Systemic Circulation-Starting in the left atrium, blood travels through the mitral valve into the left ventricle then through the aortic valve into the aorta.

From here the blood can go into one of three areas.

·         First is to the brain via either 2 of the internal carotid arteries or 2 vertebral arteries. These will lead into either the anterior, middle or posterior arteries which go to both sides of the brain. The arteries lead to arterioles to capillaries to venules to veins then to the superior vena cava which empties into the right atrium.

·         Second is to the heart or coronary circulation via the ascending aorta to the coronary arteries to capillaries to coronary veins to the coronary sinus which empties into the right atrium

·        Third is to the rest of the body where the arteries go to arterioles to capillaries to venules to veins then travel to the inferior vena cava which empties into the right atrium.

            The transfer of nutrients and gases takes place in all areas in the capillaries where O2 is delivered and CO2 is picked up to be transported back to the lungs.

Once blood from all areas reaches the right atrium it will pass through the tricuspid valve into the right ventricle through the pulmonary valve into the pulmonary trunk. Here it will go through the right and left pulmonary arteries to either the right or left lung. The CO2 picked up in the capillaries is exchanged here for a fresh load of O2 through inhale/exhale process. The blood then travels through the right or left pulmonary veins back to the left atrium where the entire process starts all over again.

• damage to the blood vessel endothelium

• abnormal blood flow (may be stasis or turbulence)

• hypercoagulability (a condition of increased tendency of blood to coagulate)

Explain some key differences between arteries and veins 

There are 4 key differences:

1)      Arteries carry blood away from the heart and veins return blood to the heart

2)      The lumen of a vein is larger than an artery lumen, and the media & intima of the vein are thinner compared to arteries

3)      Blood pressure within the vein is considerably lower than that of the artery

4)      Veins have valves to prevent backflow of blood; arteries do not have valves

Describe the three layers of a blood vessel? 

Jimmy E  Describe the three mechanisms that contribute to normal hemostatis. 

-Vascular Spasm

-Platelet plug formation

-Coagulation or blood clotting

usually the result of an injury to the blood vessel and results in the smooth muscle layer of the vessel wall to contract which narrows the blood vessel and reduces blood flow.  The spasm can last for several minutes or hours and buys time for the other stages of hemostasis to begin to work.  Remember that this stage is temporary and without the completion of the other stages bleeding will resume and can become life-threatening.

describe platelet plug formation

.  Normally platelets circulate freely in the blood and do not stick to the endothelium.  However during Platelet Plug Formation, these platelet come in contact with the damaged blood vessel and we have platelet adhesion, activation, and aggregation resulting in a platelet plug.  During adhesion- platelets stick (or adhere) to the damaged area and are reinforced by molecular glue called von willebrand factor- ensuring that the attaching platelets can withstand the strong current of normal blood flow.  Once anchored at the injury site the platelets become activated-why its called activation- and they change in structure to finger-like projections-allowing them to interact  with one another and playing a key part in the aggregation phase where these finger-like projections reach out and recruit other platelets free-floating in circulation to join together at the injured site and a sticky mass known as the platelet plug.

describe coagulation  

Initially the platelet plug is loose but during this stage a series of enzymatic reactions, called the cascade, where specific clotting factors activate the next enzyme in a fixed sequence, ultimately where fibrin, an insoluable protein, stabilizes the platelet plug into a sturdy clot. 

There are two atrioventricular valves (mitral and tricuspid) and two semilunar valves (aortic and pulmonary).  These valves make sure that blood flows in only one direction through the heart.  Tricuspid valve is located between right atrium and right ventricle.  Mitral valve is located between left atrium and left ventricle.   The pulmonary valve sits between the right ventricle and the pulmonary trunk.  The aortic valve seperates the aorta and the left ventricle. 

Red blood cells, white blood cells and platelets.  Red blood cells transport oxygen and carbon dioxide bound to hemoglobin.  White blood cells defend the body against damage by bacteria and viruses.  Platelets play a crucial role in normal blood clotting.  55% of blood is blood plasma and 45% are the formed elements.

• arteries: carry oxygenated blood away from the heart toward other organs

• arterioles: smaller vessels that regulate the flow of blood from the arteries

into capillaries

• capillaries: the smallest vessels; connect arterioles to venules; the exchange of

substances (eg, oxygen, carbon dioxide) between blood and body tissues occurs

through capillary walls

• venules: small vessels that link capillaries to veins and begin the return of blood

back to the heart

• veins: return deoxygenated blood from the body tissues to the heart

The intrinsic is blood trauma or damage to the vessel and is triggered by activators in the blood.  The Extrinsic is tissue trauma.  At factor 10A they meet and the common pathway begins and completes the coagulation cascade.

Plasmin  is the major enzyme of the fibrinolytic system. It dissolves the clot by breaking down the fibrin threads within the clot. By doing this, it inactivates fibrinogen, prothrombin and factors V and XII; which are essential in the coagulation cascade.

The volume of blood ejected by the heart in a specified period of time is known as

cardiac output (CO). It is usually expressed in liters per minute. Cardiac output is

calculated by multiplying heart rate (beats/minute) and stroke volume (liters/beat).

How the cardiac output is distributed into circulation depends on many factors,

including:

• the pressure difference that drives blood through tissues: the greater the

pressure difference between areas, the greater the blood flow

• the resistance of blood flow in specific tissues: the greater the resistance, the

smaller the blood flow

Blood pressure is the pressure exerted by blood on the walls of a blood vessel and

is generated by the contraction of the ventricles. Systolic blood pressure is the

highest pressure attained in the arteries during ventricular contraction. Diastolic

blood pressure is the lowest pressure attained in the arteries during ventricular

relaxation. Pressure is highest in the aorta and drops as blood moves away from the left ventricle into systemic circulation.

Vascular resistance is the opposition to blood flow that occurs from friction

between blood and blood vessel walls. The 3 factors that influence vascular

resistance are:

• size of the blood vessel lumen: the smaller the lumen, the greater the resistance

• blood viscosity or thickness: the higher the viscosity, the greater the resistance

• total blood vessel length: the longer the blood vessel, the greater the resistance

endothelium which comes in direct contact with blood