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Histo- Heart & blood vessels


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What are the three layers of vessels in general?
tunica intima= innermost layer
tunica media= middle layer
tunica adventitia= outermost layer
Is the tunica intima closest to the lumen of the blood vessels?

What is the TI lined with?

What type of cells is endothelium made of?
simple squamous epithelial cells
What is the tunica intima composed of?
connective tissue and firbroblasts with some elastic and collagen fibers
What forms the outer boundary of the tunica intima and is the boundary between the tunica intima and the tunica media?
the internal elastic membrane
Do the cells and fibers of the tunica intima run parallel or perpendicular in the vessel?
What is a function of the tunica intima?
it provides a smooth surface to prevent blood clotting.
What direction do the fibers and the cells of the tunica media run in relation to the long axis of the vessel?
perpendicular in a circular manner around the vessel
What type of cells and membranes are located in the tunica media?
smooth muscle cells and elastic membranes
Do the smooth muscle cells of the tunica media give rise to elastic tissue?
What is the vasa vasorum?

Give an example of a vasa vasorum
-small arteries and veins that lie in the wall of large vessels and give nutrients to the muscle tissue: the vessel of the vessel
-coronary arteries are the vasa vasorum of the heart
How do small blood vessels recieve nutrition?
Where can one find the vasa vasorum in a blood vessel?
in the tunica adventitia and the outskirts of the tunica media
What does the connective tissue of the tunica adventitia contain?
-collagen fibers
-the external elastic membrane (is part of the TA, not boundary)
-in larger vessels the vasa vasorum
Do tunica adventita fibers run parallel or perpendicular to the long axis of the blood vessel?
What are the three classifications of arteries?
1. elastic arteries
2. muscular arteries
3. small muscular arteries/arterioles
What are elastic arteries?
-the very large distributing arteries
-example=aorta and renal arteries
In elastic arteries is the tunica intima thick or thin?
-It is a thick subendothelial layer of CT
-some elastic fibers making the internal elastic membrane but hard to see
In the elastsic arteries, what types of cells does the tunica intima contain?
-some smooth muscle cells
-some elastic fibers making the internal elastec membrane
In the elastic arteries, is the tunica media thick or thin?
In the elastic arteries, does the smooth muscle alternate with elastic membranes in the tunica media? Why?
-because the smooth muscle is producing the elastic membranes
In the elastic arteries, what does the structure of the elastic membranes look like?
the elastic tissue is full of fenestrations
What are the fenestrations in the elastic tissue of the tunica media of the elastic arteries?
holes in the wall to allow the passage of material such as nutrients, ions and wastes
In the elastic arteries, is the tunica media fed by a vasa vasorum?
In the elastic arteries, what does the tunica adventitia contain?
the vasa vasorum
What are the muscular arteries known as?
most named arteries of the body wall and organs
In the muscular arteries,is the tunica intima thick or thin?
thin subendothelial CT layer
In the muscular arteries, is the tunica intima bordered by an internal elastic membrane?
In the muscular arteries, what does the tunica media contain?
2-40 layers of circular smooth muscle
In the muscular arteries, is there an external elastic membrane present in the tunica adventitia?
only in larger arteries
In the muscular arteries, is a vasa vasorum present?
no, these vessels are small enough to suppply nutrients by diffusion
What are the small muscular arteries/arterioles?
the smallest of the arteries
In the small muscular arteries/arterioles, what size is the tunic intima?
less than .5mm in diameter
In the small muscular arteries/arterioles, what does the tunica media contain?
102 layers of circular smooth muscle
In the small muscular arteries/arterioles, does the tunica adventitia contain an external elastic membrane?
How many red blood cells can travel through a capillary at a time?
only one- if you see 2-3 cells side by side it is not a capillary
What are general characteristics of capillaries?
-composed of a single layer of endothelial cells that are simple squamous epthelium
-all cells rest on a basal lamina/basement membrane
-pericytes are scattered along the surface
What is a pericyte?
-a mesenchymal cell with long cytoplasmic processes that partly surround the endothelial cells of the capillary
- these cells are enclosed in their own basement membrane
What is the function of a pericyte?
-is contractile, contains actin, myosin, and tropomyosin,helps move the fluid in the lumen of the capillary on through it
-can repair after tissue injury, can form new blood vessels and CT
What are continous or somatic capillaries?
endothelium is characterized by an absence of fenestrae in the wall, all cells rest on a continuous basement lamina/membrane
How do continous/somatic capillaries transport stuff without fenestrations?
Where are continous/somatic capillaries located?
-in muscle, CT, exocrine glands, and nervous tissue
**can not see this on a slide but must know from the type of tissue it is in
-found where rapid exchange is not needed
What are fenestrated/visceral capillaries?
endothelium is characterized by large fenestrae in the wall that are either uncovered or covered by a thin diaphragm (not trilaminar), all cells rest on a basement membrane/lamina
How do fenestrated/visceral capillaries transport stuff?
across the fenestrae
Where are fenestrated/visceral capillaries located?
-in organs where rapid transport between tissues and blood is needed
-kidneys, intestines, endocrine organs
What are sinusoids?
-a specialized capillary which has an enlarged diameter and has a tortuous course that slows the circulation of blood
-these are fat capillaries
-are wider & accomidate more than one blood cell
-do not have pericytes
-have endothelium and a basal lamina outside of endothelial cells
What are characteristics of fenestrated sunusoids?
their cells have fenestrae, are in endocrine organs
What are characteristics of discontinous sunusoids?
there are gaps or spaces where two endothelial cells join, the basal lamina may be discontinuous, is in the liver and other organs
What is the function of capillaries/sinusoids?
-exchange of materials across the wall of the capillary
-materials = gas(CO2 or O2) or nutrients
What type of capilliary is in skeletal muscle?
continous, this is why muscles fatigue
What are the comparitive speeds through the different types of capillaries?
What do veins do?
return blood to the heart
Are the walls of veins more or less organized than arteries?
Do veins have organized smooth muscle in them?
Are there more veins or arteries in the body?

Are the walls of veins thicker or thinner than arteries?

Is the circumfrence of a vein larger or smaller than an aretery?
-more veins
What are some general characteristics of veins?
-low blood pressure
-contain valves
-thickest layer in veins is the tunica adventitia
What is a venule?
-a thin wall vessel, the endothelium is similar in function to the capillary but the diameter begins to enlarge.
-is a very small caliber vein
What are small veins?
most of the veins in the body with the exception of the main trunks
Do venules contain a tunic adventita?
What does the tunica intima of the small veins contain?
- a thin layer of CT covered by endothelium
-valves (folds of the intima)
**facial veins do not have valves
What does the tunica media of small veins contain?
a few poorly organized layers of smooth muscles
What does the tunica adventitia of small veins contain?
has well developed, numerous collagen fibers w/ no smooth muscle
What are some examples of large veins?
vena cava and renal veins
Is the tunica intima well developed in the large veins?
What are characteristics of the tunica media of large veins?
a few layers or circular arranged smooth muscle
What are characteristics of the tunica adventitia of the large veins?
-thick layer, contains longitudinal clusters of smooth muscle parallel to the long axis of the blood vessel
-this gives structural support to the wall and helps move vascular contents
-there is collagen fibers in between the smooth muscle
What is the normal capillary blood flow?
metarterioles(precapillary sphincters)
venules(postcapillary venule)
What are arteriovenous anastamoses/shunts?
-places where blood bypasses capillary beds completely or reduces flow in a capillary bed for the purpose of thermoregualtion
-direct connections between the arterial and venous systems
What is the function of arteriovenous anastamoses/shunts?
-shuts down blood flow in cold and increases blood flow in fever
-function is to regulate blood pressure, blood flow and conservation of heat
Is the arteriovenous anastamoses/shunts in addition to the capillary beds?
What are precapillary sphincters?
-sphincters that are at the end of metarterioles
-these regulate blood flow through the capillary bed
What are postcapillary venules?
-sometimes referred to as venous portion of the capillary bed
-functions similar to capillaries
-is modified in lymphatic organs for transport of the T-lymphocytes
-is surrounded by contractile pieces
-5-6 times of the capillary
Arteries compared to veins
lumen A=circular V=irregular
T.intima A=I. elastic memb V= valves
T. media A=thick V=thin
T.adventitia A=thin,no SM V=thick
Is the heart a modified blood vessel?
What are the three layer of the heart?
epicardium-T. adventitia
myocardium-T. media
endocardium-T. intima
What is the epicardium analagous to?
the visceral pericardium
Where is the epicardium on the heart?
What type of epithelium is the epicardium made of?
-external layer of the heart
-simple squamous epithelium
Where is the subepicardial CT?
What is its function?
-the subepicardial CT is under the simple squamous epithelium of the epicardium
-it contains coronary vessels, nerves, and fat of the heart
What is the myocardium?
-the middle, largest layer of the heart
-contains cardiac muscle w/ intercalated disks and the sliding filament theory
-has a rich vascular supply
What is the endocardium composed of and where is it?
-simple squamous epithelium and subenodcardium
-is the internal layer of the heart, lines the chambers
What is subendocardial tissue?
-thin CT tissue
-contains the impulse conducting system of the heart (perkinje cells)
-does not contain large coronary vessels
What are perkinje cells?
-specialized modified cardiac muscle cells of the endocardium in the subendothelium
-this is the only kind of nervous/impulse to supply cardiac muscle (the heart does not get a direct nervous supply)
What is the cardiac conducting system composed of?
-sinoatrial node
-atrioventricular node
-bundle of His

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