How do fluids get from the stomach to kidNEY?

The movement of fluids from the stomach to the kidneys involves several physiological processes and structures:

1. Digestion in the Stomach: After we consume liquids and food, they enter the stomach, which is a muscular organ that begins the process of digestion. The stomach secretes gastric juices, including hydrochloric acid and digestive enzymes, to break down food particles.

2. Absorption in the Small Intestine: Once partially digested, the chyme (food and fluid mixture) leaves the stomach and enters the small intestine. Here, nutrients, water, and electrolytes are absorbed through the intestinal walls into the bloodstream.

3. Portal Circulation: The small intestine has a rich network of blood vessels called mesenteric vessels. After absorption, the nutrients, along with fluids, are transported through these mesenteric veins to the liver. The liver processes and filters these nutrients and fluids before sending them to the rest of the body.

4. Renal Blood Supply: The liver sends the blood, containing the absorbed nutrients and fluids, to the heart through the hepatic veins. From the heart, the blood is pumped to the kidneys through the renal arteries.

5. Glomerular Filtration: In the kidneys, the renal arteries branch into tiny filtering units called nephrons. Each nephron consists of a filtering structure called the glomerulus, surrounded by a cup-shaped structure called Bowman's capsule. Fluid, along with waste products, salts, and small molecules, is forced out of the glomerulus into Bowman's capsule. This initial step of filtration is known as glomerular filtration.

6. Tubular Reabsorption: As the filtered fluid moves along the nephron tubules, essential substances, such as water, glucose, amino acids, and sodium, are reabsorbed back into the bloodstream through passive and active transport mechanisms. This reabsorption process ensures that the body retains what it needs.

7. Tubular Secretion: Additionally, the renal tubules also secrete certain substances, like drugs, toxins, and excess ions, from the bloodstream into the tubules. This secretion further contributes to the composition of the final urine.

8. Urine Formation and Excretion: The remaining fluid after filtration, reabsorption, and secretion is considered urine. It travels through the collecting tubules and ureters to the bladder. The bladder stores urine until it reaches a certain volume, triggering the urge to urinate. When we urinate, the urine is expelled from the body through the urethra.

In summary, fluids from the stomach pass through the digestive system and are absorbed into the bloodstream. The liver processes and sends these fluids, along with nutrients, to the kidneys. The kidneys filter the blood and reabsorb essential substances while eliminating waste products and excess fluids as urine. This complex process ensures proper fluid balance and the removal of waste from the body.