Transcript The Cardiac Cycle

Perfusion
David Taylor
[email protected]
http://www.liv.ac.uk/~dcmt
Learning Outcomes
 By the end of this lecture you should be able to
describe





The physiological components of the circulatory system
The physiology of tissue perfusion
Oxygen and nutrient delivery
Removal of waste products
General homeostasis of pH and ions
Physiological components of the
cardiovascular system
 The heart, of course, is the pump
 Three things are essential to remember.
 Pressure from the right of the heart to the lungs is low
 Pressure from the left side of the heart is high, but
reduces as the blood is distributed through the body.
 The same amount of blood leaves the right side of the
heart as leaves the left….
Chapter 17, p 189 in Preston and Wilson (2013)
Chapter 11, p 500 in Naish and Court (2014)
Velocity and cross sectional area
50
5,000
Cross sectional
area cm2
Velocity
cm/s
0
0
Chapter 19, p 215 in Preston and Wilson (2013)
Systemic Pressures
120
Systolic pressure
80
40
Diastolic pressure
0
0
Chapter 19, p 215 in Preston and Wilson (2013)
Fluids
 In a male 60% of body weight is due to fluid, in a
female 55%
 2/3 of the fluid is inside cells – intracellular fluid (ICF)
 1/3 is extracellular (ECF)
 Of the ECF 80% is interstitial fluid
 And 20% is plasma
 Osmotic pressure and hydrostatic pressure determine
the flow between interstitial fluid and plasma
Chapter 3, p 30 in Preston and Wilson (2013)
Chapter 2, p 20 in Naish and Court (2014)
Perfusion pressure
arteriole
capillary
Osmotic pressure
inside capillary
25mmHg
35mmHg
15mmHg
venule
Chapter 19, p 227 in Preston and Wilson (2013)
For O2 and nutrients
arteriole
capillary
high
low
low
venule
Chapter 19, p 227 in Preston and Wilson (2013)
For CO2 and waste products
arteriole
capillary
low
higher
high
lower
venule
Chapter 19, p 227 in Preston and Wilson (2013)
General Homeostasis
 This topic will unroll as you cover more of the body
systems.
 Concentration gradients (as mentioned above are of
crucial importance), and blood flow and tissue
perfusion are needed to ensure them.
 But remember that the circulatory system is also a
crucial buffer system and if it, or part of it stops
working there are local as well as central effects.
Buffers
 There are others, but the most important system is
HCO3- + H+
H2CO3
CO2 + H2O
Chapter 3, p 35 in Preston and Wilson (2013)
Chapter 1, p 11 in Naish and Court (2014)