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Cardiovascular System. Week 11 Dr. Walid Daoud A. Professor. Arterial Blood Pressure ____________________________________________________________________________________________________________________________________________. Factors which determine ABP & Pulse P.: F = ∆ P

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Cardiovascular system

Cardiovascular System

Week 11

Dr. Walid Daoud

A. Professor

Arterial Blood Pressure____________________________________________________________________________________________________________________________________________

Factors which determine ABP & Pulse P.:

F = ∆ P


CO = ABP – Rt. Atrial P (zero)





= SV x HR x TPR

Arterial Blood Pressure____________________________________________________________________________________________________________________________________________

Factors which determine ABP & Pulse P.:

1-Stroke volume:

SV ↑ SP more than DP → ↑ pulse P.

2-Heart rate:

↑ HR ↑ DP due to shortening of diastole.

3-Total peripheral resistance: ↑ TPR ↑ DP.

4-Elasticity of aorta and arteries:


↑ SP and ↓ DP → ↑ Pulse pressure.

SP is determined by SV mainly.

DP is determined by TPR mainly.

Regulation of ABP____________________________________________________________________________________________________________________________________________

ABP is regulated by 3 mechanisms:

1-Nervous mechanisms (Rapid).

2-Capillary fluid shift mechanism (Intermediate)

3-Hormonal and renal mechanisms (Slow).

Nervous Mechanism______________________________________________________________________________________________________________________________

Cardiovascular centers in medulla:

1-Pressor area: CAC and VCC.

2-Depressor area: CIC and VDC.

Activity of centers is modified by afferents from:

1-Receptors inside cardiovascular system.

2-Receptors outside cardiovascular system.

3-High centers and blood gases changes:

.Mild ↓ O2, ↑ CO2 → ↑ ABP.

.Severe ↓ O2, ↑ CO2 → ↓ ABP and death.

Cardiovascular centers______________________________________________________________________________________________________________________________

Cardiovascular centers______________________________________________________________________________________________________________________________

Capillary fluid shift mechanism____________________________________________________________________________________________________________________________________________

↑ blood volume ↑ ABP ↑ capillary hydrostatic pressure ↑ filtration from plasma to tissue fluid ↓ plasma volume ↓ VR ↓ ABP.

↓ ABP ↓ capillary hydrostatic pressure ↓ filtration at arteriolar end of capillaries

↑ reabsorption at venular end ↓ plasma volume ↑ VR ↑ ABP.

i.e, tissue fluid acts as a reservoir of plasma.

Hormonal Regulation of ABP____________________________________________________________________________________________________________________________________________

Kidney regulates ABP by regulating plasma volume and extracellular fluid volume.

When ABP drops:

1-Renin-angiotensin system.

2-Atrial mechanoreceptors.

Arterial Pulse___________________________________________________________________________________________________________________________________________

It is a propagated wave that travels along the wall of arteries as blood is forced into aotra.

Clinical significance of palpation of radial pulse:



3-Pulse deficit.

4-Force of ventricular contraction.

5-Force equality on both sides.

6-State of arterial wall.

Capillary Circulation____________________________________________________________________________________________________________________________________________

Equilibrium with interstitial fluid and exchange of materials across capillary wall occur by

2 mechanisms:

1- Diffusion.

2- Filtration.


It is passive occurs on both directions and concerned with H2O & dissolved substance.

Factors affecting diffusion rate:

.Factors in substance:

1-Concentration gradient.


3-Molecular weight.

Factors in capillary permeability:

1-Liver capillaries.

2-Muscle, skin, heart and lung capillaies.

3-Kidney and intestine capillaries.


It is a passive flow across capillaries in one direction. It is the bulk transport of H2O, electrolytes and crystalloids.

Factors affecting filtration:

1-Forces tending to move fluid outwards:

. Hydrostatic capillary pressure.

. Interstitial fluid colloidal OP

2-Forces tending to move fluid inwards:

. Colloidal OP of plasma proteins.

. Hydrostatic pressure of interstitial fluid.

Variation in the bulk flow____________________________________________________________________________________________________________________________________________

1- Decrease colloidal OP of plasma proteins:

Liver and kidney diseases ↑ filtration.

2-Increase capillary blood pressure as in

venous obstruction ↑ filtration.

3-Increase capillary permeability as in activity, inflammation, albumin goes out ↑ filtration.

4-Decrease hydrostatic pressure of tissue fluid

↓ filtration.


Excessive infiltration of plasma fluid into tissue fluid leading to accumulation of tissue fluid.

Edema may be generalized or localized.


1-↑ capillary blood pressure: cardiac edema, pregnancy edema and localized edema.

2-↓ colloidal OP of plasma proteins: nutritional, hepatic and renal edema.

3-↑ capillary permeability: allergy, inflam.

4-Lymphatic obstruction: Filaria, cancer.

Venous Circulation____________________________________________________________________________________________________________________________________________

Central venous pressure (CVP):

Pressure in right atrium & veins opening into it.

Normal value: 0-2 mmHg.

CVP fluctuates with respiration & cardiac cycle.


- CVP ↓ in hemorrhage.

- CVP ↑ in heart failure.

Functions of Veins___________________________________________________________________________________________________________________________________________

1-Transport vessels.

2-Capacitance vessels or blood reservoir:

Capacity is a ratio= Change in volume

Change in pressure

Effects of gravity on venous return________________________________________________________________________________________________________________________________________________

1-Orthostatic hypotension.

2-Pressure in different veins during orthostasis.

. Pressure in leg veins.

. Pressure in superior sagital sinus

Mechanisms helping venous return against gravity in standing position____________________________________________________________________________________________________________________________________________

1-Sympathetic vasoconstrictor tone.

2-Muscular pump.

3-Thoracic pump.

4-Cardiac suction:

. Atrial suction.

. Ventricular suction.

Coronary Circulation position____________________________________________________________________________________________________________________________________________

Anatomical considerations:

Right & left coronary arteries arise from coronary sinuses behind aortic valve.

Left coronary artery supplies anterior & lateral parts of left ventricle.

Right coronary artery supplies right ventricle and posterior part of left ventricle.

Venous blood of left ventricle drains into coronary sinus (75% of coronary blood). That of right ventricle goes through small anterior cardiac veins directly to right atrium.

Regulation of coronary blood flow position______________________________________________________________________________________________________________________________________________

1-Autoregulation (intrinsic mechanism):

↑ cardiac work → hypoxia, ↑ CO2, ↑ H+ ,↑ K+,

Lactate, prostaglandins & adenosine ------→

Coronary VD.

2-Mechanical regulation:

.During systole → ↓ coronary blood flow.

.During diastole → ↑ coronary blood flow.

3-Neural factors:

.Sympathetic: α-adrenergic (VC),β-adren (VD)

.Parasympathetic (vagus): VD.

Cardiovascular homeostasis in health & disease position____________________________________________________________________________________________________________________________________________

Circulatory shock:

It is inadequate tissue perfusion due to ↓ CO

Types & causes:

1-Hypovolemic: Hge, burn, trauma, surgery.

2-Disributive: fainting, anaphylaxis.

3-Cardiogenic: MI, CHF, arrhythmias.

4-Obsructive: obstruction of blood flow.

Hemorrhagic Shock position__________________________________________________________________________________________________________________________________________



↑ Heart rate

↑ Respiratory rate

↓ skin temperature





Compensatory reactions to hemorrhagic shock position____________________________________________________________________________________________________________________________________________

Rapid compensatory reactions:

1-Nervous factors.

2-Humoral factors.

Long-term compensatory reactions:

1-Correction of plasma volume.

2-Correction of plasma proteins.

3-Correction of red cell mass.