ANS 3319C Reproductive Physiology and Endocrinology Lab Female Reproductive Anatomy Objectives 1. To introduce the gross anatomy of the reproductive tracts of the cow, sow, and mare. 2. To dissect the reproductive tracts of the mare, sow, and cow. 3. To develop an understanding of the functional significance of the anatomical parts of the reproductive tract and how these parts function as a unit.

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Please refer to the course textbook “Pathways to Parturition and Pregnancy” to view the figures cited in this handout. The figure numbers correspond with figure numbers found in the textbook. The figures can also be found on the lab web page as part of this handout.

Gross anatomy – general terminology 1. External genitalia  Vulva, Clitoris, Dorsal and Ventral Commissures, Perineum, Anus, Vestibule 2. Internal structures  Vestibule, Urethra, Vagina, Urethra, Bladder, Cervix, Uterus (body/horns), Oviduct, Ovary, Broad ligament

External Genitalia (Figures 2-23, 2-24)

1. Vulva Consist of the labia majora and labia minora. Provides anatomical closure to vagina so as to minimize entry of foreign material into vagina. 2. Commissures Dorsal and ventral are the sites of the union of the labia. 3. Perineum Area surrounding the vulva and anus. Can be torn during a difficult parturition. 4. Clitoris Highly innervated tissue (homologous to glans penis) located in the ventral commissure that is very sensitive to tactile stimulation. Serves to control copulation in some species. 5. Vestibule Common duct for urine and fetus during parturition. Also functions to stimulate penis during copulation. 

Suburethral diverticulum (also called blind pouch) Sac-like structure in cow and sow, which lies ventral to urethral opening. No know function.

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Urethral tubercle Bulb-like structure directly above urethral opening that protrudes into vestibule in the bitch. No know function.

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Vestigial glands (also called the Bartholin glands) Glands located along walls of vestibule and responsible for viscous vaginal secretions to provide lubrication during estrus. Additionally, they produce chemicals called “pheromones”, which declare to the male that the female is in estrus.

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Vulvo-vaginal sphincter muscle Muscle contracts to block urine from entering the uterus.

Internal Reproductive Tract (Figures 2-4, 2-5, 2-6, 2-7, 2-8) 1. Broad Ligament Double layer of connective tissue that originates from the peritoneum. 

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Functions: 

Supports and suspends the ovaries, oviduct, uterus, cervix, and anterior vagina.

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Houses the vascular, lymphatic drainage, and nerve supplies.

Structural characteristics 

Mesoovarium Houses vascular supply, lymphatics, and nerves to ovary 

Forms hilus or attachment to ovary

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Mesosalpinx Thin tissue that supports the oviduct and helps orient infundibulum around ovary to direct oocytes into oviduct. In the bitch, the mesosalpinx encloses the ovary forming a bursa around the ovary.

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Mesometrium The largest part of the broad ligament that supports the uterine horns and (or) uterine body. It is continuous with the dorsal peritoneum and hangs from the dorsal body wall.

ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

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2. Vagina 

Functions 

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Structural Characteristics: 

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Copulatory organ during natural mating in most species & serves as birth canal during parturition. Highly acidic environment, which functions to prevent bacterial infection. 

Microflora: aerobic and facultative anaerobic.

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The low pH (5.7) creates an unfavorable to the spermatozoa.

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Provides lubrication via mucous secretions and asserts pressure on the penis to stimulate ejaculation during mating is some species.

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Stimulates the bull’s penis directly via temperature.

Histological Composition: 

Poorly defined muscular layer but a well developed and highly adapted mucosal layer composed of epithelium, which changes in thickness depending on the endocrine environment as the animal progresses through the estrous cycle. 

Cranial: high degree of secretory activity during estrus, composed of columnar epithelium

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Caudal: characterized as having stratified squamous epithelium that serves to physically protect vagina during copulation & prevents bacteria from getting into submucosa.

3. Fornix Vagina Protrusion of cervix into anterior vagina in cow, mare, ewe, and bitch. 

Functions 

Site of semen deposition during natural mating in cow, ewe, cat, dog. 

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In mare, fornix vagina is flexible & slightly open. During mating the stallion’s penis presses against it and semen is actually forced into cervix and flows into uterus.

Secretes copious amounts of mucous during estrus in some species.

4. Cervix is a sphincter-like structure (Figure 2-20) 

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Functions 

Site of semen deposition in sow during natural mating. The cervix is composed of interdigitating pads that lock onto boars penis, apply pressure, and stimulate ejaculation.

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Site of semen deposition in mare during natural mating and semen flows into uterus.

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Site of semen deposition during artificial insemination in dog, pig, sheep

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Serves as sperm reservoir in some species and assist in transporting sperm from cranial end of the cervix to uterine lumen.

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Production of mucus in cow and ewe, but to a lesser extent in sow and mare

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Sealed during pregnancy with a “glue-like” substance to serve as barrier to uterus in most species.

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Serves as a birth canal during parturition

Structural Characteristics: 

Fibrous, collagenous, thick-walled organ with a small amount of muscle with a constricted lumen.

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Contains either single/multiple folds or rings: 

Sow: interlocking digital pads that hold the boar’s corkscrew penis during copulation.

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Ewe/cow: prominent ridges that are close together.

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Mare: loose folds that protrude into uterus.

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Bitch/Queen: smooth cervix with no folds or rings.

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Cervical mucous (mucin macromolecules) is formed from epithelial origins within the annular rings. Facilitates transport of the sperm, serves as a sperm reservoir, and may play a role in the selectivity of viable sperm to enter the uterine lumen.

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During anestrous, the cervix is tight due to lack of stimulation from estrogen.

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During estrus, mucous is discharged from cervix and expelled from vulva.

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During pregnancy, the cervix acts as a barrier against sperm transport and bacterial invasion to prevent infection.

ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

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In late gestation and during parturition, the cervical plug liquefies. The amount of collagen present decreases and the cervix begins to dilate, which is due to hormones such as estrogen, relaxin, and prostaglandin F2. The final step is parturition and fetal expulsion from the uterus).

Histological Composition: 

Dense connective tissue with small amount of myofibrils (muscle tissue).

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Some epithelial tissue, which secretes mucous.

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Little vascularization.

5. Uterus consists of the body and two horns. The uterus is composed of three separate layers, which are suspended by the broad ligament. Additionally, the vasculature of the uterus comes from the attached broad ligament. (Figures 2-5, 2-7, 2-9, 2-13, 2-17, 2-24) 

Major Functions: 

Sperm Transport Estrogen from the ovaries stimulates myometrial contractions to assist in sperm transport toward oviducts when female is in estrus. During transportation the sperm is also capacitated to get it ready for fertilization.

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Regulation of Corpus Luteum (CL) Uterine glands secretes prostaglandin F2 (PG F2), which functions to destroys the CL to regulate the estrous cycle.

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Embryo Development & Placental attachment Provides early developing embryo the proper nutrition via its abundant endometrial vasculature. Eventually, placental attachment or placental invasion occurs and functions to provide an interface between the maternal and fetal circulations allowing for nutrient and gas exchange necessary for fetal growth and development

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Parturition and Post-Partum Involution Increased myometrial contractions assist in expulsion of the fetus during parturition. After parturition, the uterus goes through a process called involution, which allows the uterus to return to its original size and prepare itself for the next pregnancy.

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Semen deposition during artificial insemination: cow, mare, cat, sheep, goat, dog (sometimes)

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Structural Characteristics and Histology:

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Uterine body is fused between the end of the cervix and the base of the uterine horns.

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Uterine horns are two elongated structures located between the oviducts and the uterine body.

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Types: 

Bicornuate: two horns associated with the body. Cow & mare have poorly developed horns; whereas, ewe, sow, queen, & bitch have highly developed uterine horns.

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Simplex: large body with virtually no uterine horns (humans, primates).

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Duplex: two cervical canals separate each horn into distinct sections (marsupials, rabbits).

Histology: (three major tissue layers) 

Perimetrium Outer serous (serosa) layer composed mainly of connective tissue.

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Myometrium Middle smooth muscle layer responsible for contraction during estrus to allow for sperm transport & during parturition to expel the fetus.

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Under the influence of estrogen the uterus has tone (turgidity and hardness), which is distinguished from the soft and flaccid uterus under the influence of progesterone.

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During the parturition process, the myometrium is major driving force for expulsion of fetus and eventually the placental membranes.

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Sympathetic nerves penetrate the myometrium and endometrium. The source of vasculature comes through the broad ligament.

Endometrium Consist of inner mucosal epithelial layer that vascularizes during estrus and grows a delicate mucous membrane lining during pregnancy. 

Mucosal layer secretes material from its glands into lumen that enhance embryo development and sperm survival. It also secretes prostaglandin F2 in the absence of an embryo that lysis the corpus luteum. This layer is sloughed-off in primates and humans but not lower mammals.

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Submucosal layer consist of connective/supporting tissues that houses the glands.

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In the cow and ewe, small protuberances from endometrial surface called caruncles are important in placental attachment. Sow and mare have endometrial folds.

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6. Oviducts (salpinges or fallopian tubes) Small tubes that extend from the uterine horns to ovaries, which are suspended in the peritoneal fold that is derived from the broad ligament. The infundibulum is also part of the oviduct (Figures 2-13, 2-13, 2-14). 

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Functions 

Transport sperm and oocytes via smooth muscle contractions to the site of fertilization.

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Acts to reduce sperm numbers to prevent polyspermy.

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Removes oocytes from the surface of the ovary via cilia called fimbria on infundibulum.

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Provides proper environment necessary for the oocyte(s) and the early developing embryo.

Structural Characteristics 

Utero-tubal junction has no distinct sphincter muscle, but the musculature does exist and increases in thickness from the distal end towards the proximal end. This section controls the number of sperm that enter the oviduct from the uterus in some species.

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Isthmus proximal ½ of oviduct connected to uterus consisting of a thick muscular wall with few mucosal folds. Transports sperm from uterus to ampulla by muscle contractions.

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Ampullary-isthmic junction - site of fertilization and cleavage of embryos. 

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Mare control point that only allows fertilized oocytes to pass to isthmus.

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Ampulla distal ½ of oviduct consisting of a thin muscular wall with numerous mucosal folds with ciliated epithelium that beat towards the uterus.

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Ostium opening into ampulla

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Infundibulum funnel shaped structure surrounding ovary that captures oocytes.

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Fimbria ciliated structures on infundibulum that massage the ovarian surface to catch/grab the oocyte(s) being ovulated from ovary.

Histology: 

Serosa layer outer layer that is composed of connective tissue.

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Muscularis layer middle smooth muscle layer.

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Longitudinal fibers function to shorten oviduct.

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Circular fibers provide annular constriction.

Mucosa layer inner tubal layer, lined with: 

Ciliated columnar epithelium (provides motion).

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Secretory cells (goblet cells - secrete mucous).

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Nonsecretory cells.

7. Ovary Primarily supported by the broad ligament in the peritoneal cavity. Function is controlled by the pituitary hormones FSH and LH. The ovarian structures are highly complex and perform a variety of functions during the lifespan of the female. (See Estrous Cycle diagrams below) 

Functions: 

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Hormone production 

Estrogen from the ovarian follicles, which functions to bring female into behavioral estrus.

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Progesterone from corpus luteum (CL), which is tissue derived from the ovulated follicle. The progesterone prepares the uterus for pregnancy and serves to maintain pregnancy.

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Oxytocin, relaxin, activin are also produced by the ovary but with species differences.

Gamete production 

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Development, maturation and ovulation of oocyte(s) with each estrous cycle.

Structural characteristics: 

Tunica albuginea Outer dense, connective tissue layer, which is continuous with the peritoneal lining. Consist of a single layer of cuboidal epithelial cells called the germinal epithelium, which serve to prevent adhesions and is broken at ovulation.

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Cortex Zone of ovary that houses oocytes except in the mare. 

Corpus hemmorrhagicum (bloody body) Blood filled cavity where follicle ovulated.

ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

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Corpus luteum (yellow body) Forms in cavity left by ovulated follicle. Produces progesterone, the hormone of pregnancy and oxytocin in ruminant.

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Corpus albicans (white body) Regressed CL on surface of ovary with no function.

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Medulla: Contains blood vessels, connective tissue, lymphatics, and nerves.

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Specific Notes: 

Mare ovarian medulla and cortex are reversed (cortex inside, medulla outside). Ovulation occurs at a single location on the ovary called the ovulation fossa. The follicle can be palpated but the resultant CL cannot since it develops in the cortex. The mare typically has one ovulation and is known as a monotocous species.

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Cow typically has one ovulation and is known as a monotocous species.

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Bitch, ewe, queen, & sow have multiple ovulations; hence, multiple CL and are known as polytocous species.

Histological stages of the oocyte development Several stages of development occur before a mature oocyte is released into the oviduct known as folliculogenesis. 

Primordial follicles (2n chromosome) most immature follicle found in the ovarian cortex.

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Primary follicle Germ cell (2n) surrounded by a single layer of granulosa cells; largest cell in the body (180 um). A young calf may have 75,000 primary follicles in groups called “egg nests” at birth. Humans and primates are the primary species than “run-out” of follicles to ovulate during their lifetime

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Secondary follicle (n) Majority of the follicles are in this stage (resting/storage) and they contain two or more layers of granulosa cells.

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Tertiary follicle (n) fluid filled follicle visible on surface of the ovary in most species. 

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Typically have an antrum, which is a fluid filled cavity.

Graafian follicle (n) - A mature tertiary follicle that produces estrogen. 

Appears as a blister on the surface of the ovary with a fluid filled antrum.

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Size is species dependent: 

Ewe, sow, bitch, queen: 3 - 10 mm.

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Cow:15 - 20mm.

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Mare: 30 - 50 mm.

Note on ovarian development

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Several stages of follicle development as well as the presence or absence of a corpus hemmorrhagicum, corpus luteum, and corpus albicans can be observed on the ovary at any point and time during the estrous cycle. The structures present on the ovary are dependent on the stage of the estrous cycle that the animal is in at that point in time. Therefore, it is important that you learn the morphological and physiological similarities and differences in ovarian development across the species at different stages of the estrous cycle (See Figs. A & B).

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For most mammalian species, follicles grow in a wave like pattern during the estrous cycle. Follicles go through a recruitment, selection, dominance phase during the growth of the follicle. At the dominance phase, the follicle can either go through atresia (presence of high progesterone) or ovulation (absence of high progesterone). (See Fig. C)

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Growth and development of follicles & luteal structures (CL) change over the duration of the estrous cycle. The amount of estrogen and progesterone secreted by follicles and CLs are closely tied to the development of follicles and luteal structures. The estrous cycle diagram below shows the variation in concentrations of estrogen and progesterone (See Fig. D). In addition, the types of estrous cycles, length of the estrous cycle, and length of behavioral estrus is different across species (See Table 1).

ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure A. Diagrammatic representation of ovarian structures. The diagram shows the development from a

primordial follicle to an antral follicle that ovulates to form a coprpus hemorrhagicum (Not shown) and eventually a corpus luteum and eventually a corpus albican.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Species

Early Metestrus

Diestrus

Proestrus

Cow

Sow

Mare

Figure B. Ovarian Structures. Photographs of the ovaries at three different stages of the estrous cycle in the cow,

sow, and mare. Early metestrus – note the coprpus hemorrhagicum (CH) present on the ovarian cross sections of all species. Diestrus – note the presence of a fully developed corpus luteum (CL) in the cow and sow and multiple CLs in the sow. Proestrus – note the decrease CL size and color (decreased vascularity) of the regressing CL and also the presence of newly developed dominant follicle in the cow and numerous follicles in the sow. Estrus occurs after the proestrus phase and is the period of sexual receptivity of the females for the male.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure C. Follicle development occurs in wave like patterns during the estrous cycle in the bovine and numerous other mammalian species.

Figure D. Stages of the estrous cycle and progesterone and estrogen concentrations in the bovine. Follicle phase consist of proestrus and estrus and the luteal phase consist of metestrus and diestrus.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Table 1. Characteristics of estrous cycles in domestic animals Length of estrous cycle

Duration of estrus

Time from LH surge to ovulation

Species

Classification

Mean

Range

Mean

Range

Time from onset of estrus to ovulation

Cow

Polyestrus

21 d

(17-24 d)

15 h

(6-24 h)

24-32 h

28 h

Ewe

Seasonally Polyestrus

17 d

(13-19 d)

30 h

(18-48 h)

24-30 h

26 h

(Short day) Sow

Polyestrus

21 d

(17-25 d)

50 h

(19-96 h)

36-44 h

40 h

Mare

Seasonally Polyestrus

21 d

(15-26 d)

7d

(2-12 d)

5d

2d

(Long day) Bitch

Monoestrus

6 mo

(3-9 mo)

9d

(4-21 d)

4-24 d

2-3 d

Queen

Polyestrus

17 d

(4-30 d)

9d

(2-19 d)

Induced ovulator

30-40 h

Llama

Polyestrus

10 d

(8-12 d)

5d

(4-5 d)

Induced ovulator

26-36 h

Alpaca

Polyestrus

15 d

(11-18 d)

5d

(4-5 d)

Induced ovulator

26-36 h

 Definition of the types of estrous cycles for Table 1 

Polyestrus (cattle, swine, rodents, domestic cats) 

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Uniform & regular estrous cycles throughout year

Seasonally polyestrus (sheep, goats, horses, deer, elk, wild cats) 

Clusters of estrous cycles only during certain season of year

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Short-day breeders (sheep, goats, elk, deer) 

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Long-day breeder (horses, wild cats) 

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Began estrous cycles w/  day length

Began estrous cycles w/  day length

Monoestrus (dogs, wolves, fox, bear) 

One estrous cycle per year

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Domestic canine: typically 3 estrous cycles in two year period

Induced ovulation: the process of mating initiates the process of ovulation

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

A

B

Reproductive Anatomy of the cow. A) Figure 2-23 External genitalia: A = Anus; CB = Cutaneous Bridge; DC = Dorsal Commissure; VC = Commissure; RL = Right Labis; LL = Left labia. B) Figure 2-4 Internal reproductive structures.

A

B

Reproductive Anatomy of the sow. A) Figure 2-23 External genitalia: A = Anus; CB = Cutaneous Bridge; DC = Dorsal Commissure; VC = Ventral Commissure; RL = Right Labia; LL = Left labia. B) Figure 2-6 Internal reproductive structures.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

A

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B

Reproductive Anatomy of the Mare. A) Figure 2-23 External genitalia: A = Anus; CB = Cutaneous Bridge; DC = Dorsal Commissure; VC = Ventral Commissure; RL = Right Labia; LL = Left labia. B) Figure 2-6. Internal reproductive structures.

A

B

Reproductive Anatomy of the Bitch. A) Figure 2-24 External genitalia: A = Anus; CB = Cutaneous Bridge; DC = Dorsal Commissure; VC = Ventral Commissure; RL = Right Labia; LL = Left labia. B) Figure 2-8 Internal reproductive structures.

ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

A

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B

Reproductive anatomy of the queen. A) Figure 2-24 External genitalia: A = Anus; CB = Cutaneous Bridge; DC = Dorsal Commissure; VC = Ventral Commissure; RL = Right Labia; LL = Left labia. B) Figure 2-8 Internal reproductive structures.

Figure 2-15 Drawings of the uterus of several mammalian species. Note the differences in the ratio of uterine body to uterine horn. Litter bearing species have a greater uterine horn area.

ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure 2-5. Photographs showing the internal reproductive structures of the cow and ewe.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure 2-7. Photographs showing the internal reproductive structures of the sow and mare.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure 2-9. Photographs showing the internal reproductive structures of the bitch and queen.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure 2-20. Photographs of the cervixes of the cow, ewe, sow, and mare.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure 2-17. Photographs of the interior anatomy of uteri from a cow, ewe, sow, and mare.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure 2-13. Photographs of the anatomy of the oviduct and associated structures in the cow, ewe, sow, and mare

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure 2-14. Pictures of the anatomy of the oviduct and its components in the bitch and queen.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Figure 2-12. Illustration of the anatomy of the oviduct and its components.

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ANS 3319C Reproductive Physiology and Endocrinology Lab - Female Reproductive Anatomy

Additional Notes:

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