How does the Excretory System work with the Circulatory system

The excretory system works intricately with the circulatory system to optimize body physiology and maintain homeostasis.

The functions of the circulatory system are

1. Transport of oxygen to all the body cells
2. Removal of excess Carbon Dioxide from the body.
3. Maintain uniform body temperature
4. Supply nutrients and hormones to target cells
5. Carry waste to the excretory organs.

The excretory system functions to

1. Remove excess carbon dioxide from the body
2. Expel unwanted waste from the body
3. Dissipate excess body temperature
4. Ensure optimal concentration of electrolytes.
5. Maintain the pH of various body fluids

Components of the excretory system:

1. Urinary system: Kidneys, ureters, urinary bladder, and urethra
2. Liver
3. Lungs
4. Skin

Components of the circulatory system 

1. Heart
2. Blood vessels: Arteries, veins, and capillaries

Hence, called the cardio-vascular system (CVS)

How does the Excretory System work with the Circulatory System

• Both systems are connected to each other through the blood.

• The circulatory system performs its functions through proper blood distribution.

• In doing so, the blood collects waste from all the body parts.

• This waste in blood is removed by excretory organs, thereby maintaining the overall function of the circulatory system.

• Without this excretory system, the circulatory system would lose its ability to perform effectively and also lose its healthy anatomical structure.

• Excretory systems help the circulatory system to remain effective in delivering the functions needed to maintain body physiology and homeostasis.

It helps the circulatory system in different ways, like

1. Transport of Oxygen.

• The circulatory system delivers oxygen-rich blood to all the cells and tissues through the capillaries.

• This ability is dependent on blood pH and hemoglobin levels in red blood cells.

HBO ⇄ HB + O

Blood pH effects:

• pH of blood and other body fluids is critical for optimal physiology. It relies on H⁺ ion concentration.

• This pH is dependent on CO₂ levels, which are expelled by lungs and by kidneys as carbonate ions (HCO^–).

• As per the Bohr effect, at lower pH, hemoglobin’s affinity towards oxygen decreases, and at higher pH, it increases.

• So, both acidosis and alkalosis can affect Oxygen binding and release with hemoglobin.

• Hence, lungs and kidneys as excretory organs regulate pH, and thereby oxygen levels that impact the CVS.

• If oxygen levels are low, the heart rate is high to supply sufficient oxygen to tissues, causing strain on it.

2. Removal of waste.

• Cells and tissues produce waste as a part of regular metabolism, such as urea, uric acid, creatinine, etc.

• These waste materials are toxic to the body and have to be expelled in time. 

• Failure to expel by the excretory organs can damage the circulatory system’s structure and efficiency.

• For example, excess urea in blood can cause damage to blood vessel wall linings, causing capillary leakage and inflammation.

3. Temperature regulation

• The CVS, with the control of the temperature regulating center in the brain, tries to maintain uniform body temperature in the body.

• When the body temperature is high, the CVS distributes blood towards the skin to enhance sweating to cool down.

• But, if this mechanism of temperature normalisation fails, there could be issues like

1. Low Oxygenation of blood: At high temperatures, the binding of hemoglobin with O2 decreases. 
2. Increases heart rate (to expel heat from skin), leading to strain
3. Heat stroke can occur, leading to organ damage.

4. Blood Pressure Optimization

• When blood pressure falls, the kidneys release renin.

• This renin converts angiotensinogen to angiotensin, which further undergoes changes to enhance blood pressure by constricting blood vessels.

• Thus, it helps to regulate the blood pressure and thereby maintain sufficient blood perfusion by the CVS.

• Without sufficient BP, the perfusion of tissue decreases, leading to stroke, fainting due to poor oxygen supply.  

5. Electrolyte balance

• Excretory system organs like the kidneys and skin help maintain electrolyte levels in the body.

• The electrolytes like Na⁺, Mg⁺², Ca⁺², K⁺, etc., can be expelled through urine as a part of blood filtration.

• However, the nephrons reabsorb them back into the blood to maintain homeostasis.

• Na⁺ is essential to maintain blood volume. If Na⁺ decreases, blood volume decreases, leading to a fall in BP.

• Similarly, loss of K⁺ causes arrhythmias (irregular heartbeats)

• Besides, excess Phosphates can cause hardening of blood vessels, which can strain the heart.

• Thus, maintenance of electrolyte levels by the excretory system helps safeguard the circulatory system and its efficiency.

6. Lipid levels for healthy CVS

• The liver is an important organ of lipid metabolism that also acts as a supportive excretory organ.

• It is essential for the reduction of harmful lipids, which can damage blood vessels and the heart.

• When the liver malfunctions, the low-density lipoproteins (LDL) can increase, which can cause atherosclerosis and a heart attack.

7. Water balance

• Water levels in the body are regulated by the kidneys and the skin.

• High water levels can increase BP and even lead to ascites (accumulation). 

• On the contrary, low water levels can decrease blood volume and BP, which can also increase heart rate.

References:

• What are Heart Disease and Stroke?