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Complex p – atrial.

Complex QRST – ventricular.

As heart excitation begins from its base, than this region is a negative pole, apex region – positive one. Heart electromoving force (EMF) has its size and direction. EMF direction is considered to call heart electrical axis. In the most common cases it is located in parallel to heart anatomical axis (normogram). Direction of one or another dens on ECG reflects an integral vector direction. When vector is directed to heart apex, one can registrate positive (as for electrical axis) denses, if to the heart base - negative. Due to definite heart location in thorax and human body shape, electrical force lines occuring between excited and unexcited heart locus, are distributed unequally on body surface. If heart axis becomes horizontal (lying heart) than such situation is called left-gram, in a case of its vertical localization (hanging heart) – right-gram.

Lecture 12.

Vessels physiology. Blood pressure. Pulse. Capillary and venous circulation. Lymphatic supply. Functional vessels classification:

  1. Elastic:

  • aorta;

  • pulmonary artery;

  • other large vessels.

  1. Muscular:

  • middle arteries;

  • shallow arteries.

  1. Resistive (vessels of resistance):

  • ending arteries;

  • arterioles.

  1. Of exchange (exchangeable):

  • capillaries.

  1. Cavitary:

  • veins;

  • venules.

Blood movements through the vessels obey to some regularities known as hydrodynamics laws. But they are named as haemodynamics laws according to blood vessels.

Factors determining haemodynamics peculiarities (3 first are the main, rest are additional ones):

  • pressure;

  • resistance;

  • velocity;

  • vessel diameter and length;

  • blood content;

  • blood viscosity et al.

Circulation peculiarities:

  • one-sided blood traffic through vessels;

  • its continuosity;

  • laminarity;

  • turbulent character.

One-sided movement - is provided by pressure gradient (difference) at the beginning and at the end of vascular system. It is 120-150 mm merc col. in initial circulation part and 5-0 mm merc col - in ending part (veins inflowing into heart).

Circulation continuosity – is linked with vessels elasticity, when blood is pumped in aorta by heart (it possesses elasticity) then all its volume can not come through the vessels at once. More blood part is remained temporarily in dilated (due to elasticity) aorta region and then (in course of dyastole) leaves it due to aorta walls muscular contraction. The more elastic is aorta and other large arteries, the better circulation continuosity is realized. And on the contrary, at elasticity loss (with ageing, at sclerosis and other vessels injuries) circulation continuosity is disturbed.

Laminar or streamline and turbulent character of blood circulation movement character through vessels. Laminar circulation - is blood movement by separate layers in parallel to vessel axis (it is realized practically in all vessels). Turbulent circulation – with blood turbulence – occurs in the places of dilations, constrictions, flexures and pressures on them.