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Flashcards in Blood Vessels Deck (25)
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Compare and contrast epicardium and endocardium (Homology, Lining, Composition)

Endocardium is homologous to the intima.
Epicardium is homologous to the adventitia

Endocardium lines the atria and ventricles
Epicardium is the visceral layer of the pericardium: it is the surface of the heart.

Endocardium is composed of endothelium and a subendothelium layer of connective tissue.
Epicardium is composed of mesothelium and connective tissue containing neurons, adipose tissue, and coronary blood vessels.


what is myocardium?

The thickest layer of the heart composed of muscle. It is homologous to the media of blood vessels.


What is the physiological significance of the # of elastic intima in the aorta?

The elasticity produces a more uniform and laminar flow


Which arteries are LARGE elastic?

aorta and its branches: common carotid , subclavian, brachiocephalic, pulmonary arteries


Desribe: How to distinguish an elastic artery from a mixed artery

Elastic Artery: Tunica Intima (150microns thick), Media (2millimeters thick), Adventitia (thin) differ in width
Mixed Artery: Tunica Media and Adventitia have same width (thin).

Elastic Artery: Tunica Media has 40-70 layers of fenestrated elastic lamallae with smooth muscle cells in alternate layers. Inconspicous IEL. Thin EEL present with 1/2way penetration of vaso vasorum of adventitia. Adventitia contians nerve fibers, lymphatics, and vasa vasorum in loose connective tissue
Mixed Artery: Fewer elastic lamellae and obvious IEL. .


EEL _______ in smaller diameter arterial vessels.

gets thinner and disappears


Describe the Tunica Intima

consists of endothelium, basal lamina, subendothelium layer of connective tissue. It may contain an occasional smooth muscle cell.

In arteries, the intima is separated from the media by an IEL (external component of the intima)


Describe the Tunica Media

Composed of smooth muscle. elastic fibers, elastic lamellae, proteoglycans, glycoproteins and reticular fibers(collagen type III).

*Controls Blood Pressure and movement


Describe the Tunic Adventitia

Outermost layer composed of fibroblasts, Type I collagen (longitudinal oriented), and elastic fibers. Larger blood vessels have vasa vasorum.

*Provides physical support, connects vessels to tissues, carries vessels and nerves


Define Vasa vasorum

vessels of the vessel that provides nutrients via small vessels to the vessel wall. (more extensive in veins)


Define IEL

Internal Elastic Lamina borders the media and is a fenestrated layer of elastin. Fenestrae allow the diffusion of substances to nourish cells deep in the vessel wall.


Define EEL

External Elastic Lamina is seen in larger blood vessels and borders the media, separating it from the adventitia.


Describe the arteriole characteristics

Diameter is ~ 100 microns and invisible to naked eye
Arteriole Tunica Intima. Larger Arterioles have IEL. A thin subendothelial layer of reticular fibers is present.
Arteriole Tunica Media: have 1-3 layers of muscles or 1-5.
Arteriole Adventitia has loose connective tissue only- moderate to scant


What is a metaarteriole?

Formed by the terminal end of a capillary bend. It is a shunt between venule and arterioles. It has also a precapillary sphincter that regulates blood flow into capillaries


What are the three main types of capillaries?

1. Fenestrated
2. Continuous
3. Sinusoidal


Describe Continuous capillaries.

They are the most common and least permeable capillaries and are found in muscle, nervous, and connective tissues, and the exocrine pancreas.
They have a complete endothelial lining and basal lamina.
The endothelial cells are sealed by tight junctions and the cytoplasm has many vesicles that transport large molecules.


Describe Fenestrated capillaries.

They are found in the pancreas, intestines, and endocrine glands. (A special type with no diaphragms are found in renal glomerulus)

They have a continuous, but thin endothelium and basal lamina. Fenestrae of 60-80 nm are covered by a diaphragm and allow rapid interchange of substance between blood and tissue.


Describe Sinusoids

Sinusoidal capillaries are irregular blood channels found in endocrine glands, liver, bone marrow (sdiscontinous) , spleens

They have continuous basal lamina and larger fenestrae with diaphragms.

Discontinuous sinusoids have a discontinuous or absent basal lamina and large gaps between endothelial cells prompting exchange.


List 6 ways to distinguish a vein from an artery

1. veins vary more in size and structure
2. veins ar elarger ( hold 70% blood volume)
3. Veins have more extensive vasa vasorum and lymphatics
4. Thickess of veins mostly are due to adventitia
5. Veins have more collaen, less elsatic and less smooth muscle
6. small/medium veins have valves from infolded tunica intima some with IEL


What is a portal system?

A vascular specialization that carries blood from one capillary bed to another


What is a AV Anastamose?

A vascular Specialization in which there is a direct connection from an arteriole to a venule.


What feature of the lymphatic capillary strucutre is important for their physiological function?

1. Large Lumens
2. Thin walls
3. Irregular Shape
4. Run parallel to bloood capillaries and veins.


What is the function of lymph?

1. Help transport lymphocytes
2. collect lymph from extracellular space and return it to blood vascular system.


What is a Weibel-Palade body?

It is a granule in the endothelial cell that stores von-Willebrand factor (unvolved in blood coagulation) and P-selectin (recruits leukocytes in inflammation)


What are Mixed, Musculo-Elastic Artery?

Transitional segments between large and medium arteries