- Formed by a single layer of flattened epithelial cells, the mesothelium, supported by connective tissue including fat. - A similar mesothelial layer lines the opposing parietal surface of the pericardial sac

- Triangular mass of fibrous connective tissue - Connects the aortic arterial ring and the left and right atrioventricular ring.

Lecture 16: Histology of the Cardiovascular System Flashcards by Allison Brown

4 Functions of the cardiovascular system

Maintenance of adequate blood flow (cardiac output)
Delivery of oxygen, nutrients, hormones, electrolytes, and water to peripheral tissues
Removal of CO2 and other metabolic waste products
Maintenance of normal thermoregulation and glomerular filtration rate -> urine output

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Normal vascular pattern

Artery - arteriole - metarteriole - capillaries - venule - vein

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Endocardium

Endothelial lining of the heart chamber surface. Also covers the surface of valves. The subendocardium contains a thin layer of connective tissue.

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Where are purkinje fibers found?

.Subendocardium

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Myocardium

Cardiac muscle mass

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Epicardium

Formed by a single layer of flattened epithelial cells, the mesothelium, supported by connective tissue including fat.
A similar mesothelial layer lines the opposing parietal surface of the pericardial sac

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What lubricates the movement of the epicardium on the opposite parietal pericardium?

Mesothelial cells

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The epicardium represents what layer of the pericardial sac?

Visceral

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What is cardiac muscle called?

Mycardium

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Is myocardium cross-striated?

Yes

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Nucleus of myocardium

Single, centrally located

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The intercalated discs of myocardium

gap junctions

- anchoring junctions

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Myocardium contains what pigment

lipofuscin

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Mitochondria in myocardium?

Yes, many.

Up to 20% cell volume

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Because there are a lot of mitochondria in myocardium,

it requires a lot of O2

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Epicardium is contiguous with the endocardium at the level of the

endocardial cushion

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The cardiac skeleton consists of

4 bands of fibrous connective tissue that encircles the base of the pulmonary trunk, aorta, and AV valves

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Purpose of the cardiac skeleton

Provides structural support to the heart

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Fibrous trigon

Triangular mass of fibrous connective tissue

- Connects the aortic arterial ring and the left and right atrioventricular ring.

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Differentiation of the fibrous trigon

Osseous differentiation and forms the Os Cordis, which is primarily seen in cattle

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Three tunics of vessels

Tunica intima
Tunica media
Tunica adventitia/externa

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Tunica intima of vessels

Innermost

- Endothelium, internal elastic membrane, subendothelial connective tissue

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Tunica media of vessels

Middle

- Smooth muscle and elastic lamellae/fibers

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Tunica adventitia of vessels

Outermost

- CT, principally collagen, may contain blood vessels, nerves, capillaries

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Vascular endothelium role in hemostasis

- Anti-thrombotic and pro-fibrinolytic in the normal state | - Pro-thrombotic and anti-fibrinolytic during injury

Vascular endothelium role in modulating perfusion

- Nitric oxide relaxes and causes vasodilation | - Endothelin causes vasoconstriction

Vascular endothelium role in inflammation

- Regulates the traffic of inflammatory cells - Produces pro-inflammatory cytokines - Control angiogenesis and tissue repair

Hemostasis

Arrest bleeding by the physiological properties of vasoconstriction and coagulation or by surgical means

Does the elastic artery have all three tunics?

Yes

Best example of an elastic artery

Aorta

Tunica media of elastic artery

Consists largely of repeating elastic lamellae

Tunica intima of elastic artery

Endothelium + loose CT

Tunica adventitia of elastic artery

Contains vasa vasorum to assist in supplying nutritional needs to thick tuncia media

In muscular arteries, tunica media is primarily

Smooth muscle

Thickest Tunica in muscular arteries is

tunica media

In cross section, muscular arteries generally have what appearance?

round

Muscular arteries generally have a prominant

internal elastic membrane

What is an example of muscular artery?

Femoral artery

In vascular smooth muscle, the cells are arranged

Circumferentially within the tuncia media

Vascular smooth muscle regulates

Diameter and tone (vasodilation/vasoconstriction)

Arterioles have how many layers of smooth muscle?

1-3

What has the greatest effect of blood pressure?

Arterioles

Arteriole nuclei

bulge into thelumen

Appearance of arteriole

Round

Do arterioles have an internal elastic membrane

Not if they are the smallest ones with 1 smooth muscle cell

Metarteriole

Terminal vessel | Has precapillary sphincters that can regulate flow to capillary bed

Pericytes are also called

rouget cells

Pericytes

Mesenchymal-like contractile cells that wrap around capillaries and venules to communicate with endothelial cells by physical contact and paracrine signaling

Pericytes have actin, myosin, tropomyosin?

Yes

Do pericytes have their own basal membrane?

Yes

Pericytes proliferate after

- Injury - May be replacement stem cell source - Important in angiogenesis (new vessel formation)

Capillaries

Thin walled tubes of mesenchymal origin

Capillaries in a cross section

Made of only one endothelial cell rolled into the tube

Capillaries represent

The site of exchange between blood and surrounding tissue

Capillary size

Diameter - 1-9 micro | Length - 0.25-1mm

Capillaries can be longer in

adrenal cortex, kidney medulla

Three classifications of capillaries

1. Continuous 2. Fenestrated 3. Discontinuous

What is the most common capillary

Continuous

Where are continuous capillaries found?

Muscle, brain, bone, lung | Blood-brain barrier and blood-testes barrier

Fenestrated capillaries

In tissues with substantial fluid exchange

Fenestrated capillaries are found

Intestinal villi, choroid plexus, ciliary process, glomerular capillaries

Discontinuous capillaries are found

In hepatic and splenic sinuses -> large molecules can exit (ex. RBC in spleen)

What is responsible for the filtration of plasma?

Renal glomerulus

Sinusoids are also called

discontinued or sinusoidal capillaries

Venules are called

Postcapillary vessels

Venules are very _____ vessels

Leaky

Do venules have smooth muscle?

Nope

What is possible in venules

Leukocyte diapedesis

Pressure in venules

5mm Hg

Veins compared to arteries

Large, wide lumen and thin walls

Are valves present in veins?

Yes

Tunica media in veins

thin

What is the thickest tunica in veins

Tunica adventitia

Vasa vasorum is present in what kinds of veins

large

Veins may be collapsed in

histological sections

Lymphatic vessels

Very thin wall, very low pressure, may contain valves

Why do lymphatic vessels appear clear?

No RBC in lymph