A&P II Ch. 4 - Blood Vessels

about 100,000 miles of blood vessels

The human adult circulatory system is made of how many miles of blood vessels?

away from the heart

Arteries carry blood where?

nutrient & gas exchange in the tissues

Capillaries enable what?

back to the heart

Veins carry blood where?

- They all have arterial AND venous blood supply

- allows all organs to get oxygen & nutrients they need

- allows blood flow to individual organs to be regulated

All the body's organs have what kind of blood supply? What does this allow?

branhch off the aorta

All systemic arteries branch off where?

from arterial to venous capillaries

All blood flows from where to where?

- Not all venous capillaries return deoxygenated blood directly to the heart

- Not all arterial capillaries exchange oxygen/carbon dioxide

- EXCEPTIONS are the Portal Systems:

- Hepatic portal, pituitary portal, & renal portal systems

Not all venous capillaries do what? Not all arterial capillaries do what? What are the exceptions?

1. Pituitary Portal System

2. Hepatic Portal System

3. Renal Portal System

What are the 3 Portal Systems?

1. Tunica Externa (adventitia)

2. Tunica Media

3. Tunica Intima (interna)

What are the 3 layers of the Blood Vessel?

except for the capillaries

All blood vessels have the tunica media and tunica adventitia layers except for..?

- it's the outermost layer of blood vessels

- made of tough connective tissue

- function is to anchor blood vessels in place

What is the Tunica externa (adventitia)? Describe it too.

- middle layer of the blood vessels

- elastic connective tissue allows blood vessels to stretch --> increase blood volume

- function is vasodilation & vasoconstriction by smooth muscle

What is the Tunica media? Describe it too.

- the innermost layer of blood vessels

- endothelium is continuous with the endocardium

- simple squamous epithelium

- function is reduced friction & turbulence and permeability barrier

What is the Tunica intima (interna)? Describe it too.

Arteries: tunica media

Veins: tunica externa

What is the thickest layer in Arteries vs. Veins?

Arteries: typically round

Veins: often irregularly shaped

What is the shape of lumen in Arteries vs Veins?

found in tunica intima

In Veins, where are valves found?

only have tunica intima

Capillaries (exchange vessels) only have what layer?

blood vessels that are part of the systemic circuit that carry oxygenated blood from heart to body and deoxygenated blood from body to heart

What are Systemic Vessels?

- carry deoxygenated blood to lungs by arteries

- carry oxygenated blood to heart by veins

Describe the kind of blood and the location Pulmonary Vessels carry to and from.

they hold more blood than other vessels

Why are veins considered blood reservoir vessels?

- Conducting vessels

- Distributing vessels

- Resistance vessels

- Exchange vessels

- Reservoir vessels

What are the functional names of Systemic Vessels?

their high level of elastic proteins

Where do Elastic Arteries get their name from?

- "Conducting vessels" conduct blood from heart

- Examples: aorta & pulmonary trunk

- Function: stretching creates a pressure reservoir by capturing systolic pressure from the ventricle & recoiling to help close the semilunar valves

Describe Elastic Arteries.

from their thick tunica media (made of smooth muscle)

Where do Muscular Arteries get their name from?

- "Distributing vessels" distribute blood to various organs and tissues

- Examples: most arteries in the body

- Function: regulatin blood flow through vasoconstriction & vasodilation

Describe Muscular Arteries.

the smallest kind of blood vessel before the capillary beds

What are Arterioles?

- "Resistance vessels" due to dilation and constriction

- Function: changing resistance to regulate capillary blood flow (resistance opposes flow)

- Increasing resistance increases pressure

Describe Arterioles.

- Vasodilation increases capillary blood flow (decreasing resistance and pressure)

- Vasoconstriction decreases capillary blood flow (increasing resistance and pressure)

What are the mechanisms of regulation for Arterioles?

- They're tiny blood vessels that branch off arterioles

- Only have tunica intima layer

- "Exchange vessels"

- Function: nutrient, gas & fluid exchange

What are Capillaries? Describe them too.

into capillary beds

How do Capillaries arrange?

very extensive capillary beds

Tissues that have high metabolic needs (like muscle tissue) have what?

more blood flow --> more oxygen & nutrients

Large capillary beds means what?

circular muscles that regulate the level of blood flow into capillary beds.

What are Precapillary Sphincters?

- Open: blood flow throughout the bed

- Closed: blood flow only through the bed's metarteriole

Open vs Closed Precapillary Sphincters?

- A blood vessel that connects an arteriole to a venule directly (skipping the capillary bed)

- This process is known as vascular shunting

- Vascular shunting is critical to blood redistribution throughout the body

What is a Metarteriole? Describe it too.

1. Continuous Capillaries

2. Fenestrated Capillaries

3. Sinusoid Capillaries

What are the 3 types of Capillaries?

Locations: brain, lungs, muscles, skin, connective tissues

Structure: continuous layer of endothelial cells with tight junctions

Permeable to: water, ions, glucose

Identify the Locations, Structure, and what Continuous Capillaries are Permeable to.

Locations: kidneys, small intestines, endocrine glands

Structure: small fenestrations (windows) and smaller intercellular clefts

Permeable to: water, ions, glucose, small solutes

Identify the Locations, Structure, and what Fenestrated Capillaries are Permeable to.

Locations: liver, spleen, bone marrow

Structure: large fenestrations & large intercellular clefts

Permeable to: water, ions, glucose, small solutes, proteins, blood cells

Identify the Locations, Structure, and what Sinusoid Capillaries are Permeable to.

the process of bringing things into or out of a blood vessel

What is Capillary Exchange?

1. Diffusion

2. Transcytosis

3. Bulk Flow

What are the 3 methods of Capillary Exchange?

- Substances move from high to low concentration

- Diffusion through cells: water, gases, steroids

- Diffusion through fenestrations / clefts: water, ions, glucose, amino acids

- Facilitated or simple

Describe Diffusion.

- Substances move using endocytosis or exocytosis

- This is used for large things like hormones or antibodies

Describe Transcytosis.

- Substances move from high to low pressure

- Many ion / molecules move at same time in same direction, making this process faster than simple diffusion

Describe Bulk Flow.

from Lumen to Interstitial Fluid

Where does Filtration move stuff from and to?

from Interstitial Fluid to Lumen

Where does Reabsorption move stuff from and to?

pushes away from the heart and seen in Filtration

Hydrostatic pressure creates a motion in what direction and is seen in what process?

pulls toward the heart and seen in Reabsorption

Osmotic pressure creates a motion in what direction and is seen in what process?

BOTH!

What kind of pressure does Blood (capillary) have? (Hydrostatic/Osmotic?)

- Blood Hydrostatic Pressure --> push water OUT of vessels

- Blood Colloid Osmotic Pressure --> push water INTO vessels

Explain what both Blood Hydrostatic and Blood Colloid Osmotic Pressure do.

caused by heart stroke volume inside vessel lumen...this pushes water OUT of vessel (filtration)

Explain how Blood Hydrostatic Pressure is caused.

caused by proteins, ions & formed elements inside vessel...this pulls water INTO vessel (colloids suck) (reabsorption)

Explain how Blood Colloid Osmotic Pressure is caused.

True!! This also has minimal influence.

Interstitial fluid has both kinds of pressure. True or False?

Interstitial Hydrostatic = push water out of tissues into vessels

Interstitial Colloid Osmotic = pulls water into tissues out of vessels

Explain Interstitial Hydrostatic Pressure & Interstitial Colloid Osmotic Pressure.

- 4 types of pressure

- How does capillary hydrostatic pressure compare to interstitial hydrostatic pressure?

- How does plasma colloid pressure compare to interstitial colloid pressure?

Net filtration pressure considers the effects of how many types of pressures? What questions do we need to consider?

1. Capillary Hydrostatic Pressure (Pc)

2. Interstitial Fluid Hydrostatic Pressure (PIF)

3. Osmotic force due to plasma protein concentration (OPC)

4. Osmotic force due to interstitial fluid protein concentration (OPIF)

What are the 4 types of pressure that need to be considered for Net Filtration Pressure (NFP)?

(Pc + OPIF) - (PIF + OPC)

What is the Net Filtration Pressure (NFP) formula?

filtration exceeds reabsorption

What happens in the venous end in net filtration?

excess is taken uo by the lymphatic vessels

What happens when filtration excess reabsorption?

an increase in interstitial fluid that does not drain

What is Edema?

Typically, lymphatic vessels near capillary beds collect fluid that is not reabsorbed by the bed

- If fluid lvls are too high, the lymphatic vessels can't keep up

Describe Edema.

problems with hydrostatic & osmotic pressures

Edema can be caused by problems with what?

- Capillary hydrostatic pressure is too high --> water pushed out of vessels

- Interstitial osmotic pressure is too high --> water is pulled out of vessels

- Plasma osmotic pressure is too low --> water is NOT pulled back into vessels

- Decreased drainage of interstitial fluid through lymphatic vessels

Describe how Edema can be caused by problems w/ hydrostatic & osmotic pressures

normal diffusion of gases, nutrients, and wastes

What does Edema prevent?

of right-side congestive heart failure

Peripheral edema is a symptom of what?

it enters venules, which combine to form veins

Blood that leaves the capillary bed enters where? What happens after?

they're wider and more numerous than arteries

How do veins compare to arteries in terms or width and quantity?

1. Valves --> these prevent blood backflow

2. The Skeletal Muscle Pump --> contracting muscles squeeze veins & push blood back toward the heart

3. The Respiratory Pump --> decreased thoracic pressure from inhaling pulls blood up

4. Sympathetic Venoconstriction --> epinephrine increases smooth muscle contraction

Describe the process how Veins need "help" getting blood back to the heart.

alternate routes for blood to flow to or from organs

What are Anastomoses?

ensure that tissues receive a constant flow of oxygen-rich blood, even if an artery is blocked

What do Arterial Anastomoses do?

allow blood to "skip" capillary beds during vascular shunting

What do Arteriovenous Anastomoses (Metarterioles) do?

ensure that all oxygen-poor blood returns to the heart, even if one vein is blocked or removed

What do Venous Anastomoses do?

the study of how blood moves through blood vessels (perfusion)

What is the definition of Hemodynamics?

1. Pressure - how strongly does the blood want to get through?

2. Resistance - how hard is it for the blood to get through?

3. Velocity - how fast does the blood get through (cm/sec)

4. Flow - what volume of blood moves through a given cross-section (ml/min)

What are the important aspects of Hemodynamics?

- Velocity is the distance a fluid moves within a unit of time (cm/sec)

- Flow is related to velocity (F= V x r^2) where V is velocity times the radius of the vessel.

- Also, Flow is Pressure divided by Resistance (F = deltaP/R) measured in ml/min

aka velocity = speed of fluid, flow is volume of liquid

How are Velocity and Flow different?

pressure is proportional to flow

In a condition of constant resistance, how are pressure and flow related?

1. Laminar - The velocity of blood flow is highest in the center and decreases near the walls.

2. Turbulent - chaotic, irregular fluid particle movement with swirling eddies

What are the 2 types of Flow? Define them too!

increases turbulent flow due to increased resistance

What does Arterial Plaque increase?

F = deltaP/R

aka Flow = pressure change/resistance

What is the formula for Flow?

1. Blood Viscosity

2. Vessel Radius

3. Vessel Length

What is resistance determined by?

- How THICK is the blood?

- Thicker blood = more resistance

- Thinner blood = less resistance

Describe Blood Viscosity.

- How wide is the blood vessel? (greatest effect on resistance)

- Wider vessel = less resistance

- Narrow vessel = more resistance

Describe Vessel Radius.

- How far does the blood have to travel?

- Longer vessel = more more resistance

- Shorter vessel = less resistance

Describe Vessel Length.

(Blood Viscosity x Vessel Length) divided by Radius

What is the formula for Resistance?

all vascular resistances

What's Total Peripheral Resistance (TPR)?

Arteries/Veins - low TPR

Capillaries/Venules - high TPR

Arterioles - highest TPR ("resistance vessels")

Describe the TPR for the following:

- Arteries/Veins

- Capillaries/Venules

- Arterioles

R = (blood viscosity x vessel length) divided by area (vessel radius)^4

What's the Total Peripheral Resistance Formula?

speed that blood travels through blood vessels (cm/sec)

What is Velocity?

decreases it

What does resistance do to blood velocity?

surface area increases

What happens every time blood vessels branch?

Increased surface area = increased resistance

Increased surface area = DECREASED velocity

What do we get from increased surface area due to blood vessels branching?

capillaries do

What has the greatest surface area of all the body's blood vessels?

blood moves the most slowly in these vessels, allowing for sufficient nutrient & gas exchange

Describe what Capillaries having the greatest surface area does for blood.

a measurement of the force of blood pressing on the blood vessel walls

What is Blood (pulse) pressure?

the pressure varies when the heart is in systole vs. when it's in diastole

What's special about Blood Pressure in arteries?

BP = SP - DP

How do we calculate Blood Pressure?

MAP = DP + (1/3 BP)

How do we calculate Mean Arterial Pressure?

flows from high to low pressure vessels

How does blood flow pressure wise?

It's how much a blood vessel can stretch.

- stretching can decrease pressure in vessel

What is Compliance and how does it affect pressure?