Body Fluids

Fluids are water-based substances that contain ions and minerals that are essential for body functions and transport of minerals for metabolism. 

The fluids of the body are divided into two main divisions: intracellular fluid (inside the fluid cell) and extracellular fluid (outside the fluid cell). 

Intracellular fluids are present inside the cells. They have a low concentration of potassium and high concentration of sodium. They secrete fluid to maintain the osmotic pressure and environment inside the cell. 

Extracellular fluids flow around the cells and bathe them by supplying nutrients, oxygen, and taking out carbon dioxide with other waste products. Some of the extracellular fluids are plasma, interstitial fluid, lymph, and milk. 

Opening to body fluids

One of the extracellular fluids is blood. Blood is a special type of connective tissue, with constituents like plasma and other vital elements. 

Blood is the important common body fluid in higher organisms including humans. Blood acts as an intermediate in exchange for minerals, gases, waste, and minerals from organs outside the body. 

Lymph is also a body fluid that transports fats and proteins. Blood along with lymph helps in body fluid circulation. 

Notes on body fluids 

Blood

Blood is made up of connective tissue, and is composed of a fluid matrix, plasma, and blood corpuscles. The body’s extracellular fluid is made up of blood, which constitutes 30-35%. Its pH is 7.4, and it is alkaline in nature. 

Plasma

Plasma is a colourless or straw coloured viscous fluid that constitutes 55% of blood. Plasma is mainly composed of 90-92% of water, while the remaining 6%-8% is protein. 

The main components of protein in plasma are albumins, fibrinogen, globulins, some amino acids, glucose, and very small amounts of minerals such as Cl-, Mg++, HCO3, Ca++, Na+, etc. 

Role of proteins present in plasma

• Fibrinogen – clotting of blood in wounded areas of the body

• Globulin – defence mechanisms against pathogens

• Albumin – maintains osmotic balance of the blood plasma.

A plasma without clotting ability is called serum. 

Formed elements

About 45% of blood is composed of erythrocytes, leukocytes and platelets, which are collectively known as formed elements. 

• Erythrocytes or red blood cells (RBC) are abundant in the human body. RBCs are biconcave in shape, with the absence of a nucleus. RBCs are produced in the red bone marrow of the bone. A healthy individual has 5 million to 5.5 million RBCs in the blood. An RBC is rich in iron due to the presence of haemoglobin, which also gives blood its red colour. A healthy adult has 12-16 grams of haemoglobin in 100ml of blood. RBCs facilitate the transport of respiratory gases in the body. 

• Leukocytes or white blood cells (WBC) are colourless due to the absence of haemoglobin, short-lived, and fewer in number (from 6,000 to 8,000 mm-³ in blood) than RBCs. WBCs are divided into granulocytes and agranulocytes. Granulocytes are further classified into neutrophils, eosinophils, and basophils, and agranulocytes into lymphocytes and monocytes.

• Thrombocytes or platelets are fragments of cells present in the plasma that are responsible for blood coagulation. The smaller the number of platelets in the blood, the higher the risk of disorders and excessive loss of blood. 

Blood group types

Although blood appears in all individuals, it has different aspects. Blood groups are of two variants: ABO and Rh.

ABO group

This is based on the presence or absence of antigens such as antigen A and antigen B on the surface of the RBCs, whereas antibodies present in plasma are opposite to antigens. 

• For blood transfusion, the blood groups of the individuals are matched to avoid blood agglutination. 

• Individuals with blood group O can donate to anyone, and are called universal donors. 

• Persons with blood group AB can receive blood from anyone, and are called universal acceptors. 

Rh blood group 

First observed in the urine of Rhesus monkeys, it is present in the majority of humans. A person with an Rh antigen is called Rh+, while if absent, called Rh-. 

What Is the Role of the Rh Factor? The Rh factor is one of the proteins on RBCs that determines whether the blood of two persons is compatible when mixed – for example, the blood of a mother and her infant at delivery. During pregnancy, the Rh factor for both the mother and the unborn child is routinely determined.

Lymph

In blood capillaries, a colourless fluid flows between the cells and tissues, low in protein, phosphorus and calcium, and high in glucose; it is called lymph. It is known as tissue fluid or interstitial fluid. 

• The fluid contains lymphocytes, which act as the immune system in the human body.

• It carries and transports hormones, food molecules, and proteins. However, it mainly provides immunity. 

Potentially infectious body fluids

Blood fluids also contain bloodborne infectious pathogens that infect a human and transmit from one person to another. 

In short, bloodborne pathogens are microorganisms that when coming in contact with blood, cause risk to human life and are potentially infectious. 

The primary bloodborne pathogens are MRSA, Hepatitis B (HBV), and Human Immunodeficiency Virus (HIV). 

• Blood: It’s important to wear gloves and other protective equipment to prevent infection because handling contaminated blood or skin membrane is exposed or injuries due to sharp objects lead to the exposure of blood to outside pathogens. 

• Vaginal and semen secretions: Diseases such as HBV and HCV are transmitted through the secretion of vaginal or semen fluids. They spread not only during sexual intercourse, but also affect who ever comes in contact with the contaminated secretions. 

Contamination of other body fluids with bloodborne pathogens

Unlike HIV, these are unlikely to be exposed outside the hospital. But some may cause serious trauma. 

• Amniotic fluid: Fluid present in the amniotic sac that surrounds the fetus. 

• Pleural fluid: Fluid present on the outer membrane of the lungs.

• Cerebrospinal fluid: A clear, colourless fluid present in the spine and brain.

Potentially infectious diseases caused by body fluids

When a human comes into contact with pathogens, it can cause serious illness or even fatal death. The diseases include: 

• HIV

• HBV

• Relapsing fever

• Babesiosis

• Leptospirosis

• Type 1 Human T-lymphotropic virus

• Arboviral infections

• Viral hemorrhagic fever

• Syphilis

• Malaria

Conclusion

This article has dealt in detail with body fluids. Body fluids are one of the most important components of a completely healthy human body. This system has evolved from primitive animals such as the water canal system in Porifera and Coelenterata to well-developed fluid systems in humans such as the blood vascular system or human circulatory system. 

Each molecule present in body fluids has its unique role or function. The absence of any molecule or failure to function leads to disease and disorders. The mechanism of circulation runs due to the combined work of body fluids like blood, lymph and the heart.