Comparative Anatomy: Estrous (Cram)

Fill in the blank: The ______ cycle is the sequence of events that occurs from one heat until the next heat.

estrous

Refers to the phase when the female is sexually receptive

Estrus (means: desire)

Of or pertaining to a mammal that has one estrous period per breeding season. Give an example species

Monestrous

Example: Bear

Species that go into heat twice per year. Give an example species

Diestrous

Example: Dog

Having several estrous cycles annually or during a breeding season. Give two example species

Polyestrous

Example: Cow, sow

Having estrous cycles only during part of the year. Give four example species.

Seasonally polyestrous

Examples: Mare, ewe, cat, doe

Fill in the blank: Increasing daylight hours stimulates cycling in spring and summer in _____ and _____. Decreasing hours of daylight stimulates cyclicity in _____ and _____ in autumn.

mares, cats, ewes, does

What do rabbits and humans have in common in regards to their estrous cycle?

Both species are able to conceive at almost any arbitrary moment

What is the estrus frequency in the ewe?

17 days

What is the estrus frequency in the cow, doe, and sow?

21 days

What are the four stages of the estrous cycle in cattle?

1. Proestrus
2. Estrus
3. Metestrus
4. Diestrus

Term for no cyclical activity is occurring in the ovaries

Anestrus

Period of growth of tertiary (graafian) follicle, thickening of vaginal wall, submucosa of uterus becomes thickened, and more cells with cilia develop in the oviduct

Proestrus

Period of heat or season, swelling of external genitals occurs, postural and voice changes occur, and the cervix dilates

Estrus

What does this behaviour in cows indicate?

The cow that is standing to be mounted is in estrus, the cow doing the mounting may or may not be in estrus (usually coming into or coming out of estrus)

What does the appearence of this cow's vulva indicate?

Watery mucous and swollen vulva indicate she is in estrus

What does the appearence of this cow's vulva indicate?

Metestrual vaginal discharge occurs in 90% of heifers and 45% of cows. It occurs in metestrus (after estrus) and doesn't indicate anything about failure or success in breeding

Note: Some clients will think it's an abortion, it ain't!

Length of estrus in a cow

16 hours

This mare (right) is winking, and not kicking the stallion (left). What does her behaviour indicate?

The winking and failure to kick, and her tail raising are signs that she is in estrus. Other signs would include nervousness, and interest in the stallion.

What do sheep tails do to indicate that they are in estrus?

Vibrating

Which sow is in heat (left or right)?

Right. The vulva is much more swollen

When cats live indoors, what happens to thier estrous cycle?

They become polyestrous instead of seasonally polyestrus, because they don't experience environmental changes

A female dog has blood spotting, what does this indicate?

She is in proestrus or possibly the first two days of estrus

What is the range of estrus length in the dog?

3-21 days

Note: Ovulation occurs on the third day after the start of estrus. Because the range is so large doing a vaginal smear to determine estrus is recommended

Stage of estrus where a dog acts like she is still in heat, but is not actually

Pseudocyesis stage

What stage of the estrous cycle is this cow in: A corpus luteum (CL) is formed, progesterone levels in circulation begin to rise, she may bleed as a result of a drop in estrogen

Metestrus

What stage of the estrous cycle is this cow in: Period of maximum corpus luteum size and function, high levels of progesterone in circulation

Diestrus

Name these types of vaginal epithelial cells

A – Parabasal cell
B – Intermediate cell
C – Superficial cell

Which vaginal epithelial cell is seen only in estrus?

Superficial cells

Term for the nucleus in a superficial cell

Pyknotic nucleus

Which vaginal epithelial cell is seen in diestrus, anestrus and early proestrus?

Parabasal cells

Which vaginal epithelial cell is seen in all stages except estrus?

Intermediate cells

Which vaginal epithelial cell can sometimes appear in strings/sheets?

Superficial cells

What stage of estrus is this dog in? What two factors let you know?

Anestrus

1. Intermediate and parabasal cells
2. Few RBC's

What stage of estrus is this dog in? What two factors let you know?

Proestrus

1. Intermediate and superficial cells
2. More RBC's

What behaviour can clue you in to your dog being in proestrus?

Female attracts males, but is not receptive

What stage of estrus is this dog in? What factor lets you know?

Estrus

1. Superficial cells

Which three stages of estrus are neutrophils present, and to what extent are they present?

1. Proestrus - Increased in early proestrus

2. Diestrus - Few to none

3. Anestrus - Few to none