Reproductive Physiology

Fallopius (1562)

discovered and described the Oviduct ~ where fertilization occurs

Coiter (1572)

discovered Corups Luteum ~ support pregnancy (Progesterone (ovary))

de Graaf (1672)

discovered the Antral Follicle ~ secondary follicle or Graafian Follicle

Dumas (1825)

proved that spermatozoa were the fertilization agents

Why Study Today?

improvement in animal reproductive performance → increased efficiency of food production + increased profitability

3% increase in repro rate would cause… 1 mil more beef calves/year, 3.2 mil more pigs/year, 3.7 mil more gallons milk/year

Dairy

MOE: days open

national average: 150 days

realistic goal: 110 days

cost/measure unit: $2 6/open days

Beef

MOE: % calf crop

national average: 86%

realistic goal: 95%

cost/measure unit: $350/open cow

Sheep

MOE: % lamb crop

national average: 108%

realistic goal: 175%

cost/measure unit: $100/open ewe

Swine

MOE: weaned pigs/sows

national average: 15 pigs/sows

realistic goal: 20 pigs/sows

cost/measure unit: $48/weaned pigs

Equine

MOE: % foal crop

national average: 60%

realistic goal: —

cost/measure unit: —

Asexual Reproduction

reproduction by mitosis (unicellular organisms)

advantages: simple/fast

disadvantages: no new gametes, can’t adapt to environmental change

Sexual Reproduction

reproduction by meiosis, fusion of male/female gametes (higher forms), separate sexes

advantages: new genotypes each generation

disadvantages: complex/long process

Oviparous

fish, amphibians, reptiles, birds

egg laying ~ embryonic development + possible fertilization occurs external of the body

Ovoviviparous

certain reptiles and fish

fertilization + embryonic/fetal development takes place within female reproductive tract ~live young are born (ex. rattlesnakes)

Viviparous

almost all mammals

fertilization + all embryonic development occurs within the female reproductive tract ~ birth live young

~ monotremes are the exception: egg laying mammals (platypus, spiny anteater)

Sexual Differentiation

phenotypic sex: sperm determines XY= make XX= female

abnormalities:

• X_: turner syndrom ~ develops as female but don’t grow normally

• XXY: klinefelters syndrom ~ developer as male but breasts may develop

Development of Reproductive Tract

developed in close proximity + at same time a renal system (kidneys) in embryo → testes/ovaries ~ by gonadle ridge (gonadogenesis = development of gonad)

• primordial germ cells originate in early embryonic yolk sac → form spermatagonism (sperm) or oogonia (eggs)

In Female, by 33% of pregnancy completion…

no TDF (Testis Determining Factor) → ovaries develop → no AMH (Anti-malarian Hormone)→ paramesonephric ducts become oviducts/uterus/cervix/parts of vagina → complete female repro tract

Intersex (Free Martin)

when heifer (xx) is born with a twin bull (xy) ~ share placenta fluids

• male (XY): reduced fertility

• female (XX): infertile (90% of time) because ovaries don’t develop properly

  • TDF gets into her developing repro tract + hinder → TDF/AMH (present in males) ~ make repro tract very small

Chorion

outermost embryonic membrane around the developing fetus (mammals, birds, and reptiles)

Amnion

thin innermost embryonic membrane around developing fetus (mammals, birds, and reptiles)

Layers of the Female Repro Tract (out→in)

1. Serosa: single layer flat squamous cells that cover~ protect

2. Muscularis (Myometrium):

   1. longitudinal smooth muscle layer

   2. circular smooth muscle layer

3. Endometrium

   1. Submuscoa: vary in thickness, blood vessels, nerves, lymphatics, support mucosa layer

   2. Mucosa: opening to glands - secretory layer of epithelium, different function based on location

      1. Caruncles: present in ruminants on uterine lining - placenta liner attachment

Broad Ligament Parts

suspend the female reproductive system in pelvic cavity

1. Mesovarium: suspends ovaries

   1. Hilus: where the Mesometruim meets the ovary

2. Mesosalphinx: suspends oviducts

3. Mesometrium: suspends uterus + all parts posterior to uterus

Broad Ligament Blood Vessels

1. Uterine Artery: blood supply to uterus

2. Utero-ovarian Artery: blood to supply to ovaries → in conjunction with Corpus Luteum

3. Caudel Uterine Artery: blood supply to vagina

Ovary Main Functions

1. Gametogenic: release Ova → egg

2. Endocrine → produces…

   1. progesterone + oxytocin = Corpus Luteum

   2. Estrogen = Graafian Follicle

   3. Inhibin

Ovary Morphology (shape/size)

1. Monotocous: give birth to 1-2 offspring

   1. kidney bean (mare): have ovulation Fossa → point of ovulation (1 follicle)

   2. almond shape (small/large ruminants): follicles can develop all over

2. Polytocous: birth multiple offspring

   1. ovary = lobulated (cluster of grapes) → sows, queens, bitches

3. Stage of Estrous Cycle impacts predominant ovary structures present

   1. follicular phase: follicles

   2. luteal phase: corpora lutea

Ovary Anatomy

1. Tunica Albuginea: thin white skin around ovary

2. Cortex (the party): contains over 1 million eggs

3. Medulla (the center): blood vessels, nerves, lymph

Follicular Phases

Primordial Follicle: Oocyte surrounded by single layer of Cuboidal cells

Secondary Follicle: 2-3 layers of Cuboidal cells, Oocyte developed Zona Pellpucida

• Zona Pellpucida: membrane surrounding Oocyte

Tertiary Follicle: have antrum (pool of fluid), clear to naked eye, produces estrogen because of Graafian Follicle

Follicle Ruptures…

ovulations occurs

Corpus Hemorrhagicum: bloody depression that develops into Corpus Luteum

Corpus Luteum Develops (yellow body in cattle) → produces Progesterone to promote pregnancy

OR

Corpus Albican: pale white scar on surface of ovary if egg isn’t fertilized

Ovarian Anatomy - Photo

Anatomy of the Graafian (Antral) Follicle

Oocyte/egg (genetic info) → Cumulus Oophorus (surround/protects egg) → Granulosa Cells (estrogen production/synthesis) → basement membrane (outermost membrane) → Theca cells (testosterone production)

Abnormal Graafian (Antral) Follicle

Cystic Follicle: Graafian follicle that doesn’t ovulate, so estrogen production in huge amounts → make animal always display signs of heat

• GNH (Gonadotropin-releasing Hormone): promotes ovulation/follicular rupturing ~ can be given to suppress heat/make follicle rupture

Ovum → Egg

can see with naked eye - 80-240 microns ~ largest cell in female body

contains: Zona Pellucida (sperm bind to during fertilization), perivitelline, vitelline membrane (genetic info)

Oviduct ~ MAMMALS

1. Infundibulum: funnel shaped opening with Fimbria (lace like) that catches the ova at ovulation

Ovary Hormone Production + Process

Theca Interna/Externa Cells (produce Testosterone (androgen)) → through basement membrane ~ Aromatase (enzyme) → Granulosa cell (estrogen ~ produced by making testosterone into estrogen by use of aromatase) → estrogen released

Hen Repro System stages

0 → ovary = cluster of follicles, left ovary develops → point of ovulation = suture line (prevents bleeding)

1. Infundibulum: 15 minutes ~ contracts + catches yolk (funnel) during ovulation, stores sperm cells for 1-2 weeks (if germinal disk is present than yolk will be fertilized)

2. Magnum: 3 hours ~ creates thick white (albumen) around yolk - longest section of oviduct

3. Isthmus: 1 ¼ hours: places inner + outer shell membranes, protects egg from bacteria, keeps eggs shape - narrow segments with tough layers, provides all nutrients for embryo

4. Uterus: 20 hours ~ egg is “plumped” → thin white is added, shell is added - egg is turned so large end comes out 1st

5. Vagina: minutes ~ secretes mucous to help expel egg

Total: 22-27 hours

Egg Anatomy

Why do Hens not develop a Corpus Luteum?

don’t develop a Corpus Luteum since eggs are laid externally + develop when passing through repro system a CP isn’t needed