Blood Vessels: Cardiovascular System

STRUCTURE AND FUNCTION ONLY

Explain why the human cardiovascular system is a closed system of tubes

it carries the blood away from the heart, transport it to tissues, and returns it to the heart, they never exit freely into the body cavities

Lumen of a blood vessel

the space within an artery, vein, intestine, renal tubule or any tubular structure, there for blood flow and pressure with blood

Arteries Function

carry blood away from the heart to other organs

Veins function

are the blood vessels that convey blood from the tissues back to the heart

What is the role of capillaries 

allow exchange of gas and nutrients

allow oxygen to diffuse from the blood into surrounding tissues

transport nutrients (glucose etc) from blood to the cells 

Tunics (they are part of the wall of the arteries and veins)

tunica intima (inner lining), tunica media (middle layer of smooth muscle and elastic CT) and tunica externa ( CT outer covering)

Tunica Interna’s endothelium is

simple squamous epithelial cells, its for blood to flow smoothly

How does the endothelium of tunica internal prevent thrombus (blood clot)

they release anticlotting chemical factors 

Vasa Vasorum (such as the aorta)

in tunica externa, they are blood vessels that supply nutrients to large arteries or veins

Anastomoses and the alternate routes for blood flow

is an end to end of joining blood vessels, lymphatic vessels or nerves

provides arteries for alternate routes

may occur between veins and between arterioles and venules

Collateral circulation

is the alternative route of blood flow to a body part through an anastomosis 

Elastic (conducting) arteries structure and function

largest arteries, elastic membrane in tunica intima , thick tunica media, thin tunica externa, and they conduct blood from the heart to muscular arteries

Muscular Arteries structure and function

medium sized arteries, defined elastic membrane in tunica intima, thick tunica media, thick tunica externa, distribute blood to arterioles

Arterioles (resistance vessels) structure and function 

microscopic, thin tunica intima, few layers of tunica media, collagenous CT and sympathetic nerves in tunica externa, and delivers blood to capillaries and help regulate blood flow from arteries to capillaries

Arterioles role in altering peripheral resistance

systemic vascular resistance (aka) it refers to all of the vascular resistances offered by systemic blood vessels. Arterioles are the smallest vessel so they contribute the most resistance 

What is a major function of arterioles in total peripheral resistance?

it controls SVR and therefore blood pressure and blood flow to the tissues by changing their diameters. They need to vasodilate or vasoconstrict only slightly to have that larger effect.

Arterioles in blood pressure

they have the key role of regulating blood flow from arteries into capillaries and in altering arterial blood pressure

How to determine blood flow into capillaries

multiply the total cross sectional area of all capillaries by the average blood velocity through them ( Q= Ax V) 

Design of Metarterioles

smooth muscle that control the flow of blood through capillaries

Function of metarterioles

key regulator of blood flow controlling which capillary beds receive blood

What is the design of thoroughfare channel

no smooth muscle, resemles a capillary

What is the function of thoroughfare channel

a channel provides a direct route for blood from an arteriole to a venule, this will bypass capillaries

What is the design of precapillary spincters

the distal most muscle cell at the metarteriole capillary junction, smooth muscle fibers

What is the function of precapillary sphincter?

regulate and monitor blood flow into true capillaries

What are true capillaries and what is their function

smallest and has the most blood vessels, forming a capillary beds that branches mainly from arterioles and drain into venules, provide oxygen and nutrients, remove waste products

Continuous Capillaries

in plasma membrane of endothelial cells form a tube that is interrupted by gaps between neighboring cells. they are in the central nervous system, lungs, muscle tissue and skin

What are fenestrated capillaries

plasma membrane of endothelial cells they have many fenestrations (small pores) in their capillaries, in the kidney, intestinal villi, choroid plexuses. eye, ventricle in brain

What are sinusoids

wider and winding than others, have unusually large fenstrations. absent basement membrane. in the liver, spleen, antiuatary pituatary, parathryoid

What is the critical importance of the role of capillaries

their thin walls enable the exchange of oxygen, nutrients and waste products between the blood and body tissue. they are the connection were arteries and veins meet

What is the mechanism of exchange of substances between blood and tissue cells

occurs over the wall of capillaries through diffusion (simply diffusion, oxygen co2 and glucose)  transcytosis (blood plasma becomes enclosed with tiny vesicles)  and bulk flow (large number of ions and molecules that go in the same direction)

Venules

tiny vessels that collect blood from capillaries to form larger veins

Larger Vein

much larger, they lead back to the heart, thicker walls, conduct blood at low pressure back to the heart and have high capacitance (how much blood they hold)

Why are veins described as blood reservoirs  and capacitatance vessels

they hold a lot of blood volume, thinner less muscular and elastic compared to arteries, blood pressure are very low and can be stretched easily, they can hold storage, and constrict

Principle differences in the design of the walls of veins versus arteries and their functional role

Veins are called capacitance vessels or blood reservoirs because their unique design allows them to hold approximately 60-75% of the body's total blood volume at any given moment. extremely high compliance thin, less muscular walls and wide lumens, now arteeries are thick walled muscular that withstand high pressure

Why is the lumen of a vein always larger than the lumen of a nearby artery

the lumen of a vein has thin walls to accommodate high volume at low pressure since it is just taking blood to the heart and it acts as that reservoir, the artery however is taking blood away from the heart under high pressure by the hearts contractions so they need that thick muscular lumen for greater resistance

what are the role of valves in veins?

ensure blood flow in only one direction towards the heart and prevent any backflow 

Pressure Reservoir and Elastic Recoil Role of large arteries

Windkessel Effect, using elastic recoil to maintain continuous blood flow during the hearts resting phase

Smooth Muscle in Tunica media of arterioles

regulating blood flow and blood pressure, it contracts when a small artery is damaged to help limit blood loss, helps with elastic fibers to stretch and recoil

Tunica media and vasoconstriction and vasodilation

decrease the diameter is vasoconstriction

increase the lumen of diameter is vasodilation

for regulating blood pressure