Lecture 27: Blood vessels and blood pressure

Question 1

Describe the five types of blood vessels and their main anatomical features

Answer 1

Arteries: carry blood from heart to tissues in large quantities and eventually branch into arterioles

Arterioles: vessels coated with smooth muscle can exert huge changes in resistance to flow. sites of large energy loses in the arterial tree

Capillaries: arise from arterioles and are the major site of nutrient and cellular waste exchange

Venules: drain capillary beds then rejoin to form small veins

Veins: collect blood from the venules to return it to the heart. Veins are highly distensible, so they also serve as a blood reservoir

Question 2

Describe the relationship between blood flow rate, pressure and resistance, including the role of vessel radius

Answer 2

The difference in pressure gradient from the beginning and the end is crucial to determine flow rate not the pressure within the vessel.

If resistance doubles and deltaP remains the same, flow rate will be reduced by half

In a narrower vessel its harder for blood to flow through therefore causing more firction and more resistance since it has more surface area.

In a wider vessels it has less friction and less resistance

Resistance is inversely related to the fourth power of the vessel radius, so if the radius doubles there is a 16 fold decrease in resistance (r/16)

Question 3

Define systolic, diastolic and mean arterial pressure, and describe how they are measured

Answer 3

Systolic pressure : peak arterial pressure during cardiac contraction. Measured when you hear the first sound with a stethoscope between 120 and 80mmHg.

Diastolic pressure : lowest arterial pressure during cardiac relaxation. Measured when you hear no sound with a stethoscope under the 80 mmHg pressure.

Mean arterial pressure(MAP) : the average pressure driving the blood forward into the tissues. Measured with the formula of:
MAP=((S-D)/3)+D or MAP=pp/3+D
(pp= pulse pressure)

Question 4

Define Hypertension

Answer 4

its when you have high blood pressure or high systolic over high diastolic

BP is > =140/90 when measured at the doctors office

BP is > =130/80 if the patient is diabetic

BP is > =135/85 if measured at home