What are red blood cells?

 ANIRUDH 

Red blood cells, also known as erythrocytes, are the most abundant type of blood cell in the human body, accounting for around 45% of the total blood volume. They are responsible for carrying oxygen from the lungs to the body’s tissues and removing carbon dioxide from those tissues to be exhaled from the body. Red blood cells have a unique structure that enables them to perform these vital functions.

Structure of Red Blood Cells

Red blood cells are biconcave discs, which means they have a concave shape on both sides. This shape gives them a large surface area-to-volume ratio, allowing for efficient gas exchange. The cells are around 7.5 micrometers in diameter and 2.5 micrometers thick at their thickest point.

The outer membrane of a red blood cell is composed of lipids and proteins that allow for flexibility and deformability. This flexibility is crucial as red blood cells need to be able to navigate through small capillaries in the body’s tissues. If red blood cells were rigid, they would not be able to pass through these narrow spaces, causing blockages and tissue damage.

The inner contents of a red blood cell are mainly made up of hemoglobin, a protein that binds with oxygen and carbon dioxide. Each red blood cell contains approximately 270 million molecules of hemoglobin. Hemoglobin gives red blood cells their characteristic red color and also allows them to transport oxygen and carbon dioxide.

Life Cycle of Red Blood Cells

Red blood cells have a life span of around 120 days in the human body. They are constantly being produced in the bone marrow and released into the bloodstream. However, as red blood cells age, they become less flexible and more rigid, making it harder for them to pass through the narrow spaces in the body. This is why old red blood cells are removed from circulation by the spleen and liver.

The process of removing old red blood cells from circulation is known as erythrophagocytosis. The spleen and liver contain macrophages, which are specialized cells that engulf and digest old and damaged red blood cells. The heme portion of hemoglobin is broken down into bilirubin, which is excreted in bile and gives feces their brown color. The iron from hemoglobin is recycled and used to produce new red blood cells.

The function of Red Blood Cells

The primary function of red blood cells is to transport oxygen from the lungs to the body’s tissues and carbon dioxide from the tissues to the lungs. This process is known as gas exchange and is vital for the survival of all cells in the body. Without red blood cells, oxygen and carbon dioxide could not be transported efficiently, leading to tissue damage and cell death.

The process of gas exchange occurs in the lungs and body tissues. In the lungs, red blood cells pick up oxygen from the alveoli, which are small air sacs in the lungs. Hemoglobin shackles with oxygen to form oxyhemoglobin. This process is reversible, which means that when red blood cells reach the body’s tissues, they release oxygen, allowing it to diffuse into the cells.

In the body’s tissues, red blood cells pick up carbon dioxide, which is a waste product of cellular metabolism. Hemoglobin binds with carbon dioxide to form carbaminohemoglobin. This process is also reversible, which means that when red blood cells reach the lungs, they release carbon dioxide, allowing it to be exhaled from the body.

Red blood cells also play a role in maintaining the body’s acid-base balance. The hemoglobin in red blood cells can act as a buffer, which means it can bind with excess hydrogen ions in the blood, preventing a decrease in pH.