Flashcards in Cardiovascular Histology Deck (60)
What are the three layers of the heart wall in all chambers?
What is the epicardium?
It is the visceral layer of the pericardium
What is the myocardium?
the principle cardiac muscle layer of the heart
What is the endocardium? What does it contain?
most internal layer of the heart wall containing Purjinke fibers and nuclei
What are the layers/contents of the epicardium?
a layer of mesothelial cells
autonomic nerve tissue
the sarcoplasm of cardiac muscle in the middle myocardium usually contains what?
What are the contents of the endocardium?
1) endothelium and its supporting CT
2) a middle myoelastic layer of smooth muscle fibers and CT
3) deep layer of CT called the subendocardial layer
4) Purjinke fibers,
In what part of the heart does the endothelium contain a thick layer of Purjinke fibers?
Which are larger, Purjinke fibers or cardiac muscle fibers?
Purjinke fibers (their nuclei are also larger)
The nucleus of Purjinke fibers are rich in what substance?
A vein or arteriole situated in between two capillary beds is called what?
a portal system (e.g. the hepatic portal system)
walls of arteries and veins consist of ___ layers called ____
What are the names of the tunics of vein and arteries from innermost to outermost?
1) tunica intima
2) tunica media
3) tunica adventitia
What does the tunica intima consist of?
1) endothelium and a basement basement of the endothelium and
2) a sub endothelial layer with CT and internal elastic lamina
What does the tunica media consist of?
1) circularly arranged layers of smooth muscle cells
2) elastic and collagen fibers
3) sometimes an external elastic membrane
What does the tunica adventitia consist of?
outermost CT layer
has external elastic lamina adjacent to tunica media, and has vasa vasorum and nervi vasorum (aka nervi vascularis)
What is a vasa vasorum?
a system of vessels found in large arteries and veins that provide blood supply to tunica adventitia and media
Tunica intima and part of tunica media are supplied by the vessel
What is the role of nervi vascularis?
they are a network of autonomic nerves that control vessel diameter
How do nervi vascularis control vessel diameter?
they cause contraction and relaxation of the smooth muscle in the T. media layer of the vessel
How can the tunica intima cause vasodilation?
the endothelium cells of the layer release endothelial derived relaxing factor
What are the roles of endothelial cells in vessels (5 things)?
• Play an important role in blood homeostasis
• Maintain selective permeability barrier
• Maintain nonthrombogenic barrier between blood platelets and sub endothelial tissue
• Modulate blood flow and vascular resistance
• Modification of lipoproteins by oxidation
What are the roles of smooth muscle cells in vessels (2 things)?
1) contraction/relaxation modulated BP
2) synthesize elastic fibers, reticular fibers, and proteoglycans
What are the three types of vessels?
1) large (elastic)
2) median (muscular)
3) small arteries (arterioles)
What is the only elastic artery?
What are some distinguishing features of elastic arteries?
Note that the only elastic artery is the aorta
1) T. media layer is thicker than adventitia
2) T. media layer has multiple sheets of elastic lamellae
3) T. intima, subendothelial layer is relatively thick, contains collagen and elastic fibers
4) T media and adventitia contain collagen fibers that prevents excessive distention of the large arteries
What are some distinguishing features of muscular arteries?
• Subendothelial layer is thin
• **Prominent internal and external elastic laminas**
• More smooth muscle and little elastic material in T media compared to large artery
• T. adventitia is about the same thickness as T Media
T or F. T. media in muscular arteries contain little elastic fibers.
T. They are primarily smooth muscle cells and collagen
What is the t. adventitia composed of in muscular arteries?
What are some distinguishing features of small arteries (arterioles)?
• Arterioles have only 1-5 layers of smooth muscle in T Media.
• Internal elastic lamina may or may not be present.
• Tunica adventitia is thin and ill defined
What are capillaries composed of?
single layer of endothelium and basal lamina
also contain pericytes that cover the basal lamina
What are the three types of capillaries?
3) discontinuous (sinusoids, sinusoidal capillaries)
Where are continuous capillaries found?
muscle, lung, and CNS
What features of continuous capillaries make the moniker "continuous" appropriate?
they have continuous basal lamina and their endothelial cells have occluding junctions between them
What are Rouget cells and what do they do?
they are the pericytes associated with some continuous capillaries
they are relatively unspecialized and can give rise to endothelial cells and smooth muscle cells
What features of fenestrated capillaries make the moniker "fenestrated" appropriate?
fenestrated capillaries have a continuous basla lamina but have small openings in their endothelial cells that allow for diffusion of small molecules and limited proteins
Where are fenestrated capillaries found?
primarily located in the endocrine glands, intestines, pancreas, and the glomeruli of the kidney.
Where are sinusoid capillaries found?
liver, spleen, and bone marrow
What is the largest type of capillary?
sinusoid have largest diameter
What are some features of sinusoid capillaries?
incomplete basal lamina
gaps in between endothelial cells
In the liver, sinusoid capillaries have macrophages called what?
what is a pre-capillary sphincter?
a slight thickening of smooth muscle of ana arteriole at the beginning of/connection to a capillary
What is the magnitude of a capillary network dependent on?
the relative metabolic activity of the tissue
What are the three types of veins and what is their characterization based on?
venules, small-median veins, and large veins
based on presence of absence of contents in 3 tunic layers
Venues can be further classified as what?
postcapillary or muscular venules
Where are postcapillary venules located and what do they do?
immediately distal to a capillary
they receive deoxygenated blood from capillaries
What are the contents (aka what is the structure) of postcapillary venules?
have an endothelium and parasites that lie on a basal membrane
do not have t media or t adventitia
What is the principle site for action of histamine or serotonin?
Where are muscular venues located?
distal to postcapillary venules
What is the major difference in the structure of muscular venules vs. the structure of post capillary venules?
muscular venules have t media and t adventitia in addition to the endothelial layer
What are some common features of median and large veins?
they all have:
1) three tunic layers (t intima, t media, and t adventitia)
2) their lumen are larger than correspondingly sized arteries
3) many veins, especially those that serve the periphery, contain valves that ensure unidirectional flow
What are the main features of median veins?
• Tunica intima consist of endothelium, BM, thin sub endothelial layer, and sometimes thin internal elastic lamina.
• Tunica media layers of circularly arranged smooth muscle cells
• Tunica adventitia thicker than T media, consist of collagen and elastic fibers
Which have larger t media sections, medium sized arteries or veins?
What are the main features of large veins?
• T. intima has endothelial lining, BM, and thin sub endothelial layer
• T. media is thin, has circularly arranged smooth muscle fibers that alternates with CT
• T. adventitia is the thickest layer and has bundles of longitudinally arranged smooth muscle.
Which have larger t media sections, large sized arteries or veins?
Which have larger lumens, large sized arteries or veins?
Which have larger t adventitia sections, arteries or veins?
In histological sections, why are veins more collapsed than arteries?
Due to the thin t. media section
What do arteriovenous shunts do?
AV shunts or anastomoses regulate blood flow by allowing direct communication between arterioles and venules
Smooth muscle contraction of arterioles in AV anastomoses sends blood to capillaries, relaxation sends the blood directly to venules, bypassing the capillaries
Are lympahtic vessels unidirectional? Due to what?
Yes, due to valves