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APHY 201 Exam 5d
Ch. 20 - The Male Reproductive System & Sexual Reproduction
| Question | Answer |
|---|---|
| What is the primary benefit of sexual reproduction? | It provides genetic diversity and is considered the foundation for the survival and evolution of species. |
| What elements combine to form a fertilized egg, or zygote? | Male and female gametes, which are sex cells, combine their genes to form a fertilized egg. |
| Which parent is considered the male? | The parent producing the gamete that has motility, known as the sperm or spermatozoon, is considered the male. |
| Which sex chromosome is unique to the male? | The male has the Y chromosome. |
| Which gamete contains most of the nutrients for the developing zygote? | The other gamete, called the egg or ovum, contains most of the nutrients for the developing zygote. |
| Which parent is considered the female? | The parent producing eggs is considered the female. |
| What additional roles does the female mammal have during reproduction? | In mammals, the female also provides shelter for the developing fetus via the uterus and placenta. |
| What are the primary sex organs? | The primary sex organs are the testes or ovaries, which are the organs that produce the gametes like sperm and eggs. |
| What are the secondary sex organs in males? | Male secondary sex organs include the ducts, glands, and the penis, which serve to deliver the sperm cells. |
| What are the secondary sex organs in females? | Female secondary sex organs include the uterine tubes, the vagina that receives the sperm, and the uterus which nourishes the developing fetus. |
| What are secondary sex characteristics? | Secondary sex characteristics are features that develop at puberty to attract a mate. |
| What are examples of secondary sex characteristics in males? | In males, these features include pubic, axillary, and facial hair, scent glands, body morphology, and a low-pitched voice. |
| How many pairs of homologous chromosomes do human cells contain? | Our cells contain 23 pairs of homologous chromosomes. |
| How are the 23 pairs of chromosomes categorized? | They are categorized as 22 pairs of autosomes and 1 pair of sex chromosomes. |
| What are the sex chromosomes for males and females? | Males have XY sex chromosomes, and females have XX sex chromosomes. |
| What percentage of Y-carrying and X-carrying sperm do males produce? | Males produce 50% Y-carrying sperm and 50% X-carrying sperm. |
| What sex chromosome do all eggs carry? | All eggs carry the X chromosome. |
| How is the biological sex of a child determined? | The sex of the child is determined by the type of sperm that fertilizes the mother's egg. |
| When do gonads begin to develop and what are they called initially? | Gonads begin to develop at 6 weeks as gonadal ridges located near the primitive kidneys, or mesonephros. |
| What two sets of ducts exist at 6 weeks of embryonic development? | The two sets of ducts are the mesonephric, or Wolffian, ducts and the paramesonephric, or Müllerian, ducts. |
| What do the mesonephric ducts develop into? | The mesonephric ducts develop into the male reproductive system, which causes the paramesonephric ducts to degenerate. |
| What do the paramesonephric ducts develop into? | The paramesonephric ducts develop into the female reproductive tract, which causes the mesonephric ducts to degenerate. |
| What is the SRY gene? | The SRY gene stands for the Sex-determining Region of the Y gene. |
| What does the SRY gene do in males? | In males, it codes for a protein called the testis-determining factor, which causes the development of testes. |
| What do the newly developed testes secrete? | The testes secrete testosterone and müllerian-inhibiting factor. |
| What is the function of the müllerian-inhibiting factor? | It degenerates the paramesonephric ducts, although a part remains as a vestigial uterus and uterine tubes in the area of the prostatic urethra, called the uterus masculinus. |
| Does female development require estrogens? | Female development occurs in the absence of male hormones, not in the presence of estrogens, because maternal estrogens are high in all pregnancies. |
| What hormones cause male development? | Androgens cause maleness. |
| What is the genetic makeup of someone with Androgen-Insensitivity Syndrome? | They are genetically male with XY chromosomes. |
| What do the abdominal testes secrete in individuals with this syndrome? | Testosterone is secreted by the abdominal testes, along with a small amount of estrogen. |
| Why do no masculinizing effects occur in this syndrome? | Target cells lack receptors for testosterone, so the hormone is made but the body cannot respond to it. |
| How do individuals with Androgen-Insensitivity Syndrome develop externally? | Males grow as females externally through puberty. |
| What female internal structures are absent in this syndrome? | There are no ovaries, uterus, or vagina present. |
| What is a major health risk associated with Androgen-Insensitivity Syndrome? | The abdominal testes are at high risk for testicular cancer. |
| What three structures do all 8-week-old fetuses have? | All 8-week-old fetuses have a phallus, urogenital folds, and labioscrotal folds. |
| When do fetuses begin to show sexual differentiation? | By the end of week 9, fetuses begin to show sexual differentiation. |
| When is the external genitalia distinctly male or female? | The genitalia is distinctly male or female by the end of week 12. |
| Where do the testes begin their development? | The testes begin development near the kidney. |
| What is the gubernaculum? | The gubernaculum is a cordlike structure containing muscle that extends from the gonad to the abdominopelvic floor. |
| How do the testes travel to the scrotum? | The gubernaculum shortens and guides the testes through the abdominal wall via the inguinal canal to the scrotum. |
| What structures accompany the testes during their descent? | The testes are accompanied by the testicular nerve, artery, and vein. |
| When does the descent of the testes begin and end? | Descent begins in weeks 6 to 10 and is finished by week 28. |
| What is cryptorchidism? | Cryptorchidism is a condition where boys are born with undescended testes, which affects 3% of boys. |
| Why must the testes be located outside the pelvic cavity? | Location outside the pelvic cavity is essential to maintain the lower temperatures needed for sperm production. |
| What are the dimensions of the testes? | The testes are oval organs that are 4 cm long and 2.5 cm in diameter. |
| What covers the anterior portion of the testes? | They are covered anteriorly by the tunica vaginalis, a saclike extension of the peritoneum that descended into the scrotum with the testes. |
| What is the tunica albuginea? | The tunica albuginea is a white fibrous capsule that covers the testes. |
| What divides the testes into internal compartments? | Septa divide the organ into compartments that contain seminiferous tubules where sperm are produced. |
| What lines each seminiferous tubule? | Each tubule is lined with a thick germinal epithelium composed of germ cells in the process of becoming sperm. |
| What is the function of sustentacular cells? | Sustentacular cells, also known as Sertoli cells, sustentocytes, or nurse cells, promote sperm cell development. |
| How is the blood-testis barrier formed? | The blood-testis barrier is formed by tight junctions between sustentacular cells. |
| What is the purpose of the blood-testis barrier? | It separates sperm from the man's immune system, which would otherwise attack the sperm as foreign entities. |
| Where do seminiferous tubules drain sperm and testicular fluid? | They drain through the straight tubules, or tubulus rectus, into a network called the rete testis. |
| Where do sperm go after passing through the rete testis? | They travel to the efferent ductules and then into the head of the epididymis where the sperm mature. |
| Why do sperm develop very large mitochondria? | The low blood pressure of the testicular artery results in a poor oxygen supply, so large mitochondria help sperm survive the hypoxic environment of the female reproductive tract. |
| Where do the right and left testicular veins drain? | The right testicular vein drains into the inferior vena cava, while the left testicular vein drains into the left renal vein. |
| What is the scrotum? | The scrotum is a pendulous pouch holding the testes, divided into two compartments by a median septum. |
| What structure travels up from the scrotum through the inguinal canal? | The spermatic cord travels up from the scrotum to pass through the abdominal wall via the inguinal canal. |
| What components does the spermatic cord contain? | It contains the ductus deferens, cremaster muscle, testicular artery, pampiniform plexus of veins, testicular nerve, and lymphatics. |
| Why is testicular thermoregulation necessary? | It is necessary because sperm cannot be produced at core body temperature. |
| What is the function of the cremaster muscle? | The cremaster muscle consists of segments of skeletal muscle from the internal abdominal oblique muscle that pull the testes closer to the body when the external temperature is too cold. |
| What does the dartos muscle do? | The dartos muscle is a smooth muscle that wrinkles the skin, reducing the surface area of the scrotum and lifting it upwards when external temperatures are cold. |
| What is the function of the pampiniform plexus? | The pampiniform plexus consists of veins ascending near the testicular artery that act as a countercurrent heat exchanger, cooling arterial blood entering the testis like adjacent cold and hot pipes in a wall. |
| What are the efferent ductules? | Efferent ductules are 12 small ciliated ducts that collect sperm from the rete testis and drive them along to the epididymis. |
| What are the parts and dimensions of the epididymis? | The epididymis consists of a head, body, and tail, forming a 6-meter-long coiled duct adhering to the posterior of the testis. |
| What occurs in the epididymis? | It is the site of sperm maturation and storage. |
| How long are sperm viable in the epididymis? | Sperm are viable for 60 days, and if they are not used by then, they are reabsorbed. |
| What is the ductus deferens? | The ductus deferens is a muscular tube 45 cm long passing up from the scrotum through the inguinal canal to the posterior surface of the bladder, and it exhibits peristalsis during orgasm. |
| How is the ejaculatory duct formed and where does it go? | The 2 cm ejaculatory duct is formed from the ductus deferens and seminal vesicle, passing through the prostate to empty into the urethra. |
| What are the regions of the male urethra and its total length? | The regions are the prostatic, membranous, and penile urethra, which total 20 cm in length. |
| Where are the seminal vesicles located and what is their function? | They are located posterior to the bladder, empty into the ejaculatory duct, and contribute the majority, or 60%, of seminal fluid. |
| Describe the location, size, and function of the prostate gland. | The prostate gland is located below the bladder, surrounds the urethra and ejaculatory duct, measures 2 x 4 x 3 cm, and contributes 30% of seminal volume. |
| What is the function of the bulbourethral glands? | Located near the bulb of the penis, they empty into the penile urethra and produce a lubricating fluid that neutralizes the acidity of residual urine which would harm sperm. |
| What is the growth pattern of the prostate gland as a man ages? | The prostate gland stops growing at age 20, then recommences growing slowly after age 45. |
| What percentage of men show benign prostatic hyperplasia by age 70? | By age 70, 90% of men show some degree of benign prostatic hyperplasia. |
| What natural supplement is often prescribed for benign prostatic hyperplasia? | Saw palmetto is a natural supplement often prescribed for this condition. |
| How common is prostate cancer? | Prostate cancer is the second most common cancer in men over 50. |
| Why does prostate cancer often go undetected initially? | It often goes unnoticed until it causes pain. |
| What factor leads to poor survival rates in prostate cancer? | Survival is poor if the cancer metastasizes to the lymph nodes, lungs, or other organs. |
| In which demographic is prostate cancer more common? | It is more common among American blacks than whites. |
| How is prostate cancer diagnosed? | It is diagnosed with a digital rectal examination and tests for PSA, or Prostate specific antigen, and acid phosphatase. |
| What are the main anatomical regions of the penis? | The penis consists of an internal root, a visible shaft, and a glans. |
| How long is the external portion of the penis when flaccid? | The external portion is 4 inches long when flaccid. |
| What covers the glans of the penis? | The skin extends over the glans as the prepuce or foreskin. |
| How many cylindrical bodies of erectile tissue make up the penis? | The penis consists of 3 cylindrical bodies of erectile tissue. |
| Which erectile tissue encloses the penile urethra? | A single corpus spongiosum along the ventral side of the penis encloses the penile urethra. |
| Where does the corpus spongiosum end? | It ends as a dilated bulb ensheathed by the bulbospongiosus muscle. |
| Describe the paired corpora cavernosa. | The paired corpora cavernosa diverge like arms of a Y in the pelvic cavity, and each crus or arm attaches to the pubic arch and is covered with the ischiocavernosus muscle. |
| What do all three cylinders of erectile tissue contain? | All three cylinders contain tiny blood sinuses called lacunae with connective tissue and smooth muscle trabeculae between them. |
| What triggers the development of the reproductive system after birth? | A surge of pituitary gonadotropins begins development after years of dormancy. |
| At what ages does the reproductive system begin development in boys and girls? | Development begins at ages 10 to 12 in most boys and 8 to 10 in most girls. |
| How is adolescence defined? | Adolescence is the period from the onset of gonadotropin secretion until a person attains full adult height. |
| How is puberty defined? | Puberty constitutes the first few years of adolescence from the onset of gonadotropin secretion until the first menstrual period in girls at age 12, or the first ejaculation of viable sperm in boys at age 14. |
| What hormone does the mature hypothalamus produce? | The mature hypothalamus produces GnRH. |
| What does the stimulation of gonadotrope cells in the anterior pituitary cause? | It causes the secretion of FSH and LH. |
| What is the function of Luteinizing Hormone (LH)? | LH stimulates interstitial cells, or Leydig cells, to produce testosterone and is also known as interstitial cell-stimulating hormone, or ICSH. |
| What is the function of Follicle-Stimulating Hormone (FSH)? | FSH stimulates sustentacular, or Sertoli, cells to secrete androgen-binding protein (ABP) that interacts with testosterone to stimulate spermatogenesis. |
| What are the physical effects of testosterone on the body? | Testosterone enlarges secondary sexual organs like the penis, testes, scrotum, ducts, glands, and muscle mass, and it develops hair, scent, and sebaceous glands. |
| How does testosterone affect the brain and blood? | It stimulates erythropoiesis and libido, as brain neurons convert it to estrogen. |
| What maintains functions during adulthood? | During adulthood, testosterone sustains libido, spermatogenesis, and the reproductive tract. |
| How is testosterone converted in the brain? | Testosterone is converted to estradiol by aromatase in the brain. |
| How does testosterone secretion change with age? | Peak secretion is at 7 mg/day at age 20, and it declines to 1/5 of that by age 80. |
| What causes the male climacteric, or andropause? | A rise in FSH and LH secretion after age 50 produces the male climacteric. |
| What are the symptoms of andropause? | Most men have minor or no symptoms, but some experience mood changes, hot flashes, and illusions of suffocation. |
| How prevalent is impotence, or erectile dysfunction, with aging? | It affects 20% of men in their 60s and 50% of men in their 80s. |
| Are men with erectile dysfunction still able to ejaculate? | Over 90% of impotent men remain able to ejaculate. |
| What does mitosis produce and what is its purpose? | Mitosis produces 2 genetically identical diploid daughter cells, which are used for tissue repair and embryonic growth. |
| What does meiosis produce? | Meiosis produces gametes, which are haploid cells required for sexual reproduction. |
| How many cell divisions occur during meiosis? | Meiosis involves 2 cell divisions after only one replication of DNA. |
| What happens during meiosis I? | Meiosis I separates homologous chromosome pairs, resulting in 2 haploid cells with 2 chromatids per chromosome, known as "double-copied." |
| What happens during meiosis II? | Meiosis II separates duplicated sister chromatids, resulting in 4 haploid cells with 1 chromatid per chromosome, known as "single-copied." |
| What is the long-term effect of meiosis on chromosomes? | Meiosis keeps the chromosome number constant from generation to generation after fertilization. |
| Where does meiosis occur in males? | It occurs in the seminiferous tubules of males. |
| What two kinds of daughter cells do spermatogonia produce? | They produce type A cells that remain outside the blood-testis barrier to produce more daughter cells, and type B cells that differentiate into primary spermatocytes. |
| How do developing cells move toward the lumen? | Cells must pass through the blood-testis barrier to move inward toward the lumen, and new tight junctions form behind these cells. |
| What do primary spermatocytes become after meiosis I? | After meiosis I, they become 2 secondary spermatocytes. |
| What do secondary spermatocytes become after meiosis II? | After meiosis II, they become 4 spermatids. |
| What is spermiogenesis? | Spermiogenesis is the transformation of spermatids into spermatozoa, where the cell sprouts a tail and discards cytoplasm to become lighter. |
| Is spermiogenesis the same process as spermatogenesis? | No, spermiogenesis is the last part of spermatogenesis, and they are not the same. |
| How do spermatocytes physically move toward the lumen? | Spermatocytes squeeze between Sertoli, or nurse, cells toward the lumen. |
| Describe the head of the spermatozoon. | The head is a pear-shaped front end that is 4 to 5 microns long, containing the nucleus, acrosome, and basal body of the tail's flagellum. |
| What does the nucleus of the spermatozoon contain? | The nucleus contains a haploid set of chromosomes. |
| What is the function of the acrosome? | The acrosome contains enzymes that penetrate the egg, such as hyaluronidase which acts on hyaluronic acid, or bioglue. |
| What are the three regions of the spermatozoon tail? | The tail is divided into the midpiece, principal piece, and endpiece. |
| What does the midpiece of the tail contain? | The midpiece contains mitochondria around the axoneme of the flagella that produce ATP for flagellar movement. |
| Describe the principal piece and endpiece of the tail. | The principal piece is an axoneme surrounded by fibers, and the endpiece is the very narrow tip of the flagella, consisting of a bare axoneme. |
| What is the volume and composition of fluid expelled during orgasm? | Approximately 2-5 mL of fluid is expelled, consisting of 60% seminal vesicle fluid, 30% prostatic fluid, and 10% sperm. |
| What is considered a normal sperm count? | A normal sperm count is 50-120 million/mL, and less than 25 million/mL is associated with infertility. |
| How have chemical pollutants affected male sperm counts? | "Estrogen mimic" chemical pollutants appear to be sharply decreasing male sperm counts from 113 million/mL in 1940 to 66 million/mL in 1990, and are linked to increased rates of testicular cancer, hypospadias, and cryptorchidism. |
| What is the purpose of fructose in semen? | Fructose provides energy for sperm motility. |
| What causes semen to clot? | Enzymes convert proseminogelin to seminogelin, causing it to become a sticky, fibrin-like substance so semen adheres to the vagina and cervix. |
| What enzyme liquefies semen after it clots? | Serine protease, also known as PSA, breaks down seminogelin and liquefies semen within 30 minutes. |
| What is the role of prostaglandins in semen? | Prostaglandins stimulate female peristaltic contractions. |
| What protective base does prostatic fluid contain? | Prostatic fluid contains spermine, a base that stabilizes sperm pH at 7.2 to 7.6, neutralizes vaginal and male spermatic duct acidity, and protects and activates sperm. |
| Which arteries supply blood to the penis? | The dorsal and deep arteries, which are branches of the internal pudendal, supply the penis. |
| How does blood flow cause an erection? | Dilation of the deep artery fills the lacunae of the corpora cavernosa, causing an erection. |
| What nerves serve the penis? | The penis has an abundance of tactile, pressure, and temperature receptors, and the dorsal nerve of the penis and internal pudendal nerves lead to an integrating center in the sacral spinal cord. |
| What physiological changes characterize the excitement phase? | Excitement is characterized by vasocongestion of genitals, myotonia, and increases in heart rate, blood pressure, and pulmonary ventilation. |
| What triggers penile erection during excitement? | Erection of the penis is due to the parasympathetic triggering of nitric oxide secretion. |
| Does the corpus spongiosum become as engorged as the corpora cavernosa? | No, the corpus spongiosum is not nearly as engorged. |
| What happens to the erection during the plateau phase? | The erection is maintained during the plateau phase. |
| What defines an orgasm or climax? | Climax is a short, intense sensory reaction lasting 3 to 15 seconds that usually includes the discharge of semen. |
| What occurs during the emission phase of ejaculation? | During emission, the sympathetic nervous system propels sperm through ducts as glandular secretions are added. |
| What occurs during the expulsion phase of ejaculation? | During expulsion, semen in the urethra activates muscular contractions that lead to expulsion. |
| Are ejaculation and orgasm the exact same event? | No, ejaculation and orgasm are not the same and can occur separately. |
| What happens during the resolution phase? | Sympathetic signals constrict the internal pudendal artery and reduce blood flow to the penis, causing it to become soft and flaccid, a process known as detumescence. |
| What is the refractory period? | The refractory period lasts from 10 minutes to a few hours, during which it is impossible to attain another erection and orgasm. |
| How common is male breast cancer? | Breast cancer accounts for 0.2% of male cancers, with a ratio of 175 females to 1 male. |
| What is hypospadias? | Hypospadias is a congenital defect in which the urethra opens on the ventral side of the penis instead of at the tip. |
| What is a varicocele? | A varicocele is an abnormal dilation of the pampiniform plexus veins of the spermatic cord, often described as a "bag of worms." |
| Who is most commonly affected by testicular cancer? | Testicular cancer is common in young men aged 15 to 34 years old of middle and upper class backgrounds. |
| How does testicular cancer present and how is it detected? | It begins as a painless lump, is highly curable if detected early, and males should self-exam by palpation. |
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