Male Reproductive Physiology Flashcards
1
Q
During childhood, which is secretion of which is higher FSH or LH?
A
FSH in female. Male do not start secretion until after puberty.
2
Q
During puberty, pulsatile secretion of _ drive the pulsatile secretion of _ and _.
A
GnRH
FSH
LH
3
Q
The earliest event in puberty is the appearance of large pulses of LH during _.
A
REM sleep. Large nocturnal pulses of LH.
4
Q
Pulsatile secretion of FSH and LH stimulates the secretion of what other hormones?
A
Gonadal steroid hormones, testosterone, and estradiol
5
Q
Whats responsible for the appearance of secondary sex characteristics at puberty?
A
Increased circulating levels of sex steroids like testosterone and estradiol.
6
Q
Can puberty be initiated and reproductive function established if a GnRH analogue was to be administered in intermittent pulses?
A
Yes
7
Q
True or false. A long-acting GnRH analogue will not initiate puberty.
A
True.
8
Q
True or false: extreme stress or caloric deprivation in girls can cause an early onset of puberty
A
False. It delays it.
9
Q
What acts as a natural inhibitor of GnRH release before puberty?
A
melatonin
10
Q
What are the two main function of testes?
A
- Spermatogenesis
2. secretion of testosterone
11
Q
What is the function of Scrotum?
A
Stores the testes away from the core of the body so that temp within the testes is 1-2 degrees below normal body temp.
12
Q
Where is sperm matured and stored?
A
Epididymis
13
Q
True or False. The vas deferens secretes fluid rich in citrate and fructose.
A
True.
14
Q
What is the function of seminal vesicles?
A
Secretes fluid rich in citrate, fructose, prostaglandins, and fibrinogen
15
Q
What is the function of prostate gland?
A
Secretes milky aqueous solution rich in citrate, calcium and enzymes.
16
Q
Within what structure is sperm produced?
A
Seminiferous tubule.
17
Q
What is the most immature male germ cells located near the periphery of the tubule.
A
Spermatogonia.
18
Q
What is the male mature germ cells located near the lumen of the tubule.
A
Spermatozoa.
19
Q
What makes up the bulk of the adult testis?
A
Seminiferous tubules
20
Q
What are the function of sertoli cells?
A
- provide nutrients to the differentiating sperm
- From tight junctions with each other, creating a barrier between testes and blood
- secrete an aqueous fluid into the lumen of the seminiferous tubules (helps to transport sperm through the tubules into the epididymis)
21
Q
What is the function of Leydig cells?
A
Synthesis and secretion of testosterone
22
Q
what is the most active form of androgens?
A
dihydrotestosterone
23
Q
In the testis what is the main steroidogenic cell?
A
Leydig cells.
24
Q
What is the purpose of fetal leydig cells?
A
masculinizing the male urogenital tract and inducing testis descent.
25
what happens to the fetal Leydig cells after birth?
Atrophies soon after birth. Do not contribute to the adult Leydig cell population
26
when do the adult Leydig cells become active?
At puberty
27
Can Leydig cells synthesize cholesterol de novo?
yes
28
Cholesterol within the Leydig cells are stored as esters, how do they become free cholesterol when needed to make hormones?
Hormone sensitive lipase which is then transferred within the mitochondrial membrane via steroidogenic acute regulatory protien (StAR)
29
The testes cannot make glucocorticoids or mineralocorticoids becuase _
Testes lack 21 beta hydroxylase and 11-beta hydroxlase
30
Unlike in the adrenal gland, the end product of steroid synthesis in the testis is_
testosterone
31
Testosteorne is able to concentrate in the lumen of the seminiferous tubules by binding to _
androgen-binding protein (ABP)
32
testosterone is not active in all tissues, but mainly in prostate gland, external genitalia of the male fetus, skin, and liver. How does testosterone convert to it's more active form dihydrotestosterone in the peripheral tissue?
5-a- reductase
33
Most of the circulating testosterone is bound to _
plasma protein (sex-hormone binding gobulin, SHBG) and albumin
34
True or false, estrogen is not produced in male.
False
35
It was proposed that estrogen in male seminiferous tubules may be produced by _ cells and mediated by the enzyme _ to convert testosterone to estradiol.
Sertoli cells
| Aromatase
36
What is a stimulant for the conversion of cholesterol to pregnenolone in testes?
LH
37
How does LH promote pregnenolone synthesis?
1. Increase affinity of P450SCC (desmolase) enzyme for cholesterol
2. Long-term action in which it stimulates synthesis of P450SCC (desmolase) enzyme
38
Around what week of embryonic development does testosterone begin to produce?
Week 14-15
39
Where are some common locations for androgen receptors in the male?
Prostate, testis (sertoli, Leydig and myoid cell, epididymis, seminal vesicle.
Non-reproductive tissue CNS neurons, anterior pituitary, thyroid, skin, adrenal cortex, liver, kdiney tubules, bladder, cardiac and striated muscle, bone, vasculature
40
What receptors do dihydrotestosterone bind to?
androgen receptors (AR)
41
In fetus, deficiency of 5a-reductase can lead to _
ambiguous external genitalia.
42
50% of excess testosterone is excreted and found as _ form.
17-ketosteroids
43
During puberty, testosterone is responsible for what changes?
1. Increased muscle mass
2. pubertal growth spurt
3. Closure of the epiphyseal plates
4. growth of the penis and seminal vesicles
5. deepening of the voice
6. Spermatogenesis
7. Libido
44
Because of the growth of prostate gland and male pattern baldness depend on _ rather than testosterone, _ inhibitor can be used as treatment for benign prostatic hypertrophy and hair loss in males.
DHT
| 5-a reductase.
45
What are the anabolic actions of androgens?
1. Stimulation of erythropoietin synthesis
2. stimulation of sebaceous gland secretion
3. control of protein anabolic effects (Nitrogen retention)
Stimulation of linear body growth, bone growth and closure of epiphyses
4. Stimulation of androgen binding protein synthesis
5. maintenance of secretion of sex glands
6. regulation of behavioral effects, including libido
46
Leydig cells contain receptor for what hormone?
LH
47
LH receptor is coupled to what signaling pathway resulting in steroidogenesis and testosterone production?
Gs, cAMP-PKA
48
What hormones can stimulate sertoli cells?
Testosterone and FSH
49
FSH receptor is coupled to what signaling cascade and is involved in protein synthesis and production of inhibin?
Gs, cAMP-PKA
50
FSH stimulates sertoli cells to secrete what protein into the lumen of the seminiferous tubules?
androgen-binding protein (ABP)
51
What are the general functions of sertoli cells?
1. Supportive Function
2. Exocine function
3. Endocrine Functions
52
As part of the supportive function of sertoli cells, what specifically do sertoli do?
1. maintain blood-testis barrier
2. phagocytosis
3. transfer of nutrients from blood to sperm
4. receptors for hormones and paracrine
53
what are the exocrine functions of sertoli cells?
1. Production of fluid
2. Production of ABP
3. Determination of release of sperm from seminiferous tubule
54
What are the endocrine function of sertoli cells?
1. Expression of testosterone, ABP, and FSH receptors
2. Production of antimullerian hormone
3. aromatization of testosterone to estradiol 17-beta
4. production of inhibin to regulate FSH levels.
55
Spermatogenesis takes place in what structures?
Occurs along the seminiferous tubules.
56
Seminiferous tubules are lined by what distinct cell population?
Lined by complex stratified epithelium with sertoli cells (which are tall simple columnar cells), and spermatogenic cells which produces the spermatozoa.
57
How long does it take for a spermatogonia to become a spermatozoa?
about 74 days
58
What are the 3 phases of spermatogenesis?
1. Mitotic division
2. Meiotic division
3. Spermiogenesis
59
in the process of spermatogenesis, at the end of mitosis phase, what cells are produced and what are their DNA number (haploid/diploid)
End of mitosis produces spermatogonia which are 2N DNA. These cells are called primary spermatocytes.
60
In the process of spermatogenesis, at the end of the meiotic division phase what cells are produced and what their DNA number (haploid/diploid)?
End of meiosis I, two secondary spermatocytes are produced which are haploid 2N DNA.
At the end of meiosis II, two spermatids are produced which are haploid with 1N DNA.
61
What happens during spermiogenesis?
Spermaids undergo spermiogenesis and mature into spermatozoa; nuclear cytoplasmic changes to produce mature spermatozoa and ends in testis with release of spermatozoa from sertoli cells.
62
True or False, lack of growth hormone can render a male infertile.
True
63
What changes do sperm go through inside the epididymis?
- Undergo further maturation
- Becomes strongly motile
- Decapacitation
- Stores mature sperm
64
Explain the plasma testosterone levels starting from start of fetal development.
Starting the 1st trimester, the fetus begins to produce testosterone and reaches it's peak (about 80% of max) at 2nd trimester and goes back down to zero by the end of third (upside down parabola with 2nd trimester being the peak). After birth, testosterone levels begin to increase to about 50% of maximal until month 6 and then goes back down to zero by the time baby reaches 1. It remains at zero until about 10 when the boy starts to reach puberty. During puberty it gradually increases reaching it's 100% max at about 17-20 and remains at that level until middle age after which it begins to decrease gradually reaching to 50% by 100.
65
Explain the trend for sperm production.
Sperm production begins at mid puberty and reaches it's peak after end of puberty and remains at it's peak late mid age. and follows the same trend as testosterone production.
66
What substances do seminal vesicles secrete?
Secretes mucoid material containing fructose, citric acid, and other nutriends, and prostaglandins and fibrinogen.
67
What role does prostaglandin found in the mucoid material of seminal vesicle secretion play?
- aids in fertilization by reacting with the female cervical mucus to make it more receptive to sperm movement (makes the mucus less thick), and
2. causes backward, reverse peristaltic contraction in the uterus and fallopian tubes to move the ejaculated sperm toward the ovaries.
68
The __ secretes during emission, a thin, milky fluid that contains Ca, citrate ion, phosphate ion, a clotting enzyme and a profibrinolysis.
Prostate gland
69
How does the prostate gland play a role in pH adjustment?
The slightly alkaline prostatic fluid helps neutralize the acidity of the other seminal fluids during ejaculation and thus enhances the motility and fertility of the sperm.
70
During flaccid state, the vascular smooth muscles are constricted or relaxed?
constricted, thus restricting blood flow to the penis.
71
During erection, which ANS component innervates the vascular smooth muscle?
Parasympathetic
72
Which arteries are relaxed during erection and where are they found?
Helicine arteries found on the corpora cavernosa
73
Which neurotransmitter is used by the parasympathetic during erection?
NO
74
Which signaling cascade does NO activate in the process leading to erection?
NO activates guanylyl cyclase increasing cGMP and thus decreases intracellular Ca and causes relaxation of the vascular smooth muscle.
75
What effect does the engorged erectile tissue have on the veins of the penis?
It presses the veins against a noncompliant outer fascia, thereby reducing venous drainage.
76
Emission (the movement of semen from the epididymis, vas deference, seminal vesicles, and prostate to the ejaculatory duct) is under what autonomic control?
sympathetic.
77
During emission, which sphincter of the bladder is closed?
the internal sphincter which prevents semen to go into the bladder.
78
Emission is caused by sequential peristaltic contraction of smooth muscle of _1_, while ejaculation is rhythmic contraction of the _2_.
1. Vas Deferens.
| 2. Bulbospongiosus and ischiocavernosus muscles.
79
what is capacitation?
Takes place in the female genital tract, capacitation is associated with removal of adherent seminal plasma proteins, reorganization of plasma membrane lipids and proteins. It also seems to involve an influx of extracellular calcium, increase in cyclic AMP, and decrease in intracellular pH.
80
What is the sperm acrosome reaction?
The acrosome reaction provides the sperm with an enzymatic drill to get throught the zona pellucida. The same zona pellucida protein that serves as a sperm receptor also stimulates a series of events that lead to many areas of fusion between the plasma membrane and outer acrosomal membrane. Membrane fusion (actually an exocytosis) and vesiculation expose the acrosomal contents, leading to leakage of acrosomal enzymes from the sperm's head.
81
What is the purpose of the hyaluronidase and proteolytic enzymes found in the acrosomal head of sperm?
Hyaluronidase depolymerizes the hyaluronic acid polymers int he intercellular cement that hold the ovarian granulosa cells together. The proteolytic enzymes digest proteins int he structural elements of the tissue cells that adhere to the ovum.
82
Explain what condition can arise, if testosterone was deficiency during these age of onsets:
1. 2nd and 3rd month of gestiona
2. 3rd trimester of pregnancy
3. Puberty
4. Post-puberty
1. Results in varying degrees of amiguity int he male genitalia and male pseudohermaphrodism
2. Leads to problem in testicular descent along with micropenis
3. leads to poor secondary sexual development and overall eunuchoid features
- Eunichoidism: persistence of prepubertal characeristics, and often by presence of characteriscs typical of the opposite sex
4. Leads to decreased libido, erectile dysfunction, decrease facial and body hair growth, low energy and infertility
83
What is male hypogonadism?
Caused by genetic inability to produce GnRH, resulting in low testosterone levels and is thus associated with infantile sex organs.
84
what is Kallman's syndrome?
A genetic disorder - the hypothalamic neurons that are responsible for releasing GnRH fails to migrate into the hypothalamus during embryonic development. Characterized by delayed or absent puberty and an impaired sense of smell.
85
What is Klinefelter syndrome
AKA seminiferous tubular dysgenesis. Men with an extra Y chromosome.
86
What are some characteristics of Klinefelter syndrome?
Primary hypogonadism. Appears normal at birth, but at puberty increased levels of gonadotropins fail to induce normal testicular growth and spermatogenesis. Androgen production is usually low (but this is highly variable among patients). Seminiferous tubules are largely destroyed, resulting in infertility.
87
In primary hypogonadism like Klinefelter's syndrome, what would be the expected levels of T and LH?
decreased T
| Increased LH
88
Pituitary dysfunciton, and Kallman's syndrome are examples of _ hypogonadism
Secondary
89
In secondary hypogonadism what would be the expected levels of T and LH.
decreased T
| Decreased/normal LH
