Chapter 11 Reproductive system
Male reproductive system
The male dog is known as a dog; the male cat is known as a tomcat. The reproductive system of the dog and the tomcat are generally similar – any differences will be described where appropriate (Figs 11.1, 11.2). The parts of the male reproductive tract are:
The testis
The testis is the male gonad, with functions as follows:

Fig. 11.3 A Testis within scrotum. B Scrotum removed. C Cross-section through the seminiferous tubules.
Lying between the tubules are the cells of Leydig or interstitial cells. They secrete testosterone and are under the control of interstitial cell stimulating hormone (ICSH) (see Ch. 6), produced by the anterior pituitary gland.
Testicular descent
In the early embryo, the undifferentiated gonads develop inside the abdomen close to the kidney. In the male, the gonad becomes the testis and a band of tissue known as the gubernaculum forms and runs from the caudal end of each testis to the inside of the developing scrotal sac. During late gestation, the testes are pulled caudally by the contraction of the gubernaculum and they migrate through the abdomen. The testes leave the abdominal cavity viathe inguinal canal – a channel between the fibres of the external abdominal oblique muscle in the groin or inguinal area (see Ch. 4). As each testis with its associated blood capillaries, nerve and deferent duct passes through the inguinal canal into the scrotum, it becomes wrapped in a double fold of peritoneum which forms the tunica vaginalis (Fig. 11.3).
Deferent duct
The epididymis continues as the deferent duct (also called the vas deferens or ductus deferens; Figs 11.1, 11.2), which passes out of the scrotum into the abdominal cavity via the inguinal canal within the spermatic cord. The spermatic cord is wrapped in the tunica vaginalis and also contains the testicular artery and vein and the testicular nerve. Lying within the cord is a strip of muscle derived from the internal abdominal oblique muscle and known as the cremaster muscle. Contraction of this muscle raises the testis closer to the body in response to cold and works in conjunction with the Dartos muscle to maintain a constant temperature for the testes.
During ejaculation, the sperm and fluid produced in the seminiferous tubules are propelled along the epididymis and up the deferent duct, which joins the urethra. At this junction, the walls of the deferent ducts are thickened and glandular; the whole area is surrounded by the prostate gland (Figs 11.1, 11.2).
The penis
The functions of the penis are to:
The dog
The distal part of the penis is contained within a sheath of hairy skin known as the prepuce. This is suspended from the ventral abdominal wall and covers and protects the penis. It is lined with mucous membrane and is well supplied with lubricating glands. During mating, the prepuce is pushed back to reveal the glans penis. Afterwards, the retractor penis muscle pulls the penis back into the prepuce.
The tomcat
The main parts of the penis are similar to those of the dog, except that the cat penis is shorter and points backwards – the external opening is ventral to the anus (Fig. 11.2). The glans penis is covered with tiny barbs, which elicit a pain reflex as the male withdraws from the female after mating. This stimulates the nerve pathway to the hypothalamus, resulting in ovulation approximately 36 hours later – known as induced ovulation. The os penis lies ventral to the urethra in the cat. During sexual excitement, the penis engorges and points cranioventrally so that the mating position in cats is similar to that seen in the dog.
Accessory glands
The function of the accessory glands is to secrete seminal fluids which:
There are two types of gland (Figs 11.1, 11.2):
Female reproductive system

Fig. 11.6 Dorsal view of the reproductive system of the bitch.
(With permission from Colville T, Bassett JM 2001 Clinical anatomy and physiology for veterinary technicians. Mosby, St Louis, MO, p 330.)
The ovary
The ovary is the female gonad. The functions of the ovary are:
There is a pair of ovaries, one lying on each side of the dorsal abdominal cavity, caudal to the kidney (see Ch. 10, Fig. 10.2). The ovary is held close to the kidney by the ovarian (suspensory) ligament (Fig. 11.7). The ovary is suspended from the dorsal body wall by part of the visceral peritoneum called the mesovarium, which also encloses the infundibulum of the uterine tube. Part of the mesovarium forms a pocket-like structure known as the ovarian bursa, which completely covers the ovary. Within this is a small opening allowing ova to leave the ovary – this is a potential means of entry of infection into the peritoneal cavity.
The uterus
The uterus is a Y-shaped structure lying in the midline of the dorsal abdomen (Fig. 11.6). During pregnancy, the weight of the conceptuses pulls the uterus ventrally and at full term it occupies the greater part of the abdomen. The function of the uterus is:
The wall of the uterus has three layers:
The cervix
The vulva
The vulva marks the external opening of the urogenital tract. It consists of two parts:
The mammary glands
Lactation
Composition of milk
Table 11.1 Average composition of milk
Constituent | Quantity (%) |
---|---|
Water | 70–90 |
Fat | 0–30 |
Protein | 1–15 |
Carbohydrate | 3–7 |
Minerals | 1.5–1: calcium phosphate, magnesium, sodium, potassium and chlorideMilk is deficient in iron and copper; traces of iodine, cobalt, tin and silica are present |
Vitamins | A, B2, B5, E, KMilk is low in vitamins C and D |
NB. Milk from a cat contains the amino acid taurine, as cats have a specific requirement for this.
The oestrous cycle
The oestrous cycle is the rhythmic cycle of events that occurs in sexually mature non-pregnant female mammals and includes limited periods of sexual receptivity known as oestrus. The function of the oestrous cycle is:
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