25- Male Reproductive Physiology Flashcards
(105 cards)
1
Q
Pulsatile secretion of ______ and ______ stimulates secretion of gonadal steroid hormones, testosterone and estradiol.
A
FSH
LH
2
Q
Increased circulating levels of the sex steroid hormones are then responsible for the appearance of _________ sex characteristics at puberty.
A
Secondary
3
Q
If a _______ analogue is administered in intermittent pulses to replicate the normal pulsatile secretion, puberty is initiated and reproductive function is established. If a long-acting ______ analogue is administered, puberty is not initiated.
A
GnRH
GnRH
4
Q
The two main functions of these are spermatogenesis and secretion of testosterone.
A
Testes
5
Q
The lower temperature of the ________ is essential for spermatogenesis (1-2 degrees C below body temp).
A
Scrotum
6
Q
This is the primary location for the maturation and storage of sperm.
A
Epididymis
7
Q
These provide another storage are for sperm (Ampulla). Secretes fluid rich in citrate and fructose.
A
Vas Deferens
8
Q
These secrete fluid rich in citrate, fructose, prostaglandins, and fibrinogen.
A
Seminal Vesicles
9
Q
These secrete a milky aqueous solution rich in citrate, calcium, and enzymes.
A
Prostate Gland
10
Q
These are epithelium formed by the Sertoli cells, with interspersed germ cells.
A
Seminiferous Tubule
11
Q
These are the most immature germ cells, located near the periphery of the tubule.
A
Spermatogonia
12
Q
These are mature germ cells, located near the lumen of the seminiferous tubule.
A
Spermatozoa
13
Q
These are interstitial cells that lie between the seminiferous tubules.
A
Leydig Cells
14
Q
The adult testis are 80% ________ ________ and 20% CT interspersed with _______ _______.
A
Seminiferous Tubules
Leydig Cells
15
Q
These cells provide nutrients to the differentiating sperm and form tight junctions with each other, creating a barrier between testes and the bloodstream.
A
Sertoli Cells
16
Q
Sertoli Cells secrete an aqueous fluid into the lumen of the _______ _______, which help to transport sperm through them and into the epididymis.
A
Seminiferous Tubules
17
Q
These cells synthesize and secrete testosterone.
A
Leydig Cells
18
Q
Androgens secreted by the testes include…
A
Testosterone
Dihydrotestosterone
Androstenedione
***Testosterone is the most abundant!
19
Q
In target tissues, much of the testosterone is eventually converted into ________.
A
DHT (Dihydrotestosterone)
20
Q
Testosterone is the major androgenic hormone synthesized and secreted by the Leydig cells of the testes. The testes lack _________ and ________ so no glucocorticoids or mineralocorticoids are synthesized.
A
21ß-hydroxylase
11ß-hydroxylase
21
Q
The testes have _________ __________, which converts Androstenedione to Testosterone. The end product of steroid synthesis in the testes is Testosterone, not DHEA or Androstenedione like in the adrenal gland.
A
17ß-hydroxysteroid Dehydrogenase
22
Q
In the lumen of seminiferous tubules, Testosterone is concentrated by binding to ________.
A
ABP (Androgen-Binding Protein)
23
Q
Testosterone is not active in all androgenic target tissues. In some tissues, DHT is the active androgen (i.e., prostate gland in adult and external genitalia of male fetus, skin, liver). _________ in peripheral tissue converts Testosterone to DHT.
A
5 alpha-reductase
24
Q
Most of the circulating testosterone is bound to plasma proteins and albumin. Also a specific protein called…
A
SHBG (Sex Hormone-Binding Protein)
25
Leydig cells synthesize _________ de novo. They can also acquire it from the circulation, through LDL receptors and HDL receptors.
Cholesterol
26
Leydig cells store cholesterol as as cholesterol esters. Free cholesterol is generated within the testis, particularly within Leydig cells, by a...
Cholesterol Hormone-Sensitive Lipase (HSL)
***HSL converts cholesterol esters to free cholesterol for androgen production!
27
Once free cholesterol is produced, it is then transferred within the mitochondrial membranes via the _______. Here, the cholesterol is then converted to ________.
StAR (Steroidogenic Acute Regulatory Protein)
| Pregnenolone
28
Small amounts of estrogens are formed in the male. In the fluid of the ________ ________, the estrogens is quite high.
Seminiferous Tubules
29
In the seminiferous tubules, the putative source of estrogen is the _______ _______ via the product of the conversion of testosterone to estradiol, mediated by aromatase. Human sperm cells also express at least one isoform of the estrogen receptor (ER).
Sertoli Cells
30
Much larger amounts of estrogens are formed from testosterone and androstenediol in other tissues of the body, especially the ________. Accounts for as much as 80% of total male estrogen production.
Liver
31
Describe the mitochondrial pathway for testosterone synthesis and what its rate limiting step is.
Cytochrome P450SCC enzyme removes the side-chain (carbons 22-27) from the carbon at position 20 of cholesterol.
****RATE LIMITING STEP = conversion of cholesterol to pregnenolone
32
Leydig cells make limited amounts of DHT and estradiol-17B. Testosterone diffuses into the seminiferous tubules and into the peritubular capillary network to be carried into the circulation. In seminiferous tubules, Testosterone is concentrated by binding to _______. Testosterone is carried in the peripheral circulation by ______ and ______.
ABP
SHBG
Albumin
33
______ stimulates the conversion of cholesterol to pregnenolone and regulates the overall rate of testosterone synthesis by the Leydig cells.
LH
34
LH promotes pregnenolone synthesis in two ways, which are...
-- Increase affinity of P450SCC enzyme for cholesterol
-- Stimulate synthesis of P450SCC enzyme (long-term action)
***Another name for P450SCC enzyme is cholesterol desmolase!
35
Androgens diffuse to target cells and bind to ________ ________. This complex is a nuclear receptor which directs protein synthesis.
Androgen Receptors (AR)
36
_______ also binds to androgen receptors, however with greater affinity. Plays an important role in causing changes at puberty. Deficiency of 5a-reductase results in ambiguous external genitalia.
DHT
37
As T enters the peripheral circulation, it quickly reaches equilibrium with serum proteins. 60% of circulating T is bound to _______, 38% of circulating T is bound to _______, and 2% remains as free T (most important biologically form).
SHBG
| Albumin
38
T and its metabolites are excreted primarily in the urine. About 50% of excreted androgens are found as urinary ________. Remainder being conjugated androgens or diol or triol derivatives.
17-ketosteroids
39
What enzyme converts Testosterone to Estradiol in the peripheral tissues and the testes?
Aromatase
40
What are specific actions of DHT?
- - Fetal differentiation of external male genitalia
- - Male hair distribution and male pattern baldness
- - Sebaceous gland activity
- - Growth of the prostate
41
Because the growth of the prostate gland and male pattern baldness depend on DHT rather than testosterone, ________ inhibitors can be used as treatment for benign prostatic hypertrophy and hair loss in males.
5a-reductase
***Excess DHT causes hair loss!
42
What are the androgenic actions?
-- Regulation of differentiation of male internal and external genitalia in fetus
-- Stimulation of growth, development of secondary sexual characteristics at puberty
-- Maintenance of reproductive tract and production of semen
-- Initiation and maintenance of spermatogenesis
43
By age 80, over 80% of men will have _______ _______ _______. Signs and symptoms include urinary frequency, urinary urgency, nocturia (excessive urination at night), difficulty initiating and maintaining a urinary stream, and dribbling.
Benign Prostatic Hyperplasia (BPH)
44
The concentrations of DHT in prostatic tissue are NOT higher in men with BPH than in those without BPH. BPH patients might have more _______ _______ on their prostates.
DHT Receptors
45
What is the intracellular mechanism of action for Leydig cells, resulting in steroidogenesis and testosterone production?
LH receptor (GPCR) and activates a cAMP-PKA pathway
46
After being produced by Leydig cells, testosterone diffuses into _______ _______ and peripheral circulation.
Seminiferous Tubules
47
What is the intracellular mechanism of action for Sertoli cells, resulting in protein synthesis and production of inhibin, APB, aromatase, and other products?
Stimulated by testosterone and FSH via its receptor (GPCR) and activates a cAMP-PKA pathway
48
FSH stimulates the Sertoli cells to secrete _______ into the lumen of the seminiferous tubules. Binding of testosterone to this in the lumen provides a local testosterone supply for the developing spermatogonia.
ABP
49
In Sertoli cells, testosterone is also converted to ________ via the enzyme Aromatase.
Estradiol-17ß
50
What are the 3 types of functions that Sertoli cells have?
Supportive
Exocrine
Endocrine
51
Spermatogenesis occurs along the seminiferous tubules. The seminiferous tubules are lined by a complex stratified epithelium containing two distinct populations of cells. ________ ________ that develop into spermatozoa, and ________ ________ which have a supportive and nutrient function.
Spermatogenic Cells
| Sertoli Cells
52
The entire process of spermatogenesis takes about _______ days. The process is staggered to allow a group of cells to enter maturation every 16 days.
64
53
Spermatogenesis has 3 phases, which are...
1) Mitotic Divisions
2) Meiotic Divisions
3) Spermiogenesis
54
At the end of mitosis, what is the result of spermatogenesis?
Type A and Type B Spermatogonia (2N)
***Type A repeats the process of mitosis, while Type B continues on to meiosis.
55
Describe the path of spermatogenesis through Meiosis I.
Spermatogonia (Type B - 2N) ---
Primary Spermatocytes (diploid 4N) ---
Secondary Spermatocytes (haploid 2N)
56
Describe the path of spermatogenesis through Meiosis II.
Secondary Spermatocytes (haploid 2N) ---
Spermatids (haploid 1N)
57
The mitotic division (spermatocytogenesis) is the proliferative phase. At puberty, mitotic cycles increase and spermatogonia or stem cells divide to produce daughter spermatogonia. After the last division, the resulting cells are called...
Primary Spermatocytes (diploid 4N)
58
During Meiosis (production of the haploid gamete), Primary Spermatocytes undergo two meiotic divisions. The first division produces two ________ _________, each with a haploid number of duplicated chromosomes.
Secondary Spermatocytes (haploid 2N)
59
Secondary Spermatocytes enter a second meiotic division, producing two ________, each with a haploid number of unduplicated chromosomes.
Spermatids (haploid 1N)
60
Spermiogenesis (maturation) occurs Spermatids mature into __________. Nuclear and cytoplasmic changes occur and ends in the testis with the release of _________ from Sertoli cells.
Spermatozoa
| Spermatozoa
61
This hormone is secreted by the anterior pituitary and stimulates the Leydig cells to secrete testosterone.
LH (Luteinizing Hormone)
62
This hormone is secreted by the anterior pituitary and stimulates the Sertoli cells to nurse and form sperm. Without this stimulation, spermiogenesis will not occur.
FSH (Follicle-Stimulating Hormone)
63
This hormone is necessary for controlling background metabolic functions of the testes. It promotes early division of the sperm themselves and without it, as seen in pituitary dwarfs, spermatogenesis is severely deficient or absent rendering them infertile.
GH (Growth Hormone)
64
This is secreted by Leydig cells, and is essential for growth and division of the testicular germinal cells, which is the beginning of sperm formation.
Testosterone
65
This is formed from the testosterone by the Sertoli cells when they are stimulated by FSH. Might also be essential for spermatogenesis.
Estrogens
66
Sperm spend an average of a month in the _________ undergoing further maturation after release from the Rete Testis. Sperm are weakly motile upon entering, but strongly motile upon exiting.
Epididymis
***Can be storage site for mature sperm for several months!
67
_________ of the sperm occurs in the Epididymis, which involves adding molecules to the membranes of sperm to prevent the acrosomal reaction before contact with an egg.
Decapacitation
68
These secrete a mucoid material containing: fructose, citric acid, and other nutrient substances, as well as prostaglandins and fibrinogen. Adds considerable nutrient value for the ejaculated sperm.
Seminal Vesicles
69
In Seminal Vesicles, _________ aid in fertilization by reacting with the female cervical mucus to make it more receptive to sperm movement (make cervical mucus less thick). Also causes backward, reverse peristaltic contractions in the uterus and fallopian tubes to move the ejaculated sperm toward the ovaries.
Prostaglandins
70
This secretes a thin, milky fluid that contains Calcium, citrate ion, phosphate ion, a clotting enzyme, and a profibrinolysin. This is secreted during emission.
Prostate Gland
71
The slightly (ACIDIC/ALKALINE) prostatic fluid helps neutralize the acidity of the other seminal fluids during ejaculation and thus enhances the motility and fertility of the sperm.
Alkaline
72
This is composed of fluid and sperm from the Vas Deferens, fluid from the Seminal Vesicles, fluid from Prostate, and small fluid amounts from the mucous glands (bulbourethral gland). Final pH = 7.5
Semen
73
Once sperm cells are ejaculated in the semen, their maximal life span is 24-48 hours at body temperature. Each ejaculation contains 20-200 million sperm. Less than ________ sperm means a man is infertile.
20 million
74
Once spermatozoa emerge from the ________ _______, they leave the gonad and enter the extratesticular portion of the reproductive tract (epididymis and beyond).
Efferent Ductules
75
An erection is a neurovascular event, and there are 3 erectile bodies in the penis which are...
2 Corpora Cavernosa
| 1 Corpus Spongiosum
76
During the flaccid state, blood flow to the erectile tissue is minimal due to _________ of vasculature. ________ allows blood to flow into the spaces, causing engorgement and erection.
Vasoconstriction
| Vasodilation
77
During erection, (SYMPATHETIC/PARASYMPATHETIC) nerves innervating the vascular smooth muscle of the helicine arteries that supply blood to the cavernous spaces release NO.
Parasympathetic
78
NO activates guanylyl cyclase, which increases ________, and ultimately decreases intracellular ________ and causes relaxation of the vascular smooth muscle.
cGMP
| Calcium
79
The engorged tissue presses the veins against a noncompliant outer fascia, reducing venous drainage. ________ stimulation also increases contraction of muscle at the base of the penis, further promoting erection.
Somatic
80
This is the movement of semen from the epididymis, vas deferens, seminal vesicles, and prostate to the ejaculatory ducts. It is under sympathetic control and causes sequential peristaltic contraction of smooth muscle of vas deferens, closing the internal sphincter of the bladder.
Emission
81
Closure of the internal sphincter of the bladder prevents _________ ejaculation of the semen into the bladder.
Retrograde
82
T/F. Emission normally precedes ejaculation but also continues during ejaculation.
True
83
This is the propulsion of semen out of the male urethra.
Ejaculation
84
Ejaculation is caused by the rhythmic contraction of the __________ and _________ muscles, which surround the base of the penis. These striated muscles are innervated by somatic motor nerves.
Bulbospongiosus
| Ischiocavernous
85
Sperm are mature when they leave the epididymis, but their activity is held in check by secretions from the genital duct epithelia. The changes that occur when they come in contact with the fluids of the female tract allow for __________ of the sperm.
Capacitation
86
What occurs during capacitation of the sperm?
-- Uterine and Fallopian Tubes wash away inhibitory factors
-- Loss of cholesterol on acrosome
-- Membrane of sperm more permeable to calcium, increasing its motility
87
Large quantities of _________ and proteolytic enzymes are stored in the acrosomal head of the sperm.
Hyaluronidase
88
Hyaluronidase depolymerizes Hyaluronic Acid polymers in the intercellular cement that hold the ovarian _________ cells together. The proteolytic enzymes digest proteins in the structural elements of tissue cells that adhere to the ________.
Granulosa
| Ovum
89
T deficiency during 2nd-3rd month of gestation results in varying degrees of ambiguity in the male genitalia. This is called...
Male Pseudohermaphrodism
***Also called intersex or DSD
90
T deficiency during the 3rd trimester of pregnancy leads to problems in testicular descent, called _________, along with micropenis.
Cryptorchidism
91
T deficiency leads to poor secondary sexual development and overall ________ features.
Eunuchoid
***Eunuchoidism: persistence of prepubertal characteristics, and often by the presence of characteristics typical of the opposite sex
92
T/F. T deficiency post-puberty leads to decreased libido, erectile dysfunction, decrease facial and body hair growth, low energy, and infertility.
True
93
This is a genetic disorder that occurs when GnRH neurons fail to migrate into the hypothalamus during embryonic development. Characterized by delayed or absent puberty an an impaired sense of smell. Occurs more often in males than females.
Kallman's Syndrome
***Form of hypogonadotropic hypogonadism
94
This is a disorder when a male has an extra X chromosome. Individuals are phenotypically male because of the presence of the Y chromosome and appear male at birth. At puberty, increased levels of gonadotropins fail to induce normal testicular growth and spermatogenesis.
Klinefelter Syndrome
95
In Klinefelter Syndrome, androgen production is usually (HIGH/LOW) whereas levels of gonadotropins are usually (HIGH/LOW), thereby indicating primary hypogonadism.
Low
| High
96
In Klinefelter Syndrome, ________ ________ are largely destroyed, resulting in infertility.
Seminiferous Tubules
***Klinefelter also called Seminiferous Tubular Dysgenesis
97
In a testicular dysfunction (i.e., Klinefelter's) there is decreased testosterone secretion. This is classified as _______ _______, which means decreased testosterone and increased LH.
Primary Hypogonadism
98
In a pituitary dysfunction (i.e., tumor) there is decreased LH and FSH secretion. This is classified as ________ _______, which means decreased testosterone and decreased or normal LH.
Secondary Hypogonadism
99
In a hypothalamic dysfunction (i.e., Kallman's) there is decreased GnRH secretion. This is classified as _________ _________, which means decreased testosterone and decreased or normal LH.
Secondary Hypogonadism
100
Male-pattern baldness is caused by ________ and treated by 5a-reductase inhibitor.
DHT
101
Benign prostatic hypertrophy can be treated with...
5a-reductase Inhibitor
102
As men age, gonadal sensitivity to LH decreases and ________ production stops. As this occurs, serum LH and FSH levels rise (FSH > LH).
Androgen
103
________ decreases slowly after age 40, which causes decreased bone formation, muscle mass, growth of facial hair, appetite, and libido.
Testosterone
104
Small amounts of estrogens are formed in the male. In the fluid of the _______ _______, the estrogens is quite high.
Seminiferous Tubules
105
Over production of _________ from the anterior pituitary can suppress FSH and LH secretion via negative feedback to GnRH.
Prolactin
***Called Hyperprolactinemia
