Hart en bloedvatstelsels van vertebraten - Zoo Chptr 31: Internal fluids and restpiration

7 important questions on Hart en bloedvatstelsels van vertebraten - Zoo Chptr 31: Internal fluids and restpiration

What changed in the evolution from gills to lungs?

A high-pressure double circulation evolved. A systemic circuit provides oxygenated blood to the body and a pulmonary ciruit serves the lungs. 

What does the modern amphibian heart look like?

There are two atria, the right receives venous blood from the body and the left blood from the lungs and skin. The ventricle is undivided, but venous and arterial blood stay seperated due to the spiral fold of the conus arteriosus.

What does the mamalian heart look like?

The heart is covered by the pericardium. Blood returning from the lungs flows through the pulmonary veins and collect in the left atrium, passes though to the left atrioventricular (AV) valve (/valvula bicuspidalis) to the left ventricle and is pumped to the body through the aorta by passing the aortic semilunar valve. Blood returning from the body flows though the inferior and superior vena cava into the right atrium and passes the right atrioventricular (AV) valve (/valvula tricuspidalis) into the right ventricle which pumps the blood to the lungs via the pulmonary semilunar valve and pulminary arteries.
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What is contraction and relaxation of the heart called?

Systole is contraction and diastole is relaxation. When the atria contract (atrial systole), the ventricles relax (ventricular diastole).  

What do skeletal and cardiac muscle have in common and how are they different?

They are both striated muscle, but cardiac cells are branched and joined end-toend by junctional complexes (intercalated discs) to form a branching network. Cardiac muscle also does not rely on nerve activity to initiate contraction, this is done by pacemaker cells.

What is a myogenic heart?

One that is initiated in specialized muscle cells. (vertebrates, molluscs and several other invertebrates)

How does capillary exchange take place?

In  a capillary, the blood pressure that pushes water molecules and solutes through the capillary endothelial cell clefts is greatest at the arteriolar end of the capillary and declines alson its length as the blood pressure reduces. Opposing blood pressure is osmotic pressure created by the proteins that cannot pass through the capillary endothelial cell clefts. This colloid osmotic pressure drwas water back into the capillary. Excess fluid is collected and removed by lymph capillaries of the lymphatic system and eventually this fluid is called lymph is returned to the circulatory system via larger vessels.

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