Basic concepts in gynecology Flashcards
The two types of reproductive cycles are
the estrous cycle and the menstrual cycle.
An estrous cycle consists of the physiologic events that occur between successive
periods of sexual receptivity (estrus or heat) and/or ovulation.
The length of cycle varies from about 4 days in rodents to as long as 14 – 16 weeks in elephants.
Each menstrual cycle consists of 3 distinct phases that reflect the condition of the uterine endometrium. Describe the phases.
The cycle starts with menses (about 4 – 6 days) where the endometrium is sloughed to the exterior.
Second phase (about 9 days) is proliferative phase in which follicles develop and secrete estradiol, the endometrium begins to grow and increase in thickness.
The final phase, the secretory phase (14 days) is dominated by the CL that secretes progesterone and estradiol. The endometrium grows in thickness as a function of progesterone.
At the end of this 28 day period the endometrium begins to slough.
estrus vs estrous
ESTRUS is a noun = The cow is displaying estrus.
ESTROUS is an adjective = The length of the estrous cycle in the cow is 21 days.
Why do some animals bleed during estrus?
It’s NOT related to endometrial sloughing.
Its related to the effect estrogen has on histamine release which in turn affects endometrial/vaginal capillary permeability.
More common in heifers than in more mature cows. The higher the production, the lower the chance of seeing blood during estrus.
Estrous cycles are categorized according to
the frequency of occurrence throughout the year.
The three types of estrous cyclicity are:
Polyestrus (cattle, queen, pig, rodents etc.)
Seasonally polyestrus (short-day breeders and long day breeders aka ewe vs mare)
Monoestrus (large carnivores including dogs)
define superfetation
when a second, new pregnancy occurs during an initial pregnancy. It’s rare in humans and observed in animals much more frequently.
define superfecundation
fertilization of a second ovum during the same estrus cycle as a result of a second mating, leading to fetuses of the same age but different parentage.
e.g. more commonly in cats
The estrus cycle consists of two major phases:
follicular phase and the luteal phase
But Can be also divided into four stages:
- Proestrus = the phase of follicular development preceeding oestrous
- Estrus = visible behavioural changes
- Metestrus = first stage of CL development
- Diestrus = the phase of luteal activity
Follicular phase = pro- + estrus
Luteal phase = met- + diestrus
Estrus cycle divided into 4 phases:
Proestrus = the phase of follicular development preceding estrous
Estrus = visible behavioral changes
Metestrus = first stage of CL development
Diestrus = the phase of luteal activity
Not particularly useful for the large domestic animals or the primates.
More used concepts: FOLLICULAR PHASE and LUTEAL PHASE.
Follicular phase = pro- + estrus
Luteal phase = met- + diestrus
Describe the Follicular phase:
the period from regression of corpora lutea to ovulation (20% of the estrous cycle)
During the follicular phase:
- Large antral follicles = the primary ovarian structures
- Estradiol (secretion product of the follicles) = the primary hormone
Follicular phase = pro- + estrus
Luteal phase = met- + diestrus
Describe the Luteal phase:
the period from ovulation until corpora lutea (CL) regression (about 80% of the estrous cycle)
During the luteal phase:
- Corpora lutea (CL) = the primary ovarian structure (s)
- Progesterone (secreted by CL) = the primary hormone
Follicular phase = pro- + estrus
Luteal phase = met- + diestrus
estrous cycle lengths of different species & estrus length.
ewe?
mare?
queen?
sow?
ewe 17 days, 30 hour heat
mare 21 days, 7 day heat
queen 17 days, 9 day heat
sow 21 days, 50 hour heat
Define Postestrus:
Term is used only in queens. Term used to describe an interestrus period that follows estrus that has not been induced to ovulate by copulation.
In queens that have not copulated, no ovulation occurs and no CL forms. Therefore, neither metestrus (CL formation) nor diestrus occurs.
Define Anestrus:
„without estrus (Heat)“
Ovaries are relatively inactive and neither ovulatory follicles nor corpora lutea are present.
Anestrus is the result of insufficient GnRH release from the hypothalamus to stimulate and maintain gonadotropin secretion by the pituitary.
True anestrus and apparent anestrus: it is very important to distinguish between those terms. Explain.
True anestrus – caused by insufficient hormonal stimuli.
Gestational anestrus is a normal condition brought about by inhibition GnRH by progesterone.
Seasonal anestrus is a normal condition.
Apparent anestrus – caused by failure to detect estrus or failure to recognize that female is pregnant.
Describe the Ovarian cycle. (5)
- Maturation of the oocyte 16 – 20 (21) days
- Ovulation stage 1 – 2 days
- Post-ovulation stage 2 – 5 days
- Stage of CL 5 – 16.5 (17) days
- Regression stage of CL 16.5 – 21 days
Describe the Tubular cycle.
Changes in oviduct epithelium.
- number of cytoplasma extrusion
- thickness of epithelium
- length of epithelium cilia
Describe the Uterine cycle
Changes in endometrium during the estrous cycle.
All layers experience change.
- Endometrial epithelium max thickness at the beginning of proestrus, during the estrus and in the middle of the cycle.
- Uterine gland secretion start from day 3 of cycle. Uterine gland secretion is at maximum level during diestrus. At the same time uterine resistance to infections will decrease.
- Edema of the uterine stroma is strong during proestrus and estrus. High level of estrogens will lead to release of histamines from the cells. Histamine will increase the permeability of blood capillaries and we will see post-estrus bleeding.
Describe the Cervical cycle
changes in the cervix
Most prominent changes will present in cervical epithelium (increase of secretory activity) during estrus.
Relaxation of muscular tissue of the cervix and partial opening of the cervical canal.
Due to rise in estrogen
Changes will disappear at the beginning of diestrus
Describe the vaginal cycle.
Changes in vagina during the estrous cycle.
Most prominent changes in the epithelium of the vagina are described in mouse and rat.
Very prominent changes also in the bitch
In cow, edema of the mucus layer and the mucus secretion is visible at the beginning of estrus in the uterine cervix area and when estrus is developing the mucus secretion is moves towards the the vulva.
At the end of estrus edema of the mucus layer will disappear and a new increase is visible when new proestrus is approaching
Principle behind using prostaglandins to synchronize or induce cow estrus.
PGF2α plays a crucial role in the natural regression of the corpus luteum
Progesterone prevents release of GnRH, LH, and FSH.
When PGF2α is administered exogenously (injected), it mimics the cow’s natural luteolytic mechanism.
regression of the CL results in the rise of GnRH and subsequently LH and FSH, stimulating the development of a new follicle on the ovary.
Within a few days after the PGF2α injection, estrus (heat) is induced, and ovulation follows.
Before attaching to the endometrium, what processes does an embryo need to go through first? (4)
the pre-attachment embryo (morula) needs to develop into a blastocyst, hatch from the zona pellucida and develop a functional trophoblast.
The early embryo must secrete materials that prevent luteolysis or enhance luteal function to maintain pregnancy.
Syngamy =
fusion of the male and female pronuclei, after which the zygote becomes an embryo
embryo vs fetus
An embryo has not acquired an anatomical form that is readily recognizable in appearance as a member of specific species
Fetus is generally recognizable as a member of given species.
Conceptus = defined as the product of conception and includes:
The embryo during the early embryonic stage.
The embryo and extraembryonic membranes during the pre-implantation stage.
The fetus and placenta during the post-attachment phase.
describe camelids heat
induced ovulators. 5 day heat
camels
llamas
alpacas
etc.
The extraembryonic membranes are a set of four anatomically distinct membranes that originate from
the trophoblast, endoderm, mesoderm and the embryo.
Developing fetus is surrounded by three layers (extraembryonic (fetal) mebranes):
Amnion
Allantois
Chorion
Describe the Amnion:
The most inner fetal membrane which surrounds fetus completely in all animals. It forms the amnionic sac. Very thin, but strong, white-gray membrane.
The origin of amnion is the embryonic trophoblast and development of amnion will start at the end of 3rd week of pregnancy.
Describe the Amnionic fluid:
Will surround the fetus (amnion together with amnionic fluid is called amnionic sac). Color is gray or yellowish.
Maximum amount is up to 10L between 5 – 7 months of pregnancy (large animals).
At the end of pregnancy the amount is 3 – 5L in cow and 5 – 7L in mare.
The main task of the amnionic fluid is mechanical protection of the fetus.
Important also during parturition.
Describe the Allantois:
located between amnion and chorion.
develops parallelly with amnion and is formed during 3rd week of pregnancy.
It is the evagination from the posterior region of primitive gut.
Is a fluid filled sac that collects liquid waste from embryo. Allantois sac surrounds the fetus and the amnionic sac completely in mare and carnivores.
In cow and sow only partly.
As the embryo grows, the allantois continues to expand and eventually will make contact with the chorion.
Describe the allantochorion.
When the allantois reaches a certain volume it, it presses against the chorion and eventually fuses with it.
When fusion takes place the two membranes are called the allantochorion.
In cow, mare and ewe; the amount of allantoic liquid will increase during pregnacy. In sow it will disappear at the end of pregnancy.
Describe the chorion.
Surrounds allantois, amnionic sac and fetus completely. Origin is trophoblast.
During the first stage of development so called prochorion will develop. Its surface is fully covered with villi.
Later, blood vessels penetrate into the villi.
From one side, chorion is affiliated with other fetal membranes and from the other, chorion is connected with endometrium via the chorionic villi.
In mare and carnivores connections only with allantois.
In ruminants and pigs, with allantois as well as the areas where allantois is not present with amnion.
forficate sac =
In ruminants: whether there is one fetus or several fetuses, the chorion is located in both uterine horns and forms a forficate sac.
At the beginning, it develops in the pregnant uterine horn and at the end of 3rd week of pregnancy it start to invade the non-pregnant horn.
By 37 days of pregnancy, chorion is present in both uterine horns.
During ruminant pregnancy, where is the chorion located?
in both uterine horns even if its a singleton pregnancy.
At the beginning, it develops in the pregnant uterine horn and at the end of the 3rd week of pregnancy it start to invade the non-pregnant horn. By 37 days of pregnancy, the chorion is present in both uterine horns.
the chorion thus forms the forficate sac.
Discrete areas of villi can be on the surface of the ruminant chorion. These are called…?
cotyledons when they’re the fetal side
caruncles when referring to the maternal side
and altogether they form placentomes.
placentome =
cotyledon + caruncle
During mare pregnancy, where is the chorion located?
What type of placenta do mares have?
In the mare: chorion is conjoined with allantois (allantochorion) and is present in both uterine horns forming the forficate sac.
On the endometrial side of the chorion many microcotyledons are distributed diffusely over the entire chorion. The chorion villi are short and the connection between chorion and endometrium is not very strong.
The equine placenta is diffuse, microcotyledonary, and epitheliochorial.
During sow pregnancy, where is the chorion located?
What type of placenta do sows have?
Sows have similar placentas to horses, except their chorion joins more deeply, it joins the allantois and amnion (whereas horses’ joins the allantois).
Pigs have an epitheliochorial and diffuse placenta (but NOT microcotyledonary like mares).
Describe the carnivore chorion.
What type of placenta do carnivores have?
The chorion is an elongated sac.
Carnivore placentas are zonary like a belt (2.5-6 cm wide). Villi are not found anywhere else but within this belt-like zone.
Placentas are classified according to
the distribution of chorionic villi.
Placental classifications according to chorionic villi distribution are: (4)
Cotyledonary placenta (have numerous, discrete button-like structures called cotyledons) e.g. ruminants
Diffuse placenta (uniform distribution of chorionic villi that cover the surface of the chorion) e.g. some mammals like horses and swine
Zonary placenta (have a band-like zone of chorionic villi) e.g. carnivores
Discoid placenta (form a regionalized disc) e.g. primates
The zonary placenta consists of what zones? (3)
The zonary placenta consists of transfer zone, a pigment zone and a relatively nonvascular zone.
A Band of tissue forms around the conceptus where nutrient transfer occurs.
The pigment zone or paraplacenta represents local regions of maternal hemorrhage and necrosis.
Difference between cow and sheep/goat cotyledons?
The chorion-caruncular tissue interface is shaped a little differently.
In cows (and giraffes), the caruncular tissue in convex into the receiving chorionic tissue.
In sheep and cats, the caruncular tissue in concave and the chorionic tissue inserts into it.
Placental classification based on separation between fetal and maternal blood supplies. (4)
epitheliochorial (syndesmochorial)
endothelialchorial
hemochorial
Describe the epitheliochorial placenta.
In which species is it found?
- Chorionic capillaries
- Chorionic interstitium
- Chorionic epithelium
- Endometrial epithelium
- Endometrial interstitium
- Endometrial capillaries
Pig, horses and ruminants
Describe the endotheliochorial placenta.
In which species is it found?
- Chorionic capillaries
- Chorionic interstitium
- Chorionic epithelium
- Endometrial interstitium
- Endometrial capillaries
Dogs and cats
Describe the syndesmochorial placenta.
In which species is it found?
Same as the epitheliochorial but The endometrial epithelium transiently erodes and then regrows, causing intermittent exposure of the maternal capillaries to the chorionic epithelium.
- Chorionic capillaries
- Chorionic interstitium
- Chorionic epithelium
- Endometrial epithelium
- Endometrial interstitium
- Endometrial capillaries
Small ruminants, and some sources say cows too.
Describe the hemochorial placenta.
In which species is it found?
- Chorionic capillaries
- Chorionic interstitium
- Chorionic epithelium
Primates and rodents
In addition to the feature of partial erosion of the endometrial epithelium (syndesmochorial), a unique cell type is found in ruminant placenta called…
Describe them too.
Binucleate giant cells
They are quite large and they have two nuclei.
They appear at about day 14 in the sheep and between days 18 – 20 in the cow.
Their origin is trophoblast cells and they are formed continuously throughout gestation. They constitute around 20% of fetal placenta.
During development those cells migrate from the chorionic epithelium and invade the endometrial epithelium.
May transfer:
Placental lactogen
Pregnancy specific protein B
Pregnancy associated glycoproteins
Pregnancy recognition factors in various species.
Bitch
Cow
Ewe
Mare
Queen
Sow
Woman
Bitch, none needed
Cow, IFN-tau
Ewe, ovine IFN-tau
Mare, 3 proteins or estrogens
Queen, none needed
Sow, estradiol/E2
Woman, hCG
