Circulatory system
From CreationWiki, the encyclopedia of creation science
The Circulatory system is an organ system that helps maintain homeostasis. It delivers gases, helps with the regulation of temperature, and the transport of nutrition and waste.[1] It is also known as the cardiovascular system (Kardia means heat in Greek and vasculum means small vessel in Latin).
It consists of heart, blood, and blood vessels. There are two different types of the circulatory system: open circulatory system and closed circulatory system.[2] Most of vertebrates have a closed circulatory system, whereas most invertebrate have an open circulatory system.[1]
Contents |
System Types
Closed
Closed circulatory system separates the tissue fluid from blood. The heart pumps (vascular system) blood to send everywhere in the body. Vertebrates have closed circulatory system, and some of invertebrates have it.
The earthworm is an example of an organism with a closed circulatory system. When the heart (five pairs of connecting vessels) pumps blood, blood transfers from anterior end to posterior end. Ventral vessels carry oxygen, nutrients, and wastes. Dorsal vessels allow the blood move from the posterior end to the anterior end.
The closed circulatory system has more advantages than the open circulatory system. Some of the advantages are:
- The blood can transfer faster in the closed circulatory system. Therefore, oxygen, nutrients, and wastes can transport fast.
- Specialized cells help to carry hormones or nutrients. They keep those in the vessels, and at certain place they leave those.
- The blood and the tissue fluid can be distinguished easily.
Because the closed circulatory system can transport oxygen, nutrients, and wastes rapidly, the organisms can maintain high metabolic activities.[3]
Open
Open circulatory system is simple. It is called the open circulatory system, because tissue fluid and blood cannot be distinguished. Blood and tissue fluid are pumped by the heart and they transfer through the vessels. After they circulate all body through the vessels, they go back to the heart.
Arthropods and mollusks have the open circulatory system and few of the invertebrates have this system. Arthropods have ostia, which is little valve openings that allow the tissue fluid to go back to the heart. Mollusks do not have ostia as arthropods, but they have open vessels that help the tissue fluid returns to the heart.[4]
None
Some of organisms, especially simple aquatic animals, do not have the circulatory system. A characteristic of the organisms without the circulatory system is the organisms’ cells are close enough to interact with external environment. (The examples of the external environment are nutrients, respiratory gases and wastes from the cells.)
The aquatic animals have flat bodies to have more contacting areas with the external environment. The aquatic invertebrates have gastrovascular system which allows exchanging their inter stuff with the environment. For example, a sponge contacts with water directly, so the water helps to circulate the sponge through central cavity (gastrovascular system). (Purves, 941)
Components
Vessels
Arteries are the vessels that carry blood away from the heart, veins conduct blood back to the heart. Arteries branch into smaller vessels called arterioles, which then branch further to form capillary beds. Capillaries are the vessels that allow the blood and the tissue fluid to exchange materials.(Purves, 942)
The blood is transported back to the heart from the lungs or the body by the venous system. After materials are exchanged, the capillaries ultimately merge to form venules, which then merge in turn forming the much larger veins. Veins then deliver blood to the heart.
The blood from the upper part of the body returns to the heart through the superior vena cava. In contrast, the inferior vena cava transports the blood from the lower part of the body to the heart. Both vena cavas end at the right atrium, but they enter different places. The superior vena cava enters from the top and the inferior vena cava enters from the bottom.[1]
Heart
- Main Article: Heart
Heart is a muscular organ which pumps blood to the various body systems. It heats constantly and repeatedly. [2]
There are three types of the heart: two-chambered heart, three-chambered heart, and “human heart.” Types of the heart are distinguished by the number of chambers in the heart. (Purves, 942-946)
Heart has right and left sides and both sides have upper chamber (atrium) and lower chamber (ventricle). The atrium collect the blood, and pump it to the lower chamber. Inlet valve and outlet valve prevent the blood from backflow. Heart beating is heard when the valves are closed and opened.
The main function of the heart is pumping the blood. By pumping the blood, wastes (carbon dioxide) from the body can be removed from the lungs and oxygen and nutrients can be delivered to all of the body. First, the right side of the heart pumps the blood to the lungs. And then, the left side of the heart send the blood to every part of the body. Blood from the body passes through the right atrium. Through the right atrium, the blood goes to the right ventricle when it is relaxed. When the right ventricle is full, the right atrium contracts. Contracting the right atrium send the blood into the pulmonary arteries through the pulmonary valve. Oxygen from the lung moves through the pulmonary veins to the left atrium. When the left ventricle contracts, the blood goes to the aorta through the aortic valve. Oxygen is moved by this process to all of the body except to the lungs.[3]
Cardiac Cycle
Cardiac cycle is when two ventricles contract and relax. When the ventricles contract, it is called systole. When the ventricles relax, it is called diastole. The heart makes sound continuously. Sound from the heart is called, “lub-dub”, and it happens during the cardiac cycle. This sound is made by close the heart valves. (Purves, 947)
Atrial systole
Atrial systole is a contraction muscle in the heart from left and right atria. When both atria contract same time, the blood pressure increases and the blood is sent to the ventricles.[4]
Ventricular systole
Ventricular systole is a contraction muscle in the heart from left and right ventricles.[5]
Cardiac diastole
When the ventricles are relaxed, it is called ventricular diastole. The atrial diastole is when the atria are relaxed. Both of them are known as the cardiac diastole. The cardiac diastole is the time that the heart relaxes after the atrial systole and ventricular systole to prepare refilling.[6]
Vascular Pathway
Human Vascular Pathway
The human vascular pathway consists of two circuits, the Pulmonary and the Systemic.
Pulmonary Circuit
The Pulmonary circuit is involved in the exchange of gases in the lungs. Blood flows from the right ventricle of the heart into the pulmonary artery. From here, it branches both left and right directions, making it's way toward the lungs. Once it reaches the lungs, carbon dioxide is released and oxygen is taken in, both in relation to their concentration gradient. In this case, some carbon dioxide remains in the blood and some oxygen remains in the lungs. However, under hyperbolic conditions, such as in a hyperbolic oxygen chamber, the level and pressure of the oxygen is so high that a much larger amount of oxygen is consumed by the blood, forcing a larger quantity of carbon dioxide out of the blood.
The oxygen level inside the blood and the oxygen level inside the lungs will attempt to balance out. When the oxygen level is seriously depleted in an environment, the body will produce more hemoglobin to decrease the oxygen:blood ratio and to provide more carriers for the oxygen molecules. In hyperbolic conditions, the oxygen without hemoglobin quantity will increase, while the hemoglobins will also fill to capacity.
The blood then leaves the lung capillaries and travels down the pulmonary vein and enters the left atrium of the heart.
Systemic Circuit
The systemic circuit is involved in carrying oxygen rich blood to the body tissues and organs. The blood leaves the left ventricle and enters the right ventricle. The AV node of the heart signals ventricular contraction and the blood is moved through the aortic semilunar valve, into the aorta. The aorta is the largest and strongest artery in the body, branching into other arteries which spread throughout the body. The blood then returns through venules and veins to the superior and inferior vena cava before entering the right atrium.
Measurement Techniques
Five measurement techniques are used to examine circulatory system. Five techniques are electrocardiogram, sphygmomanometer, pulse meter, stethoscope, and pulse.
Electrocardiogram (ECG or EKG) is produced by an electrocardiograph. (The electrocardiograph records a heart’s electrical activity and shows a graph of it.) The electrocardiogram gives diagnostic information. For example:
- It detects electrolyte disturbances.
- It shows an ischemic heart disease.
- It detects conduction abnormalities.
- It guesses a therapy of a myocardial infarction. [7]
Sphygmomanometer (or blood pressure meter) measures the blood pressure. Manual sphygmomanometer is used with a stethoscope. Sphygmus means pulse and manometer means pressure meter in Greek. Samuel Siegfried Karl Ritter von Basch and Scipione Riva-Rocci invented it. Cuff wraps upper left arm at same height as the heart. An examiner inflates the cuff and listens to brachial artery with a stethoscope while he is releasing the cuff’s pressure slowly. A systolic blood pressure records the cuff’s pressure when sound begins again. A diastolic blood pressure records the cuff’s pressure when the sound is not heard anymore.[8]
Pulse meter (or heart rate monitor) measures rate of the heart. Robert Treffene invented it. A chest strap transmitter maintains electrodes that monitor the electrical voltages in the heart. (The chest strap should touch with skin.)[9]
Stethoscope is used for listening auscultation (internal sounds in the human body). The examiner uses it to listen to the heart sounds and breathe sounds. Because it allows hearing auscultation, the examiner uses it with the sphygmomanometer to hear blood flow.[10]
Pulse is the simplest measure technique. When the arteries throb by heart beat, the pulses can be felt. A person can feel the pulses from carotid artery (neck), radial artery (wrist), popliteal artery (knee), brachial artery (elbow), and posterior tibial artery (ankle joint). Normal person has 60 to 100 beats per minute (BPM) pulse rate. When he exercises, the pulse rate increases about 200-220 BPM. Pulses help to find artery diseases. Giant cell arthritis is occurred by absence of the pulses at the skull. Peripheral artery occlusive disease is occurred by decreasing the pulses at the limbs.[11]
Related References
- ↑ 1.0 1.1 Circulatory system by Wikipedia
- ↑ Purves, William. Life the Science of Biology. 2005. Couriers Company Inc. p 941.
- ↑ Purves, p 942
- ↑ Purves, p 941
- The Circulatory System Globalclassroom.org
- Circulatory System Wikipedia
- Electrocardiogram Wikipedia
- Heart Merck
- Heart Wikipedia
- Pulse Wikipedia
- Pulse meter Wikipedia
- Sphygmomanometer Wikipedia
- Stethoscope Wikipedia
See Also
| |||||||||||||||||||||||
