Circulation + Fluid Dynamics Flashcards

1
Q

Endothelium

Characteristics, Types, Roles

A

single cell layer that lines all components of circulatory system -> continuous system

acts as an important interface between blood + tissue

critical factor in fluid distribution, inflammation, immunity, angiogenesis, hemostasis

types:
- continuous
- fenestrated
- discontinous (sinusoidal)

range in level of control exhibited over movement of substances between blood + supplied tissue

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2
Q

Continuous Endothelium

A

strong barrier that tightly controls molecule passage

only H2O + O2 + CO2 + ions can cross membrane or via tight junctional complexes

found in = brain (BBB), muscle, lung, bone

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3
Q

Fenestrated Endothelium

A

allows controlled transfer of certain mol. + proteins

have pores + junctional complexes

provides filtration

seen in = renal glomeruli, intestinal villi, endocrine glands, choroid plexuses, ciliary processes of eye

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4
Q

Discontinuous Endothelium

A

free transfer of mol, cells, water, etc.

relatively open juncitonal complexes between endothelial cells

also associated with discontinuous basement membrane

seen in = liver sinusoids, spleen sinusoids, bone marrow, lymph nodes

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5
Q

Normal v Abnormal Endothelium

A

normal = antithrombotic + profibronilytic
v
abnormal = prothrombrotic + antifibrinolytic

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6
Q

Causes of Endothelial Cell Injury or Activation

A

oxidative stress/injury
hypoxia
inflammation
infectious agents
tissue injury

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7
Q

Stroke Volume

A

volume of blood pumped per beat by the respective ventricle

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8
Q

Cardiac Output

A

volume of blood pumped by each half of the heart per minute

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9
Q

Arteries + Arterioles

A

Arteries:
- relatively large lumen diameter
- thick + strong walls
- smooth muscle fibers for strenght
- elastic fibers for elasticity

Arterioles:
- smaller than arteries
- walls primarily of smooth muscle
- major pressure/resistance vessels of circ. system

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10
Q

Capillaries

A

site of nutrient + waste exchange between blood + tissue

major component of microcirculation

capillaries have minimal structure -> single layer of endothelial cells + NO smooth muscle

narrow lumen, low pressure -> RBCs move in single file line

slow pace + low RBC density -> aid with movement of nutrients + waste products

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11
Q

Postcapillary Venules + Veins

A

postcapillary venules provide a low resistance path for blood
- thin layers of muslce present as move away from capillary bed

veins are larger + consists of collagen w/ small amounts of elastin + smooth muscle
- low resistance path
- return blood to heart

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12
Q

Blood return to heart assisted by

A

venous valves
skeletal mm. contractions
venous vasoconstriction
cardiac-suction effect
respiratory pump

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13
Q

Lymphatic System

A

structure similar to vascular capillaries

low pressure + distensible

fluid + molecules should move into lymphatic vessels + not out

large interendothelial gaps allow movement of larger particles + substances, relative to capillaries

converge into progressively larger vessels that drain into lymph nodes

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14
Q

Microcirculation

A

environment formed by intersection of:
- blood capillaries
- lymphatic capillaries
- interstitium
- tissue cells

interstitium consists of interstitial fluid + extracellular matrix (ECM)

ECM is the tissue portion of interstitium
- structural, adhesive, absorptive components

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15
Q

Normal Fluid Distribution

A

water makes up ~60% of BW, distributed between IC + EC spaces

EC fluid subdivided between plasma + intersitium

distribution of nutrients + waste controlled by:
- pressure + conc. gradients
- physical barriers

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16
Q

Fluid Movement at capillary bed influenced by:

A

osmotic pressure
-significantly different between plasma + intersititum -> primarily d/t albumin

hydrostatic pressure
- effects of high v low pressure

rate of blood flow
- effects of high v low flow rate

17
Q

Normal Fluid Distribution + Homeostasis

A

following capillary drainage, any fluid left in intersitium is drained by lymphatics

net effects of pressure + forces -> slightly favor fluid return to vasculature

constant fluid flow needed to continually supply nutrients to + remove waste products from cells

intersititial fluid as a buffer for plasma volume changes

18
Q

Changes in hydrostatic pressure

Imbalance between IC + Interstitial Spaces

A

explanded plasma vol. (hypervolemia) -> increased IF
- if prolonged, fluid moves into cells along somotic + hydrostatic gradients (cell swelling)

reduced plasma vol. (hypovolemia) -> reduced IF
- if prolonged, fluid moves out of cells alomg osmotic + hydrostatic gradients (cell shrinkage)

19
Q

changes in osmotic pressure

Imbalance between IC + Interstitial Spaces

A

increased OP -> increased intersitial OP
- if prolonged, sodium + fluid move into cells along osmotic gradient (cell swelling)
- ex) water deprivation, sodium toxicity w/ restrict water

reduced OP -> reduced interstitial osmotic gradient
- if prolonged, sodium + fluid moves out of cells along osmotic gradient (cell shrinkage)

20
Q

Edema v Effusion

Imbalance Between IV + Intersititial Spaces

A

Edema
- abnormal accumulation of fluid in interstitium from plasma
- results inn tissue swelling within intersitial space

Effusion
- abnormal accumulation of fluid in a body cavity d/t imbalances between interstitial + intravascular compartments

21
Q

Major Mechanisms of Edema/Effusion Formation

A

increased microvascular permeability
increased IV hydrostatic pressure
decreased IV osmotic pressure
decreased lymphatic drainage

22
Q

Increased microvascular permeability

Mechanisms for Edema/Effusion

A

commonly a reaction to inflammatory/immune stimuli

sequence of events:
- stimulus
- vasodilation + widening of interendothelial junctions
- fluid movement out of vascular space into interstitium +/or body cavity

early on -> low protein conc. + low cellularity of fluid (transudate)
progression -> increasing protein content + influx of inflammatory cells (eventual exudate)

intention is to dilute an inflammatory agent +/- deliver needed cytokines, chemokines, cells, etc.

creates local tissue swelling or fluid accumulation in a body cavity

23
Q

Increased IV Hydrostatic Pressure

Mechanisms for Edema/Effusion

A

usually d/t increased blood vol. in microvasculature

Causes:
- less common = hyperemia such as d/t inflammation
- mroe common = congestion

24
Q

Decreased IV Osmotic Pressure

A

most commonly d/t severe decreases in plasma albumin conc.

Sequence of events:
- reduced albumin reduces colloidal OP
- increased fluid movement out of microvasculature into interstitium with simultaneous decreased fluid drainage from interstitium to microvasculature
- tissue edema/cavitary effusion formation

Causes of severe hypoalbuminemia:
- protein-losing nephropathy
- protein-losing enteropathy
- decreased production by liver d/t severe disease
- plasma exudation from severe, diffuse skin disease/burns

25
Decreased Lymphatic Drainage
compression/obstruction of lymphatic outflow -> reduces drainage of normal excess interstitial fluid this mechanism usually limited to specific tissue area or single body cavity causes: - external mass/swelling (neoplastic v inflammatory) - constriction d/t fibrosis/ligation - internal occlusion d/t clot/barrier
26
Morphologic Characteristics of Edema + Effusions
edema may form in specific tissue or generalized throughout body - swollen, doughy or fluctuant tissue - may be cooler than adjacent unaffected tissue - expansile v confined space effects single body cavity, bicavitary or tricavitary: - fluid wave - expansile v confined space effects
27
Fluid Analysis of Effusion
diagnostic classification of effusion based on protein conc., nucleated cellularity, microscopic features may help with differential diagnoses for cause of effusion General categories: - transudate - exudate - modified transudate specific effusion types = septic, feline infectious peritonitis, hemorrhagic effusion, chylous effusion