Drainage vein

The superior vena cava (SVC) is the primary drainage vein for blood return from the head, neck, and upper extremities. It is a relatively thin-walled vein that is particularly vulnerable to obstruction from adjacent tumor invasion or thrombosis. The obstruction leads to elevated venous pressure, although collateral veins partially compensate. This is one reason for the relatively slow onset of the classic symptoms of SVCS. In fact, 75% of patients have signs and symptoms for more than 1 week before seeking medical attention.15... 

Palpation Each treatment Palpation of the thrill by placing fingers up the vein from the anastomosis along the drainage vein to the chest wall A palpable continuous thrill felt through the entire vein, with higher intensity at the anastomosis The entire fistula is soft and easily compressible Presence of arterial pulse distal of the VA Absence of thrill occlusion of fistula Hyperpulsatile and firm/water - hammer compressed or occluded Weak thrill weak inflow Absence of radial pulse... 

The veins of skin are organized along the same lines as the arteries in that there are both subpapillary and subdermal plexuses [11]. The main arteriole communication to these is the capillary bed. Copious blood is passed through capillaries when the core body is either feverish or overheated, far more than needed to sustain the life force of the epidermis, and this rich perfusion lends a red coloration to skin. When there is opposite physiological need, the capillary bed is short-circuited as blood is passed directly into the venous drainage by way of the arteriovenous anastomoses. Fair skin noticeably blanches when this occurs. These mechanisms act in part to regulate body temperature and blood pressure. 

This technique, also referred to as the auto-perfused method after experiments by Windmuller and Spaeth [67] involves cannulation and drainage of a vein from an intestinal segment and donor blood replacement via a sustainable blood vessel (e.g. jugular vein). The most commonly reported site of cannulation is the mesenteric vein. Cannulation is performed as follows. A midline incision of 4 cm is made and an 8-12-cm segment of the ileum is located to... 

Vaseular drainage from the oral mueosa is prineipally by the lingual, faeial, and retromandibular veins. These veins open into the internal jugular vein and thus avoid first-pass metabolism. 

The liver is uniquely situated to process and distribute dietary nutrients because the venous drainage of the gut and pancreas passes through the hepatic portal vein before entry into the general circulation. Thus, after a meal, the liver is bathed in blood containing absorbed nutrients and elevated levels of insulin secreted by the pancreas. During the absorptive period, the liver takes up carbohydrates, lipids, and most amino acids. These nutrients are then metabolized, stored, or routed to other tissues. Thus, the liver smooths out potentially broad fluctuations in the availability of nutrients for the peripheral tissues. 

There are many different procedures used for pancreas transplantation, and there is no one standard protocol used in all transplant centers. The important considerations, however, are that the arterial blood flow supply to the pancreas and duodenal segment, and venous outflow from the pancreas via the portal vein should be adequate. The recipient s right common or external iliac artery is used to restore vascularization of the artery in the pancreas. The Y graft of the tissue is anastomosed end-to-side and the venous vascularization is performed either systemically or portally, but mostly it is done with systemic venous drainage. 

FIGURE 7.1 Schematic illustration of the venous drainage of the human rectum. Drugs absorbed in the inferior and middle rectal veins that drain the lower part of the rectum will be delivered preferentially to the systemic circulation, bypassing the liver and avoiding first-pass metabolism. (Illustrated with modification from Nishimura, M., et al. (Eds.), Shin-Gekakgaku, 5th ed., Nanzando, Tokyo, 1979, 583. With permission.)... 

The blood supply to the vagina is through the uterine arteries and the internal iliac artery. Blood returns to the venous system through veins that empty into the internal iliac vein. Lymphatic drainage is through the external and internal iliac lymph nodes and superficial inguinal lymph nodes. 

The suprachoroid is 30 pm in thickness and comprises thin interconnected lamellae of melanocytes, fibroblasts, and connective tissue fibers. These are separated by a thin space known as the suprachoroidal space. In this space hydrostatic pressure is a few mm of Hg lower than the IOP. The small gradient allows drainage of aqueous humor, through the tissue spaces of the ciliary muscles, into the suprachoroidal space. Venous drainage takes place through a series of large vortex veins each of these drains a sector of the choroid into the superior and inferior ophthalmic veins of the orbit. 

Functional disturbances within the spinal cord are caused by the venous congestion due to arteriali-zation and elevated pressure of the medullary veins (Aminoff et al. 1974). In addition, venous outlets are insufficient and thus reinforcing impairment of the venous circulation and chronic spinal hypoxia. In particular, Merland and coworkers (1980) introduced the concept of blocked venous drainage into the epidural space. 

AVMs of the perimedullary fistula type are direct AV shunts that are located on the ventral or dorsal surface of the spinal cord or the conus medullaris, usually in the thoracolumbar area, occasionally thoracic, and rarely cervical. Their location thus is intradural, intra- or extramedullary. They are always supplied by spinal cord vessels, either by the anterior spinal artery (ventrally) or by a posterolateral artery (dorsally), depending on their location. They drain into spinal cord veins (Fig. 17.12). Drainage may even ascend up to the foramen magnum or into the posterior fossa. 

The posterior cerebral artery supplies the occipital lobe and portions of the medial and inferior temporal lobe. The arterial supply of the spinal cord is derived from the vertebral arteries and the radicular arteries. The brain is supplied by the internal carotid arteries (the anterior circulation) and the vertebral arteries, which join at the pon tomedullary junction to form the basilar artery (collectively termed the posterior circulation). The brainstem is supplied by the posterior system. The medulla receives blood from branches of the vertebral arteries as well as from the spinal arteries and the posterior inferior cerebellar artery (PICA). The pons is supplied by paramedian and short circumferential branches of the basilar artery. Two major long circumferential branches are the anterior inferior cerebellar artery (AICA) and the superior cerebellar artery. The midbrain receives its arterial supply primarily from the posterior cerebral artery as well as from the basilar artery. The venous drainage of the spinal cord drains directly to the systemic circulation. By contrast, veins draining the cerebral hemispheres and brain stem drain into the dural sinuses. Cerebrospinal fluid also drains into the dural sinuses through unidirectional valves termed arachnoid villi. 

Each node, also called a lymph gland, has both arterial blood supply and venous drainage. Lymphocytes drain out of the arteries into the node interior, usually through a high endothelial venule that facilitates their entry. This venule (small vein) derives its name from the higher-than-usual tightly joined endothelial cells that line it. 

These veins are located between the surface of the liver or spleen and the diaphragm. They are used for collateral circulation. Drainage takes place into the inferior vena cava. 

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