Body fluids and circulation definition

Body fluids

The body of almost all living beings has some sort of fluid circulating in their body. Fluids such as blood, lymph, milk, saliva, gastric juices, etc. are produced in the body. It is either circulated within the body or secreted outside it. The two most important body fluids in the body are blood and lymph.

Circulation 

Circulation is the movement of fluid, especially blood, through the vessels of the body. It is one of the most important functions that are carried out inside the human body and helps to sustain other functions within the same.

Body fluids and circulation classification

Now that we know what body fluid and circulation entails, let’s delve deeper into body fluids and circulation classification.

Types of body fluids

Blood: It is a body fluid present in living organisms (humans and other animals) that delivers necessary nutrients and oxygen to the cells and carries out the carbon dioxide and waste products produced by the same cells. This unique fluid connective tissue is made up of blood cells (RBC, WBC and Platelets) and plasma which circulate through the body in the arteries and veins by the circulatory system. 

It is produced in the bone marrow, especially the vertebrae, ribs, hips, skulls and sternum. It functions in two directions: arterial and venous. Arterial blood carries oxygen and nutrients which are transported to the tissues while venous blood carries carbon dioxide and metabolic by-products which are transported to the lungs and kidneys, respectively, for removal of the waste products from the body. 

Lymph: It is a colourless fluid also known as lymphatic fluid, containing plasma and a lesser amount of WBC’s and platelets present in the interstitial tissues. Lymph is derived from blood plasma as fluids pass through capillary walls at the arterial end. It circulates through the lymphatic vessels, unlike blood vessels, which only carry fluid away from the tissues and supplies nutrition and oxygen to the part of the body where blood cannot reach.  

Composition of body fluids

The body fluid within the cell is mainly composed of water dissolved ions and other molecules. Human cells are bathed in fluid, both inside and outside of the cell. The total body fluid is distributed mainly in two compartments: Extracellular fluid (26%) and Intracellular fluid (67%). There is another small fluid compartment referred to as Transcellular fluid (TCF). ICF and ECF help in keeping the body hydrated, and help in important fluid and renal functions of the body.

• Extracellular fluid (ECF): All the fluid present outside the cell is collectively known as extracellular fluid. They help to control the movement of water and electrolytes throughout the body
• Intracellular fluid (ICF): All the fluid present inside the cells is collectively known as intracellular fluid. ICF contains solutes and proteins. The solutes are electrolytes, which when dissolved in fluid break up into ions. This helps to keep our bodies functioning properly. There are lots of electrolytes present inside the cell, but potassium, magnesium, and phosphate have the greatest concentration
• Transcellular fluid (TCF): It includes fluid in the synovial, peritoneal, pericardial and intraocular spaces, as well as the cerebrospinal fluid

Functions of body fluids:

• Transport of body fluid: Facilitates the transportation of oxygen and nutrients throughout the body and elimination of the waste products from the body
• Temperature regulation: Helps in regulating the body temperature
• Maintain Consistency of Internal Environment: body fluid properties are kept to maintain an efficient metabolism

The cardiovascular system

It is a closed system of vessels called arteries, veins, and capillaries. They all are connected to a muscular pump known as the “Heart”. The cardiovascular system keeps a controlled and continuous movement of blood that delivers oxygen and nutrients to the cells of the body and carries out the carbon dioxide and waste products from the body.

Arteries (which carry blood away from the heart): The “pulmonary arteries” carry deoxygenated blood from the right ventricle of hearts and lungs whereas “systemic arteries” transport oxygenated blood from the left ventricle of the heart to the rest of the body.

Veins (which return blood from the heart): The “Pulmonary veins” carry oxygenated blood from the lungs to the left atrium of the heart wherein “systemic veins” carry deoxygenated blood from the body to the right atrium of the heart.

Capillaries: These are the smallest and most numerous of the blood vessels. The connection between the arteries and the veins. Its primary function is to exchange the materials like oxygen, between the blood and tissue cells.

Heart: The heart contains four chambers named right atrium, right ventricle, left atrium and left ventricle. It helps to pump and circulate blood through the cardiovascular system. 

Mechanism of circulation

The heart is the main organ that helps in the circulation of blood throughout the body. It consists of four chambers, two upper chambers called “atria” and two lower chambers called “ventricles”.

Arteries are responsible for carrying oxygen-rich blood, referred to as “oxygenated blood” away from the heart to various parts of the body. Veins carry blood low in oxygen, referred to as “deoxygenated blood” from the body back to the heart. They are part of two closed systems of tubes that starts and ends at the heart:

• Pulmonary: Pulmonary arteries carry oxygen-poor blood from the heart’s right ventricle to the lungs wherein pulmonary veins transport oxygen-rich blood back to the heart’s left atrium
• Systemic: Systemic arteries carry oxygen-rich blood from the heart’s left ventricle to the tissues of the body and return oxygen-poor blood through the veins back to the heart’s right atrium

During circulation, some fluid is forced out of the bloodstream which gets filtered by the lymph nodes to remove the bacteria and other matter. Then the filtered fluid is transported back into the bloodstream via lymph vessels.