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Cardiovascular <3

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Amber Britton

on 15 April 2015

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Transcript of Cardiovascular <3

Cardiovascular <3
The Cardiovascular system -- A closed system of the heart and blood vessels
The heart pumps blood
Blood vessels allow blood to circulate to all parts of the body
The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

the Heart
Located in the thorax between the lungs; Pointed apex directed toward left hip
About the size of your fist

Coverings:
Pericardium – a double serous membrane
Visceral pericardium
Next to heart
Parietal pericardium
Outside layer
Serous fluid fills the space between the layers of pericardium

Heart Wall – three layers
• Epicardium -- Outside layer
• This layer is the parietal pericardium
• Connective tissue layer
• Myocardium -- Middle layer
• Mostly cardiac muscle
• Endocardium -- Inner layer
• Endothelium

Heart Chambers -- right and left side act as separate pumps
• Four chambers
• Atria – receiving chambers
• Right atrium
• Left atrium
• Ventricles -- discharging chambers
• Right ventricle
• Left ventricle

Atrioventricular valves –
between atria and ventricles
• Bicuspid valve (left)
• Tricuspid valve (right)

Semilunar valves –
between ventricle and artery
• Pulmonary semilunar valve
• Aortic semilunar valve
Heart Valves -- allow blood to flow in only one direction
• Valves open as blood is pumped through
• Held in place by chordae tendineae (“heart strings”)
• Close to prevent backflow
• Four valves

Great Vessels
Aorta –
leaves left ventricle
Pulmonary arteries –
leaves right ventricle
Vena cava –
enters right atrium
Pulmonary veins (four) –
enters left atrium

Vena Cava
Conduction System
Intrinsic conduction system (nodal system)
muscle cells contract, without nerve impulses, in a regular, continuous way
Special tissue sets the pace
Sinoatrial node (pacemaker)
Atrioventricular node
Atrioventricular bundle
Bundle branches
Purkinje fibers



Coronary Circulation
• Blood in the heart chambers does not nourish the myocardium
• The heart has its own nourishing circulatory system
• Coronary arteries
• Cardiac veins
• Blood empties into the right atrium via the coronary sinus


Conduction System
• Intrinsic conduction system (nodal system)
• muscle cells contract, without nerve impulses, in a regular,
continuous way
• Special tissue sets the pace
• Sinoatrial node (pacemaker)
• Atrioventricular node
• Atrioventricular bundle
• Bundle branches
• Purkinje fibers

• Heart Contractions
• Contraction is initiated by the sinoatrial node
• Sequential stimulation occurs at other autorhythmic cells

• Cardiac Circle
• Atria contract simultaneously
• Atria relax, then ventricles contract
• Systole = contraction
• Diastole = relaxation
• Cardiac cycle – events of one complete heart beat
Mid-to-late diastole – blood flows into ventricles
Ventricular systole – blood pressure builds before ventricle contracts, pushing out blood
Early diastole – atria finish re-filling, ventricular pressure is low


Cardiac output (CO)
Amount of blood pumped by each side of the heart in one minute
CO = (heart rate [HR]) x (stroke volume [SV])
• Stroke volume
Volume of blood pumped by each ventricle in one contraction

Regulation of Heart Rate
Stroke volume usually remains relatively constant
Starling’s law of the heart – the more that the cardiac muscle is stretched, the stronger the contraction
Changing heart rate is the most common way to change cardiac output
Increased heart rate
Sympathetic nervous system
Crisis
Low blood pressure
Hormones
Epinephrine
Thyroxine
Exercise
Decreased blood volume
Decreased heart rate
Parasympathetic nervous system
High blood pressure or blood volume
Decreased venous return



Normal CO = (75 beats/min) x (70 mL/beat)
Normal CO =~ 5000 mL/min
Blood Vessels: The Vascular System
• Taking blood to the tissues and back
• Arteries
• Arterioles
• Capillaries
• Venules
• Veins
freeways
alleys
Anatomy: three layers (tunics)
• Tunic interna
• Endothelium
• Tunic media
• Smooth muscle (changes diameter of vessel)
• Controlled by sympathetic nervous system
• Tunic externa
• Mostly fibrous connective tissue
Differences Between Blood Vessel Types:
Walls of arteries are the thickest
Lumens of veins are larger
Skeletal muscle “milks” blood in veins toward the heart
Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue
Movement of Blood Through Vessels
Most arterial blood is pumped by the heart
Veins use the milking action of muscles to help move blood

Capillary Beds
Capillary beds consist of two types of vessels
Vascular shunt – directly connects an arteriole to a venule
True capillaries – exchange vessels
Oxygen and nutrients cross to cells
Carbon dioxide and metabolic waste products cross into blood
Diffusion at Capillary Beds

roads
Major Arteries of Systemic Circulation
Major Veins of Systemic Circulation
Arterial Supply of the Brain
• Hepatic Portal Circulation
Circulation to the Fetus
Pulse -- pressure wave of blood
Monitored at “pressure points” where pulse is easily palpated

Blood Pressure
Measurements by health professionals are made on the pressure in large arteries
Systolic – pressure at the peak of ventricular contraction
Diastolic – pressure when ventricles relax
Pressure in blood vessels decreases as the distance away from the heart increases

Comparison of Blood Pressures in Different Vessels
Blood Pressure Effects & Factors
Neural factors
Autonomic nervous system adjustments (sympathetic division)
Renal factors
Regulation by altering blood volume
Renin – hormonal control
Temperature
Heat has a vasodilation effect
Cold has a vasoconstricting effect
Chemicals
Various substances can cause increases or decreases
Diet

Variations in Blood Pressure
Human normal range is variable
Normal
140–110 mm Hg systolic
80–75 mm Hg diastolic
Hypotension
Low systolic (below 110 mm HG)
Often associated with illness
Hypertension
High systolic (above 140 mm HG)
Can be dangerous if it is chronic

Capillary Exchange
Substances exchanged due to concentration gradients
Oxygen and nutrients leave the blood
Carbon dioxide and other wastes leave the cells
Mechanisms
Direct diffusion across plasma membranes
Endocytosis or exocytosis
Some capillaries have gaps (intercellular clefts)
Plasma membrane not joined by tight junctions
Fenestrations of some capillaries
Fenestrations = pores
Developmental Aspects of the Cardiovascular System
A simple “tube heart” develops in the embryo and pumps by the fourth week
The heart becomes a four-chambered organ by the end of seven weeks
Few structural changes occur after the seventh week
Blood -- The only fluid tissue in the human body
Classified as a connective tissue
Living cells = formed elements (RBC, WBC, & platelets)
Non-living matrix = plasma
erythrocytes
leukocytes
Erythrocytes -- red blood cell
basically sacks of hemoglobin (Iron-containing protein that binds strongly to oxygen)
44% of blood

Platelets = cell fragments
Derived from ruptured cells
Needed for the clotting process
0.5% of blood

Plasma = 55% of blood
90% water
10% dissolved substances
Nutrients
Salts (metal ions)
Respiratory gases
Hormones
Proteins
Waste products
Hematopoiesis – blood cell formation
Hemostasis – stoppage of blood flow
• Coagulation
• Blood usually clots within 3 to 6 minutes
• The clot remains as endothelium regenerates
• The clot is broken down after tissue repair

Human Blood Groups
Blood contains genetically determined proteins
A foreign protein (
antigen
) may be attacked by the immune system
Blood is “typed” by using
antibodies
that will cause blood with certain proteins to clump (agglutination)

ABO Blood Groups -- based on the presence or absence of two antigens
Type A -- the presence of antigen A
Type B -- the presence of antigen B
Type O -- the lack of these antigens A & B
Type AB -- the presence of both A & B antigens

Rh Blood Groups
Named because of the presence or absence of one of eight Rh antigens
Most Americans are Rh+
Problems can occur in mixing Rh+ blood into a body with Rh– blood


Blood Typing
Blood samples are mixed with anti-A and anti-B serum
Coagulation or no coagulation leads to determining blood type
Typing for ABO and Rh factors is done in the same manner

Leukocytes = white blood cells
Crucial in the body’s defense against disease
0.5% of blood
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