Circulation and Fluid Balance

Question 1

Amoeba

Answer 1

• 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

Question 2

Circulatory System

Answer 2

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

Question 3

Microcirculation

Answer 3

Blood vessels

Lymphatics vessels

Extracellular Matrix

Question 4

Microcirculation:

Blood vessels

Answer 4

• Terminal Arterioles
  
  • endothelium, basement membrane, muscle
• Capillaries
  
  • endothelium, basement membrane
• Postcapillary venules
  
  • endothelium, basement membrane, muscle

Question 5

Microcirculation:

Terminal Arterioles

Answer 5

• 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

Question 6

Microcirculation:

Capillaries

Answer 6

• 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

Question 7

Microcirculation:

Postcapillary Venule

Answer 7

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

Important site of cellular events associated with inflammation

Question 8

Microcirculation:

Lymphatics

Answer 8

Blind-ended lymphatic vessels originate in association iwht the microcirculation

Important participants in fluid balance at the microcirculatory level

Question 9

Microcirculation:

Interstitium

Answer 9

The space between cells and the microcirculation

COmposed of the extracellular matrix

Question 10

Fluid Homeostasis

Answer 10

• 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

Question 11

Normal water distribution

Answer 11

• 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

Question 12

Interactions:

Interstitium - Blood vessel

Answer 12

• 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

Question 13

Interactions:

Interstitium - Lymphatic Vessels

Answer 13

• 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
  *

Question 14

Control of intravascular/interstitial Fluid distribution

Answer 14

• Anatomic integrity of the circulation
• Osmostic pressure
  
  • plasma
  • Interstitium
• Hydrostatic pressure
  
  • plasma
  • Interstitium

Question 15

Intravascular/interstitial water distribution

Answer 15

• 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

Question 16

Intravascular/interstitial water distribution:

Osmotic Pressure

Answer 16

• 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

Question 17

Intravascular/interstitial water distribution:

Differences in Hydrostatic/osmotic pressure

Answer 17

• 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

Question 18

Control of Fluid Distribution:

Net Filtration Pressure

Answer 18

Plasma/interstitium pressure differential at the arteriole

Net flow (nutrients) into the interstitium

Question 19

Control of Fluid distrobution:

Net absorption Pressure

Answer 19

Plasma/interstitium pressure differential at the venule

Net flow (wastes) into the plasma

Question 20

Control of Fluid Distrobution:

Lymph

Answer 20

Lymphatic vessels pick up excess fluid

Question 21

Changes in intravascular/interstitial water distrobution:

Edema

Answer 21

the increased accumulation of fluid in interstitial spaces or body cavities

Question 22

Changes in water distribution:

Edema

Answer 22

• 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

Question 23

Edema:

Decreased Plasma osmotic Pressure

Answer 23

• 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

Question 24

Hypoalbuminemia

Answer 24

• 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

Question 25

Edema: Increased Plasma Hydrostatic Pressure

Answer 25

* 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

Question 26

Heart Failure: Right Heart Failure

Answer 26

* 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

Question 27

Heart Failure: Left Heart Failure

Answer 27

* 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)

Question 28

Heart Failure

Answer 28

* 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

Question 29

Edema: Decreased Lymphatic Drainage

Answer 29

* 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

Question 30

Edema: Increased Vascular Permeability

Answer 30

* 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

Question 31

Edema: Morphology: Gross:

Answer 31

* 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

Question 32

Edema: Morphology: Histologic

Answer 32

Eosinophilic amorphous material within a tissue

Question 33

Edema: Significance

Answer 33

* 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