the inner most layer of a blood vessel; including the endothelial lining of the vessel and an underlying layer of connective tissue that contains elastic fibers (THE ELASTIC MEMBRANE IS ONLY IN ARTERIES)
The middle layer of a blood vessel; including sheets of smooth muscle tissue. In arteries you will find thin bands of elastic fibers and on the outer edge of the media you will find an external elastic membrane
the outermost layer of a blood vessel; composed mainly of collagen fibers.
>In arteries you will find scattered bands of elastic fibers
>this layer is usually thicker in veins
1. Walls of arteries are thicker than those of veins.
>The media of artery contains MORE smooth muscle and elastic fibers than does that of a vein.
2. Arterial walls contract. for this reason they may appear smaller, this is because they hold there shape better than veins. they are thick and strong. veins, when cut tend to collapse where as arteries hold there shape.
3. the endothelial wall of arteries does not contract which gives it a pleated/folded look.
What are three differences in veins and arteries?
Elastic arteries (conducting arteries)
--Large vessels (e.g., pulmonary trunk and aorta)
--Tunica media has many elastic fibers and few muscle cells
--Elasticity evens out pulse force
--transport large volumes of blood away from the heart.
Muscular arteries (distribution arteries)
--Are medium-sized (most arteries)
--Tunica media has many muscle cells
--Transport blood to the body's skeletal muscle and internal organs.
--Greater density of smooth muscle within the media than elastic arteries.
--Have little or no tunica externa
--Have thin or incomplete tunica media
--they control the blood flow between arteries and capillaries.
--is poorly defined and the media consists of scattered smooth muscle fibers that may not form a complete layer.
The smallest and most delicate blood vessels; permit exchange between the blood and the surrounding interstitial fluids
a typical capillary consists of an endothelial tube with nucleus enclosed within a delicate basal lamina
1. Continuous capillaries
2. Fenestrated capillaries
What are three types of capillaries?
--Found in most regions of the body
--the endothelium is a complete lining
--the endothelial cells are connected by tight junctions and desmosomes more fitted
--found in endocrine organs (glands), filtration sites of kidneys and in the choroid plexus
--they have a "swiss cheese" appearance.
--they contain pores in there walls due to an incomplete/perforated endothelial lining.
--resemble fenestrated capillaries, BUT they have larger pores and a thinner basal lamina. *in some organs they have no basal lamina* --they follow the internal contours of complex organs. The liver, bone marrow and suprarenal glands.
The exchange; this is where anterioles (arteries) and venules (veins) come together through capillary beds!
--a band of smooth muscle that guards the entrance to every capillary.
--control by reducing or stopping the blood flow that travels through capillaries.
--they dilate with an increase in carbon dioxide
--they contract with a decrease of carbon dioxide indicating the need for oxygen and nutrients.
the automatic adjustment of blood flow to each tissue in proportion to its needs, and is controlled intrinsically by modifying the diameter of local arterioles and sphincters
direct connections between arterioles and venules. this is helpful within visceral organs and joints when blood supply is lacking going through the capillary bed due to the position of your body.
purpose of veins
to collect blood from tall tissues and organs and return it to the heart.
*Note* veins walls are structurally not as strong as there corresponding artery so they may have a greater diameter in different regions.
the smallest venules lack a media. However, in the largest venules you will find scattered smooth muscle cells
contain a thin media and the thickest layer is the adventitia which contains longitudinal bundles of elastic and collagen fibers
*Ex. superior and inferior venae cavae* all of the layers are thickest in large veins. Still a slender media which is surrounded by a thick adventitia, mix of elastic and collagenous fibers
infoldings of the intima layer. they prevent the back flow of blood. explanation: venous valves break the blood flow back to the heart into compartments so to speak, and contractions in the surrounding skeletal muscles help to squeeze the blood towards the heart
when smooth muscles in the walls of venous veins contract reducing the volume of the venous system
the venous system acts as a blood reservoir for when the body is undergoing blood loss and can help to maintain the volume within the arterial system at near-normal levels despite a significant blood loss. (liver acting as primary reservoir)
At this point attempt to do the concept check questions on the bottom right of page 577! (in the study guide)
composed of arteries and veins that transport blood between the heart and the lungs.
There are 3 important functional patterns of the pulmonary and systemic circuit...
1. the peripheral distribution of arteries and veins on the left and right sides is usually identical except near the heart, where the largest vessels connect to the atria or ventricles
2. A single vessel may have several different names as it crosses specific anatomical boundaries, making accurate anatomical descriptions possible when the vessel extends far into the periphery.
3. Arteries and veins often make anastomotic connections that reduce the impact of a temporary or even permanent blockage of a single vessel
arterial trunk that has three major branches, which serve the liver, spleen, and stomach
these were not all of the arteries that need to be known but most of them (: refer to the in class ws for the rest.
THE FOLLOWING SLIDES 59
large vein that carries nutrient rich blood from the digestive organs to the liver for processing