Circulatory System Flashcards
What is the circulatory system?
The circulatory system is the system that circulates blood through the body, consisting of the heart, blood vessels, blood, lymph, and the lymphatic vessels and glands. It consists of both the open and closed circulatory systems.
Open circulatory system
Open circulatory systems circulate interstitial fluid throughout the body. They usually have low pressures and long circuit times and are often found in ‘simple’ organisms.
Closed Circulatory system
In a closed circulatory system, the blood is entirely enclosed within a system of vessels as it is pumped by the heart around the body. Because of this higher blood pressure is possible and faster circuit times and are often found in larger, more active organisms which need transport systems too meet cellular demand.
What is blood?
Mammalian blood is a fluid which contains cells and cellular fragments. The fluid portion is called plasma and the cellular part includes red and white blood cells and platelets.
Red blood cells
Red blood cells transport oxygen and co2 and are filled with hemoglobin molecules to enable the transport of respiratory gases.
White blood cells
White blood cells function in defense and are larger but fewer in number, i.e. phagocytes fight infection.
Platelets
Platelets are fragments of cells that are much smaller than red and white blood cells and they are involved in blood clotting and preventing blood loss.
what are blood vessels?
Blood vessels include arteries, veins and capillaries, all of which aid the flow of blood through the body.
What is the function of Arteries?
Arteries carry blood away from the heart and have thick muscular and elastic walls. Blood pressure in arteries is high due to the contraction of ventricles which keeps the blood flowing.
What is the function of Veins?
Veins transport blood to the heart. Pressure here is much lower so the flow is maintained by external compression by the skeletal muscles.
What are the function of Capillaries?
Capillaries are thin walled (one cell thick), highly branching network which provides surface area for the exchange of substances between plasma and interstitial fluid by diffusion. Blood pressure is higher at the start of the capillary and therefore water will diffuse out of the capillary at the arterial end and will diffuse in at the venous end.
Define systole
ventricles contracting, pushing out blood into arteries and there is high pressure in the aorta.
Define diastole
ventricles are relaxing and filling with blood, and there is lower pressure in the aorta.
HUMAN HEART
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