Download BLOOD and CARDIOVASCULAR SYSTEM

BLOOD
Blood
• The only fluid tissue in the human body
• Classified as a connective tissue
– Living cells = formed elements
– Non-living matrix = plasma
Blood
Physical Characteristics of Blood
• Color range
– Oxygen-rich blood is scarlet red
– Oxygen-poor blood is dull red
• pH must remain between 7.35–7.45
• Blood temperature is slightly higher
than body temperature
Blood Plasma
• Composed of approximately 90 percent
water
• Includes many dissolved substances
– Nutrients
– Salts (metal ions)
– Respiratory gases
– Hormones
– Proteins
– Waste products
Plasma Proteins
• Albumin – regulates osmotic pressure
• Clotting proteins – help to stop blood
loss when a blood vessel is injured
• Antibodies – help protect the body from
antigens
Formed Elements
• Erythrocytes = red blood cells
• Leukocytes = white blood cells
• Platelets = cell fragments
Photomicrograph of a Blood Smear
Erythrocytes (Red Blood Cells)
• The main function is to carry oxygen
• Contains hemoglobin
• Anatomy of circulating erythrocytes
– Biconcave disks
– Essentially bags of hemoglobin
– Anucleate (no nucleus)
– Contain very few organelles
• 4 - 6 million per mm3 of blood
Hemoglobin
• Iron-containing protein
• Binds strongly, but reversibly, to oxygen
• Each hemoglobin molecule has four
oxygen binding sites
• Each erythrocyte has 250 million
hemoglobin molecules
Homeostatic Imbalance
• Anemia – decrease in oxygen-carrying ability of blood
• May be caused by:
– Low red blood cell count (RBC)
– Abnormal or deficient hemoglobin
– Lack of B12 or intrinsic factor
– Lack of iron
– Cancer
• Sickle cell anemia – genetically defective hemoglobin
• Polycythemia – abnormal increase in RBC
– May be from bone marrow cancer or living at high
altitudes
– Causes increased viscosity of blood
Sickle Cell Anemia
Leukocytes (White Blood Cells)
• Crucial in the body’s defense against
disease
• These are complete cells, with a
nucleus and organelles
• Able to move into and out of blood
vessels (diapedesis)
• Can move by ameboid motion
• Can respond to chemicals released by
damaged tissues
Leukocyte Levels in the Blood
• Normal levels are between 4,000 and
11,000 cells per mm3
• Abnormal leukocyte levels
– Leukocytosis
• Above 11,000 leukocytes/ml
• Generally indicates an infection
• Could indicate leukemia (WBC
cancer)
– Leukopenia
• Abnormally low leukocyte level
• Commonly caused by certain drugs
Platelets
• Derived from ruptured cells
• Needed for the clotting process
• Normal platelet count is 250,000 500,000/mm3
Hematopoiesis
• Blood cell formation
• Occurs in red bone marrow
• All blood cells are derived from a
common stem cell (hemocytoblast)
• Hemocytoblast differentiation
– Lymphoid stem cell produces
lymphocytes
– Myeloid stem cell produces other
formed elements
Fate of Erythrocytes
• Unable to divide, grow, or synthesize
proteins
• Wear out in 100 to 120 days
• When worn out, are eliminated by
phagocytes in the spleen or liver
• Lost cells are replaced by division of
hemocytoblasts
Control of Erythrocyte Production
• Rate is controlled by a hormone
(erythropoietin)
• Kidneys produce most erythropoietin
as a response to reduced oxygen levels
in the blood
• Homeostasis is maintained by negative
feedback from blood oxygen levels
Control of Erythrocyte Production
Hemostasis
• Stoppage of blood flow
• Result of a break in a blood vessel
• Hemostasis involves three phases
– Platelet plug formation
– Vascular spasms
– Coagulation
Hemostasis – blooding clotting
Platelet Plug Formation
• Collagen fibers are exposed by a break
in a blood vessel
• Platelets become “sticky” and cling to
fibers
• Anchored platelets release chemicals to
attract more platelets
• Platelets pile up to form a platelet plug
Vascular Spasms
• Anchored platelets release serotonin
• Serotonin causes blood vessel muscles
to spasm
• Spasms narrow the blood vessel,
decreasing blood loss
Coagulation
• Injured tissues release thromboplastin
• PF3 (a phospholipid) interacts with
thromboplastin, blood protein clotting
factors, and calcium ions to trigger a
clotting cascade
• Prothrombin activator converts
prothrombin to thrombin (an enzyme)
• Thrombin joins fibrinogen proteins into
hair-like fibrin
• Fibrin forms a meshwork (the basis
for a clot)
Blood Clotting
• Blood usually clots within 3 to 6 minutes
• The clot remains as endothelium
regenerates
• The clot is broken down after tissue
repair
Fibrin Clot
Undesirable Clotting
• Thrombus
– A clot in an unbroken blood vessel
– Can be deadly in areas like the heart
• Embolus
– A thrombus that breaks away and
floats freely in the bloodstream
– Can later clog vessels in critical
areas such as the brain
Bleeding Disorders
• Thrombocytopenia
– Platelet deficiency
– Even normal movements can cause
bleeding from small blood vessels
that require platelets for clotting
• Hemophilia
– Hereditary bleeding disorder
– Normal clotting factors are missing
Blood Groups and Transfusions
• Large losses of blood have serious
consequences
– Loss of 15 to 30 percent causes
weakness
– Loss of over 30 percent causes
shock, which can be fatal
• Transfusions are the only way to
replace blood quickly
• Transfused blood must be of the same
blood group
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)
Human Blood Groups
• There are over 30 common red blood
cell antigens
• The most vigorous transfusion reactions
are caused by ABO and Rh blood group
antigens
ABO Blood Groups
• Based on the presence or absence of
two antigens
– Type A (only A antigen)
– Type B (only B antigen)
– Type AB (both A and B antigen)
– Type O (neither A or B)
Rh Blood Groups
• Named because of the presence or
absence of one of eight Rh antigens
(agglutinogen D)
• Most Americans are Rh+
• Problems can occur in mixing Rh+ blood
into a body with Rh– blood
Rh Dangers During Pregnancy
• Danger is only when the mother is Rh– and the
father is Rh+, and the child inherits the Rh+
factor
• The mismatch of an Rh– mother carrying an Rh+ baby
can cause problems for the unborn child
– The first pregnancy usually proceeds without
problems
– The immune system is sensitized after the
first pregnancy
– In a second pregnancy, the mother’s immune
system produces antibodies to attack the Rh+
blood (hemolytic disease of the newborn)
Developmental Aspects of Blood
• Sites of blood cell formation
– The fetal liver and spleen are early
sites of blood cell formation
– Bone marrow takes over
hematopoiesis by the seventh month
• Fetal hemoglobin differs from
hemoglobin produced after birth
CARDIOVASCULAR SYSTEM
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
• Location
– Thorax between the lungs
– Pointed apex directed toward left hip
• About the size of your fist
The Heart
The Heart: 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
• Pericarditis – inflammation of pericardium,
which causes a decrease in serous fluid
The Heart: 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
External Heart Anatomy
The 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
Blood Circulation
The Heart: Valves
• Allow blood to flow in only one direction
• Four valves
– Atrioventricular valves – between atria
and ventricles
• Bicuspid valve or mitral (left)
• Tricuspid valve (right)
– Semilunar valves between ventricle
and artery
• Pulmonary semilunar valve
• Aortic semilunar valve
The Heart: Valves
• Valves open as blood is pumped through
• Held in place by chordae tendineae
(“heart strings”)
• Close to prevent backflow
Operation of Heart Valves
The Heart: Associated Great Vessels
• Aorta
– Leaves left ventricle
• Pulmonary arteries
– Leave right ventricle
• Vena cava
– Enters right atrium
• Pulmonary veins (four)
– Enter left atrium
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
Homeostatic Imbalance
• Valvular stenosis – valve flaps become
stiff, often from endocarditis (bacterial
infection of endocardium)
• Faulty valves may be replaced by synthetic
or pig valves
• Angina pectoris – chest pain as a result of
the myocardium being deprived of oxygen
• Myocardial infarction (heart attack) –
prolonged angina that kills heart cells
The Heart: Conduction System
• Intrinsic conduction system
(nodal system)
– Heart muscle cells contract, without
nerve impulses, in a regular and
continuous way
The Heart: Conduction System
• Special tissue sets the pace
• Sinoatrial node or pacemaker
– In right atrium
– Starts impulse
• Atrioventricular node
– At junction of right atrium and
ventricle
• Atrioventricular bundle
– In interventricular septum
• Bundle branches
• Purkinje fibers
– In wall of ventricles
Heart Contractions
Filling of Heart Chambers – the Cardiac Cycle
Homeostatic Imbalance
• Heart block – damage to AV node causing
ventricular contraction to beat at own rate
(much slower)
• Ischemia – lack of adequate blood supply to
heart muscle
• Fibrillation – rapid uncoordinated shuddering of
heart muscle (caused by ischemia)
• Tachycardia – rapid heart rate (over 100 bpm)
• Brachycardia – much slower rate (under 60
bpm)
The Heart: Cardiac Cycle
•
•
•
•
Atria contract simultaneously
Atria relax, then ventricles contract
Systole = contraction
Diastole = relaxation
The Heart: Cardiac Cycle
• 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
• Heart sounds – lub (closing AV valves) dub
(semilunar valves close)
• Heart murmur – abnormal or unusual
heart sounds
– From blood hitting thin walls
– Valves not closing tightly
– Narrowed valves
The Heart: Cardiac Output
• 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
Cardiac Output Regulation
The Heart: 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
The Heart: Regulation of Heart Rate
• Increased heart rate
– Sympathetic nervous system
• Crisis
• Low blood pressure
– Hormones
• Epinephrine
• Thyroxine
– Exercise
– Decreased blood volume
The Heart: Regulation of Heart Rate
• Decreased heart rate
– Parasympathetic nervous system
– High blood pressure or blood volume
– Increased venous return
Homeostatic Imbalance
• Congestive heart failure – pumping
efficiency of heart is diminished
– Often from clogging of coronary
arteries (atherosclerosis), persistent
high blood pressure, and MI
• Pulmonary edema – left side of heart fails
so blood not pumped out to body, but blood
continues to move into lungs causing fluid
to leak into lungs
– Can lead to suffocation
Blood Vessels: The Vascular System
• Taking blood to the tissues and back
– Arteries (away from heart)
– Arterioles
– Capillaries
– Venules
– Veins (toward heart)
The Vascular System
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
Capillary Beds
• True capillaries –
exchange vessels
• Oxygen and
nutrients
cross to cells
• Carbon
dioxide and
metabolic
waste
products
cross into
blood
Diffusion at Capillary Beds
Homeostatic Imbalance
• Varicose veins – pooling of blood in feet
and legs and inefficient venous return
resulting from inactivity or pressure on
the veins; veins become twisted and
dilated
• Thrombophlebitis – inflammation of vein
that results when clot forms in a vessel
with poor circulation; if the clot moves to
the lungs it causes a pulmonary embolism
Major Arteries of Systemic Circulation
Major Veins of Systemic Circulation
Arterial Supply of the Brain
Hepatic Portal Circulation
Circulation to the Fetus
Pulse
• 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
Measuring Arterial Blood Pressure
Comparison of Blood Pressures in Different Vessels
Blood Pressure: Effects of Factors
• Neural factors
– Autonomic nervous system
adjustments (sympathetic division)
• Renal factors
– Regulation by altering blood volume
– Renin – hormonal control
Blood Pressure: Effects of Factors
• Temperature
– Heat has a vasodilation effect
– Cold has a vasoconstricting effect
• Chemicals
– Various substances can cause
increases or decreases
• Diet
Factors Determining Blood Pressure
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;
weakens myocardium and causes
atherosclerosis
Capillary Exchange
• Substances exchanged due to
concentration gradients
– Oxygen and nutrients leave the blood
– Carbon dioxide and other wastes leave
the cells
Capillary Exchange: 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