Cardiovascular pathology 4 Flashcards
The vascular system is divided into which 4 components?
- Arterial
- Capillary
- Venous
- Lymphatic
Describe the features of arteries
- Largest = elastic arteries
- Muscular arteries: fewer layers of smooth muscle cells without elastic laminae
Describe the 3 layers of elastic arteries and the components of each
- Tunica intima: inner endothelial layer over a basal lamina and subendothelial connective tissue
- Tunica media: thick, fenestrated, elastic laminae, smooth muscle cells and ground substance
- Tunica adventitia: collagen, elastic fibres and connective tissue with blood vessels (outer layer)
Describe the features of capillaries
- 5-10mm diameter
- Continuous epithelium
- Fenestrated
Describe the features of veins
Thinner walled than arteries
Adventitia is the thickest layer
Valves to prevent retrograde blood flow
What is an aneurysm?
- Localized dilation of a thinned and weakened portion of a vessel.
- Usually arteries affected (large elastic arteries), but can occur in veins
Which deficiency in pigs can lead to aneurysms?
Copper deficiency
- copper is necessary for the development of elastic tissue
What are usually the consequence of aneurysms?
Rupture => fatal
Give 2 examples as to why vessels would rupture?
Horses - sudden rupture of ascending aorta due to trauma to ventral thorax from fall
Cattle - rupture of the middle uterine artery may occur during parturition, uterine torsion or prolapse
What causes arterial hypertrophy?
Sustained increased in pressure of volume loads?
Which vessel is most affected by arterial hypertrophy?
Muscular arteries are mainly affected with hypertrophy of smooth muscle of the tunica media
Give 3 examples of arterial hypertrophy
Cats - pulmonary arteries in parasitic infections e.g. Toxocara spp, Dirofilaria immitis
Cows - Pulmonary arteries, hypoxia induced vasoconstriction and pulmonary hypertension from exposure to high altitude
All - CV abnormalities that shunt blood left to right lead to pulmonary hypertension and hypertrophy
Arterial medial calcification is associated with?
Concurrent endocardial mineralisation and fibrosis
Arterial medial calcification could be seen with which conditions?
- Vitamin D toxicosis
- Renal insufficiency
- Johne’s disease
- Calcinogenic plant toxicosis
How does arterial medial calcification appear grossly?
Solid, dense, pipelike structures with raised, solid, white, intimal plaques.
How does arterial medial calcification appear histologically?
Prominent basophilic, granular mineral deposits occasionally admixed with iron (siderocalcinosis).
What is a normal finding in the subendothelium of muscular arteries and arterioles of horses?
Arterial intimal calcification
Describe fibrinoid necrosis
Deposits of an amorphous, homogeneous, eosinophilic protein material composed of serum proteins and fibrinogen.
Describe the pathogenesis of fibrinoid necrosis
Endothelial and muscular damage of the arterial wall with extravasation of proteins and deposition in the vessel wall.
The smooth muscle of the tunica media has been replaced by an amorphous to fibiliary eosinophilic protein
Give 2 examples of when you’d see fibrinoid necrosis
Pigs - vitamin E deficiency
Dogs - uraemia
What are 3 predisposing factors for thrombosis
- Endothelial damage/injury
- Turbulence or stasis of blood
- Hypercoagulative states
What is a saddle thrombosis?
a blood clot (called a “thrombus”) that lodges at the base of the aorta just as it branches into two distinct arteries
Describe disseminated intravascular coagulation
Clotting phenomenon due to endothelial damage with exposure of subendothelial collagen and subsequent platelet aggregation and intravascular activation of the coagulation process
Give example causes of DIC
- Endotoxaemias
- Viraemias
- Dirofilariasis
- Tumours
- Shock
- Extensive necrosis
What can be seen microscopically in DIC?
Numerous fibrin thrombi in arterioles and capillaries causing occlusion
What are the consequences of DIC?
Extensive clotting depletes coagulation factors, resulting in widespread haemorrhages.
What is an embolism?
Oclussion of arteries by lodgement of foreign materials such as disrupted fragments of thrombi, neoplastic cells or bacteria.
What are septic embolisms?
Originate from lesions of vegetative endocarditis in the lung (right side) or the myocardium, kidneys, spleen, joints, leptomeninges (left side).
Give 3 examples of possible occlusion causes of arteries (embolisms)
- Parasites: fragments of dead intravascular parasites, such dirofilaria, into the pulmonary circulation of carnivores following administration of adulticidal drugs
- Fat: due to bone fractures
- Fibrocartilaginous: Due to movement within the spinal vasculature of fibrocartilaginous fragments from degenerated intervertebral disks leading to infarction of the spinal cord
What are 4 causes of vasculitis?
- Haematogenous dissemination of infectious organisms
- Local extension of suppurative inflammatory processes
- Immunomediated processes
- Parasitic infections
What are the names of inflammation of the arteries and veins?
Arteries = arteritis Veins = phlebitis
How does vasculitis appear grossly?
Medium-sized arteries appear thick and tortuous, with associated haemorrhages, aneurysms and thrombosis
How does vasculitis appear microscopically?
- Fibrinoid necrosis and inflammation of the intima and media.
- Leukocytes present within and surrounding walls; damage to vessel as fibrinoid necrosis.
- Endothelial damage causes thrombosis leading to infarction.
Give some examples of viral causes of vasculitis
- Bluetongue of sheep
- Equine viral arteritis
- Malignant Catarrhal Fever
- Equine Infectious Anemia
- Feline infectious peritonitis
Describe bluetongue induced vasculitis
- polyarteritis centred around the intima
- haemorrhage at the origin of the pulmonary artery
Describe equine viral arteritis induced vasculitis
- Polyarteritis affecting the media and adventitia
- Widespread petechiae haemorrhages
- Subcutaneous oedema
- Hydrothorax
- Hydroperitoneum
- Hydropericardium
Give 2 parasitic causes of vasculitis
- Dirofilaria immitis in the dog
- Strongylus vulgaris in the horse
How does dirofilaria immitis cause vasculitis?
- Adult worms live in the pulmonary arteries of dogs.
- Microfilaria are found throughout the circulation.
- Cause villous pulmonary endoarteritis (inflammation of the intima) and obstruction and narrowing of the lumina
- Chronic = villous hyperplasia of the tunica intima – narrowing of the vessel
How does strongylus vulgaris cause a vasculitis?
- 4th stage larvae in mesenteric arteries.
- Causes intense focal inflammatory reaction in the walls of the larger arteries
- Aneurysmal dilation
- Thrombosis
- Infarction distal to involved site
What is polyarteritis nodosa?
Multifocal chronic proliferating and necrotizing mesenteric arteritis with aneurysm in rats
Inflammation of veins is termed?
Phlebitis
What are the possible causes of phlebitis?
- Systemic infections (vasculitis): Salmonellosis, collibacilosis, FIP.
- Local infections: Metritis, hepatic abscesses.
- Intravenous injection sites
What is the name given to inflammation of the umbilical vein?
Omphalophlebitis
What could be the cause of vascular damage and development of phlebitis and thrombosis jugular vein (horses)
IV injections of irritant solutions or intimal trauma produced by intravenous catheters
What is a haemangioma?
Vascular tumour
Describe a haemangioma
- Well-circumscribed benign tumours of well-differentiated endothelial cells forming vascular channels in dermis or subcutis
- Variably sized vascular spaces filled with erythrocytes and lined by a single layer of uniform endothelial cells.
What is a haemangiosarcoma?
Malignant neoplasm of endothelium
Describe the gross and histological appearance of a haemangiosarcoma
Gross: large, red (haemorrhagic) nodular masses
Histologically: irregular vascular clefts, channels, atypical cells, high mitotic rate, usual signs of malignancy
What is a haemangiopericytoma?
Occurring exclusively in dogs, solitary, multilobulated masses occurring around the joints of limbs.
- White and firm
- Vascular wall tumours
How does a haemangiopericytoma appear histologically?
Perivascular whorls of fusiform cells.
Low metastatic potential.
