The two blood pressure numbers obtained when a BP reading is taken, represent important life-sustaining events. Although minute in time they are enormous in their effects. The top number of a reading is the systolic blood pressure. The bottom number is the diastolic pressure. In order to appreciate these numbers and the two crucial events they represent it is necessary to have a basic understanding of the cardiovascular system. The construction of a natural model can be helpful in acquiring this understanding.
The cardiovascular system is a closed circuit within the body through which blood flows. It consists of the heart, blood vessels and nerve endings which regulate the actions of the heart and vessels. The left side of the heart pumps oxygen-rich and nutrient-rich blood to all the vital body tissues through arteries. The arteries deliver oxygen nutrients to those tissues. They also remove waste products such as carbon dioxide from those tissues via an exchange process in the smallest microscopic subdivided branches of the arteries, known as capillaries. The ends of those capillaries then join end-to-end with equally small vessels that merge in an identically opposite manner as the preceding branching ones to form progressively larger vessels known as veins. The veins empty into the right side of the heart, as the blood flow throughout the circuit is from left to right in a counterclockwise direction. The blood is then pumped from the right side of the heart into the lungs where it is replenished with oxygen and cleansed of carbon dioxide. It then flows from the lungs into the left side of the heart for a repeat cycle of delivery to bodily tissues.
The cardiovascular system can be likened to Siamese rivers with parallel mainstreams travelling in opposite directions. One stream flows outward. The other flows inward. At various points along the outflowing stream branching tributaries also flow outward and eventually merge with other tributaries which feed into the inflowing river stream. A lake is the source of water for the outflowing river stream. The lake has a natural filter dividing it into two separate bodies of water. The water in the inbound river empties into the right side of the lake and passes through the filter before then flowing into the left side of the lake for recycling. The lake symbolizes the heart. The filter which separates the lake symbolizes the lungs. The smallest subdivisions of the outflowing tributaries represent the capillaries which supply oxygen-rich and nutrient rich blood to the cells. The communities through which the tributaries flow represent tissues. The people that live in the communities are the cells of the body.
Blood pressure numbers obtained when a reading is taken represent two events. The top number is the systolic blood pressure. It represents the force exerted when the heart contracts and pumps blood into the arteries. The bottom number is the diastolic pressure. It is the passive force exerted by the blood against the walls of the arteries when the heart is relaxed and filling with blood. According to the laws of physics, force = mass x acceleration. Mass is the volume of blood in the arteries. Acceleration is the change in the speed of blood flow through the arteries. Therefore, it is not surprising that the systolic blood pressure number is higher than the diastolic number because the amount of blood in the arteries is greater and the speed of the blood flow through the arteries is increasing when the heart contracts.
A heartbeat is a contraction followed by a relaxation. The number of heartbeats in a normal healthy state ranges from between 60 to 90 per minute. Therefore, each one of these life-sustaining events lasts for only between 1 to 1½ seconds. If that is not a marvel in and of itself it is even more amazing is that without these consecutive mini-events life ceases to exist within just a few minutes of their absence. The top and bottom numbers of a blood pressure reading therefore, don’t only represent cardiovascular events. They also represent life. They are life.