Vascular Disorders and Thrombosis: Anatomy/Microanatomy

Lecture 7

What is the main function of the circulatory system?

to deliver nutrients and remove waste products from cells

The circulatory system is composed of what?

• blood

• central pump and driving force to distribute blood through system (heart)

• vascular network

Are arteries under high pressure or low pressure?

high

Are veins under high pressure or low pressure?

low

Do arteries or veins move blood toward the heart?

veins

Do arteries or veins move blood away from the heart?

arteries

What is the purpose of the vascular network?

exchanges nutrients and waste

What is responsible for draining the extracellular space?

lymphatic vessels

Lymphatic vessels parallel the veins and empty back into the blood via what?

the thoracic duct

Why do arteries have large diameter lumens?

to facilitate rapid blood flow

The walls of arteries are predominantly made up of what?

smooth muscle for tensile strength and elastin fibers for elasticity

Why do arterioles have narrower lumens?

because their main functions is to provide resistance

How do arterioles combat the pressure drop as blood moves further from the heart?

by having a thick layer of smooth muscle within the wall that constricts based on stimulation

What are the three distinct layers that make up vessels?

• tunica intima

• tunica media

• tunica adventitia

Which vessel layer is made up of a single layer of endothelial cells around the lumen, is adhered to the basement membrane, contains elastin, and is the internal elastic lamina?

tunica intima

Which vessel layer is made up of smooth muscle, elastin, collagen, is reticular, and is known as the external elastic lamina?

tunica media

Which vessel layer is made up of connective tissue, has micro vessels known as the vasa vasorum, contains lymphatic vessels, and nerve fibers?

tunica adventitia

What are the sites of nutrient waste/product exchange between blood and the surrounding tissue?

capillaries

What is the most numerous vessel of the circulatory system but only contains 5% of the total blood volume at one time?

capillaries

Is the velocity of blood thorugh capillaries fast or slow?

slow

The slow speed and small laminate of capillaries allows for what?

time for exhange of nutrients and waste

In most cases, there is no more than how much space between a capillary and a cell?

1mm

What are the three types of capillaries?

• continuous

• fenestrated

• discontinuous

The brain only has what type of capillaries?

continuous

Continuous capillaries have a _____ endothelium and _____ basement membrane.

continuous, continuous

The continuous endothelium and continuous basement membrane of continuous capillaries allows for the passage and exchange of what?

passage of only small molecules and the exchange of oxygen and carbon dioxide

Continuous capillaries are present in which tissues?

those that don’t require or necessarily want the exchange of larger products such as the brain, lung, muscle, and bone

Fenestrated capillaries have _____ endothelium and _____ basement membrane.

discontinuous, continuous

The discontinuous endothelium and continuous basement membrane of fenestrated capillaries allows for the exchange of and keeping in what?

exchange of slightly larger products and keeping in negatively charged items such as protein (albumin)

The basement membrane of fenestrated capillaries has what charge?

negative charge

Fenestrated capillaries are found where?

• renal glomeruli (kidney)

• intestinal villi

• endocrine glands

• choroid plexus

• ciliary body of the eye

Discontinuous capillaries have _____ endothelium and ____ basement membrane.

discontinuous, discontinuous

The discontinuous endothelium and discontinuous basement membrane of discontinuous capillaries allows for what?

maximum passage of molecules from the vascular lumen into the extracellular space

Discontinuous capillaries are found where?

in tissues involved in:

• filtration —> liver

• removal and clearance —> liver and spleen

• surveillance —> lymph nodes and spleen

• hematopoiesis —> bone marrow

Discontinuous capillaries are also known as what?

sinusoids

Post capillary venules have a composition similar to capillaries but will develop thin layers of smooth muscle where?

the further away from the capillary they are

Veins are larger vessels which are composed predominantly of what?

collagen with little smooth muscle and elastin

Veins contain valves to prevent what and why?

prevent backflow of blood because pressure within the vein is relatively low

Veins will contract the little skeletal muscle they have to help with movement of blood, but other factors facilitate movement of blood within a vein like?

• skeletal muscle contraction

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

Veins and venuoles can hold up to what percent of total blood volume?

65%

What type of stain highlights the elastin in vessels?

Verhoff’s

Lymphatic vessels have what to allow for passage of large molecules into their lumen?

overlapping endothelial cells with large interendothelial gaps

What acts as a valve in a lymphatic vessel to close the interendothelial gaps and prevent escape of the flow of lymph from the lumen?

the pressure within the lumen of the lymphatic vessel

What is the drainage path for lymphatic vessels?

lymphatic vessels —> larger lymphatic vessels —> pass through lymph nodes —> thoracic duct —> vena cava

Are lymph nodes a high pressure or low pressure system?

low

What forms a dynamic interface between the blood and tissue and serves many roles, including fluid distribution, inflammation, immunity, aniogenesis, and hemostasis?

endothelium

Normal endothelium is what?

antithrombotic and profibrinolytic

Define fibrinolytic.

helps break down the complexing of fibrinogen into fibrin

Define antithrombotic.

helps to regulate hemostasis and prevent clot formation

What are the five main functions of the endothelium?

• fluid distribution

• inflammation

• immunity

• angiogenesis

• hemostasis

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

rete mirabile

What is the function of rete mirabile?

function as countercurrent exchangers for regulating temperature, ionic concentration gradients, O2/CO2 exchange, and equalizing blood pressure

Where can you find rete mirabile?

around the right and left internal carotid arteries as they pass by the pituitary gland as well as along the cranial floor

What is the most well known rete mirabile?

rete mirabile cerebri of ruminants

What is the space between parenchymal and stromal cells and microcirculation?

interstitium (extravascular compartment)

What are the functions of the interstitium?

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

• module systematic physiologic properties exerted by parenchymal cells

• genereal fluid pool/reservoir providing cushing (shock absorption) offects for organs, water/ion reserve

• structural framework for cell survival

What is the structural, adhesive, and absorptive components within the intertitium?

extracellular matrix

The extracellular matrix is composed of what?

• type I collagen

• glycoproteins

• glycosaminoglycans

• proteoglycans

What component provides the structural framework for the extracellular matrix?

type I collagen

What component provides sites of attachment for the structural proteins as well as a site of adhesion for transmigrating leukocytes within the extracellular matrix?

glycoproteins

What are the absorptive disaccharide complexes in the extracellular matrix?

glycosaminoglycans

What is the hydrophilic component of the extracellular matrix that can bind large amounts of water and other solumen molecules?

proteoglycans

Components of the extracellular amtrix are produced by what?

• parenchymal cells

• fibroblasts

• glial cells (CNS only)

• macrophages

• trafficking leukocytes