Lectures 3 & 4 - Male Reproduction - Jan 13 & 15, 2025 (1) Flashcards
(101 cards)
1
Q
What are gonads?
A
Primary reproductive organs made up of a pair of testes in males and a pair of ovaries in females.
2
Q
What are the two main functions of mature gonads?
A
- Producing gametes (gametogenesis)
- Production of sex hormones
3
Q
What is spermatogenesis?
A
The process in males that gives rise to spermatozoa or sperms.
4
Q
What is oogenesis?
A
The process in females that gives rise to the ova or egg.
5
Q
What hormones are produced in males?
A
Testosterone.
6
Q
What hormones are produced in females?
A
- Estrogen
- Progesterone
7
Q
What are the components of male internal genitalia and accessory sex organs?
A
- Testes
- Epididymis
- Vas deferens
- Seminal vesicles
- Ejaculatory duct
- Prostate
- Bulbourethral (Cowper) glands
- Urethra
- Penis
8
Q
What does the prostate gland secrete?
A
A slightly acidic milky fluid that makes up 50-75% of the volume of semen.
9
Q
What is the pH nature of semen?
A
Overall nature is alkaline due to fluid from the seminal vesicle.
10
Q
Where do spermatozoa form?
A
In the seminiferous tubules.
11
Q
What are Sertoli cells?
A
Cells that support spermatogenesis in the seminiferous tubule.
12
Q
What do Leydig cells produce?
A
Testosterone.
13
Q
What initiates spermatogenesis?
A
Sertoli cells.
14
Q
What is the role of the hypothalamus in hormone regulation?
A
Produces neurohormones called hypothalamic releasing hormones that stimulate or inhibit the release of pituitary hormones.
15
Q
What are the six peptide hormones synthesized by the anterior pituitary?
A
- GH (Growth Hormone)
- TSH (Thyroid Stimulating Hormone)
- ACTH (Adrenocorticotropic Hormone)
- LH (Luteinizing Hormone)
- FSH (Follicle Stimulating Hormone)
- PRL (Prolactin)
16
Q
What does GHRH stimulate?
A
Release of Growth Hormone (GH) from somatotrophs in the anterior pituitary.
17
Q
What is the function of AVP (Arginine Vasopressin)?
A
Increases water permeability in the collecting duct.
18
Q
What is the role of oxytocin (OT)?
A
Stimulates uterine contraction and milk production.
19
Q
What does GnRH stimulate in the anterior pituitary?
A
- Release of FSH
- Release of LH
20
Q
What are the primary functions controlled by the male hypothalamic-pituitary-gonadal axis?
A
- Production of male gametes (spermatogenesis)
- Androgen biosynthesis
21
Q
What is the structure of GnRH?
A
A decapeptide synthesized as a prohormone with 69 amino acids.
22
Q
What is the effect of LH on Leydig cells?
A
Stimulates the transcription of proteins involved in testosterone biosynthesis.
23
Q
What does FSH bind to in Sertoli cells?
A
Receptors on the basolateral membrane.
24
Q
True or False: The secretion of GnRH is pulsatile.
A
True.
25
Fill in the blank: The anterior pituitary regulates ______ and stress response.
reproduction
26
What is the role of Luteinizing Hormone (LH) in the male reproductive system?
Stimulates synthesis and secretion of testosterone from Leydig cells
## Footnote
LH binds to receptors on Leydig cells, promoting testosterone biosynthesis.
27
What does Follicle-Stimulating Hormone (FSH) stimulate in Sertoli cells?
Gene transcription and protein synthesis
## Footnote
FSH binds to receptors on Sertoli cells, leading to the production of various proteins.
28
What are the two routes of negative feedback on the hypothalamic-pituitary-testicular axis?
* Testosterone inhibits GnRH release
* Inhibin inhibits FSH release
## Footnote
Testosterone acts on hypothalamic neurons and gonadotrophs in the anterior pituitary.
29
Which hormones belong to the family of glycoprotein hormones?
* Luteinizing Hormone (LH)
* Follicle-Stimulating Hormone (FSH)
* Human chorionic gonadotropin (hCG)
* Thyroid-Stimulating Hormone (TSH)
## Footnote
All these hormones consist of two polypeptide chains, α and β.
30
What is the function of androgen-binding protein (ABP)?
Keeps local testosterone levels high in the seminiferous tubule
## Footnote
ABP is synthesized in response to FSH and is secreted into the luminal space.
31
True or False: The α subunits of LH, FSH, hCG, and TSH are identical.
True
## Footnote
It is the β subunits that differ among these hormones.
32
What is the primary source of testosterone production in males?
Leydig cells
## Footnote
Leydig cells synthesize androgens from cholesterol.
33
Fill in the blank: LH stimulates the synthesis of _______ and _______ in Leydig cells.
Sterol-carrier protein (SCP) and sterol-activating protein (SAP)
## Footnote
SCP and SAP are involved in the transport and activation of steroidogenesis.
34
How does GnRH affect the secretion of LH and FSH?
Stimulates gonadotrophs in the anterior pituitary to release LH and FSH
## Footnote
GnRH is secreted by neurons in the hypothalamus.
35
What happens to FSH and LH levels during early puberty in boys?
Both FSH and LH levels increase
## Footnote
This increase correlates with Leydig cell proliferation and rising testosterone levels.
36
What is the role of inhibins in the male reproductive system?
Feedback inhibition of FSH release
## Footnote
Inhibins are produced by Sertoli cells and play a key role in the hypothalamic-pituitary-testicular axis.
37
What is the effect of testosterone on Sertoli cells?
Stimulates the conversion of testosterone to estradiol
## Footnote
This conversion occurs via aromatase activity in Sertoli cells.
38
What is the relationship between Leydig cells and Sertoli cells?
Crosstalk occurs where Leydig cells produce testosterone, influencing Sertoli cells, which convert some testosterone to estradiol
## Footnote
Sertoli cells also produce growth factors that act on Leydig cells.
39
What is the primary testicular site of FSH action?
Sertoli cells
## Footnote
FSH influences Sertoli cell function and spermatogenesis.
40
What additional role does FSH play in spermatogenesis?
May stimulate sperm motility
## Footnote
This contributes to increased fertility potential.
41
What is the function of P-450 aromatase in Sertoli cells?
Converts testosterone into estradiol
## Footnote
This conversion is essential for male sexual differentiation and reproductive function.
42
What do Leydig cells produce?
Testosterone
## Footnote
Leydig cells are the primary source of testosterone in the testes.
43
What is the role of Sertoli cells in relation to testosterone?
Convert some testosterone to estradiol
## Footnote
Sertoli cells contain aromatase, which facilitates this conversion.
44
What two gonadotropins are required for optimal spermatogenesis?
* LH
* FSH
45
What hormone is therapeutically used to initiate spermatogenesis in oligospermic men?
hCG
## Footnote
hCG is a substitute for LH in this context.
46
What do Sertoli cells produce that affects Leydig cells?
Inhibin and growth factors
47
During early puberty in boys, what happens to FSH and LH levels?
Both FSH and LH levels increase
48
What is the preferred pathway for testosterone synthesis starting from cholesterol?
The pathway begins in the mitochondria with the SCC enzyme.
49
What is the rate-limiting step in testosterone biosynthesis?
Conversion of cholesterol to pregnenolone
50
What is the primary regulator of testosterone synthesis by Leydig cells?
LH
51
What are the main products secreted by the testis aside from testosterone?
* Pregnenolone
* Progesterone
* 17-hydroxyprogesterone
* Androstenedione
* Androsterone
* DHT
52
What type of receptors do steroid hormones bind to?
Intracellular receptors
53
What percentage of plasma testosterone is bound to sex hormone-binding globulin (SHBG)?
About 45%
54
What is the free form of testosterone that exerts biological actions?
Free testosterone
55
What is the function of the androgen receptor?
Acts as a transcription factor
56
What happens when the androgen receptor complex interacts with nuclear chromatin?
Increases transcription of structural genes
57
What genetic condition is associated with the absence or abnormality of the androgen receptor?
Testicular feminization syndrome
58
What type of steroid is testosterone classified as?
A steroid hormone
59
Where is the gene coding for the androgen receptor located?
On the X chromosome
60
What is the role of 5α-reductase in testosterone metabolism?
Converts testosterone to dihydrotestosterone (DHT)
61
What is the main source of circulating testosterone?
Leydig cells of the testes
62
What happens to testosterone that diffuses into a cell?
It binds to a high affinity-androgen receptor or is converted to DHT
63
What type of dimer does the androgen receptor function as?
Homodimer (AR/AR)
64
How do steroid hormones regulate gene transcription?
By binding to hormone-response elements on DNA
65
Which enzymes are involved in the synthesis of testosterone from cholesterol?
* P-450 side-chain-cleavage enzyme (SCC)
* 3β-hydroxysteroid dehydrogenase (3β-HSD)
* 17α-hydroxylase (P-450c17)
66
Where is the gene coding for the androgen receptor located?
On the X chromosome
## Footnote
The androgen receptor (AR) is crucial for androgen action.
67
What is the role of the androgen-AR complex?
It acts as a transcription factor that binds to hormone response elements on DNA
## Footnote
This binding leads to increased transcription of specific genes.
68
What is dihydrotestosterone (DHT) and how is it formed?
DHT is formed from testosterone by the action of cytoplasmic 5α-reductase
## Footnote
DHT binds to the androgen receptor with a much greater affinity than testosterone.
69
What happens to testosterone levels in aging males?
There is a gradual decline in serum testosterone levels
## Footnote
This decline is associated with changes such as decreased bone formation and muscle mass.
70
What is the relationship between testosterone therapy and aging males?
Testosterone therapy can restore muscle and bone mass and correct anemia
## Footnote
It is important for mitigating the effects of aging.
71
What is the primary site of testosterone metabolism?
Mainly in the liver and prostate
## Footnote
Only a small amount is excreted unchanged in urine.
72
What are the two major roles of androgens in male differentiation?
* Trigger conversion of the wolffian ducts to the male ejaculatory system
* Direct differentiation of the urogenital sinus and external genitalia
73
What are the two independent biological actions of androgens?
* Androgenic effects
* Anabolic effects
## Footnote
These effects are organ-specific and arise from the same class of steroids.
74
What is the significance of testicular descent?
It is an androgen-dependent process necessary for optimal testicular function
## Footnote
Abnormalities can lead to conditions like cryptorchidism.
75
What is male pseudohermaphroditism?
A syndrome where individuals have a normal male karyotype but ambiguous external genitalia
## Footnote
This condition arises from defects in androgen action.
76
What is hypospadias?
A developmental anomaly where the urethra opens inferior to its usual location
## Footnote
It is commonly seen in males.
77
What is the role of the autonomic nervous system in the male genital system?
It controls the male genital system through sympathetic and parasympathetic innervation
## Footnote
Both divisions provide dual innervation to the testes, epididymis, and penis.
78
What primarily controls penile erection?
The parasympathetic nervous system
## Footnote
Erection involves relaxation of smooth muscles and increased blood flow.
79
What neurotransmitters are involved in the erection process?
* Acetylcholine (ACh)
* Nitric oxide (NO)
## Footnote
ACh binds to receptors on endothelial cells, leading to NO release.
80
Fill in the blank: The degradation products of testosterone are primarily excreted in the urine as water-soluble conjugates of either _______ or _______.
[sulfuric acid, glucuronic acid]
81
What are the effects of androgens on male secondary sexual characteristics?
They include deepening of the voice and male patterns of hair growth
## Footnote
The voice deepening is due to changes in the size of the larynx.
82
What type of receptors are involved in the stimulation of nitric oxide synthase on endothelial cells?
Muscarinic receptors
## Footnote
Specifically, M3 muscarinic receptors are involved in this process.
83
Which G protein is associated with the stimulation of nitric oxide synthase?
Gαq
## Footnote
Gαq activates phospholipase C (PLC), leading to increased intracellular calcium.
84
What is the primary control system for erection?
Parasympathetic system
85
What physiological changes occur during erection?
Relaxation of smooth muscles, increased blood inflow, increase in volume and rigidity
86
What neurotransmitters are released by parasympathetic postganglionic terminals during erection?
Acetylcholine (ACh) and nitric oxide (NO)
87
What effect does nitric oxide have on vascular smooth muscle cells?
Stimulates soluble guanylyl cyclase to generate cyclic guanosine monophosphate (cGMP), causing vasodilation
88
What does tonic sympathetic activity contribute to?
Penile flaccidity
89
What role do somatic fibers play in erection?
Innervate striated penile muscles, increasing pressure in the corpora cavernosa
90
What is erectile dysfunction?
Inability to develop or maintain an erection during sexual act
91
Name three medications used to treat erectile dysfunction.
* Sildenafil (Viagra)
* Vardenafil (Levitra)
* Tadalafil (Cialis)
92
How do sildenafil, vardenafil, and tadalafil work?
They inhibit cGMP-specific phosphodiesterase type-5, increasing cGMP concentration
93
What is a common side effect of sildenafil?
'Blue vision'
94
What is seminal emission primarily under the control of?
Sympathetic control
95
What causes retrograde ejaculation?
Failure of the internal urethral sphincter to constrict
96
What confirms the presence of retrograde ejaculation?
More than 15 sperm per high-power field in urine specimens obtained after ejaculation
97
What can lead to ejaculatory dysfunction?
Interference with the innervation of the vas deferens and bladder neck
98
Name some medical conditions that can cause retrograde ejaculation.
* Diabetes mellitus
* Multiple sclerosis
99
What pharmacological therapies can treat retrograde ejaculation?
* Phentolamine
* Ephedrine
* Imipramine
100
What is the role of phentolamine in treating retrograde ejaculation?
It is an α-adrenergic antagonist that promotes normal ejaculation
101
What is the effect of imipramine on ejaculation?
Inhibits norepinephrine re-uptake by presynaptic terminals
