Mosby items and derived items © 2007, 2003 by Mosby, Inc. 1 Chapter 31 Male Reproductive System

2 Introduction Ensures the survival of the species functions are to produce, transfer, and introduce mature sperm into the female reproductive tract where fertilization can occur

3 Male Reproductive Organs Essential organs = production of gametes  Gonads of the male = testes Accessory organs that support the reproductive process Accessory organs of reproduction Genital ducts convey sperm to outside of body paired epididymis, paired vas deferens, pair of ejaculatory ducts, and the urethra Accessory glands produce secretions that nourish, transport, and mature sperm pair of seminal vesicles, the prostate, and pair of bulbourethral glands Supporting structures— scrotum, penis, and pair of spermatic cords

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5 Perineum  Males: roughly diamond-shaped area between thighs  extends anteriorly from symphysis pubis to coccyx posteriorly  lateral boundary is the ischial tuberosity on either side  divided into the urogenital triangle and the anal triangle

6 Testes Structure and location  Located in scrotum  10-15g each  Left generally 1 cm lower than right in scrotal sac  Several lobules composed of seminiferous tubules and interstitial cells (of Leydig), separated by septa  Seminiferous tubules in testis  rete testis  epididymis  vas deferens  If unraveled, seminiferous tubules would be 75 cm long!

7 Testes > 5 layers in seminiferous tubule Sertoli cells-  cells that provide support and protection for developing germ cells  Play a role in release of mature spermatozoa into lumen of tubule

8  Spermatogenesis — formation of mature male gametes (spermatozoa) by seminiferous tubules

9 Testes Functions  Spermatogenesis— formation of mature male gametes (spermatozoa) by seminiferous tubules  hill.com/olc/dl/120112/anim0043.swf hill.com/olc/dl/120112/anim0043.swf  Secretion of hormone Testosterone: Promotes male secondary sex characteristics Promotes anabolism of proteins (muscular and bone development) Inhibits female hormones (FSH and LH)

10 Testes Structure of spermatozoa  consists of head (covered by acrosome) Acrosome contains hydrolytic enzymes Neck Midpiece Tail

11 Reproductive (Genital) Ducts Epididymis  Structure and location Single tightly coiled tube Lies along top and side of each testis About 20 feet long!  Functions Duct for seminal fluid secretes part of seminal fluid Sperm become capable of motility while they are passing through epididymis

12 Reproductive (Genital) Ducts Vas deferens (ductus deferens)  Structure and location Tube; extension of epididymis Extends through inguinal canal, into abdominal cavity, and over top and down posterior surface of bladder Enlarges and joins duct of seminal vesicle  Function One of excretory ducts for seminal fluid Connects epididymis with ejaculatory duct

13 Reproductive (Genital) Ducts Ejaculatory duct  Formed by union of vas deferens with duct from seminal vesicle  Passes through prostate gland, terminating in urethra Urethra

14 Accessory Reproductive Glands Seminal vesicles  Structure and location convoluted pouches about 5 to 7 cm long on posterior surface of bladder  Function secrete the viscous, nutrient- rich part of seminal fluid 60% of semen volume

15 Accessory Reproductive Glands Prostate gland  Structure and location Doughnut-shaped Encircles urethra just below bladder  Function adds slightly alkaline, watery, milky-looking secretion to seminal fluid 30% of semen volume Alkalinity neutralizes the acidity of the urethra and the vagina

16 Accessory Reproductive Glands Bulbourethral gland  Structure and location Small, pea-shaped structures with ducts about 2.5 cm (1 in) long 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  Divided into two compartments  Contains testis, epididymis, and lower part of a spermatic cord  muscles elevate the scrotal pouch when it is cold and lower it when it is hot lymphangioma

18 Supporting Structures Penis  Structure composed of three cylindrical masses of erectile tissue, one of which contains the 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

19 Supporting Structures Spermatic cords (internal)  Consists of vas deferens, blood vessels, lymphatics, and nerves  Passes through inguinal canal

20 Composition and Course of Seminal Fluid Consists of secretions from testes, epididymides, seminal vesicles, prostate, and bulbourethral glands Each mL contains millions of sperm From testes  epididymis  vas deferens  ejaculatory duct  urethra

21 TYPICAL REFERENCE INTERVALS COMPONENTCONVENTIONAL UNITS LiquefactionWithin 20 min Sperm Morphology >70% normal, mature spermatozoa Sperm Motility>60% pH>7.0 (average 7.7) Sperm Count X 10 6 /mL Volume mL

22 Male Fertility Relates to many factors  number of sperm  size, shape, and motility Infertility may be caused by antibodies some men make against their own sperm- “immune infertility” <25 million sperm/mL of semen = functional sterility  Possible Hypothesis: Semen with enough sperm contains hydrolytic enzymes to breakdown the cells around the ovum Without this, a single sperm cannot penetrate these layers

23 Cycle of Life: Male Reproductive System 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