Transcript Varicose veins

BIO 238




Heart and blood vessels
are part of the
cardiovascular system
Heart pumps blood
Arteries carry blood away
from the heart to
capillaries
Veins carry blood from
capillaries to heart

Heart Chambers
◦ 2 atria
 Receive blood from
veins
◦ 2 ventricles
 Pump blood to arteries
◦ Atrial septum
◦ Interventricular
septum
◦ Heart is a double pump
 Left atria and ventricle: left pump
 Right atria and ventricle: right pump
◦ Differences in wall thickness depend upon
work performed by the chamber
 Ventricles have more muscle then atria: atria pump
to ventricle, ventricles pump out to body areas
 Left ventricle is most muscular: pumps blood to
body
 Right ventricle has less muscle: pumps blood to
lungs only

Heart Valves:
◦ Allows blood to flow in one directionAtrioventricular
valves
 Allows flow from atria to ventricles
 Tricuspid valve: between R atrium and ventricle
 Bicuspid (mitral) valve: between L atrium and ventricle
◦ Semilunar valves
 Located at base of blood vessels attached to ventricles
 Pulmonary semilunar valve: between R ventricle and
pulmonary trunk
 Aortic semilunar valve: between L ventricle and aorta

Includes:
◦ Systole: contraction phase
◦ Diastole: relaxation phase

When atria and ventricles are relaxed, blood
flows into atria, then through open AV valves
into ventricles
◦ Semilunar valves closed due to greater pressure in
arteries than in ventricles

Atrial systole forces more blood into relaxed
ventricles

Ventricular systole (atrial diastole) increases blood
pressure in ventricles
◦ Closes AV valves, opens semilunar valves
◦ Blood moves from ventricles and into arteries
 Ventricular
diastole (atrial diastole)
follows
◦ Allows AV valves to open and
semilunar valves close
◦ Cycle repeats
 Heart
Sounds
◦ Lub-dup (pause) lub-dup
◦ Lub: closing of AV valves during
ventricular diastole
◦ Dup: closing of semilunar valves
during ventricular systole
 Flow
of Blood Through the Heart
◦ Two basic circuits of blood flow
 Pulmonary circuit
 Deoxygenated blood flows from R ventricle to
lungs
 Oxygenated blood flows from lungs to L atrium
 Systemic Circuit
 Oxygenated blood flows L ventricle to body
 Deoxygenated blood flows from body to R
atrium

Steps of heart circulation
◦ Superior and inferior vena cava return blood from
body to R atrium
◦ Pulmonary veins return blood from lungs to L atrium
◦ Atria push blood into ventricles
◦ R ventricle pumps blood into pulmonary trunk
 Blood moves into R and L pulmonary arteries, which
head to lungs
◦ L ventricle pumps blood into the aorta, which carries
blood out to body

Conduction system consists of specialized muscle
tissue that acts as neural tissue
◦ Spontaneously form impulses
◦ Impulses cause myocardium to contract

Components include
◦
◦
◦
◦
Sinoatrial (SA) node
Atrioventricular (AV) node
AV bundle
Purkinje fibers

Sinoatrial node
◦ Pacemaker of the heart
◦ Rhythmically forms impulses to initiate each heartbeat
◦ Impulses cause simultaneous contraction of atria

Atrioventricular node
◦ Receives impulse from SA node
◦ Delay in passing through node allows time for ventricular
filling and the completion or atrial contraction
◦ Passes impulse to the AV bundle

AV bundle
◦ Divides into L and R branches
◦ Carries impulse down ventricular septum and up
lateral ventricle walls
◦ Forms Purkinje fibers

Purkinje fibers
◦ Carry impulse to myocardium of ventricles
◦ Contraction occurs from the apex upward

Electrocardiogram (ECG or EKG)
◦ Recording of the electrical current generated during
heart contraction
◦ Performed by an electrocardiograph
◦ Electrocardiogram has three distinct waves
 P wave: atrial depolarization
 QRS wave: ventricular depolarization
 T wave: ventricular repolarization


Numerous factors can act on the SA node to
increase or decrease heart rate
Autonomic Regulation
◦ Cardiac center in the medulla oblongata
 Stimulated by excessive blood pressure and emotional
factors, such as grief and depression
 Sympathetic neurons in the cardiac center cause an
increase in heart rate
 Parasympathetic neurons in the cardiac center cause a
decrease in heart rate

Other factors affecting heart rate
◦ Age: resting rate declines with age
◦ Sex: females slightly faster than males
◦ Physical condition: good condition means
lower heart rate
◦ Temperature: increase in temperature
increases rate
◦ Epinephrine: increases strengthens heart rate
◦ Thyroxine: produces a lesser but longer
lasting increase in heart rate
◦ Blood calcium levels
 Low levels slow heart rate
 Increased levels increase heart rate and prolong
contraction
◦ Blood potassium levels
 Increased levels decrease both heart rate and force of
contraction
 Low levels can cause abnormal heart rhythms

Arteries
◦ Carry blood away from the heart
◦ Branch into smaller arteries, eventually forming
arterioles
 Play an important role in controlling blood flow and blood
pressure

Capillaries
◦ Most numerous and smallest vessels
◦ RBCs pass through one at a time
◦ Thin walls allow exchange of materials between blood
and cells

Veins
◦ Blood flows from capillaries into venules
◦ Venules unite to form larger veins, which in turn
unite to form even larger veins
◦ Valves exist in large veins to prevent blood
backflow and aid in venous blood return
◦ Veins hold ~60% of blood volume at any instant
 Reducing venous volume can compensate for blood loss or
increase in muscle activity

Blood flows from high pressure areas to low
pressure areas
◦ Greatest in ventricles and lowest in atria

Ventricles create the pressure

Pressure decreases with increased distance from the
heart
◦ Due to increase in overall cross-sectional area of vessels
due to branching
◦ Due to low pressure,
veins require assistance
to return blood to the
heart
 Skeletal muscle
contractions
 Contraction compresses
veins, forcing blood
from one valved
segment to another
 Important in arms and
legs
 Respiratory movements
 Downward contraction of diaphragm during
inspiration
 Decreases thoracic pressure and increases
abdominal pressure
 High pressure in abdominal veins forces
blood into low pressure thoracic veins

Arterial blood pressure in the systemic circuit
◦ Systolic blood pressure
 Highest pressure during ventricular systole
◦ Diastolic blood pressure
 Lowest pressure during ventricular diastole
◦ Pulse pressure is difference between systolic and
diastolic blood pressures
 Causes the pulse: expansion and contraction of arterial
walls
◦ Cardiac output
 Volume of blood pumped by heart in one minute
 Determined by heart rate and blood volume pumped in
contraction
 Increase cardiac output, increase blood pressure
 Decrease cardiac output, decrease blood pressure
◦ Blood volume
 Decrease in blood volume, decrease in blood pressure
 Increase in blood volume, increase in blood pressure
◦ Peripheral resistance
 Friction of blood against blood vessel walls
 Constriction of arterioles increase both resistance and
blood pressure
 Dilation of arterioles decreases both resistance and
blood pressure
◦ Viscosity
 Thickness of blood
 Determined by blood cell concentration and plasma proteins
 Increase viscosity increases blood pressure
 Decrease viscosity decreases blood pressure

Control of Peripheral Resistance
◦ Vasomotor center in the medulla
 Increases frequency of sympathetic impulses to
cause vasoconstriction
 Increases blood pressure and velocity
 Accelerates oxygen and carbon dioxide transport rates
 Decreases frequency of sympathetic impulses to
cause vasodilation
 Lowers blood pressure and velocity
 Activity of vasomotor area can be modified
 Affected by epinephrine, impulses from higher brain area,
impulses from pressure and chemoreceptors
 Decrease in pressure, pH, or oxygen causes
vasoconstriction
◦ Autoregulation
 Blood vessels are affected by localized
changes in blood composition
 Oxygen, carbon dioxide, pH
 Effects can override vasomotor control
 Increases rate of exchange of materials
between cells and capillaries
 Example: decrease in oxygen and increase in
carbon dioxide causes vasodilation to increase
blood flow

Arrhythmia
◦ Abnormal heart beat
◦ Caused by factors such as damage to conduction system and
drugs
 Bradycardia
 Heart rate less then 60 beats/min
 Tachycardia
 Heart rate over 100 beats/min
 Heart flutter
 Heart rate over 200-300 beats/min
 Fibrillation
 Very rapid heart rate with uncoordinated contraction
 Blood is not pumped from ventricles

Congestive heart failure (CHF)

Heart murmurs

Myocardial infarction

Pericarditis
◦ Acute or chronic inability of hear to pump out returned to it
◦ Symptoms include fatigue, edema, accumulation of blood
in organs
◦ Possible cause is atherosclerosis
◦ Unusual heart sounds associated with defective heart
valves
◦ Death of myocardium due to coronary artery blockage
◦ Heart attack
◦ Inflammation of pericardium due to viral or bacterial
infection

Aneurysm
◦ Weakened vessel wall bulges, forming balloon-like sac
filled with blood
◦ Rupture can be fatal

Arteriosclerosis
◦ Hardening of the arteries
◦ Due to calcium deposits accumulating in tunica media

Atherosclerosis
◦ Formation of fatty deposits in the tunica interna of arteries
◦ Plagues reduce lumen size and increase probability of
blood clot formation

Hypertension
◦ Chronic high blood pressure
◦ Pressure exceeds 140/90
◦ Pre-hypertension
 A systolic pressure between 120-139 and diastolic pressure
between 80-89

Phlebitis

Varicose veins
◦ Inflammation of a vein
◦ Most common in the legs
◦ Thrombophlebitis involves the formation of blood clots at
the inflammation site
◦ Dilated, swollen veins due to malfunctioning valves
◦ Causes include heredity, pregnancy, and lack of physical
activity
◦ Hemorrhoids