1. The Reproductive System
Chapter 27
The Reproductive System

2. Primary sex organs (gonads)
Reproductive System
Primary sex organs (gonads)
Testes in males
Ovaries in females
Gonads produce:
Sex cells called gametes
Secrete sex hormones
Accessory reproductive organs:
Ducts
Glands
External genitalia

3. Reproductive System Sex hormones: They play roles in:
Androgens (males)
Estrogens & progesterone (females)
They play roles in:
Development of the reproductive organs
Function of the reproductive organs
Sexual behavior and drives
Growth and development of many other organs and tissues

4. Male Reproductive System
The male gonads (testes):
Lie within the scrotum
Produce sperm
Sperm:
Delivered through a duct system consisting of:
Epididymis
Ductus deferens
Ejaculatory duct
Urethra

5. Male Reproductive System
Accessory sex glands:
Empty their secretions into the ducts during ejaculation
Include :
Seminal vesicles
Prostate gland
Bulbourethral glands

6. Male Reproductive System
Figure 27.1

7. Sac of skin and superficial fascia
The Scrotum
Sac of skin and superficial fascia
Hangs outside the abdominopelvic cavity
Contains testicles separated by a midline septum
Its external positioning keeps the testes:
3C lower than core body temperature:
Needed for sperm production

8. Intrascrotal temperature is kept constant by two sets of muscles:
The Scrotum
Intrascrotal temperature is kept constant by two sets of muscles:
Dartos muscle:
Smooth muscle
Wrinkles scrotal skin (cold)
Cremaster muscle:
Bands of skeletal muscle
Elevate the testes (cold)

9. The Scrotum S7
Figure 27.2

10. Each testis is surrounded by two tunics:
The Testes
Each testis is surrounded by two tunics:
The tunica vaginalis (serous), derived from the peritoneum
The tunica albuginea, the fibrous capsule of the testis
Septa divide the testis into lobules
Each lobule contains 1-4 seminiferous tubules

11. The Testes Seminiferous tubules: Tubulus rectus:
Where sperm are produced
Converge to form the tubulus rectus
Interstitial (Leydig) cells surround seminiferous tubules
These cells produce androgens
Tubulus rectus:
Straight tubules that convey sperm to the rete testis
From the rete testis, the sperm:
Leave the testis via efferent ductules
Enter the epididymis

12. The Testes
Figure 27.3a

13. The Testes Testicular arteries: Testicular veins: Spermatic cord:
abdominal aorta branch
supply the testes
Testicular veins:
arise from the pampiniform plexus
Spermatic cord:
A connective tissue sheath
Encloses: Nerve fibers, blood vessels, and lymphatics that supply the testes

14. The Penis A copulatory organ designed to: Consists of:
Deliver sperm into the female reproductive tract
Consists of:
An attached root
A free shaft
The glans penis
Prepuce, or foreskin:
Cuff of skin covering the distal end of the penis
Circumcision:
Surgical removal of the foreskin after birth

15. Internally the penis contains:
The spongy urethra
Three cylindrical bodies (corpora) of erectile tissue
Erectile tissue is made of:
Spongy network of connective tissue
Smooth muscle riddled with vascular spaces

16. The Penis Erection: Corpus spongiosum: Occurs during sexual excitement
The erectile tissue fills with blood causing the penis to:
Enlarge
Become rigid
Corpus spongiosum:
The midventral erectile body
Surrounds the urethra
Expands to form:
Proximally, the bulb of the penis
Distally, the glans penis

17. The Penis Corpora cavernosa: Crura: The paired dorsal erectile bodies
Bound by fibrous tunica albuginea
Crura:
Proximal penile end
Surrounded by the ischiocavernosus muscle
Anchors the penis to the pubic arch

18. The Penis
Figure 27.4

19. Epididymis Has three regions: Head: Head Body Tail
Joins the efferent ductules
Caps the superior aspect of the testis
Entering nonmotile sperm, become motile while passing through its tubes
Expels sperm into ductus deferens when contract during ejaculation

20. Ductus Deferens and Ejaculatory Duct
Runs from the epididymis through the inguinal canal into the pelvic cavity
Its terminus expands to form the ampulla
Joins the duct of the seminal vesicle to form the ejaculatory duct
Propels the sperm to the urethra
Vasectomy:
Cutting & ligation of the ductus deferens
Nearly 100% effective means of male birth control
Success rate of reversing the procedure is 50%

21. Conveys both urine and semen in males Consists of three regions
Urethra
Conveys both urine and semen in males
Consists of three regions
Prostatic urethra:
Portion surrounded by the prostate
Membranous urethra:
Lies in the urogenital diaphragm
Spongy, or penile urethra:
Runs through the penis
Opens to the outside at the external urethral orifice

22. Accessory Glands: Seminal Vesicles
Paired glands
Lie on the posterior wall of the bladder
Produces and stores secretion that is:
Yellowish viscous fluid
Contains:
Ructose
A coagulating enzyme “vesiculase”
Ascorbic acid
Prostaglandins & other substances

23. Accessory Glands: Seminal Vesicles (cont’d)
Secrete 70% of the volume of semen:
Ducts join ductus deferens forming ejaculatory ducts
Sperm & seminal fluid mix in the ejaculatory duct
Semen enter the prostatic urethra during ejaculation

24. Accessory Glands: Prostate Gland
Doughnut-shaped single gland
Encircles the urethra just inferior to the bladder
Produces milky, slightly acid fluid that:
Contains citrate, enzymes, prostate-specific antigen (PSA)
Accounts for one-third of the semen volume
Plays a role in the activation of sperm
Enters the prostatic urethra via several ducts during ejaculation

25. Accessory Glands: Bulbourethral Glands (Cowper’s Glands)
Pea-sized paired glands
Inferior to the prostate
Produce (prior to ejaculation):
Thick, clear mucus
Secreted mucus:
Neutralizes traces of acidic urine in the urethra

26. Semen Milky, viscous, sticky, white, alkaline fluid
A mixture of sperm and accessory gland secretions
Contains fructose, ascorbic acid, coagulating enzyme (vesiculase), and prostaglandins
Provides a transport medium and nutrients (fructose)
Protects and activates sperm, and facilitates their movement
Prostaglandins in semen:
Facilitate sperm movement through the female reproductive tract by:
Decreasing the viscosity of mucus in the cervix
Stimulating reverse peristalsis in the uterus

27. Male Sexual Response: Erection
Enlargement & stiffening of the penis
Results from engorgement of erectile tissue with blood
A parasympathetic reflex promotes the release of nitric oxide (NO) during sexual arousal
NO causes erectile tissue to fill with blood (vasodilatation)
Blood-expanded corpora cavernosa compress their drainage veins retarding blood outflow
Retarded blood maintains engorgement
The corpus spongiosum keeps the urethra open during ejaculation
Impotence:
Inability to attain erection

28. Ejaculation Is the propulsion of semen from the male duct system
At ejaculation, sympathetic nerves serving the genital organs cause:
Reproductive ducts and accessory organs to contract and empty their contents
The bladder sphincter muscle to constrict, preventing the expulsion of urine
Bulbospongiosus muscles to undergo a rapid series of contractions
Propulsion of semen from the urethra

29. Human Life Cycle
Figure 27.5

30. Spermatogenesis
The sequence of events that produces sperm in the seminiferous tubules of the testes
Each cell has two sets of chromosomes (a maternal & a paternal)
Such cell is said to be diploid (2n chromosomal number)
Humans somatic cells have 23 pairs of homologous chromosomes
Gametes “ reproductive cells” only have 23 chromosomes and are said to be haploid (n chromosomal number)
Gamete formation is by meiosis
During meiosis the number of chromosomes is halved (2n to n)

31. Mitosis of Spermatogonia
Spermatogenesis:
Begins at puberty
Spermatogonia (stem cells):
Are the outermost cells
In contact with the epithelial basal lamina
Each mitotic division results in:
Type A and type B daughter cells

32. Mitosis of Spermatogonia
Type A cells:
Remain at the basement membrane
Maintain the germ line
Type B cells:
Move toward the lumen
Become primary spermatocytes

33. Spermatocytes to Spermatids
Primary spermatocytes:
Undergo meiosis I, forming two haploid cells called:
Secondary spermatocytes
Secondary spermatocytes:
Undergo meiosis II forming daughter cells called:
Spermatids
Spermatids are:
Haploid
Nonmotile
Small round cells with spherical nuclei
Seen close to the lumen of the tubule

34. Figure 27.8b, c

35. Semen Contains the following substances:
The hormone relaxin which enhances sperm motility
The antibiotic seminalplasmin which destroys certain bacteria
Clotting factors that coagulate semen immediately after ejaculation (stick to vaginal wall & not being drained out)
Fibrinolysin that liquefies the sticky mass (resume movement)
Semen alkalinity neutralizes the acid environment in the male urethra and female vagina
Ejaculated amount of semen is only 2-5 ml, but contains million sperm/ml