The skin
C. Simon Herrington in Muir's Textbook of Pathology, 2020
The dermis contains two parallel, vascular plexuses, each with an ascending arterial and descending venous limb: (a) superficial vascular plexus at the junction of the papillary and reticular dermis, and (b) deep vascular plexus at the junction between the reticular dermis and subcutaneous tissue. The vascular plexuses are connected by arteriovenous anastomoses. Also present throughout the dermis are lymphatic channels that drain the excess tissue fluid. The dermis contains sensory and sympathetic autonomic nerves that vary significantly with anatomical site. The sensory nerve fibres may be free ending or associated with specialized nerve corpuscles. These cutaneous nerves convey the sensations of touch, pain, proprioception, and pressure. Sympathetic fibres innervate a variety of structures including sweat glands, blood vessel walls, and arrector pili muscle. Smooth muscle in the skin is represented by arrector pili and the wall of medium to large blood vessels. Striated muscle fibres are superficially located in the dermis in the head and neck region.
Venous anatomy and pathophysiology
Helane S Fronek in The Fundamentals of Phlebology: Venous Disease for Clinicians, 2007
The most feared complications of sclerotherapy are anaphylaxis and intra-arterial injection. Fortunately, these are both rare. Intra-arterial injection can occur even when ultrasound guidance is used. The danger areas for intra-arterial injection include the posterior medial malleolar region, perforators (with their accompanying perforating arteries), and the saphenofemoral and saphenopopliteal junctions, although the arteries at greatest risk in these latter areas are generally not the femoral or popliteal arteries. Instead, the external pudendal artery, a small vessel that can cross anterior to the great saphenous vein, and unnamed superficial arteries near the small saphenous vein are most frequently affected. Arteriovenous anastomoses may explain some cases of arterial injection.29
Upper Extremity Arterial Occlusive Disease
Sachinder Singh Hans, Alexander D Shepard, Mitchell R Weaver, Paul G Bove, Graham W Long in Endovascular and Open Vascular Reconstruction, 2017
Initially, the brachial artery is ligated just distal to the arteriovenous anastomosis above the elbow crease. This is followed by distal revascularization to restore arterial perfusion to the forearm and hand. The location of the proximal anastomosis of the distal revascularization bypass is the key variable for hemodynamic efficacy of the procedure. The anastomosis must be created 5-10 cm proximal to the arteriovenous anastomosis where there is normal systemic pressure to drive blood flow into the bypass and the arteriovenous communication. Intra-arterial pressure measurements help to select the optimum region for the proximal anastomosis. Distally, the bypass is anastomosed
Advances in thermal physiology of diving marine mammals: The dual role of peripheral perfusion
Published in Temperature, 2022
Arina B. Favilla, Markus Horning, Daniel P. Costa
What makes blubber the ideal insulator also makes it challenging for in vivo studies. Blubber is internal, which allows for blood to bypass this insulation when needed (Figure 3a). A complex microvasculature network exists within the skin and blubber of marine mammals [23,24,30–32]. Superficial vessels are associated with arteriovenous anastomoses. These structures allow fine-scale adjustment to blubber’s insulative and transmissive properties by either constricting or dilating to regulate peripheral perfusion. By effectively modifying their conductance, marine mammals control the characteristics of the thermal gradient (Figure 3b) and can maintain a high core body temperature while immersed in water [33,34]. Therefore, understanding the thermoregulatory strategies of diving marine mammals requires examining the physiological mechanisms that influence heat transfer at their periphery.
Subretinal Hemorrhage Complicating Retinal Angiomatous Proliferation in Tubercular Retinal Vasculitis
Published in Ocular Immunology and Inflammation, 2022
Aniruddha Agarwal, Kanika Aggarwal, Sabia Handa, Ashish Markan, Vishali Gupta
In our patient, FA revealed significant retinal capillary non-perfusion areas that could have been long-standing given the prolonged nature of the disease. The vascular alterations in our patient included retinal vascular anastomosis and significant venous looping. Multimodal imaging helped in establishing the cause of the dense submacular hemorrhage in our patient, confirming the diagnosis of stage 2 RAP.11–13 In conditions such as polypoidal choroidal vasculopathy (PCV) and neovascular AMD, combination therapy with anti-VEGF agents, rTPA and gas tamponade has been described as the first-line therapy.15,22 However, in our patient, we first aimed at displacing the submacular hemorrhage using rTPA and SF6 gas, and then assessing the macular structure and function before injecting intravitreal anti-VEGF agents. Since our patient had significant retinal atrophy after the hemorrhage was displaced, and the visual potential was limited, further therapy with anti-VEGF agents was not considered. Lee et al.23 evaluated 187 eyes of 135 patients diagnosed with RAP (based on multimodal imaging and features of intraretinal hemorrhages, intraretinal vascular anastomosis, and hyper-reflective intraretinal vascular complex). The authors studied the risk factors for developing subretinal hemorrhage in these eyes, and observed that the overall incidence of massive bleed was 9.6%. The authors concluded that presence of layered lamellar tissue under the RPE (leading to RPE ruptures) and involvement of retinal arterioles were contributing factors to developing subretinal hemorrhage.23 In our patient, the possibility of occult RPE tear could not be ruled out, and arteriovenous anastomosis could be demonstrated on multimodal imaging. In addition, the subretinal neovascular fronds could be fragile and bleed leading to submacular hemorrhage in our patient.
Ocular Manifestations in an Italian Cohort of Patients with Takayasu Arteritis
Published in Ocular Immunology and Inflammation, 2023
Rosanna Dammacco, Luca Cimino, Luca De Simone, Giovanni Alessio, Franco Dammacco
Takayasu retinopathy (TR), characterized by chronic ischemia, was staged according to the classification system of Uyama and Asayama30: stage 1) dilation of retinal veins; stage 2) microaneurysm formation, mostly in the posterior pole; stage 3) arteriovenous anastomosis, usually in the peripapillary area; stage 4) ischemic complications such as retinal neovascularization, iris rubeosis, proliferative retinopathy, vitreous hemorrhage, and neovascular glaucoma (Figure 1).
Related Knowledge Centers
- Anastomosis
- Circle of Willis
- Collateral Circulation
- Vein
- Circulatory System
- Blood Vessel
- Artery
- Circle of Willis
- Left Anterior Descending Artery
- Posterior Descending Artery
- Scapular Anastomosis