TRANSPORT IN HUMANS

By Giulia Corrado

The circulatory system

• This, with the heart and blood itself, is one of the most important things we need in our body in order to survive.

• This system is also known as “cardiovascular system” and is responsible for the transport of different substances (like oxygen, nutrients and water) through the whole body.

• As it transports these materials to our infinite number of body cells, it carries away wastes, such as carbon dioxide, that body cells produce.

• We can look at this immense system as a big and long freeway, where our main streets are the arteries and the veins. The arteries carry blood away from the heart, while the veins bring it towards the heart.

• The circulatory system consists into two circuits through which blood travels pulmonary and systemic circuit.

The pulmonary circuit

• It brings the blood to the lungs to be oxygenated and then back to the heart. The blood passes through the lungs so that carbon dioxide can be removed and oxygen taken in by the hemoglobin, which is found in the red blood cells.

• In this circuit pressures are lower because the pulmonary vascular resistance is lower and the capacitance of the system is higher.

• It has three main functions: blood filter, metabolic organ and gas exchange.

• What happens is that the pulmonary arterial pressure is generated by the right ventricle emitting blood into the pulmonary circulation, which acts as a resistance to the production of the right ventricle. With each ejection, the pulmonary arterial blood volume increases and this stretches the wall of the artery.

• As the heart relaxes blood continues to flow from the pulmonary artery into the pulmonary circulation.

THE SYSTEMIC CIRCUIT

• On the other side, in this circuit the blood is carried from the heart towards all of our body parts and returns as de-oxygenated. In this case, blood carries also nutrients and waste.

• In this circuit we find the most important artery present in our body: the Aorta, which is found next to the left lung.

• Here, the arterial blood pressure is generated by the left ventricle emitting blood into the systemic vasculature, which acts as a resistance to cardiac output. With each of these cycles, the aortic volume increases and stretches the wall of the aorta.

• As the heart relaxes blood flows from the big vein into distributing arteries that transport the blood to the various organs.

THE HEART

• The heart is a very strong and big muscular pump, which spurts blood around the body and to the lungs. It beats about 70 times per minute and the first beat is when it pumps blood to the lungs to be oxygenated and then returns to the heart. Here comes the second pump where the blood is sent from the heart to the whole body. The cycle then starts again.

• The muscular wall of the heart is the myocardium, which contracts to pump blood out of the heart and then relaxes as the heart refills with the returning blood. It has a smooth outer membrane, which is called epicardium, and an inner part, which is called endocardium.

• Then there are the four chambers: the two atria collect blood, while the two ventricles pump the blood out of the heart.

• Also the valves have an important job, which is to prevent blood from flowing backwards.

• The central part which separates the heart is called the septum.

• Then there are three varieties of blood vessels arteries, veins and capilleries. During circulation arteries, which have thick muscular walls, carry blood away from the heart. They are connected to the veins by the capillaries, found in the muscles and lungs, in which gas exchange takes place. To conclude there are the veins, with thin muscular walls, carry the blood back to the heart.

• CORONARY HEART DISEASE

• This is a narrowing of the small blood vessels that supply blood and oxygen to the heart.

• It can also be called the “ coronary artery disease”, where plaque, made of fat and cholesterol, biulds up in the arteries during the years. It gets harder and narrows the space for the flow of blood going to the heart carring oxygen.

• Causes diet, stress and smoking

• Preventions regular exercise, mantaining a healthy weight and monthly heart screenings

Functions of the heart

• The heart is the biggest and strongest muscular organ found in our body and it is a type of involuntary muscle.

• As it is a muscle, it generates rhythmical electrical impulses to cause rhythmical contraction of it and conducts these impulses rapidly through the whole heart.

• Heart valves function to ensure a one-way flow of blood through the heart. The valves are not made of muscle, but rather are composed of sheets of tough connective tissue (leaflets) that act like flaps. The heart valves open and close passively because of pressure differences on either side of the valve. When pressure is greater behind the valve, the leaflets are blown open and the blood flows through the valve. The opposite happens when the pressure is lower behind the valve.

Physical activity and pulse rate

• While the people in the picture you just saw were running, their pulse rate increased. This is because the heart has to work harder to pump blood to the working muscles which require more oxygen to produce extra energy.

• The heart can beat up to 200 times per minute with extreme exercise. The brain sends nerve signals to the heart to control the rate. The body also produces chemical hormones, such as adrenaline, which can change the heart rate.

• During each heartbeat, the muscles of the heart contract causing a wave of pressure which forces blood through the arteries. This is known as a pulse. And there is one for each heartbeat.

• In addition, when exercising blood removes heat and regulates the body temperature.

Bloooooood!

• Blood occupies about the 7% of our body and it is equal to about 5 LITRES of fluid in an average adult person. This in fact changes depending on the height and weight of a single person.

• It can be divided into four main components: red blood cells, white blood cells, plasma and platelets.

• RED BLOOD CELLS they contain haemoglobin, which carries oxygen. They are made in the marrow bone through a process called erythropoiesis.

• WHITE BLOOD CELLS they play an important role in the immune system because they produce antibodies and destroy any harmful microorganism. Also they, are formed in the marrow bone.

• PLATELETS they group together to form various lumps (clots). In fact, they protect the body from excessive bleeding. They are a solid part of the blood.

• PLASMA 97% of it is made of water and the other 3% is formed by antibodies, nutrients, waste and proteins. In fact, it carries the albumin and the globulins serum proteins. It is the fluid part of the blood and it carries also carbon dioxide.

Under the light of microscope…

Red blood cells White blood cells

THANK YOU FOR WATCHING

THE END