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Tissue Structure and Function
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
Veins are elastic vessels that transport deoxygenated blood from tissues to the heart, ranging in size from 1 millimeter to 11.5 centimeters in diameter. Venules are the smallest veins in the body. They receive blood from the arteries via the arterioles and capillaries. The venules branch into larger veins, which eventually carry the blood to the largest vein in the body, the vena cava. The blood is then transported from the vena cava to the right atrium of the heart.
Cardiovascular System:
Published in Michel R. Labrosse, Cardiovascular Mechanics, 2018
The venules and veins move blood to the heart and, with the exception of the pulmonary vein, carry deoxygenated blood. Venules are the receiving vessels from the capillary beds and drain into the veins. Both the venules and veins are characterized by thin walls that are collapsible and have low pressures (10–15 mmHg). The postcapillary venules range in size from 10 to 50 µm, while the larger muscular venules are 50–200 µm in size. These venules are highly distensible and can act as blood reservoirs, with the ability to expand their blood volume by two to three times. When this blood is required by the circulation (e.g., during exercise), the smooth muscle in the muscular venules may contract and contribute to an increased venous return to the heart.
Identification of retinal diseases based on retinal blood vessel segmentation using Dagum PDF and feature-based machine learning
Published in The Imaging Science Journal, 2023
K. Susheel Kumar, Nagendra Pratap Singh
The eyes are the important organs in the human body, comprising more than two million cells and tissues. The light-sensitive tissues behind the eyes are called the retina, which captures the view and forwards towards the brain through nerves [1]. The variations in the blood vessels of the retina cause retina artery occlusion, diabetic Retinopathy, retinal vein occlusion, hypertensive Retinopathy etc. The variations in the retinal blood vessels (RBV) cause vision problems and must be detected early to prevent vision loss [2]. The variations in blood vessel types include arteries, arterioles, capillaries, venules and veins. The arteries possess a significant role in organ nourishment with blood and nutrients. Elastic and muscular are the two main forms of arteries. The arterioles render blood over the organs, mainly comprised of smooth muscles. The metabolites and nutrients are exchanged through thin capillary walls made up of a single endothelial layer. The venules are the smallest veins that obtain blood from capillaries for oxygen transfer. The blood flows from venules over the larger, thin-walled, less elastic veins. The inherent retinal disease (IRD) is the most common cause of severe vision problems; thus, early detection would minimize the risk of vision problems in family members [3]. Therefore, a deep insight into these issues is required to protect patients with retinal diseases. Diagnosis of vision complications is tedious; in some cases, only small variations occur between the affected and normal blood vessels [4]. Advances and screening methods are useful for identifying various retinal diseases [5].