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The PCA begins as a continuation of the posterior communicating artery in 70-90% of fetuses with the remainder of PCAs having a basilar origin. The fetal carotid origin of the PCA usually regresses as the vertebral and basilar arteries become dominant and it finds a new origin in the basilar artery.
The United Nations geoscheme is a system which divides 248 countries and territories in the world into six continental regions, 22 geographical subregions, and two intermediary regions. [1] It was devised by the United Nations Statistics Division (UNSD) based on the M49 coding classification . [ 2 ]
Both the ACA and MCA originate from the cerebral portion of internal carotid artery, while PCA branches from the intersection of the posterior communicating artery and the anterior portion of the basilar artery. The three pairs of arteries are linked via the anterior communicating artery and the posterior communicating arteries. All three ...
The following are central branches of the PCA, also known as perforating branches: Thalamoperforating and thalamogeniculate or postero-medial ganglionic branches: a group of small arteries which arise at the commencement of the posterior cerebral artery: these, with similar branches from the posterior communicating, pierce the posterior perforated substance, and supply the medial surfaces of ...
The political map of the world with all countries labeled and their boundaries marked. Items portrayed in this file depicts. copyright status. public domain. media type.
This is a list of countries and territories by the United Nations geoscheme, including 193 UN member states, two UN observer states (the Holy See [note 1] and the State of Palestine), two states in free association with New Zealand (the Cook Islands and Niue), and 49 non-sovereign dependencies or territories, as well as Western Sahara (a disputed territory whose sovereignty is contested) and ...
A subregion is a part of a larger geographical region or continent. Cardinal directions are commonly used to define subregions. There are many criteria for creating systems of subregions; this article is focusing on the United Nations geoscheme , which is a changing, constantly updated, UN tool based on specific political geography and ...
A world map is a map of most or all of the surface of Earth. World maps, because of their scale, must deal with the problem of projection. Maps rendered in two dimensions by necessity distort the display of the three-dimensional surface of the Earth. While this is true of any map, these distortions reach extremes in a world map.