Functions of the Kidneys
1. Filtration of Blood:
The primary function of the kidneys is to filter waste products and excess substances from the blood, which are then excreted as urine.
This process is vital for cleansing the blood and preventing waste buildup in the body.
2. Regulation of Blood Volume and Pressure:
By adjusting the amount of water excreted in urine, the kidneys regulate blood volume and, consequently, blood pressure.
They can also secrete the enzyme renin, which helps regulate blood pressure through the renin-angiotensin-aldosterone system (RAAS).
3. Electrolyte Balance:
The kidneys help maintain the balance of electrolytes in the body, including sodium, potassium, and calcium, by filtering excesses from the blood for excretion or reabsorbing them as needed.
4. Acid-Base Balance:
By excreting hydrogen ions and reabsorbing bicarbonate from urine, the kidneys contribute to the regulation of the body's pH level, ensuring it remains within a healthy range.
5. Erythropoiesis Regulation:
The kidneys produce and release erythropoietin, a hormone that stimulates the production of red blood cells in the bone marrow in response to hypoxia (low oxygen levels in the blood).
6. Detoxification:
While the liver plays a primary role in detoxification, the kidneys also remove various toxins from the blood during the filtration process.
7. Metabolite and Bioactive Substance Regulation:
The kidneys filter out and excrete metabolites (e.g., urea and creatinine) and other bioactive substances, such as hormones, thereby regulating their levels in the body.
Functions of the Urinary Tract
The urinary tract includes the ureters, bladder, and urethra, which work together to transport, store, and eliminate urine:
1. Transportation of Urine:
The ureters transport urine from the kidneys to the bladder through peristaltic waves.
This process is crucial for moving urine in the right direction and preventing backflow.
2. Storage of Urine:
The bladder serves as a temporary reservoir for urine, allowing for controlled urination.
It can expand significantly to store urine until it is convenient to excrete it.
3. Controlled Excretion of Urine:
The process of urination involves the coordinated action of the urinary sphincters and the detrusor muscle of the bladder.
The internal sphincter (involuntary) and the external sphincter (voluntary) control the release of urine from the bladder.
The urethra then transports urine out of the body.
4. Prevention of Infection:
The urinary tract plays a role in preventing infections by flushing out pathogens with the flow of urine. Additionally, various mechanisms, including the urethra's length and the valves in the ureters, help prevent the backflow of urine, reducing the risk of infections reaching the kidneys.
