1 Blood (rev 11/11) The circulatory system consists of the heart, blood vessels and the blood...

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Blood (rev 11/11)

• The circulatory system consists of the heart, blood vessels and the blood itself.

• The circulatory system is essential to supply all cells with what they need and removing substances they no longer need.

BIO 102-Blood-Cardiovascular

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The Functions of Blood

Blood is actually a liquid body tissue and is classified as a connective tissue

Blood carries out three essential tasks:

• Transportation: oxygen, nutrients, waste, hormones

• Regulation: body temperature, volume of water in the body, pH of body fluids

• Defense: contains specialized defense cells to protect against illness and excessive bleeding through clotting mechanisms

These are necessary for homeostasis.


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Blood Components

All blood cells and platelets develop from stem cells in the red bone marrow.

Blood is made up of the following: • Formed elements (cellular components--45%):

– RBCs or erythrocytes; most abundant cell type; primarily is a carrier of oxygen and carbon dioxide

– WBCs– Platelets

• Plasma (liquid components--55%):– Water– Electrolytes (ions of elements)– Proteins (albumins, globulins, clotting proteins)– Hormones– Gases (oxygen and carbon dioxide)– Nutrients and wastes


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RBC (erythrocytes) Production=Erythropoiesis

• Stem cells develop into immature cells called erythroblasts.– Erythroblasts become erythrocytes in about 1 week– They lose their nucleus and organelles as they

mature so they can’t reproduce– New RBC must develop (from stem cells) because

with no nucleus, RBC can’t accomplish any cellular activities and wear out quickly

– Old or damaged RBC are removed from blood and destroyed in the liver and spleen by macrophages in a process called phagocytosis.

• Many cell components are recycled: hemoglobin is broken up into its amino acids, iron atoms returned to bone marrow, heme group is converted to bilirubin


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Red Blood Cells– contain hemoglobin, a protein which

carries oxygen and carbon dioxide– RBC live for approximately 4 months. – As they mature, they expel their nucleus so

they can carry more hemoglobin.– They also assume a biconcave shape.

This shape makes them more flexible and allows more of them to fit into blood vessels to increase the surface area available for gas (O2 and CO2) exchange.


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Hemoglobin Molecule• Hemoglobin is an oxygen binding protein

which consists of 4 polypeptide chains coiled around a “heme group”

• The “heme group” has an iron atom in its center. This combines easily with oxygen at the lungs AND lets go of the oxygen when reaching body tissues.


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Hematocrit• is a measure of the oxygen carrying capacity

of blood • is obtained by spinning down blood and

measuring the amount of formed elements • RBCs make up nearly 99% of formed

elements• Normal hematocrit

– men: 43-49% women: 37-43%


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• Regulation of RBC production is a negative feedback control loop which maintains homeostasis.

• Cells in the kidneys check the availability of oxygen. If levels are low, these cells are signaled to secrete the hormone erythropoietin. This is carried to red bone marrow where more RBC are produced.

• When the oxygen levels are appropriate, the kidney cells stop production of erythropoietin.


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White Blood Cells-WBC or leukocytes

Functions: protection from infection, regulation of the inflammatory reaction

• Types:– Granular:

• neutrophils, eosinophils, basophils• Mature in the red bone marrow• Granules are actually vesicles filled with proteins

and enzymes– Agranular:

• lymphocytes, monocytes• monocytes mature in red bond marrow;

lymphocytes mature in the thymus gland


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Circulating levels of WBC rise whenever the body is threatened by viruses, bacteria, or other health challenges

• Each type of WBC can produce chemicals which travel, via the blood, to the bone marrow where they stimulate the production of more WBC

Most WBC remain in the blood vessels, but some circulate in the intercellular fluid and the lymphatic system.


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Types of WBC • Neutrophils-most common WBC- approximately

60% of WBC are neutrophils

• see in acute infections; are the first WBC to combat infection

• main function is phagocytosis (bacteria and fungi)

– Eosinophils- approximately 2-4% of WBCs

• see in parasitic infections (such as worms) and in allergic reactions (they release chemicals that diminish the severity of these reactions)


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– Basophils-are rare, 0.5% of WBCs• initiate the inflammatory response—

granules in the cell cytoplasm contain histamine which starts the inflammatory response

– Lymphocytes-second most common WBC, about 30%; found in tonsils, blood, spleen, lymph nodes, thymus

• manufactures antibodies and eliminates anything foreign to the body

• play crucial role in immune response– Monocytes-about 5%

• active in phagocytosis• elevated in chronic infections


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Platelets• are small cell fragments (not complete cells) which

play an essential role in the process of blood clotting• platelet production is regulated by hormone

thrombopoietin• platelets are stable as they circulate, but when they

encounter a “rough surface” they form a temporary plug and initiate the clotting mechanism

• the body also requires vitamin K for normal blood clotting


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• Clotting process or hemostasis (stopping blood)

– damage to a blood vessel triggers a vasospasm or constriction of the damaged blood vessel

– platelets in the area swell, become sticky, adhere to the damaged area and produce a plug which will become the clot

– platelets also release chemicals to help in clot formation

• prothrombin activator converts prothrombin (a plasma protein) into thrombin

• thrombin converts the fibrinogen molecules, to fibrin which traps blood cells, forms a clot and seals the hole


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• Blood Typing– Each of us has one of 4 types of blood--A, B, AB, O--

along with some specific glycoproteins or antigens• Our cells have surface proteins that the immune

system can recognize as “self” or “non-self”. The immune system will recognize foreign cells as non-self .

• An antigen is a non-self cell protein that causes the immune system to defend itself.

• The immune system builds antibodies-an opposing protein which can kill the non-self cells.

– and causes them to stick together so it can be destroyed. So, the transfused blood clumps or clots within our blood vessels.

– This can be fatal


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• Another antigen found in blood is the Rh antigen--if you have it, your blood is classified as Rh positive. If you do not have this, your blood is classified as Rh negative.

Blood Typing Tests– Based on the interaction between antigens

and antibodies– performed with anti-sera which contain

high concentrations of anti-A and anti-B antibodies

– blood samples are mixed with each anti-sera


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– if agglutination or clumping (similar to clotting) occurs with

anti-A sera, you have type A blood

anti-B sera, you have type B blood– if clumping occurs with both anti-A and

anti-B, you have type AB blood– if no clumping occurs with either anti-A and

anti-B sera, you have type O blood• so, the antibodies you have in your body are

the opposite of your blood type


BIO 102-Blood-Cardiovascular 18

Blood Types Determine Blood Compatibility

Figure 7.12

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Blood Typing

Blood Type

Reaction

Anti-A Serum Anti-B Serum

Antibody Type

Type A Agglutination No

Agglutination

Anti-B antibody

Type B No

Agglutination

Agglutination Anti-A antibody

Type AB Agglutination Agglutination No antibodies against major blood groups

Type O No

Agglutination

No

Agglutination

Anti-A & Anti-B antibodies


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Blood Disorders

• Carbon monoxide poisoning: competes with oxygen

Anemia: reduction in oxygen-carrying capacityTypes of Anemia• Iron deficiency anemia occurs when there is insufficient

iron ingested so fewer hemoglobin molecules are available.

• Aplastic anemia where the bone marrow doesn’t produce enough stem cells

• Hemorrhagic anemia is caused by extreme blood loss


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• Pernicious Anemia where the body is unable to absorb vitamin B12 from the digestive tract. The body uses B12 to produce normal RBC.

• Sickle cell Anemia is an inherited disorder in which the RBC become sickle or crescent shaped when the oxygen concentration of the blood is low. This shape doesn’t travel easily through blood vessels because the cells clump, get stuck in the vessels and cause a great deal of pain. – Sickle shaped cells can’t carry a normal

amount of oxygen.


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• Leukemia is a form of cancer where you see an uncontrolled production of abnormal or immature WBC in the bone marrow. This crowds out the production of normal WBC, RBC, and platelets.

• Multiple myeloma: a form of cancer where abnormal plasma cells in the bone marrow increase production. These cells are important for the manufacture of antibodies.

• Mononucleosis is a contagious infection of lymphocytes caused by the Epstein-Barr virus.

• Septicemia can also be called “blood poisoning”. It occurs when organisms invade the blood, overpower our body’s defenses and multiply rapidly in the blood.

• Thrombocytopenia is a reduction in the number of platelets.


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Polycythemia is a term used to describe an abnormally high RBC count– this increases the thickness of blood and

slows down the flow of blood.

Hemophilia is an inherited condition caused by a deficiency of one or more clotting factors (known as clotting factor VIII)– When a blood vessel is damaged, blood either clots

very slowly or not at all


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The Cardiovascular System

Blood Vessels: Arteries, VeinsArterial systemStructure: • Endothelium: thin inner layer of squamous epithelial cells• Middle: thick layer of smooth muscle woven with elastic

connective tissue• Outer layer: tough supportive layer of connective tissue,

primarily collagen– anchors vessels to surrounding tissues and helps protect them

from injury• Aneurysm: ballooning of the arterial wall

– Endothelium of blood vessel becomes damaged and blood seeps through and accumulates between the middle and outer layers of the blood vessel


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• Functions:– Arteries: carry blood away from heart– Need thicker muscular wall due to pressure of blood

being pumped by aorta – Because blood pressure is less by the time blood has

reached the arterioles, they do not have the outermost layer of connective tissue and the muscular layer is thinner.

• precapillary sphincter, a band of smooth muscle, is located where the arteriole meets the capillary and controls the blood flow to each capillary

• Capillaries: thin walled blood vessels; branching design allows exchange of gases, nutrients, waste, and defensive cells between vessel and tissue


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– vasoconstriction– vasodilation


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Venous system• Functions: carry blood to the heart • Structure: veins: three layers, thin-walled

– like the walls of arteries, the walls of veins consist of 3 layers of tissue.

• Outer 2 layers are much thinner than those of arteries

• veins have larger diameters (lumen) than arteries – the pressure in veins is much lower than that in

arteries which is why their walls are not as strong as arteries

• Blood pressure lower in veins than in capillaries– veins can act as a blood volume reservoir


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– the larger diameter of veins allows them to stretch to accommodate large volumes of blood at low pressures

– because veins can stretch, it is more difficult for them to return blood to the heart against the force of gravity

– people who spend a lot of time on their feet may get varicose veins because of this

• Factors which help veins to return blood to heart

• Contraction of skeletal muscles-skeletal muscle pump

• as we move and muscles contract and relax, they press against veins and help push blood to the heart


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– One-way valves—blood can only flow in one direction

• Open passively to allow blood to move toward the heart and cloose whenever blood begins to flow backward

– the work of the skeletal muscles helps the valves pump blood. This is called a skeletal muscle pump


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Pressure changes associated with breathing– movements associated with breathing also help

pump blood. This is called a respiratory pump and helps to push blood from the abdomen to the chest and to the heart.

• when we breathe, there are pressure changes in the thoracic and abdominal cavities

• during inhalation, abdominal pressure increases and squeezes abdominal veins

• simultaneously, pressure within the thoracic cavity decreases which dilates the thoracic veins and thus propels the blood.


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Lymphatic System

Function: maintains proper volume of blood and interstitial fluid; also functions in immune system– Picks up objects in interstitial fluid that are too large to

diffuse into capillaries• Lipid droplets absorbed during digestion• Invading organisms

– Transports these to larger lymphatic vessels which return the fluid to veins near the heart

• Structure:– Lymphatic vessels– Lymph


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The Heart

Structure: composed of cardiac muscle enclosed by pericardium, a fibrous sac– Pericardium protects the heart, anchors it to

surrounding structures, prevents it from overfilling with blood

– Pericardial cavity separates it from heart muscle itself and contains a tiny amount of fluid to allow heart and pericardium to glide smoothly every time the heart contracts

– Heart beat rate determined by the SA Node


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The Heart• Layers: Epicardium: thin, outermost layer

made up of epithelial and connective tissue– Myocardium: thick layer primarily of cardiac

muscle – Endocardium: innermost layer of endothelial

tissue resting on a layer of connective tissue; is continuous with the endothelium that lines blood vessels


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The Heart• Pericarditis:

– A layer of the heart wall becomes inflamed• Endocarditis: inflammation of the endocardium• 4 Chambers: two atrias, two ventricles

– Atrias are on the top– Ventricles are the 2, more muscular chambers

on the bottom• Septum, a muscular partition, separates the right

and left sides of the heart


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The Heart• Valves: prevent blood from flowing backward

– Two atrioventricular valves: tricuspid (right) and bicuspid (mitral--left)• Chordae tendinae: strands of connective

tissue which connect to muscular extensions of the ventricle wall, called papillary tendons

• These prevent the valves from being pushed backward

– Two semilunar valves: pulmonary and aortic• Have 3 flaps


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Flow of blood through the heart:

• Deoxygenated blood through the vena cava to the right atrium

• Deoxygenated blood through the right atrioventricular valve to the right ventricle

• Deoxygenated blood through the pulmonary semilunar valve to the pulmonary trunk and the lungs

• Oxygenated blood through the pulmonary veins to the left atrium

• Oxygenated blood through the left atrioventricular valve to the left ventricle


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• Oxygenated blood through the aortic semilunar valve to the aorta

Blood flow through the tissues:• Oxygenated blood through branching

arteries and arterioles to the tissues• Oxygenated blood through the arterioles to

capillaries• Deoxygenated blood from capillaries into

venules and veins• Ultimately to the vena cava and into the

right atrium


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• Coronary arteries supply the heart muscle with blood (myocardium is too thick to be able to be supplied with oxygen and nutrients by diffusion from the blood passing through it)

• Coronary arteries branch from the aorta as it leaves the heart and encircle the heart’s surface

• Cardiac veins bring the blood back to the right atrium


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Cardiac cycle is a measure of the blood pumped with each beat multiplied by the number of heart beats per minute

• Steps summarized:1. Heart relaxes and all four chambers fill; blood is

sucked in as the heart muscle expands

2. Atrial contraction: more blood into the already filled ventricles

3. Ventricular contraction: blood is ejected into the aorta and pulmonary trunk

• Systole refers to the contraction pressure• Relaxation of the entire heart = diastole


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Heart Sounds and Heart Valves

• Lub-dub – Lub signals the closure of the 2 AV valves– Dub signals the aortic and pulmonary

semilunar valves closing

• Heart murmurs are created by obstructions the blood encounters as it flows through the heart


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Cardiac conduction system is a group of specialized cardiac muscle cells that initiate and distribute electrical impulses throughout the heart– is responsible for the coordinated sequence of

the cardiac cycle which spreads from atria to ventricles

– Consists of: sinoatrial node, atrioventricular bundle and its 2 branches and Purkinje fibers


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• Sinoatrial (SA) node– Provides the stimulus that starts the heartbeat

• Is a small mass of cardiac muscle cells close to where the right atrium and the superior vena cava meet

• Emits an electrical impulse that travels across both atria stimulating waves of contraction

• Is called the cardiac pacemaker because it initiates the heartbeat

• Atrioventricular (AV) node– Located between the atria and ventricles– Muscle fibers are smaller in diameter which causes a

slight delay of the electrical impulse. This allows the atria time to contract and empty their blood into the ventricles before the ventricles contract


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– Atrioventricular bundle:• Located in the septum between the 2 ventricles • These fibers branch and extend into Purkinje

fibers, smaller fibers that carry the impulse to all cells in the ventricular myocardium

• The impulse travels down the septum (to the lower part of the ventricles) and then spreads rapidly upward through the purkinje fibers, the lower part of the ventricles contract first and squeeze blood into the pulmonary trunk and the aorta.


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Cardiac Conduction System Coordinates Contraction

• SA node: cardiac pacemaker

• AV node: relay impulse

• AV bundle and Purkinje fibers: carry impulse to ventricles

Figure 8.14BIO 102-Blood-Cardiovascular

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Electrocardiograms (EKG/ECG)

We can track the electrical activity of the heart as weak electrical differences in voltage with an EKG– Place “leads” or electrodes at the chest, wrists

and ankles• Three formations:

– P wave: impulse across atria– QRS complex: spread of impulse down

septum, around ventricles in Purkinje fibers (this occurs just as the ventricles start to contract)

– T wave: end of electrical activity in ventricles


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• Arrhythmias are an abnormal rhythm or rate of heartbeat– Some arrhythmias are common and not

potentially dangerous– ventricular fibrillation is the leading cause of

cardiac death• Can treat with medication or “cardioversion” with

an electric shock or artificial pacemakers


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Electrocardiograms (EKG/ECG)

Figure 8.15b,cBIO 102-Blood-Cardiovascular

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Blood Pressure

• Force that blood exerts on the wall of a blood vessel as a result of the pumping action of the heart

• Definitions: “normal”:– Systolic pressure: highest pressure, pressure reached

during ventricular contraction to eject blood from theheart

– Diastolic pressure: lowest pressure, pressure when the ventricles relax

• Arteries store energy generated during systole and during diastole they use that stored energy to supply blood to the tissues

• Measurement: sphygmomanometer


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• Hypertension: high blood pressure:– Definition– The silent killer– Risk factors

• Hypotension: blood pressure too low so blood can’t be pushed throughout the body and back to the heart; generally thought of as reducing blood flow to the brain– Clinical signs: dizziness, fainting– Causes: orthostatic, severe burns, blood loss


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Regulation of the Cardiovascular System: Baroreceptors

Baroreceptors: pressure receptors in aorta and carotid arteries which help maintain arterial blood pressure

• Steps in mechanism:– Blood pressure rises, arterial vessels stretched– Signals sent to cardiovascular center in the brain – Heart signaled to lower heart rate and force of

contraction– Cardiac output (amount of blood and rate that the

heart pumps into the aorta) lowered– Arterioles vasodilate (increasing arteriole diameter)

and thus increasing blood flow to tissues– Combined effect lowers blood pressure

The opposite happens when blood pressure is too low


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Regulation of the Cardiovascular System: Nervous and Endocrine Factors

• Medulla oblongata regulates cardiac output (obtained by multiplying heart rate by stroke volume (volume of blood pumped out with each heartbeat)– Sends nerve signals to the heart via:

• Sympathetic nerves: increase heart rate; constrict blood vessels, raising blood pressure

• Parasympathetic system, a decrease in nerve activity will dilate blood vessels, lowering blood pressure; decrease heart rate; dilate blood vessels

• Hormones: epinephrine (adrenaline) and norepinephrine• Local requirements dictate local blood flow based upon a

need for more or less oxygen and nutrients and waste products to be removed


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Cardiovascular Disorders

• Angina pectoris: a chest pain warning• Myocardial infarction/heart attack: permanent

cardiac damage• Congestive heart failure: decrease in pumping

efficiency• Embolism: blockage of blood vessels• Stroke or Cerebrovascular Accident or brain

attack: impaired blood flow with subsequent damage to the brain


• Pericarditis:– Inflammation of the pericardium (sac which

surrounds the heart)• Endocarditis: inflammation of the endocardium

BIO 102-Blood-Cardiovascular 53

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Reducing the Risk of Cardiovascular Disease

• Smoking: don’t • Blood lipids: monitor cholesterol levels• Exercise: regular and moderate• Blood pressure: treat hypertension• Weight: being overweight increases risk of heart

attack and stroke• Control of diabetes mellitus: early diagnosis and

treatment delays onset of related problems• Stress: avoid chronic stress


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Cardiac Anatomy Quiz


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