Research Area

Excretory System Development

Excretory system development overview

Excretory System Development

The excretory system refers to the continuous production of wastes that cannot be reused or even toxic in the metabolic process of animals. At the same time, excessive intake of water, salt and some toxic substances are taken into the body when the animals ingest food, and these substances must be continuously excreted. The endogenous substances, excess substances and substances not required by the body are transported to the excretory organs through the blood circulation and are excreted from the physiological process in vitro, which is called excretion. This process is mainly done by the way the kidneys form urine. The excretory system also has a relatively stable function of regulating water, salt metabolism, acid-base balance, and maintaining the body environment while discharging urine. Therefore, the development of the excretory system is very important for the body's steady state. If the excretory system is not developed properly, it will cause some serious diseases.

Excretory system development research status

The amniotic animal kidneys occur continuously through the two stages of the anterior kidney (embryo stage) and the dorsal kidney (adult); while the amniotic animal undergoes three stages, namely the anterior kidney, the middle kidney (embryo stage) and the posterior kidney (adult). Anterior kidney: The anterior kidney is located on both sides of the dorsal midline of the end of the body cavity and is arranged in small tubular segments. These small tubes are called anterior renal tubules. One end of each anterior renal tubule is open to the body cavity, and the opening is funnel-shaped, with cilia on it, called the kidney mouth, and the other end of the small tube is connected to a total catheter, called the anterior kidney tube, and the end is inserted into the cloaca or the sinus. Near the renal ostium, there are vascular globules formed by vascular plexus. They discharge the metabolic waste contained in the blood into the body cavity by filtration and collect the waste in the body cavity into the renal tubule by means of the swing of the cilia at the renal mouth. The anterior renal tube is excreted from the cloaca (reflecting the original nephron structure), and this connection between the glomerulus and the renal tubule is called the body cavity connection. This type of kidney is a stage that vertebrates experience during the embryonic period, and only certain round mouths and a few hard bone fish remain in adulthood. Middle or posterior kidney: The middle kidney refers to the kidney that appears in the amniotic embryo stage after the anterior kidney. It is in the middle of the body cavity. The posterior kidney refers to the kidney without the amniotic membrane. It is in the middle and back of the body cavity. When the anterior kidney degenerates, a series of new renal tubules form a new renal tubule, i.e., a middle renal tubule. The middle renal tubule extends to the side and communicates with the longitudinal anterior renal tube. At this time, the anterior renal tube is called the middle kidney tube. One end of the middle renal tubule is open in the middle kidney tube, and the other end is inflated into a double-layered cup-shaped capsule, that is, a renal balloon, in which a vascular balloon is wrapped to form a renal corpuscle, and the nephron structure tends to be perfect. The vascular spheroid in the sac is called the inner vascular spheroid to distinguish it from the outer vascular globule in which the anterior kidney is suspended in the body cavity. The waste from the blood vessels of the inner vascular bulb directly enters the renal balloon and then passes through the renal tubule to the middle kidney tube. This connection is called vascular communication and in comparison, with the body cavity connection of the anterior kidney, undoubtedly has a more efficient excretory function. The connection of the lumen to the vascular connection is a major advancement in animal excretion. The posterior kidney is the kidney of the amniotic animal. The stage of its occurrence and the site of its growth are all behind the kidney. The posterior kidney has a dual source of occurrence: one part is derived from the posterior kidney bud; the other part is derived from the posterior renal tube bud. The posterior renal bud base is connected to the posterior part of the middle renal tubule. It is also composed of renal tubules. The number of posterior renal tubules is larger than that of the small renal tubules. One end is a renal corpuscle, and there is no renal mouth at all. The other end is connected to the collecting duct. The posterior renal tube bud is a pair of protrusions protruding from the base of the middle kidney tube near the cloaca. The distal end of the kidney tube is extended to connect the posterior renal bud base, and branches at the end of the kidney to form many collecting tubes. It can be said that the kidney structure has a richer kidney unit and the function is more perfect than that of the middle kidney or the posterior kidney. In summary, vertebrate kidneys have the following evolutionary trends: The number of nephrons is from small to large, the body cavity is connected to the vascular connection, and the site occurs from the front of the body cavity to the middle and back of the body cavity. The ureter and bladder excretory system include the ureter, bladder, and urethra in addition to the kidney. Urine is formed in the kidney, enters the cloaca or bladder through the ureter, and when it is stored in a certain amount, it is excreted through the urethra. Ureter: The middle kidney tube of the sputum is the ureter, which has only urinary function and has nothing to do with reproduction. The cartilage fish additionally forms a plurality of collaterals for urethral resection, and the middle kidney tube acts as a vas deferens. The middle kidney tube of the bony fish is only used for urinary purposes. The amphibious middle kidney tube is the ureter, which is used for male insemination. The ureter of the amniotic animal is the posterior renal tube. Bladder: round mouth, cartilage fish, some reptiles (such as snakes, some lizards, and crocodiles) and birds (except ostriches) have no bladder. Other animals' bladders can be divided into 3 types: ureteral bladder from the middle kidney tube inflated, found in hard-scale fish, hard-bone fish. The cloaca bladder is protruded from the abdominal wall of the cloaca, and the middle kidney tube is not directly related to the bladder. The cloaca hole is normally closed due to the contraction of the sphincter, and the urine is stored in the bladder from the cloaca and is found in the single-hole type of lungfish, amphibians, and mammals.

Excretory system development clinical research

Nephrotic syndrome is characterized by a large amount of protein, edema and hyperlipidemia. In patients with nephrotic syndrome, many protein leaks from the glomerular basement membrane due to various reasons. The consequence is that the renal tubules absorb a large amount of protein, leading to information disorder in the tubular cells, releasing vasoactive substances and inflammatory mediators to the interstitial. The inflammatory response eventually develops into chronic renal insufficiency. In recent years, some new therapeutic drugs and methods have been applied clinically to reduce protein through the glomerular basement membrane. The earliest immunosuppressive agent for the treatment of adult glomerulonephritis and the nephrotic syndrome is prednisone. Clinical practice has shown that some types of nephrotic syndrome can reduce urinary protein and protect kidney function. Subsequently, other immunosuppressive agents such as sulfur anthraquinone, cyclophosphamide, phenylbutazone, etc. are also used to treat nephrotic syndrome, especially in patients with poor prednisone effects, such as focal stage glomerulosclerosis, membranous glomerulonephritis get better results. Non-specific treatment angiotensin, the most important vasoactive peptide in the angiotensin system, plays a key role in renal interstitial fibrosis through receptors. In the 1980s, Borrtenr first pointed out that glomerular capillary transmembrane pressure increased, not only the hemodynamic basis of many chronic primaries or secondary kidney diseases, but also the key to delaying the continuous progression of kidney disease. Many experiments after the 1980s found that the RAS system plays a particularly important role in the above pathology. The RAS system is excited to raise blood pressure and increase the transmembrane pressure of capillaries in the glomerulus. ACIE preparations not only lower blood pressure but also reduce urinary protein by blocking RAS, especially in patients with nephrotic syndrome. ACIE and ARB can prevent renal fibrosis by blocking the RAS system, and ARB has the same effect and efficacy on urine protein. Hyperlipidemia can lead to kidney tissue damage or increased kidney tissue damage and has been demonstrated in various animal models. Lowering blood lipids can improve kidney damage. Hyperlipidemia can damage glomerular innate cells including endothelial cells, glomerular epithelial cells, mesangial cells, which in turn leads to glomerular sclerosis. Low-density lipoprotein can also induce an increase in apoptosis of mesangial cells, which plays a role in glomerular sclerosis. In addition to lowering blood lipids, statins can also improve endothelial cell function, alter the local fiber balance of the vessel wall, and increase fibrinolytic activity. Non-steroidal anti-inflammatory drugs can reduce urinary protein by reducing the glomerular filtration rate. Treatment of chronic renal failure should include specific treatment of primary disease, evaluation, and improvement of comorbidities. In preparation, dialysis or transplantation should be initiated if the uremia phase has been reached. Measures to delay renal failure: Eliminate CRF deterioration risk factors such as: infection, sepsis, major bleeding or hypovolemia, hypokalemia, hypercalcemia, stones, urinary tract obstruction, nephrotoxic drugs; diet therapy: low-protein and low-phosphorus diet. Studies have found that patients with chronic renal failure, like normal people, limit protein intake can activate the body's moderate response, that is, the degree of protein degradation after the meal is inhibited, and the oxidative decomposition of amino acids is also significantly reduced. Controlling systemic and glomerular hypertension in a timely and proactive manner to control hypertension is an important factor in delaying the progression of CRF. For hyperlipidemia, we must first limit the intake of fat, especially unsaturated fatty acids. In recent years, studies have shown that in addition to lipid-lowering, it also has a non-dependent lipid-lowering kidney protection, which can slow glomerular sclerosis. Antiplatelet aggregation drugs have a role in reducing renal circulation thrombosis, and its slowing of glomerular sclerosis needs further study. Other vasoactive drugs, such as astragalus injection, have been confirmed in previous studies, and the traditional Chinese medicine Huangmao has reduced urine protein. As a vasodilator, prostaglandin has a certain protective effect on the kidney. Recently, foreign scholars have found that prostaglandin lE, the mechanism of renal protection is not limited to improving renal vascular flow, inhibiting platelet aggregation, etc., importantly, it can inhibit glomerular intrinsic cell proliferation and accumulation of extracellular matrix. Early treatment of chronic renal failure plays an important role in delaying the development of the disease and improving the prognosis of patients. In short, strengthening comprehensive treatment to alleviate CRF symptoms in all aspects can delay its development.


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