Repro - Physiology (Spermatogenesis & Androgens)

Question 1

When does spermatogenesis begin, and with what kind of cell?

Answer 1

Spermatogenesis begins at puberty with spermatogonia

Question 2

How long does full development of sperm take? Where does this occur?

Answer 2

Full development takes 2 months. Occurs in seminiferous tubules.

Question 3

What is produced in the process of spermatogenesis? What occurs after that?

Answer 3

Produces spermatids that undergo spermiogenesis (loss of cytoplasmic contents, gain of acrosomal cap) to form mature spermatozoon; Think: “Gonium is Going to be a sperm, Zoon is Zooming to egg.”

Question 4

Draw the processes of spermatogenesis and spermiogenesis, labeling the following: (1) Replication (interphase) (2) Meiosis I (3) Meiosis II (4) Spermatogonium Diploid (2N, 2C) (5) Secondary spermatocyte Haploid (1N, 2C) (6) Spermatid Haploid (1N, 1C) (7) Spermiogenesis (8) Primary spermatocyte Diploid (2N, 4C) (9) Mature spermatazoon Haploid (N) (10) 46 single chromosomes (sex=X-Y) (11) 46 sister chromatids (sex = X-X, Y-Y) (12) 23 sister chromatids (sex=X-X) (13) 23 sister chromatids (sex=Y-Y) (13) Sperm (14) 23 single (sex=X) (two of these) (15) 23 single (sex=Y) (two of these) (16) Blood-testis barrier/Tight junction

Answer 4

See p. 572 in First Aid 2014 or p. 518 in First Aid 2013 for visual starting at left

Question 5

Draw a spermatozoon, labeling the following: (1) Head (2) Neck (3) Middle piece (4) Nucleus (5) Tail (6) Acrosome.

Answer 5

See p. 572 in First Aid 2014 or p. 518 in First Aid 2013 for visual on right

Question 6

What can result from impaired tail mobility in mature spermatozoon? In what condition(s) is this seen?

Answer 6

Impaired tail mobility can lead to infertility (seen in ciliary dyskinesia/Kartagener syndrome)

Question 7

What are the forms of androgens? What is the source of each?

Answer 7

Testosterone (testis), dihydrotestosterone (DHT) (testis), androstenedione (adrenal); Think: “AnDrostenedione = ADrenal”

Question 8

List the forms of androgen in order of decreasing potency.

Answer 8

Potency: DHT > testosterone > androstenedione

Question 9

What 5 functions does testosterone serve?

Answer 9

(1) Differentiation of epididymis, vas deferens, seminal vesicles (internal genitalia, except prostate) (2) Growth spurt - penis, seminal vesicles, sperm, muscle, RBCs (3) Deepening of voice (4) Closing of epiphyseal plates (via estrogen converted from testosterone) (5) Libido

Question 10

What functions does testosterone serve in terms of growth and differentiation?

Answer 10

Differentiation of epididymis, vas deferens, seminal vesicles (internal genitalia except prostate); Growth spurt - penis, seminal vesicles, sperm, muscle, RBCs

Question 11

What causes the closing of epiphyseal plates?

Answer 11

Closing of epiphyseal plates (via estrogen converted from testosterone)

Question 12

What are early and late effects of DHT?

Answer 12

Early - differentiation of penis, scrotum, prostate; Late - prostate growth, balding, sebaceous gland activity

Question 13

Which enzyme converts testosterone to DHT? What inhibits this enzyme?

Answer 13

Testosterone is converted to DHT by the enzyme 5alpha-reductase, which is inhibited by finasteride

Question 14

In the male, what converts androgens to estrogen, and where?

Answer 14

In the male, androgens are converted to estrogen by cytochrome P-450 aromatase (primary in adipose tissue and the testis)

Question 15

What is the key enzyme in the conversion of androgens to estrogen?

Answer 15

Aromatase

Question 16

What main effect does exogenous testosterone have, and via what mechanisms does this occur?

Answer 16

Exogenous testosterone –> inhibition of hypothalamic-pituitary-gonadal axis –> decrease in intratesticular testosterone –> decreased testicular size –> azoospermia

Question 17

What is the N (ploidy) and C (# of chromosomes) for each of the following cell stages in spermatogenesis and spermiogenesis: (1) Spermatogonium (2) Primary spermatocyte (3) Secondary spermatocyte (4) Spermatid (5) Mature spermatozoan?

Answer 17

(1) Diploid (2N, 2C) (2) Diploid (2N, 4C) (3) Haploid (1N, 2C) (4) Haploid (1N, 1C) (5) Haploid (1N, 1C)