Human excretory organs
Lymphatic vessels human kidney In renal system: These nodes swell in response to infection, due to a build-up of lymph fluid, bacteria, or other organisms and immune system cells. Let's be the change and make the world a better place! The tubule descends into a renal pyramid , makes a U-shaped turn, and returns to the cortex at a point near its point of entry into the medulla. Healthcare , Recent Articles. The skin over the nodes may be red or streaky. Malignant neoplasms, other cutaneous neoplasms with significant vascular component, and disorders erroneously considered as vascular neoplasms".
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This page tells you about the lymphatic system and how cancer may affect it. There is information about. These tubes are called lymph vessels or lymphatic vessels. The lymph system is an important part of our immune system.
It plays a role in:. You can read detailed information about the immune system and cancer. The lymphatic system is similar to the blood circulation. The lymph vessels branch through all parts of the body like the arteries and veins that carry blood. But the lymphatic system tubes are much finer and carry a colourless liquid called lymph.
The lymph contains a high number of a type of white blood cells called lymphocytes. As the blood circulates around the body, fluid leaks out from the blood vessels into the body tissues. Although all nephrons in the kidney have the same general disposition , there are regional differences, particularly in the length of the loops of Henle.
Glomeruli that lie deep in the renal cortex near the medulla juxtamedullary glomeruli possess long loops of Henle that pass deeply into the medulla, whereas more superficial cortical glomeruli have much shorter loops.
Among different animal species the length of the loops varies considerably and affects the ability of the species to concentrate urine above the osmotic concentration of plasma. The successive sections of the nephron tubule vary in shape and calibre , and these differences, together with differences in the cells that line the sections, are associated with specific functions in the production of urine.
The intrarenal network of blood vessels forms part of the blood-processing apparatus of the kidneys. The anterior and posterior divisions of each renal artery , mentioned earlier, divide into lobar arteries, each of which enters the kidney substance through or near a renal papilla. Each lobar artery gives off two or three branches, called interlobar arteries, which run outward between adjacent renal pyramids. When these reach the boundary between the cortex and the medulla they split almost at right angles into branches called arcuate arteries that curve along between the cortex and the medulla parallel to the surface of the kidney.
Many arteries, called interlobular arteries , branch off from the arcuate arteries and radiate out through the cortex to end in networks of capillaries in the region just inside the capsule.
En route they give off short branches called the afferent arterioles , which carry blood to the glomeruli where they divide into four to eight loops of capillaries in each glomerulus. Near and before the point where the afferent arteriole enters the glomerulus, its lining layer becomes enlarged and contains secretory granules. This composite structure is called the juxtaglomerular apparatus JGA and is believed to be involved in the secretion of renin see below The role of hormones in renal function.
They are then reconstituted near the point of entry of the afferent arteriole to become the efferent arterioles carrying blood away from the glomeruli.
The afferent arterioles are almost twice as thick as the efferent arterioles because they have thicker muscular coats, but the sizes of their channels are almost the same.
Throughout most of the cortex the efferent arterioles redivide into a second set of capillaries, which supply blood to the proximal and distal renal tubules.
The efferent glomerular arterioles of juxtaglomerular glomeruli divide into vessels that supply the contiguous tubules and vessels that enter the bases of the renal pyramids. Known as vasa recta, these vessels run toward the apexes of the pyramids in close contact with the loops of Henle. Like the tubules they make hairpin bends, retrace their path, and empty into arcuate veins that parallel the arcuate arteries.
Normally the blood circulating in the cortex is more abundant than that in the medulla amounting to over 90 percent of the total , but in certain conditions, such as those associated with severe trauma or blood loss, cortical vessels may become constricted while the juxtamedullary circulation is preserved. Because the cortical glomeruli and tubules are deprived of blood, the flow of urine is diminished, and in extreme cases may cease. The renal venules small veins and veins accompany the arterioles and arteries and are referred to by similar names.
The venules that lie just beneath the renal capsule , called stellate venules because of their radial arrangement, drain into interlobular venules. In turn these combine to form the tributaries of the arcuate, interlobar, and lobar veins. Blood from the renal pyramids passes into vessels, called venae rectae, which join the arcuate veins.
In the renal sinus the lobar veins unite to form veins corresponding to the main divisions of the renal arteries, and they normally fuse to constitute a single renal vein in or near the renal hilus. Lymphatic capillaries form a network just inside the renal capsule and another, deeper network between and around the renal blood vessels. Few lymphatic capillaries appear in the actual renal substance, and those present are evidently associated with the connective tissue framework, while the glomeruli contain no lymphatics.
The lymphatic networks inside the capsule and around the renal blood vessels drain into lymphatic channels accompanying the interlobular and arcuate blood vessels. The main lymph channels run alongside the main renal arteries and veins to end in lymph nodes beside the aorta and near the sites of origin of the renal arteries. The ureters are narrow, thick-walled ducts, about 25—30 centimetres 9.
Throughout their course they lie behind the peritoneum, the lining of the abdomen and pelvis, and are attached to it by connective tissue. In both sexes the ureters enter the bladder wall about five centimetres apart, although this distance is increased when the bladder is distended with urine.
The ureters run obliquely through the muscular wall of the bladder for nearly two centimetres before opening into the bladder cavity through narrow apertures. This oblique course provides a kind of valvular mechanism; when the bladder becomes distended it presses against the part of each ureter that is in the muscular wall of the bladder, and this helps to prevent the flow of urine back into the ureters from the bladder.
The wall of the ureter has three layers, the adventitia, or outer layer; the intermediate, muscular layer; and the lining, made up of mucous membrane.
The adventitia consists of fibroelastic connective tissue that merges with the connective tissue behind the peritoneum. The muscular coat is composed of smooth involuntary muscle fibres and, in the upper two-thirds of the ureter, has two layers—an inner layer of fibres arranged longitudinally and an outer layer disposed circularly.
In the lower third of the ureter an additional longitudinal layer appears on the outside of the vessel. As each ureter extends into the bladder wall its circular fibres disappear, but its longitudinal fibres extend almost as far as the mucous membrane lining the bladder.
The mucous membrane lining increases in thickness from the renal pelvis downward. Thus, in the pelvis and the calyxes of the kidney the lining is two to three cells deep; in the ureter, four to five cells thick; and in the bladder, six to eight cells. The mucous membrane of the ureters is arranged in longitudinal folds, permitting considerable dilation of the channel. There are no true glands in the mucous membrane of the ureter or of the renal pelvis.
The chief propelling force for the passage of urine from the kidney to the bladder is produced by peristaltic wavelike movements in the ureter muscles. The urinary bladder is a hollow muscular organ forming the main urinary reservoir. It rests on the anterior part of the pelvic floor see below , behind the symphysis pubis and below the peritoneum. The symphysis pubis is the joint in the hip bones in the front midline of the body.
The shape and size of the bladder vary according to the amount of urine that the organ contains. When empty it is tetrahedral and lies within the pelvis; when distended it becomes ovoid and expands into the lower abdomen. It has a body, with a fundus, or base; a neck; an apex; and a superior upper and two inferolateral below and to the side surfaces, although these features are not clearly evident except when the bladder is empty or only slightly distended.
The neck of the bladder is the area immediately surrounding the urethral opening; it is the lowest and most fixed part of the organ. In the male it is firmly attached to the base of the prostate, a gland that encircles the urethra. The superior surface of the bladder is triangular and is covered with peritoneum. The bladder is supported on the levator ani muscles, which constitute the major part of the floor of the pelvic cavity. The bladder is covered, and to a certain extent supported, by the visceral layer of the pelvic fascia.
This fascial layer is a sheet of connective tissue that sheaths the organs, blood vessels, and nerves of the pelvic cavity. The fascia forms, in front and to the side, ligaments, called pubovesical ligaments, that act as a kind of hammock under the inferolateral surfaces and neck of the bladder.
The blood supply of the bladder is derived from the superior, middle, and inferior vesical bladder arteries. The superior vesical artery supplies the dome of the bladder, and one of its branches in males gives off the artery to the ductus deferens , a part of the passageway for sperm. The middle vesical artery supplies the base of the bladder. The inferior vesical artery supplies the inferolateral surfaces of the bladder and assists in supplying the base of the bladder, the lower end of the ureter, and other adjacent structures.
The nerves to the urinary bladder belong to the sympathetic and the parasympathetic divisions of the autonomic nervous system. The sympathetic nerve fibres come from the hypogastric plexus of nerves that lie in front of the fifth lumbar vertebra. Sympathetic nerves carry to the central nervous system the sensations associated with distention of the bladder and are believed to be involved in relaxation of the muscular layer of the vesical wall and with contraction of sphincter mechanism that closes the opening into the urethra.
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