title: Structure and hemodynamics of vascular networks in the chorioallantoic membrane of the chicken.
abstract: The chick chorioallantoic membrane (CAM) is extensively used as an in vivo model. Here, structure and hemodynamics of CAM vessel trees were analyzed and compared with predictions of Murray's law. CAM microvascular networks of Hamburger-Hamilton stage 40 chick embryos were scanned by videomicroscopy. Three networks with ∼3,800, 580, and 480 segments were digitally reconstructed, neglecting the capillary mesh. Vessel diameters (D) and segment lengths were measured, and generation numbers and junctional exponents at bifurcations were derived. In selected vessels, flow velocities (v) and hematocrit were measured. Hemodynamic simulations, incorporating the branching of capillaries from preterminal vessels, were used to estimate v, volume flow, shear stress (τ), and pressure for all segments of the largest network. For individual arteriovenous flow pathways, terminal arterial and venous generation numbers are negatively correlated, leading to low variability of total topological and morphological pathway lengths. Arteriolar velocity is proportional to diameter (v∝D1.03measured, v∝D0.93modeling), giving nearly uniform τ levels (τ∝D0.05). Venular trees exhibit slightly higher exponents (v∝D1.3, τ∝D0.38). Junctional exponents at divergent and convergent bifurcations were 2.05 ± 1.13 and 1.97 ± 0.95 (mean ± SD) in contrast to the value 3 predicted by Murray's law. In accordance with Murray's law, τ levels are (nearly) maintained in CAM arterial (venular) trees, suggesting vascular adaptation to shear stress. Arterial and venous trees show an interdigitating arrangement providing homogeneous flow pathway properties and have preterminal capillary branches. These properties may facilitate efficient oxygen exchange in the CAM during rapid embryonic growth.
authors.affiliation: Department of Physiology, Charité Berlin, Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Maibier
authors.affiliation: Department of Physiology, Charité Berlin, Berlin, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Reglin
authors.affiliation: Department of Physiology, Charité Berlin, Berlin, Germany.
authors.forename: Bianca
authors.initials: B
authors.lastname: Nitzsche
authors.affiliation: Department of Physiology, Charité Berlin, Berlin, Germany.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Xiang
authors.affiliation: Department of Physiology, Charité Berlin, Berlin, Germany.
authors.forename: Wen Wei
authors.initials: WW
authors.lastname: Rong
authors.affiliation: Department of Physiology, Charité Berlin, Berlin, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Hoffmann
authors.affiliation: Institute of Anatomy, University of Bern, Bern, Switzerland; and.
authors.forename: Valentin
authors.initials: V
authors.lastname: Djonov
authors.affiliation: Department of Physiology, University of Arizona, Tucson, Arizona.
authors.forename: Timothy W
authors.identifier: 0000-0002-0176-5502
authors.initials: TW
authors.lastname: Secomb
authors.affiliation: Department of Physiology, Charité Berlin, Berlin, Germany; Deutsches Herzzentrum Berlin, Berlin, Germany; axel.pries@charite.de.
authors.forename: Axel R
authors.initials: AR
authors.lastname: Pries
mesh_terms: D000818:Animals; D001158:Arteries / Q000033:anatomy & histology / Q000502:physiology*; D001160:Arterioles / Q000033:anatomy & histology / Q000502:physiology*; D001783:Blood Flow Velocity; D002196:Capillaries / Q000033:anatomy & histology / Q000502:physiology*; D002642:Chick Embryo; D049033:Chorioallantoic Membrane / Q000098:blood supply*; D003198:Computer Simulation; D006400:Hematocrit; D006439:Hemodynamics; D008955:Models, Cardiovascular; D013314:Stress, Mechanical
keywords: Murray's law; angiogenesis; cardiovascular modeling; chick embryo; microcirculation