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Flashcards in Fluid flow Deck (49):

Circulatory System definition

-what organisms don't need it - what they use instead

-Bulk flow defn.

-A system that transports nutrients, wastes and signalling molecules (i.e. hormones) between body tissues
-v. small organisms don't need it -> rely on diffusion (only good if small, flat or porous)

*large animals move fluid through bodies by bulk flow
-Bulk Flow: Movement of fluid as a result of a pressure gradient


-How fluid is moved

-3 components of circulatory system

-Moved by generating pressure in one part of circuit to create pressure gradient

*3 parts;
-Pump (all involve muscle contraction)
-System of tubes


Types of Circulatory systems;

-open and closed
-what fluid within each one called

-2 other types of fluid

-Open Circulatory system: Circulatory fluid comes in direct contact w/ tissues in spaces (sinuses)
-Hemolymph is the fluid that circulates these systems
-Closed circulatory system: Circulatory fluid stays w/in blood vessels
-Blood is fluid that circulates this system (plasma + cells)

Other fluids: Interstitial (ECF that bathes tissues) and Lymph


Evolution of Circulatory Systems -> Overview

-what evolved to do first

-Driving force for evolution

-First evolved to transport nutrients
-very early on began to serve as a respiratory function (has been driving force for evolution of this system)
*O2 limits what an organism can do metabollically

-Other things that affect oxygen delivery requirements;
-metabolism, altitude, size, level of activity, endothermic


Common features of vertebrate circulatory system

-Closed (blood separate from tissue fluid)
-note: not all invertebrates have open
-2 or more contractile chambers of myocardial tissues, w/ valves to ensure unidirectional blood flow
-2 or more heart chambers
-progressive increase in separation of blood flow to gas exchange organs and rest of body


Advantages of closed circulatory system (3)

-Can generate higher pressures - blood flows more rapidly )means quicker nutrient and waste transport)
-Resistance in blood vessels can be changed (blood flow can be more tightly regulated and easily redirected to specific tissues)
-Cellular elements and transport molecules kept within vessels (means specific molecules have evolved w/ closed system - i.e. haeme)

*generally support higher lvls of metabolic activity


2 types of myocardium used to generate contractile force

-which one prominent over time

-Spongy: meshwork of loosely connected cells (not hugely efficient)
-Compact: Tightly packed cells arranged in a regular pattern (no space for blood -> lead to evolution of coronary circuit)
-downside: v. dependent on coronary circuit

*shift from mostly spongey to compact over time


Number of Heart chambers over time

-what current groups have

-Vertebrate hearts are first to have 2 chambers
-all have at least 1 atrium and one ventricle
-Heart evolved from 2 chambers in fish to three in amphibians and reptiles, and four in crocodilians, mammals and birds


Fish Heart

-what two chambers allow

-what made of
-what emerged in this heart

-First group to develop multi-chambered heart
-gills require more efficient circulatory system working at higher pressure
-2 chambers allow separate collection and pumping of blood (also continuous blood flow)
*mostly spongy myocardium
*emergency of polarised contraction (posterior -> anterior)


Fish circulation

-Ventrical located ventral to atrium (gravity helps blood flow)
-Most of pressure from ventricular contraction dissipated passing through gills
-blood flowing to tissues is at relatively low pressure (still good enough for tuna and marlin)


Amphibian Heart

-no. of chambers
-How blood flow occurs

-type of myocardium tissue

-3 chambered (2 atria, 1 ventricle)
-Oxgenated blood from lungs -> left atrium, deoxygenated from tissues -> right atrium
*both types of blood enter 1 ventricle (v. little mixing - trabeculae may help)

*mostly spongy myocaridum
-evolved separately to lungfish heart (even tho similar)


Amphibian Circulation

-extra way can get oxygen - how it helps

-Partially separated pulmonary and systemic circuits
-means can have higher systemic pressures
-Gas exchange also occurs at skin, buccopharyngeal mucosa
-oxygenated blood from skin mixes w/ deoxygenated - supplies heart with O2
-only pulmonary circuit has separate venous return to heart


Reptile hearts (turtles, snakes and lizards)

-chambers (no.)
-special feature
-type of tissue

-3 chambered heart (2 atria, 1 ventricle)
-Have complex ventricular structure (3 sub chambers divided by muscular ridges)
-ridges separate flow of oxygenated and deoxygenated blood
-small in turtles, but large in lizards and snakes (less mixing)
*mostly compact myocardium
-2 aortas rather than one


Reptile circulations

-extra features
-what it allows reptiles to do

-Left aorta takes oxygenated blood from left side; right aorta takes blood from both sides of ventricle to body
-if reptile stops breathing, contraction of blood vessels in lung = increased resistance
-blood diverted from lungs into systemic circuit when not breathing (extra aorta allows this)


Crocodile heart

-heart chambers
-no of aortas
-what they allow

-4 chambered heart
-2 aortas
-Blood bypasses lungs when animal is submerged (pulmonary pressure increases, opens valve - means less oxygen goes to lungs, more goes to body)


Avian and Mammalian Hearts

-separation of blood?
-type of myocardium

-4 chambered w/ valves to prevent backflow of blood
-ventricles separated by intraventricular septum
-Is COMPLETE separation of oxygenated and de-oxygenated blood
-very different pressures in pulmonary and systemic circuits

*compact myocardium


Advantages of Separate pulmonary and Systemic Circulations (3)

1. Oxygenated and deoxygenated blood cannot mix -> systemic circulation receives blood with highest O2 content (v. efficient)
2. Maximises respiratory gas exchange (large gradient)
3. Pulmonary and systemic circuits can operate under different pressures (allows nutrients to get to tissues faster)


Other evolutionary changes in cardiovascular system

-Specialised electrical conduction

-Myocardial cell replication

1. Specialised electrical conduction
-pacemaker cells present v. early in evolution (allows rhythmic activity)
-Fish and amphibia first to demonstrate ordered contraction
-mammals have specialised conduction pathways (better co-ordinated contraction)
2. Myocardial cell replication
-ability to efficiently replace lost myocardial cells disappears around appearance of endothermy (frogs can generate heart cells)
-Mammals can't generate significant numbers of new ventricular myocytes after birth



-what it is

-2 components

Blood: fluid in heart and blood vessels
-Divided into plasma portion (water component - has ions, organic solutes and proteins) and cellular portion (produced from stem cells in bone marrow)


Red Blood cells


-Advantages of biconcave erythrocyte shape

-Are the most numerous cellular component
-Specialised for oxygen transport
-Shape varies - round, oval or biconcave
Advantages of biconcave;
-Large SA, sort distance b/w interior and exterior edge (favors diffusion
-can deform to squeeze through small capillaries
-can tolerate a degree of swelling w/out bursting


Blood flow around body

-5 types of blood vessels blood encounters

Blood flow through Heart;

-how moves
-How gradients generated (2 factors)

-Blood encounters 5 types of vessels; each w/ different structural features and functions
->veins, arteries, venules, arterioles, capillaries
Blood flow through heart;
-blood flows passively down pressure gradients
-gradients generated by venous return and contraction of heart
*unidirectional heart valves stop backwards blood flow


The Cardiac Cycle

-what it is

-Systole and diastole

-Cardiac Cycle: the electrical and contractile (mechanical) events associated with the movement of blood through the heart during a single heart beat

Systole: contraction; blood forced into next chamber or out into circulation

Diastole: Relaxation; blood enters the chamber

*atria contract together; ventricles contract together


Electrical activity of the heart

-how generated
-How electrical activity travels in heart

-Cardiac cycle involves rhythmic contraction of heart chambers in response to electrical activity (depolarisation)
-is initiated in sinoatrial node
-spreads across the atria and then to ventricles via atrioventricular node


Electrical activity and blood flow of the heart

-orderly spread of electrical activity leads to co-ordinated contraction of heart chambers
-SA node deploarises spontaneously
-atria depolarise together, contract together -> blood to ventricles
-delay during atrio-ventricular spread of depolarisation -> blood flows to ventricles
-ventricles depolarise together, contract together -> blood flows to artieries


Monitoring cardiac efficiency (2 methods)

-their definitions and features

1. Cardiac output: the amount of blood pumped by the heart every minute
-heart rate x stroke volume (volume of blood pumped per stroke)
-stroke volume is difference b/w amount of blood that collects in ventricle during diastole and what is left at end of systole
2. Blood pressure: pressure exerted by blood on arterial walls
-depends on cardiac output and peripheral resistance
-is highest during ventricular contraction (systolic pressure)


How to measure blood pressure

-Done with a sphygmomanometer (pressure monitor) and stethoscope
-Relies on fact that smooth (laminar) blood flow is silent, while turbulent blood flow is audible


Control and regulation of circulation

-Heart rate controlled by autonomic nervous system
-Brain regulatory centers monitor incoming info about BP/Volume - act via ANS
-ANS has 2 branches; sympathetic (fight or flight) and parasympathetic (rest and digest)
-increase and decrease heart rate respectively


Dive Reflex

-what it is
-what declines specifically

-Tachycardia - what is it

-Diving mammals conserve blood oxygen stores by slowing HR during dives (aka Diving bradycardia - decreased HR)
-Decreased heart rate relative to anticipation of dive depth
-stroke volume remains constant - decline is in cardiac output
-is an ancient response to oxygen insufficiency
-Tachycardia = increased HR


Blood pressure in diving seals

-what happens to HR, stroke volume, cardiac output and blood pressure

-special feature

-Seals demonstrate integrated, body wide reorganisation of cardiovascular function
-if HR drops, stroke volume doesn't change, cardiac output drops
-blood pressure maintained by increasing peripheral resistance
*diving seal shows arterial constriction of all blood vessels except in lung, brain, heart and eyes


Other phyiological adaptations for diving


-Enteer hypometabolic state (low metabolism)
-Very high oxygen storing capacity
-greater blood volume
-greater O2 carrying capacity of blood (mobilise more RBC from spleen)
-more myoglobin in muscles



-relationship to flow rate and cross sectional area

Two most important terms to describe movement of fluids:
-Flow (Q): volume of fluid transferred per unit time (cm3/sec)
-Velocity (V): Distance travelled by fluid per unit time (Cm/sec)

Velocity is proportional to flow rate (as flow increases, so does velocity)
-BUT, inversely proportional to cross sectional area
-if cross-sectional area increases, velocity decreases (narrower vessel - the faster the velocity of flow)


Determinants of Fluid Flow
-flow and pressure
-flow and resistance

-Flow is;
-proportional to pressure gradient (as pressure increases, so does flow)
-inversely proportional to resistance (as resistance increases, flow decreases)


Poiseuille's Law
-what it describes relationship between

-Is the relationship between fluid flow, pressure differences and resistance


Pressure Gradient and fluid flow

-general concepts

-pressure generation in cardiovascular system

-Fluid flows from high pressure to low pressure
-is proportional to the pressure difference between two areas (larger the difference, higher the flow)
*mainly generated by contraction of heart in cardiovascular system
-gravity also contributes


Resistance and Fluid flow

-what is resistance?
-Flow and resistance relationship
-4 factors that affect resistance

-Resistance: friction that opposes blood flow
-Flow INVERSELY proportional to resistance
-fluid loses some kinetic energy as heat when faced with resistance
-Factors that affect resistance;
-Tube length, tube radius, fluid viscosity and flow pattern


Tube length and fluid flow

Tube radius and fluid flow
-degree of flow change in response to radius change

-As tube length increases, resistance increases

-As tube radius decreases, resistance increases
-resistance is a function of fourth power of radius (therefore a small change in radius leads to a very big change in resistance)


Flow pattern and relation to resistance

-2 types of flow and their features

-More turbulent blood flow leads to increased resistance

1. Laminar Flow:
-Fluid moves in concentric layers, w/ highest velocity in middle of tube
-Some friction between adjacent layers moving at different velocities

2. Turbulent Flow:
-Breakdown of laminar flow, radial fluid movement -> mixing
-Much higher resistance than laminar flow


Causes of turbulence

-cause in biological system too

-Likely with high density, low viscosity fluids travelling at high velocity through large diameter tubes

*also by irregularities in tube walls or abrupt change in dimensions


Haemodynamics - definition

-Refers to the forces generated by the heart and movement of blood through the cardiovascular system


Resistance to flow in the cardiovascular system

-what contributes most to change in resistance

-Viscosity and length not normally considered when assessing blood flow in vasculature
-Constant or slow to change unless disease
*Most important contributor to resistance in blood vessels is changes in vessel radius (smooth muscle)


Blood flow by regulating radius

-how constriction in one part affects other part

-Vasoconstriction and vasodilation

-Blood diverted between organs regulating blood vessel radius (smooth muscle contraction)
-constriction of blood vessel leads to increased pressure in another region
-leads to increase in peripheral resistance (increased blood pressure)

Vasoconstriction: Decrease in vessel radius
Vasodilation: increase in vessel radius


Special properties of flow in cardiovascular system (4)

-Blood viscosity is variable
-Blood pressure is pulsatile
-Blood vessel walls are distensible (not rigid)
-Blood flow is not always laminar


Variability of Blood viscosity

-3 factors and how changes in them affect fluid flow

-Blood is a suspension
Varies depending on;
-Haematocrit (proportion of RBCs)
-more = higher viscosity
-RBC shape
-Healthy RBCs flexible; decreased flexibility = increased viscosity
-flexibility lost with sickle cell anemia
-Blood flow
-blood tends to clot at low flow rates (low rate = increased viscosity)
-can occur during shock, hypotension, prolonged immobility


Blood pressure is pulsatile - why

-Variable pressure gradient = flow decreases between heart beats
-peaks in systole, troughs in diastole


Blood vessels are not rigid

-How -> veins and arteries compared

-How arteries dampen pressure changes

-Blood vessels are compliant (expand in response to pressure) and can be elastic (recoil when stretched)
-veins particularly compliant (Store blood)
-Arteries are particularly elastic (store pressure)
-dampen pressure changes - as pressure drops, artery recoils to constrict artery = higher minimum pressure
-blood enters, artery stretches and dilate to lessen pressure


Blood flow is not always laminar

-Normal changes in cardiovascular chamber dimension causes turbulence
-irregularities in blood vessel wall during disease can cause turbulence


Gravity and the cardiovascular system

-hydrostatic pressure -> definition


-Hydrostatic pressure = pressure on a vertical column of fluid due to gravity
-is proportional to the height of the column
-gravity flows from high potential energy to low potential energy
-Blood pressure is influenced by both the pressure generated by the heart and the pressure exerted by gravity


Gravity and blood flow

-lying down and standing up

Lying down: all parts of body at same height -> hydrostatic pressure constant across circulation
-no gradient therefore gravity doesn't affect flow (pressure will naturally decline as it moves from heart (due to resistance))

Standing Up: Gravity promotes movement of blood to feet; gravity opposes return of blood from feet to heart (decreased venous return)
- Blood moving into feet due to gravity exerts pressure on blood vessel walls -> higher blood pressure in feet
*lowest BP at head, highest at feet; heart = somewhere in between


Venous Return -> 3 mechanisms that help veins defy gravity

-Gravity opposes return of blood from feet to heart via veins
-body has several mechanisms to promote venous return;
1. Valves: facilitates unidirectional flow (stops backflow) -> located in peripheral veins
2. Skeletal muscle pump: contraction of muscle squeezes veins - valves stop blood going back
3. Respiratory pump: diaphragm drops during inhalation -> decreases pressure around heart, increases venous return.
-valves stop blood flowing backwards during exhalation

*valves extremely important