(2) Circall - Systemic circulation is similar to a parallel...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Circulation • The main function of the systemic circulation is to deliver adequate oxygen, nutrients to the systemic tissues and remove carbon dioxide & other waste products from the systemic tissues • The systemic circulation is also serves as a conduit for transport of hormones, and other substances and allows these substances to potentially act at a distant site from their production Functional Parts • systemic arteries – designed to carry blood under high pressure out to the tissue beds • arterioles & pre capillary sphincters – act as control valves to regulate local flow • capillaries- one cell layer thick – exchange between tissue (cells) & blood • venules – collect blood from capillaries • systemic veins – return blood to heart/dynamic storage Basic theory of circulatory function • Blood flow is proportional to metabolic demand • Cardiac output controlled by local tissue flow • Arterial pressure control is independent of local flow or cardiac output Characteristics of Vessels • Components – Endothelium- one layer exists in all vessels – Elastic tissue (1) – Smooth muscle (2) – Fibrous tissue (3) • Relative composition – Aorta 1>3>2 – typical artery 2>1>3 – vein 1 = 2 = 3 – capillary- only endothelium Hemodynamics • Flow • Pressure gradient • Resistance • Ohm ` s Law – V = IR (Analogous to Δ P = QR) Flow (Q) • The volume of blood that passes a certain point per unit time (eg. ml/min) • Q = velocity X cross sectional area – At a given flow, the velocity is inversely proportional to the total cross sectional area • Q = Δ P / R – Flow is directly proportional to Δ P and inversely proportional to resistance (R)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Pressure gradient • Driving force of blood • difference in pressure between two points • proportional to flow (Q) • At a given Q the greater the drop in P in a segment or compartment the greater the resistance to flow. Resistance • R= 8 η l/ π r 4 η = viscosity, l = length of vessel, r = radius • Parallel circuit – 1/R T = 1/R 1 + 1/R 2 + 1/R 3 + … 1/R N – R T < smallest individual R • Series circuit – R T = R 1 + R 2 + R 3 + … R N – R T = sum of individual R ` s • The systemic circulation is predominantly a parallel circuit Advantages of Parallel Circuitry • Independence of local flow control – increase/decrease flow to tissues independently • Minimizes total peripheral resistance (TPR) • Oxygen rich blood supply to every tissue Viscosity • Internal friction of a fluid associated with the intermolecular attraction • Blood is a suspension with a viscosity of 3 – most of viscosity due to RBC ` s • Plasma has a viscosity of 1.5 • Water is the standard with a viscosity of 1 • With blood, viscosity 1/ velocity Viscosity considerations at microcirculation • velocity decreases which increases viscosity – due to elements in blood sticking together • cells can get stuck at constriction points momentarily which increases apparent
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/03/2011 for the course PHYS 339 taught by Professor Free during the Spring '11 term at Palmer Chiropractic.

Page1 / 19

(2) Circall - Systemic circulation is similar to a parallel...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online