22 Anatomy of the Reproductive System of the Cow
Ben Nabors
Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, USA
Introduction
The anatomy of the reproductive system in the cow is functionally grouped into the components associated with oocyte production and transport and those involved with gestation and copulation.
Production
The cellular machinery for oogenesis and steroid production is found in the ovary (Figure 22.1). The ovary consists of a cortex and medulla. The medulla is composed of connective tissue, lymphatic vessels, blood vessels, and nerves. Surrounding the medulla is the cortex. The cortex contains the ova surrounded by follicular cells within the connective tissue stroma [1]. Exterior to the cortex, the ovary is covered by the dense fibrous tunica albuginea and a superficial epithelium [2].
Figure 22.1 (a) Ov, ovary, Uh, uterine horn, F, follicle, 22.1 (b) Corpus luteum, Image courtesy Dr. Fuller Bazer, Texas A & M, (c) Corpus lutea (image from pregnant cow), Image courtesy Dr. John Roberts, College of Veterinary Medicine, University of Florida.
Because the ovary in the cow descends further from its embryologic origin near the kidney than other species, it is positioned closer to the pelvis. The consequence of this ovarian location and the attachment of the short mesovarium is that the uterine horns bend ventrally and caudally [3] (Figure 22.2). (Editor's note: for additional histological images of the ovary see Chapter 25.)
Figure 22.2 The internal reproductive tract from oblique angle. V, Vagina; C, cervix; Uh, uterine horn; Ov, ovary; Ub, urinary bladder.
Transport and Gestation
The reproductive system of the cow is designed to transport spermatozoa toward the ovary and to transport an ovum toward the spermatozoa (Figure 22.3). The parts of this tubular system include the vestibule, vagina, cervix, uterine horns, and uterine tubes (oviduct).
Figure 22.3 The internal reproductive tract from dorsal view. V, Vagina; C, cervix; U, uterus body; Ov, ovary; Uh, uterine horn.
Uterine Tube
The uterine tube is arranged like a funnel near the ovary. The funnel‐shaped end, or infundibulum, contains processes, the fimbriae, which collect the ovum on ovulation (Figure 22.4). The ovum is then transported through the abdominal opening of the uterine tube located at the base of the infundibulum [4]. The ampulla of the uterine tube is the region adjacent to the infundibulum where fertilization takes place. The isthmus, the continuation of the uterine tube from the ampulla toward the uterus, is relatively long due to the meandering course it takes before ending at the uterine opening where it releases the ovum into the uterine horn [4].
Figure 22.4 Structures of the ovary. Ov, Ovary; Inf, infundibulum; Ut, uterine tube; Ovb, ovarian bursa; Uh, uterine horn.
Uterus
The uterus consists of a body and two horns (Figure 22.5). The body is short, beginning immediately after the cervix ends. The horns branch from the body but are joined together by the peritoneum, giving the appearance that the body is longer than it truly is. As the horns progress craniad they divide at the intercornual ligaments, each turning abruptly ventrally, then proceeding caudally, and finally ending dorsal to the ovary [3] (Figure 22.6).
Figure 22.5 Dorsal view of reproductive tract. U, Uterus body; Ov, ovary; Uh, uterine horn.
Figure 22.6 Uterine horns positioned to better view the intercornual ligament. Uh, Uterine horn; Dl, dorsal intercornual ligament; Vl, ventral intercornual ligament; Ovb, ovarian bursa; Ov, ovary.
From external to internal, the uterus can be divided into three layers: the perimetrium, the myometrium, and the endometrium [3]. The perimetrium is the continuation of the abdominal peritoneum onto the uterus. The myometrium constitutes the muscular layers, which can undergo substantial hypertrophy [5]. The endometrium is the internal epithelial lining of the uterus and is arranged into two distinct regions, caruncular and intercaruncular [6]. The caruncles are raised mucosal regions of the endometrium that are highly vascularized (Figure 22.7). The caruncles of the uterus join with the cotyledons of the fetal placental membranes to form the placentomes of a cotyledonary placenta [4].
Figure 22.7 The uterine lumen. Pm, Perimetrium; Mm, myometrium; Em, endometrium; Cr, caruncle.
Cervix
The cervix is located between the body of the uterus cranially and the vagina caudally (Figure 22.8). It is a firm, muscular, sphincter‐like structure that acts as a barrier separating the external genitalia from the internal genitalia [5]. Characteristic of the cervix are the three to four circular folds projecting into its lumen.
