Medulla/medullary

Fig. 2. Schematic representation of relevant electrolyte transport through the renal tubule, depicting the osmolar gradient ia medullary iaterstitial fluid ia ywOj yW where represents active transport, —passive transport, hoth active and passive transport, and passive transport of H2O ia the presence of ADH, ia A, the cortex, and B, the medulla. An osmole equals a mole of solute divided by the number of ions formed per molecule of the solute. Thus one mole of sodium chloride is equivalent to two osmoles, ie, lAfNaCl = 2 Osm NaCl. ADH = antidiuretic hormone.

Figure 9.1 The distribution of 5-HT neurons in the brain. The cell bodies are clustered in nuclei (B1-B7) in the pons/upper medullary regions of the brainstem. The rostral cluster ( superior group ) project mainly to forebrain areas while the caudal ( inferior ) group projects mainly to the medulla and spinal cord. Collectively, these neurons innervate most regions of the central nervous system...

Medullary cystic disease A hereditary kidney disorder characterized by gradual and progressive loss of kidney function because of cysts in the kidney medulla. 

Aggregates of cell bodies within the medulla of the brainstem form the medullary respiratory center, which has two distinct functional areas ... 

Proprioceptors originating in muscles and joints of the exercising limbs provide substantial input to the medullary respiratory center. In fact, even passive movement of the limbs causes an increase in ventilation. Therefore, the mechanical aspects of exercise also contribute to the ventilatory response. The increased metabolism associated with exercise increases body temperature, which further contributes to the increase in ventilation during exercise. (Not surprisingly, ventilation is also enhanced in response to a fever.) Exercise is associated with a mass sympathetic discharge. As a result, epinephrine release from the adrenal medulla is markedly increased. Epinephrine is believed to stimulate ventilation. 

The vasa recta are modified peritubular capillaries. As with the peritubular capillaries, the vasa recta arise from efferent arterioles. However, these vessels are associated only with the juxtamedullary nephrons and are found only in the medullary region of the kidney. The vasa recta pass straight through to the inner region of the medulla, form a hairpin loop, and return straight toward the cortex. This structure allows these vessels to lie parallel to the Loop of Henle and collecting ducts. 

The abdominal vagus and sympathetic nerves are the most important afferent inputs involved in vomiting induced by chemotherapy and radiation [31]. The input from vestibular nerves and the cerebellum plays an important role in the motion disease [52]. The afferent inputs from vagal, trigeminal and glossopharyngeal nerves terminate eventually in the nucleus solitarius tract located in the medulla oblongata which has neuronal connections with other medullary areas involved in emesis, for example, area postrema [53]. 

A lymph node consists of a cortex and an inner medulla. The cortex is composed of an outer cortex, which contains B-lymphocytes, within lymphoid follicles, and paracortical areas, which contain mainly T-lymphocytes and dendritic cells. The proliferation of B-cells occurs in central areas, called germinal centres. The medulla consists of strings of macrophages and the B-cells that secrete the antibodies (i.e. the effector cells) these are the medullary cords (Figure 17.42). Lymph carries immune cells (e.g. lymphocytes, antigen-presenting cells) and pathogens from the tissues to the lymph nodes, via the afferent lymphatics. 

A single artery enters the lymph node at the hilum. After branching, the vessels pass through the medulla within the medullary cords and into the inner and outer cortex. The vessels branch into capillaries around the follicles which provide oxygen, fuels and precursor molecules for the proliferating cells. 

The cells of the adrenal medulla, called chromaffin cells, are homologous with sympathetic postganglionic neurons. The adrenal medulla may in fact be considered a modified sympathetic ganglion. The adrenal medulla secretes two hormones. One is norepinephrine, which is also the primary neurotransmitter of sympathetic postganglionic neurons. The other medullary hormone is epinephrine. 

General activation of the sympathetic system during stress, fear, or anxiety is accompanied by increased secretion of adrenal medullary hormones, which consist primarily of epinephrine in the human. The secretory activity of the adrenal medulla is regulated by the CNS. 

Action on respiration Morphine depresses the medullary respiratory centre in medulla oblongata and by reducing the sensitivity of the medullary respiratory centre to increased plasma CO. The rise in arterial... 

At the boundary between the inner and outer stripes of the outer medulla, the proximal tubule empties into the thin descending limb of Henle s loop. Water is extracted from the descending limb of this loop by osmotic forces found in the hypertonic medullary interstitium. As in the proximal tubule, impermeant luminal solutes such as mannitol oppose this water extraction. The thin ascending limb is relatively water-impermeable. 

Both the medulla and the cortex of the kidney synthesize prostaglandins, the medulla substantially more than the cortex. COX-1 is expressed mainly in cortical and medullary collecting ducts and mesangial cells, arteriolar endothelium, and epithelial cells of Bowman s capsule. COX-2 is restricted to the renal medullary interstitial cells, the macula densa, and the cortical thick ascending limb. 

IV. Stage of medullary depression This deep stage of anesthesia includes severe depression of the CNS, including the vasomotor center in the medulla, as well as the respiratory center in the brain stem. Without circulatory and respiratory support, death rapidly ensues. 

Stage IV. Medullary Paralysis. This stage is marked by the cessation of spontaneous respiration because respiratory control centers located in the medulla oblongata are inhibited by excessive anesthesia. The ability of the medullary vasomotor center to regulate blood pressure is also affected, and cardiovascular collapse ensues. If this stage is inadvertently reached during anesthesia, respiratory and circulatory support must be provided or the patient will die.39... 

We now turn to an anatomical description of lymph nodes. The lymph node is surrounded by a thick, fibrous capsule and is subdivided into compartments by trabeculae. Inside the capsule is the subcapsular or marginal sinus, which forms the entry point of lymphatic fluid into the node, via the afferent vessel. The lymph node cortex, which lies beneath the subcapsular sinus, is the location of the primary and secondary lymphoid follicles. The primary follicles are comprised of B-lymphocytes. An immune response stimulates B-cells to replicate and differentiate, converting the primary follicle into a secondary follicle or germinal center, surrounded by a zone of small lymphocytes. The paracortex surrounds the germinal centers and primary follicles and contains mostly T-lymphocytes. The medulla is composed of medullary cords, consisting of macrophages and plasma cells, and medullary sinuses. The medullary vessels include the arteries and veins, and the afferent and efferent lymphatic vessels, respectively, deliver the lymphatic fluid into and out of the lymph node. 

The anatomy of the tuber is shown diagrammatically in Figure 11.2. Parts that can be distinguished are the skin (periderm) with the lenticels, the eyes, the bud and stem ends, the cortex, the ring of vascular bundles, the perimedullary zone, and the pith with medullary rays which are homologous with the medulla of the stolon.7... 

Those spinal radicular arteries that are radiculo-medullary arteries, supplying nerve root, pial plexus and medulla, branch in a very typical way to form the anterior spinal artery. The ascending branch continues the direction of the radicular artery in the midline of the anterior surface. The descending branch, being the larger one at thoracolumbar levels, forms a hairpin curve as soon as it reaches the midline at the entrance of the anterior fissure (Fig. 17.3). The artery runs above the vein. The maximum diameter of a spinal radiculomedullary artery or the anterior... 

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