Tell whether each of the following substances that is filtered from the blood in the glomerulus is reabsorbed, excreted as part of the urine, or both
I PUT BOTH
To determine whether each substance is reabsorbed, excreted, or both, we need to understand the basic process of filtration and reabsorption in the kidneys.
The glomerulus is a network of tiny blood vessels located in the kidney. It acts as a filter, allowing small molecules and waste products to pass through into the renal tubules while retaining larger molecules such as proteins and blood cells.
Substances that are filtered from the blood in the glomerulus can either be reabsorbed back into the bloodstream or excreted as part of the urine. Reabsorption occurs mainly in the renal tubules, where certain substances are selectively transported back into the bloodstream. Excretion, on the other hand, refers to the elimination of waste products and certain substances through the urine.
Now let's go through some common substances and determine whether they are reabsorbed, excreted, or both:
1. Glucose: Normally, glucose is almost completely reabsorbed in the renal tubules. However, in certain conditions such as diabetes, when glucose levels in the blood are high, the capacity for reabsorption can be exceeded, leading to glucose being excreted in the urine. So, glucose can be both reabsorbed and excreted.
2. Water: Water is highly regulated in the kidneys. Under normal conditions, most of the filtered water is reabsorbed back into the bloodstream in the renal tubules. This allows the kidneys to maintain fluid balance in the body. So, water is primarily reabsorbed.
3. Urea: Urea is a waste product formed in the liver from the breakdown of proteins. It is filtered in the glomerulus and most of it is reabsorbed in the renal tubules, as the body can reuse urea. However, a small amount is excreted in the urine. So, urea is primarily reabsorbed.
4. Creatinine: Creatinine is a waste product of muscle metabolism. It is filtered in the glomerulus and excreted in the urine without significant reabsorption. So, creatinine is primarily excreted.
5. Sodium: Sodium is an essential electrolyte that plays a crucial role in maintaining fluid balance and blood pressure. It is mainly reabsorbed in the renal tubules to maintain sodium homeostasis in the body. However, some sodium can also be excreted in the urine. So, sodium is primarily reabsorbed.
Note that the reabsorption and excretion of substances can be influenced by various factors, including hormonal regulation, the body's needs, and certain medical conditions. Therefore, there may be exceptions or variations in specific cases.