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30 Cards in this Set

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What are the (2) functional components of the circulatory system?
Blood vascular system
Lymph vascular system
The whole circulatory system has a common basic structure. It is a tube with:
An inner layer - tunica intima
A middle layer - tunica media
An outer layer -tunica adventia
Endothelial cells are simply a passive lining epithelium, ya?
NO
What is the tunica intima?
the innermost layer (lining the lumen) consists of a layer of specialized simple squamous epithelium called endothelium, which rests on a basement membrane and a layer of subendothelial connective tissue.

Arteries, unlike veins, possess a well defined internal elastic lamina which is a fenestrated sheet of elastin that demarcates the tunica intima from the next layer.
What is the tunica media?
this middle layer consists of circumferentially arranged smooth muscle and connective tissue, largely Types III and IV collagen and elastin.
What is the tunica adventitia?
the outermost layer, composed of connective tissue containing Type I collagen and elastin, blends into connective tissue components of the tissue being supplied (or drained) by the vessel. In larger vessels is characterized by the presence of small blood vessels (vasa vasorum)and nerves (nervi vasorum) supplying the outer region of the wall of the artery or vein.
In large arteries or veins, how is the external layer (tunica adventitia) perfused?
Via small blood vessels (vasa vasorum)and nerves (nervi vasorum)
What are elastic arteries?
such as the aorta and its major branches,are the largest arteries in the body. Their tunica intima is relatively thick due to abundant connective tissue in the subendothelial layer, and their tunica media is comprised of concentrically oriented elastic lamellae interspersed with smooth muscle cells and collagenous fibers. The elastic lamellae and other matrix components are products of the smooth muscle cells. The tunica adventitia consists of connective tissue and the vasa vasorum.
What are muscular arteries?
Muscular arteries deliver blood to specific body regions or organs, and are also called distributing arteries. The tunica intima of muscular arteries is characterized by a thin subendothelial layer and a very prominent internal elastic lamina. The tunica media is thick and consists of circularly arranged smooth muscle cells with prominent elastic lamellae or fibers. The tunica adventitia is unremarkable. Gap junctions between adjacent smooth muscle cells coordinate their contraction, enabling them to control the luminal diameter and thereby regulate local blood flow.
What are arterioles?
Arterioles are characterized by:
(a) their smaller diameter,
(b) a thin subendothelial layer,
(c) a barely discernible internal elastic lamina,
(d) a 5-8 cell thick tunica media and
(e) a thin tunica adventitia.

These vessels account for approximately 50% of the resistance to blood flow due to their narrow lumen and large numbers. Arteriole constriction increases resistance to outflow and, consequently, results in increased blood pressure in the large arteries that feed the arterioles, and in non-pulsatile flow downstream from the arterioles.
What is part of the microvasculature?
capillaries, venules, post-capillary venules
Substances cross the capillary wall by different mechanisms which depend on:
The nature of the endothelium
Hydrostatic vs osmotic pressures
The physicochemical properties of the substance in the blood and interstitial fluid.
What are the (3) types of capillary walls?
Continuous
Fenestrated
Discontinuous or sinusoidal
What is fenestrated capillary?
Complete basal lamina
Fenestrated endothelial lining
What is discontinous capillary?
Incomplete basal lamina
Fenestrated endothelial lining
The passage of substances across the capillary wall is dependent on:
Hydrostatic pressure differences
Osmotic pressure differences
Molecular size, etc.
Where do lymphatics start?
They are blind end in the periphary and are unidirectional
Are lymph caillaries larger or smaller than blood capillaries?
The lumen of lymph capillaries are much larger
What is a characteristic of lymph vessels that may help identifying during dissection?
Presence of valves to prevent backflow
How much of the systemic blood is located within the veins?
~70%
What are the capacitance vessels and why are they called that?
Veins are the capacitance vessels and they are called that due to their ability to distend without changing the pressure substantially
For purposes of comparison and identification of veins vs accompanying arteries, the veins generally exhibit:
(a) a larger and more irregular lumen,
(b) a smaller smooth muscle cell/collagen fiber ratio,
(c) the absence of distinct elastic laminae,
(d) a thicker adventitia than media and
(e) valves.
What are some characteristics of large veins?
Large veins are characterized by a thin intima and media, but a thick adventitia. The media contains mostly connective tissue and a few smooth muscle cells. The adventitia may include occasional longitudinally oriented bundles of smooth muscle cells.
What are some characteristics of medium and small veins?
Medium and small veins exhibit similar morphologies, but the intima may be relatively thick in comparison to other vessels. The media is thin and has a few layers of smooth muscle cells in a network of elastic lamellae and a thick adventitia.
What are some characteristics of venules?
Venules (sometimes called muscular venules) possess an intima of endothelium and basal lamina only, a media with a few muscle cells and a substantial adventitia. The smallest venules, the post-capillary venules constitute part of the microvasculature and will be considered with the capillaries.
With what tissue are venous valves formed?
Backflow is prevented by valves formed by flaps of endothelium with their underlying basal lamina.
What are the (3) layers of the heart wall?
The endocardium - A simple squamous layer of endothelium that rests on a relatively thin layer of connective tissue. The endocardium also lines the valves of the heart.

The myocardium - Cardiac muscle cells and their blood supply.

The epicardium - Connective tissue which contains numerous adipose cells, coronary vessels, and a simple squamous layer of mesothelium (visceral layer of the pericardium).
What are the components of the electrical conduction system of the heart?
The sinoatrial (SA) node is a located beneath the epicardium in the medial wall of the right atrium near the opening of the superior vena cava.

The atrioventricular (AV) node is located in the atrioventricular septum.

The bundle of His and the right and left bundle branches of His pass from the AV node through the interventricular septum.

Purkinje fibers are branch from the bundle of His into the subendocardium, transmitting impulses to the rest of the myocardium.
Describe endothelium:
Endothelium is very thin, a single layer of squamous epithelium, and the luminal surfaces of these cells are non-thrombogenic, i.e. will not initiate formation of a blood clot, whereas the underlying connective tissue will.
What are some functions of endothelium?
It plays a role in the regulation of blood pressure through the formation of vasoactive substances, e.g. conversion of angiotensin I to angiotensin II by angiotensin-converting enzyme, and the synthesis and release on endothelially-derived constricting (endothelin) and relaxing (nitric oxide) factors
It synthesizes pro-coagulant factors (von Willebrand factor) and anticoagulant factors (prostacyclin)
It plays a major role in the inflammatory response. For example, endothelial cell surface proteins function as receptors (endothelial-leukocyte adhesion molecule, ELAM, or E selectin) for binding of leukocytes and the initiation of diapedesis at sites of inflammation.