Chapter 28 The Reproductive System PDF

Chapter 28 The Reproductive System Edited by N. Marlo Ballard An Introduction to the Reproductive System  Reproductive system o Is the only body system that is not essential to the life of the individua...

Chapter 28 The Reproductive System Edited by N. Marlo Ballard An Introduction to the Reproductive System  Reproductive system o Is the only body system that is not essential to the life of the individual o Male and female reproductive organs produce and store specialized reproductive cells that combine to form new individuals 28-1 Structures of the Reproductive System  Reproductive structures o Gonads—organs that produce gametes (reproductive cells) and hormones o Reproductive tract—includes all chambers, passageways, and ducts connecting the gonads to the exterior of body o Accessory glands—secrete fluids into ducts o External genitalia—perineal structures  Male and female reproductive systems are structurally and functionally different 28-2 Male Reproductive Structures  The Testes o Testes are the male gonads  Composed of tightly coiled seminiferous tubules  Nearly one-half mile in each testis  Location of male gamete (sperm) production (half a billion sperm per day)  Interstitial endocrine cells (Leydig cells) fill the spaces between the seminiferous tubules  Produce androgens (primarily testosterone)  The Epididymis o Start of male reproductive tract; coiled tube almost 7 m long o Three regions: 1. Head - Receives sperm from the testis 2. Body - middle section 3. Tail - Primary location of sperm storage; delivers sperm to the ductus deferens o Functions of epididymis 1. Monitor & adjust composition of fluid produced by seminiferous tubules  Via stereocilia of pseudostratified ciliated columnar epithelium 2. Recycle damaged sperm 3. Store and protect sperm and facilitate their functional maturation © 2018 Pearson Education, Inc. 1  The Scrotum o Fleshy pouch that encloses and suspends the testes and epididymis outside of the abdominopelvic cavity  For viable sperm production, testis must be 2 oF lower than body temp. Regulation is accomplished by muscles of the scrotum: 1. Dartos muscle  Layer of smooth muscle in dermis of scrotum  Causes characteristic wrinkling of the scrotal surface 2. Cremaster muscle  Layer of skeletal muscle deep to dermis  Contracts/relaxes to adjust proximity of testes to the body  The Spermatic Cords o Paired structures that extend between the abdominopelvic cavity and testes  Enclose the ductus deferens, blood vessels, nerves, and lymphatic vessels of testes o Begin at a passageway through the abdominal musculature called the inguinal canal  During fetal development, testes form within the abdominopelvic cavity, and around the 7th month they descend through the inguinal canal and into the scrotum  Leaves a weak spot that can cause inguinal hernias  Protrusions of visceral tissues into the inguinal canal  Cryptorchidism – condition in which one or both testes fail to descend and remain within the abdominopelvic cavity  Ductus deferens (vas deferens) o 40–45 cm long duct that begins at the tail of the epididymis, passes through the interior of the spermatic cord, and ascends through the inguinal canal into the abdominopelvic cavity  Sperm move through the ductus deferens through peristaltic contractions o In the abdominopelvic cavity the ductus deferens curves inferiorly along urinary bladder, where the lumen enlarges into the ampulla of ductus deferens - Can store sperm for several months  Male urethra o Used by both the urinary and reproductive systems o Extends 18–20 cm from urinary bladder to tip of penis o Divided into three regions 1. Prostatic – runs through the prostate gland 2. Membranous – between the prostatic and spongy sections, 3. Spongy – runs through the penis © 2018 Pearson Education, Inc. 2  Accessory glands o Produce seminal fluid, the fluid component of semen  Mixture of secretions with distinctive biochemical characteristics and functions that serve to activate the sperm 1. Seminal glands (seminal vesicles) o Produce the majority (about 60%) of seminal fluid volume  Secretions are discharged into the ejaculatory duct - Short passageway (2 cm) that empties into prostatic urethra  Thick, yellowish secretion that nourish and activates the sperm a. Slightly alkaline to neutralize the acidity of prostatic fluid & the vagina b. Contains fructose to nourish sperm c. Contains prostaglandins to stimulate smooth muscle contractions along male and female reproductive tracts d. Contains fibrinogen to create a temporary “semen clot” 2. Prostate gland o Small, muscular organ (about 4 cm in diameter) that encircles the prostatic urethra below the urinary bladder o Prostatic fluid (about 30% of semen volume) a. Slightly acidic fluid ejected into prostatic urethra b. Contains enzymes that prevent sperm coagulation in the vagina o Older males suffer from a variety of prostatic conditions, including: prostatitis, benign prostatic hyperplasia, and prostate cancer 3. Bulbo-urethral glands (Cowper’s glands) o Located at root/base of penis o Secrete thick, alkaline mucus (