Blood Vessels

Arteries carry blood where?

away from the heart

A vein leads where?

towards the heart

What is vasa vasorum

small blood vessels that carry blood to tissues of blood vessel walls

Layers of blood vessel

1. tunica interna

2. tunica media

3. tunica externa

Because walls of arteries are elastic, it allows them to absorb what?

It allows them to absorb pressure created by the ventricles of the heart as they pump blood into the arteries

Which layer can regulate the diameter of an artery

tunica media

First type of artery

elastic arteries

• large diameter

• more elastic fibers

• function as pressure reservoirs

Second type of artery

muscular arteries

• medium diameter

• more smooth muscle, fewer elastic fibers

• distribute blood to various parts of the body

What is vasoconstriction

when lumen get smaller

What is vasodilation

lumen get larger

Examples of elastic arteries

• aorta

• brachiocephalic

• common carotid arteries

Examples of muscular arteries

• radial and ulnar

• external carotid

• brachial

• femoral

• mesenteric

Function of arterioles

abundant small arteries that regulate blood flow into capillaries

What is an anastomosis

the union of the branches of 2 or more arteries supplying the same region of the body

• alternate route for blood flow

What are arteries that do not form anastomosis called

end arteries

What are capillaries

microscopic vessels that usually connect arterioles and venules

What are capillaries modified for

modified for diffusion

Size of capillary bed is determined by what?

metabolic activity of tissues

• high activity = large capillaries

  • muscles, kidneys, ns

• low activity = small capillary bed

  • tendons, ligaments

What are continuous capillaries

• endothelial cells are continuous with only intercellular clefts between them

• found in CNS, lungs, muscles and skin

What are fenestrated capillaries

• fenestrations (pores)

• kidney, villi of small intestine, endocrine glands, etc

What are sinusoid capillaries

• wider and winding. large fenestrations and incomplete basement membrane

• liver, anterior pituitary, parathyroid and adrenal glands

Venous structure

• veins and venules have thin walls and do not usually retain their shapes

• veins also lock internal and external elastic lamination

• lumen is larger than a comparable artery

• can manage changes in blood flow, but not high pressure like an artery

What do veins have that arteries dont

valves

What is the largest layer of medium-sized veins

contains elastic fibers

Are large veins thin or thick

all three layers relatively thick

• superior/inferior vena cava

Which structures are considered “blood reservoirs”

systemic medium-sized veins, veins, and venules

What diffuse in capillaries

O2, CO2, glucose, Amino Acids, and hormones

What is transcytosis

vesicular transport for large, lipid-soluble molecules

What is bulk flow

passive process in which large numbers of ions, molecules, or particles in a fluid move together in the same direction

How does bulk pressure occur

it occurs from an area of higher pressure to an area of lower pressure, and it continues as long as a pressure difference exists

What generates blood pressure

contraction of ventricles

What is blood pressure determined by

• CO

• blood volume

• vascular resistance

  • the higher the blood pressure, the greater the blood flow

What is vascular resistance (R)

the opposition to blood flow due to friction between blood and walls of blood vessels

• the higher the r, the smaller the blood flow

What does vascular resistance depend on?

• size of the blood vessel lumen

• blood viscosity

• total blood vessel length

What is venous return

volume of blood flowing back to the heart from the body’s peripheral tissues through the systemic veins

What is venous return assisted by

1. valves

2. respiratory pump

3. skeletal muscle pump

What is blood flow

the volume of blood that flows through a tissue in a given period of time

4 different circulatory routes

1. systemic

2. pulmonary

3. hepatic portal

4. fetal

What is the hepatic portal circulation?

• carries blood from the digestive system full of nutrients to the liver

• veins that carry blood from one venous network to another are called portal veins

• hepatic portal vein - receives blood from the GI tract and spleen delivers to the liver

What is fetal circulation?

• oxygenated blood is delivered by umbilical arteries

• foramen ovale

• ductus arteriosus

Can arteries maintain their circular shape?

Yes

Can veins maintain their circular shape?

No

Do arteries spurt blood or does it flow out

spurt

Do veins spurt or flow out blood

flow out