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By the end of this section, you will be able to:
  • Distinguish between systolic pressure, diastolic pressure, pulse pressure, and mean arterial pressure
  • Describe the clinical measurement of pulse and blood pressure
  • Identify and discuss five variables affecting arterial blood flow and blood pressure
  • Discuss several factors affecting blood flow in the venous system

Blood flow refers to the movement of blood through a vessel, tissue, or organ, and is usually expressed in terms of volume of blood per unit of time. It is initiated by the contraction of the ventricles of the heart. Ventricular contraction ejects blood into the major arteries, resulting in flow from regions of higher pressure to regions of lower pressure, as blood encounters smaller arteries and arterioles, then capillaries, then the venules and veins of the venous system. This section discusses a number of critical variables that contribute to blood flow throughout the body. It also discusses the factors that impede or slow blood flow, a phenomenon known as resistance    .

As noted earlier, hydrostatic pressure is the force exerted by a fluid due to gravitational pull, usually against the wall of the container in which it is located. One form of hydrostatic pressure is blood pressure    , the force exerted by blood upon the walls of the blood vessels or the chambers of the heart. Blood pressure may be measured in capillaries and veins, as well as the vessels of the pulmonary circulation; however, the term blood pressure without any specific descriptors typically refers to systemic arterial blood pressure—that is, the pressure of blood flowing in the arteries of the systemic circulation. In clinical practice, this pressure is measured in mm Hg and is usually obtained using the brachial artery of the arm.

Components of arterial blood pressure

Arterial blood pressure in the larger vessels consists of several distinct components ( [link] ): systolic and diastolic pressures, pulse pressure, and mean arterial pressure.

Systolic and diastolic pressures

When systemic arterial blood pressure is measured, it is recorded as a ratio of two numbers (e.g., 120/80 is a normal adult blood pressure), expressed as systolic pressure over diastolic pressure. The systolic pressure    is the higher value (typically around 120 mm Hg) and reflects the arterial pressure resulting from the ejection of blood during ventricular contraction, or systole. The diastolic pressure    is the lower value (usually about 80 mm Hg) and represents the arterial pressure of blood during ventricular relaxation, or diastole.

Systemic blood pressure

This graph shows the value of pulse pressure in different types of blood vessels.
The graph shows the components of blood pressure throughout the blood vessels, including systolic, diastolic, mean arterial, and pulse pressures.

Pulse pressure

As shown in [link] , the difference between the systolic pressure and the diastolic pressure is the pulse pressure    . For example, an individual with a systolic pressure of 120 mm Hg and a diastolic pressure of 80 mm Hg would have a pulse pressure of 40 mmHg.

Generally, a pulse pressure should be at least 25 percent of the systolic pressure. A pulse pressure below this level is described as low or narrow. This may occur, for example, in patients with a low stroke volume, which may be seen in congestive heart failure, stenosis of the aortic valve, or significant blood loss following trauma. In contrast, a high or wide pulse pressure is common in healthy people following strenuous exercise, when their resting pulse pressure of 30–40 mm Hg may increase temporarily to 100 mm Hg as stroke volume increases. A persistently high pulse pressure at or above 100 mm Hg may indicate excessive resistance in the arteries and can be caused by a variety of disorders. Chronic high resting pulse pressures can degrade the heart, brain, and kidneys, and warrant medical treatment.

Questions & Answers

name the 5 layers of skin
Monika Reply
stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum
airiz
those are the layers of epidermis,, then we have the dermis which has got two layers that is papillary dermis and reticular dermis.. beneath the dermis we have the hypodermis( subcutaneous layer) which is not considered as a layer of skin
airiz
what's a feedback
ivhil Reply
is the information or comment about something that one have done
Gaston
may be you mean negative or positive feedback mechanism... in general, they mean body response its changes by hormones
Quran
what is endocrin?
Asim Reply
why should there be an inhibition to the process of gastric production in the intestinal phase
Gloria
endocrine is a system through which the secretions of cell directly poured into blood.
Tanveer
why should there be an inhibition to the process of gastric production in the intestinal
Gloria Reply
what is a stimuli
Emily Reply
environment factor that cause a cell to respond
Quran
name the two types of melanin
Laila Reply
deference between RNA and DNA
Ali
.DNA stands for Deoxyribonucleic Acid. The sugar portion of DNA is 2-Deoxyribose.RNA stands for Ribonucleic Acid.  The sugar portion of RNA is Ribose.2.The helix geometry of DNA is of B-Form (A or Z also present).The helix geometry of RNA is of A-Form.3.DNA is a double-stranded molecule consisting o
ryaisha
DNA consists of nucleotide but RNA consists of nucleoside DNA is double standard but RNA is single standard.In DNA at the nitrogen bases adinine,guanine,cytocin and thymine is present but in case of RNA instead of thymine uracil is present.
Tanveer
what are rdna
Budumari
what is a heart
walker Reply
A heart is an organ in the circulatory system that pumps blood throughout the systemic regions
bernard
what is anatomy
Aisha
Anatomy is the study of internal and external structures and the relationship among body parts. (the study of structure).
Tomi
what is the physiology of the heart
nadine
guys help me with a pathophysiology of asthma
Luyando
asthma is a lungs related disorder in which there is difficulty in breathing due to some allergic factors, their is inflamation of alveoli of respiratory part of lungs.also decreases the surface area.
Tanveer
what is meaning of brain strock and its types?
Tanveer
the pathophysiology of asthma is complex and involves airway inflammation and bronchial hyperresponsiveness pathogenesis of asthma
Omkar
skin infection please explain
Hamza Reply
what is malignant melanoma
Akon Reply
cancerous cells 🙄
Sohan
yes benign is non-cancerous malignant is cancerous.
Joseph
that's a simple way of explaining it however you're different processes like mitosis etc a person can be at risk for developing cancer etc
Joseph
you can tell by an unusual growth of a mole, or change in size coloration with melanoma. which is abnormal growth of your squamous cells.
Joseph
Types of wandering connective tissues
Hassan Reply
what are the meaning of skin
PASHALINA Reply
study of external structure of human body is known as anatomy
VINAY Reply
what is Tau?
Vicki Reply
what is sliva
Saqlain Reply
what is gross
Kiran Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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