  Angiogenesis is the complex process by which new blood vessels develop from
an existing vasculature in order to supply nutrients and/or metabolites to
tissues, playing a fundamental role in many physiological and pathological
conditions such as embryogenesis and tissue repair or tumour growth. Here we
analysed the \textit{in-vitro} angiogenic process from the perspective of the
monolayer to understand the role of the interaction between the surrounding
endothelial monolayer, the sprouting and the mechanics. First we noticed that
the VEGF (Vascular Endothelial Growth Factor) promotes a jamming/unjamming
transition that allows the fluidisation of the monolayer by measuring the shape
index factor. Next, we measured the density field over the monolayer and
realised that the flow of cells manifests strong similarities with the
evacuation process where the flock of cells can flow or stuck, defining a
convergent channel. Based on these novel observations we propose a mathematical
model to describe the effects of unjamming and reorientation of a flock of
cells which flow from the monolayer towards the early capillary structure. This
model is developed into the framework of the continuum mechanics in which we
consider the endothelial monolayer as an active biopolymer film where the
nematic order emerges in the unjammed phase promoted by the VEGF activation. To
test the proposed ideas we implement the developed coupled equations into a
finite element code and describe, with a simplified geometry, the flow effect
and cells orientation from the monolayer to the capillary. In this work, we
propose an interpretation, from the top of the endothelial monolayer, based on
experimental observations and theoretical arguments to think the angiogenesis.
