Part 3: Female Genitalia

In intact FEMALE specimens, within the abdominal cavity, identify the uterus and ovaries. The uterus is made up of the uterine horns, body, and cervix. The uterine horns are located caudal to the kidneys. They extend caudally to their unification at the body of the uterus. The cervix of the uterus is found ventral to the descending part of the colon in the caudal part of the abdominal cavity. In non-pregnant animals, the uterus is quite small, but a pregnant uterus can be very distended and may alter the position of other organs within the abdominal cavity. (See DG Figs. 4-9B, 4-12, and 4-24)

• Identify all parts of the uterus: uterine horns, body, and cervix.

  Related Learning Objectives

  • D6.5
  • D6.6

   

• The two, long uterine horns are the most notable and recognizable parts of the uterus; there will be one horn on the left side and one horn on the right side.

  • • Traveling along each uterine horn, identify the uterine a.

• Where the two uterine horns unite, they create the body of the uterus. The body is quite short in comparison to the horns. (See DG Figs. 4-12 and 4-24)

• From the body, as you move caudally, you will encounter the cervix. The cervix is seen as a short, firm enlargement as you move caudally into the pelvic inlet. There is a palpable difference at the transition of the uterine body to the cervix. (See DG Fig. 4-24)

  Related Learning Objective

  • D6.5

   

Identify the ovaries (left & right) (See DG Figs. 4-9B, 4-12, 4-24, and 4-25) The ovaries lie near the caudal pole of each kidney.

• Note that each ovary is enclosed in a thin-walled peritoneal sac called the ovarian bursa. There is a slit-like opening where the bursa is open to the peritoneal cavity on the medial surface. (See DG Fig. 4-25, B, C, & D)

• On the exterior of the sac/bursa look for and identify the uterine tube which is a small, cord-like thickening in the wall of the bursa traveling from the ovary to the uterine horn. The uterine tube carries oocytes to the uterine horn (or if fertilization has occurred carries the zygote to the uterine horn). (See DG Fig. 4-24, and 4-25, A, B, & C)

  • • On the lateral side of the ovary/ovarian bursa, dorsal to the uterine tube, make a small incision into the ovarian bursa to observe the ovary and the infundibulum. The infundibulum is the dilated ovarian end of the uterine tube and has a fimbriated margin to help engulf the oocyte post-ovulation. (See DG. Fig. 4-25B)

    • Attempt to trace the uterine tube to its connection with the uterine horn which is called the tuberouterine junction. (See DG Fig.4-25B, “tubouterine junction”)

• Identify the proper ligament of the ovary connecting the ovary to the cranial end of the uterine horn. (See DG Figs. 4-24, and 4-25A)

• Look for, and identify, the ovarian a. and associated ovarian v.

  • • Comment: Note that clinically, the ‘pedicle’ referred to in a spay (OVH) procedure is the stump left behind when the ovarian vessels are tied off and transected.

Re-identify the ovarian arteries (female) (left & right) branching from the aorta, which were previously dissected in Chapter 5. Attempt to trace at least one of the ovarian aa. to the respective left or right ovary (if present). (See DG Figs. 4-12 and 4-28)

• Dissection Note: The ovarian arteries may be small and easily broken, so dissect with care. (See DG Figs. 4-12, 4-28, 4-29, and 4-31)

• As previously mentioned, note the ovarian veins that satellite these arteries.

The female’s internal genitalia are suspended from the dorsal body wall by peritoneal folds on each side of the body; these are the broad ligaments of the uterus. Identify the broad ligament of the uterus on both left and right sides. (See DG Fig. 4-12, and 4-25D) Each broad ligament is divided into three parts: mesovarium, mesosalpinx, and mesometrium. (See DG Fig. 4-25A) Identify these components and their associated structures listed below:

• The mesometrium is found attaching to the cranial end of the vagina as well as the cervix, uterine body, and uterine horn.

  • • Note the fold from the lateral side of the mesometrium whose free border makes up the round ligament of the uterus. The round ligament of the uterus passes through the inguinal canal and has no function in the adult female animal. (See DG Fig. 4-12, and 4-25A)

• The mesovarium is a continuation of the mesometrium and is the cranial portion of the broad ligament attaching to the ovary. (See DG Fig. 4-25, A & D)

  Related Learning Objective

  • D6.5

   

  • • Identify the suspensory ligament of the ovary extending from the cranial end of the ovary/mesovarium to the body wall. This ligament holds the ovary in a relatively fixed position and must be broken down in a spay procedure to remove the ovary. (See DG Figs. 4-12, 4-24, and 4-25A)

• The mesosalpinx attaches the uterine tube to the mesovarium and helps form the wall of the ovarian bursa mentioned previously. (See DG Figs. 4-24 and 4-25A)

Caudoventrally, inside the peritoneal cavity, observe the region of the vaginal ring and identify the deep inguinal ring. (See DG Figs. 4-5, 4-11, and 4-43)

• Dissection Note: The vaginal ring is the opening formed by the parietal peritoneum as it leaves the abdomen and enters the inguinal canal to form the vaginal tunic/process. An accumulation of some amount of fat usually surrounds the vaginal ring region.

• The vaginal ring marks the position of the deep inguinal ring, which is formed by the reflection of transversalis fascia outside the vaginal ring. The deep inguinal ring represents the entrance to the inguinal canal.

Re-identify the round ligament of the uterus inside the abdominal cavity before it passes through the inguinal canal.

Review the concept of the inguinal canal (which the external pudendal vessels and genitofemoral nerve pass through) that was previously discussed in Chapter 3; note that this canal is a ‘passageway’ and not a distinct ‘structure’.

• The inguinal canal is a ‘slit’ between the abdominal muscles that forms a very short, natural passageway through the abdominal wall. It extends from the deep inguinal ring (inside the abdomen) to the superficial inguinal ring (outside the abdominal wall) and allows passage of various structures. These structures include the external pudendal a. and v., genitofemoral nerve, vaginal tunics, and spermatic cord (male) or vaginal process (female). (See DG Figs. 2-80 and 4-5)

If possible, re-identify the vaginal process (previously identified in Chapter 3). It is found passing out of the inguinal canal through the superficial inguinal ring. The vaginal process in the female envelops the round ligament of the uterus and a varying amount of fat. It may vary in appearance in each specimen (short, long, a lot of fat, only a little fat, etc.). (See DG Figs. 4-2 and 4-4)

Re-identify the ureters (left and right) (previously identified in Chapter 5) and trace them to the urinary bladder. Within the pelvis, identify the urethra leaving the neck of the bladder. Attempt to identify the striated urethral m. (urethralis m.) surrounding the pelvic urethra. (Note that the urethralis m. may also be referred to as the external urethral sphincter.)(See DG Figs. 4-38 and 4-39)

• Make a mid-ventral incision through the wall of the urinary bladder and the urethra.

• Open the urinary bladder and observe the entrance of the ureters into the bladder; identify the trigone of the bladder. The trigone of the bladder is the dorsal triangular area located between the ureteral openings and the urethral exit from the bladder. (See DG Fig. 4-42B)

Identify the vagina, vestibule, and vulva. (See DG Figs. 4-24 and 4-52)

• The vagina is the cavity located between the cervix and the vestibule.(See DG Figs. 4-24 and 4-52) Note that the most cranial part of the vagina is called the fornix. (See DG Fig. 4-52)

• The vestibule is the cavity extending from the vagina to the vulva. (See DG Figs. 4-24 and 4-52)

• The vulva contributes to the external opening of the female urogenital tract. (See DG Fig. 4-52)

  • • The vulva is composed of two labia that come together and fuse dorsally and ventrally at the dorsal & ventral commissures respectively. Identify these structures on your specimens.

Open the vestibule and vagina with a dorsal midline incision, similar to DG Fig. 4-52. View the interior and identify the vagina and vestibule. (Note that the fornix may be difficult to see so it need not be identified.)