BIO 122 Vessels and circulation

All blood vessels are part of what circuit?

Both Pulmonary and Systemic circuit

What do blood vessels do ?

Conduct blood between the heart and peripheral tissues

Where does arteries/efferent vessels carry blood to?

AWAY from the heart

Where do veins/afferent vessels return blood to ?

BACK to the heart

What does capillaries do ?

Exchange substances between blood and interstitial fluid

What does Capillaries interconnect?

Interconnect smallest arteries and smallest veins

What is the path of the pulmonary circuit?

Deoxygenated blood leaves from right ventricle, to the lungs for gas exchange, and returns oxygenated blood to the left atrium

Pulmonary circuit =

gas exchange

Systemic circuit pathway

Oxygenated blood leaves body from left ventricle, out through body, and returns deoxygenated blood back to the right atrium

What are the 3 layers of arteries and veins

1. Tunica intima

2. Tunica media

3. Tunica externa

Vasa vasorum

Large vessel walls of arteries/veins contain what for nourishment ?

Tunica intima

Innermost layer; in all vessels; elastic fibers

What cells does the Tunica intima contain?

Endothelial cells with CT with elastic fibers

What is special about arteries and Tunica intima?

Has an internal elastic membrane

Tunica media

Middle layer; concentric sheet of smooth muscle

Vasoconstriction

Contraction of tunica media

Vasodilation

Relaxation of tunica media

External elastic membrane

Separates the tunica externa from tunica media

Tunica externa

Outermost layer

What does the Tunica externa contain

Elastic fibers and smooth muscle

What is special about arteries in Tunica externa?

Contains collagen, scattered elastic fibers

What is special about veins in Tunica externa?

Generally thickers than tunica media

What does Tunica externa do?

Anchors vessel to surrounding tissues

What are the 5 general blood classes?

1. Arteries (outgoing)

2. Arterioles (outgoing)

3. Capillaries (exchange)

4. Venules (return)

5. Veins (return)

Arteries: outgoing, exchange, or return?

outgoing

Arterioles : outgoing, exchange, or return?

outgoing

Capillaries : outgoing, exchange, or return?

Exchange

Venules : outgoing, exchange, or return?

Return

Veins : outgoing, exchange, or return?

Return

Elastic arteries

• Large vessels closet to heart

• Stretch/recoil when heart beats

What type are arteries include pulmonary trunk, aorta, and branches?

Elastic arteries

Muscular arteries

• Medium-sized arteries

• Distribute blood to skeletal muscles and internal organs

Arterioles

• Little or no Tunica externa

• Tunica only 1-2 smooth muscle cells thick

What is unique about Capillaries?

• Unique in only blood vessels that allow exchange between blood and interstitial fluid

• Very thin walls allow easy diffusion

Venules

• Very small veins; most lack a tunica

• Collect blood from capillaries

Medium-sized veins

• Thin tunica media with smooth muscle collagen

• Thickest layer is tunica externa with collagen and elastic fibers

Large veins

• Have all three vessel wall layers

• Include superior and inferior vena cava tributaries

Typical capillary

• Made of simple squamous endothelial cells with delicate basement membrane

• No tunica media or tunica externa

What are the 2 types of capillaries?

1. Continuous capillaries

2. Fenestrated capillaries

Continuous capillary

• Least permeable; endothelium forms a complete lining

Where is continuous capillary located ?

• Located throughout body in all tissues EXCEPT epithelia and cartilage

Fenestrated capillary

• Contains “windows” or pores in endothelial lining

• Permits rapid exchange of water and larger solutes

Examples of fenestrated capillaries

• Choroid plexus of brain

• Capillaries of hypothalamus, pituitary, pineal, thyroid

• Absorptive areas of intestinal tract

• Kidney filtration sites

Sinusoids

• Basement membrane is thin or absent

• Permit more water and solute (plasma proteins) exchange

Where does sinusoids occur ?

Occurs in

• Liver

• Bone marrow

• Spleen

• Many endocrine organs

Capillary bed

• Interconnected network of capillaries

• With several connections between arterioles and venules

Multiple arteries fuse together is an example of ?

Arterial anastomois

Anastomosis

is joining of blood vessels

Capillary bed function

Allows continuous delivery of blood to capillary bed even if one artery is blocked/compressed

Capillary bed can be bypassed by what that direclty connects arteriole to venule?

Arteriovenous anastomosis

Precapillary arteriole, or Metarteriole

• Initial segment of connection passageway

• Smooth muscle can change vessel diameter and adjust flow rate

Precapillary arteriole

• Initial segment of connection passageway

• Smooth muscle can change vessel diameter and adjust flow rate

Thoroughfare channel

Most direct passageway through bed

Precapillary sphincters

Bands of smooth muscle that contract and relax to control flow into the capillary bed

Valves

• Flaps of tunica intima projecting from vessel wall, pointing in the direction of blood flow

What is the muscle is contracting in veins ?

Skeletal muscle

Valves permit blood flow in what direction?

Valves permit blood flow in one direction and prevent backflow of blood toward capillaries

Varicose veins

Mild to moderate discomfort and cosmetic problems, as with varicose veins

Hemorrhoids

Painful distortion of adjacent tissues

Is it an even distribution of blood among arteries, veins, capillaries?

No it’s uneven

What acts as blood reservoirs ?

Systemic veins contain 64 % of total blood volume

Hepatic portal system

Systemic veins carrying blood from digestive organs to liver

What causes Venoconstriction?

• Smooth muscle fibers in veins contract

• Reduces diameter of veins

What method of maintaining blood volume in the arterial system even with a significant blood loss is used ?

Venoconstriction

Where is the vasomotor center located ?

Medulla oblongata

Does the Parasympathetic or Sympathetic nervous system stimulate smooth muscles in medium-sized vines

Sympathetic

What is the formula of pressure ?

Pressure = Resistance x Flow

Flow

The volume of blood moving through a vessel within a certain time

To maintain proper blood flow, and increase in resistance will require a __ in pressure

increase (to overcome resistance)

Total peripheral resistance

= Resistance of entire cardiovascular system to blood flow

What must over Total peripheral resistance overcome?

Overcome by sufficient pressure from the heart for circulation to occur

Total peripheral resistance 3 factors

1. Vascular resistance

2. Viscosity

3. Turbulence

Vascular resistance

Resistance to blood flow in vessels

What is the main contributor to total peripheral resistance ?

Total peripheral reistance

Whaat are the 2 factors of vascular resistance ?

1. Vessel length

2. Vessel diameter

Length of each vessel is __, but the diameter can _

Set, change

Viscosity

Resistance to flow caused by molecular interactions among molecules in a liquid

Lower viscosity =

Easier flowing

Higher-viscosity fluids is lower or higher resistance ?

Higher resistance; flow only at high pressuree

Turbulence

Caused by high flow rates, irregular surfaces, and sudden changes in vessel diameter

Increases turbulence causes increases resistance which results in ?

Decrease flow

Blood flow

Volume of blood flowing through a vessel or group of vessels per unit of time

What is blood flow proportional to ?

Arterial pressure

What is blood flow inversely proportional ?

Peripheral resistance

What is more important than absolute pressure ?

Pressure gradient

What are the factors that affect blood flow ?

• Changes in vessel diameter

• Changes in blood pressure

• Changes in blood flow

• Arterial pressure

• Pulse pressure

• Mean arterial pressure (MAP)

Blood flow: outgoing from aorta to capillaries

• wide to narrow

• decreased diameter = increased resistance = decreased pressure = decreased flow

Blood flow: incoming from capillaries to vena cava

• narrow to wide

• increased diameter = decreased resistance = increased flow

Where is the highest pressure of blood flow (and largest diameter)

Aorta

Where is blood flow the slowest (and smallest diameter)

Capillaries

Flow accelerates in venous system due to larger diameter vessels =

lower resistance

Systolic pressure

Arterial pressure increases during ventricular systole

Diastolic pressure

Arterial pressure decreases during ventricular diastole

Pulse pressure

= difference between systolic and diastolic pressure

Example of pulse pressure

120-90=30 mmHg

If there is greater resistance, a __

greater pulse pressure is needed to overcome it

Mean arterial pressure (MAP)

= Diastolic pressure + 1/3 pulse pressure

Example of mean arterial pressure

90+(120=90)/3= 100mmHg

What does capillary exchange involve?

Combination of diffusion, osmosis, and filtration

What does materials exchange in capillary exchange ?

Materials are exchange between blood and interstitial fluid