Text Material Preview
22.17.19 N 57.0 4G : KB/S 71 50 Something has to move the spermatozoa from the epididy- mis (located way down in the scrotum) up to the urethra SEMINAL VESICLES (within the pelvic cavity) when ejaculation occurs. This is Ducts from the two seminal vesicles, sometimes called vesic- the job of the vas deferens. Also known as the ductus ular glands, enter the pelvic urethra in the same area as the CHAPTER 19 The Reproductive System 475 Bladder Bladder Bladder Ureter Ureter Bladder Ureter Ampullary Ureter gland Ampullary gland Vas deferens Vas deferens Vas deferens Vas deferens Seminal Seminal Seminal Ampullary vesicle vesicle vesicle gland Prostate Prostate Prostate Prostate Urethra Urethra Urethra Urethra Bulbourethral Bulbourethral Bulbourethral gland gland gland Beginning Beginning Beginning Beginning A of penis of penis of penis D of penis B C FIGURE 19-11 Accessory reproductive glands. Comparisons among some common domestic species (dorsal A, Stallion B, Bull. C, D, Dog. TABLE 19-3 Male Accessory Reproductive Glands secretions into the urethra. It is present in all common domestic animals. In dogs, it is particularly large because it BULBOURETHRAL is the only accessory reproductive gland they have. ANIMAL SEMINAL VESICLES PROSTATE GLAND GLANDS Boar + + BULBOURETHRAL GLANDS Bull + + The two bulbourethral glands, also known as the Cowper's Cat + glands, are located further caudally than the other accessory Dog + reproductive glands. Their ducts enter the urethra back near Human + the caudal border of the pelvis. They secrete a mucinous Ram + + + (mucus-containing) fluid just before ejaculation that clears Stallion + + + and lubricates the urethra for the passage of semen. All +, Indicates the presence of a gland; indicates the gland is absent. common domestic animals have bulbourethral glands except for the dog. CLINICAL APPLICATION PENIS The penis is the male breeding organ. It is made up mainly Vasectomy of muscle, erectile tissue, and connective tissue, with the If a section of each vas deferens is removed surgically from urethra running down its center. It has a very large blood an animal, the animal is rendered sterile (it cannot repro- supply and many sensory nerve endings. When the male is duce). This procedure is known as a vasectomy. It prevents sufficiently aroused and stimulated, the erectile tissue spermatozoa from reaching the urethra during ejaculation. becomes engorged with blood, causing the penis to enlarge The other components of semen are ejaculated, but no sper- and stiffen. This allows it to be inserted into the vagina of matozoa are included. The individual is "firing blanks," to speak. The spermatozoa live out their lives in the epididymis, the female for breeding. die, and are absorbed by the lining cells. The three main parts of the penis are the roots, the body, Vasectomy is a common contraceptive surgery to prevent and the glans. pregnancy in humans. It is performed less commonly for that reason in nonhuman animals but is sometimes per- ROOTS formed on bulls to create "teaser" animals. Teaser bulls are The roots of the penis attach it to the brim of the pelvis. used to help identify in heat so that they can be bred, They consist primarily of two bands of connective tissue, often by artificial insemination, to other males. called the crura, covered by the ischiocavernosus muscles. BODY vas deferens. They are present in all common domestic The body of the penis is its largest part. It is mainly made animals except for cats and dogs. up of two bundles of erectile tissue. Erectile tissue is com- posed of a spongy network of fibrous connective tissue and PROSTATE GLAND many tiny, blood-filled spaces called sinuses. In the nonerect The prostate gland is a single structure that more or less state, the amount of blood flowing into the erectile tissue is completely surrounds the urethra. Multiple ducts carry its the same as the amount flowing out. When more blood flows 476 CHAPTER 19 The Reproductive System into erectile tissue than leaves it however, the sinuses engorge causes the male and female to remain stuck together after 4 T Isi & Konver Edit Anotasi Semua Tanda T... si
