Blood is a blood fluid with specific functions. Give examples of the functions of blood in the animal body and explain how the animal body defends itself by against changes in H+ion concentration.
Blood is a vital fluid in the bodies of many animals, including humans, that carries out a multitude of essential functions. Some of the primary functions of blood include:
1. **Transportation**: Blood serves as a transport medium for various substances, including:
- Oxygen: Red blood cells contain hemoglobin, which binds to oxygen in the lungs and carries it to tissues.
- Nutrients: Blood carries nutrients absorbed from the digestive system to cells throughout the body.
- Metabolic wastes: Blood picks up waste products from cellular metabolism and transports them to organs such as the kidneys and liver for excretion or detoxification.
- Hormones: Hormones produced by endocrine glands are distributed via the bloodstream to target organs and tissues.
2. **Regulation**: Blood helps in the regulation of:
- Body temperature: Blood can absorb and distribute heat throughout the body, helping to maintain a stable internal temperature.
- pH balance: Blood buffers help maintain the pH of body fluids within a narrow range necessary for proper cellular function.
- Fluid balance: Proteins and salts in blood plasma help regulate the movement of water in and out of cells, maintaining the balance of bodily fluids.
3. **Protection**: Blood plays a role in:
- Immune response: White blood cells are part of the immune system and defend the body against pathogens and foreign particles.
- Clotting: Platelets and plasma proteins participate in the blood clotting process to prevent excessive blood loss from injuries.
The body maintains the pH of blood within a very tight range (typically around 7.35 to 7.45) because slight deviations from this range can have significant impacts on enzyme activity and overall cellular function. The body has several mechanisms to defend against changes in H+ ion concentration (i.e., maintaining acid-base balance):
1. **Buffer systems**: Blood contains several buffers that immediately neutralize small changes in pH. The bicarbonate buffer system, for instance, is essential for maintaining the pH of blood. This system operates according to the following reversible reaction, which can absorb excess H+ ions or provide them when needed:
HCO3^- (bicarbonate) + H+ (hydrogen ion) ↔ H2CO3 (carbonic acid) ↔ CO2 (carbon dioxide) + H2O (water)
Increase in H+ is countered by the reaction to the left, which forms more carbonic acid. Conversely, a decrease in H+ leans the reaction to the right, releasing H+ into the system.
2. **Respiratory compensation**: The respiratory system can adjust the rate and depth of breathing to either expel more carbon dioxide (which, as it reacts with water, generates H+ ions) or to retain it. Increasing the breathing rate reduces CO2 and, therefore, the concentration of H+ ions, raising the blood pH in the case of acidosis (too acidic). On the other hand, slowing breathing can help to lower the blood pH in the case of alkalosis (too basic).
3. **Renal compensation**: The kidneys also play a critical role in maintaining acid-base balance by excreting or retaining bicarbonate and hydrogen ions. In response to acidosis, the kidneys excrete more H+ and conserve bicarbonate, pushing the bicarbonate buffer equation to the left and raising blood pH. In alkalosis, they can retain H+ and excrete bicarbonate, increasing the acidity of the blood.
These mechanisms act together to prevent significant deviations from the normal range of blood pH, ensuring the proper functioning of cells and the entire organism.