L17: Ovaries

What are the two functional ovarian structures?

Follicles and corpus luteum (corpora lutea).

ovaries

paired gonads that produce oocytes and hormones

oviducts

site of fertilization and embryo development

uterus

site where the embryo attaches and fetal development occurs

vagina

copulatory organ

external genitalia

access to the vagina and provides protection against infections

MCQ: what is the main function of the ovaries in female mammals?

to produce eggs and hormones

MCQ: what hormonal event triggers ovulation during the estrous cycle?

LH surge

where are the ovaries located?

in the dorsal abdominal cavity caudal to the kidneys

Which hormones are produced by the ovaries?

Estrogen and progesterone.

cortex of ovary

follicular growth and coropra luteal location

medulla of ovary

very irrigated and rich in nerve endings

at the end of which stage will ovulation happen?

follicular phase

what is the dominant structure in the luteal phase?

corpus luteum

what is the dominant hormone in the follicular phase?

estrogen

MCQ: what is the main physiological role of the estrous cycle in female mammals?

regulate the timing of ovulation and prepare the reproductive tract for potential pregnancy

what stimulates theca cells?

Luteinizing hormone (LH)

what do theca cells produce?

androstenedione

what stimulates granulosa cells?

Follicle-stimulating hormone (FSH)

what hormone do granulosa cells produce?

estrogen

folliculogenesis

ovarian follicles mature from premordial follicles to become antral structures that can release oocyte during ovulation

gonadotropin independent growth

not dependent on FSH

gonadotropin dependent growth

dependent on FSH and LH

recruited follicles

basal GnRH and FSH/LH pulses induce small groups of small antral follicles to grow

recruited follicles

some recruited follicles start to produce estrogen, many will dies

antral dominant follicles

produce large amounts of estrogen

what does the presence of progesterone do to follicles?

induces negative feedback on hypothalamus surge center =inhibit GnRH = no FSH or LH is produce = no surge = no ovulation

when can mature follicles be ovulated?

estrous follicular phase

what regulates final maturation and ovulation of dominant follicles?

LH

What triggers ovulation during the estrous cycle?

A surge of luteinizing hormone (LH).

how will high levels of estrogen affect the brain (what signs will you see in the animal)?

1. induce sexual receptivity

2. mating posture (lordosis)

3. phonation

4. increased physical activity

how will very high levels of estrogen affect the hypothalamic-pituitary?

creates strong positive feedback DURING ESTRUS to cause massive release of GnRH and LH surge = OVULATION

what activates the hypothalamic surge center?

when estrogen has passed the critical threshold

what does LH stimulate?

1. histamine

2. proteolytic enzymes

3. prostaglandins

what causes release of the oocyte?

LH surge

luteinization

after ovulation cells granulosa and theca cells are converted into luteal cells and form CL

what hormone do luteal cells produce?

progesterone

corpus luteum

temporary endocrine organ that produces progesterone during pregnancy and part of estrous cycle

which species have corpora lutea with multiple ovulations?

1. dogs

2. cats

3. sheep

4. pigs

what is estrogen and progesterone derived from?

cholesterol

what type of receptors do estrogen and progesterone have?

intracellular receptors

what type of hormones are estrogen and progesterone?

sex steroid hormones

how is estrogen and progesterone transported in the animal?

bound to blood in proteins

what controls progesterone?

hypothalamic-pituitary control

how does progesterone influence the uterus?

1. stimulate products to support development of embryo

2. inhibit motility of uterus

how does progesterone influence the mammary gland?

promotes aveolar development

MCQ: what type of hormones are LH and hCG?

peptide

luteolysis

process where CL undergoes regression and death

PGF2alpha

inhibits progesterone synthesis and opens Ca2+ channels = apoptosis

declining progesterone activates…

new estrous cycle

MCQ: what triggers the switch from negative to positive feedback by estrogen on the hypothalamic-pituitary axis during the estrous cycle?

high sustained estrogen concentration

What are the phases of the estrous cycle and which are follicular vs luteal?

1. Follicular phase (proestrus and estrus)

2. luteal phase (metestrus and diestrus).

What triggers luteolysis and what hormone mediates it?

Oxytocin from the CL or posterior pituitary initiates prostaglandin F2α release from the endometrium, leading to luteolysis

what hormones are involved in proestrus?

FSH and estrogen

what are the key events of proestrus?

• follicles mature

• estrogen rises

• uterus thickens

during what stage of the estrous cycle will you see visible signs like vaginal bleeding or swelling?

proestrus

what stage of the estrous cycle is estrogen at peak levels?

estrus

what are the key events of estrus?

• female sexually receptive

• female can become pregnant

• ovulation occurs at end

what stage of the estrous cycle will progesterone begin to rise?

metestrus

what are the key events of metestrus?

• CL forms and secretes progesterone to support pregnancy

• female no longer sexually receptive

what stage of the estrous cycle is progesterone high?

diestrus

what are the key events of diestrus?

• CL secretes progesterone to maintain uterine lining

what will happen during diestrus if pregnancy did not occur in the female?

CL will start to regress and new follicular cycle will begin

what stage of the estrous cycle are there low levels of estrogen and progesterone?

anestrus

what are the key events of anestrus?

• period of reproductive inactive

• female not sexually receptive