Human blood pressure is the total pressure of all arteries in the body. In different arteries, the pressure is different. It is the higher, the wider the diameter and closer to the heart. The highest pressure in the aorta is the great vessel extending from the left ventricle.
Human blood pressure consists of two numbers: "upper and lower." “Upper” pressure is the so-called heart pressure. It is due to the work of the heart, the force with which the heart pushes blood into the aorta. “Lower” reflects the tone of the vessels of the body, which is affected by the kidneys. The juxtaglomerular apparatus is located in the kidney parenchyma , which, when the pressure is reduced, ensures the start-up of the angiotensin-aldosterone system, which leads to an increase in the reuptake of water in the kidneys and, accordingly, an increase in the volume of circulating blood and an increase in pressure.
A person’s blood pressure can fluctuate widely: upper - from 90 to 139, and lower - from 60 to 89. There is a concept of working pressure. This is usually the pressure that is normal for this particular patient.
A person’s blood pressure can depend on many environmental factors: for example, in hot weather it decreases due to reflex expansion of blood vessels (to give off heat) and with loss of fluid with sweat. With increased heart rate, which occurs, for example, due to increased physical activity or fright, blood pressure may increase. With a sharp change in body position from horizontal to vertical, an orthostatic effect may appear, which is manifested by darkening in the eyes and goosebumps. Its occurrence is due to the fact that the vessels and heart could not quickly respond to a change in the position of the body in space, and the pressure was low.
The blood pressure of a person is regulated by the nervous system, as well as hormones. Throughout the day, pressure can significantly change its performance. In a dream, it decreases, during the day (especially with stress) it rises.
It should be noted that different hands may have different blood pressure. But if the difference is less than 5 mm RT. Art., then it does not have clinical significance. Identification of differences of 10 or more mm RT. Art. indicates a narrowing of the artery on the arm with less pressure.
Pressure in different age categories may vary slightly. For example, blood pressure in adolescents may be elevated. If its increase is not due to pathology, then hypertension is transient and moderate. This is due to the fact that children are usually hyperactive (i.e., they are characterized by increased activity), as well as neuro-endocrine regulation during the transitional period.
Under various physiological conditions, changes in pressure are possible. For example, blood pressure during pregnancy can increase, which can be a symptom of a severe pathology - preeclampsia. Therefore, blood pressure in pregnant women should be constantly monitored. If blood pressure is found to be higher than normal two times or more within one week, the development of preeclampsia should be suspected.
Throughout pregnancy, normal pressure changes. Pregnancy hormone, progesterone, causes relaxation of the walls of blood vessels, which leads to a decrease in pressure and increased orthostatic effect. The largest amount of progesterone is produced in mid-pregnancy - hypotension at this time is possible. By the sixth month of pregnancy, the woman’s body contains about 2.5 liters more blood - this is an additional burden on her body. In the last days of pregnancy, blood pressure restores its normal value.