NATS 1675 Lecture Notes - Lecture 19: Robert Crippen, Skeletal Muscle, Pulmonary Circulation

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24 Mar 2016
NATS 1675 LECTURE #19 The Circulatory System
Professor: Robert Crippen
Refer to textbook: Figure 5.1 Circulatory System
This is a complete system : we have a heart [which acts like a pump it is actually 2
pumps with 4 chambers]
Blood is pumped out through the heart
It interconnects with ten other organs
It is composed of cardiac muscle only found in the heart and in the aorta
All three muscle types are found in the circulatory system the only system that can
have 3 muscles
The Heart consists...
Right side = pulmonary circulation to the lungs
Left side = systemic circulation to the body
Upper chambers = atria (plural) [atrium = singular] this is a receiving chamber so the
atria receives blood from some place in the body
Lower chambers = ventricles this is a pumping chamber so it pumps blood to some
place in the body: the two ventricles are separated by a muscular wall called the septum.
The pressure produced by the left ventricle is 5x that of the right.
Blood Vessels [STRUCTURE] Arteries
It has 3 layers
1) Inner : a tube of endothelium [a continuation of the capillaries] that is surrounded by
connective tissue including elastic fibrous tissue
2) Middle : the thickest layer, smooth muscle and elastic connective tissue
3) Outer : primarily fibrous connective tissue [with some smooth muscle cells and elastic
There are also arterioles [aka. little arteries] and they are small branches of the arteries that
connect the larger arteries to capillaries
It connect arterioles to venules; walls are one cell thick; all exchanges occurs here. They are
microscopic endothelial tubes with walls 1 cell thick with a total surface area of about 6300m2.
They are a continuation of the endothelial lining of the arteries and arterioles. The endothelial
cells are loosely joined permitting the passage of substance between cells ex. WBC’s. Because
of the narrow diameter, RBC’s are restricted to passing in single fill. Capillaries branch
extensively nearly every cell in the body has a capillary passing near to it
They contain less smooth muscle and connective tissue, especially elastic fibres. The veins also
contain one way valves. There are also venules [aka. little veins] and they are small
branches of the veins that connect capillaries to the larger veins. Blood pressure in the veins is
about 5.
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