Download Pulmonary circulation

Pulmonary circulation
 High pressure low flow circulation: Bronchial vessels. Empties
into pulmonary veins and enter left heart.
 Left atrium input, and left ventricle output are about 1-2%
grater than that of right ventricular output.
 Low pressure high flow circulation: Rt. Ventricle-Pulmonary
artery  arterial branches alv. capill.  Veins  Lt. atrium
 Lymphatics: From supportive tissue spaces coursing to
hilium of lungs and into right thoracic lymph. Duct.
Helping to prevent pulmonary edema
Pulmonary circulation
 Physiological anatomy:
the Artery is 5cm thin (1/3 of aorta diameter) , while the
branches are short and have more diameter so it will have a
large compliance (7 ml/mmHg).
pulmonary veins are thin & short.
bronchial arteries originate from the systemic circulation
(carry 1-2% of C.O -oxygenated blood-) then empty into
pulmonary veins then to the left atrium so the left ventricle
pumps 1-2% more than the right ventricle.
rich lymphatic drainage to the right thoracic duct to
prevent edema
 Pressures in the pulmonary system:
1- right ventricle: 25-1 mmHg
2- pulm. Artery: 25-8 mmHg
3- pulm. cap. : 8 mmHg
4- left atrium & major veins: 2 mmHg
 Blood volume of the lungs: :
 450 ml ( 9% of total blood volume)
 70 ml are found in the capillaries
Blood volume of the lungs
if the person is bleeding or blowing
air out hardly the volume can reach 200
ml.
if blow out air hard
if the person has left heart failure or
mitral valve stenosis or regurgitation
the volume can reach 900 ml
Blood
flow
 Effect of alveolar [O2]:
 when [O2] decreases below 70% of normal  alveolar
epithelial cells secrete vasoconstrictors  adjacent blood
vessels constrict  blood flows to better aerated alveoli
(extreme low [O2]  5x resistance)
 Effect of hydrostatic pressure:
 in normal upright adult there’s a difference between
the lowest and highest points of the lung
the gradient is 23 mmHg (15 mmHg above the heart & 8
mmHg below it)
 Regional pulmonary blood flow :
1-Zone 1: No blood flow
(capill. pr. < alveol, pr.)
- Pts. Breathing against positive pr.
- Sever blood loss.
2-Zone 2: Intermittent blood flow
3-Zone 3: Continuous blood flow.
(capill. pr. > alveol. pr.)
 in normal lungs zone 1 cannot be found, zone 2 is in the
apex of the lung and zone 3 represents the base.
 Regional pulmonary blood flow :
 arterial pressure in pulmonary artery is 25-8 mmHg
at apex systolic 25-15= 10 mmHg
during diastole 8-15 mmHg= -7?
 if the person is lying down or exercising only zone 3
can be seen.
 The effect of increasing C.O on pulmonary blood flow
during exercise:
blood flow increases by 4-7 folds through:
1- increasing the # of open capillaries
2- distending all the capillaries to increase the flow rate
in each one of them.
3- increasing pulm. Arterial pressure
normally 1 & 2 are enough to cause significant decrease
in resistance
 3 is not significant to conserve the energy of the right
heart & to prevent edema
 Pulmonary capillary dynamics:
 7 mmHg cap. Pressure.
 blood passes through the capillary in 0.8sec
 increasing the C.O lowers the time to 0.3sec
 Capillary fluid exchange dynamics:
lungs
Systemic cir.
Capillary pressure
7 mmHg
17 mmHg
Interst. Osm. Pr.
14 mmHg
8 mmHg
Interst. Neg. pr.
-8 mmHg
-3 mmHg
 outward forces= 7+14+8 = 29 mmHg
 inward forces = 28 mmHg
 mean filtration pr. = 1 mmHg “handled by lymph”
Pulmonary edema
 Alveoli are always dry except for a small amount of fluid
secreted by alveolar cells on the alveolar surface.
 When interstitial pressure becomes (+) water will fill the alveoli
 Causes:
1- Left-sided heart failure ↑ venous+cap. pr
2-Damage to the pulmonary capillary membrane caused by :
a- infections
b- breathing chlorine gas or sulfur oxide gas.
 Safety factors 21 mmHg in acute states
35 mmHg in chronic cases