Learning Objective 6

The walls of both the arteries and viens, made up of 3 layers collectively called tunics. (Media externa and intima)

Where the tunic surrounds in both viens and arteries is the space where the blood flows.

The inner most layer of the blood vessel wall, composed of epithelium (simple squamous) and a subendothelial layer made up of thin areolar connective tissue.

Is the middle layer of the vessel wall. It is composed of circularly arranged layers of smooth muscle cells (this is the largest layer in a Artery)

Is the outermost layer of the blood vessel wall. Composed of areolar that contains elastic and collagen fibers. It helps anchor the vessel to other structures.(This is the thickest layer in the vein)

Is is when very large blood vessels require their own blood supply to the externa in the form of a network of small arteries.

Are the largest, they are also called conducting arteries because they conduct blood away from the heart to the smaller muscular arteries. Very elastic. Ex. The aorta

Transport blood away from the heart, it carries oxygenated blood to the body EXCEPT for the pulmonary arteries which carry deoxygenated blood to the lungs (since technically it's a blood vessel going away from the heart , it's considered a artery.)

• Medium sized, they are also called distributing arteries because they distribute blood to the body. They have 2 rings
• 1. Internal lamina (Seperates the tunica intima from the turnica media
• 2. External elastic lamina (seperates the tunica media from the tunica externa.
• They have thick tunica media with multiple layers of smooth muscle, because of this they have a better ability to Vasoconstrict (constrict or make the luman smaller) and vasodilate (Make the lumen get bigger) Aka the muscular arteries help control blood pressure.

Small arteries, the largest of them have all 3 tunicas but the smallest arterioles may only have an endothelium surrounded by smooth muscle fibers.

narrowing of the blood vessel lumen (in the muscular artery specifically in the tunica media) helps control blood pressure.

Widening of the blood vessel lumen (in the muscular artery specifically in the tunica media) helps control blood pressure.

Also called the functional units of the cardiovascular system. The smallest blood vessels, connect arterioles to venules, only just large enough to fit ONE erythrocyte in (amazingly small) so they must travel single file. Most consist solely of a tunica intima composed of a very thin single layer of endothelium and a basement membrane, which lets nutrients and gases to be exchanged easily.

a group of capillaries that function together as a group (they do NOT function independently of one another)

What the capillary bed is fed by, which is a vessel branch of an arteriole. The proximal part of the metarteriole is encircled by scattered smooth muscle fibers, while the distal part has no smooth muscle (called the thoroughfare channel)

The distal part of the metarteriole that has no smooth muscle fibers and connects to the postcapillary venule.

drains the capillary bed.

branch from the metarteriole and make up the bulk of the capillary bed. At the origin of each to capillary is a smooth muscle ring called the precapillary sphincter,

Controls the blood flow into the true capillaries, when is relaxes it causes blood to flow directly from the metarteriole into the postcapillary venule via the thoroughfare channel. It opens when the tissue needs nutrients and closes when the needs are meet

the most common, the endothelial cells form a complete continous lining and are connected by tight junctions. Materials can pass through the endothelial cells or hte intercellular clefts via simple diffusion or pinocytosis (A type of endocytossi whereby droplets of fluid are packaged in pinocyroric vesicles) They are found in muscle skin the thymus the lungs and the CNS.

have fenestrations (pores) within each endothelial cell. they are seen when a great deal of fluid transport between blood and intersitial tissue occurs, such as in the small intwestine, most endocrine glands and the kidney.

have larger gaps than fenestrated capillaries and there basment membrane is either discontinuous or absent. They tend to be wider that allow for transport of larger materials such as protiens or cells (e.g. blood cells). They are found in the bone marrow, the anterior pituitary the spleen and the liver.

They drain capillaries and return the blood to the heart. Vein walls (compared to arteries) are relatively thin and the lumen is larger. They carry deoxygenated blood to the heart EXCEPT for the pulmonary veins which carry oxygenated blood back to the left atrium after they had fun in the lungs. Because blood pressure gradually decreases as the blood travels through capillaries the pressure is low by the time it reaches the veins. At rest the bodies veins hold about 60% of the bodies blood and thus function as the blood reservoirs.

the smallest veins, they are companion vessels with the arterioles since they both supply the same general areas and are of similar size. The smallest ones called Postcapillary venules, drain capillaries.

• Skeletal muscle pump works when the skeletal muscles are active and they contract and then the veins are squeezed to help pump the blood toward the heart (so when someone is bed ridden or not active what happens?)
• Respiratory is when you breath in and the pressure from your chest helps pump blood back into the heart.

hypertension causes undue stress on arterioles, resulting in thickening of the arteriole walls and reduction in luminal diameter.

the pressure in the vessel during ventricular systole (ventricular contractions). This force is greater then diastolic pressure due to the greater force from the ventricular contraction.

the pressure during ventricular diastole (relaxing of the ventriculars)

is a venous network that drains the GI tract and shunts the blood to the liver for absorption and processing of transported materials. Its needed because these nutrients from the GI tract must be absorbed and processed to the liver

Following nutrient absorption, the blood exits the lever through these viens that merge with the inferior vena cava

is the large vein that receives deoxygenated but nutrient rich blood from the gastrointestinal organs 3 main venous branches merge to form this vein ( Inferior mesenteric vein, the splenic vein and superior mesenteric vein)

a vertically positioned vein draining the distal part of the large intestine.

a horizontally positioned vein draining the spleen, receives blood from pancreatic veins, short gastric veins and the right gastriepiploic vein.

another vertically positioned vein on the right side of the body, drains the small intestine and part of the large intestine.

is a progressive disease of the elastic and muscular arteries. Characterized by the presence of an atheroma which leads to thickening of the tunic intima and narrowing of the arterial lumen.

Repeated injury to the endothelium of an arterial wall results in an inflammatory reaction that eventually leads to the development of an atheroma.

(an increased amount of cholesterol in the blood) which tends to run in families, has been positively associated with the rates of developement and severity of atherosclerosis.