- Key People:
- Carl F.W. Ludwig
- William Prout
renal system
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What is the renal system?
The renal system, also known as the urinary system, is an organ system that produces, stores, and eliminates urine. In humans, it consists of the kidneys, ureters, bladder, and urethra.
Each kidney contains approximately 1,000,000 nephrons, the structural units that produce urine. Urine passes from the kidneys through the ureters to the bladder, where it is stored until it is eliminated through the urethra. The urethra has anatomical links to reproductive structures, so its characteristics differ between males and females.
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What are the main organs of the renal system?
The renal system, crucial for maintaining the body's internal environment, includes the kidneys, ureters, urinary bladder, and urethra.
The kidneys, the primary organs, regulate blood composition by eliminating waste and excess substances in urine. Urine passes from the kidneys through the ureters, narrow tubes, into the bladder. The bladder stores urine until it is voided through the urethra.
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Where are the kidneys located in the body?
The kidneys are bean-shaped, reddish-brown organs located high in the abdominal cavity against its back wall. They sit on either side of the vertebral column between the levels of the 12th thoracic and third lumbar vertebrae, outside the peritoneum. The upper end of each kidney is tilted slightly inward toward the backbone. The hilus, a deep vertical cleft on the medial concave border, is the entry and exit point for renal arteries and veins, lymphatic vessels, nerves, and the upper extension of the ureters.
The renal arteries originate from the abdominal aorta, near the second lumbar vertebra. The renal veins, which carry blood from the kidneys, connect to the inferior vena cava; the left vein is longer than the right because of the inferior vena cava's proximity to the right kidney. The kidneys are connected to the autonomic nervous system through sympathetic and parasympathetic nerves, containing both afferent and efferent fibers.
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What is the main function of the kidneys?
The primary function of the kidneys is to regulate the volume, chemical composition, and osmotic pressure of blood and tissue fluids. They achieve this by filtering water and salts from the blood, reabsorbing essential substances, and excreting the remaining filtrate as urine. The kidneys maintain a stable internal environment despite external changes.
Additionally, the kidneys secrete renin (for electrolyte balance and blood pressure control), erythropoietin (for red blood cell formation), and 1,25-dihydroxycholecalciferol (the active form of vitamin D). They also regulate their internal circulation to ensure consistent monitoring of blood composition.
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What are nephrons and why are they important in the kidneys?
Nephrons are the functional units of the kidney, responsible for removing waste and excess substances from the blood to produce urine. Each human kidney contains about 1,000,000 nephrons.
As blood flows through the glomerulus, fluid filters into the nephron tubule. As this filtrate passes through the tubule, its composition changes due to secretion and selective reabsorption. The final product, urine, is then conveyed through collecting tubules. Nephrons are critical for maintaining fluid, electrolyte, and acid-base balance.
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How do the ureters and bladder help the body remove waste?
The ureters and bladder are essential for waste removal. The ureters, narrow tubes roughly 12 inches long, transport urine from the kidneys to the bladder via peristaltic contractions occurring every 10β15 seconds.
The bladder is a hollow, muscular organ with variable capacity that stores urine until elimination. Its mucous membrane lining is distensible, and its muscle coat contracts to empty the organ, while two muscular sphincters keep the exit closed. The renal system eliminates waste and excess substances from the blood through urine, maintaining the body's electrolyte balance.
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renal system, in humans, organ system that includes the kidneys, where urine is produced, and the ureters, bladder, and urethra for the passage, storage, and voiding of urine.
In many respects the human excretory, or urinary, system resembles those of other mammalian species, but it has its own unique structural and functional characteristics. The terms excretory and urinary emphasize the elimination function of the system. The kidneys, however, both secrete and actively retain within the body certain substances that are as critical to survival as those that are eliminated.
The system contains two kidneys, which control the electrolyte composition of the blood and eliminate dissolved waste products and excess amounts of other substances from the blood; the latter substances are excreted in the urine, which passes from the kidneys to the bladder by way of two thin muscular tubes called the ureters. The bladder is a sac that holds the urine until it is eliminated through the urethra.
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Human excretory organs
The kidneys
General description and location
The kidneys are bean-shaped, reddish brown paired organs, concave on one long side and convex on the opposite. They are normally located high in the abdominal cavity and against its back wall, lying on either side of the vertebral column between the levels of the 12th thoracic and third lumbar vertebrae, and outside the peritoneum, the membrane that lines the abdomen.
The long axes of the kidneys are aligned with that of the body, but the upper end of each kidney (pole) is tilted slightly inward toward the backbone (vertebral column). Situated in the middle of the medial concave border is a deep vertical cleft, the hilus, which leads to a cavity within the kidney known as the renal (kidney) sinus. The hilus is the point of entry and exit of the renal arteries and veins, lymphatic vessels, nerves, and the enlarged upper extension of the ureters.