Blood: Definition & Composition

Blood is a vital fluid in the human body that circulates through the heart, vessels, and organs, transporting oxygen and nutrients to the cells and removing waste products. It also plays a crucial role in maintaining body temperature and defending against infection. Blood is made up of various components, including red blood cells, white blood cells, platelets, and plasma.

Blood is made up of various components, including red blood cells, white blood cells, platelets, and plasma. Red blood cells, also known as erythrocytes, contain hemoglobin, a protein that binds to oxygen and transports it to the body’s cells. White blood cells, also known as leukocytes, help to defend the body against infection and disease. Platelets, also known as thrombocytes, are involved in blood clotting, which helps to stop bleeding when the body is injured. Plasma, which makes up about 55% of blood, is a yellowish fluid that contains water, electrolytes, and dissolved proteins. Blood also plays a role in the immune system, transporting hormones and other signaling molecules, and helping to regulate body temperature.

Composition of Blood

The composition of blood includes several important elements:

1. Red blood cells (erythrocytes): These cells contain hemoglobin, a protein that binds to oxygen and transports it to the body’s cells. They make up about 40-45% of blood volume.
2. White blood cells (leukocytes): These cells help to defend the body against infection and disease. They make up about 1% of blood volume.
3. Platelets (thrombocytes): These cells are involved in blood clotting, which helps to stop bleeding when the body is injured. They make up about 1% of blood volume.
4. Plasma: This is the yellowish fluid that makes up about 55% of blood. It contains water, electrolytes (such as sodium and potassium), and dissolved proteins (such as albumin and globulins).
5. Hematocrit: It is the percentage of red blood cells in the blood.
6. Hemoglobin: It is a protein in red blood cells that binds oxygen and carbon dioxide.
7. Erythrocyte sedimentation rate (ESR): It is a measure of how quickly red blood cells settle to the bottom of a tube.
8. Leukocyte count: This is a measure of the number of white blood cells in a sample of blood.

All of these elements work together to help transport oxygen and nutrients to the body’s cells, remove waste products, and defend against infection.

What hemoglobin is and its function?

Type of Blood cells

There are three main types of blood cells: red blood cells, white blood cells, and platelets.

1. Red blood cells (erythrocytes): These cells contain hemoglobin, a protein that binds to oxygen and transports it to the body’s cells. They are responsible for carrying oxygen from the lungs to the body’s tissues.
2. White blood cells (leukocytes): These cells help to defend the body against infection and disease. They are part of the immune system and can be classified into five types: neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
3. Platelets (thrombocytes): These cells are involved in blood clotting, which helps to stop bleeding when the body is injured. They are small, disk-shaped cell fragments that are important in the process of hemostasis, which is the body’s natural mechanism to stop bleeding.

All these cells are produced in the bone marrow, which is the spongy tissue inside the bones. They are constantly replaced as they die and new cells are produced. Abnormalities in the numbers or function of these cells can indicate a variety of health conditions.

Formation of Blood

The formation of blood, also known as hematopoiesis, occurs in the bone marrow, which is the spongy tissue inside the bones. The bone marrow contains stem cells, which are immature cells that have the ability to differentiate into different types of blood cells.

The process of hematopoiesis is regulated by various hormones and growth factors, and it involves the following steps:

1. Hematopoietic stem cells differentiate into multipotent progenitor cells, which can give rise to either red blood cells, white blood cells, or platelets.
2. Progenitor cells differentiate into committed precursor cells, which are specific to each cell line.
3. Precursor cells differentiate into immature cells, which are capable of further maturation and eventual release into the bloodstream.
4. Immature cells mature into their final form, such as red blood cells, white blood cells, or platelets, and are released into the bloodstream.

The process of blood cell formation is a continuous process, as cells are constantly dying and being replaced by new cells. The balance between cell production and cell loss is carefully regulated to maintain normal blood cell counts.

Hematopoiesis is controlled by different hormones, growth factors and chemicals and cells at different stages of maturation are under the control of different transcription factors, that activate or inhibit the expression of certain genes, allowing the cell to mature into a specific type of blood cell.

Function of Blood

Blood plays several important roles in maintaining the health and function of the human body. Some of the main functions of blood include:

1. Transporting oxygen and nutrients: Blood carries oxygen from the lungs to the body’s tissues and carries carbon dioxide and other waste products back to the lungs to be exhaled. Blood also carries nutrients such as glucose and amino acids to the body’s cells, and hormones and other signaling molecules to the organs.
2. Maintaining body temperature: Blood helps to regulate body temperature by carrying heat from the core of the body to the surface, where it can be dissipated.
3. Defending against infection: Blood contains white blood cells, which are part of the immune system and help to defend the body against infection and disease.
4. Blood clotting: Blood contains platelets, which are involved in blood clotting, which helps to stop bleeding when the body is injured.
5. Regulating pH: Blood plays an important role in regulating the pH of the body’s tissues, which is crucial for maintaining proper cellular function.
6. Removing waste products: Blood carries waste products such as carbon dioxide and nitrogenous waste to the kidneys and liver, where they can be filtered and eliminated from the body.
7. Regulating fluid balance: Blood helps to regulate fluid balance in the body by removing excess fluid and returning it to the circulatory system.

All these functions are interrelated and are important for maintaining homeostasis and overall health, and any disruptions in these processes can lead to serious health problems.