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General Pathology VDMP832 > Circulation and Fluid Balance > Flashcards

Circulation and Fluid Balance Flashcards

1
Q

Amoeba

A
  • In direct contact with their environment to:
    • Obtain nutrients
    • Excrete wastes
  • Conntractile vacuoles pump water in and out of the amoeba for these exchanges to occur
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2
Q

Circulatory System

A
  • Essential in multicellular organisms for cell survival
    • provide nutrients
    • Remove wastes
    • Maintain homeostasis
    • Coordinate function of diverse tissues
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3
Q

Microcirculation

A

Blood vessels

Lymphatics vessels

Extracellular Matrix

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4
Q

Microcirculation:

Blood vessels

A
  • Terminal Arterioles
    • endothelium, basement membrane, muscle
  • Capillaries
    • endothelium, basement membrane
  • Postcapillary venules
    • endothelium, basement membrane, muscle
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5
Q

Microcirculation:

Terminal Arterioles

A
  • Major resistance vessel of the arterial system
  • Regulate the flow of blood into a capillary bed
  • Pressure falls dramatically as blood flows through the arterioles into the capillary
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6
Q

Microcirculation:

Capillaries

A
  • The most numerous of all vessels, but generally contain only 5-10% of blood volume
  • Blood is directed into a capillary based on tissue needs
  • Interendothelial pores at the junctions between endothelial cells provide capillaries with a semipermeable nature
    • important to facilitiate diffusion of materials between the intravascular and extravascular spaces
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7
Q

Microcirculation:

Postcapillary Venule

A

Collect blood from a capillary bed to begin the venous retrum to the heart

Important site of cellular events associated with inflammation

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8
Q

Microcirculation:

Lymphatics

A

Blind-ended lymphatic vessels originate in association iwht the microcirculation

Important participants in fluid balance at the microcirculatory level

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9
Q

Microcirculation:

Interstitium

A

The space between cells and the microcirculation

COmposed of the extracellular matrix

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10
Q

Fluid Homeostasis

A
  • Fliud is in a constant flux between compartments of the microcirculatory environment
  • Interactions occur between
    • Cells and interstitium
    • Interstitium and blood vessels
    • Interstitium and lymphatic vessels
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11
Q

Normal water distribution

A
  • Total body water (60% body weight)
  • Extracellular water (20% body weight)
    • Plasma (4-5% body weight)
    • Interstitium (15-16% of body weight)
  • Intracellular water (40% body weight)
    • relatively stable compartment
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12
Q

Interactions:

Interstitium - Blood vessel

A
  • Blood vessel wall is the barrier that separates intravascular and interstitial compartment
  • Capillary wall is a semi-permeable membrane that allows selective movement of fluid and molecules
    • lipid soluble substances can move through the endothelial cells
    • Water and water soluble substances move through inter-endothelial pores
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13
Q

Interactions:

Interstitium - Lymphatic Vessels

A
  • Lymph vessel wall separeates the lymphatic and interstitial compartments
  • The wall functions similar to the capillary wall, but is much more permeable
  • Water moves freely between lymphatic vessel lumens and interstitium based on pressure gradients
    *
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14
Q

Control of intravascular/interstitial Fluid distribution

A
  • Anatomic integrity of the circulation
  • Osmostic pressure
    • plasma
    • Interstitium
  • Hydrostatic pressure
    • plasma
    • Interstitium
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15
Q

Intravascular/interstitial water distribution

A
  • Water flow across the endothelium is described by the following formula (See pic)
  • Differences in hydrostatic pressure are determined mainly by the volume of water in a compartment and any driving force acting on that volume
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16
Q

Intravascular/interstitial water distribution:

Osmotic Pressure

A
  • Determined mainly by large proteins or protein-disaccharides
    • small proteins and electrolytes account for most osmolality, but are equally distributed between fluid compartments
      • 84% of plasma osmolality is due to sodium and chloride
      • less than 1% of plasma osmolality is due to plasma protiens
      • Protein-disaccharides contribute to interstital osmolality
17
Q

Intravascular/interstitial water distribution:

Differences in Hydrostatic/osmotic pressure

A
  • Intravascular and interstital osmotic, and interstital hydrostatic pressures are relatively constant in the normal microcirculation
  • Differences in intravascular hydrostatic pressure between arteriolar and venular ends of the microcirculation are the major factor in driving water exchange between the plasma and interstitium
18
Q

Control of Fluid Distribution:

Net Filtration Pressure

A

Plasma/interstitium pressure differential at the arteriole

Net flow (nutrients) into the interstitium

19
Q

Control of Fluid distrobution:

Net absorption Pressure

A

Plasma/interstitium pressure differential at the venule

Net flow (wastes) into the plasma

20
Q

Control of Fluid Distrobution:

Lymph

A

Lymphatic vessels pick up excess fluid

21
Q

Changes in intravascular/interstitial water distrobution:

Edema

A

the increased accumulation of fluid in interstitial spaces or body cavities

22
Q

Changes in water distribution:

Edema

A
  • Mechanisms:
    • decreased plasma osmotic pressure
    • Increased plasma hydrostatic pressure
    • Decreased lymphatic drainage
    • Increased vascular permeability.
  • More than one mechanism is often involved in clinical edema
23
Q

Edema:

Decreased Plasma osmotic Pressure

A
  • Hypoalbuminemia is a common underlying factor in decreased plasma osmotic pressure
    • albumin is the major plasma protein that contributes to intravascular osmotic pressure
  • Due to the systemic nature of hypoalbuminemia, edema tends to be generalized
24
Q

Hypoalbuminemia

A
  • Conditions resulting in this include:
    • starvation
      • inadequate protein intake
    • Liver disease
      • decreased protein produciton
    • Renal Disease
      • Glomerular loss of albumin
    • Gastrointestinal Disease:
      • Malabsorption
      • Parasitism
    • Severe Burns
25
Q

Edema:

Increased Plasma Hydrostatic Pressure

A
  • Increased plasma Hydrostatic pressure creates a net outflow of fluid form the vessel to the interstitium
    • normal absorptive pressure at the venule becomes a filtration pressure
      • High venular hydrostatic pressure prevents reentry of fluid form the interstitium
  • Conditions resulting in this include:
    • increased blood flow
      • acute inflammation
    • Passive blood accumulation
      • venous obstruction
        • thrombi
        • masses; inflammatory or neoplastic
        • Organ torsions
      • Heart failure
        • Flow backs up at the heart
26
Q

Heart Failure:

Right Heart Failure

A
  • Fluid maldistribution can vary depending on the nature of the failure
    • right heart failure: Blood backs up in the protal circulation
      • fluid accumulates in the abdominal cavity
27
Q

Heart Failure:

Left Heart Failure

A
  • Fluid Maldistribution can vary depending on the nature of the failure
    • Left Heart Failure:
      • Blood backs up in pulmonary circulation.
        • Fluid accumlates in the alveloli of the lung (Pulmonary edema)
28
Q

Heart Failure

A
  • Generalized edema associated with generalized heart failure can result in reduced circulating blood volume
    • ADH and aldosterone stimulate water and sodium retention to contribute to hypervolemia and increased plasma hydrostatic pressure
29
Q

Edema:

Decreased Lymphatic Drainage

A
  • Any decrease in lymphatic flow prevents removal of the slight excess of fluid taht normally persists in the interstitium furing intravascular/intertitial fluid exchange
  • Conditions resulting in this include:
    • Lymphatic Obstruction:
      • Compression from inflammatory or neoplastic masses
      • Intralumenal obstruction by thrombi or emboli
  • Lymphatic Anomalies
    • Congenital anasarca/lymphedema
30
Q

Edema:

Increased Vascular Permeability

A
  • Decreased structural integrity allows water to move out of a vessel intot he interstitium more freely
  • Conditions resulting:
    • Inflammation:
      • Edothelial contraction and cytoskeletal rearrangement results in expansion of inter-endothelial junctions and fluid movement to the interstitium
      • Caused by histamine, bradykinin, leukotrienes, platelet activating factor, substance P
    • Immunologic Stimuli
      • many of hte same events that accompany imlammations
    • Direct endothelial injury
      • Toxins, Chemicals or infectious agents

Edema is usually localized

31
Q

Edema:

Morphology:

Gross:

A
  • Clear, gel-like fluid within tissue
    • tends to gravitate to ventral areas
    • Can occur in body cavities
      • ascites - abdomen
      • Hydrothorax - thoracic cavity
      • Hydropericardium - pericardial sac
32
Q

Edema:

Morphology:

Histologic

A

Eosinophilic amorphous material within a tissue

33
Q

Edema:

Significance

A
  • Edema can be insignificant to fatal
    • Subcutaneous edema has little functional significance
    • Cerebral or pulmonary edema are life-threatening
  • Clinical Classification:
    • Nutritional
    • Renal
    • Cardiac
    • Parasitic

General Pathology VDMP832 (26 decks)

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