4_Estrous Cycle

“Estrus”

• was used first by Heape (1900) as a Latin adaptation of the Greek word oistros, meaning gadfly, sting, or frenzy to describe the “special period of sexual desire of the female”

• a period of strong sexual desire made evident through behavior

• occurs close to the time of ovulation

Heape (1900)

Estrus was used first by ___

oistros

Estrus was used first by Heape (1900) as a Latin adaptation of the Greek word ___, meaning gadfly, sting, or frenzy to describe the “special period of sexual desire of the female”

gadfly, sting, or frenzy

Estrus was used first by Heape (1900) as a Latin adaptation of the Greek word oistros, meaning ____ to describe the “special period of sexual desire of the female”

special period of sexual desire of the female

Estrus was used first by Heape (1900) as a Latin adaptation of the Greek word oistros, meaning gadfly, sting, or frenzy to describe the “____”

anestrus,

Heape also used:

• nonbreeding season when reproductive organs are quiescent

Proestrus (Heape)

Heape also used:

• animal coming on heat

Metestrus (Heape)

Heape also used:

• in the absence of conception, when estrus changes in the reproductive tract subside

Diestrus (Heape)

Heape also used:

• reproductive tract prepares for receipt of the ovum

Estrous cycle

• is a reproductive cycle observed in non-primate vertebrates such as rats, mice and pigs to name a few.

• A repeated series of events where preparation for ovulation followed by regressive changes in the female in the absence of pregnancy take place

non-primate vertebrates

Estrous cycle is a reproductive cycle observed in ____ such as rats, mice and pigs to name a few.

reverts to its original state devoid of blood discharge

Similar to the menstrual cycle, female animals become receptive to males during brief periods of “heat” or estrus. However, at the end of the cycle, the uterine lining simply ____

changes in the ovary, uterus and vagina

The Estrous cycle is divided into stages marked by ___

Proestrus

Stage of Estrous Cycle:

• is the period of preparation where new ovarian follicles grow and the endometrium develops.

• a period os active preparatory changes, when everything is again in readiness for reproduction

• vagina is gaping and the tissues are reddish pink and moist

• Duration: 12-14 hours

• External genitalia:

  • Dry vaginal mucosa.

  • Vaginal lips are slightly swollen.

• Cells of the Vaginal Mucosa:

  • A layer of thick epithelium with mitoses in the inner layers.

• Vaginal Smear:

  • Only epithelial cells are observable. None to few leucocytes.

• Sexual behavior: The rat is in heat towards the end of this cycle.

Estrus

Stage of Estrous Cycle:

• when mating occurs

• a short time of complete preparedness for reproduction accompanied by ovulation and increased sexual desire

• ovarian follicle bursts, releasing the ovum (ovulation)

• Duration: 12 hours

• External genitalia:

  • Dry vaginal mucosa, lusterless.

  • Vaginal lips are swollen.

• Cells of the Vaginal Mucosa:

  • Outer layer of epithelial cell become cornified and sloughed off into the lumen

• Vaginal Smear:

  • Hundreds cornified cells present.

• Sexual behavior: The rat is in heat and ready for copulation.

Early Metaestrus

Stage of Estrous Cycle:

• Duration: 15 hours

• External genitalia:

  • Dry vaginal mucosa, lusterless.

  • Vaginal lips are not swollen.

  • Vaginal tissues are pale and dry; Dorsal lip is not edematous/swollen as in etrus

• Cells of the Vaginal Mucosa:

  • Cornified layer is shredded and completely detached to the epithelium.

• Vaginal Smear:

  • There are many cornified cells present and leucocytes.

• Sexual behavior: The rat is not in heat.

Late Metaestrus

Stage of Estrous Cycle:

• Duration: 6-12 hours

• External genitalia:

  • Vaginal mucosa is slightly moist.

  • Vaginal lips are not swollen.

  • Vaginal signs are similar to early metestrus, but the lip is less edematous/swollen and has receded

• Cells of the Vaginal Mucosa:

  • Cornified layer is gone. Epithelium is thin layered.

  • Presence of many leucocytes is evident.

• Vaginal Smear:

  • There are still cornified cells but there are many leukocytes present.

• Sexual behavior: The rat is not in heat.

ovulation

Almost simultaneous to estrus is the release of the egg from the ovarian follicles, a process known as ___

Metestrus

Stage of Estrous Cycle:

• Should mating and fertilization fail to occur, estrus is followed by ___, where corpus luteum is formed in the ovary, and sexual activity ceases.

• A period during which the fruitless preparation for pregnancy undergo regression

• A period of repair, when mating and fertilization fail to occur

• a metestrus smear consists of the same proportion among leukocytes, cornified, and nucleated epithelial cells

• predominant presence of small densely stained leukocytes

• Duration: 22 hours

• smear reveals the epithelial cells reaching its lowest level, presence of leukocytes, a few cornified cells, and basophilic cells

Diestrus

Stage of Estrous Cycle:

• during which the uterus diminishes in size and becomes anemic

• a period of quiescence and slow growth

• the uterus diminishes in size and become anemic

• Duration: 55-57 hours

• External genitalia:

  • Vaginal mucosa is moist and glistening.

  • Vaginal lips are not swollen

  • Vagina has a small opening and the tissues are bluish-purple and very moist

• Cells of the Vaginal Mucosa:

  • Epithelial layer is thin.

  • There is no cornified layer formed yet.

  • Some leukocytes are still present.

• Vaginal Smear:

  • There are many leukocytes and epithelial cells.

• Sexual behavior: The rat is not in heat.

Epithelial cells

• Non-cornified squamous epithelial cells.

• round and nucleated

Cornified cells

• Keratinized squamous cells with horny appearance

• irregular; without nucleus

White blood cells/Leukocytes

characterized as small, round cells and by the presence of irregularly-shaped or large nucleus.

Males

sexually potent throughout adult life

Females

• have sexual periodicity which follows the development and maturity of the female gamete

• period of strong mating impulse

every 4-5 days for 12 months

Rodents’ estrous cycle lasts _____ from the onset of sexual maturity

• cellular types from vaginal smear and proportion among them

• appearance of vagina

• histological features of reproductive tract

• performing vaginal lavage, crystal violet staining, and vaginal cytological evaluation

How to determine the stages of the estrous cycle in female rodents:

stratum granulosum


Formation of the ___ over the stratum germinativum of the vaginal epithelium, consisting of flattened epithelial cells containing many keratohyalin granules, marks the start of proestrus.

keratohyalin granules


Formation of the stratum granulosum over the stratum germinativum of the vaginal epithelium, consisting of flattened epithelial cells containing many ____, marks the start of proestrus.

lighter and less moist

Vaginal sign in Estrus phase is similar to proestrus but the tissues are ____

anucleated cornified cells

An estrus smear primarily consists of ___

loss of mitotic figures

In estrus stage, there is a ___ and a progressive shedding of the superficial mucous and cornified layers, with a reduction in the height of the epithelium, and cell debris is present in th lumen

progressive shedding of the superficial mucous and cornified layers

In estrus stage, there is a loss of mitotic figures and a ________ , with a reduction in the height of the epithelium, and cell debris is present in th lumen

complete detachment of the cornified epithelium

The start of metestrus is marked by the mid region of the vagina showing a ____, generally with residual squames present in the lumen. There is a continued desquamation of epithelial cells throughout the stage, with a progressive loss of the stratum granulosum and upper germinativum.

residual squames present in the lumen

The start of metestrus is marked by the mid region of the vagina showing a complete detachment of the cornified epithelium, generally with _____. There is a continued desquamation of epithelial cells throughout the stage, with a progressive loss of the stratum granulosum and upper germinativum.

Cow

Estrus period length by species:

• 12-18 hours

Ovulation rates by species:

• 1 egg per estrus

Ewe

Estrus period length by species:

• 24-36 hours

Ovulation rates by species:

• 1 to 3 eggs per estrus

Sow

Estrus period length by species:

• 48-72 hours

Ovulation rates by species:

• 10 to 20 eggs per estrus

Mare

Estrus period length by species:

• 90-170 hours

Ovulation rates by species:

• 1 egg per estrus

Hens and Women

Estrus period length by species:

• none

Ovulation rates by species:

• Approx 28 eggs per month (HEN)