Female Reproductive System

Gestation (mammalian)

internal embryonic development and placental nutrient exchange require highly adapted uterine structures

Oviposition/Incubation (avaian)

external embryonic development and maternal nutrient packing (yolk/albumen) require a highly specialized manufacturing assembly line

Ovaries

responible for gamete production >> ooctye release & steroidogensis

Oviducts

fertilization site >> infundibulum catches released ova

Uterus

fetal incubation >> embryo implantation and nourishment

Cervix

protective barrier >> annular rings protect uterine cavity

GnRH (gonadotropin-releasing hormone)

secreted by hypothalamus >> triggers pituitary LH & FSH release

FSH and LH (follicle stimulating hormone and luteinizing hormone)

secreted by pituitary gland >> drives folllicular growth & ovulation

Estrogen (E2)

produced by developing follicles >> induces standing estrus bhavior

P4 (progesterone)

corpus luteum >> maintains pregnancy

Mammalian ovaries

folliculogenesis, ovulation & progesteron secretion (corpus luteum)

Mammalian oviducts

site of fertilization (ampullary-isthmic junction) and early embryonic transport

Mammalian uterus

bicornuate structure (body & horns); site of placental attachment and fetal development

Mammalian cervix

physical barrieer; species-specific landmarks >> protects the sterile uterus from the non-sterile vagina >> transports sperm & acts as birth canal

Annular rings (cervix)

cow and ewe

Interlocking cushions (cervix)

sow

Longitudinal folds (cervix)

mare

Mammalian vagina & vulva

copulatory organ & external genitalia >> passage between cerivx & vulva is the vagina

Polytocous (litter-bearers/swine)

logn, convouluted uteine horns (2-3 ft long) to maxmize surface area for 10-15 placentas

Monotocous (single-bearers/ cattle & horses)

shorter horns, larger uterine body; designed to support one massive fetus

Bovine anatomical features

3-4 annular rings, bicornuate (moderate) uterine horns, accepts fibroelastic penis (sigmond flexure, bull)

Porcine anatomical features

corkscrew interlocking pads, bicornuate uterine horns (long horns), accepts spiral tip fibroelastic penis (boar)

Ovine/Caprine anatomical features

complex annular rings, bicornuate unterine horns (curved), accepts filiform process present penis (ram, buck)

Equine antaomical features

longitudinal folds, bipartite unterine horns (prominent body), accpects vascular erection type penis (stallion)

What is the estrous cycle?

The recurring set of physiological & behavioral changes driven by reproductive hormoes in females

What does the estrous cycle do?

It prepares the body for ovulation and potential pregnancy

Estrus

Time periods when females are receptive to mating

What phase of the menstrual cycle is estrogen dominant?

Follicular Phase

What hormone drives the recruitment and maturation of ovarian follicles?

FSH (Follicle Stimulating Hormone)

What do developing follicles produce in increasing amounts during the Follicular Phase?

Estradiol (E2)

What triggers a positive feedback loop on the hypothalamus/pituitary during the Follicular Phase?

Peak Estradiol

What does the positive feedback loop caused by peak Estradiol induce?

A massive LH Surge that induces ovulation

What transforms from a ruptured follicle during the Luteal Phase?

The Corpus Luteum (CL)

What hormone is primarily secreted by the Corpus Luteum?

Progesterone (P4)

What is the role of Progesterone in the endometrium during the Luteal Phase?

It prepares the endometrium for embryo implantation.

What effect does Progesterone have on uterine activity during the Luteal Phase?

It maintains uterine quiescence.

How does Progesterone affect GnRH, LH, and FSH during the Luteal Phase?

It exerts negative feedback on GnRH, LH, and FSH.

Luteolysis

Non-pregnant uterus releases Prostaglandin

F2α (PGF2α) to regress th CL, dropping P4 & allowing new follicular phase to begin

Estrous in cattle

21 day cycle, 16-18 hr estrus, ovulate 20-40 hrs after starting

Estrous in swine

21 day cycle, 3 day estrus, ovulate 24hr before end of estrus

Estrous in sheep

16 day cycyle, 30hr estrus, ovulate near end of cycle

Estrous in goats

22 day cycle, 2.5 day estrus, ovulate near end of cycle

Estrous in horses

22 day cycle, 6 day estrus, ovulate 24-48 before end of cycle

Cattle gestsation length

282 days

Swine gestation length

114 days

Sheep/Goat gestation length

150 days

Horse gestation length

336 days

Parturiton (positive feedback loop)

The cycle only stops when the baby is born and the

stimulus (stretching) is removed.

What is the asymmetry in the avian female reproductive tract?

Only the left ovary and oviduct are fully developed and functional.

What does the ovary in the avian female reproductive tract contain?

Thousands of follicles at varying maturity stages.

What is the process of yolk development in avian ovaries?

Hierarchical yolk development.

What is the function of the eggshell and cuticle in an avian egg?

The eggshell and cuticle form a calcified porous layer enabling gas exchange (O2 in, CO2 and H2O out).

What are the shell membranes in an avian egg?

The shell membranes are inner and outer membranes that separate at the blunt end post-laying to form the Air Cell.

What is the primary function of the yolk in an avian egg?

The yolk serves as the primary nutrient and lipid reserve enclosed by the vitelline membrane.

What does the germinal disc indicate in an avian egg?

The germinal disc serves as a fertility indicator.

What is the difference between a blastoderm and a blastodisc in an avian egg?

A blastoderm (fertile) is a doughnut-shaped ring with a clear center, while a blastodisc (infertile) is a solid, unorganized white spot.

What is the composition and function of albumen in an avian egg?

Albumen (egg white) consists of dense and thin protein layers providing water, cushioning, and antimicrobial protection (lysozyme).