Chapter 16 The Reproductive System Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 16 The Reproductive System Slides 16.1 – 16.20 Lecture Slides in PowerPoint by Jerry L. Cook Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Functions: 1. Produce Gametes 2. Transport Gametes 3. Maintain Gametes 4. Maintain developing Zygote / Fetus (female) 5. Produce Sex hormones: Male = testosterone Female = estrogen and progesterone

MALE REPRODUCTIVE SYSTEM INTERESTING FACTS  Male sperm are significantly smaller than the female egg.  While the sperm measures 2.5 to 3.5 microns across the head the fully mature egg is 100-125 microns in diameter. About 500 million sperm mature every day in a healthy male. The male scrotum hangs outside the body since the internal body temperature is too high and will kill the sperm. Once the sperm has penetrated the egg the outer shell becomes impenetrable to other sperm Unlike the ovaries which never produce new eggs after a female child is born, the male testes (once sperm production begins in puberty), can produce about 1,000 sperm per second, or about 30 billion per year. From the standpoint of the mathematics alone, 10-20 ejaculations of semen hold enough sperm to populate the earth!

MALE REPRODUCTIVE SYSTEM INTERESTING FACTS Sperm cells contain receptors on the surface of the sperm head that are similar to odor receptors in the nose. This has lead researchers to believe that sperm can detect the "odor" of the released egg, and literally are following its scent to locate it and attempt to fertilize it. It was once thought that the best time to either have sex to get pregnant, or to abstain from sex to keep from getting pregnant was at the time of ovulation. In reality, the best time to have sex if one to two days before ovulation, so that sperm cells have enough time to swim up through the uterus and the fallopian tubes to be waiting for the egg when it is ejected from the ovary at ovulation. Following ovulation, changes in a woman's hormones produce changes in the secretions at the cervix (the opening to the uterus, at the blind end of the vagina), and these thicken to form a barrier intended to protect the potentially developing embryo (if the egg has been fertilized). It is extremely difficult for sperm to penetrate this mucus barrier, and therefore more difficult for the egg to be fertilized after ovulation has occurred.

The Reproductive System Gonads – primary sex organs Testes in males Ovaries in females Gonads produce gametes (sex cells) and secrete hormones Sperm – male gametes Ova (eggs) – female gametes Slide 16.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Meiosis Make sex cells through process called Meiosis: In humans each body (somatic cell) has 46 chromosomes = diploid Sex cells are haploid (23 chromosomes) Meiosis = type of cell division that reduces the chromosomes # in half so that during fertilization, get correct amt. of chromosomes. This process occurs in two divisions

Male Reproductive System Testes: Produce sperm and male sex hormones Accessory Organs forming Male Duct System {Transports sperm}: Epididymis Ductus deferens Urethra Slide 16.2a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Male Reproductive System Accessory organs: Seminal vesicle Prostate gland Bulbourethral gland External genitalia: Penis Scrotum Slide 16.2b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Male Reproductive System Figure 16.2 Slide 16.2c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Testes Coverings of the testes Tunica albuginea – capsule that surrounds each testis Figure 16.1 Slide 16.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Testes Coverings of the testes (continued) Septa – extensions of the capsule that extend into the testis and divide it into lobules Figure 16.1 Slide 16.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Testes Each lobule contains one to four seminiferous tubules: Tightly coiled structures Function as sperm-forming factories Empty sperm into the rete testis Sperm travels through the rete testis to the epididymis Interstitial cells produce androgens such as testosterone Slide 16.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Epididymis Comma-shaped, tightly coiled tube – 20 ft. long Found on the superior part of the testis and along the posterior lateral side Functions to mature and store immature sperm cells (trip takes at least 20 days) Expels sperm with the contraction of muscles in the epididymis walls to the vas deferens Slide 16.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Ductus Deferens (Vas Deferens) Carries sperm from the epididymis to the ejaculatory duct Passes through the inguinal canal and over the bladder Moves sperm by peristalsis Spermatic cord – ductus deferens, blood vessels, and nerves in a connective tissue sheath (fig. 16.1) Slide 16.6a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Ductus Deferens (Vas Deferens) Ends in the ejaculatory duct which unites with the urethra Site of Vasectomy Vasectomy – cutting of the ductus deferens at the level of the testes to prevent transportation of sperm Slide 16.6b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Urethra Extends from the base of the urinary bladder to the tip of the penis Carries both urine and sperm Sperm enters from the ejaculatory duct Slide 16.7a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Urethra Regions of the urethra 1. Prostatic urethra –surrounded by prostate 2. Membranous urethra – from prostatic urethra to penis 3. Spongy (penile) urethra – runs the length of the penis Slide 16.7b

Seminal Vesicles Located at the base of the bladder Produces a thick, yellowish secretion = alkaline fluid rich in nutrients (60% of semen) Fructose (sugar) Vitamin C Prostaglandins Other substances that nourish and activate sperm Slide 16.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Prostate Gland Encircles the upper part of the urethra, below the bladder Secretes a milky, alkaline, fluid Helps to activate sperm motility Enters the urethra through several small ducts Slide 16.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Bulbourethral Glands Pea-sized gland inferior to the prostate Produces a thick, clear mucus for lubrication: Cleanses the urethra of acidic urine Serves as a lubricant during sexual intercourse Secreted into the penile urethra Slide 16.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Semen Mixture of sperm and accessory gland secretions Only 2-5 ml (teaspoon) of sperm is made during ejaculation: however, there are b/w 50 – 130 million per ml. Advantages of accessory gland secretions: Fructose provides energy for sperm cells Alkalinity of semen helps neutralize the acidic environment of vagina Semen inhibits bacterial multiplication Elements of semen enhance sperm motility Slide 16.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

SEMEN* Contains sperm cells (FROM TESTES), alkaline fluid (FROM PROSTATE), fructose (FROM SEMINAL VESICLE), & lubricant (FROM BULBOURETHRAL)

Infertility Male infertility may be caused by: obstructions of the duct system Hormonal imbalance Environmental estrogens Pesticides Excessive alcohol Semen analysis is one of the first series of tests done when couples are unable to conceive: look at sperm count, pH, volume, fructose content, etc. Sperm count lower than 20 million per ml makes impregnation improbable

External Genitalia Scrotum Divided sac of skin outside the abdomen Maintains testes at 3°C lower than normal body temperature to protect sperm viability The Cremaster muscle is an extension of the internal oblique muscle that elevates the scrotum during sexual arousal and exposures to the cold Slide 16.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

External Genitalia Penis Delivers sperm into the female reproductive tract Regions of the penis: Shaft Glans penis (enlarged tip) Prepuce (foreskin) Folded cuff of skin around proximal end Often removed by circumcision Slide 16.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

External Genitalia Internally there are three areas of spongy erectile tissue around the urethra Slide 16.13b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Spermatogenesis Production of sperm cells Begins at puberty and continues throughout life Occurs in the seminiferous tubules Slide 16.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Processes of Spermatogenesis Sperm cells are produced from spermatagonia cells, which contain 46 chromosomes (diploid) Spermatogonia (stem cells) undergo rapid mitosis to produce more stem cells before puberty Follicle stimulating hormone (FSH) modifies spermatogonia division: One cell produced is a stem cell The other cell produced becomes a primary spermatocyte Slide 16.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Processes of Spermatogenesis Primary spermatocytes undergo meiosis Haploid spermatids are produced Slide 16.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Processes of Spermatogenesis Spermiogenesis Late spermatids are produced with distinct regions Head – contains DNA covered by the acrosome Midpiece Tail Sperm cells result after maturing of spermatids Spermatogenesis takes 64 to 72 days Slide 16.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Processes of Spermatogenesis Spermatogonium (46 chromosomes) duplicates its DNA (mitosis). This gives rise to: One primary spermatocyte (46 chromosomes) which undergoes Meiosis I. Other stays at membrane as stem cell: This gives rise to 2 spermatocytes (46 chromosomes) which undergo Meiosis II This produces 4 spermatids (23 chromosomes) Then these cells mature into: Four sperm cells that collect in the lumen of the seminiferous tubule Sperm travel to, fully mature, and are stored in the epididymis Figure 16.3 Slide 16.17

Spermatogenesis http://www.youtube.com/watch?v=k2kclHg0ohU

Sperm Many things can suppress sperm production or mutate the sperm (2 heads / 2 tails. . . ): Antibiotics (penicillin) Radiation Lead Pesticides Marijuana Tobacco Excessive Alcohol

Anatomy of a Mature Sperm Cell The only human flagellated cell DNA is found in the head Acrosome  similar to lysosome, when comes into contact with egg, membrane breaks down and releases enzyme to allow it to penetrate Figure 16.5 Slide 16.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Sperm Penetrating Egg http://www.youtube.com/watch?v=CJakYmgtrDA &NR=1&feature=endscreen http://www.youtube.com/watch?v=fO4UWj01Gx 8

Hormonal Control of Male Reproductive Function 1. @ puberty, hypothalmus secretes a “releasing hormones” that target the male’s pituitary gland: 2. This pituitary gland secretes 2 gonadotropins: Follicle Stimulating hormone (FSH)  stimulates spermatogenesis in the seminiferous tubules Luteinizing Hormone (LH)  stimulates the interstitial cells between the seminiferous tubules to produce male sex hormones (testosterone)

Testosterone Production Male Sex hormones = Androgens The most important hormone of the testes = testosterone Produced in interstitial cells  production begins @ puberty Slide 16.19a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Testosterone Production Functions of testosterone: Stimulates reproductive organ development Underlies sex drive Causes secondary sex characteristics: Deepening of voice  affects vocal cords Increased hair growth Enlargement of skeletal muscles Thickening of bones Slide 16.19b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Regulation of Male Androgens (Sex Hormones) Figure 16.6 Slide 16.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Male Reproduction Disorders 1. Priapism  persistent, painful erections lasting 4+ hours. Not associated with sexual activity and is not relieved from an orgasm. Occurs when blood flows into penis, but is not adequately drained. Causes = alcohol or drug abuse, medication, spinal cord problems or injuries, anesthesia, blood diseases . . . 2. Balantis  inflammation of the head of the penis. Often occurs in men and boys who have not been circumcised and who have poor hygiene. Sweat, dirt, and bacteria build and cause foul smell that accumulates under the foreskin. 3. Chriptorchidism  male testes and female ovaries during development are made in the approximately same location of the abdomen; however, testes descend into the outer scrotum: failure of this descent = this condition. If untreated, can lead to sterility, surgery can rectify this problem. 4. Prostate Cancer cancer that starts in the prostate. As men age (see in men 75+, rare to see in 40’s), their prostate enlarges and is called benign prostatic hyperplasia (BPH)  this can increase your PSA blood test results, not necessarily raise your risk of cancer. Signs: delayed / slow start of urinary system, dribbling or leaking after urinating, blood in urine or semen, bone pain or tenderness (if cancer has spread)

UPDATED RESEARCH ABOUT SPERM: http://www.nature.com/news/1998/030127/full/ne ws030127-14.html http://www.nature.com/news/1998/020708/full/ne ws020708-10.html