1. Chapter 31: Male Reproductive System
Dr. Kim Wilson

2. SEXUAL REPRODUCTION
Functioning of the reproductive system ensures the survival of the genetic characteristics of a species
Male reproductive system consists of organs whose functions are to produce, transfer, and introduce mature sperm into the female reproductive tract, where fertilization can occur

3. MALE REPRODUCTIVE ORGANS
Classified as essential organs for production of gametes or accessory organs that support the reproductive process
Accessory glands produce secretions that nourish, transport, and mature sperm
Essential organs: gonads (testes)
Accessory organs:
Genital ducts convey sperm outside the body
pair of epididymides,
paired vasa deferentia
pair of ejaculatory ducts
urethra
pair of seminal vesicles
the prostate
bulbourethral glands
Supporting structures: scrotum, penis, and pair of spermatic cords
MALE REPRODUCTIVE ORGANS

4. Perineum Structure: roughly diamond-shaped area between thighs
Location: extends anteriorly from pubic symphysis to coccyx posteriorly
Lateral boundary is the ischial tuberosity on either side
Divided into the urogenital triangle and the anal triangle

5. TESTES Structure and location
Several lobules composed of seminiferous tubules and interstitial cells (Leydig cells), separated by septa and encased in fibrous capsule called the tunica albuginea (Figure 31-3)
Seminiferous tubules in testis open into a plexus called rete testis, which is drained by a series of efferent ductules that emerge from the top of the organ and enter the head of epididymis
Located in scrotum, one testis in each of two scrotal compartments

6. Microscopic Anatomy of the Testes
Interstitial (Leydig) cells: endocrine cells between the seminiferous tubules
Seminiferous tubules
Spermatogenic cells produce sperm
Sustentacular cells: also called nurse or Sertoli cells
Support and regulate sperm-producing functions of the testis
Produce androgen-binding protein that binds to testosterone to make it more soluble and thus increase its concentration, supporting sperm production
Tight junctions between sustentacular cells form the blood-testis barrier, which protects developing sperm from the immune system

8. Functions of the Testes
Spermatogenesis: formation of mature male gametes (spermatozoa) by seminiferous tubules
Stimulated by follicle-stimulating hormone from the anterior pituitary (and also gonadotropin-releasing hormone from hypothalamus)
Secretion of hormones by interstitial cells
Testosterone
Type of androgen: maleness hormone
Functions include promoting primary and secondary male sexual characteristics and anabolism, affecting fluid and electrolyte balance
Regulated by luteinizing hormone from anterior pituitary
Inhibin: inhibits release of follicle-stimulating hormone by anterior pituitary, allowing the testis some control over spermatogenesis
Estrogen: small amounts secreted by interstitial cells, liver, and other organs; role in males uncertain but may influence spermatogenesis and other functions

9. Testosterone Secretion

10. Spermatozoa
Structure: consists of a head (covered by acrosome), neck, midpiece, and tail; tail is divided into a principal piece and a short end piece

11. Reproductive Ducts - Epididymis
Structure and location
Single tightly coiled tube enclosed in fibrous casing
Lies along top and side of each testis
Anatomical divisions include head, body, and tail
Functions
Duct for seminal fluid
Also secretes part of seminal fluid
Sperm become capable of motility while they are passing through the epididymis

12. Reproductive Ducts – Vas Deferens
Vas deferens (ductus deferens)
Structure and location
Tube, extension of epididymis
Extends through inguinal canal, into abdominal cavity, over top and down posterior surface of bladder
Enlarged terminal portion called ampulla; joins duct of seminal vesicle
Function
Excretory duct for seminal fluid
Connects epididymis with ejaculatory duct

14. Reproductive Ducts – Ejaculatory Duct & Urethra
Formed by union of vas deferens with duct from seminal vesicle
Passes through prostate gland, terminating in urethra
Urethra

15. Accessory Reproductive Glands
Seminal vesicles
Structure and location: convoluted pouches 5 to 7 cm long on posterior surface of bladder
Function: secrete the viscous, nutrient-rich part of seminal fluid (60% of semen volume)
Prostate gland
Structure and location
Doughnut shaped
Encircles urethra just below bladder
Function: adds slightly acidic, watery, milky-looking secretion to seminal fluid (30% of semen volume)

16. Accessory Reproductive Glands
Bulbourethral glands
Structure and location:
Small, pea-shaped structures with approximately 2.5-cm long (1 inch) ducts leading into urethra
Lie below prostate gland
Function: secrete alkaline fluid that is part of semen (5% of semen volume)

17. Supporting Structures - Scrotum
Skin-covered pouch suspended from perineal region into which the testes descend near the time of birth
Divided into two compartments:
Contains testis, epididymis, and lower part of a spermatic cord
Dartos and cremaster muscles elevate the scrotal pouch

18. Supporting Structures - Penis
Structure: composed of three cylindrical masses of erectile tissue, one of which contains urethra
Functions: penis contains the urethra, the terminal duct for both urinary and reproductive tracts; during sexual arousal, penis becomes erect, serving as a penetrating copulatory organ during sexual intercourse
Spermatic cords (internal)
Fibrous cylinders located in inguinal canals
Enclose seminal ducts, blood vessels, lymphatics, and nerves

19. Seminal Fluid Composition: Flow:
Consists of secretions from testes, epididymides, seminal vesicles, prostate, and bulbourethral glands
Each milliliter contains millions of sperm
Flow:
Passes from testes through epididymis, vas deferens, ejaculatory duct, and urethra

20. Male Fertility
Relates to many factors: number, size, shape, and motility of sperm
Infertility may be caused by antibodies some men make against their own sperm
Male fertility begins at puberty and extends into old age

21. Reproduction Cycle Reproductive functions begin at time of puberty
Development of organs begins before birth; immature testes descend into scrotum before or shortly after birth
Puberty: high levels of hormones stimulate final stages of development
System operates to permit reproduction until advanced old age
Late adulthood: gradual decline in hormone production may decrease sexual appetite and fertility