Related Experiment Videos
Tissue PO2 and growth rate in early chick embryos
H J Meuer1, V Hartmann, S Jopp
1Medizinische Hochschule Hannover, Zentrum Physiologie, FRG.
Insights
Early chick embryo growth shows the head develops faster than the trunk. This is linked to higher oxygen levels and blood vessel density in the head, crucial for embryonic development.
Area of Science:
- Developmental Biology
- Embryology
- Physiology
Background:
- Head growth outpaces trunk growth in early chick embryos (days 4-6).
- Tissue oxygen levels (PO2) vary significantly between embryonic head and trunk.
- Microvascular density differs between head and trunk, potentially impacting oxygen supply.
Purpose of the Study:
- To investigate the relationship between dry mass, tissue PO2, and microvascular density in chick embryo head and trunk.
- To understand how oxygen availability influences embryonic growth rates.
- To explore the role of microvascular structure in determining tissue oxygenation.
Main Methods:
- Measurement of dry mass, tissue PO2 distribution, and microvascular density in chick embryos (days 4-6).
- Comparison of parameters between embryonic head and trunk.
- Analysis of oxygen extraction from capillary blood by embryonic tissues.
Main Results:
- Embryonic head dry mass increased from 31% to 48% of total dry mass, indicating faster head growth.
- Mean tissue PO2 was significantly higher in the head than in the trunk.
- Microvascular density was significantly higher in the head compared to the trunk.
- Low tissue PO2 values (<5 Torr) were frequent, suggesting high oxygen extraction.
Conclusions:
- Embryonic growth rate is critically dependent on oxygen availability.
- Differences in microvascular bed structure likely cause variations in tissue PO2 and growth rates between head and trunk.
- Enhanced microvasculature in the head supports its faster development and higher oxygenation.
Abstract:
We determined dry mass, frequency distribution of tissue PO2 and microvascular density of head and trunk of early chick embryos between day 4 and day 6 of incubation. During this period the percentage of the dry mass of the head on total dry mass increased from 31% to 48% indicating that the head grows faster than the trunk. Tissue PO2 values ranged between zero and arterial PO2. About half of the numbers were less than 5 Torr. Mean tissue PO2 was significantly higher in the head than in the trunk. This was paralleled by a significantly higher microvascular density in the head. The high frequency of low tissue PO2 values found at each day at all measuring sites suggests that the embryonic tissue of both head and trunk extracts as much oxygen from the capillary blood as possible. Consequently, growth rate strongly depends on oxygen availability. Since the arterial PO2 is the same in the head and in the trunk (Meuer and Baumann, 1988), the diversity of tissue PO2 and growth rate found in this study is probably caused by differences in the structure of the microvascular bed resulting in variations of tissue blood perfusion, capillary transit time and diffusion distance.