Camelid Female Anatomy - Anatomy & Physiology

Ovary

• Located ~36 cm from the opening of the vulva but are subject to great variations depending on the physiological stage.
  • For example, during pregnancy they becomes more ventral and are pulled forward during the advancing stages thus making them very difficult to palpate.
• The left ovary is generally more cranio-ventral in postion than the right ovary.
• The ovary is attached to the broad ligament by a well-defined strong ligament which extends from the hilus of the ovary to the tip of the corresponding uterine horn.
• Both ovaries are enclosed within a fold of the mesosalpinx known as the ovarian bursa, the apex of this bursa forms a large circular orifice within which lies the fimbriae of the oviduct.
• Their general appearance and size varies according to the age and activity of the animal.
  • In the prepubertal animals they have a smooth and glistening surface with several raised small vesicles (2 - 5 mm in diameter) throughout the surface which correspond to the follicles.
  • In anoestrous females the ovaries are oval or circular, flattened laterally and have an irregular surface due to many small follicles.
  • During the breeding season, mature follicles and current corpora lutea (CL) project from the main contour of the ovary and give it a more lobular form.
    • This lobulation increases with increased number of previous ovulations or pregnancies and is due mainly to the presence of old corpora albicantia.

Ovarian Structures

• The ovary consists of two major parts
  • Cortex
  • Medulla
• Whole organ is enclosed by a tunica albuginea except in the area of the hilus.
• Follicular activity takes place in the cortex and ovulation can occur anywhere on this surface.
• However, as camelids are induced ovulators (only ovulate in response to mating) there is no cyclical appearance of a CL in non-mated females.
• Corpora lutea are only present in the ovaries of recently bred or pregnant females.

Follicles

• Follicular activity is dominated by 4 types of follicles
  • Small growing follicles
  • Mature follicles
  • Regressing follicles
  • Over-large, anovulatory follicles
• As the follicular waves overlap with each other, several generations of follicles may be present at the same time.
• The small growing follicles are visible on the surface of the ovary as small slightly raised vesicles measuring between 2 - 4 mm, whereas the mature pre-ovulatory follicle measures between 13 - 20 mm [19,20] and is spherical, turgid, with a thin clear translucent wall and protrudes markedly from the ovarian surface.
• The appearance of regressing follicles depends on the stage of regression.
  • At the start of regression the follicular wall becomes thick and opaque and the diameter decreases slowly until the follicle recedes into the ovary itself.
  • Large anovulatory follicles are present in about 50% of non-mated females and their size and appearance can be highly variable.
    • They vary in size from 25 - 60 mm and may have a thin or thick, opaque wall and contain either serous or haemorrhagic fluid with various amounts of fibrin.

Corpus Luteum

• Forms after ovulation, which occurs 24 - 48 hours after mating.
• The ovulating follicle collapses at ovulation and then the follicular cavity fills with blood to form a corpus haemorrhagicum.
• Luteinization of the corpus haemorrhagicum occurs within 4 - 5 days and gives rise to a corpus luteum.
• Regression of the CL occurs between 10 - 12 days after a sterile mating or just before parturition in the pregnant female.
• The corpus albicans, originating from the regression of the CL of pregnancy is hard, white or grey in colour and has no blood vessels on its surface. Corpora albicantia of different sizes (5 - 12 mm in diameter) can remain on the surface of the ovary of the female for a long time.

Oviduct

As in other mammalian species the oviducts play an important role in storage of sperm, fertilization and early embryonic development. Unlike other mammals though the oviducts are enlarged at the uterine end and this unique arrangement allows prolonged storage of large numbers of spermatozoa.

• The oviducts measure between 17 - 28 cm in length.
• The isthmus is less coiled than the ampulla, and the fimbria lies within the bursa at a short distance from the ovary.
• Each oviduct opens into the uterine horn via papillae.
  • Very muscular with a sphincter.

Uterus

• Y-shaped bicornuate uterus.
• Almost all pregnancies carried in the left Uterine Horn, which is longer than the right.
• Ova shed from the right ovary must migrate down the right Uterine Horn to the Uterine Body and up the left Uterine Horn in order to establish pregnancy.
• In immature females the uterus is very small and can be found entirely within the pelvic cavity, whereas in mature non-pregnant females it is located in the abdominal cavity at the level of the 5th, 6th and 7th lumbar vertebra.
• The endometrium of the uterine body and horns contain no caruncles and the uterine glands are simple, branched and tubular.
• In the gravid uterus the left uterine horn, in which the fetus implants, becomes noticeably distended at around 1.5 months of pregnancy and is almost double its size by 2 months at which time the uterus hangs into the abdominal cavity.
• By 150 days the diameters of the gravid and non-gravid horns are nearly 4 times their original sizes.
• Endometrium increases in size and the glands become more numerous.
• The non-involuted post-partum uterus hangs over the brim of the pelvis. The uterine wall is thickened, oedematous and in the early postpartum period the uterus contains a small amount of old blood.
• The uterus returns to its normal non-pregnant position between 20 - 45 days after parturition.

Cervix

• Contains annular muscosal folds but its consistency does not differ significantly from that of the uterus, unlike that of cattle, which makes it very difficult to identify by rectal palpation.
• The cervix protrudes caudally in the vaginal cavity forming a fornix.
• The size of the protruded vaginal portion of the cervix and the actual position within the vaginal cavity varies between individuals and the appearance of the external cervical os varies according to the stage of the cycle.
  • In the presence of a mature follicle the cervix is contracted and oedematous and appears open on vaginal examination.
  • During the luteal phase, it becomes dry and the cervical os is usually covered by a flap of the last two cervical rings.
  • During pregnancy the cervix becomes very tight and in the advanced stages the cervix is pulled forward and downward beyond the pelvic brim.
  • The normal size and position of the cervix is regained within the first two weeks following parturition.

Vagina

• 25-35 cm in length
• Lined with many longitudinal folds.
• The anterior vagina and the vestibulum are separated by a strong band of tissue (vestibulum sphincter muscle) and the hymen.

Hymen

• Membrane 3-4cm thick
• Persists from embryonic development in maiden females.
• Tough to break down, some males may fail to achieve it.
  • Mating will stimulate ovulation and subsequent rejection of the male by the female but no pregnancy.
  • May require assistance to break the hymen of maiden females using a sterile-gloved finger.

Vulva

• Opens directly below the anus.
• 6 - 7 cm in length
• During the follicular phase oedema of the vulva can be present but it is very discrete.
• During the last week prepartum it becomes much more relaxed and oedematous.
• The clitoris is very small and there is no distinct clitoral fossa.