The blood vessels are TUBES through which blood flows to all parts of the body.  These tubes carry the blood from the heart to the capillaries and back to the heart.  The function of the vessels is to contain the blood, and transport it (and the contents) from the heart, to the tissues, where nutrients etc are exchanged, and to then transport blood back to the heart.

There are three sections of 'tube':
   1. Arterial side - Function: carry blood under high pressure, from the heart to the capillaries.
   2. Capillaries - Function: exchange substances between the blood and the tissues.
   3. Venous side - Function: carry blood under low pressure, from the capillaries, back to the heart.

Remember: the capillary is where the most important event occurs: EXCHANGE of nutrients between the blood and the tissues!

The vessels are a continuous tube (loop).  Blood flows within the tube away from the heart to the tissues (inside capillaries), then, STILL INSIDE THE TUBE, back to the heart. 
    - RBCs and the blood proteins never get outside of the tubes (vessels).  
    - At the capillaries, water, nutrients, wastes, hormones, etc are exchanged between the tissues
       and blood.  These substances must cross the wall of the capillary.  The capillary keeps RBCs and
       blood proteins inside the vascular system, while allowing O2, CO2, nutrients, wastes, etc to enter
       or exit.

The wall of the vessels is composed of three parts:

Tunica interna (aka. t. intima) - a simple squamous epithelium, lines the lumen and is in contact
       with the whole blood inside the vessel.  Tunica = layer or coat. 
Tunica media - composed of elastic connective tissue and smooth muscle.  This 'middle coat' is the
       functional unit for the vessels: the function of a specific vessel is determined by the relative amount
       of smooth muscle and/or elastic connective tissue in the t. media.
Tunica externa (aka t. adventitia) connective tissue, protein fibers connect the vessel to the adjacent
       tissues.

What is the function of the arterial side of the vascular system?
What is the function of the capillaries?
What is the function of the venous side of the vascular system?
Where is the highest blood pressure found?
How does blood pressure affect the structure of the t. media?
Which vessel, artery or vein, has the thinnest wall?
   Why?
Which vessel, artery or vein, has the thickest wall?
  Why?

Arteries: are Efferent - carry blood FROM the heart to the capillaries (peripheral tissues).

Arteries have thick walls with lots of smooth muscle and elastic connective tissue. The larger the artery diameter, the more elastic connective tissue and less smooth muscle. The smaller the artery diameter, the more smooth muscle and less elastic tissue.  Large diameter arteries with elastic CT, withstand and absorb high blood pressure.   Small diameter arteries with smooth muscle, vasoconstrict and vasodilate for control of blood pressure and blood flow.

The function of LARGE arteries (such as the Aorta) is to absorb very high blood pressure, therefore the t. media is almost entirely elastic connective tissue.

Arterioles are the smallest arteries. They have LOTS of smooth muscle in the walls, and almost NO elastic connective tissue. The smooth muscle functions for vasoconstriction and vasodilation.
   Define vasoconstriction and vasodilation.

The function of small arteries and arterioles is to maintain blood pressure and control blood flow to individual tissues, therefore, the t. media is mostly smooth muscle which can contract and impede flow, or relax and allow blood flow.

Veins: are Afferent – carry blood TO the heart from the capillaries.

Thinner walls with very little smooth muscle and have valves.
What is the function of valves?

       Veins have thinner walls than arteries because the blood pressure in veins is low.

Capillaries: the SMALLEST blood vessels; the location of EXCHANGE of nutrients between blood and interstitial fluids. The walls are a simple squamous epithelium. One layer of squamous cells – therefore ions and molecules in the blood that are diffusing out of the blood into the interstitial spaces only have to pass through the cell membrane next to the blood into the epithelial cell and through the cell membrane on the other side to get to the interstitial fluid. Ions and molecules diffusing from the interstitial spaces into the blood also pass through these two CMs.

What are the 6 basic nutrients? (Review Chapter 17 Metabolism)
  Of the 6 – what are the two main groups?
    What is the function of carbohydrates and lipids?
         What is the function of O2 with respect to the function of carbohydrates and lipids?
    What is the function of minerals and vitamins?
    What is the function of water as a nutrient?

What is an epithelium? (Review Chapter 4, Tissues).
   What are the two characteristics of an epithelium?
      Describe the two types of epithelium based on numbers of cells.
        Describe the cell shapes and the function of each shape.

List the three types of muscle.  (Review Muscles, Tissues)
   What are the characteristics of smooth muscle?
     Where is smooth muscle found?

     Compare Smooth Muscle to Cardiac and Skeletal. 
       Where is each type found?
          What is the main function of each type of muscle?

Blood pressure is the force of the blood pushing on the walls of the vascular system.

Blood moves through the vascular system from area of HIGHER blood pressure (BP) to an area
         of lower blood pressure. 
    When the heart contracts (systole), the heart is squeezing the blood inside the heart the the blood
          pressure is highest inside the heart - therefore, blood moves to an area with lower BP - the
          arteries (valves prevent backflow into the veins).
    When the heart relaxes (diastole), there is NO pressure on the blood inside the heart, and the
         blood pressure is lowest inside the heart - therefore, blood moves from the veins (vena cavas)
         into the heart.

Blood moves from High BP to Low BP.

Cardiac muscle contraction creates High BP in the ventricles, and blood flows into the arteries.  Each time the heart beats (contracts) a PULSE of blood pushes into the arteries - this Pulse of blood pushes the blood ahead, on through the vessels.  As blood flows into smaller and smaller diameter arteries, it moves against increasing resistance.

Vasoconstriction and vasodilation of the arterioles and the precapillary sphincter control blood flow into the capillary bed.

The capillaries are the smallest diameter vessels - and therefore, the RESISTANCE to blood flow is high.  Most of the Blood pressure produced by ventricular contraction is used just to push blood through the arteries and through the capillaries.

Downstream of the capillaries are the veins.  Blood steadily flows into the veins under very little pressure, therefore, veins have valves to prevent back flow.  The diameter of the veins (into which blood is flowing) steadily increases - therefore, the blood is flowing against decreasing resistance.
     Skeletal muscles adjacent to the veins contract and 'squeeze' the veins.  This causes 'pressure'
          inside the vein and blood moves along toward the heart. 
     Valves prevent backflow. 
     There is a steady flow of blood entering the veins from the capillaries, which pushes blood along
         the venous side.

These phenomena produce 3 (three) areas of blood pressure:
   Arterial blood pressure - pressure in the arteries and arterioles.  Typically the highest BP outside
         the heart.
   Capillary blood pressure - pressure in the capillary beds - typically lower than arterial, but higher
         than BP in veins.
   Venous blood pressure - typically the lowest BP, outside the heart.

   Remember: blood flows INTO the atria and ventricles of the heart while the heart is relaxed - therefore, during diastole, the BP INSIDE the heart is lower than that in the veins.  The HEART has both the highest cardiovascular BP (during ventricular systole) as well as the lowest cardiovascular BP (during cardiac diastole -both the atria and ventricles are relaxed at the same time).

 Remember the heart sounds?  S1 and S2?
Lubb..Dupp........ pause......... Lubb.. Dupp....... pause...... and so on...

During the 'pause' - both the Atria and Ventricles are 'relaxed' and Preload is filling the ventricles and then the atria - on both the right and left side.

Systolic pressure is the MAXIMUM pressure during ventricular contraction.

Diastolic pressure is the minimum pressure during cardiac relaxation.

Normally, we describe blood pressure as: systolic over diastolic : eg. 120 over 80

Pulse Pressure: the difference between Systolic and Diastolic Pressures.  Usually about 40.

Resistance to blood flow in the Arterial side helps maintain BP and control blood flow to the tissues.  There are 3 (three) types of resistance:
   Viscosity - usually constant.  Dehydration can cause blood to become more viscous, but is not normal.
   Turbulence - usually constant.  Plaques or other structures extending from the wall of the vessel, cause
        'eddy's' and impede blood flow.  Again, not normal in a healthy vascular system.
   Vascular resistance - Changeable - due to vasodilation and vasoconstriction.  Vascular resistance
        is the method used by the body to maintain blood pressure and control blood flow to the tissues.

Which two types of resistance are NORMALLY constant?
Which type of resistance is NORMALLY variable?
   How does the body use this variability to maintain homeostasis of blood pressure?

What structure controls blood flow into the capillary bed?
   What is a sphincter?
   How do the arterioles vasoconstrict?

Describe Systolic, Diastolic and Pulse Pressure.

O2 and CO2 are lipid soluble –
    What kind of molecule are they? (hint: polarity and hydrophilic vs hydrophobic)

What do these molecules have to pass through to go from the blood to the interstitial spaces?
    Or from the interstitial spaces into the blood?
        How does being lipid soluble help the diffusion of these molecules?
           (hint: what is the CM made up of? - Review Chapter 3, Cells)
               What is the function of the CM?

These molecules are dissolved in a liquid – they are no longer in gas form. The molecules diffuse from one area to the next.
  What is diffusion?
    Which way does O2 go?
    Which way does CO2 go?
       Therefore, where is the highest concentration of O2, of CO2?
          Why is O2 low in the mitochondrium?
             Why is CO2 high in the cell? (Hint: describe aerobic cellular respiration).

There are 4 (four) forces that move nutrients into and out of the capillaries:
    Filtration - capillary BP is greater than Osmotic pull.
    Diffusion - moves molecules and ions from areas of high concentration to low concentration. 
         Any molecule with a higher blood concentration will diffuse OUT of the capillary.  Any molecule
         with higher interstitial fluid concentration will diffuse into the capillary.
    Active Transport - movement of a molecule or ion AGAINST the concentration gradient - using
         energy.  There are lots of active transport mechanisms to move specific nutrients into or out of
         capillaries and/or cells.  Active transport creates a highly concentrated solution -and water flows
          into the tissues due to osmosis.
    Osmosis - the diffusion of water through a semipermeable membrane.
 

Filtration - The capillary wall is a simple squamous epithelium.  There are tiny 'holes' in the wall called Finestrae.  Capillary BP pushes liquid against the wall of the capillary and OUT, through the finestrae.  The H2O molecules and other SMALL molecules are forced out of the capillary and into the interstitial spaces.  Because small ions, molecules and water are forced out of the plasma, leaving behind the larger RBCs, WBCs, platelets and large blood proteins, the blood is FILTERED. 

Diffusion - passive movement of molecules and ions along their concentration gradient.
Active transport - ENERGY used to concentrate molecules and ions.

Osmosis - passive movement of water - to an area that is highly concentrated with solutes.  After the water and small molecules have been forced out of the capillaries by high BP on the arterial side of the capillary bed, the blood on the venous side of the capillary bed is concentrated and osmotic pull is stronger than the BP, therefore, water osmoses back into the vascular system.

Water and small molecules are continually forced out (filtered!) of the capillaries into the extracellular spaces, and then water osmoses back into the capillaries.  This action very efficiently moves small nutrients out of the blood - making them available to the tissues.  Excess nutrients diffuse back into the vascular system, too.

These are the Cellular Transport mechanisms introduced in Chapters 3. 

Why do O2 and CO2 move into or out of the blood?
    Hint: What is the electrostatic charge of O2 and CO2?

What two (2) forces cause H2O to move into or out of the blood/vascular system?
What forces cause other solutes to move into or out of the blood/vascular system?

What is Edema?
  How does 'too little' osmotic pull inside the blood system cause 'edema'?

Which transport mechanisms function at the capillary?

Describe the Sounds of Korotkoff

These are the 'noises' that are produced by a blood pressure cuff.
The pressure cuff is inflated with AIR, until the air pressure is strong enough to stop blood flow through the artery.  (what is the normal systolic BP? ... 120? - so inflate the cuff to 150 or so then 'listen')

If the air pressure is strong enough to 'cut off the blood flow', then there will be no noise in the artery. No blood flow = no noise. Release a small amount of air, decreases the pressure.  When the air pressure is just slightly LESS than the systolic BP, then a small amount of blood will SPURT passed the cuff when the ventricles contract.  The blood will only pass the cuff for that period of time when the blood pressure is greater than the air pressure in the cuff.

Blood will 'spurt' passed the cuff until the air pressure is just less than the diastolic pressure. At this point, there will be no more 'spurts' - since the blood pressure is always greater than the air pressure - i.e. the air pressure no longer is strong enough to 'cut off' the blood flow.

Recording the air pressure at the point which the first 'spurts' are heard - is the systolic pressure.
Recording the air pressure at the point which the last 'spurts' are heard -i.e. the noise becomes constant - is the diastolic pressure.

What are the medics actually measuring with the traditional sphygmomanometer (blood pressure cuff)?
   Air pressure in the cuff - it is an ESTIMATE of the Blood pressure.

Describe Cardiovascular regulation

The three (3) goals of cardiovascular regulation is blood flow:
   1. to the right place
    2. at the right time
     3. with out affecting blood flow to the vital organs - heart, lungs, nervous system.

If you need to run, you want your blood (and all the resources - O2, nutrients, energy) to go to your muscles - not your liver, pancreas, etc.

You want your blood to go to the muscles WHEN you need energy, O2, etc in the muscles.

You want blood to go to the vital organs continually.
 

The ANS controls blood flow via control centers in the Brain Stem.
  this is the nervous system - primarily SHORT TERM rapid control.

The endocrine system uses
    - ADH, Aldosterone, Renin, and ANP to control blood volume
    - erythropoietin to control RBCs.
    - norepinephrine, epinephrine, and acetylcholine to control:
         - peripheral blood flow
         - heart rate and therefore - Cardiac Output.
  This is the endocrine system - primarily LONG TERM control. 

Local controls - at the tissue level, prostaglandins (local hormones) control the precapillary sphincters and vasodilation or vasoconstriction of the smallest arterioles.
    Immediate, local fine-tuning of blood flow.

Baroreceptors - sense blood pressure changes in the heart, vascular sinuses, etc - send info to the CNS/ANS.
Chemoreceptors - sense pH, O2, and CO2 concentrations in blood, cerebrospinal fluid, and
    peripheral tissues.  Send info to the CNS/ANS.

Exercise
  Light: causes vasodilation and activation of the venous reserve - Frank Starling's Law.
  Heavy - activates the ANS - Sympathetic NS to get vasoconstriction and therefore increase BP, HR,
     and Cardiac Output.  This increases blood flow to the tissues - more efficient delivery of nutrients,
     O2 to the tissues.

Hemorrhaging:   local hemostasis fails (blood is being lost through a hole in some vessels)
Small losses (less than 20% of total blood volume): activate the venous reserve to maintain Cardiac Output.
     How much total blood does a normal person have?
        How much is 20% of 5 liters?

Larger losses:  increase heart rate (highest is about 200 bt/min), vasoconstriction, release ADH, Renin, and Aldosterone.

Again, - these actions preserve Frank Starling's Law.

As long as the body can maintain an appropriate amount of blood going into the heart, there will be sufficient blood pumped out of the heart to maintain 'life'.

When so much blood is lost that the amount in cannot be sustained - the amount pumped out decreases - and the delivery of nutrients to the tissues decreases below that point necessary to maintain metabolism in the cells - death.

Describe blood supply to and from the brain

There are 4 (four) arteries that send blood to the brain.
     Two (2) Vertebral arteries run parallel to the cervical vertebra, enter the cranium through the
          foramen magnum and fuse to form the basilar artery.
     The 2 (two) internal carotid arteries branch off the common carotids (1 on each side),

  The Basilar and 2 internal Carotid arteries fuse to form the Circle of Willis - aka: cerebral
     arterial circle.

The Circle of Willis is a major anastomose - it ensures that blood can flow to all parts of the brain.

At the capillary level - the Blood-Brain Barrier controls the exchange of substances between the blood and the nervous tissues.

Venous blood enters the cerebral sinuses, flows into the jugular veins and then into the brachicephalic veins and then the superior vena cava.

List the arteries that supply blood to the CNS.
  What is the Circle of Willis?
    Why is it so important?
       What is another name for it?
  What is the blood-brain barrier?  Review Chapter 4, Tissues.
List the veins that drain blood from the CNS.

Describe the Hepatic Portal System.

The function of the Hepatic Portal System is to transfer nutrient rich blood from the digestive capillaries to the Liver, so that lobules of the liver can 'clean and detoxify' the blood.

The lobules of the liver are made up of a central artery, sinusoids and hepatocytes.

Blood flows into the capillaries around the digestive system an absorbs the nutrients from the food in the digestive tract.  These nutrients potentially are toxic to the other body cells.  Therefore, the blood is first sent to the LIVER, to be 'cleaned' and chemically filtered by hepatocytes.

The digestive capillaries drain blood into the Hepatic Portal Vein, which carries the nutrient-rich blood to the liver.  There, the blood enters the Lobules of the liver, and the sinusoids.  Hepatocytes are in direct contact with the blood - absorb nutrients and other substances from the blood, and chemically modify, detoxify, store, or otherwise process those subtances so that the substances can be used by the body or excreted.

Remember: the sinusoids are 'primitive capillaries'. Review Chapter 4, Tissues
Compare and contrast Sinusoids, Capillaries, and the Blood brain barrier.

What are hepatocytes?
  What is the function of the hepatocytes?
     What is the mechanism by which hepatocytes 'clean' blood?
 

Describe Fetal Circulation

The developing fetus obtains all its nutrients from the mother's blood and disposes of wastes into the mother's blood.

The 2 (two) umbilical arteries carry blood from the baby to the placenta.
The Placenta is a massive capillary bed that exchanges wastes from the baby into the mother's
     blood and O2 and nutrients from the mother's blood to the baby's blood.
The umbilical vein (one) carries nutrient rich blood from the placenta to the baby and enters the
     baby's body at the ductus venosus, which passes the blood into the inferior vena cava.

The blood enters the Right Atrium.

NOW - since the lungs are non-functional (no air to breath in the womb) - MOST of the blood BYPASSES the fetal lungs.

From the Rt Atrium, some blood passes through the foramen ovale - a hole in the interatrial septum - into the Left Atrium (bypasses the pulmonary circuit).
Some blood goes into the right ventricle and is pumped into the pulmonary trunk.  From the pulmonary trunk SOME blood goes into the pulmonary circuit - but most goes through the Ductus Arteriosum into the Aortic Arch (i.e. into the systemic circuit).

The function of the Foramen Ovale (in the heart) and the Ductus Arteriosus is to bypass the pulmonary circuit.

At birth - IMMEDIATELY - the foramen ovale and the ductus arterosus close, and become the fossa ovale and ligamentum arteriosum, respectively.

Why is it ok to bypass the pulmonary circuit?
What is the function of the ductus venosus?
What is the function of the ductus arteriosus and the foramen ovale?

 

How does aging affect this system?

Define:
   arteriosclerosis.
   atherosclerosis
   aneurysm

Atherosclerosis and arteriosclerosis result in stiff inelastic arteries that are less able to control blood pressure than supple, elastic vessels.
 

Remember – all the systems have to work together to maintain homeostasis.

 

Arteries
to the HEAD:

• Right common carotid
• Left common carotid
• Vertebral arteries
• Circle of Willis - Cerebral Arterial Circle

To the UPPER EXTREMITIES:

• Right subclavian
• Left subclavian
• Brachiocephalic
• Axillary
• Brachial
• Ulnar
• Radial
• Palmar arches
• Digital arteries

• Celiac
• Renal

• Common ilac
• Femoral
• Popliteal
• Posterior tibial
• Anterior tibial
• Peroneal
• Plantar arch

Name the major systemic veins and the parts of the body they drain of blood
Veins
From the HEAD

• External jugular
• Internal jugular
• Vertebral

• Brachiocephalic
• Subclavial
• Axillary
• Cephalic
• Brachial
• Basilic
• Median cubital
• Median antebrachial
• Ulnar
• Palmar venous arches
• Digital veins

• Hepatic vein
• Renal

From the Lower extremities

• External iliac
• Internal ilac
• Femoral
• Great saphenous
• Popliteal
• Small saphenous
• Posterior tibial
• Anterior tibial
• Peroneal
• Dorsal venous arch
• Plantar venous arch

Hepatic Portal System
Hepatic portal vein
Digestive capillary beds
Sinusoids in the Liver

• Umbilical arteries
• Umbilical vein
• Ductus venosus
• Foramen ovale
• Ductus arteriosus
• Ligamentum arteriosum