Blood Biochemistry

### Blood: Functions and Components Blood is essential for life, serving three primary functions: **transport**, **protection**, and **regulation**. Through a complex system of cells, proteins, and plasma, blood sustains physiological balance and enables critical biological processes. --- #### Functions of Blood **1. Transport** Blood serves as the primary transport medium within the body, ensuring the distribution of gases, nutrients, waste products, hormones, and heat: - **Gases**: Blood transports oxygen (O₂) from the lungs to tissues and carries carbon dioxide (CO₂) from tissues back to the lungs for exhalation, maintaining cellular respiration. - **Nutrients and Waste**: Nutrients from digested food are delivered to cells for energy and growth, while metabolic waste products, such as **ammonia** and **creatinine**, are directed to the kidneys and liver for detoxification and excretion. - **Hormones**: Blood acts as a transport network for hormones, allowing organs and glands to communicate with distant tissues, coordinating essential body functions. - **Heat**: Blood distributes heat generated in tissues, particularly in **brown adipose tissue** found around areas like the neck and spine, which is important for regulating body temperature. **2. Protection** Blood plays a protective role in the immune system and in preventing blood loss: - **Immune Defense**: Blood contains white blood cells (WBCs), antibodies, and other immune proteins that identify and neutralize pathogens, protecting the body from infections. - **Inflammation and Healing**: Blood transports inflammatory molecules, such as **histamine**, to injury sites, promoting an immune response. Proteins in blood also initiate wound healing processes. - **Clotting**: Platelets and clotting factors within the blood trigger the formation of clots at injury sites, preventing excessive blood loss and facilitating tissue repair. **3. Regulation** Blood is essential for regulating various physiological balances within the body: - **pH Balance**: Through buffer systems like **carbonic acid**, blood maintains a stable pH range between 7.35 and 7.45, which is critical for enzymatic and cellular function. - **Water Balance**: Blood helps regulate the distribution of water across cells, tissues, and organs, maintaining fluid balance and preventing dehydration or fluid overload. - **Electrolyte Composition**: Plasma in the blood manages electrolyte levels, ensuring that minerals like sodium, potassium, and calcium are at optimal concentrations for cellular function. --- #### Components of Blood Blood consists of two main components: **plasma** and **formed elements**. **1. Plasma** Plasma, a yellowish fluid, constitutes about 55% of blood volume. It provides a medium for blood cells to circulate and carries a variety of substances necessary for body function: - **Proteins**: Plasma contains several proteins, including **albumin, globulins, and fibrinogen**, each serving specific roles in osmotic pressure, immunity, and clotting. - **Nutrients, Enzymes, and Waste Products**: Plasma distributes essential nutrients, enzymes, hormones, and waste products throughout the body for cellular function and detoxification. - **Serum**: Serum is plasma with the clotting factors removed and is commonly used in diagnostic testing. **2. Formed Elements** The formed elements in blood include **erythrocytes (red blood cells)**, **leukocytes (white blood cells)**, and **platelets**: - **Erythrocytes**: Red blood cells are responsible for carrying oxygen to tissues and removing carbon dioxide. Their biconcave shape maximizes surface area, allowing efficient gas exchange. - **Leukocytes**: White blood cells defend the body against pathogens. They are a key component of the immune system, with several types specialized in targeting specific infections or foreign substances. - **Platelets**: Platelets are small cell fragments essential for blood clotting and wound healing. When activated, they aggregate at injury sites, forming clots that prevent excessive blood loss. --- #### Plasma Proteins and Their Functions Plasma contains various proteins that fulfill important roles in transport, immunity, and coagulation. **1. Albumin** Albumin is the **most abundant and smallest plasma protein**. It performs several critical functions: - **Osmotic Pressure**: Albumin helps maintain **oncotic pressure**, preventing fluid from leaking out of blood vessels into surrounding tissues. When albumin levels are low, fluid can accumulate in tissues, leading to edema. - **Transport Function**: Albumin also acts as a transport protein, binding to various nonpolar substances and carrying them through the bloodstream. These include: - **Fatty Acids** and **bilirubin** - **Steroid hormones** and **pharmaceuticals** (e.g., narcotics) - **Hormones** that are not water-soluble, enabling their distribution to target tissues **2. Globulins** Globulins are a diverse