1. Unit V: Development Male Reproductive System
Chapter 25:

2. Male Reproductive System

3. Scrotum Pouch holding testes
divided into 2 compartments by median septum
Sperm not produced at core body temperature
cremaster muscle
dartos muscle
pampiniform plexus
countercurrent heat exchanger

4. Testes Oval organ, 4 cm long x 2.5 cm in diameter Seminiferous tubules
thick germinal epithelium
Sustentacular cells/nurse cells
promote germ cell development
secrete inhibin
Interstitial cells
Scrotum
Cremaster muscle
Skin
Dartos muscle
Superficial fascia
Scrotal cavity
Epididymis
Efferent ductule
Ductus deferens
Seminiferous tubule
Septa
Rete testis

5. Testes 3% born with undescended testes (cryptorchidism)
2 months
3 months
Birth
Developing testis
Connective tissue band
5 mm
The connective tissue bands do not get longer as the fetus
grows.
Late in fetal development,
hormones cause the connective
tissue band to contract.
Testis
Scrotum
Testes
3% born with undescended testes (cryptorchidism)
Location outside pelvic cavity essential for low temperatures needed for sperm production
Blood-testis barrier
Formed by tight junctions between sustentacular cells -- separating sperm from immune system

6. Spermatic Ducts Efferent ductules 12 small ciliated ducts Epididymis
Reabsorbs 90% of testicular fluid
site of sperm maturation and storage (fertile for 60 days)
Vas (ductus) deferens
muscular tube 45 cm long
sympathetic nerve fibers
peristalsis during orgasm
Ejaculatory duct
2 cm duct empties into urethra

7. Male Duct System

8. Seminal vesicles/glands
Accessory Glands
LM  35
Seminal gland
Lumen
Secretory pockets
Smooth muscle
Seminal vesicles/glands
pair of glands
empty into ejaculatory duct
Prostate gland
aggregate of glands
empty into urethra
Bulbourethral glands
near bulb of penis; empty into spongy urethra
lubricating fluid
neutralizes acid of urine
LM  35
Prostate gland
Connective tissue and smooth muscle
Prostatic glands
Smooth muscle
Capsule
Mucous glands
Bulbo-urethral gland
Lumen
LM  140

9. Penis Internal root; external shaft and glans
skin over shaft loosely attached allows expansion
extends over glans as prepuce (foreskin)
3 cylindrical bodies of erectile tissue
Fill with blood during sexual arousal
Membranous urethra
Bulb of penis
Right crus of penis
Corpus spongiosum
Corpora cavernosa
Scrotum
Pubic symphysis
Root of penis
Body (shaft) of penis
Neck
Glans of penis
External urethral
orifice

10. Penis 3 cylindrical bodies of erectile tissue corpus spongiosum
encloses spongy urethra
bulbospongiosus muscle
corpus cavernosa (2)
diverge like arms of a Y
ischiocavernosus muscle

11. Spermatogenesis Spermatogonia (diploid)2 3 4 5 1 n
Secondary spermatocyte
Sustentacular cell
Spermatid
Spermiogenesis
Meiosis II
Meiosis I
Sperm
Blood–testis barrier
Lumen of
seminiferous tubule
Primary
spermatocyte
Type B spermatogonium
Tight junction
Type A spermatogonium
Basement membrane
of seminiferous tubule 2n
Spermatogonia (diploid)
1. type A - produce more daughter cells until death
2. type B differentiate into primary spermatocytes
cells must pass through BTB
3. meiosis I  2 secondary spermatocytes
4. meiosis II  4 spermatids

12. Spermiogenesis Changes that transform spermatids into spermatozoa
400 million per day

13. Spermatozoon
Head
containing the nucleus, acrosome and basal body of the tail flagella
Tail (flagellum)
midpiece contains mitochondria

14. Semen / Seminal Fluid 2-5 mL of fluid expelled during orgasm
60% seminal vesicle fluid, 30% prostatic, 10% sperm
normal sperm count million/mL
Other components of semen:
fibrinogen - causes clotting  seminogelin
prostatic fluid - is a base stabilizing sperm pH at 7.2 to 7.6
prostaglandins - stimulate female peristaltic contractions
For capacitation:
serine protease - liquefies semen within minutes
fructose - energy for sperm motility

15. Excitement
Erection of penis is due to parasympathetic triggering of nitric oxide (NO) secretion
dilation of deep arteries and filling of lacunae with blood

16. Orgasm
Orgasm (climax) is 15 second reaction that includes the discharge of semen (ejaculation)
Ejaculation
emission = peristaltic contractions propel sperm through ducts as glandular secretions are added
expulsion = semen in urethra activates muscular contractions that lead to expulsion

17. Resolution Sympathetic signals reduce blood flow to penis
penis becomes soft and flaccid
Cardiovascular and respiratory responses return to normal
Refractory period (10 minutes to few hours)