Histology and Cytology of the Aortic Valve*
Mano Thubrikar in The Aortic Valve, 2018
The aortic root consists of three aortic sinuses, which are hemispherical, outwardly ballooned regions of the wall, and the leaflet anchorages that partially surround them. Two of the three sinuses include the orifices of the coronary arteries. In the sinuses, which expand and contract with each cardiac cycle, tissues of the aortic root are disposed inconstantly into the three tunics that conventionally characterize arterial vessels, the intima, media, and adventitia. The thin tunica intima consists of an endothelial lining and a layer of intermixed collagenous and elastic tissue. The presence of elastic bands, similar to those of the tunica media, makes it difficult to separate the intima from the media. The much thicker tunica media in much of the aortic root is composed of the alternating layers of smooth muscle and elastic tissue mainly responsible for the elasticity of the sinuses. Various amounts of collagenous fibers are intermixed into the musculoelastic strata, providing some mechanical strength for the sinus portions of the wall. An adventitial tunic is a variable feature of the wall, consisting in places of a relatively loose, even fatty, connective tissue but displaced elsewhere by the insertions of broad bands of atrial and ventricular cardiac muscle. An outer tunic is nonetheless important for sinus function, especially for providing an external blood circulation for the medial musculature through vasa vasorum.
Cardiovascular System:
Michel R. Labrosse in Cardiovascular Mechanics, 2018
The blood vessel wall is made up of three layers: the tunica intima, the tunica media, and the tunica externa (Figure 1.7). The innermost layer, the tunica intima, is made up of a basement membrane and endothelium, which is in contact with the blood as the blood moves through the blood vessel lumen. The endothelial cells secrete chemicals such as endothelin and nitric oxide, which can trigger a local vasoconstriction or vasodilation. The endothelium also provides a smooth surface that minimizes the friction at the wall. The basement membrane and the internal elastic lamina make up the rest of the tunica intima. The network of collagen fibers within the basement membrane and the layers of elastic fibers within the lamina provide tensile strength to the wall while also allowing for stretching and recoiling.
Morphologic features and pathology of the elderly heart
Wilbert S. Aronow, Jerome L. Fleg, Michael W. Rich in Tresch and Aronow’s Cardiovascular Disease in the Elderly, 2019
Thickening of the tunica intima is seen in practically all arteries of the human body and has been described in association with aging (Figure 2.3). Originally, the intima consists of only a thin layer of endothelial cells lining the vascular lumen, with minimal subendothelial connective tissue. With aging, smooth muscle cells migrate from the tunica media and accumulate in the intima. The cells undergo a switch from a differentiated contractile to a synthetic phenotype (20). Cytoskeletal markers are reduced and cell morphology becomes more rounded, owing to an increase in rough endoplasmic reticulum and other cytoplasmic organelles. Proliferative behavior in response to growth factors increases. Slowly, over time, this proliferation results in intimal thickening. Larger arteries, such as the aorta, are the most affected. Both peripherally and in the coronary vasculature, this phenomenon plays a significant role in the development of cardiovascular diseases such as hypertension and atherosclerosis.
Targeting VCAM-1: a therapeutic opportunity for vascular damage
Published in Expert Opinion on Therapeutic Targets, 2023
Mayarling F Troncoso, Magda C Díaz-Vesga, Fernanda Sanhueza-Olivares, Jaime A Riquelme, Marioly Müller, Luis Garrido, Luigi Gabrielli, Mario Chiong, Ramon Corbalan, Pablo F Castro, Sergio Lavandero
The cardiovascular system includes the heart and blood vessels that pump and deliver blood throughout the body. Blood vessels are structured in three layers: the tunica intima, media, and adventitia. The tunica intima, or inner layer, comprises endothelial cells (EC) in contact with the blood. The tunica media or medial layer is formed mainly by vascular smooth muscle cells (VSMC) and the extracellular matrix, such as collagen and elastin, that regulates vascular tone and the integrity of vessels. In capillaries, the medial layer does not contain VSMC, but pericytes form a thin wall that facilitates the transport of blood components [3]. The adventitia layer, or outer layer, comprises fibroblasts, nerves, and small arteries (Vasa vasorum) that deliver nutrients to this layer [4].
Berberine alleviates monosodium glutamate induced postnatal metabolic disorders associated vascular endothelial dysfunction in newborn rats: possible role of matrix metalloproteinase-1
Published in Archives of Physiology and Biochemistry, 2022
Abeer A. Abo Zeid, Ibrahim Rowida Raafat, Abeer G. Ahmed
Light microscopic examination of H&E stained aortic sections of control rats, revealed three layers from inward outward. The 1st layer was the tunica intima with its regular lining endothelial cells. The next layer appeared was the tunica media that showed smooth muscle cells with their nuclei appeared dark blue arranged in concentric layers alternating with collagen and elastic fibres. The third layer was the tunica adventitia which consisted of loose connective tissue containing elastic and collagen fibres (Figure 2(A)). Mallory’s trichrome stained sections showed regular distribution of connective tissue in the intima and in the media (Figure 2(B)).Sudan III stained sections of control showed only one orange brown fat cell in the media (Figure 2(C)). Also, Van Geison stained sections of control showed regularly arranged brown elastic fibres all through the media (Figure 2(D)).
An unusual “venous circle” of the internal mammary vein encountered during microvascular anastomosis and implications for practice
Published in Case Reports in Plastic Surgery and Hand Surgery, 2020
S. Samaras, M. A. McKelvie, G. Oni, C. M. Malata
Secondly, modifying the ring by ligating, excluding and excising one limb of the bifurcation in order to create a single continuous vein onto which a single donor vessel can be anastomosed potentially raises the risk of creating additional sites of turbulence at the points of ligation in the remaining limb. This would increase the risk of thrombogenesis or luminal narrowing and thus the chance of venous outflow problems. Lastly and perhaps most importantly, anastomosing two antegrade veins can be seen as advantageous as there are reports of retrograde anastomoses having an increased thrombotic risk and decreased flow rate compared to the antegrade [15]. Given the aforementioned reasons, the authors propose that by anastomosing within the ring, respecting the observed anatomy and the natural contour of the converging veins, this would preserve the integrity of the tunica intima promoting normal laminar blood flow.