Test 2 - Circulatory Disturbances Flashcards
What is the microcirculation?
The microcirculation consists of arterioles (small arteries proximal to a capillary bed), metarterioles (arterial capillaries), capillaries (thin, semipermeable vessels that connect arterioles and venules), and postcapillary venules (small vessels that merge to form veins after collecting blood from a capillary network). Smooth muscle of the arterioles and metarterioles regulates flow of blood into the capillary bed. There is a dramatic drop in pressure and blood flow rate from the arterial to the venous side of the microcirculation, facilitating interactions between capillary blood and interstitial fluid. Blind-ended lymphatic vessels that originate near capillary beds interact
intimately with the microcirculation.
Microcirculation is so called because its components are only visible with the microscope.
Define hemostasis.
Arrest bleeding by the physiological properties of vasoconstriction and coagulation or by surgical means
What are the different functions of the vascular endothelium?
Role in hemostasis
- Anti-thrombotic & pro-fibrinolytic in the normal state
- Pro-thrombotic and anti-fibrinolytic during injury
Modulates perfusion:
- NO relaxes and causes vasodilation
- Endothelin causes vasoconstriction
Role in inflammation:
- Regulates the traffic of inflammatory cells
- Produces pro-inflammatory cytokines
- Control angiogenesis and tissue repair
Describe the fluid distribution of the body.
Total Body Water: 65% of total body weight
- Plasma (5%)
- Interstitial Fluid (15%)
- Intracellular Fluid (40%)
- Transcellular Fluid (5%)
Define interstitium.
What is it composed of?
- Space between tissue compartments (microcirculation and the cells).
- Composed of the Extracellular Matrix (ECM) and supporting cells
What is the medium through which all metabolic products must pass between the microcirculation and the cells?
The interstitium
What is the ECM composed of?
Composed of structural molecules (collagen, reticulin, elastic fibers) and ground substance (glycoproteins like fibronectin & laminin, plus glycosaminoglycans, proteoglycans etc..)
What accounts for the water distribution between the two compartments of plasma and interstitium?
Hydrostatic and osmotic pressures
Describe how changes in hydrostatic and osmotic forces may lead to tissue edema.
“Capillary hydrostatic and osmotic forces are normally balanced so that there is no net loss or gain of fluid across the capillary bed. However, increased hydrostatic pressure or diminished plasma osmotic pressure will cause extravascular fluid to accumulate. Tissue lymphatics remove much of the excess volume, eventually returning it to the circulation via the thoracic duct; however, if the capacity for lymphatic drainage is exceeded, tissue edema results”.
Define edema.
- Abnormal accumulation of excess extracellular water in interstitial spaces or in body cavities
- Fluid is outside both the vascular fluid compartment and cellular fluid compartment (i.e.: within the interstitium).
What are the pathomechanisms of edema?
- I_ncreased blood hydrostatic pressure:_ (Generalized: e.g. right-sided congestive heart failure (CHF); Localized: e.g.: tightly bandaged limb resulting in venous occlusion.
- Decreased plasma colloidal osmotic (a.k.a. oncotic) pressure: Proteins not absorbed from diet (e.g.: starvation, GI malabsorption), Proteins not produced (e.g.: liver disease), Protein loss (e.g. glomerular disease, Intestinal mucosal damage)
- Lymphatic obstruction. Damage/ obstruction of lymphatics (e.g.: surgery, neoplasms, inflammation)
- Increased vascular permeability (Inflammation)
What are the two classifications of edema?
- Inflammatory: Increased vascular permeability – refers as an “exudate”. Edema fluid in these cases is “protein rich” –> an exudate (high protein content (>30g/L), specific gravity (>1.025), total nucleated cells (<7x109L) –> less than 7,000 cells per μl.
- Non-inflammatory (e.g.: edema of CHF; edema of liver failure) – refers to as a “transudate”. Edema fluid in these cases is “protein poor” –> low protein content (<30g/L), low specific gravity (<1.025), low cellularity (<1.5x109L) –> less than 1,500 cells per μl.
Describe the gross appearance of edema.
- Wet
- Gelatinous and heavy
- Swollen organs
- Fluid seeps from cut surfaces
- May be yellow
Describe this image of the gastric wall of a horse.
Edema
- Wet
- Gelatinous and heavy
- Swollen organs
- Fluid weeps from cut surfaces
- May be yellow
Describe the histological appearance of edema.
- Clear or pale eosinophilic staining depending on whether is non-inflammatory or inflammatory edema.
- Spaces are distended
- Blood vessels may be filled with red blood cells
- Lymphatics are dilated
- Collagen bundles are separated
Define pitting edema.
When pressure is applied to an area of edema a depression or dent results as excessive interstitial fluid is forced to adjacent areas
Hydrothorax
Fluid in the thoracic cavity
Pericardial Effusion
“Mulberry heart disease”- (inflammatory edema). Note fibrin strands and cloudy appearance of the pericardial fluid.
Ascites/Hydroperitoneum
Fluid (transudate) within the peritoneal cavity
Anasarca
Generalized edema with profuse accumulation of fluid within the subcutaneous tissue
Edema is dependent on ________.
Extent, location, and duration
How does tissue change after prolonged edema?
Tissue may become firm and distorted due to an increase in fibrous connective tissue after prolonged edema
What are the types of pulmonary edema? Describe their mechanisms.
Non-inflammatory edema: e.g.: Associated to left-sided congestive heart failure (CHF).
Inflammatory edema: Damage to pulmonary capillary endothelium –> e.g.: pneumonia
ARDS (Acute respiratory distress syndrome) Sudden, diffuse and direct- increase in vascular
permeability: high fatality rate –> Followed by pneumonia if animal survives
What is most associated with chronic pulmonary edema?
Describe the pathophysiology.
- Most commonly associated with cardiac failure
- Alveolar walls become thickened –> may lead to fibrosis
- Congestion, micro-hemorrhages –> and accumulation of heart failure cells
What are siderophages?
Hemosiderin-laden Macrophages* (“heart failure cells”) within alveoli
Describe the difference between hyperemia and congestion.
- Both terms indicate a local increase in blood volume and flow within the vascular bed.
- Hyperemia indicates increase of arteriole-mediated engorgement of the vascular bed. Blood is oxygenated (red).
- Congestion indicates passive, venous engorgement. Blood is not oxygenated (blue).
Pathological hyperemia is caused by an underlying pathological process – usually ______.
Inflammation
_________ is one of the cardinal signs of inflammation. What are the other signs?
Reddening (rubor)
tumor, calor, rubor, pain, loss of function
Describe the mechanism of congestion.
What are the different ways to classify it?
Passive engorgement of vascular beds caused by a decreased outflow of blood
Since the vascular beds are engorged with poorly oxygenated blood tissues are dark red to blue (cyanotic), depending on the degree of stagnation.
Like other lesions it can be classified according to duration (acute or chronic) and its extent:
localized (e.g. isolated area of venous obstruction); generalized: Systemic change like in CHF.
List some examples of physiological hyperemia.
- Digestion: ↑ blood flow to the GI tract during digestion.
- Exercise: ↑ blood flow to muscles during exercise
- To dissipate heat: ↑blood flow to the skin to dissipate heat and cool down.
- Neurovascular: Involuntary ↑in blood flow to the face (facial hyperemia) as a result of embarrassment or emotional distress –> common in people with social anxiety.
What is this?
Pitting Edema
What is this?
(Heifer)
Hydrothorax (idiopathic pulmonary hypertension)
What is this?
Pericardial effusion – “mulberry heart disease”- (inflammatory edema). Note fibrin strands and cloudy appearance of the pericardial fluid.
What is this?
Ascites or hydroperitoneum: fluid (transudate) within the peritoneal cavity. Dog with CHF
What is this?
Ascites, horse with CHF
What is this?
Anasarca: Generalized edema with profuse accumulation of fluid within the subcutaneous tissue
What is this?
Submandibular edema (“bottle jaw”), is commonly associated with severe GI parasitism and hypoproteinemia in sheep
What is this?
(Horse)
Horse, forelimb. This animal had generalized edema due to protein-losing enteropathy
What is this?
What characteristics make this obvious to you?
(Pig)
Pulmonary Edema
How to distinguish pulmonary edema in the lungs:
See enlarged lungs –> when you open the thoracic cavity, normally the lungs will collapse. But when you open it up and there is pulmonary edema you will still see them occupying a large amount.
- Pleural surface looks moist or wet
- Will also see impression of the lungs (this is not normal!)
- If you open the trachea - see frothy fluid - this Is abnormal and suggestive of the presence of pulmonary edema
- Interlobular connective tissue - gives lobulation of pulmonary parenchyma. See expansion of CT. Gelatinous/yellow appearance.
What is this?
(Horse)
Pulmonary Edema
This is the the histological appearance of what disorder?
Pulmonary Edema
What is the arrow pointing to?
What is distinct about this cell?
What is this associated with?
HE-stain, dark brown pigment within the cytoplasm of alveolar macrophages
These are also known as “heart failure cells” or siderophages.
This is diagnostic of chronic pulmonary edema associated with Left sided congestive heart failure. The brown pigmentation results from the phagocytation of the RBCs and metabolizing iron.
What is this? What type of Hyperemia is it?
(Dog)
Gingivitis - this is pathological hyperemia (arterial) associated with edema/inflammation.
What is this? What type of Hyperemia is it?
Bulbar and palpebral Conjunctivitis
Pathological Hyperemia (arterial)
What is this? Describe what happens as a result of this condition.
(Dog)
Gastric volvulus(torsion) in a dog : Twisting of vessels obstructs gastric veins → severe venous congestion (acute, local, congestion) → ischemia (necrosis) → loss of endothelial integrity → hemorrhage →shock → death
What is this?
(Horse)
Intestinal volvulus
What is this?
(Horse)
Colonic torsion
What is this?
What is it typically associated with?
(Dog)
[Acute] Pulmonary congestion: Usually the result of heart failure and associated with edema.
What is this?
(Dog)
Diffuse brownish discoloration of the lungs of a dog with chronic pulmonary edema and congestion secondary to left-sided CHF
What is this?
(Horse)
Livers of horses with right-sided CHF.
This is condition is also known as _______.
What is it associated with?
Nutmeg Liver
Chronic hepatic congestion
What is this?
Describe how this happens.
Nutmeg Liver (RCHF)
Chronically there is low-grade Hypoxia & ↑ pressure of centrolobular hepatocytes leading to atrophy and necrosis
9 y/o female rottweiler with a history of tumor on one of its left limb toes. What is this associated with?
Local lymphatics are distended (lymphangiectasia) and filed with neoplastic cells.
Hemorrhage by Rhexis
Due to a substantial rent or tear in the vascular wall (or heart).
Hemorrhage by Diapedesis
Hemorrhage due to a small defect in the vessel wall or rbc‟s passing through the vessel wall in cases of inflammation or congestion (like in the lungs of animals with left-sided CHF…)
Hemoptysis
Coughing up of blood or blood- stained sputum from the lungs or airways.
Epistaxis
Bleedingfromthe nose.
Agonal Hemorrhages
Petechiae and ecchymoses associated with terminal hypoxia
Commonly seen in animals after slaughter.
Suffusive hemorrhage
Larger than ecchymosis and contiguous.
Paint-brush hemorrhage
Looks like if red paint was hastily applied with a paint brush. Most common on mucosal and serosal surfaces.
Describe the resolution of hemorrhage.
- Small amounts can be reabsorbed
- Larger amounts require phagocytosis and degradation by macrophages
- Organizing hematoma: Central mass of fibrin & red blood cells surrounded by supportive vascular connective tissue –> macrophages will eventually phagocytize this lesion.
- Hemoglobin (dark red blue color) –> enzymatically converted to bilirubin (blue-green color) and eventually into hemosiderin (gold-brown color)
Describe the vasoconstriction phase in normal hemostasis.
After initial injury a brief period of arteriolar vasoconstriction occurs mostly as a result of reflex neurogenic mechanisms and is augmented by the local secretion of factors such as endothelin (a potent endothelium-derived vasoconstrictor). The effect is transient, and bleeding would resume were it not for activation of the platelet and coagulation systems.
Describe primary hemostasis.
- Endothelial injury exposes highly thrombogenic subendothelial ECM, allowing platelets to adhere (via GpIb (glycoprotein lb) receptors to von Willebrand factor) and be activated
- Activation of platelets results in a dramatic shape change (small rounded → flat
plates with ↑surface area) and release of secretory granules [ADP and TXA2] lead to further platelet aggregation (via binding of fibrinogen to platelet GpIIb-IIIa receptors) to form the primary hemostatic plug. Within minutes the secreted products have recruited additional platelets (aggregation) to form a hemostatic plug; this is the process of primary hemostasis
Describe secondary hemostasis.
Tissue factor (factor III-thromboplastin) is also exposed at the site of injury.Tissue factor is a membrane-bound procoagulant glycoprotein synthesized by endothelium. It acts in conjunction with factor VII as the major in vivo pathway to activate the coagulation cascade, eventually culminating in thrombin (factor II) generation.Thrombin cleaves circulating fibrinogen into insoluble fibrin, creating a fibrin meshwork deposition (secondary hemostatic plug). Thrombin also induces further platelet recruitment and granule release. This secondary hemostasis sequence lasts longer than the initial platelet plug
Describe the thrombus and antithrombotic events that occur during hemostasis.
Polymerized fibrin and platelet aggregates form a solid permanent plug to prevent any additional hemorrhage. At this stage counter-regulatory mechanisms [e.g., tissue plasminogen activator, t-PA (fibrinolytic product) and thrombomodulin (interfering with the coagulation cascade)] are set into motion to limit the hemostatic plug to the site of injury.
Describe Virchow’s triad.
- Endothelial injury
- Alterations in blood flow (turbulence or stasis)
- Hypercoagulability: ↑in coagulation factors (or ↑sensitivity to) OR ↓ in coagulation inhibitors
What kind of disease is typically associated with pulmonary thrombosis? Why?
Seen in dogs with severe renal glomerular
disease –> protein losing nephropathy –> Significant loss of Antithrombin III, a major inhibitor of thrombin
Verminous thrombosis
Thrombus formation in the cranial mesenteric artery of horses with Strongylus vulgaris infection
Saddle thrombosis
Thrombus is located in the trifurcation of the abdominal aorta
“If pieces of a thrombus break off from the original mass and sail downstream to lodge at a distant site, that process is called ______. The mass that brakes off is called an ________.”
embolism
embolus
Fibrocartilaginous embolism in the spinal cord may result in ________.
Spinal cord infarcts.
Fat embolisms may be a complication of ________.
Long bone fractures
What is this condition known as? What can it lead to?
Hemopericardium–>leads to fatal cardiac tamponade.
What is this?
(Pig)
Dissecting aneurysm. Pig with Copper deficiency
What is a dissecting aneurysm?
Dissection of blood between and along the laminar planes of the media (blood- filled channel within the aortic wall) –> can result in rupture and fatal hemorrhage.
This condition is known as _______.
Hemarthrosis –blood within a joint space
What is the term for this kind of hemorrhage?
Petechia (pl. petechiae): up to 1-2 mm in size. Especially found on skin, mucosal and serosal surfaces
What is the term for this kind of hemorrhage?
Ecchymosis (pl, ecchymoses): Larger than petechia (up to ~1 or 2 cm). As seen in bruise (contusion) or small hematoma.
What kind of hemorrhage is this?
Agonal Hemorrhages: Petechiae and ecchymoses associated with terminal hypoxia
Commonly seen in animals after slaughter.
Describe the location of the thrombi in the pictures.
Left: mural thrombus, left ventricle
Right: Atrial thrombus
What is pictured? What kind of thrombosis is this?
Infectious thrombosis
Bacterial valvular endocarditis in cattle often involve the right AV valve and can give rise to septic emboli that will lodge in the pulmonary arteries –> inflammation/ abscess formation(embolicpneumonia)
What is pictured? What kind of thrombosis is this?
Infectious Thrombosis
Thrombotic Meningoencephalitis (TME), steer,
Etiology: Histophilus somni infection – results in vasculitis and thrombosis
What is this? Explain the pathophysiology.
(pig)
Venous infarction, small intestinal volvulus, pig. Note the intensely congested loops of small intestine undergoing early venous infarction. The twisting of the mesentery associated with the volvulus has resulted compression of the arteries and veins of the intestine. Because arterial pressure is higher than venous pressure, some blood can get into the gut but the compressed veins result in backing up and stagnation of blood in the gut.
What is this?
(Rabbit)
Acute pale infarcts, kidney. Multiple, pale white to tan pyramidal-shaped infarcts extend from the renal cortex to the medulla. The infarcts bulge above the capsular surface (center top), indicative of acute cell swelling.
