Anatomy and Physiology of Urinary System

Anatomy and Physiology of Urinary System

Welcome back to Educator.com! In this lesson, we will be discussing the urinary system. The functions of the urinary system go beyond simply producing and eliminating urine. While that is its primary function, it also plays a crucial role in removing metabolic wastes from your bodily fluids. Solid waste, on the other hand, is part of the digestive system and is eliminated through fecal matter. The urinary system primarily focuses on filtering blood and eliminating metabolic wastes.

Additionally, the urinary system is responsible for regulating blood volume and blood pressure. Your kidneys secrete hormones in response to the amount of blood flowing through them, which can affect your blood pressure and blood volume. Furthermore, the urinary system helps maintain the proper concentrations of electrolytes, such as sodium, potassium, and chloride, in your plasma. Depending on the levels of these electrolytes, the urinary system will excrete more or less of them through urine. Lastly, it also aids in stabilizing blood pH by either retaining or eliminating substances like sodium and H+ ions.

These hydrogen ions have an impact on pH, while bicarbonate ions affect alkaline levels. Understanding pH allows us to recognize that retaining hydrogen ions would slightly increase blood acidity, while eliminating them would slightly increase blood alkalinity. The normal pH for blood in the human body is 7.4, which is slightly basic. This is important for preserving valuable nutrients in the bloodstream. Kidney function plays a crucial role in this process. When examining the urinary system, there are four main components. The kidneys, resembling kidney beans, are located on either side of the spine between the thoracic vertebrae, specifically from the bottom of the thoracic curvature (number 12) to the third lumbar vertebra. They are partially covered by the ribcage, with the top portion having some ribs behind it. The ureters are tubes that transport recently produced urine from the kidneys to the urinary bladder, which serves as a temporary storage spot. It is important to specify "urinary bladder" to differentiate it from the gall bladder. Finally, the urethra is the tube responsible for eliminating urine from the body. It is longer in males and shorter in females.

All of these arteries are interloper arteries that branch off of the little segmental arteries. The arcuate arteries finally take blood branching off of the interloper mobile arteries all the way up to the more superficial cortex regions. In these regions, you will see the arcuate arteries and then finally those branch off into these tiny little capillary bundles, which can be called afferent arterioles. These afferent arterioles lead to the capillary bundles because arterioles branch off of arteries and lead to capillaries. The afferent arterioles get super tiny to the point where they're microscopic and they form little capillary bundles called glomeruli. The afferent arterioles are located in the cortex of the kidney and they branch off into millions of little bundles of capillaries. Blood leaves through the renal veins, which take blood out of the kidney that hasn't been filtered out to make urine. Blood flow is regulated by renal nerves. Nephrons are the little filtering units of the kidney where all the action happens. They are microscopic tubular structures in the cortex of the kidneys that do the filtering of blood and production of urine. There are approximately 1.25 million nephrons per kidney.

The glomerulus is a collection of capillaries where filtration takes place. Blood enters the glomerulus through the afferent capillary and exits through the efferent capillary. These capillaries have small holes in their cells, known as fenestrations, which allow solutes and water to easily pass through. This enables the filtration of small particles and essential nutrients such as glucose, fatty acids, amino acids, and vitamins. However, important nutrients are not completely lost as they are reabsorbed in the proximal convoluted tubule. The proximal convoluted tubule is the first part of the renal tubular system and is lined with a type of tissue called simple cuboidal epithelium. If you were to examine a cross-section of the proximal convoluted tubule, you would observe this specific tissue type.

The peritubular fluid is responsible for transporting substances back into the tube. This is the final opportunity to eliminate unwanted materials that have been reabsorbed from the tubular fluid. Once these substances are transported back into the distal part of the tube, they can enter the collecting system. This process is crucial because filtration alone is insufficient to remove waste products from the plasma. Without the ability to secrete, the amount of waste eliminated during urination would not be enough to maintain homeostasis. On average, urine consists of about 95 percent water, although this percentage can vary between 93 and 97 percent. The remaining five percent contains various components. Among the main players found in urine is urea, which is highly concentrated compared to other substances. Urea is derived from the breakdown of amino acids, which constantly occurs in the body. It serves as a means to eliminate waste, considering that amino acids are the building blocks of proteins. Additionally, creatinine is produced from the breakdown of creatine phosphate, which is found in muscles. Creatine phosphate plays a role in the rapid regeneration of ATP in muscles, as explained in muscular lessons. Lastly, uric acid is formed through the cycling of nitrogenous bases of RNA. The production of RNA is a continuous process in cells throughout life.

Uric acid is derived from the breakdown of RNA waste, and it contributes to the yellow color of urine. Euro billion, also known as euro chrome, refers to the color of urine. It is a byproduct of the breakdown of bilirubin, which also affects the color of fecal matter. The yellow color of urine is primarily due to the breakdown of bilirubin, which originates from the breakdown of red blood cells. These red blood cells contain heme groups that have a yellowish hue. Therefore, urine contains enough bilirubin breakdown products to give it a yellow color. Sometimes, urine may appear more clear, indicating a higher concentration of water. Clear urine can be a sign of being well-hydrated or even intoxicated, as alcohol impairs the antidiuretic hormone responsible for water retention in the kidneys. Despite the potential disgust some people may feel towards urine, it is actually sterile and free from bacteria when it leaves the body, unless there is a urinary tract infection present. In survival situations, drinking urine can be a way to replenish fluids temporarily, but it should be noted that this practice is not recommended for long-term survival as it does not provide new water to the body.