ANATOMY
Circulatory system- cardiovascular system & lymphatic system
Cardiovascular system- heart, blood vessels, blood
Lymphatic system- lymphatic vessels, spleen, thymus, tonsils, lymph nodes
Lymphatic system
Consists of lymphatic vessels, lymphoid tissue & organs
Liquid in lymphatic capillaries is called lymph
Used to maintain fluid balance in tissues, to absorb fat from gastrointestinal tract
Also part of body’s immune system
Vessels drain intercellular fluid into bloodstream in the subclavian veins
In small intestine, lymphatic capillaries called lacteals absorb fat away from GI tract
Lymph is carried by lymphatic capillaries to lymph ducts that all interconnect & empty into
the thoracic duct or the right lymphatic duct
Lymph is filtered as it moves through lymph nodes where phagocytic cells purify the fluid
Nodes are clustered in specific regions of body
Other lymph nodes include the tonsils, spleen & thymus
Tonsils- form a protective rings of lymphatic tissue around opening between nasal/oral
cavities & pharynx
Spleen- not vital in adults but helps other organs make lymphocytes, filter blood &
destroy old RBC
Thymus- key role in immune system
Cardiovascular system
Blood Connective tissue with liquid matrix, 3 types of cells suspended in liquid plasma
Cells 45% & plasma 55%
Average adult has 5L which is 8% of body mass
Thicker/more viscous than water
pH 7.35-7.45
Cells made in red bone marrow
Bright red color indicates presence of oxygen & dull red indicates lack of oxygen
Erythrocytes (red blood cells)
5.1-5.8 million/cubic millimeter of blood in males
4.305.2 million in females
Most numerous blood cell
Biconcave disc shape mature ones lack nuclei & mitochondria
Survive 120 days & are then destroyed by phagocytic cells in liver/spleen
Oxygen attached to hemoglobin molecules- each hemoglobin can carry 4 molecules
Each RBC contains about 280 million hemoglobin molecules
Actually 2 kinds of hemoglobin- A & B
A makes up 98% of adult’s hemoglobin & B only 2%
Made in bone marrow of arm/leg bones, vertebrae, ribs, sternum, skull
Leukocytes (white blood cells)
5-10,000/cubic millimeter of blood
Least numerous blood cell
Larger than RBC & have nuclei/mitochondria
Some can move out of capillaries & into tissues to destroy disease causing organisms
10 day life span
Made in bone marrow, spleen, thymus & lymph glands
Two main types
Granulocytes- cytoplasm shows presence of large number of small granules
Neutrophils- account for 60-75% of WBC; protect body against infection
by eating/digesting foreign matter; usually die within a few
hours so live 12-24 hours
Eosinophils- 2-4% of WBC; do same as neutrophils but also help break
up blood clots by releasing enzymes
Basophils- 1% of WBC; release heparin (body’s natural anticoagulant)
& secrete histamines (during allergic reactions)
Agranulocytes- cytoplasm doesn’t have granules
Monocytes- 3-8% of WBC; largest WBC; scavenges for foreign matter;
can migrate into surrounding body tissues where they can
increase in size & become macrophages that continue to
scavenge for foreign matter
Lymphocytes- 20-25% of WBC; smaller size with large nucleus & little
cytoplasm; become B cells & T cells of immune system
Thrombocytes (platelets)
Fragments of larger cells in red bone marrow Lack nuclei
250,000-450,000/cubic millimeter of blood
Can move out of capillaries
Capable of amoeboid movement
Live 5-9 days & then are destroyed by spleen/liver
Important role in blood clotting & blood clot formation
Rich in secretory granules that trigger clot formation/coagulation
Stick to damaged areas & seal breaks
Plasma Straw colored liquid where blood cells are suspended
90% water, rest is proteins, inorganic salts (sodium, potassium, calcium chloride,
phosphates), carbohydrates (sugars), lipids, amino acids, chemical waste (urea,
uric acid), vitamins, hormones
Transports nutrients, gases, vitamins
Regulates electrolyte/fluid balance & maintains blood pH
Plasma proteins- 7-9% of plasma
Albumins- smallest but most numerous proteins, made by liver, make blood
thick, help regulate blood pressure (osmotic pressure) & transport
lipids/bile
Globulins- made in liver or lymphoid tissue; transport lipids, hormones, iron &
vitamins as well as helping with immunity
Fibrinogens- large proteins made in liver; help in blood clotting by forming a
matrix where cells get trapped
Heart
Transport pump that keeps blood continuously circulating through body
Roughly the size of fist 255 g in adult females & 310 g in adult males
Contracts 42 million times/yr pumping 700,000 gallons of blood
Located in thoracic cavity between lungs
Parietal pericardium (pericardial sac)
Loose fitting double walled sac of dense fibrous connective tissue that encloses/protects
heart
Forms wall of pericardial cavity that is filled with pericardial fluid
Wall of heart
Epicardium- outer layer; also called visceral pericardium
Myocardium- thick middle layer made of cardiac muscle tissue; layer that actually
contracts
Endocardium- inner layer of wall; continuous with endothelium of blood vessels
Interior of heart- 4 chambers; right/left halves separated by septum
Atria- two upper chambers separated by thin muscular interatrial septum; each has
ear shaped expandable appendage called an auricle
Ventricle- two lower chambers separated from each other by thick muscular
interventricular septum; walls are thicker than atria since must push blood
farther (left is thicker than right)
Valves- 4 total
Atrioventricular valves- AV valves between atria/ventricles; bicuspid or mitral
valve on left side, tricuspid on right side
Semilunar valves- between ventricle & arteries leaving heart; pulmonary valve
& aortic valve
Blood circulation routes
Blood in heart
Superior vena cava & inferior vena cava drain deoxygenated blood from body into
right atria; blood passes through tricuspid valve to fill right ventricle; when the
ventricle contracts it pushes the blood through the pulmonary valve to the
pulmonary arteries; the blood leaves the heart here to go to the lungs to drop
off carbon dioxide & pick up oxygen; the pulmonary veins deposit oxygenated
blood into the left atrium; blood passes through the bicuspid valve to fill the
left ventricle; when the left ventricle contracts with a mighty force the blood
exits the heart through the aortic valve & the aorta
Pulmonary circulation
Vessels transport blood to the lungs & then back to the heart after blood has refreshed
its oxygen level; pulmonary arteries are only arteries that transport
deoxygenated blood; pulmonary veins are only veins to carry oxygen rich blood;
right ventricle of heart pumps blood to lungs for purpose of enriching the
blood’s oxygen content & diminish the carbon dioxide content
System circulation
Vessels transport blood from left ventricle of heart, through body & back to the right
atrium; delivers oxygen & picks up carbon dioxide from body; left ventricle of
heart pumps blood to all the body’s organs to nourish & remove wastes; aorta,
arteries, arterioles, capillaries, venules, veins, vena cava
Coronary circulation
Vessels that supply the heart walls with the oxygen it needs; made of coronary arteries
that exit the aorta & the coronary veins deliver blood back to the right atrium
through the coronary sinus
Contraction of heart is controlled by specialized strands of interconnecting cardiac muscle tissue
(sinoatrial node, atrioventricular node, atrioventricular bundle & conduction myofibrils)
SA node is called the pacemaker & is found in the posterior wall of the right atrium
SA node initiates the contraction, AV node in inferior portion of interatrial septum sends signal
on to AV bundle between ventricles
Contraction of ventricles is systole & their relaxation is diastole
These cause pressure in arteries & is measured as blood pressure
Sounds of heart come from 2 actions
“lub” is made when AV valves close
“dub” is from closing of other valves
Both right/left sides of heart act together- both atria fill at the same time, both ventricles fill at the same
time, both ventricles expel blood at the same time
Blood vessels
Form closed network of tubes that allow blood to flow through body
If lined up end to end an adult human’s blood vessels would circle the Earth’s equator 4 times
Walls of arteries/veins are made of 3 layers
Tunica externa (adventia)- outermost layer made of loose connective tissue
Tunica media- middle layer of smooth muscle & elastic fibers
Tunica interna (intima)- innermost layer made of simple squamous epithelium & elastin;
also called endothelium
Differences between arteries & veins
Arteries have more muscle than veins thus thicker walls; arteries are both strong/elastic
Arteries appear more round than veins
Arteries carry blood away from heart; veins carry blood toward heart
Veins are usually partially collapsed because they don’t fill all the way
Veins can stretch more & have valves inside them
Veins aren’t found in the wall of the heart
Arteries
Expand with pressure of blood when heart contracts & recoil when pressure decreases
Small muscular arteries are 100 micrometers or less in diameter
Capillaries
7-10 micrometers in diameter
Functional unit of circulatory system since this is where exchange of gases, nutrients
& wastes occurs
Over 40 billion capillaries in body
Walls are only 1 cell layer thick
Blood flows slowest here but there is little frictional resistance to the movement of
blood
Types of capillaries
Continuous- those in which adjacent endothelial cells are tightly joined together
Found in muscles, lungs, adipose tissue & CNS
Fenestrated- have wide intercellular pores that are covered by layers of
mucoprotein
Occur in kidneys, endocrine glands & intestines
Discontinuous- large spaces between endothelial cells
Found in bone marrow, liver & spleen
Veins Carry oxygen poor blood from capillaries back to heart
Very little pressure which isn’t enough to return blood to heart
Massaging action of muscles as well as presence of venous valves moves blood through
Valves in medium-large veins
Valves help to move blood by preventing blood from flowing backwards
Blood pressure
Force exerted by blood against the inner walls of the vessels through which it flows
Considered a vital sign
Measured with sphygmomanometer over the brachial artery
Normal is 120/80
Difference between the two numbers is the pulse pressure
Diminishes the further the blood moves from the heart
PHYSIOLOGY
Major jobs of circulatory system
Transport oxygen, nutrients & raw materials to body’s tissues
Remove carbon dioxide & metabolic waste from body’s tissues
Transport hormones & other secretory substances from one tissue/organ to another
Distribute body’s heat of metabolism
Regulation of body homeostasis
Protection against disease
Cardiac cycle
Sequential actions of heart’s chambers
About 0.8 sec long if heart is beating 75 times/min
Begun by SA node
Systole- contraction of heart chamber that empties it
Atrial systole 0.1-0.2 sec
Ventricular systole 0.3 sec
Diastole- relaxation of a heart chamber to it can fill
About 0.5 sec long
Right/left atrial systole occur at same time & are accompanied by right/left ventricular diastole
Ventricular systole accompanied by atrial diastole
When chambers contract, they do not eject all of the blood in them (only about 50-60%)
The more blood entering the ventricle, the greater the force with which the ventricle contracts to
eject it (Frank-Starling Law of the Heart)
Stroke volume- volume of blood expelled from left ventricle with each systole
About 70 mL of blood when resting & more during exercise
Cardiac output or minute voume
5250 mL of blood (70 mL x 75 beats/min) at rest & more when exercising
Amount of blood leaving heart
If average adult male has 5 L of blood & a resting cardiac output of 5250 mL then it takes an average
of 1 min for a drop of blood to circulate through the body
If you have a major leak & had been working out, it could take about 7 sec to pump your
body dry or about 63 sec at resting heart rate
Blood pressure
Pressure against the walls of the vessels through which blood is flowing
Decrease between aortic pressure & vena cava pressure is due to friction within the blood
& between the blood/vessel walls
called peripheral resistance
Must use artery to measure blood pressure because venous pressure is very low (almost
0 mm Hg in vena cava)
Systolic blood pressure- occurs at peak of ventricular contraction
120 mm Hg
Diastolic blood pressure- occurs as left ventricle relaxes/fills with blood 80 mm Hg
Pulse pressure- difference between systolic/diastolic pressures
Measuring with sphygmomanometer
Pump air into cuff until pressure level reaches 180 mm which stops flow of blood in arm
No sounds will be heard
Slowly release air from cuff & listen. When faint Korotkoff sounds are heard note the
pressure (systolic)
As cuff pressure continues to drop the sound will fade. Note the pressure when sounds
can no longer be heard (diastolic)
Factors affecting blood pressure
Nervous control via reflex arcs
Kidneys- renal regulation changes thickness of blood
Chemicals
Elasticity of vessels- allows them to expand/contract as blood pressure changes
Pumping action of heart- heart pumps 5.6 L of blood/min
Size of blood vessels- smaller the vessel, the higher the pressure forcing the blood
through
Amount of blood present- loss of blood lowers pressure
Thickness of blood- thicker blood has more pressure
How fast does blood move? 10 inches/sec through the aorta but in capillaries it can drop to
1/100th inch/sec & then it speeds up some in the veins
Valves in veins & the massaging of veins by skeletal muscles that keep blood flowing back to heart
Cardiac muscle
Myogenic- doesn’t rely on nervous system for stimulation
Self-stimulating- first cell is stimulated & it excites neighboring cells
Pace is set by SA (sinoatrial) node in wall of right atrium near superior vena cava
If left to itself, SA node would make heart beat 100 times/min but it is controlled by the
sympathetic/parasympathetic nervous system
Beating of the heart
SA node initiates an impulse about once a second; this depolarization wave spreads across the
atria at 800-1000 cm/sec
This wave is immediately followed by a wave of muscle contraction that pushes blood out of
atria
AV (atrioventricular) node is at base of right atria near heart’s center septum
SA node depolarization triggers depolarization through heart septum to Bundle of His
(30-50 cm/sec speed); Relays conduction of stimulus from atria to ventricles
As we age, AV node may slow down & it may be necessary to get an artificial pacemaker
Bundle of His divides into left/right bundle branches that travel down septum
At heart apex the branches become Purkinjie fibers that radiate upward along inside walls of
ventricles; this depolarization occurs very quickly (5000 cm/sec); this contraction
pushes blood up/out of ventricles
How is your heart controlled?
Sympathetic NS- increases heart rate; center for this lies in medulla oblongata in the
cardioaccelerator center
Parasympathetic NS- decreases heart rate; center in medulla oblongata in the cardioinhibitor
center
These activities are determined by the nature of impulses reaching centers from cerebrum
(ex. Watching scary movie makes heart beat faster), impulses reaching centers from
aorta/carotid arteries (ex. Increase in pressure decreases heart rate), & chemical
composition of blood flowing through medulla oblongata (ex. Oxygen decreases or
carbon dioxide increases will cause heart rate to increase), age, gender, body
temperature, postural changes, emotions, activity level
Other control factors
Nervous impulses to vessels
Vasoconstriction- brain keeps arteries in slight contraction
Vasodilation- brain relaxes muscle fibers in vessels
Drugs
Epinephrine- heart rate & blood pressure increase for a short time
Acetylcholine- acts as a relaxing agent to dilate vessels
Histamine- dilates arterioles/capillaries if in excess
Alcohol- vasodilator/depressant
Nicotine- vasoconstrictor/stimulant
Ephedrine- constricts vessels locally
Hematocrit
Ratio of blood cells to total volume of whole blood
Adult males 46%
Adult females 42%
If it drops below 30% person is anemic since there are too few RBC
Buffy layer in middle is WBC/platelets
How does exchange take place between tissues/blood?
Capillary walls are one cell thick so small molecules are freely permeable & larger molecules
must be moved other ways (diffusion/filtration)
Diffusion occurs because there is a concentration gradient
Movement goes from area of high concentration to area of lower concentration
Filtration occurs due to pressure differences between blood/osmotic pressure
Movement goes from area of high pressure to area of lower pressure
Hemostasis
Body’s effort to minimize amount of blood lost by body through wound
Methods of hemostasis
Vasoconstriction (vascular spasm)- happens immediately upon injury to blood vessels
Smooth muscle tissue of vessel constricts to reduce blood flow
Platelet plug formation- when injury to vessel wall occurs collagen fibers in connective
tissue become directly exposed to blood; platelets catch on these fibers & to
surfaces coated with von Willebrand factor; platelets release secretory
granules that contain ADP/vasoconstrictors; as more platelets gather a platelet
plug is formed to seal the wound temporarily
Coagulation- most important mechanism
Blood changes from fluid to solid to form long-lasting seal for wound (scab)
Fibrin threads support the platelet plug & trap RBC/WBC to increase size of plug
Fibrin threads formed from fibrinogen plasma proteins through a series of
chemical reactions
Step 1- thrombin protein alters the fibrinogen molecule to form fibrin
monomer
Step 2- monomers link together to form polymer
Step 3- polymerized monomers cross link to form a stable fibrin clot
Normally fibrinogen has a concentration of 200 mg/mL blood
Blood types
Blood carries proteins called antigens which stimulate the production of antibodies
Blood classification (A-B-O) is based on antigens found on RBC surfaces
RBC can carry A antigen, B antigen, both or neither to produce blood types A, B, AB, & O
Genes IA, IB or i
Type A makes anti-B antibodies, Type B makes anti-A antibodies, Type O makes both anti-A &
anti-B antibodies but Type AB makes neither
When A blood is added to B blood, B antibodies attack foreign A antigens causing blood to
clump together so transfusion recipients must receive blood that is compatible to theirs
If transfusions do not match, then antigens make antibodies to attach foreign blood & blood
clumps
O is universal donor & AB is universal recipient
Rh factor is another blood antigen
If Rh+ blood is added to Rh- blood, antibodies will react with antigen & clumping will
occur
Rh incompatibilities during pregnancy (- mother + father)
If first child is +, mother will react to second child & fetus may die if medication
(Rhogam) is not given at first birth
There are other types of blood antigens that aren’t as commonly known but still important in
transfusions/transplants
Some Disorders of Circulatory System
Anemia
Lack of hemoglobin (therefore fewer RBC) in blood which corresponds with a lower oxygen
supply
Most common type is iron-deficiencty anemia
Aplastic anemia due to destruction of bone marrow such as in radiation therapy
Pernicious anemia due to lack of vitamin B-12
Symptoms: fatigue, weakness, pale color
Treatment: iron supplements
Sickle cell anemia
Genetic defect more common in African-Americans
Sickling of RBC produced by lack of oxygen such as when traveling at high altitudes or
exercising vigorously
Hypertension (high blood pressure)
~20% of adults have this
140/90 is considered high
Blood is forced through capillaries too fast for sufficient exchange of nutrients/waste
Risk factors: heredity, male gender, obesity, high salt diets, alcohol use, smoking, inactivity,
over age 35, stress
Complications: damage to kidneys, weakened blood vessels, blindness, heart disease
Treatments: lifestyle changes, medication (sympathetic nerve blockers, calcium channel
blockers, ACE inhibitors), vitamin C may help
Arteriosclerosis (hardening of arteries)
Lining of arteries become thickened/roughened due to deposits of cholesterol, proteins
& calcium
Makes it easier for clots to become lodged since vessels are smaller
Cholesterol- 2 types (low density & high density lipoproteins)
LDL creates harmful deposits
HDL may help block accumulation of LDL on walls; takes cholesterol from blood &
returns it back to liver to be flushed from body
Total blood cholesterol increases with age but HDL part remains fairly constant
Exercise may increase LDL
Varicose veins
Cause chronically swollen legs & skin ulcers
Swollen twisted veins at surface of skin look like bumpy blue ropes
Valves have failed & blood is pooling in veins
May be hereditary
Symptoms: aching tired legs, itchiness, leg cramps/tenderness, stabbing pain
Self helps: wear loose fitting clothing, elevate legs, don’t sit/stand too long, exercise regularly,
lose excess weight, eat high fiber diet, avoid high heels/support hose
Heart attack (myocardial infarction)
Death to section of heart muscle due to blockage of blood supply possibly caused by blood clot
(thrombosis) in coronary artery or fatty deposits
75% occur after age 65
Risks: smoking, excess weight, high blood pressure, lack of exercise, family history, age, gender
(males)
Symptoms: heavy chest pain, tightness, pain in jaw/shoulder/arm/neck, pain like severe
heartburn, sweating, nausea, women tend to also feel short of breath
Treatment: bypass surgery where healthy veins are transplanted to heart to increase blood flow
Women are twice as likely to die within a few weeks
Aspirin may reduce risk of having first heart attack in men by keeping blood thinner & from
forming clots
Stroke (brain attack)
3rd leading cause of death
Blockage of blood supply to brain due to clot or bulge in blood vessel that bursts
Some cause loss of speech, memory or paralysis but can be severe enough to cause immediate
death
Symptoms: sudden weakness or numbness to one side of body, sudden loss of vision, loss of
speech or understanding, sudden severe headache, unexplained dizziness
Prevention: reduce high blood pressure, reduce stress, dietary changes
Hemophilia
Sex linked inherited condition caused by recessive allele
More common in males
Blood in person fails to clot or clots very slowly after injury
Once treated with blood transfusions but now there are blood factor treatments
Heart murmur- result of defective heart valves that do not close completely so blood squirts back into
chamber it just left
Mononucleosis
Symptoms: low energy, chronic sore throat, low grade fever, tired/achy feeling, enlarged spleen