PP11 Fetal Development, Growth and Physiology 2

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PP11Fetal Development, Growth and Physiology 2

• Chapter 3 pg 43-62
• ANS 3043
• University of Florida
• Dr. Michael J. Fields

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Nutritional Effects

• Increased surface area and completion of the
  chorion attaching to the endometrium for optimal
  transfer of nutrients
• Maximal fetal weight accumulation and protein
  deposition

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Nutritional Effects

• Constraints and external stimuli have the
  greatest effect on fetal growth
• Severe maternal nutrient restriction can have
  negative effect on fetal growth
• Dependent on body energy reserves of mother
• Excess nutrient intake can increase fetal weight

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Environmental Effects

• Cold Environment
• Increases energy requirements of dam
• Increases metabolism of body energy reserves that
  may be required if nutrient requirements are not
  met
• Warm Environment
• Increases cooling requirement of dam
• Causes blood to flow away from placenta
• Decreased blood to placenta causes decreased
  nutrition to fetus and decreased fetal weight

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Effects of Fetal Number

• Polytoccous species model
• Interaction between fetal number and nutrition on
  fetal growth rate
• Nutrients partitioned between multiple fetuses
• Increased fetal number can amplify negative
  effects of poor nutrition and negative
  environmental effects

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Average Daily Growth During Gestation in Sheep
Elevated Diet
Decreased Nutrition
Rattery et al., 1974
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Relative Growth Rate During Gestation in Sheep
Rattery et al., 1974
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Organs Develop Early
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Cartilage gt Bone gt Muscle
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Vascularization of Bone
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Liver
Early Development
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Heart Early Beating Steady Growth
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Placentome of a Day 210 Bovine Fetus
Blood Vessel
Placentome
Caruncle
Cotyledon
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Fetal Skeletal Weights as Percentages of Total
Skeleton Weight in Sheep
Wallace, 1948
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Fetal Muscle Weights as Percentages of Total
Muscle in Sheep
Wallace, 1948
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Fetal Organ Weights as Percentages of Fetal Body
Weight in Sheep
Wallace, 1948
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DNA and ProteinDNA Ratios for Bovine Fetal Bicep
and Ovine Gastrocnemius Muscles
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Fetal Weights During Late Bovine Gestation
Anthony et al., 1986
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Fetal Tissue and Organ Growth

• General order of tissue development
• CNS gt Bone gt Muscle gt Fat
• Central Nervous System
• Fetal head is disproportionately large compared
  to body in early development

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Fetal Tissue and Organ Growth

• Organs
• Heart
• Maintains a constant relationship with fetal body
  weight
• Necessary to maintain blood flow because of
  increased placental and fetal size
• Same for kidney
• Liver
• Considerable development early and decreases late
  in gestation

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Fetal Tissue and Organ Growth

• Lungs
• Minimal growth early in gestation but increased
  growth in last half of gestation
• Not needed for oxygen exchange until birth
• Tissues
• Skeletal
• Initial development is cartilage miniatures
• Replaced with bone as gestation progresses

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Fetal Tissue and Organ Growth

• Muscle and Skeletal Groups Exhibit Differential
  Growth
• Lumbar region grows in constant relationship with
  rest of fetus (CNS and spinal cord development)
• Hind and forelimbs show increased growth late in
  gestation (both hyperplastic and hypertropic)
• Adipose
• Hyperplasia of preadipocytes is significant
• Hypertropic growth is minimal so there is little
  adipose deposition