Virtual Chicken

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Virtual Chicken

• The Female Reproductive Tract

Advanced Level
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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• Ovary Structure
• Outer cortex contain the ovarian follicles
• gt12000 follicles
• Oocytes
• Steroid producing cell layers
• Granulosa
• Theca
• Inner Medulla

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Virtual ChickenThe Female Reproductive Tract

• Ovarian Follicle

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Virtual ChickenThe Female Reproductive Tract
Time ova spends in each section

• 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

• Oviduct
• Fast Facts

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Virtual ChickenThe Female Reproductive Tract

• 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 (PGCs) that will become
  eggs or sperm have formed in the embryo before
  oviposition.
• PGCs circulate in the blood
• Migrate into the mesoderm and colonize gonadal
  ridge
• 96 hours into incubation PGCs migrate to left
  side if the embryo is genetically female
• Eventually forms the ovary

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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

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract
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Virtual ChickenThe Female Reproductive Tract
Yolk Formation and Maturation of the Ovum

• 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

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Virtual ChickenThe Female Reproductive Tract
Yolk Formation and Maturation of the Ovum

• 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

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Virtual ChickenThe Female Reproductive Tract
Yolk Formation and Maturation of the Ovum

• Proteins
• Apo-B, Apo-VLDL-II
• Vitellogenin
• Phosvitin, Lipovitellin
• Plasma proteins
• Albumin
• IgG (antibodies to protect chick)

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Virtual ChickenThe Female Reproductive Tract
Yolk Formation and Maturation of the Ovum

• Lipids
• Triglycerides (70 75)
• Can be somewhat manipulated by changing hens
  diet
• Mainly palmitic, oleic acids
• Phospholipids (20-25)
• Cholesterol (only 4!)

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Virtual ChickenThe Female Reproductive Tract
Yolk Formation and Maturation of the Ovum

• 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

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract
Hormone production by follicles

• 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

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Virtual ChickenThe Female Reproductive Tract
Endocrine Control of Development

• Follicle stimulating hormone (FSH)
• Granulosa cell differentiation
• Progesterone production
• Luteinizing hormone (LH)
• Androgens
• Estrogens

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Virtual ChickenThe Female Reproductive Tract
Post Ovulatory Follicle

• 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 dont get
  pregnant
• Gone by 6 days

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Virtual ChickenThe Female Reproductive Tract
Ovulatory Cycle

• 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

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• Egg Formation
• Starts in a hens 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

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Virtual ChickenThe Female Reproductive Tract

• 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

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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

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• Cuticle
• Protein
• Plugs pores

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Virtual ChickenThe Female Reproductive Tract

• Shell Formation
• Two Main components of egg shell mineral
• Calcium from diet
• Carbonate from respiration

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• Measuring Shell Quality
• Appearance
• Rough Shell
• Misshapen
• Shell thickness
• Shell strength
• Shell porosity

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Virtual ChickenThe Female Reproductive Tract

• 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

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Virtual ChickenThe Female Reproductive Tract

• The End
• Questions?