VM528 - Repro Exam 1

What hormone enters the brain and masculinizes the hypothalamus?

testosterone

(testosterone can cross the barrier but turns into estrogen to masculinize the hypothalamus)

What would you expect to find on transrectal palpation of a heifer if she has reached puberty after ovulation?

corpus luteum

How is puberty in females defined?

age when pregnancy can be successfully supported

From the outer layer to the lumen, in the female reproductive tract is composed of which layers?

Serosa, Outer longitudinal muscularis, Inner circular muscularis, Submucosa, Mucosa

What species have cervical rings?

cow and ewe

What species have cervical folds?

mares

What species have interdigitating prominences?

sow

What species have smooth (no cervical rings /folds)?

bitch

The epithelium of the caudal vagina or vestibule is what type?

stratified squamous

In reference to the uterine layers, which of the following terms are mismatched?

a) Serosa = perimetrium

b) Mucosa = endothelium

c) Muscularis = myometrium

d) Mucosa + submucosa = endometrium

b) Mucosa = endothelium

What is the order of the oviduct components (from ovary to uterus):

infundibulum, ampulla, isthmus

What ovarian structure is most associated with progesterone?

corpus luteum

Which species does not exhibit lactational anestrus?

mare

In ruminants, what stage of the estrous cycle does the ovary secretes the highest amount of estrogen?

estrus

What structure anchors the carnivore ovaries to the body wall near the kidneys?

suspensory ligament

Gonadotropin

The hormones (FSH and LH) of anterior pituitary origin that stimulate gonadal function.

Meconium

A neonate's first feces

Standing estrus

A female behavioral characteristic of estrus in which the female remains immobile allowing the male to mount her.

List the major structures of the female reproductive tract and describe each structure's function.

1. ovaries - produce female gametes (ova) and the hormones, estrogen and progesterone

2. oviducts - passageway for ovary and fertilization

3. uterus - nourish and house fertilized egg

4. cervix - barrier separating uterus and facilitates passages

5. vagina - copulatory organ and site for expulsion of urine during micturition

6. external genitalia - minimizes entrance of foreign material into vagina

The female reproductive tract can be described as a series of tubes. List the 4 concentric layers and describe the function of each layer.

1. Serosa (outer) - single layer of squamous cells that cover the surface of reproductive tract

2. muscularis - provide tubular components with the ability to contract

3. submucosa - houses blood vessels, nerves, and lymphatics and is supporting tissue for mucosa

4. mucosa (inner) - each part of reproductive tract is lined by different types of mucosal epithelium

The female reproductive tract is completely surrounded by continuous peritoneum with the broad ligament. List the components of the broad ligament and associated attachments.

1. mesovarium (cranial) - attaches to ovary

2. mesosalpinx - supports oviduct and surrounds the ovary (bursa)

3. mesometrium - supports the uterine horns (cornua) and body of uterus

Define the components of the ovary: tunica albuginea

(outer connective tissue) - single layer of cuboidal cells (germinal epithelium), has no function relating to production of germinal cells

Define the components of the ovary: ovarian cortex

houses oocytes and cells surrounding oocytes will develop and produce follicle that will mature and ovulate, houses functional corpus luteum (produce progesterone) and corpora albicantia (represent degeneration of corpora lutea from previous estrous cycles)

Define the components of the ovary: ovarian medulla

houses vasculature, nerves, and lymphatics and is composed of dense connective tissue

Describe three features of the mare's ovary that are different from the majority of species.

1. Ovarian medulla and cortex are reversed (cortex inside and medulla outside)

2. Ovulation occurs only at one location in mare's ovary (ovulation fossa), while it occurs at random locations in the ovaries of other mammals

3. Follicles can be palpated per rectum but corpora lutea cannot (penetrate into ovarian tissue)

Distinguishing features of Primary follicles?

Has an oocyte surrounded by a single layer of cuboidal epithelium or follicular cells, do not divide, either develop into advanced secondary follicle or degenerate

Distinguishing features of secondary follicles?

2 or more layers of follicle cells without an antrum or cavity, oocyte surrounded by thick, translucent layer (zona pellucida)

Distinguishing features of antral follicles?

Fluid-filled cavity (antrum), fluid is follicular fluid, can be observed by naked eye on surface of ovaries (blister-like)

Distinguishing features of corpora lutea?

Produce progesterone, yellow, large

Distinguishing features of corpora albicantia?

represent degeneration of corpora lutea from previous estrous cycles, white (increase of connective tissue), scar-like

What hormones are produced from the following distinct layers of the antral follicle?

· Theca externa-

· Theca interna-

· Granulosal cell layer-

· Theca externa- supports follicle

· Theca interna- produce androgens under influence of LH

· Granulosal cell layer- has FSH receptors, produce estrogen, inhibin and follicular fuid

What are the distinguishing features and function of the Infundibulum?

Funnel-shaped opening that forms a pocket that captures newly ovulated oocyte

Terminal end of oviduct, captures newly ovulated oocyte

What are the distinguishing features and function of the ampulla?

Thick, large diameter with internal fern-like mucosal folds with ciliated epithelium

Merges with isthmus, control point that allows only fertilized oocytes to pass into isthmus (fertilization)

What are the distinguishing features and function of the isthmus?

Smaller in diameter, thicker muscular wall and fewer mucosal folds

Allows only fertilized oocytes to pass to uterus

Describe the 3 types of uteri found in mammals and list examples of species that have each type of uterus.

1. Duplex - two cervical canals that separate each uterine horn into distinct compartments. Two types, first type single vaginal canal opening to exterior and on interior, it splits into two vaginas and two cervixes (marsupials, opossum), second type (rabbit) two uterine horns and two distinct cervical canals connected to single vaginal canal

2. Bicornuate - two uterine horns and small uterine body, mare (short uterine horns and large uterine body), cow/ewe/goat (uterine horns are intermediate length), bitch/queen/sow (little fusion - long uterine horns)

3. Simplex - single uterine body (primates including humans)

What is the serosa layer of the uterus called?

perimetrium

What is the muscularis layer of the uterus called?

myometrium

What components make up the endometrium of the uterus?

mucosa and submucosa

Describe 5 functions of the uterus.

1. sperm transport

2. luteolysis and control of cyclicity

3. environment for preattachment embryo

4. maternal contribution to the placenta

5. expulsion of the fetus and fetal placenta

Compare and contrast the endometrium of the mare and cow.

In ruminants, the surface of the endometrium has small, nonglandular areas that protrude from surface (caruncles). In contrast, the endometrium of the sow and mare have no caruncles but have many endometrial folds.

Describe similarities and differences of the cervix of the bitch, mare, cow and sow.

Provides lubrication, a flushing system and a barrier during pregnancy. It is a relatively thick-walled, non-compliant organ that serves as a barrier to sperm transport in the ewe, cow, bitch, and queen but not in the mare and sow. It has a cervical canal surrounded by a single (bitch and queen) or multiple (cow, ewe, sow, mare) folds or rings protruding into cervical canal. In cow and ewe, several of these rings form interlocking finger-like projections. In sow, rings interdigitate in intimate fashion (initial deposition of semen occurs in cervix).

What type of epithelium is located in the caudal vs. the cranial vagina? What is the embryologic significance of this difference?

Caudal has stratified squamous epithelium and cranial has columnar epithelium. Cranial originates from paramesonephric ducts and fuses with caudal vagina that originates from an invagination of the urogenital sinus.

How does estrogen influence the epithelium of the caudal vagina?

During time of estrogen dominance, stratified squamous epithelium thickens dramatically.

What is puberty?

Acquisition of reproductive competence. It is a process that occurs over time and depends on the ability of specific hypothalamic neurons to produce GnRH in sufficient quantities to promote and support gametogenesis.

The hypothalamus is inherently female. T or F.

True. Testosterone defeminizes the hypothalamus during embryogenesis and eliminates the GnRH surge center in the male.

What hormone defeminizes the hypothalamus? What does this defeminization prevent from developing?

Testosterone defeminizes the hypothalamus during embryogenesis and eliminates the GnRH surge center in the male.

What is the role of alpha-fetoprotein in feminization of the hypothalamus?

It binds estradiol and prevents it from crossing the blood-brain barrier. Therefore, estradiol cannot affect the hypothalamus.

The female hypothalamus contains a ___________ + _____________ where as the male hypothalamus only contains a ____________.

The female hypothalamus contains a surge center + a tonic center where as the male hypothalamus only contains a tonic center.

What hormone remains relatively consistent throughout the day in the male as compared to the female which has a surge every estrous cycle?

LH

The onset of puberty in the male and female has different definitions. Please list the female and highlight which is the most valid criterion for each species.

1. Age at first estrus (heat) (not accompanied by behavioral estrus in heifers and ewes)

2. Age at first ovulation (difficult to determine - palpation, ultrasound, endoscopy)

3. Age at which a female can support pregnancy without deleterious effects (most applicable in all domestic animals and humans)

Name two factors that impact the development of the hypothalamic GnRH neurons in the female.

1) Development of a threshold body size and/or composition

2) Exposure to certain environmental or social cues

True or false. Genetics influences age at puberty.

True

What is the major limiting factor for onset of puberty in females?

The female must reach a threshold body size before puberty can be achieved.

What is different about the hypothalamic secretion of GnRH before and after puberty in the female?

Before puberty, GnRH neurons in tonic center and surge center of hypothalamus release low amplitude and low frequency pulses of GnRH because estradiol is too low. After puberty in the female, the tonic center controls basal levels of GnRH, but they are higher than in the prepubertal female because the pulse frequency increases. The surge center controls the preovulatory surge of GnRH.

True or false. The surge center responds primarily to negative feedback stimulus.

false

Explain the feedback system for the surge center.

The surge center responds primarily to a positive feedback stimulus. The surge center lies dormant in prepubertal female since the prepubertal ovary does not secrete sufficient quantities of estradiol to stimulate the surge center to secrete high amplitude pulses of GnRH.

While the exact mechanisms of metabolic signaling have not been described, what are the proposed influences of leptin and kisspeptin on GnRH secretion?

Leptin may be an important signal that notifies key hypothalamic neurons that influence GnRH secretion the nutritional status is adequate because a threshold degree of "fatness" has been achieved. Kisspeptin neurons may act directly on GnRH neurons and stimulate the firing of GnRH neurons.

Describe external factors that influence the onset of puberty in females.

Season of birth and social cues (presence of male or size of social group in which females are housed). Small groups housed together have delayed onset of puberty.

In mammals, what are the two types of reproductive cycles?

estrous cycle and menstrual cycle

Define the estrous cycle.

Consists of physiologic events that occur between successive periods of sexual receptivity (heat) and/or ovulation. Two phases, follicular and luteal phase. Follicular phase is dominated by estradiol secretion by ovarian follicles that initiates sexual receptivity and luteal phase is dominated by progesterone from corpus luteum that prepares reproductive tract for pregnancy.

Throughout the adult female's life, describe three things that can interrupt her estrous cycle.

1. Pregnancy

2. Nursing

3. Season of the year

4. Certain forms of stress and pathology (nutrition inadequate)

Define anestrus.

Periods of time when estrous cycles cease.

True or false. Copulation generally occurs after ovulation.

false. copulation occurs prior to ovulation

When pregnancy occurs, the female enters a period of __________which ends after parturition, _______________, and _____________.

When pregnancy occurs, the female enters a period of anestrus which ends after parturition, uterine involution (acquisition of normal uterine size and function), and lactation.

Describe the difference between estrous and estrus and when should each term be used.

Estrus is a noun (ex. the cow is displaying estrus), while estrous is an adjective (ex. the length of the estrous cycle in the pig is 21 days).

Name two terms that a client may use to refer to the period of estrus.

heat and season

List the three types of estrous cyclicity and species that have each type of cyclicity.

1. Polyestrus - cattle, swine, and rodents have uniform distribution of estrous cycles throughout the entire year.

2. seasonally polyestrus - Sheep, goat, mares, deer, and elk display clusters of estrous cycles that occur only during a certain season of the year.

3. Monoestrus - only one cycle per year - dogs, wolves, foxes, and bears

Sheep and goats are ________-day breeders while the mare is a _______-day breeder.

Sheep and goats are short-day breeders (fall) while the mare is a long-day breeder (spring).

How many estrous cycles does the typical domestic canid have every 3 years? How does this compare to the non-domestic canids?

Canids have three estrous cycles every two years but are classified as monoestrous.

Follicular phase: % of estrous cycle, primary ovarian structure, primary hormone, stages of the estrous cycle

20%

Large antral, growing follicles

Estradiol

Proestrus and estrus

Luteal phase: % of estrous cycle, primary ovarian structure, primary hormone, stages of the estrous cycle

80%

Corpora lutea

progesterone

Metestrus and diestrus

Describe the major events of the four stages of the estrous cycle.

1. Proestrus - formation of ovulatory follicles and E2 secretion. Progesterone declines because luteolysis

2. Estrus - sexual receptivity (behavioral) and peak E2 secretion

3. Metestrus - CL formation and beginning of P4 secretion. Estradiol and progesterone are low

4. Diestrus - sustained luteal secretion of P4 (longest stage), corpus luteum is fully functional and progesterone is high

Describe the primary and secondary behavioral characteristics associated with sexual receptivity.

Primary- locomotion, phonation, nervousness, mounting other animals

Secondary- standing estrus or lordosis (arching of the back in preparation for mating)

What is the longest stage of the estrous cycle?

diestrus

The stages of the estrous cycle are different for the bitch and queen. Describe these differences below.

Bitch- anestrus (lasts 20 weeks in nonpregnant bitch), proestrus, estrus, and diestrus.

Queen- proestrus, estrus, postestrus (interestrus period that follows estrus in a queen that has not been induced to ovulate by copulation), diestrus, and anestrus. They are polyestrus.

Define superfecundation and list some species in which this can occur.

Occurs when multiple ovulations produce multiple oocytes during a single estrus period that are fertilized by spermatozoa from different males. Occurs in dogs, canids.

Anestrus can be caused by:

-stress

-pathology

-pregnancy

-lactation

-presence of offspring

-season

Describe the hormonal changes that occur just before parturition.

Progesterone declines rapidly just before parturition and estradiol increases

Explain the suggested reason that some species experience seasonal anestrus.

A way of preventing females from conceiving during periods of the year when survival of the developing embryo and the neonate would be low.

Describe what silent ovulation is, including what species this occurs in and what hormone is absent before this estrus.

An ovulation is not preceded or accompanied by behavioral estrus. Occurs in the ewe and progesterone is absent before this estrus.

True or false. The responsiveness of kisspeptin neurons to RFRP-3 is the fundamental difference between short-day and long-day breeders.

true

When the days are short, __________ increases à decreases __________. In short-day breeders, this signals an increase in ________ leading to an elevation in ______ and ______ from the anterior pituitary gland. In long-day breeders, this signals a decrease in __________ leading to termination of _______ and _______ from the anterior pituitary.

When the days are short, melatonin increases à decreases RFRP-3. In short-day breeders, this signals an increase in GnRH leading to an elevation in FSH and LH from the anterior pituitary gland. In long-day breeders, this signals a decrease in GnRH leading to termination of FSH and LH from the anterior pituitary.

True or false. Mammary stimulation is solely responsible for lactation anestrus.

false

Name two species that do not experience lactational anestrus.

mare and alpaca

Other than suckling, what are three factors that may be responsible for inhibition of GnRH during the postpartum period?

1. Visual encounter with offspring

2. Olfactory encounter with offspring

3. Auditory encounter with offspring

Describe the importance optimal nutrition has on primiparous lactating heifers.

In lactating females, inadequate nutrition will prolong duration of lactational anestrus, especially in primiparous females (those that have given birth for the first time). They have restricted dietary intake compounded with energy requirements of lactation and growth.

Of the 3 structures below located in the caudal abdomen and pelvis, which is the most dorsal? The most ventral?

urinary bladder

reproductive tract

rectum.

urinary bladder is most ventral and rectum is most dorsal

What structure corresponds to the caudal vagina as described in PPP? What landmark(s) allows you to separate it from what is described as the cranial vagina in PPP?

Caudal vagina = vestibule

Cranial vagina = vagina (anatomical terminology)

Caudal urethral opening is at cranial end of vestibule. Remnant of hymen separates vestibule from vagina proper

What does the suspensory ligament attach to?

ovary to dorsal body wall near kidney in dogs and cats (the equine mesovarium is also sometimes called that)

What does the mesometrium attach to?

uterine horns and body to dorsal body wall - aka broad ligament

What does the mesosalpinx attach to?

uterine tube technically to dorsal body wall, but for all practical purposes to mesovarium and mesometrium

What does the mesovarium attach to?

ovary and ovarian vessels to dorsal body wall

What does the round ligament attach to?

ovary to: near vulva in dogs, passing through inguinal ring deep inguinal ring in cats ends before reaching inguinal ring in most other species

What arteries supply the uterus of small animals? What about large animals?

SA: uterine branches of ovarian and vaginal arteries

LA: also have a middle uterine artery (its origin varies with the species, you don't need to know it)

What species has an ovulation fossa?

mare

It is relatively easy to artificially inseminate a mare because cervical folds are longitudinal. What large animal species have a different cervical anatomy and are thus more difficult to inseminate? How does their cervical anatomy differ from that of the mare?

Ruminants have cervical rings

Pigs have cervical cushions ("pulvini")

What structures can be used to retract the bovine uterus during rectal palpation?

intercornual ligaments and cervix

The hormone that directly brings about ovulation via weakening of the follicle wall and increased follicular pressure is what?

PGF2-alpha

What hormone selectively suppresses FSH secretion from the anterior pituitary?

Inhibin

The gonadotrophin sensitive pool of antral follicles begins to grow under the influence of what hormones?

basal FSH and LH