Circulatory system veins

The adenohypophysis does not have a direct anatomical connection with the hypothalamus therefore, regulation of hormone secretion by way of neuronal signals is not possible. Instead, these two structures are associated by a specialized circulatory system and the secretion of hormones from the adenohypophysis is regulated by hormonal signals from the hypothalamus (see Figure 10.2). Systemic arterial blood is directed first to the hypothalamus. The exchange of materials between the blood and the interstitial fluid of the hypothalamus takes place at the primary capillary plexus. The blood then flows to the adenohypophysis through the hypothalamic-hypophyseal portal veins. Portal veins are blood vessels that connect two capillary beds. The second capillary bed in this system is the secondary capillary plexus located in the adenohypophysis. 

The circulatory system is composed of several anatomically and functionally distinct blood vessels including (1) arteries, (2) arterioles, (3) capillaries, and (4) veins. 

Figure 15.1 The circulatory system. Arteries carry blood away from the heart. The smallest arterial vessels, the arterioles, are composed mainly of smooth muscle and are the major resistance vessels in the circuit. The capillaries are the site of exchange between blood and tissues. Veins carry blood back toward the heart. The small veins are the major compliance vessels in the circuit and, under resting conditions, contain 64% of the blood volume.

The most distensible vessels in the circulatory system are the veins. As with arteries, this feature of the veins also has important physiological implications because it allows them to serve as blood reservoirs. The veins are so distensible that they are capable of holding large volumes of blood at very low pressures. In fact, under resting conditions, 64% of the blood volume is contained within these vessels. 

The circulatory system moves materials (and heat) from one organ to another. It is centred on the heart which pumps blood through arteries to capillaries, where exchange occurs before the blood returns to the heart via the veins (Figure 1.16). During its passage through the tissues, there... 

Amino acids, sugars, and minerals pass through the small intestine into the circulatory system, where they are mixed with blood. The primary reactor organs in processing blood are muscle and the kidneys. The fluid flows in nearly total recycle through arteries and veins, which are basically the pipes in the system, and capillaries, where most of the transfer to and from the reactors and separators occurs. 

Figure 3.2 Schematic of distribution and elimination of pharmaceutical compound on normal administration. Compound is distributed through the (a) lungs, (b) arteries, (c) other tissues (e.g., muscles, subcutenous tissues), (d) veins, and (e) gastrointestinal tract (i.e., oral). Notice the enteroheptic cycle where recirculation occurs between the hver and the GIT with most of the drug being excreted in the bile and is released into the gall bladder, transits into the small intestine, and is absorbed into the circulatory system.

Figure 1.5 The blood vessel and nerve supply in the mammary glands of a cow. Circulatory system (arteries, white veins, stippled) h, heart a, abdominal aorta pa, external pudic artery pv, external pudic vein s, subcutaneous abdominal vein c, carotid artery j, jugular vein. Nerves 1, first lumbar nerve 2, second lumbar nerve 3, external spermatic nerve 4, perineal nerve. A and V show blood sampling points for arteriovenous (AV) difference determinations (Mepham, 1987).

Intravenous delivery is the most direct route into the circulatory system. The entirety of the administered drug reaches the blood because the dose is placed into a vein, and therefore IV routes define 100% bioavailability. Absorption is not an issue. 

The intestine-blood-liver-bile loop constitutes the enterohepatic circulation system (see Figure 6.5). A substance absorbed through the intestines goes either directly to the lymphatic system or to the portal circulatory system. The latter carries blood to the portal vein that goes directly... 

Figure 8-14. Circulatory system for the ear of a rabbit. The area of the vein to be longitudinally cut is denoted by a dashed line.

FIGURE 6.8 Packaging of fatty acids by the liver. (1) The radioactive fatty acid is injected into a vein and enters the cells of the liver. Most of the cells of the liver manufacture lipoproteins (circles). (2) Fatty acids in the Uver, including the injected radioactive fatty acid, are converted to triglycerides and packaged into the lipoproteins. (3) Lipoproteins are secreted continuously by the liver into the bloodstream. Most of the lipoproteins in the blood have been in the circulatory system for several hours. Blood sample removal after various time periods following injection of the radioactive tracer facilitates generating a minute-by-minute picture of the secretory processes, both in normal animals and in those that are choline deficient. 

The intravenous (IV) parenteral route directly injects medication into the circulatory system, providing rapid onset. The IV should be inserted in the dorsal vein but can also be inserted into the ... 

Standardized mortality ratio (SMR) in the subgroup was 328 (5 observed/1.52 expected deaths, 95% confidence interval [Cl] 33-61, p value not reported). Kimbrough et al. (1999a) found no significant increases in mortality related to ischemic heart disease, hypertension with heart disease, other diseases of the heart, cerebrovascular disease, or circulatory system (arteries, veins, pulmonary circulation) in a study of 7,075 male and female capacitor workers. One of the subgroups (male salaried workers) in this study had a significantly decreased risk of mortality from ischemic heart as indicated by an SMR lower than 100 (44 observed/97.5 expected deaths, SMR=45, 95% Cl 107-766, p<0.01). Neither of these studies reported adequate quantitative exposure data. The inconsistent results of these studies could be due to differences in exposure levels, durations, and latencies, as well as types of Aroclors and cohort sizes. Additional information on these studies is provided in Section 3.2.8.2.I. 

The properties of water are different from those of sodium chloride and carbon dioxide. Water is the only one of the three compounds that occurs in Earth s environment in aU three states of matter, as shown in Figure 4.7. At sea level, liquid water boils into gaseous water (steam) at 100°C and freezes to solid water (ice) at 0°C. Pure water does not conduct electricity in any of its states. Water is also excellent at dissolving other substances. It is often called the universal solvent in recognition of this valuable property. Water plays a vital role in the transport of dissolved materials, whether the aqueous solution is flowing down a river up the xylem in a tree or through the veins, capillaries, and arteries of your circulatory system. 

The animals used in these studies were conditioned male dogs of mixed breed. Access to the animals circulatory systems was accomplished via an acute shunt surgically implanted in the neck of the dog. The shunt was constructed of Vie in. Silastic tubing anastomosed to the carotid artery and jugular vein. Blood flow through the shunt was on the order of 1 L/min. 

Serving the GI tract is an important blood circulatory system, and a main feature is the flow from veins (serving the regions from the esophagus to near the end of the rectum) into the portal vein, which delivers blood to the hepatic sinusoids before blood flows into the general circulation. This is portal venous blood flow and is... 

In addition, dmg abusers rarely use aseptic techniques for administering drags intravenously which can lead to localized and systemic infections such as endocarditis (infection of the lining of the heart), HIV, and sepsis (infection of the entire circulatory system). Drag abusers also incur cellulitis (infection in the tissues), sclerosis (scaring of the veins), phlebitis (irritation of veins), and skin abscesses. 

First of all, this secretin originates in the intestine. K the duodenum-jejunal mucous membrane is macerated in dilute HCl, iV/io for example, and after neutralization tire solution so obtained is injected into the veins, a large pancreatic secretion results. This setting free of secretin also takes place in vitro. By injecting dilute hydrochloric acid or a solution of soap into the duodenum of an animal, it is found that its intestinal content, collected after a certain time and injected into another animal, causes pancreatic secretion. It is not even necessary to previously inject HCl or a solution of sodium oleate. The ample duodenum-jejimal content of an animal in the course of digestion, after filtration and elimination of the albumoses and the peptones, can, if it is introduced into the circulatory system of an animal, cause a pancreatic secretion to take place. 

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