--Blood vessel layers

--any vessel that has a wall w/ 3 layers

--cavity

--inside space of the vessel

--Outermost layer.  Forms a connective tissue covering around the vessel.

--The connective tissue here tends to blend with neighboring tissues.  This stabilizes and anchors the vessel.

---network of small arteries in the tunica externa.

--the blood supply of a blood vessel

**large vessels with a diameter from 1 cm to 2.5 cm.  Ex: Pulmonary artery and aorta.

a. Transport large volumes of blood from the heart. 

b. During ventricular systole, blood is ejected into elastic arteries and they expand.  During ventricular diastole, elastic arteries recoil (because of their elasticity) and return to their original size.

 c. The expansion of elastic arteries cushions the sudden rise in blood pressure during ventricular systole and their recoil slows the drop in pressure during ventricular diastole

d. This allows blood flow within the arteries to be continuous even though blood flow from the heart is discontinuous.

--Bring blood to all areas of the body

--Distributes blood to the body's skeletal muscle and organs.  Ex: external carotid arteries of neck, brachial arteries of arm and femoral arteries of thigh.

--Very small, microscopic

--internal diameter of 30m m or less.  The tunica media consists of six or less layers of smooth muscle.  The smallest ones do not have a tunica externa.

Smooth muscle of arterioles is usually partially constricted. 

--always somewhat toned

--exchange vessels, slow flow of blood

--blood vessels that allow for the exchange of nutrients and gases to the interstitial fluids due to tissue anatomy; blood flows at a slow velocity through them.  They connect the arteries to the veins.  Millions of them are found in the body.

--capillary lining is complete.  Materials can move in and out of the blood through endothelial cells (diffusion, pinocytosis) or between cells through intercellular gaps, which prevent the movement of large substances from the plasma.  Most common type of capillary. Can be found in skeletal muscle.             

--no openings or gaps, complete

--capillaries with small pores within endothelial cells.  The pores allow for rapid exchange of water and solutes (even small proteins).  Located in areas in need of rapid exchange.  Pinocytotic transport is also present.  Can be found in endocrine glands (release and rapid diffusion of hormones) and within the kidney (for rapid filtration of blood).

--pourous, lots of openings or gaps, like a collander

--promotes transport of materials-- H2O, small proteins

--Found where you need to move products more quickly

--not typical

--wide-open, flattened specialized fenestrated capillaries.   Allows for the free exchange of water, solutes, large proteins and formed elements. Blood moves through sinusoids slowly.  This allows for absorption and secretion into and out of capillaries.  Can be found in the liver, spleen and bone marrow.

--allow us to regulate which capillaries are open

--smooth muscle encircling an opening; contract to close; relax to open

--simplest and smallest vein

--collect blood from capillary beds

--may resemble a capillary

--collect blood from venules

--they have a thin tunica media with few smooth muscles

--not many of them

--Collect blood from medium-sized veins.  All layers present.  Ex: superior vena cava and inferior vena cava.

--2 leaflets in veins

--help deal with pressure of gravity--pulls blood toward the feet

1. Structure: folds of the tunica interna

2. Function: prevent backflow of blood into the capillary network ; keeps blood flowing in one direction.  In veins, blood pressure is below the force of gravity.  Also important are the skeletal muscle contractions that constrict veins in cycles so that blood will be pushed toward the heart.

--70% in systemic circulation

--55% in systemic veins

--There is approximately 5 liters of blood w/i the closed circulatory system (including the heart)

--Anastomosis

--Arteriovenous shunt

--Portal System

Blood flows through two capillary beds.  Ex: portal system (portal vein delivers blood to another organ before blood returns to the heart – artery, capillary bed, portal vein, capillary bed, vein)

--Can be between 2 arteries or 2 veins

Net movement of molecules from areas of high concentration to areas of low concentration.  This occurs most readily in areas where the concentration gradient is large, the distances involved are small and the substance, ion or molecule is small.

--occurs in capillaries through: cell membranes, intercellular clefts, cell membrane channels, pores of fenestrated capillaries, and openings in sinusoids

diffusion of contents through a membrane by pinocytosis

--endocytosis/exocytosis

refers to movement of fluids and their solutes in one direction down a pressure gradient. 

--moving water and what's dissolve in it

the movement by bulk flow through the openings in the capillary (for example: between intercellular clefts or pores of fenestrated capillaries) into the interstitial fluid. 

--movement out of capillary

*hydrostatic pressure

the movement by bulk flow from the interstitial fluid through the capillary and into the blood.--still requires a gradient (force)

--movement into capillary

*osmosis

--causes filtration

--pressure on water

The physical force exerted by a fluid on a structure.  Hydrostatic pressure forces water from a high to low pressure. 

the difference between the net hydrostatic pressure and the net colloid osmotic pressure.

(HP_b – HP_if).   

                        Arterial end: 35 mmHg – 0 mmHg = 35 mmHg

                        Venous end: 16 mmHg – 0 mmHg = 16 mmHg

the difference between COP_b  and COP_if. 

                        Both arterial and venous end:  26 mmHg – 5 mmHg = 21 mmHg