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*GIGU I > 27. Male Reproductive Physiology > Flashcards

27. Male Reproductive Physiology Flashcards

1
Q

Describe the Hypothalamic-pituitary-testicular axis in terms of hormones released

A

Hypothalamus = GnRH

Anterior pituitary = FSH, LH

Testes = testosterone, inhibin

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2
Q

Describe negative feedback via HPT axis

A

Testosterone from testes inhibits GnRH and LH from H and AP

Inhibin and estradiol inhibit FSH and GnRH

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3
Q

What 4 physiological processes are controlled by the hypothalamic-pituitary-testicular axis?

A

Phenotypic gender (embryogenesis)

Sexual maturation (puberty)

Testosterone production

Sperm production

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4
Q

What is the difference between genetic sex, gonadal sex, and phenotypic sex?

A

Genetic sex = XY vs. XX

Gonadal sex = testes vs. ovaries

Phenotypic sex = internal and external genitalia

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5
Q

What hormones determine phenotypic sex?

A

Antimullerian hormone and testosterone (presence = male, absence = female)

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6
Q

80% of the testes composition is _____ ______, which produce sperm

A

Seminiferous tubules

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7
Q

What cell types are found in the seminiferous tubules?

A

Sertoli cells (supportive)

Spermatogonia (stem cells)

Spermatocytes (developing sperm)

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8
Q

If seminiferous tubules make up 80% of the testes, what makes up the other 20%?

A

Connective tissue/interstitium

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9
Q

What cell types are found in the CT/interstitium of the testes?

A

Leydig cells — produce testosterone

Also mast cells, macrophages, nerves, blood vessels, lymph vessels

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10
Q

In terms of hormonal control, Leydig cells are stimulated by _____, and sertoli cells are stimulated by ____

A

LH; FSH

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11
Q

2 Exocrine functions of the sertoli cells

A

Secrete aqueous fluid into lumen of seminiferous tubules —> sperm transport from tubules to epididymis

Produce androgen-binding protein —> binds testosterone and concentrates it in seminiferous tubules

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12
Q

In terms of endocrine function of the sertoli cells, what 3 hormones do they produce?

A

Antimullerian hormone

Inhibin

Aromatase

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13
Q

Action of antimullerian hormone produced by sertoli cells

A

Regression of internal femal genital ducts

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14
Q

Action of inhibin produced by sertoli cells of testes

A

Inhibits FSH

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15
Q

Action of aromatase produced by sertoli cells of the testes

A

Converts testosterone to estradiol-17B

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16
Q

What are the supportive functions of sertoli cells of the testes?

A

Provide nutrients to differentiating sperm (transferrin, Fe, lactate)

Form tight junctions (blood testes barrier)

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17
Q

Leydig cells synthesize and secrete testosterone. They can make their own ______ de novo, or acquire it from circulation

A

Cholesterol

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18
Q

How does GnRH secretion change at puberty? What effects does this have on the rest of the HPT axis?

A

GnRH from hypothalamus becomes pulsatile —> pulsatile FSH and LH secretion from AP —> sex steroid hormon secretion (e.g., testosterone)

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19
Q

What are the 3 primary androgens?

A

Testosterone
Dihydrotestosterone (DHT)
Androstenedione

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20
Q

Androgens bind androgen receptors in reproductive and non-reproductive tissues with varying affinity. Which androgen has the highest affinity in males?

A

DHT has the highest, followed by testosterone, then androstenedione

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21
Q

______ is an active androgen in MOST androgenic target tissues?

A

Testosterone

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22
Q

Testosterone is made in Leydig cells. Where does it go from there?

A

To seminiferous tubules —> peritubular capillaries —> peripheral circulation

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23
Q

Testosterone binds _____ _____ _____in the seminiferous tubules, which leads to its concentration

A

Androgen-binding protein (ABP)

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24
Q

Testosterone binds various proteins in peripheral circulation — what proteins does it primarily bind to and which of these allow it to be biologically active?

A

60% binds sex hormone binding globulin (SHBG) = inactive

38% binds albumin = weakly active

2% is free T = biologically active!

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25
Q

Testosterone production begins at 7-8 weeks gestation. What are its initial roles in development?

A

Stimulates formation of internal male genitalia (epididymis, vas deferens, seminal vesicles), penis, scrotum

Also stimulates testicular descent

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26
Q

Testosterone leads to the development of what secondary sex characteristics at puberty?

A 
Growth spurt
Closure of epiphyseal plates
Acne
Increased muscle mass
Deepening of voice
Body hair
Baldness
Libido
Growth of penis and seminal vesicles
Increased BMR
Increased RBCs
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27
Q

What aspect of sperm development is stimulated by testosterone?

A

Spermatogenesis

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28
Q

What enzyme is responsible for the conversion of testosterone to DHT in target tissues?

A

5-alpha-reductase

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29
Q

T/F: testosterone is an active androgen in most androgenic target tissues, while DHT is only active in some

A

True

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30
Q

What role does DHT play during development?

A

Stimulates development of external male genitalia (penis, scrotum, prostate)

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31
Q

What role does DHT play during puberty?

A

Sebaceous gland activity

Prostate growth

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32
Q

What hormone is often considered responsible for male pattern baldness?

A

DHT

33
Q

The pathogenesis of BPH is poorly understood, but requires androgens, especially ____

A

DHT

34
Q

BPH causes enlargement of periurethral prostate lobes, which compress the urethra. This leads to what type of storage and voiding symptoms?

A

Urinary frequency and urgency, slow stream, dribbling after urination

35
Q

T/F: BPH often represents a malignant process

A

False - it is NOT premalignant!

36
Q

What are 1st and 2nd line tx for BPH?

A

1st line = alpha-1 antagonists which relax smooth muscle in bladder neck and urethra

2nd line = 5-alpha reductase inhibitors which block conversion of testosterone to DHT (less DHT = less hyperplasia)

37
Q

Testosterone can be aromatized to estrogens like estradiol in peripheral tissues and sertoli cells. What actions does this have in males?

A

Bone maturation
Growth acceleration
Breast growth
Role in spermatogenesis

38
Q

In general, male hypogonadism refers to a decrease in ____ and/or _____ production

A

Sperm/testosterone

39
Q

In ______ hypogonadism, or Klinefelter syndrome, the pt is born with ______ chromosome profile, meaning that they have a ____ phenotype

A

Primary; 47 XXY; male (bc they have Y chromosome)

40
Q

What effect does primary hypogonadism have on testis function?

A

Abnormal Leydig cell function — low testosterone production —> high LH —> high estrogen

Seminiferous tubule dysgenesis —> infertility, decreased inhibin leads to high levels of FSH

41
Q

Causes of secondary hypogonadism

A

Nonfunctioning pituitary tumors

Kallmann syndrome

42
Q

Symptoms of secondary hypogonadism d/t nonfunctioning pituitary tumors

A

Pituitary compression leads to low LH and FSH production —> low testosterone —> hypogonadism

Mass effect = visual symptoms, headache

43
Q

Pathogenesis of Kallmann syndrome leading to secondary hypogonadism

A

GnRH neurons fail to migrate into hypothalamus during embryonic development —> low GnRH secretion —> low LH, FSH —> low testosterone

44
Q

Symptoms of secondary hypogonadism due to Kallmann syndrome

A

Delayed/absent puberty
Infertility
Impaired sense of smell (anosmia)

45
Q

Spermatogenesis occurs in the __________, beginning at _____ and continuing throughout life

______ are the immature germ cells present at birth that will undergo this process

A

Seminiferous tubules; puberty

Spermatogonia

46
Q

What are the 3 phases of spermatogenesis?

A

Mitotic division
Meiotic division
Spermiogenesis

47
Q

Phase 1 of spermatogenesis = mitotic division

This phase starts with _______, the immature germ cells which will undergo mitosis to produce ________

A

Spermatogonia

2 primary spermatocytes

48
Q

Phase 2 of spermatogenesis = meiotic divisions

This phase starts with ___________ which undergo 2 meiotic divisions. The first division produces ________, each with a _____ number of duplicated chromosomes

The second division produces ________, each with a _____ number of unduplicated chromosomes

A

Primary spermatocytes; 2 secondary spermatocytes; haploid

2 spermatids; haploid

49
Q

Phase 3 of spermatogenesis = spermiogenesis

This phase starts with ________ which undergo nuclear and cytoplasmic changes to produce mature ______

A

Spermatids; spermatozoa

50
Q

T/F: the entire process of spermatogenesis takes about 25 days

A

False; it takes ~74

51
Q

What are the functional parts of the sperm?

A

Head = fertilization

Tail = motility

52
Q

What are the components of the head of the sperm

A

Nucleus

Acrosome = thick cap, contains enzymes (hyaluronidase, proteolytic enzymes)

53
Q

What are the components of the tail/flagellum of the sperm?

A

Axoneme = central skeleton of microtubules

Mitochondria

Dynein = ATPase

54
Q

Sperm live best in a slightly _____ environment

Increased temperature _______ the lifespan of sperm, hence the role of the scrotum

A

Alkaline

Decreases

55
Q

Lifespan of sperm in testes vs. in female genital tract

A

In testes = 1 month or greater

In female genital tract = 1-2 days

56
Q

What is the role of testosterone in spermatogenesis? What hormone is required for stimulating adequate testosterone secretion?

A

Growth and division of spermatogonia; LH stimuates testosterone

57
Q

What role does FSH play in spermatogenesis?

A

FSH stimulates sertoli cells

58
Q

What role does growth hormone play in spermatogenesis?

A

Early division of spermatogonia

59
Q

What route do sperm take prior to ejaculation?

A

Seminiferous tubules in testes —> epididymis —> vas deferens —> seminal vesicles and ejaculatory duct of prostate —> urethra via bulbourethral glands

60
Q

Where are sperm stored in order to mature and gain coordinated motility, as well as undergo decapacitation?

A

Epididymis

61
Q

________ = addition of molecules to the membranes to prevent premature acrosomal reaction; occurs in epidydimis

A

Decapacitation

62
Q

The vas deferens functions to store sperm in the ______, as well as secretes fluid rich in ____ and _____ to nourish sperm prior to ejaculation

A

Ampulla; citrate; fructose

63
Q

The ________ secrete fluid containing fructose, citrate, prostaglandins, and fibrinogen to nourish sperm.

What role do these prostaglandins play in fertilization?

A

Seminal vesicles

Prostaglandins thin out cervical mucous as well as cause reverse peristalsis in uterus so that sperm can make it to ovaries

64
Q

The 2 ejaculatory ducts empty sperm into the ______, where they are stored as ____ until ejaculation

A

Prostatic urethra; semen

65
Q

The prostate gland secretes slightly _____ fluid containing citrate, phosphate, calcium, and enzymes. This neutralizes the acidity of other seminal fluids, improves ______ of sperm, and aids in fertilization

A

Alkaline; motility

66
Q

The ______ glands secrete clear fluid for lubrication of the urethra prior to ejaculation

A

Bulbourethral

67
Q

What characteristics of semen are examined during lab testing?

A 
Morphology
Motility
Total sperm count
Vitality
Volume
68
Q

During arousal, sensory nerve signals at the glans penis are transmitted via _____ nerve to the sacral spinal cord

A

Pudendal

69
Q

There are 3 total erectile bodis in the penis: 2 ______ and 1 _______

A

Corpora cavernosa; corpus spongiosum

70
Q

During an erection, ________ tone predominates, with _____, _____, and/or _____ NTs participating

A

Parasympathetic; ACh; nitric oxide (NO); VIP

71
Q

What role does nitric oxide play during an erection?

A

NO activates cGMP —> smooth muscle relaxation

Arterial dilation for increased blood flow; increased intercavernosal pressure for cavernosal expansion; veins compressed by engorged tissue leading to reduced venous drainage overall

72
Q

What are some causes of erectile dysfunction?

A

Vascular disease (HTN, DM, atherosclerosis)

Neurogenic

Psychogenic

Endocrinologic

Medication-induced

73
Q

Tx for erectile dysfunction

A

Phosphodiesterase-5 (PDE-5) inhibitors like viagra, which increase cGMP levels in erectile tissue

74
Q

_______ = movement of semen toward ejaculatory ducts, which is under _____ nervous control

A

Emission; sympathetic

75
Q

Emission consists of sequential peristaltic contractions of ________ smooth muscle, causing semen to move into internal urethra, and the ______ sphincter of the bladder closes

A

Vas deferens; internal

76
Q

Ejaculation occurs when there is rhythmic contraction of the _____ and _____ muscles around the base of the penis, increasing the pressure in genital ducts and urethra

A

Bulbospongiosus; ischiocavernosus

77
Q

________ occurs when mature sperm come in contact with fluids in the female tract

A

Capacitation

78
Q

Capacitation involves loss of ________ factors in seminal fluid, loss of _______ on acrosome, which weakens the head of the sperm. There is also increased _____ permeability which leads to improved motility and changes in the cellular membrane allowing for acrosome to release enzymes. The ______ ______ receptors are exposed.

A

Inhibitory; cholesterol; calcium; zona pellucida

79
Q

When the sperm and oocyte meet, the ______ membrane dissolves and enzymes escape. Among these enzymes:

______ breaks down the granuloma cell layer surrounding the ovum

Proteolytic enzymes breakdown tissue cells adhering to ovum, creating a pathway for sperm to pass through _______ and enter ovum so that the cell membranes can fuse and genetic material combines

A

Acrosomal

Hyaluronidase

Zona pellucida

*GIGU I (67 decks)

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