallman syndrome
118
Kallman syndrome
hypothalamic disturbance of teste function
119
what is Kallman syndrome
- when the GnRH neurones originate from the olfactory region of the brain and so don't migrate to the hypothalamus
- if olfactory mutated, GnRH neurones dont develop at all
120
effects of Kallman sydrome
no reproductive functon and loss of smell cus of olfactory bulb dysfunction
121
pituitary disturbance of testes function
hyperprolactinanaemia
122
hyperprolactinanaemia
pituitary disturbance of teste function
123
effects of hyperprolactinanaemia
abnormally high prolaction
| - in high levels, prolactin inhibits GnRH
124
what happens when there is too much prolactin
instead of upregualting GnRH, in large levels prolactin will inhibit GnRH
125
what causes hyperprolactinanaemia
pituitary tumours
| most commonly a side effect of presciprtion drugs that affect dopamine
126
side effects of hyperprolactinanaemia in males
decreased libido and reduced fertilty
127
target tissue level disturbances of teste function
androgen insensitivity syndrome
128
androgen insensitivity syndrome
target tissue level disturbances of teste function
129
what causes androgen insensitivity syndrome
genetic defects in androgen receptors that reduce sensitivty to testosterone and other androgens
130
symptoms of androgen insensitivity syndrome
varies, depending on level of insensitivity
| males can develop uterus or uterus and testes, but will still be genetically male
131
what causes devlopment of internal female genitalia in males
complete androgen insensitivity casuing hyperandrogemia
132
complete androgen insensitivity
zero response to testosterone and so female internal genetalia devlop despite XY chromosomes
133
why is a male contraceptive pill difficult?
sperm have high proliferation rate, compared to females who produce one egg
134
what are the current effects of a male contraceptive pill
they can reduce rate of sperm proliferation, but not switch off
135
effect of steroids on male fertility
anabolic steroids like testosterone reduce fertility by supressing HPG axis through nagative feedback which switches off LH production
136
how do anabolic steroid reduce male fertility
by supressing HPG axis through nagative feedback which switches off LH production
137
non hormonal factors that effect sperm production
- environment
- climate
- radiation (?)
- air pollutio
- food chain pollution
- stress
138
how do non-hormaon factors effect sperm
they increase oxidative stress leading to sperm damage
139
what does oxidative stess do to sperm
```
causes:
- protein damage
- lipid peroxidation
- biommembrane damage
- dna damage
= sperm damage
```
