Virtual Chicken

1. Virtual Chicken The Female Reproductive Tract Advanced Level

2. Role of the Avian Female Reproductive Tract Manufacture ova and egg components Ova Yolk Albumen Shell Site of fetilization Sperm is stored and transported within the female tract Virtual ChickenThe Female Reproductive Tract

3. Ovary -- 2 functions Produce ova germinal disk - will become the embryo when fertilized Yolk-nutrition for the growing embryo Endocrine function Estrogen, androgens, and progesterone Oviduct Transport Packaging Virtual ChickenThe Female Reproductive Tract

4. Ovary Structure Outer cortex contain the ovarian follicles >12000 follicles Oocytes Steroid producing cell layers Granulosa Theca Inner Medulla Virtual ChickenThe Female Reproductive Tract

5. Ovarian Follicle Virtual ChickenThe Female Reproductive Tract

6. Infundibulum ≤ 1 hour Captures ova Secretes outer membrane First albumen Magnum 2 – 3 hours Albumen Avidin Ovalbumin Lysozyme Isthmus ± 1 hour Inner Outer Shell Membranes Shell gland 20 – 26 hours Plumping Shell deposition Vagina Just a few minutes Sperm storage Cuticle Pigment Oviduct Fast Facts Virtual ChickenThe Female Reproductive Tract Time ova spends in each section

7. Embryonic Origin of the Ovary Before hatching, the embryo is in an “indifferent” stage having the beginnings of both male and female reproductive organs. Primordial germ cells (PGC’s) that will become eggs or sperm have formed in the embryo before oviposition. PGC’s circulate in the blood Migrate into the mesoderm and colonize “gonadal ridge” 96 hours into incubation: PGC’s migrate to left side if the embryo is genetically female Eventually forms the ovary Virtual ChickenThe Female Reproductive Tract

8. Virtual ChickenThe Female Reproductive Tract Development of the Ovary • Cortex – outer cell layers of embryonic ovary • PGCs • Medulla-inner cell layers • PCGs and connective tissue • First sex specific differentiation is thickening of the cortex at 7 days of age • Proliferation of PGCs • Right ovary stops developing and degenerates • Some medullary tissue may persist in right oviduct • Can form ovotestis if the ovary ever becomes damaged • Left ovary continues to develop

9. Oviduct Embryo has both male (Wolfian) and female (Mullerian) reproductive duct system. Mullerian duct becomes the Oviduct Wolfian duct may persist as a vestigial structure Virtual ChickenThe Female Reproductive Tract

10. Virtual ChickenThe Female Reproductive Tract

11. White yolk Core of the yolk Female pronucleus (female genetic material) Yellow yolk Deposited in layers on white yolk Yellow because of fat soluble pigments from feed Female pronucleus rises through yellow yolk on stalk Virtual ChickenThe Female Reproductive Tract Yolk Formation and Maturation of the Ovum

12. Rapid deposition of yellow yolk for 7-10 days prior to ovulation Yolk material is formed as droplets or spheres much like fat droplets in milk. Yolk formation is estrogen dependent Yolk components formed in liver Particles of “Very Low Density Lipoproteins” (VLDL) 12% protein 88% lipid Virtual ChickenThe Female Reproductive Tract Yolk Formation and Maturation of the Ovum

13. Proteins Apo-B, Apo-VLDL-II Vitellogenin Phosvitin, Lipovitellin Plasma proteins Albumin IgG (antibodies to protect chick) Virtual ChickenThe Female Reproductive Tract Yolk Formation and Maturation of the Ovum

14. Lipids Triglycerides (70 – 75%) Can be somewhat manipulated by changing hen’s diet Mainly palmitic, oleic acids Phospholipids (20-25%) Cholesterol (only 4%!) Virtual ChickenThe Female Reproductive Tract Yolk Formation and Maturation of the Ovum

15. 4 membranes enclose the yolk (from inside to out) Vitelline membrane Perivitelline membrane Middle continuous layer Extravitelline layer Blastodisc Location of the embryo Floats on white yolk Virtual ChickenThe Female Reproductive Tract Yolk Formation and Maturation of the Ovum

16. Follicular Hierarchy Follicles develop in an orderly hierarchy Control of the order of follicle development is not well understood Recruitment of follicles into the hierarchy: May be adrenal regulated The Adrenal glands are essentially embedded in ovary Nerve endings on thecal cells If nerves are cut: many follicles mature at once Virtual ChickenThe Female Reproductive Tract

17. Steroidogenesis: Controlled by pituitary hormones: FSH and LH Estrogen and androgen Estrogen production dominates as the follicle begins to accumulate yolk then declines as follicle nears maturation Androgen and progesterone production maximum about 3 days prior to ovulation Androgen production ends at just before ovulation Progesterone production continues after ovulation Virtual ChickenThe Female Reproductive Tract Hormone production by follicles

18. Follicle stimulating hormone (FSH) Granulosa cell differentiation Progesterone production Luteinizing hormone (LH) Androgens Estrogens Virtual ChickenThe Female Reproductive Tract Endocrine Control of Development

19. In mammals, the parts of the follicle remaining after ovulation become the “corpus luteum” and continues to produce progesterone to support pregnancy In birds, steroidogenic capacity is retained by the postovulatory follicle for 24 hours Probably has no function since birds don’t get pregnant Gone by 6 days Virtual ChickenThe Female Reproductive Tract Post Ovulatory Follicle

20. Interval between consecutive ovulations Controlled by circadian rhythms Clock reset at dusk: open period for oviposition begins 15 hours after dusk Open period: Oviposition and ovulations occur during an 8 hour period Ovulation 30 – 45 minutes after oviposition LH release controls ovulation Virtual ChickenThe Female Reproductive Tract Ovulatory Cycle

21. Ovulation Structure of the follicle causes expulsion of the ovum Stigma: avascular area Collagen structure weaker Proteolytic enzymes -digest and weaken the membranes Myofibrils - contract and cause the membranes to rupture Virtual ChickenThe Female Reproductive Tract

22. Functions of the Egg Container Holds and protects the organic and inorganic materials required to produce the chick Controlled environment Controls entry of microorganisms, gas exchange, moisture loss Virtual ChickenThe Female Reproductive Tract

23. Egg Formation Starts in a hen’s ovary Ovum Ovum is surrounded by the vitelline membrane produced by the ovary Ovum stores nutrients as yolk granules for use by the embryo White yolk Most is located directly below the nucleus Yellow yolk Seven or eight day before the ovum is ovulated, yellow and white yolk are laid down in layers Virtual ChickenThe Female Reproductive Tract

24. Eggshell Multiple layers function together to protect the embryo Provide the correct environment for embryonic development Inner shell membrane In contact with albumen/chorioallantois Nonfibrous on surface facing embryo Fibous on outer surface Virtual ChickenThe Female Reproductive Tract

25. Calcite crystals Mammilary cores Outer shell membrane Virtual ChickenThe Female Reproductive Tract Eggshell • Capable of withstanding 100 psi internal pressure • Mammillary layer • Palisade layer • 50% of the strength of the shell • Columns of calcium carbonate (calcite) • Organic matrix • Surface crystal layer • Pores

26. Outer Shell Membrane Stacked on top of inner shell membrane, except at air cell Mat of fibers, intermeshed with fibers of inner membrane Mammillary cores Virtual ChickenThe Female Reproductive Tract

27. Cuticle Protein Plugs pores Virtual ChickenThe Female Reproductive Tract

28. Shell Formation Two Main components of egg shell mineral Calcium – from diet Carbonate – from respiration Virtual ChickenThe Female Reproductive Tract

29. Source and Deposition of Calcium Eggshell takes more calcium than hen has in blood and is placed on the shell faster than hen can absorb calcium from the gut Hen derives calcium for eggshell from diet and from stored sources Sort term calcium storage in crop Long term calcium storage in bone Medullary bone - rapidly mobilizable calcium source Virtual ChickenThe Female Reproductive Tract

30. Source and Deposition of Calcium Ionized (free) calcium is taken from blood, deposited on eggshell Blood calcium replaced by calcium released from medullary bone Shell gland maintains a supersaturated calcium solution so that calcium precipitates out on sell membranes Complex endocrine mechanisms to control calcium utilization Dihydroxyvitamin D Parathyroid hormone Virtual ChickenThe Female Reproductive Tract

31. Source and Deposition of Calcium Carbonate derived from CO2 from cell respiration Carbonic anhydrase is the enzyme responsible (mostly in red blood cells) Water and CO2 form bicarbonate and free H+ ions Carbonate secreted in shell gland to form egg shell H+ ions diffuse back into blood and lower blood pH (blood becomes acidic) Increases respiration Blows off CO2 + H+ (blood becomes alkaline) Dietary and environmental conditions can alter this and cause problems with eggshell formation. High temperatures High breathing rate (panting) to cool - blows off too much CO2 Acidic diet or water Alkaline diet or water Metabolic Acidosis Virtual ChickenThe Female Reproductive Tract

32. Egg Shell Quality Shell quality is associated with hatchability  Shell quality  Hatchability Shell quality declines the longer a hen is in production  Shell quality  Hatchability Season of the year, hen strain, environment temperature, nutrition Hot weather =  Shell quality Poor nutrition =  Shell quality Virtual ChickenThe Female Reproductive Tract

33. Measuring Shell Quality Appearance Rough Shell Misshapen Shell thickness Shell strength Shell porosity Virtual ChickenThe Female Reproductive Tract

34. Interior Egg Quality Tremulous air cells Albumen quality Haugh units Albumen height corrected for egg size Higher Haugh unit = better hatchability Haugh units should be 80 or higher for good hatch Loss in albumen height due to loss of specific protein: ovomucin Virtual ChickenThe Female Reproductive Tract

35. The End Questions? Virtual ChickenThe Female Reproductive Tract