Concept about Blood pressure | CHAPTER 5 | Anatomy and Physiology

Concept about Blood pressure-The course is designed for the basic understanding of anatomical structures and physiological functions of human body, musculoskeletal system, digestive system, respiratory system; cardiovascular system; urinary system, endocrine system, reproductive system, nervous system, hematologic system, sensory organs, integumentary system, and immune system.The aim of the course is to acquire knowledge and skills regarding anatomy and physiology.

Concept about Blood pressure

Definition:

It is the lateral pressure exerted by blood on the vessel wall by its contained blood while flowing through it

Or,

Blood pressure means the force exerted by the blood against a unit area of blood vessel.

Ref: Guyton and Hall 12th 162p.

Blood pressure Cardiac output X Total peripheral resistance

Types of blood pressure:-

1. Systolic pressure: Normally. About 110-140 mmHg.
2. Diastolic pressure: Normally. About 60-90 mmHg.
3.  Pulse pressure: Normally: About 30-40 mmHg.
4. Mean pressure: Normally About 78-98 mmHg

Functional Importance of blood pressure:

Knowing about the cardiovascular status

1. BP maintains a state to keep the blood flowing
2. It provides the force of filtration at the capillary bed and thus helps in tissue perfusion (O CO, nutrients), formation of urine, lymph etc

Diastolic pressure:

• It is the lowest pressure observed in the aorta during diastole. Or,
• It is the lowest arterial pressure during a cardiac cycle. It is measured when the heart is relaxed (diastole) and blood is returning to the heart via the veins.
• Normal diastolic pressure is about 60-90 mm Hg.

Significance:

1. It is the measure of peripheral resistance.
2. It is the level at which the heart is pumping. If the diastolic pressure is raised, heart is doing more work.

Systolic pressure:

It is the maximum arterial pressure during systole. Or,

It is the highest arterial pressure during a cardiac cycle. Systolic pressure is measured after the heart contracts and blood is ejected into the arterial system. Normal systolic pressure is about 110 to 140 mm Hg.

Significance:

The height of systolic pressure indicates-

1. The force of contraction of the heart.
2. The extent of work has done by the heart.
3. The degrees of pressure, which the arterial walls, have to withstand.

Pulse pressure:

It is the difference between systolic pressure and diastolic pressure.

Systolic pressure – Diastolic pressure = Pulse pressure

The most determinant of pulse pressure is stroke volume. As blood is ejected from the left ventricle into the arterial system, arterial pressure increases because of the relatively low capacitance of the arteries Because diastolic pressure remains unchanged during ventricular systole, the pulse pressure increases to the same extent as systolic pressure

Normal pulse pressure is about 30 to 40 mm Hg.

Significance:

1. It is the index of cardiac output eg fedCardiac outputed Pulse pressure
2. When the capacitance (distensibility of blood vessels) of arteries decreases (in aging process), pulse pressure increases

Pressure:

Definition:

It is the average pressure throughout the cardiac cycle. Mean pressure (MP) equals the diastolic pressure plus one third (1/3rd) of the pulse pressure.

MP Diastolic pressure + 1/3rd of pulse pressure. Normal mean pressure is 78-98 mm Hg.

Significance:

1. It is important in the study of hypertension. e.g.: fed Mean pressure fed chance of hypertension.
2. It is an index of paradoxal pulse.

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