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Reproductive System > Male Reproductive Physiology > Flashcards

Male Reproductive Physiology Flashcards

1
Q

Name the two main functions of the testes

A
  1. Spermatogenesis

2. Secretion of Testosterone

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2
Q

Name the essential reason why the testes are kept outside of the body. How is that cooler temperature maintained?

A

Essential for normal spermatogenesis.

Maintained by Testicular Arteries and Veins

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3
Q

Describe the composition of the testes.

A

80% - Seminiferous Tubules

20% Leydig Cells

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4
Q

Name the three types of cells that are contained within the Seminiferous Tubules and state their purpose.

A
  1. Sertoli Cells
    • Provide Nutrients to developing Sperm
    • Tight Junctions to create Blood-Testes Barrier
    • Secrete aqueous fluid into the lumen
  2. Spermatogonia - Stem Cells
  3. Spermatocytes - Cells becoming sperm
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5
Q

What is the function of the Leydig Cells?

A

Secrete Testosterone

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6
Q

How many days will a full cycle of spermatogenesis take?

A

64 days

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7
Q

Describe the process of spermatogenesis.

A
  • Mitotic Divisions (of spermatogonia) create spermatocyes. Only TYPE B spermatogonia will undergo mitotic divisions.
  • Meiotic Divisions (of spermatocytes) create haploid spermatids. Spermatids have INCOMPLETE division of cytoplasm to ensure that they are all genomically identical.
  • Spermiogenesis (of spermatids) create mature sperm.
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8
Q

Name the main site for sperm storage and maturation. Where is another site of storage during ejaculation?

A 
Epididymis
Vas Deferens (in the Ampulla)
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9
Q

What is the purpose of the vas deferens?

A

Secretes a fluid rich in citrate and fructose to nourish the ejaculated sperm.

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10
Q

Which components are involved in the secretions of the seminal vesicles?

A

Fructose (main source), citrate, PROSTAGLANDINS, and fibrinogen

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11
Q

There are two main reasons why the seminal vesicles are going to secrete prostaglandins, name them.

A
  1. React with cervical mucus (reduce the thickness) to make it more penetrable by sperm.
  2. Induce backward, reverse peristaltic contractions in the female reproductive tract.
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12
Q

What type of secretion is going to be added to the semen by the prostate gland?

A

Milky alkaline fluid with citrate, calcium and enzymes.

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13
Q

What is the purpose of capcitation and when does it occur?

A

4-6 hours after entering the female tract.

Rearranging the membrane so the sperm can have more Ca2+ influx and they will become more mobile!

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14
Q

What is the purpose of the Acrosomal Reaction?

A

The acrosomal membrane (ovum) is going to fuse to the outer membrane of the sperm and that will allow the sperm to deposit its contents into the ovum.

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15
Q

The synthesis of Testosterone is different in the Testes as it is in the Adrenal Cortex. Describe the differences (2).

A
  1. Testes lack 21B-hydroxylase and 11B-hydroxylase so they cannot make glucocorticoids and mineralocorticoids.
  2. Have 17B-hydroxysteroid dehydrogenase (converts androstenedione to testosterone).
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16
Q

Which enzyme is used to convert Testosterone into Dihydrotestosterone?

A

5a-Reductase

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17
Q

How does testosterone travel through the blood stream?

A
  1. Sex Steroid-Binding Globulin
    • Stimulated by Estrogens
    • Inhibited by Androgens
  2. Albumin
  3. Free
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18
Q

Which form of Testosterone is the biologically active form?

A

ONLY free testosterone is biologically active and can provide negative feedback in the HPA!

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19
Q

Describe the HPA regulation of the Testes

A
  1. Hypothalamus - Secretes GnRH (Arcuate Nuclei)
  2. Anterior Pituitary - FSH (SC) and LH (LC)
  3. Sertoli Cells (Inhibin) and Leydig Cells (Testosterone)
  • Inhibin will inhibit the secretion of FSH from the Anterior Pituitary
  • Testosterone will inhibit the Anterior Pituitary and Hypothalamus.
  • It will also STIMULATE the spermatogenic action of the Sertoli Cells
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20
Q

Name the two functions of testosterone.

A

Paracrine - Acts on Sertoli cells to help FSH with the development of sperm

Endocrine - Secrete in general circulation and is delivered to target tissues

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21
Q

Describe the secretion pattern of GnRH.

A

It is secreted in a Pulsatile pattern that will match the release of FSH and LH from the Anterior Pituitary.

if you administer GnRH continuously, you are going to inhibit the secretion of FSH and LH/

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22
Q

Which enzyme does LH work on to up-regulate testosterone synthesis?

A

Cholesterol Desmolase

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23
Q

FSH and LH are part of a glycoprotein family that has all of the same a-subunits and different B-subunits. Which two other hormones are in this family?

A

TSH and hCG

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24
Q

Which tissues are going to use Testosterone as their biologically active hormone? (10)

A
  • Fetal differentiation of INTERNAL male genetalia (epididymis, vas deferens, and seminal vesicles).
  • Increased muscle mass
  • Pubertal growth spurt
  • Cessation of pubertal growth spurt
  • Growth of wee wee
  • Deepening voice
  • Spermatogenesis
  • Libido
  • CLOSURE of the epiphyseal plate during puberty (Estrogen has a little contribution to the closure also!)
  • At the Liver, INCREASE VLDL and LDL, DECREASE HDL
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25
Q

Which tissues are going to use Dihydrotestosterone as their biologically active hormone?

A

Fetal differentiation of EXTERNAL male genitalia (penis, scrotum, prostate).

Male hair pattern, Male pattern of baldness, SEBACEOUS gland activity, growth of prostate.

26
Q

5a-reductase inhibitors are going to block the conversion of Testosterone into DHT. Which diseases would this be useful in treating and what is the name of the drug?

A

Finasteride

  1. Prostatic hypertrophy
  2. Hair loss in males
27
Q

Describe the relationship between FSH and LH starting in childhood and going to senescence.

A

Childhood: FSH > LH
Puberty: LH > FSH (Due to the LH surge)
Senescence: FSH > LH

28
Q

Name two examples that may delay the onset of puberty.

A
  1. Extreme Stress or caloric deprivation in girls delays the onset of puberty.
  2. Melatonin may be a natural inhibitor of GnRH release. It is secreted by the Pineal Gland and REMOVAL of the Pineal gland will correspond to an early onset of puberty. Melatonin levels are HIGHEST during childhood and DECLINE in adulthood.
29
Q

Where in the hypothalamus is GnRH secreted from?

A

Arcuate Nuclei in the hypothalamus

30
Q

List the events, in order, of puberty in males and females.

A

Males: Pubic Hair - Penile Growth - Growth Spurt
Females: Breast Development - Pubic Hair - Menarche (first menstrual cycle) - Growth Spurt

31
Q

Where in the Testes are you able to store an abundant amount of Testosterone? How is it stored in this structure?

A

Seminiferous Tubules

Testosterone binds to Androgen-Binding Protein (ABP)

32
Q

What are the two end products that are secreted from the Adrenal Glands?

A
  1. DHEA (Dehydroepiandrosterone)

2. Androstenedione

33
Q

Describe the Synthesis and Storage of cholesterol in the Leydig Cells of the Testes.

A

Synthesis: De Novo OR through LDL and HDL receptors
Storage: Cholesterol Esters

34
Q

Name the enzyme that is responsible for the conversion of cholesterol to cholesterol esters in the Leydig Cells of the Testes for storage.

A

Hormone-Sensitive Lipase

35
Q

Describe the processing of cholesterol in the Leydig Cells of the testes.

A
  • Stored as Cholesterol Esters
  • Transferred to Mitochondrial Membrane via Steroidogenic Acute Regulatory Protein (STAR)
  • Cholesterol is then converted to prgenenolone (Through Cholesterol Desmolase)
36
Q

Describe the role of estrogen in sperm product. Where is estrogen found in the highest quantities and which enzyme will convert Testosterone to Estradiol?

A
  • Human sperm cells express at least one isoform of the Estrogen Receptor. Estrogen plays an optimizational role in the process of spermatogenesis.
  • Sertoli Cells
  • Aromatase
37
Q

Which tissues accounts for 80% of Testosterone to Estradiol peripheral conversion?

A

Liver and Adipose Tissue

38
Q

Which compound has a higher affinity for the androgen receptor complex, Testosterone or DHT?

A

DHT

39
Q

How is Testosterone Metabolized?

A
  • 50% is secreted in the urine as 17-ketosteroids

- Remainder will be conjugated androgens, diol or triol derivatives

40
Q

Describe the functions of Testosterone during Fetal Development. (3)

A
  • Presence (penis, scrotum) or Absence (clitoris, vagina) of Testosterone is going to determine genital organs and characteristics
  • Fetal differentiation of INTERNAL male genital tract
  • Causes descent of testes during the last 2-3 months of pregnancy
41
Q

Define Cryptorchidism.

A

Lack of Descent of the Testes related to the lack of Testosterone

42
Q

What are the classic signs with patients that present with Benign Prostatic Hyperplasia?

A

Prostatic Growth is mediated through the actions of DHT!

  • Urinary Frequency (in the night)
  • Difficulty initiating and maintaining a urinary stream
  • By age 80, 80% of men will have BPH
  • BPH patients might have MORE DHT receptors on their protstates! (The [DHT] are NOT higher in men with BPH that those without BPH).
43
Q

LH and FSH receptors will work through which pathway to create new proteins?

A

cAMP-PKA Pathway

44
Q

The Sertoli cells are important for producing _________ which will be important for the destruction of the _________ and the maintenance of the __________ in ducts.

A

Anti-Mullerian Hormone (Mullerian Inhibitory Factor)
Mullerian Ducts
Wolffian Ducts

45
Q

List the Exocrine and Endocrine functions of the Sertoli Cells.

A

Exocrine: Production of Fluid, ABP, Determination of release of sperm from seminiferous tubules

Endocrine: Expression of ABP, T, and FSH receptors; Production of Antimullerian Hormone; Aromatization of testosterone to Estradiol-17B; Production of inhibin to regulate FSH (Males ONLY have Inhibin Type B)

46
Q

When the spermatids undergo spermiogenesis they lose part of their cytoplasm (Residual Body). Which cell is responsible for phagocytizing the Residual Body?

A

Sertoli Cells

47
Q

What happens to the production of testosterone in the testes when you administer an exogenous source of testosterone?

A
  • Testosterone Levels in the blood are going to Increase which is going to negative feedback to occur on the anterior pituitary and hypothalamus
  • This is going to cause a DECREASE in spermatogenesis that is occurring in the testes
48
Q

Describe the testosterone production during the Fetal, Neonatal, Pubertal, Adult and Old age stages of life.

A
  • Fetal: Max @ 2nd Trimester of Gestation and decreases again
  • Neonatal: Spikes again around 1/2 year
  • Pubertal: Starts increasing
  • Adult: Maintains a normal line
  • Old Age: Decreases
49
Q

Describe the composition of the Semen.

A
  • Seminal Vesicles (60%)
  • Prostate (30%)
  • Vas Deferens (10%)
  • Small amounts of secretions from the bulbourethral galnds
  • pH: 7.5
50
Q

How long can a sperm survive after ejaculation in the female reproductive tract?

A

24-48 hours

51
Q

Which component of the nervous system is important for an erectile (“Point”) event? What is the mechanism?

A

Parasympathetic System

Nitric Oxide activates guanylyl cyclase which will INCREASE cGMP and DECREASE intracellular Ca2+, causing relaxation of the vascular smooth muscle of the HELICINE arteries.

52
Q

Which component of the nervous system is important for an ejaculatory event?

A

Somatic Nervous System (Pudendal N.)

Contraction of the Superficial Perineal Ms.

53
Q

Describe the mechanism of Viagra.

A

It is going to block TYPE 5 PHOSPHODIESTERASE which is going to keep cGMP levels HIGH and Ca2+ levels LOW in the erectile tissue of the penis, allowing blood to rush in and maintain an erection.

54
Q

Which component of the nervous system is important for an emission (“Shoot”) event?

A

Sympathetic Nervous System (Hypogastric N.)

Movement of the Ejaculate into the Prostatic Urethra

55
Q

Which two enzymes are stored in the acrosomal head of the sperm in large quantities? What is their function?

A
  1. Hyaluronidase: Depolymerizes the hyaluronic acid polymers that hold the OVARIAN GRANULOSA cells together.
  2. Proteolytic Enzymes: Digest proteins and structural elements that are attached to the ovum.
56
Q

List the different gonadal dysfunctions in a male that are related to Testosterone Deficiency.

A
  1. 2nd-3rd Month of Gestation: Varying degrees of ambiguity in male genitalia
  2. 3rd Trimester: Cryptorchidism
  3. Puberty: Poor Secondary sexual development
  4. Post-Puberty: Decreased libido, erectile dysfunction, low energy, infertility
57
Q

Define Eunuchoidism

A

Persistence of prepuberal characteristics and often by the presence of characteristics typical of the opposite sex.

58
Q

Describe the mechanism of Kallman’s Syndrome.

A

Genetic Disorder when GnRH neurons fail to migrate into the hypothalamus during embryonic development.

  • SECONDARY Hypogonadism
  • Delayed or Absent Puberty
  • Impaired sense of smell
  • Low FSH, LH, and Testosterone (due to NO GnRH)
59
Q

Describe the mechanism of Klinefelters Syndrome.

A

Men have an extra X-chromosome.

  • PRIMARY Hypogonadism
  • Degenesis of the Testes will cause a decrease in the production of Testosterone
  • Levels of GnRH and LH are going to be HIGH
  • Seminiferous Tubules are largely destroyed which leads to infertility.
60
Q

When does Testosterone production begin?

A

7-8 Weeks Gestation

Reproductive System (20 decks)

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