[Biology Class Notes] on Human Circulatory System Pdf for EXAM

The human body has several different processes that happen at the same time. These processes are vital in our body to happen to keep us alive.

The circulation of blood in a human body is essential to have enough oxygen to reach different cells. This particular oxygen is then used by our cells for other purposes, including respiration. Respiration is a critical process in our human body to carry out various life functions.

This image above shows a circular human system. The human circulatory system is an intricate network of arteries, capillaries, and veins. Our heart is a fist-sized organ that is located in our rib cage, and slightly tilted towards the left. It is an organ that pumps blood from our body.

Composition of the Human Circulatory System

We can classify these tissues into two parts, Meristematic Tissues, and Permanent Tissues.

The human circulatory system comprises very vital organs with various functions to perform.

These important organs are:

Heart: The heart is a four-chambered organ that is present inside our rib cage. It is the size of our first and is made up of special muscles known as cardiac muscles.

The upper two chambers of the heart are called The Auricles and lower chambers are known as Ventricles.

Human beings have a complex circulation which is also known as a double circulation. In this circulation the blood flows through the heart two times. 

This type of circulation is vital for our body as our human body is larger than other animals and needs oxygen-rich blood to flow throughout the body.

It is divided into four chambers by a division known as the septum. In this structure of the heart, the left side has pure oxygenated blood flowing through it, whereas the right side carries the deoxygenated or the carbon dioxide-rich blood. Among the auricles and the ventricles, one valve is there on each side. 

The valves are responsible for the unidirectional flow of blood. When the blood flows through the ventricles, these valves close up so that there is not any backflow.

There is a lub-dub sound that is produced as these valves open and close. This sound is known as the heartbeat.

Lymphatic System: Our human body has other fluids than the blood; these are called lymph. They are a tissue just like the blood, but it is a colorless liquid that is responsible for transporting fats and absorbed foods to intercellular areas.

Blood: Speaking of fluids in our body, Blood is the most important one. It is not an organ but a connective tissue that has a composition of blood cells, plasma, floating proteins and other minerals.

Blood is made up of different types of cells, platelets, and plasma:

Plasma is the fluid content of the blood which makes about 90% of its structure. 

Red Blood Cells (RBCs): They are also known as Erythrocytes and transport oxygen to our entire body. They contain the important protein Haemoglobin, which when combined with Oxygen, creates a compound called Oxyhaemoglobin.

People with a higher amount of Haemoglobin are usually more active because oxygen reaches all parts of their body quickly, which as a result, produces more energy.

White Blood Cells (WBCs): They are also known as Leukocytes and are responsible for forming our body’s defense mechanism. These blood cells help us fight against foreign pathogens and build up our immunity.

Platelets: They are also called Thrombocytes, and help during an energy to create blood clots so that excessive blood does not flow out of our body.

Blood Vessels: Blood Vessels are tube-like structures responsible for the flow of blood in the body. There are two types of blood vessels present in our body:

Arteries: They are responsible for carrying the oxygenated blood from our heart to other organs of our body. Blood flows through our arteries at tremendous pressure. This is the reason why our arteries have thick and elastic walls. They are located deep below our skin.

Veins: They are responsible for carrying the deoxygenated blood from the cells in our body back to the heart. The pressure of the flowing of blood in them is lesser than the arteries. They are located near the surface of our skin, and we can also see them in our bodies.

Functions of the Human Circulatory System

The human body has a complex circulatory system that has the following functions:

• It maintains the blood supplied to all the organs of our body.

• It transports nutrients like oxygen-carbon dioxide and hormones to various cells and organs.

• It protects our body from any new disease-causing microorganisms.