Download in pulmonary BP

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‫االسراء اية ‪58‬‬
‫‪Dr abdelaziz Husssein, Mansoura‬‬
‫‪Faculty of Medicine‬‬
By
Dr. Abdel Aziz M. Hussein
Lecturer of Medical Physiology
Member of American Society of Physiology
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
• The pulmonary circulation is concerned with
passage of blood from the Rt ventricle, through
the lungs and then to the lt atrium.
• The pulmonary circulation time is about 7
seconds at rest.
• It receives all the COP from the right ventricle.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
a) Pulmonary arteries:
The lungs are supplied with blood from 2 sources:
i) Pulmonary artery:
•It transmits venous blood from the Rt ventricle to the lungs.
•It branches finally to capillaries around the alveoli→ exchange of
gases ( ) alveolar air and pulmonary blood.
ii)Bronchial arteries:
•They arise from the aorta and supply mainly the bronchi and
bronchioles.
•There are many anastomosis ( ) the bronchial and pulmonary
arteries.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
b) Pulmonary veins:
The blood leaves the lungs by 2 ways;
i) 4 pulmonary veins:
• They transmit oxygenated blood from the lung to the left
atrium.
ii) Bronchial veins:
• They transmit venous blood from the bronchi and bronchioles
to the pulmonary veins, and finally to the left atrium.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
1) Transport of blood from the right side of the heart
to the left side→ low resistance pathway for blood
transport through the lungs.
2) Arterializations of venous blood during its passage
through the lungs→ removal of CO2 and receiving
O2
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Value:
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Value:
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Intrinsic
(autoregulation)
Extrinsic
mechanism
1. Nervous
regulation
Hypoxic V.C.
2. Chemical
regulation
3. Mechanical
regulation
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
◊ Def.
• It is the automatic control of local pulmonary blood
flow distribution.
◊ Mechanism:
• When the alveolar O2 concentration becomes very
low, the adjacent blood vessels slowly constrict within
3 to 10 minutes.
• It is opposite to what happens in systemic vessels
that respond to low PO2 by VD.
• It is believed that hypoxia leads to release of some
VC substances from the lung tissues that promote
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
VC.
VD
VC
↑ PO2
↓ PO2
Significance:
Shift of blood to areas of the lungs that are better
Dr abdelaziz Husssein, Mansoura
aerated or ventilated. Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
• Pulm. BF equals COP, so factors affecting COP,
affect the pulmonary BF.
• ↑ed COP (as in exercise) →↑es the pulmonary BF
with slight ↑ in pulmonary BP.
• COP should be ↑ed 4 times before ↑ pulmonary BP
because:
a)Pulmonary blood vessels dilate passively
b)The outflow of blood from pulmonary veins ↑es due
to ↑ed HR (by Bainbridge reflex)
Significance:
•It ↑es pulmonary gas exchange with COP (in exercise)
without over work of the
heart.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
• Pulmonary circulation can change its capacity to
buffer excess changes in pulmonary BP because the
pulmonary vessels are highly distensible
a) Removal of one lung → all COP of the Rt ventricle is
pumped to one lung →↑ in pulmonary capacity→
prevents much ↑ in pulmonary BP.
b) Haemorrhage → pulmonary vessels constrict → ↓
pulmonary capacity → prevent much drop in pulmonary
BP
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
c) Left side heart failure → stagnation and congestion
of blood in lungs occur→↑ pulmonary capacity →
prevent excessive ↑ in pulmonary BP to certain limit.
• When pulmonary capacity exceeds this limit → ↑
pulmonary BP.
d) Posture (gravity) → capacity is greater in recumbent
position than in sitting or standing due to ↑ed VR caused
by absence of the effect of gravity.
e) Respiration
•During inspiration→ pulmonary capacity ↑ es (due to
VD) and pulmonary BP ↓es.
•During expiration→Dr abdelaziz
the capacity
↓es (due to VC) and
Husssein, Mansoura
Faculty of Medicine
pulmonary BP ↑es.
◊ Value:
• It equals l/6 systemic PR
•An ↑ in pulmonary PR (e.g. in mitral stenosis,
emphysema, fibrosis, and embolism) produces much
↑ in pulmonary PB→ Rt ventricle dilates to ↑ the power
of contraction (Starling's law).
• If the ↑ in pulmonary BP persists → Rt ventricular
hypertrophy and failure.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
•Pulmonary peripheral resistance is ↑ed in:
1.Mitral stenosis due to back pressure in lungs and
reflex VC by hypoxia.  Pulmonary PR and BP.
2.Emphysema: bad ventilation produces generalized
hypoxia and VC of pulmonary blood vessels  
Pulmonary PR and BP.
3.Pulmonary fibrosis and embolism: blocking of
pulmonary blood vessels and reflex VC from hypoxia 
 Pulmonary PR and BP.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
a) Vagal stimulation → VD of pulmonary blood
vessels and ↓es pulmonary BP.
b) Sympathetic stimulation → VC of pulmonary
blood vessels and ↑es pulmonary BP.
However, the nervous effect is weak on pulmonary
BP.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
a) Ach and certain prostaglandins dilate the
pulmonary arterioles.
b) Catecholamines, angiotensin II constrict the
pulmonary arterioles.
c) Serotonin and histamine constrict the pulmonary
venules.
d) Nitric oxide (NO) dilate the pulmonary arterioles →
its deficiency in pulmonary vessels leads to pulmonary
hypertension.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
1) It is distensible low pressure circulation, so the
pressure in it is low (1/6 of ABP)
• Pulmonary PR is 1/6 systemic PR because:
a) Pulmonary artery → is thin, 1/3 thickness of the
aortic wall.
b) Small pulmonary arteries and arterioles → short
with large diameter and with little smooth ms fibers→
accommodate large amount of blood.
c) Pulmonary capillaries→ are wide, have many
anastomoses around alveoli, highly permeable and
have high exchangeable surface area.
d) Pulmonary veins → are short, distensible and act as
blood reservoir.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
2. There is very little fluid formation in the alveoli, but
the lungs are richly supplied by lymphatics to keep the
alveoli dry.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
◊ Def,
•It is a pathological accumulation of fluid in the lung
alveoli or in the pulmonary interstitial spaces.
•It is dangerous (even fatal) because it prevents gas
exchange in the lungs.
Formation and drainage interstitial fluid in lungs
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
Formation and drainage interstitial fluid in lungs
o Thus the net mean filtration pressure = 29-28 = 1
mmHg→ slight continual flow of fluid from the
pulmonary capillaries into the interstitial spaces.
o This fluid is drained to the circulation through the
pulmonary lymphatic system.
◊ Causes:
a) Marked ↑ of pulmonary capillary B.P., as in patients
with left sided heart failure due to lung congestion.
b) ↑ed permeability of pulmonary capillary
membrane caused by infectious diseases or poisons as
some war gases.
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
◊ Pulmonary edema safety factors:
a) Low capillary pulmonary pressure (7 mmHg)
(filtering force).
b) High osmotic pressure of plasma proteins (28
mmHg) (reabsorbing force), so any filtered fluid will be
immediately reabsorbed.
- Safety factor against pulmonary edema is 28 -7 =21
mmHg
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine
THANKS
Dr abdelaziz Husssein, Mansoura
Faculty of Medicine