Structure and Characteristics of Venule - Post-capillary venules have a single layer of endothelium surrounded by a basal lamina. - Size of post-capillary venules is between 10 and 30 micrometers. - Post-capillary venules do not contain smooth muscle but are supported by pericytes. - When post-capillary venules increase in diameter to 50μm, they become muscular venules. - Venules have thinner walls than arterioles due to the poorly developed middle layer.

Short Portal Venules - Short portal venules exist between the posterior pituitary and the anterior pituitary lobes. - They facilitate rapid hormonal exchange via the bloodstream. - Confluent interlobevenules provide blood flow between pituitary lobes, allowing for sharing of information. - Short portal venules play a role in the anatomical connection between pituitary lobes. - They provide a pathway for communication within the pituitary gland.

High Endothelial Venules - High endothelial venules have an endothelium made up of simple cuboidal cells. - Lymphocytes exit the bloodstream and enter the lymph nodes through these venules during infections. - Compared to arterioles, high endothelial venules are larger and have a weaker muscular coat. - They are specialised venules involved in immune response and lymphocyte trafficking. - High endothelial venules are the smallest united common branch in the human body.

Related Concepts - Arteriole - Surface chemistry of microvasculature - Microcirculation

References - Standring, Susan (2016). Gray's Anatomy: The Anatomical Basis of Clinical Practice (41st ed.). Philadelphia: ISBN 9780702052309. - Woods, Susan (2010). Cardiac Nursing. New York: Lippincotts. ISBN 9780781792806. - Gross, PM; Joneja, MG; Pang, JJ; Polischuk, TM; Shaver, SW; Wainman, DS (1993). Topography of short portal vessels in the rat pituitary gland: A scanning electron-microscopic and morphometric study of corrosion cast replicas. Cell and Tissue Research. 272 (1): 79–88. doi:10.1007/bf00323573. PMID8481959. S2CID23657199.