Lecture 7: Vascular Disorders & Thrombosis

Anatomy/Microanatomy

Which vessel has a large lumen with minimal resistance and thick vessel walls?

arteries

What are the components of thick artery walls and what function do they provide?

smooth muscle and elastic fibers allow vessels to recoil easily

What vessel narrows the lumen and responds to sympathetic and parasympathetic innervation?

arterioles

Since arterioles are further away from the heart, pressure drops. How do arterioles combat this to distribute blood?

thick layer of smooth muscle that constricts and dilates based on sympathetic/parasympathetic stimulation

What are the three distinct layers of vessels from internal to external?

1. tunica intima

2. tunica media

3. tunica adventitia

What vessel layer contains endothelial cells, a basement membrane, and internal elastic lamina?

tunica intima

What vessel layer contains smooth muscle, collagen, reticular, and elastin fibers, and external elastic lamina?

tunica media

What vessel layer contains connective tissue, microvessels to supply blood to the vessel, lymphatic vessels, and nerve fibers?

tunica adventitia

What vessel runs very close to tissue to exchange nutrients and waste?

capillaries

What are the three types of capillaries?

1. continuous

2. fenestrated

3. discontinuous

Capillary lumina are so small that RBCs move through in single file and velocity of blood flow is slow. How is this advantageous?

more time for exchange of nutrients and waste

What type of capillary has a continuous basement membrane and continuous endothelium?

continuous

What is the only type of capillary used by the brain?

continuous capillaries

What is a allowed to pass through continuous capillaries?

oxygen and carbon dioxide exchange and small molecules

What type of capillary has a discontinuous endothelium with a continuous basement membrane?

fenestrated

How does the basement membrane aid in keeping certain products within the lumen of capillaries?

it is negatively charged and repels negatively charged molecules such as proteins (albumin)

Where are fenestrated capillaries found?

• renal glomeruli

• intestinal villi

• endocrine glands

• choroid plexuses

• ciliary processes of the eye

What type of capillary has discontinuous endothelium and basement membrane?

discontinuous

What type of capillary is found in tissues involved in immune surveillance and detox?

discontinuous

Where are discontinuous capillaries found?

• liver sinusoids

• spleen sinusoids

• bone marrow

• lymph nodes

Veins have little smooth muscle and elastin; they are instead made mostly of ______.

collagen

Why do veins have one way valves?

they are low pressure, the one way valves allow blood to flow back to the heart

What is blood passage in veins and venuoles dependent on?

• valves to prevent backflow

• contraction of skeletal muscles

• increased pressure gradient due to increased pressure in heart (cardiac suction effect)

Since the vein tunica media is predominantly collagen and not smooth muscle, what has little effect on veins?

sympathetic and parasympathetic effects

What is the function of the lymphatic system?

pick up extra fluid that leaks into interstitial space and return it to blood

What vessels have overlapping endothelial cells with large interendothelial gaps that allow for passage of large molecules into their lumen?

lymphatic vessels

How do lymphatic vessels begin?

as blind ended lymphatic capillaries

What function does the pressure within the lumen of a lymphatic vessel have?

acts as a valve closing the interendothelial gaps and preventing escape of the flow of lymph from the lumen

Describe the pathway of lymph through the body.

• lymphatic vessels

• larger lymphatic vessels

• lymph nodes

• thoracic duct

• vena cava

• lymph returned to circulation

True or false: lymph vessels have strong contractions that push their own fluid throughout the body.

false: they are distensible and a low pressure system like veins, therefore requiring valves and contraction of skeletal muscle

What lines all components of the circulatory system and forms a dynamic interface between the blood and tissue and serves many roles?

endothelium

What are the functions of endothelium?

• fluid distribution

• inflammation

• immunity

• angiogenesis

• hemostasis

True or false: normal endothelium is antithrombotic (regulate hemostasis and prevent clot formation) and profibrinolytic (helps break down the complexing of fibrinogen into fibrin)

true

What is the rete mirabile?

specialized vascular networks formed by arterial blood vessels through the center of large venous sinuses

What is the function of the rete mirabile?

functions as counter current exchangers:

• regulating temperature

• ionic contraction gradients

• O2/CO2 exchange

• equalizes blood pressure

Where is most of the body’s water?

in cells

What is the interstitium?

the space between parenchymal and stromal cells and microcirulation

What are the functions of the interstitium?

• provide pathways used by microvasculature, lymphatic vessels, nerves, and trafficking leukocytes

• module systematic physiologic properties exerted by parenchymal cells

• general fluid pool/reservoir providing cushioning effects for organ, water/ion reserves

• structural framework for cell survival

What is the extracellular matrix?

the structural, adhesive, and absorptive components within the interstitium

What provides the structural framework for the extracellular matrix?

type I collagen

What is the extracellular matrix predominantly composed of?

• type I collagen

• glycoproteins

• glycosaminoglycans

• proteoglycans

What provides sites of attachment for the structural proteins as well as site of adhesion for transmigrating leukocytes in the ECM?

glycoproteins

What hydrophilic molecule binds large amounts of water and other solumen molecules in the ECM?

proteoglycans