Anatomy and Physiology of Male Mammal Reproductive Organs

1. Animal, Plant & Soil Science Lesson C4-1 Anatomy and Physiology of Animal Reproductive Systems

2. What are the major reproductive organs in male mammals? Whatare the functions of those organs? • To have a successful livestock operation, a producer must have an understanding of the various reproductive organs and their functions. • In most cases, a livestock operation will have only a limited number of males available for breeding. • The male reproductive system contains several interconnected parts that must all work together for successful mating.

3. What are the major reproductive organs in male mammals? Whatare the functions of those organs? • Some of the major organs found in the male mammal reproductive system are: • A. Testicles—The testicles produce sperm, the male sex cells (also called spermatozoa). • They also produce a hormone called testosterone that causes the appearance and behavior of the animal to be masculine. • Two testicles are present in male mammals.

4. What are the major reproductive organs in male mammals? Whatare the functions of those organs? • B. Epididymis—The epididymis is the storage site for sperm cells. • From the testicle, these cells enter the epididymis to mature. • Sperm can fertilize a female’s ova (female sex cell) as it travels through the epididymis. • A separate epididymis is attached to each testicle.

5. What are the major reproductive organs in male mammals? Whatare the functions of those organs? • C. Scrotum—The scrotum is a two-lobed sac that contains and protects the two testicles. • It also regulates the temperature of the testicles, which is lower than the body temperature. • When the environment temperature is low, the scrotum contracts, pulling the testicles toward the body and its warmth.

6. What are the major reproductive organs in male mammals? Whatare the functions of those organs? • When the environmental temperature is high, the scrotum relaxes, permitting the testicles to drop away from the body. • Maintaining the correct temperature is critical because extreme temperatures (too hot or too cold) can affect the production and vitality of sperm.

7. What are the major reproductive organs in male mammals? Whatare the functions of those organs? • D. Vas deferens—The vas deferens is essentially a transportation tube that carries the sperm-containing fluid from each epididymis to the urethra. • E. Urethra—The urethra is a large, muscular canal extending from the urinary bladder. • Both semen and urine move through the urethra to the end of the penis.

8. What are the major reproductive organs in male mammals? Whatare the functions of those organs? • F. Accessory sex glands—These are several glands that add volume and nutrition to the sperm-rich fluid coming from the epididymis. • G. Seminal vesicles—The seminal vesicles open into the urethra. • They produce a fluid that protects and transports the sperm. • H. Prostate gland—The prostate gland is near the urethra and the bladder. • It produces a fluid that is mixed with the seminal fluid.

9. What are the major reproductive organs in male mammals? Whatare the functions of those organs? • I. Cowper’s gland—The cowper’s gland produces a fluid that moves down the urethra ahead of the seminal fluid. • This fluid cleans and neutralizes the urethra, which helps protect the sperm as they move through the urethra. • The mixture of the seminal and prostate fluid and the sperm is called semen.

10. What are the major reproductive organs in male mammals? Whatare the functions of those organs? • J. Penis—The penis deposits the semen within the female reproductive system. • The urethra in the penis is surrounded by spongy tissue that fills with blood when the male is sexually aroused, which causes an erection that is necessary for copulation (mating) to occur. • The sigmoid flexure (found in bulls, rams, and boars) and the retractor muscle extend the penis from the sheath, which is a tubular fold of skin. • Horses and other mammals do not have a sigmoid flexure.

12. What are the major reproductive organs in female mammals? What are the functions of those organs? • Like males, female mammals have a complex system of organs that compose the reproductive system. • It is important that those interested in animal production be familiar with these various organs and their functions. • Some of the major organs that compose the female reproductive tract are:

13. What are the major reproductive organs in female mammals? What are the functions of those organs? • A. Ovary—The ovary produces female gametes, which are sex cells that can unite with other sex cells. • These are called ova (eggs). • A female mammal will typically have two ovaries, which also produce the female sex hormones: estrogen and progesterone. • Within each ovary, there are hundreds of tiny follicles or cavities. • The ova are produced in the follicles. • Each ovum is the largest single cell in the body.

14. What are the major reproductive organs in female mammals? What are the functions of those organs? • B. Oviducts—The oviducts are two tubes that carry the ova from the ovaries to the uterus. • The oviducts are also called the fallopian tubes. • The oviducts are close, but they are not attached to the ovaries. • The funnel-shaped end of each oviduct that is close to the ovary is the infundibulum. • At ovulation the follicle ruptures, releasing an ovum that is caught by the infundibulum.

15. What are the major reproductive organs in female mammals? What are the functions of those organs? • After copulation, sperm move through the uterus to the oviduct. • Fertilization of the ovum occurs in the upper end of the oviduct. • The zygote, or fertilized egg cell, moves to the uterus about two to four days after fertilization.

16. What are the major reproductive organs in female mammals? What are the functions of those organs? • C. Uterus—The uterus of mammals is a Y-shaped structure consisting of the body, two uterine horns, and the cervix. • The size and shape of the uterus varies among mammals. • The upper part of the uterus consists of the two uterine horns that develop into the oviducts or fallopian tubes.

17. What are the major reproductive organs in female mammals? What are the functions of those organs? • Mammals that normally produce large numbers of offspring at each breeding have relatively large horns and a small body. • Those mammals that normally produce single offspring or twins have smaller horns and a larger body. • In most mammals, pregnancy normally occurs in the uterine horns. • In horses, however, pregnancy normally occurs in the body of the uterus.

18. What are the major reproductive organs in female mammals? What are the functions of those organs? • In all mammals, the fetus grows within the uterus, where it remains until parturition or birth. • The cervix is the lower outlet of the uterus and is composed primarily of connective tissue that constitutes the gateway between the uterus and the vagina. • Like the rest of the reproductive tract, the cervix is lined with mucosal cells. • These cells make significant changes as the animal goes from one estrous cycle to another and during gestation or pregnancy.

19. What are the major reproductive organs in female mammals? What are the functions of those organs? • D. Vagina—The vagina serves as the female organ of copulation at mating and as the birth canal at parturition. • It is the passage between the cervix and the vulva. • The lining is moist during estrus and dry when the animal is not in estrus.

20. What are the major reproductive organs in female mammals? What are the functions of those organs? • E. Bladder—The bladder collects the liquid waste, which is called urine. • The urine passes through the urethra to the vagina. • The urethra attaches to the floor of the vagina between the cervix and the vulva. • The bladder is not considered part of the reproductive tract in females.

21. What are the major reproductive organs in female mammals? What are the functions of those organs? • F. Vulva—The vulva is the external opening of the reproductive and urinary systems. • The exterior and visible part of the vulva consists of two folds called the labia majora. • The labia minora are two folds located just inside the labia majora.

22. What are the major reproductive organs in female mammals? What are the functions of those organs? • G. Clitoris—The clitoris is the sensory and erectile organ of the female. • It is located just inside the vulva. • The clitoris develops from the same embryonic tissue as the penis in the male and produces sexual stimulation during copulation.

23. What are the involved steps and processes of spermatogenesis and oogenesis? What are the characteristics of sperm and eggs? • For an animal to effectively reproduce, the processes of spermatogenesis with males or oogenesis with females must be viable for an animal’s reproductive development. • Spermatogenesis is the production of sperm and oogenesis is the production of egg cells. • A. The process of spermatogenesis has many steps for effective sperm production. • Spermatogonia, defined as primitive differentiated male gametes, are found along the outside wall of the seminiferous tubules. • As these gametes increase in number due to mitosis, each increases in size and develops into a primary spermatocyte.

24. What are the involved steps and processes of spermatogenesis and oogenesis? What are the characteristics of sperm and eggs? • The process of spermatogenesis begins as the two secondary spermatocytes develop when each primary spermatocyte undergoes the first meiotic division. • After this division is complete, the second meiotic division begins. • Four spermatids develop after the second meiotic division. • Each spermatid contains the haploid number of chromosomes.

26. What are the involved steps and processes of spermatogenesis and oogenesis? What are the characteristics of sperm and eggs? • For example, human sperm cells contain 23 chromosomes, swine have 19 chromosomes, sheep have 27 chromosomes, cattle have 30 chromosomes, dogs have 39 chromosomes, cats have 19 chromosomes, and chickens have 39 chromosomes.

27. What are the involved steps and processes of spermatogenesis and oogenesis? What are the characteristics of sperm and eggs? • As the spermatids develop into mature sperm, they lose a large amount of cytoplasm. • The nucleus is condensed into a head, and a whip- like flagella tail is developed. • There are three main structural characteristics of a mature sperm. • For an animal to have viable sperm, each must have a head, body, and tail in its sperm structure.

28. What are the involved steps and processes of spermatogenesis and oogenesis? What are the characteristics of sperm and eggs? • B. Much like spermagenesis, oogenesis is necessary for female animals to reproduce. • The steps of oogenesis are similar to spermagenesis in complexity, yet the steps differ in that only one sex cell is created, unlike the four sex cells created in spermagenesis. • The first step of oogenesis begins when the early germ cells, called oogonia, grow into primary oocytes. • The primary oocyte will divide into one polar body and one secondary oocyte.

29. What are the involved steps and processes of spermatogenesis and oogenesis? What are the characteristics of sperm and eggs? • The majority of the cytoplasm goes to the secondary oocyte, and the polar body is rather small. • Each oocyte contains the same number of chromosomes. • The secondary oocyte divides again, resulting in an ootid and another polar body. • Sometimes in oogenesis, the first polar body will divide into two polar bodies.

30. What are the involved steps and processes of spermatogenesis and oogenesis? What are the characteristics of sperm and eggs? • Oogenesis results in one large ootid that contains the haploid number of chromosomes and most of the cytoplasm and three polar bodies. • These polar bodies will disintegrate since they are nonfunctional. • The large ootid then grows into a functioning ovum. • The large size is needed to provide food for the embryo until it can receive nourishment from its mother.

31. What are the involved steps and processes of spermatogenesis and oogenesis? What are the characteristics of sperm and eggs? • C. Both the spermatid and ootid possess either all maternal chromosomes, paternal chromosomes, or a combination of chromosomes from the mother and father.

32. What are the methods used to castrate and neuter animals?What are the benefits? • Neutering is used often in the agriculture industry to remove an animal’s reproductive capability to prevent the passing of inferior genetics throughout a herd, to improve the meat quality of an animal, or to aid in the animal’s management. • After being neutered, an animal’s sexual classification changes. • For example, a bull calf is defined as a young male bovine. • If the animal is castrated, it is classified as a steer, which is defined as a castrated male bovine.

33. What are the methods used to castrate and neuter animals?What are the benefits? • A. Castration is defined as the removal of an animal’s testicles. • Frequently, these procedures are performed between three to four months of age to limit the development of the genitals, weight loss, and bleeding of the animal. • The three most common types of castration are clamping, banding, and cutting.

34. What are the methods used to castrate and neuter animals?What are the benefits? • 1. Clamping involves using a pincer to sever the chord of each testicle. • The process involves no blood and is considered a nonsurgical procedure. • 2. Banding involves a special instrument that places a tight rubber band around the base of the scrotum. • The band isolates the blood supply from the testicles, causing the testicles to wither from a lack of blood. This process involves no blood. • 3. Cutting involves surgically removing the testes.

35. What are the methods used to castrate and neuter animals?What are the benefits? • B. Spaying deals with the removal of a female animal’s ovaries or cutting of the fallopian tubes so eggs cannot enter the uterus to be fertilized and develop into an embryo.

36. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • Reproduction is a series of events and phases that an animal experiences. • Each event takes place in a certain order. • The properly timed completion of these phases affects success. • Some of the important phases in reproductive development are:

37. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • A. Puberty—Puberty is the time at which animals reach a level of sexual development that makes them capable of reproduction. • Puberty in female animals is the age of the first estrus with ovulation. • Puberty in males is the first ejaculate with fertile sperm. • Neither males nor females are sexually mature at puberty.

38. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • The female is often too small to bear young. • The male is not highly fertile and is not capable of breeding regularly. • Environmental and genetic factors affect the age at which puberty occurs.

39. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • B. Fertilization—Fertilization is the union of a sperm and an ovum or egg. • The sperm penetrates the ovum, and pairs of genetic material are formed. • The fertilized ovum is called a zygote. • C. Gestation—Gestation is the period of pregnancy. It begins with conception and lasts until parturition (birth). • The length of gestation varies between animals.

40. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • D. Parturition—Parturition is the process of giving birth. • Several hormone levels change and initiate the process. • Behavior changes can be observed that indicate the animal is nearing parturition. • For example, females can exhibit a “nesting” behavior. • They become restless and attempt to separate from the herd.

41. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • The first stage of parturition includes dilation of the cervix and entry of the fetus into the cervix. • This is usually the longest stage, ranging from one to 12 hours. • The second stage involves strong contractions, leading to the birth of an animal. • The last stage of parturition is the expulsion of the afterbirth (placenta) from the uterus, which normally occurs shortly after giving birth.

42. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding?

43. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • E. Lactation—Lactation is the production of milk. • Hormones that trigger the onset of lactation also play an important role in parturition. • F. Incubation—Incubation is the development of a new animal in the fertile egg of poultry, fish, and other egg-laying species. • This occurs outside the body of the female.

44. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • Four important factors in incubating eggs are: • 1. Temperature—The temperature should be maintained at 99 to 103°F (37.2 to 39.4°C). • 2. Humidity—The humidity should be approximately 60 percent during the first 18 days and 70 percent during the last three days. • 3. Oxygen—Sufficient air exchange is necessary to prevent carbon dioxide buildup while maintaining a 21 percent oxygen level.

45. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • 4. Egg rotation—Eggs should be rotated two to five times daily for the first 18 days.

46. What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding? • K. Spawning—Spawning is the releasing of eggs by a female fish and the subsequent fertilization by the male. • A female may lay thousands of eggs at one spawning. • The male fish then fertilizes the eggs by releasing sperm on the mass of eggs.

47. Reproductive Hormones • Follicle stimulating hormone (FSH) • Stimulates estrogen production in maturing follicles • In conjunction with estrogen, induces LH receptors • Luteinizing hormone (LH) • In conjunction with FSH and estrogen, causesfinal development of the follicle destined to ovulate

48. Hormones Cont. • Estrogen • Gonadotropin-releasing hormone (GnRH) • Stimulates the release of both LH and FSH from the pituitary gland (ovulation) • Oxytocin • Stimulates milk let-down • Progesterone • Decreases the frequency of gonadotropin (LH and FSH) release to prevent ovulation.

49. Review • What are the major reproductive organs in male mammals? What are the functions of those organs? • What are the major reproductive organs in female mammals? What are the functions of those organs? • What are the involved steps and processes of spermatogenesis and oogenesis? What are the characteristics of sperm and eggs?

50. Review • What the major male and female reproductive organs in poultry, and what are their functions? • What are the methods used to castrate and neuter animals? What are the benefits? • What are the phases of reproductive development in the life of an animal? How do you determine animal readiness for breeding?