Middle plexus

The BBB is found throughout the brain and spinal cord except for a small number of isolated regions of brain that line the ventricles, the large cavities in the middle of the brain. These circumventricular organs (CVOs) include the choroid plexus (a patch of tissue that lines the floors of the ventricles and manufactures cerebrospinal fluid), the median eminence of the hypothalamus, the subfornical organ at the roof of the third ventricle and the area postrema at the base of the fourth ventricle. 

Blood from the haemorrhoidal venous plexus passes via the azygous superior rectal vein into the inferior mesenteric vein and thereafter into the portal vein. By contrast, the paired middle rectal vein and inferior rectal vein discharge their blood via the iliac vein into the inferior vena cava. In portal hypertension, anorectal varices are found in the region of the rectum, the anal canal and the external anal region. Haemorrhoids are distended and dislocated cavernous bodies in the rectum, which have no connection to the portal venous system. Although haemorrhoids and anorectal varices are two different clinical pictures, it is quite possible for them to occur simultaneously. The frequency of anorectal varices (40-80%) is dependent upon the extent and duration of portal hypertension. The bleeding tendency is low (7-14%). However, there have also been reports of massive haemorrhages. (21,45,55,66,83,105,156) (s. tab. 14.10)... 

Hie solar plexus is at the bottom of the rib cage, just beneath the breast bone. To attack this area, thrust sharply with the second knuckle of the protruding middle finger (fig. 19). This method per- mils sharp penetration and is, therefore, more effective than striking this small target with the fist... 

Fractures of the clavicle result from falls onto the shoulder or lateral compression of the shoulder girdle. There is rarely any associated injury to the subclavian vessels, brachial plexus or pleura, unless the injury is due to a direct blow. Clavicular fractures have been (Allman 1967) classified into three types type 1, middle third type 2 distal to the coracoclavicular ligaments and type 3 medial to the sternocleidomastoid and costoclavicular ligament. 

AVMs may be situated in any region of the brain, lying mostly within the distribution of the middle cerebral arteries and involving the hemispheric convexities in continuity with the adjacent leptomenin-ges however, they can be restricted to the dura or choroid plexus. They vary in size from cryptic lesions, vdiich remain invisible even on angiographic studies and are discovered on anatomic studies of surgically removed hematomas, to giant AVMs, which can involve a whole hemisphere. 

The inferior tympanic branch has certain distinctive features. This artery accompanies the tympanic branch of the 9th cranial nerve in the inferior part of the tympanic cavity, where it usually divides into three branches. The ascending branch anastomoses with the petrosal branch of the middle meningeal artery, accompanying the major deep petrosal nerve. An anterior branch joins the caroticotympanic artery, following the neural anastomosis between the tympanic branch to the ninth cranial nerve and the pericarotid nervous plexus. The posterior branch that courses towards the facial canal, where it anastomoses with the stylomastoid artery. 

The lirst rib is probably the rib most commonly involved in somatic dysfunction of all the ribs. It is affected by trauma, stress, and posture as well as by dysfunction ofthe C7-T1 complex. The patient may report "shoulder" pain, stiff neck, upper back or neck pain, and an inability to turn the head while driving. The first rib can impinge the neurovascular bundle as it passes between it and the clavicle through the costoclavicular space. The anterior and middle scalene muscles, which raise the first rib, may likewise compress the brachial plexus when they are in spasm and result in thoracic outlet syndrome symptoms. The patient s symptoms are then described as pain, numbness, or paresthesias ofthe arm or hand on the involved side. The physician needs to be aware that this may cause confusion should the patient demonstrate a herniated cervical disc on magnetic resonance imaging [MRO. The symptoms may be caused by the rib dysfunction rather than the herniated disc, so evaluation ofthe rib for normal motion and treatment of any dysfunction should be performed in these cases. Osteopathic manipulation may save the patient unnecessary surgery. 

The thoracic outlet region includes the brachial plexus nerves and the subclavian artery and vein. These neurovascular structures traverse restricted spaces in which they can be compressed, the most important of which are the interscalene triangle, the costoclavicular space and the retropectoralis minor space (Fig. 6.16a) (Demondion et al. 2000). Both subclavian artery and brachial plexus nerves pass through the interscalene triangle, a space bordered by the anterior scalene musde anteriorly, the middle scalene muscle posteriorly and the first rib inferiorly. 

The vascular barrier system in the brain consists of the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barriers. There is another barrier, the brain-CSF barrier, between brain tissue and the CSF. The locations of these barriers are demonstrated in Figure i4.i [3]. The blood-brain barrier is the name for the wall of the cerebral microvessels in the brain parenchyma. At the surface of the brain parenchyma, microvessels running in the pia mater are called pial microvessels, which are often used as in vivo models for studying the BBB permeability. Owing to its unique structure that wiUbe discussed in the next section, the BBB maintains very low permeability to water and solutes. In the middle of the brain parenchyma, there are ventricular cavities (ventricles) filled with CSF secreted by the epithelial cells of choroid plexus [4]. The choroid plexus is a highly vascular tissue with leaky, fenestrated capillaries covered with ependymal epithelium, which has relatively tight junctions. The multiceU layer between the blood and the CSF in the choroid plexuses is called the blood-CSF barrier. 

The posterior lateral choroidal artery may arise in the middle or terminal portion of the P-2 segment just before its bifurcation or it may arise from either the inferolateral or superomedial trunk. This occurs at the level of the posterior rim of the peduncle. The vessel continues then to enter the choroid plexus to anastomose with the choroid plexus branch of the... 

---