vessel stuff

What are the five major types of blood vessels?

Arteries, arterioles, capillaries, venules, and veins

Which blood vessels carry blood away from the heart?

Arteries

Which blood vessels carry blood toward the heart?

Veins

Which blood vessels are the primary site of gas and nutrient exchange?

Capillaries

Which vessels connect arterioles to venules?

Capillaries

What is the smallest type of blood vessel?

Capillaries

Which vessel type is called the resistance vessel?

Arterioles

Which vessel type contains the highest blood pressure?

Arteries

Which vessel type contains valves to prevent backflow?

Veins

Name the three tunics of a blood vessel from inner to outer.

Tunica interna, tunica media, tunica externa

Which tunic is lined by endothelium?

Tunica interna

Which tunic contains smooth muscle?

Tunica media

Which tunic is primarily composed of collagen and elastic fibers?

Tunica externa

Which tunic is usually the thickest layer in arteries?

Tunica media

Which tunic is usually the thickest layer in veins?

Tunica externa

Compared with arteries, veins have a thicker or thinner tunica media?

Thinner

Compared with arteries, veins have a larger or smaller lumen?

Larger

Why do arteries have thicker walls than veins?

They must withstand higher blood pressure

What is the function of elastic arteries?

Conduct blood away from the heart while smoothing pressure fluctuations

What is the largest elastic artery?

Aorta

What type of artery distributes blood to organs?

Muscular artery

Which vessel type is the major regulator of systemic vascular resistance?

Arterioles

Why are arterioles called resistance vessels?

They regulate blood flow by changing lumen diameter

What controls vasoconstriction and vasodilation in arterioles?

Smooth muscle in the tunica media

What is a capillary bed?

A network of capillaries supplied by one metarteriole

Approximately what percentage of capillaries are actively perfused at one time?

About 25%

What structure regulates blood flow into capillary beds?

Precapillary sphincters

What is vasomotion?

Intermittent contraction and relaxation of precapillary sphincters

How often does vasomotion typically occur?

About 5–10 times per minute

What is the vessel called after the precapillary sphincters where there is no smooth muscle?

Thoroughfare channel

What are the three types of capillaries?

Continuous, fenestrated, and sinusoids

Which capillary type is the most common?

Continuous capillaries

Where are continuous capillaries commonly found?

CNS, lungs, skin, and muscle

Which capillary type contains pores (fenestrations)?

Fenestrated capillaries

Where are fenestrated capillaries commonly found?

Kidneys, intestinal villi, endocrine glands, ciliary processes, and choroid plexus

Which capillary type has the greatest permeability?

Sinusoids

Where are sinusoids commonly found?

Liver, spleen, anterior pituitary, parathyroid, and adrenal glands

Which capillary type allows proteins and even blood cells to pass through?

Sinusoids

Which tissues have especially extensive capillary networks?

Brain, liver, kidneys, and nervous tissue

Which tissues have relatively few capillaries?

Ligaments and tendons

Name three structures that normally lack capillaries.

Cornea, lens of the eye, and cartilage

What are the two types of venules?

Postcapillary venules and muscular venules

Which venules allow white blood cells to leave the bloodstream?

Postcapillary venules

Which venules continue nutrient and waste exchange?

Postcapillary venules

Which venules serve as blood reservoirs?

Muscular venules

Why are veins considered capacitance vessels?

They can hold large volumes of blood

What is the primary force moving blood through veins?

The pumping action of the heart

Besides the heart, what two mechanisms assist venous return?

Skeletal muscle pump and respiratory pump

How does the skeletal muscle pump increase venous return?

Muscle contractions squeeze veins and push blood toward the heart

How does the respiratory pump increase venous return?

Pressure changes during breathing move blood toward the heart

What are the three primary mechanisms of capillary exchange?

Diffusion, bulk flow, and transcytosis

Which mechanism is responsible for most capillary exchange?

Diffusion

What determines the rate of diffusion across a capillary wall?

Concentration gradient

Which substances diffuse easily through capillary walls?

Oxygen, carbon dioxide, glucose, amino acids, and lipid-soluble molecules

What is bulk flow?

The movement of fluid and dissolved substances together due to pressure differences

What are the two processes involved in bulk flow?

Filtration and reabsorption

What is filtration?

Movement of fluid out of the capillary into the tissues

What is reabsorption?

Movement of fluid from the tissues back into the capillary

What force pushes fluid out of a capillary?

Blood hydrostatic pressure

What force pulls fluid back into a capillary?

Blood colloid osmotic pressure

Which plasma protein contributes most to blood colloid osmotic pressure?

Albumin

At which end of a capillary is filtration greatest?

Arterial end

At which end of a capillary is reabsorption greatest?

Venous end

What happens to excess filtered fluid that is not reabsorbed?

It enters the lymphatic system

What is edema?

Accumulation of excess fluid in the tissues

Name one cause of edema.

Increased capillary pressure, decreased plasma proteins, increased capillary permeability, or lymphatic obstruction

What is transcytosis?

Movement of large molecules across endothelial cells in vesicles

Which substances commonly use transcytosis?

Large proteins and hormones

What is blood flow?

The volume of blood moving through a vessel or organ per unit time

What is blood pressure?

The force exerted by blood against vessel walls

What is the main driving force for blood flow?

Pressure gradient

Blood flows from areas of _____ pressure to _____ pressure.

Higher; lower

What is vascular resistance?

The opposition to blood flow

What three factors primarily determine vascular resistance?

Vessel diameter, blood viscosity, and vessel length

Which factor has the greatest effect on resistance?

Vessel diameter

If vessel diameter decreases, resistance _____?

Increases

If vessel diameter doubles, blood flow generally _____.

Increases

How does vasoconstriction affect resistance?

It increases resistance

How does vasodilation affect resistance?

It decreases resistance

How does increased blood viscosity affect blood flow?

It decreases blood flow

How does increased vessel length affect resistance?

It increases resistance

What is systemic blood pressure primarily determined by?

Cardiac output and peripheral resistance

State the relationship between cardiac output and blood pressure.

As cardiac output increases, blood pressure tends to increase

State the relationship between peripheral resistance and blood pressure.

As peripheral resistance increases, blood pressure tends to increase

What is systolic blood pressure?

The pressure during ventricular contraction

What is diastolic blood pressure?

The pressure during ventricular relaxation

What is pulse pressure?

Systolic pressure minus diastolic pressure

Calculate the pulse pressure if blood pressure is 120/80 mmHg.

40 mmHg

What is mean arterial pressure (MAP)?

The average pressure driving blood through systemic circulation

Approximate MAP using blood pressure measurements.

Diastolic pressure + 1/3 pulse pressure

Calculate MAP for a blood pressure of 120/80 mmHg.

About 93 mmHg

Where are the major arterial baroreceptors located?

Carotid sinus and aortic arch

What do baroreceptors detect?

Changes in blood pressure

Where are the major peripheral chemoreceptors located?

Carotid bodies and aortic bodies

What do chemoreceptors detect?

Changes in oxygen, carbon dioxide, and pH

Where is the cardiovascular center located?

Medulla oblongata

Which nervous system division increases heart rate and blood pressure?

Sympathetic nervous system

Which nervous system division decreases heart rate?

Parasympathetic nervous system

What effect does sympathetic stimulation have on arterioles?

Vasoconstriction

What effect does parasympathetic stimulation have on most systemic blood vessels?

Little to no direct effect