Circulatory System

Function and Structure of the Circulatory System Transport of gases, nutrients, wastes, and hormones. Highway system for leukocytes Helps maintain homeostasis by transporting warm blood to extremities Helps stabilize pH and ionic concentrations of body fluids

Blood vessels The three types of blood vessels are arteries, veins, and capillaries. Blood vessels consist of a layered wall surrounding a central blood- filled space, called the lumen.

Arteries carry blood away from heart. Arteries have a thick, elastic muscle layer to absorb peaks in pressure

The smallest blood vessels are capillaries. The diameter is so small that red blood cells travel single file. Not all of the capillary beds are open at one time

Blood pressure is highest in the arteries but is considerably reduced as it flows through the capillaries. It is lowest in the veins. The exchange of substances between blood and the body cells occurs in the capillaries. Although fluid leaves and returns to the capillaries, blood cells and large proteins remain in the capillaries.

The diameter of veins is greater than that of arteries. The blood pressure in the veins is low so valves in veins help prevent backflow. The contraction of skeletal muscle during normal body movements squeezes the veins and assists with moving blood back to the heart. Veins act as blood reservoirs because they contain 50% to 60% of the blood volume.

Flow of blood within the heart Blood leaves the body tissues via various veins and enters the right atrium of the heart via the vena cava. Through the tricuspid valve to the right ventricle where it is pumped through a semi lunar valve into the pulmonary artery where it is passed to the lungs to be oxygenated.Blood enters the left atrium via the Pulmonary vein from the lungs. Flows through the mitral valve to the left ventricle. Pumped out of the left ventricle through a semi lunar valve into the aorta. Branches through series of arteries to all parts of the body. Then the whole process starts again!!!

Composition of Blood

A cell that contains hemoglobin and can carry oxygen to the body. Also called a red blood cell (RBC). hemoglobin The reddish color is due to the hemoglobin. concave in shape, which increases the cell's surface area

Open versus Closed Circulatory System In an open circulatory system, blood is pumped from the heart through blood vessels but then it leaves the blood vesselsopen circulatory system Blood flows slowly in an open circulatory system. The animal must move its muscles to move the blood within the spaces. ArthropodsArthropods and most mollusks (except cephalopods: nautilus, squid, octopus) have an open circulatory systemmolluskscephalopods In a closed circulatory system, blood is not free in a cavity; it is contained within blood vessels. Valves prevent the backflow of blood within the blood vessels.closed circulatory system This type of circulatory system is found in vertebrates and several invertebrates including annelids, squids and octopuses.annelidssquids and octopuses

Fish have closed circulatory systems

Amphibians have a three chambered heart: two atria and a single ventricle. Deoxygenated blood and oxygenated blood mix; maximum efficiency is not needed to supply the body ’ s needs.

Lizards have a muscular septum which partially divides the ventricle. When the ventricle contracts, the opening in the septum closes and the ventricle is momentarily divided into two separate chambers. This prevents mixing of the two bloods.

Four Chambers: Birds, Crocodiles, and Mammals The septum is complete in the hearts of birds, crocodiles, and mammals providing two separate circulatory systems:

Raynaud ’ s phenomenon is a condition in which cold temperatures or strong emotions cause blood vessel spasms that block blood flow to the fingers, toes, ears, and nose. Raynaud's phenomenon also occurs without another disease, medication, or cause. This is called primary Raynaud's phenomenon. It most often begins in people younger than age 30. Strong emotions or exposure to the cold causes the fingers, toes, ears, or nose to become white, then turn blue. When blood flow returns, the area becomes red and then later returns to normal color. The attacks may last from minutes to hours. People with primary Raynaud's phenomenon (no other cause or condition) have problems in the same fingers on both sides, but they do not have very much pain. About 5% of the U.S. population has Raynaud ’ s.

Aortic Aneurysm A weakened and bulging area in the aorta, the major blood vessel that feeds blood to the body. Because the aorta is the body's main supplier of blood, a ruptured thoracic aortic aneurysm can cause life-threatening bleeding. Depending on the size and rate at which the thoracic aortic aneurysm is growing, treatment may vary from watchful waiting to emergency surgery. Once a thoracic aortic aneurysm is found, doctors will closely monitor it so that surgery can be planned if it's necessary. Emergency surgery for a ruptured thoracic aortic aneurysm can be risky.

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