Male Physiology

Question 1

Answer 1

Question 2

Answer 2

Question 3

Where does spermatogenesis occur?

Answer 3

Intratubular compartment of seminiferous tubules

Question 4

Answer 4

Question 5

Which of these cells are the sertoli cells?

Answer 5

St –> longer cells

Question 6

Seminiferous tubules are contained by […]

Answer 6

Perytubular myoid cells

Question 7

Answer 7

Question 8

Leydig Cells

• What do they do?
• What activates them?
• When do we see peak amounts of them?

Answer 8

Question 9

Sertoli Cells

• What are the many functions of these cells?
• What signals do they respond to to execute functions?

Answer 9

• Functions:
  
  • Support spermatogenesis
  • Maintain blood-testis barrier through tight junctions, adherens junctions, and gap junctions
  • Secrete testicular fluid that is rich in hormones, enzymes and nutrients
  • Secrete androgen binding protein and inhibin
  • Phagocytosis to clean up remnants of spermatogenesis
• Testosterone from Leydig cells and FSH from AntPit
  *

Question 10

• What is the blood-testis barrier and why is it important?
• What can damage this barrier?

Answer 10

• It is the barrier created by sertoli cells in the seminiferous tubules of the testis that controls the content of the tubule and prevents passage of cytotoxic agents into the tubule. It also prevents immune cells/cytokines from entering to prevent an autoimmune response to the testis. Serves as barrier protecting sperm.
• Trauma and vasectomy

Question 11

What is residual body?

Answer 11

Mature spermatozoa shed their cytoplasm as residual bodies

Question 12

What external factors are important for sperm development?

Answer 12

Temperature (2 deg C beow body temp)

Time (takes 74 days)

Question 13

Describe the importance of temperature on spermatogenesis, including:

• the temperature that must be maintained in the testis
• the mechansisms that help maintain that temp
• Causes of increased temp

Answer 13

Question 14

Answer 14

Question 15

Describe the general steps of spermiogenesis (note: not spermatogenesis).

Answer 15

Question 16

Where does the acrosome arise from?

Answer 16

Proacrosomal granules of hyaluronidases nad proteolytic enzymes in the golgi

Question 17

The sperm flagellum grows out from a […]

Answer 17

Centriole

Question 18

How is DNA packing in a sperm different than DNA packing in any other cell?

Answer 18

Sperm coil DNA around protamines, which makes the DNA form a toroid structure instead of solenoid structure. In this image, the DNA is wrapped around the protamine like a donut and then the protamines are stacked on top of one another. This increases the packing efficiency of the DNA superstructure (bottom image). There are histone solenoids interspersed thoughout for easier transcription.

Question 19

[…] mL of sperm per ejaculate

[…] sperm per mL

Answer 19

3.5

120 million

Question 20

What factors determine infertility in men?

Answer 20

Sperm count less than 20 million

Motility less than 50%

Question 21

After production in the seminiferous tubules, sperm travel next to the […]

Answer 21

Epididymis

Question 22

Epididymis

• Function of structure?
• How long does it take sperm to traverse this structure?
• Are sperm able to fertilize when in epididymis?
• How long do they remain viable once in epididymis?

Answer 22

• Store sperm
• Several days, structure is 6m long
• Sperm are non-motile and thus cannot fertilize. This is because they are under the influence of inhibiting proteins. They gain motility capabilities upon ejaculation.
• Viable for up to month

Question 23

What are the implications of pH on sperm function?

Answer 23

Question 24

Seminial Vesicles

• What are these?
• What do they produce?
• When / Where do they empty their contents?
• What is the function of their secretions?

Answer 24

• Tortuous tube lined with secretory epithelium, just prior to prostate gland
• Mucoid material rich in fructose, citric acid, nutrients, prostaglandins, fibrinogen
• Empty into vas deferens when the vas deferens contracts during ejaculation
• React with female cervical mucosa and make it more receptive to sperm and reverse peristaltic actions of uterus

Question 25

**Prostate gland** * What does this secrete? * When does this contract? * What is the pH?

Answer 25

Question 26

Describe the fluid composition of semen from: * Vas deferens * Seminal vesicle * Prostate gland * Mucus glands / bulbourethral glands

Answer 26

Question 27

Fluid from the [...] is the last to be ejaculated and it washes out the vas deferens / urethra.

Answer 27

Seminal vesicle

Question 28

Why is there clotting enzyme and fibrinogen in semen?

Answer 28

Clotting enzyme causes fibrinogen to form a coagulum in deeper regions of the vagina. This helps protect the sperm as it reaches deep into the female uterus. The coagulum is degraded in 15-30 minutes by fibrinolysin in the semen from the prostate gland and this releases highly motile sperm into the vagina/uterus.

Question 29

What is sperm half life in: * Epididymis * Post ejaculation * At low temp * At - 100 deg C

Answer 29

Question 30

What is sperm capacitation?

Answer 30

Sperm is mature but inactive when in epidiymis. It is activated by coming in contact with female vaginal secretions due to several factors (see image).

Question 31

Describe the process of fertilization.

Answer 31

* Acrosome binds to either: * ZP3 receptors on zona pellucida --\> Acrosome degranulates releasing hyaluronidase and protelytic enzymes that degrade the zona pellucida and granulosa cells to reach the egg * ZP2 receptors on zona pellucida --\> sperm head invades zona pellucida and then releases enzymes into ZP to degrade it and the granulosa cells to reach egg * Once sperm is able to pass through to egg, Ca++ enters (membrane made more permeable to Ca++ by vaginal environment) and causes sperm to initate PLC signaling cascade that results in changes to remaining zona pellucida that prevents additional sperm from binding * Membrane of sperm nucleus and egg nucleus occurs rapdily after penetration to nucleus (~ 30mins)

Question 32

What determines sex in humans?

Answer 32

**Genetics** (on Y chromosome) and *hormones* * **SRY gene** --\> produces TDF protein --\> expressed in sertoli cells * **SRY gene** products induce genital ridge cells to become leydig cells ---\> *testosterone* --\> male sex determination * **SRY gene** --\> sertoli cells --\> produce *antimullerian hormone* * **Eif2s3y gene** --\> helps spermatogonia develop into spermatids

Question 33

Leydig cells produce testosterone, which in the developing embryo stimulates maturation of the wolffian ducts. What structures arise from the wolffian duct?

Answer 33

Epidiymis Vas deferens Ejaculatory duct Seminal vesicle

Question 34

Where do the external male genetalia develop from? * Prostate * Penis * Scrotum

Answer 34

* Urethral epithelium (leydig cells --\> Testosterone --\> circulate --\> UE converts to DHT with 5alpha reductase --\> stimulate differentiation into prostate) * Primoridial cells (leydig cells --\> Testosterone --\> circulate --\> primordial genital ridge cells convert to DHT with 5alpha reductase --\> stimulate differentiation into penis and scrotum)

Question 35

The induction of differentiation from bipotential gonad to testes (or ovaries) occurs between weeks [...] and [...]

Answer 35

6 and 7

Question 36

Retention of wolffian ducts and regression of mullerian ducts (or opposite in females) occurs on week [...]

Answer 36

8

Question 37

External genetalia develop weeks [...] to [...]

Answer 37

9 to 12

Question 38

Answer 38

Question 39

**Testosterone** * Produced by... * Decreases after age ... * How does it circulate * How is it removed from body * Basics of receptor interaction and signaling cascade * What is the significance of androgen binding protein in the testes?

Answer 39

* Leydig cells (~95%) and adrenal gland (only ~5%) * 50 y/o * Bound to sex hormone binding globulin (Most), albumin (~38%), and 2-3% free * Eliminated by liver, excreted via bile and urine * Diffuse through membrane, bind to cytosolic androgen receptor, go to nucleus, dimerize, activate transcription * ABP allows for highly concentrated binding of testosterone in the seminiferous tubules so it can influence spermiogenesis

Question 40

True/False: GnRH is released constantly and induces constant release of FSH and LH.

Answer 40

False * GnRH is released in pulsatile manner for a few mins duration every 1-3 hours * LH is release is pulsatile, follows GnRH * FSH is constant, but follows GnRH long term

Question 41

What 2 male hormones feedback and inhibit the HPT axis?

Answer 41

Testosterone Inhibin

Question 42

Answer 42

Question 43

Describe the process of penile erection.

Answer 43

* PSNS --\> cavernous nerve --\> produce NO --\> (+) guanylyl cyclase --\> (+) cGMP --\> (+) relaxation --\> increase blood flow to cavernous artery and helicine arteries --\> increased blood entry into sinusoidal spaces --\> **erection** * Sexual stimulation --\> contraction of muscles around penis base --\> decreased venous return to cavernous spaces --\> increased blood in cavernous spaces --\> **erection** NOTE: Production of NO is cyclic. Increased relaxation produced by NO allows more NO to be produced.

Question 44

Describe process of penile emission and ejaculation.

Answer 44

Question 45

What is male circumcision?

Answer 45

Removal of the foreskin/prepuce from the penis

Question 46

What are the current recomendations regarding circumcision?

Answer 46

Health benefits of newborn male circumcision outweigh the risks, but the benefits are not so much greater than the risks that it warrants recommendation of universal newborn circumcision, so the decision is left to the parents.

Question 47

What is one reason why circumcision rates are so much higher in all of Africa?

Answer 47

Prevalence of HIV and fact that circumcision reduces likelihood of contracting HIV from infected female partner

Question 48

What are the benefits of circumcision for males and any female partners they may have?

Answer 48

Question 49

Why is it not recommended to wait to circumcise until the child is old enough to decide for themselves?

Answer 49

Question 50

What is the difference bewteen puberty and adolescence?

Answer 50

Question 51

What is minipuberty?

Answer 51

Important for maturation of male sex organs and descent of testes into scrotum

Question 52

What is hypospadias?

Answer 52

Question 53

Prenatal peak of T and minipuberty are necessary for what?

Answer 53

Decent of testicles into scrotum

Question 54

After minipuberty within the 1st year of life, GnRH neurons are essentially quiescent until puberty. What is regulating these neurons so that this is the case?

Answer 54

KNDy Neurons which secrete dynorphin and kisspeptins regulate GnRH neuron function. Dynorphin is inhibitor and is released until puberty and kisspeptins are stimulatory. During puberty, these neurons heavily stimulate GnRH neurons resulting in GnRH secretion profile throughout remainder of life of individual.

Question 55

What factors inhibit KNDy neurons? What factors stimulate them?

Answer 55

Inhibit * Stress * Inflammation * Sex-steroids * Drugs * Metabolism Stimulate --\> Nerurokinin B

Question 56

What factors inhibit and stimulate GnRH neurons?

Answer 56

Inhibit * Dynorphin from KNDy neurons * GnIH Stimulate * Kisspeptins from KNDy neurons * Neurokinin B from KNDy neurons

Question 57

What is the role of leptin in puberty?

Answer 57

Question 58

What does testosterone do?

Answer 58

Question 59

What does testosterone NOT do?

Answer 59

Question 60

What is the normal sequence of development in males?

Answer 60

Question 61

True/false: normal puberty can start at a range of ages but follows the same sequence.

Answer 61

True

Question 62

Review this slide on the tanner stages. Not for memorization, just appreciation / general understanding of trends. (Flip card)

Answer 62

Question 63

**Male Growth Spurts** * Generally occurs at age [...] * Does it occur ahead of or behind females? * Avg. height gained during puberty * When does it stop and why? * Why males tend to be taller than females?

Answer 63

* 13.5 * Behind females by 18 - 24 months * 10.3 cm * Stops ~ 15.8 y/o due to closure of epiphyseal plates from estradiol influence * Males taller b/c have typical childhood rates of growth prior to puberty, so their "base" height prior to puberty is greater than females

Question 64

Pubertal weight gain accounts for [...] of ideal adult body weight

Answer 64

50%

Question 65

When does weight gain happen in males and females?

Answer 65

Males - coincides w/ puberty Females - lags 6-9 months behind

Question 66

* What is the mean age for males entering stage 2 of puberty? * Range for males entering stage 2? * When do males typically complete puberty? What is the range?

Answer 66

* 10 y/o * 9 - 14 * 3 years after onset, can be as much as 2 - 5 years

Question 67

True/False: Boys and girls who develop earlier will be shorter than those who are late because of baseline growth prior to onset of growth spurt.

Answer 67

True

Question 68

True/False: Early maturing boys are more likely to have substance abuse and/or tobacco issues.

Answer 68

False - late maturing boys are more likely for these things

Question 69

What are some of the perils of puberty?

Answer 69