Transport Systems in Animals

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Transport Systems in Animals Circulatory Systems
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What is the role of the circulatory system?

• Maintain internal homeostasis
• What are some things that would need to be
  balanced within the body?
• Maintain temperature, O2 conc., blood glucose,
  etc.
• Deliver and remove nutrients and gases to and
  from the body
• Maintain cells in a fluid environment that allows
  for these exchanges to occur

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To do all of this, the circulatory system must
come into contact with most tissues in the human
body.
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Which of the organisms below have transport
systems? Which do not? Explain your reasoning!
How can the paramecium and hydra thrive with no
circulatory system?
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Open vs. Closed Systems
Which system seems more efficient? What are your
reasons?
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Open Circulatory System

• Body fluid is pumped through open ended vessels
  and bathes organs.
• Occurs in insects, crabs, and other animals that
  have exoskeletons
• Body fluid is circulated by the heart
• How efficient is this? Why?

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Why Do Bugs Make Such a Mess?
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Closed Circulatory Systems

• Blood is confined to major vessels which branch
  into smaller vessels that carry blood to organs.
• Blood is pumped through the body by the heart.
• Blood flow is faster than in an open system
• If you are a cheetah, what type of circulatory
  system would you need? Why?

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Several types of blood vessels exist in the
circulatory systems of vertebrates.

• What are the three types of blood vessels?
• Arteries, capillaries, veins

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Blood Vessels
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Blood Vessels

• Blood travels through three types of vessels
• What are some differences you notice between
  these vessels?
• 1. Arteries 2. Capillaries 3. Veins

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Blood Vessels

• Blood is carried in a closed system of vessels
  that begins and ends at the heart
• The three major types of vessels are arteries,
  capillaries, and veins
• Arteries carry blood away from the heart, veins
  carry blood toward the heart
• Capillaries contact tissue cells and directly
  serve cellular needs

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Elastic (Conducting) Arteries

• Thick-walled arteries near the heart the aorta
  and its major branches
• Large lumen allow low-resistance conduction of
  blood
• Contain elastin in all three tunics
• Withstand and smooth out large blood pressure
  fluctuations
• Allow blood to flow fairly continuously through
  the body

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Arteries of the Head and Neck
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Arteries of the Brain
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Arteries of the Upper Limbs and Thorax
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Arteries of the Abdomen
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Arteries of the Lower Limbs
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Muscular (Distributing) Arteries and Arterioles

• Muscular arteries distal to elastic arteries
  deliver blood to body organs
• Have thick tunica media with more smooth muscle
  and less elastic tissue
• Active in vasoconstriction
• Arterioles smallest arteries lead to capillary
  beds
• Control flow into capillary beds via vasodilation
  and constriction

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Capillaries

• Capillaries are the smallest blood vessels
• Walls consisting of a thin tunica interna, one
  cell thick
• Allow only a single RBC to pass at a time
• Pericytes on the outer surface stabilize their
  walls
• There are three structural types of capillaries
  continuous, fenestrated, and sinusoids

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Capillary Beds

• A microcirculation of interwoven networks of
  capillaries, consisting of
• Vascular shunts metarteriolethoroughfare
  channel connecting an arteriole directly with a
  postcapillary venule
• True capillaries 10 to 100 per capillary bed,
  capillaries branch off the metarteriole and
  return to the thoroughfare channel at the distal
  end of the bed

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Venous System Veins

• Veins are
• Formed when venules converge
• Composed of three tunics, with a thin tunica
  media and a thick tunica externa consisting of
  collagen fibers and elastic networks
• Capacitance vessels (blood reservoirs) that
  contain 65 of the blood supply

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Venous System Veins

• Veins have much lower blood pressure and thinner
  walls than arteries
• To return blood to the heart, veins have special
  adaptations
• Large-diameter lumens, which offer little
  resistance to flow
• Valves (resembling semilunar heart valves), which
  prevent backflow of blood
• Venous sinuses specialized, flattened veins
  with extremely thin walls (e.g., coronary sinus
  of the heart and dural sinuses of the brain)

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Factors Aiding Venous Return
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What is the purpose of the valves found in veins?
Keep blood flowing toward the heart.
So what happened here?
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Why must the capillary walls be so thin?
So materials can diffuse through the wall for
exchange.
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Veins of Systemic Circulation
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Veins of the Head and Neck
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Veins of the Brain
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Veins of the Upper Limbs and Thorax
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Veins of the Abdomen
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Veins of the Pelvis and Lower Limbs
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Blood Vessels - Summary

• Arteries carry blood away from the heart,
  thickest walls
• Veins carry blood toward the heart, thinner
  walls, one-way valves
• Capillaries extremely thin walls, sites of
  exchange in lungs and body cells

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• ARTHERIOSCLEROSISThe narrowing of blood vessels
  due to build- up of fats that turn into plaque on
  the artery and vein walls.

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How do these three different circulatory systems
compare?
What are systemic capillaries? Capillaries that
are located throughout the body
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Circulation in Fish
How many chambers does the heart have? -2
chambered heart How many loops does this
circulatory system have? 1 Blood is oxygenated in
gills and travels to the body Heart? gills?
systemic? heart
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Circulation In Amphibians and Reptiles
How many chambers does the reptilian heart
have? -3 chambered heart How many loops does this
circulatory system have? 2 (double loop
circulatory system) Trace the blood flow through
the body Heart? lungs? heart? systemic Where is
the inefficiency in the amphibian 3-chambered
system?
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The Heart and Blood Flow in Mammals

• How many chambers are there?
• -4 chambered heart
• How many loops?
• 2
• Trace the blood flow through the body
• Heart? lung? heart? systems
• How is this heart more efficient than the
  reptilian heart?

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Heart Animation
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Heart Anatomy
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The Circulatory System
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Coverings of the Heart PhysiologyThe
pericardium

• Protects and anchors the heart
• Prevents overfilling of the heart with blood
• Allows for the heart to work in a relatively
  friction-free environment

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Heart Wall

• Epicardium visceral layer of the serous
  pericardium
• Myocardium cardiac muscle layer forming the
  bulk of the heart
• Fibrous skeleton of the heart crisscrossing,
  interlacing layer of connective tissue
• Endocardium endothelial layer of the inner
  myocardial surface

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• External Heart Major Vessels of the Heart
  (Anterior View)
• Vessels returning blood to the heart include
• Superior and inferior venae cavae
• Right and left pulmonary veins
• Vessels conveying blood away from the heart
  include
• Pulmonary trunk, which splits into right and left
  pulmonary arteries
• Ascending aorta (three branches)
  brachiocephalic, left common carotid, and
  subclavian arteries

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External Heart Major Vessels of the Heart
(Posterior View)

• Vessels returning blood to the heart include
• Right and left pulmonary veins
• Superior and inferior venae cavae
• Vessels conveying blood away from the heart
  include
• Aorta
• Right and left pulmonary arteries

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Gross Anatomy of Heart Frontal Section
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Atria of the Heart

• Atria are the receiving chambers of the heart
• Each atrium has a protruding auricle
• Pectinate muscles mark atrial walls
• Blood enters right atria from superior and
  inferior venae cavae and coronary sinus
• Blood enters left atria from pulmonary veins

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Ventricles of the Heart

• Ventricles are the discharging chambers of the
  heart
• Papillary muscles and trabeculae carneae muscles
  mark ventricular walls
• Right ventricle pumps blood into the pulmonary
  trunk
• Left ventricle pumps blood into the aorta

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Pathway of Blood Through the Heart and Lungs

• Right atrium ? tricuspid valve ? right ventricle
• Right ventricle ? pulmonary semilunar valve ?
  pulmonary arteries ? lungs
• Lungs ? pulmonary veins ? left atrium
• Left atrium ? bicuspid valve ? left ventricle
• Left ventricle ? aortic semilunar valve ? aorta
• Aorta ? systemic circulation

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Pathway of Blood Through the Heart and Lungs
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Coronary Circulation Arterial Supply
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Coronary Circulation Venous Supply
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Heart Valves

• Heart valves ensure unidirectional blood flow
  through the heart
• Atrioventricular (AV) valves lie between the
  atria and the ventricles
• AV valves prevent backflow into the atria when
  ventricles contract
• Chordae tendineae anchor AV valves to papillary
  muscles

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Heart Valves

• Aortic semilunar valve lies between the left
  ventricle and the aorta
• Pulmonary semilunar valve lies between the right
  ventricle and pulmonary trunk
• Semilunar valves prevent backflow of blood into
  the ventricles

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Heart Valves
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Heart Valves
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Atrioventricular Valve Function
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Semilunar Valve Function
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Microscopic Anatomy of Heart Muscle
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The Heart
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The Mammalian Heart
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The Cardiac Cycle

• The heart is composed of cardiac muscle and each
  beat is a muscle contraction and relaxation
• Contraction Systolic Pressure
• Relaxation Diastolic pressure
• How is blood pressure written?
• Systolic / diastolic

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Heart Physiology Sequence of Excitation
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Heart Excitation Related to ECG
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Extrinsic Innervation of the Heart

• Heart is stimulated by the sympathetic
  cardioacceleratory center
• Heart is inhibited by the parasympathetic
  cardioinhibitory center

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Electrocardiography
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Heart Sounds

• Heart sounds (lub-dup) are associated with
  closing of heart valves
• First sound occurs as AV valves close and
  signifies beginning of systole
• Second sound occurs when SL valves close at the
  beginning of ventricular diastole

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Cardiac Cycle

• Cardiac cycle refers to all events associated
  with blood flow through the heart
• Systole contraction of heart muscle
• Diastole relaxation of heart muscle

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Preload and Afterload
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Regulation of Heart Rate Autonomic Nervous
System

• Sympathetic nervous system (SNS) stimulation is
  activated by stress, anxiety, excitement, or
  exercise
• Parasympathetic nervous system (PNS) stimulation
  is mediated by acetylcholine and opposes the SNS
• PNS dominates the autonomic stimulation, slowing
  heart rate and causing vagal tone

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Factors Involved in Regulation of Cardiac Output
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Blood Pressure

• What is blood pressure?
• The force that blood exerts against vessel walls
• Is BP greater in arteries or veins?
• In arteries
• Find your pulse- what are you feeling here?
• Pulse is measure of BP
• Which would have a higher blood pressure,
  constricted blood or dilated vessels?
• Constricted vessels
• Does the BP have an effect on veins?
• No- the pressure is lost in the capillaries
• How, then does blood move in veins?

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• What is average blood pressure?
• 120/80 (mm Hg) of pressure on artery walls.
• Which part of the heart contracts first?
• The atria contract first, followed immediately by
  the ventricles.

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Systemic Blood Pressure

• The pumping action of the heart generates blood
  flow through the vessels along a pressure
  gradient, always moving from higher- to
  lower-pressure areas
• Pressure results when flow is opposed by
  resistance
• Systemic pressure
• Is highest in the aorta
• Declines throughout the length of the pathway
• Is 0 mm Hg in the right atrium
• The steepest change in blood pressure occurs in
  the arterioles

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Arterial Blood Pressure

• Systolic pressure pressure exerted on arterial
  walls during ventricular contraction
• Diastolic pressure lowest level of arterial
  pressure during a ventricular cycle
• Pulse pressure the difference between systolic
  and diastolic pressure
• Mean arterial pressure (MAP) pressure that
  propels the blood to the tissues
• MAP diastolic pressure 1/3 pulse pressure

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Blood Pressure
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• Cardiac Output (CO)
• Volume of blood pumped/ minute
• Stroke Volume (SV)
• Amount of blood pumped by the left ventricle each
  time it contracts (about 75 mL per beat for the
  average person)
• 75 X 70 5250 mL/min.
• CO is affected by heart rate and SV

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Alterations in Blood Pressure

• Hypotension low BP in which systolic pressure
  is below 100 mm Hg
• Hypertension condition of sustained elevated
  arterial pressure of 140/90 or higher
• Transient elevations are normal and can be caused
  by fever, physical exertion, and emotional upset
• Chronic elevation is a major cause of heart
  failure, vascular disease, renal failure, and
  stroke

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Hypotension

• Orthostatic hypotension temporary low BP and
  dizziness when suddenly rising from a sitting or
  reclining position
• Chronic hypotension hint of poor nutrition and
  warning sign for Addisons disease
• Acute hypotension important sign of circulatory
  shock
• Threat to patients undergoing surgery and those
  in intensive care units

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Hypertension

• Hypertension maybe transient or persistent
• Primary or essential hypertension risk factors
  in primary hypertension include diet, obesity,
  age, race, heredity, stress, and smoking
• Secondary hypertension due to identifiable
  disorders, including excessive renin secretion,
  arteriosclerosis, and endocrine disorders

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How Does Your Heart Beat?

• Can you control the beating of your own heart?
• No- the heart muscles contract on their own.
• The heart has a pacemaker, or SA node, that
  maintains the hearts rhythm.

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The pacemaker sets the tempo of the heartbeat.
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Blood Composition continued...
Diagramatic View
Real Blood Cells
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Overview of Blood Circulation

• Blood leaves the heart via arteries that branch
  repeatedly until they become capillaries
• Oxygen (O2) and nutrients diffuse across
  capillary walls and enter tissues
• Carbon dioxide (CO2) and wastes move from tissues
  into the blood

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Overview of Blood Circulation

• Oxygen-deficient blood leaves the capillaries and
  flows in veins to the heart
• This blood flows to the lungs where it releases
  CO2 and picks up O2
• The oxygen-rich blood returns to the heart

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Composition of Blood

• Blood is the bodys only fluid tissue
• It is composed of liquid plasma and formed
  elements
• Formed elements include
• Erythrocytes, or red blood cells (RBCs)
• Leukocytes, or white blood cells (WBCs)
• Platelets
• Hematocrit the percentage of RBCs out of the
  total blood volume

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Blood
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Blood is the Liquid Tissue

• 55 of blood is plasma (mostly water) carries
  nutrients, wastes and important proteins like
  antibodies and clotting factors.
• 45 is made of cells
• Red, white blood cells and platelets
• Erythrocytes (RBC)
• contain hemoglobin and carry oxygen
• Leukocytes (WBC) are usually stored in the bone
  marrow, and are the bodys defense system
• Platelets are pieces of white blood cells that
  are in charge of clotting

Red blood cell
Platelet
White blood cell
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Components of Whole Blood
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Physical Characteristics and Volume

• Blood is a sticky, opaque fluid with a metallic
  taste
• Color varies from scarlet (oxygen-rich) to dark
  red (oxygen-poor)
• The pH of blood is 7.357.45
• Temperature is 38?C, slightly higher than
  normal body temperature
• Blood accounts for approximately 8 of body
  weight
• Average volume of blood is 56 L for males, and
  45 L for females

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DistributionBlood transports

• Oxygen from the lungs and nutrients from the
  digestive tract
• Metabolic wastes from cells to the lungs and
  kidneys for elimination
• Hormones from endocrine glands to target organs

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RegulationBlood maintains

• Appropriate body temperature by absorbing and
  distributing heat
• Normal pH in body tissues using buffer systems
• Adequate fluid volume in the circulatory system

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• Blood plasma contains over 100 solutes,
  including
• Proteins albumin, globulins, clotting proteins,
  and others
• Nonprotein nitrogenous substances lactic acid,
  urea, creatinine
• Organic nutrients glucose, carbohydrates, amino
  acids
• Electrolytes sodium, potassium, calcium,
  chloride, bicarbonate
• Respiratory gases oxygen and carbon dioxide

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Erythrocytes (RBCs)

• Biconcave discs, anucleate, essentially no
  organelles
• Filled with hemoglobin (Hb), a protein that
  functions in gas transport
• Contain the plasma membrane protein spectrin and
  other proteins that
• Give erythrocytes their flexibility
• Allow them to change shape as necessary

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Structure of Hemoglobin
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Hemoglobin

• Oxyhemoglobin hemoglobin bound to oxygen
• Oxygen loading takes place in the lungs
• Deoxyhemoglobin hemoglobin after oxygen
  diffuses into tissues (reduced Hb)
• Carbaminohemoglobin hemoglobin bound to carbon
  dioxide
• Carbon dioxide loading takes place in the tissues
  

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Production of Erythrocytes

• Hematopoiesis blood cell formation
• Hematopoiesis occurs in the red bone marrow of
  the
• Axial skeleton and girdles
• Epiphyses of the humerus and femur
• Hemocytoblasts give rise to all formed elements

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Dietary Requirements of Erythropoiesis

• Erythropoiesis requires
• Proteins, lipids, and carbohydrates
• Iron, vitamin B12, and folic acid
• The body stores iron in Hb (65), the liver,
  spleen, and bone marrow
• Intracellular iron is stored in protein-iron
  complexes such as ferritin and hemosiderin
• Circulating iron is loosely bound to the
  transport protein transferrin

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Fate and Destruction of Erythrocytes

• The life span of an erythrocyte is 100120 days
• Old erythrocytes become rigid and fragile, and
  their hemoglobin begins to degenerate
• Dying erythrocytes are engulfed by macrophages
• Heme and globin are separated and the iron is
  salvaged for reuse

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Fate and Destruction of Erythrocytes

• Heme is degraded to a yellow pigment called
  bilirubin
• The liver secretes bilirubin into the intestines
  as bile
• The intestines metabolize it into urobilinogen
• This degraded pigment leaves the body in feces,
  in a pigment called stercobilin
• Globin is metabolized into amino acids and is
  released into the circulation
• Hb released into the blood is captured by
  haptoglobin and phgocytized

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Life Cycle of Red Blood Cells
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Erythrocyte Disorders

• Anemia blood has abnormally low oxygen-carrying
  capacity
• It is a symptom rather than a disease itself
• Blood oxygen levels cannot support normal
  metabolism
• Signs/symptoms include fatigue, paleness,
  shortness of breath, and chills

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Anemia Insufficient Erythrocytes

• Hemorrhagic anemia result of acute or chronic
  loss of blood
• Hemolytic anemia prematurely ruptured
  erythrocytes
• Aplastic anemia destruction or inhibition of
  red bone marrow

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Anemia Decreased Hemoglobin Content

• Iron-deficiency anemia results from
• A secondary result of hemorrhagic anemia
• Inadequate intake of iron-containing foods
• Impaired iron absorption
• Pernicious anemia results from
• Deficiency of vitamin B12
• Lack of intrinsic factor needed for absorption of
  B12
• Treatment is intramuscular injection of B12
  application of Nascobal

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Anemia Abnormal Hemoglobin

• Thalassemias absent or faulty globin chain in
  hemoglobin
• Erythrocytes are thin, delicate, and deficient in
  hemoglobin
• Sickle-cell anemia results from a defective
  gene coding for an abnormal hemoglobin called
  hemoglobin S (HbS)
• HbS has a single amino acid substitution in the
  beta chain
• This defect causes RBCs to become sickle-shaped
  in low oxygen situations

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Leukocytes (WBCs)

• Leukocytes, the only blood components that are
  complete cells
• Are less numerous than RBCs
• Make up 1 of the total blood volume
• Can leave capillaries via diapedesis
• Move through tissue spaces
• Leukocytosis WBC count over 11,000 per cubic
  millimeter
• Normal response to bacterial or viral invasion

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Granulocytes

• Granulocytes neutrophils, eosinophils, and
  basophils
• Contain cytoplasmic granules that stain
  specifically (acidic, basic, or both) with
  Wrights stain
• Are larger and usually shorter-lived than RBCs
• Have lobed nuclei
• Are all phagocytic cells

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Neutrophils

• Neutrophils have two types of granules that
• Take up both acidic and basic dyes
• Give the cytoplasm a lilac color
• Contain peroxidases, hydrolytic enzymes, and
  defensins (antibiotic-like proteins)
• Neutrophils are our bodys bacteria slayers

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Eosinophils

• Eosinophils account for 14 of WBCs
• Have red-staining, bilobed nuclei connected via a
  broad band of nuclear material
• Have red to crimson (acidophilic) large, coarse,
  lysosome-like granules
• Lead the bodys counterattack against parasitic
  worms
• Lessen the severity of allergies by phagocytizing
  immune complexes

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Basophils

• Account for 0.5 of WBCs and
• Have U- or S-shaped nuclei with two or three
  conspicuous constrictions
• Are functionally similar to mast cells
• Have large, purplish-black (basophilic) granules
  that contain histamine
• Histamine inflammatory chemical that acts as a
  vasodilator and attracts other WBCs
  (antihistamines counter this effect)

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Agranulocytes

• Agranulocytes lymphocytes and monocytes
• Lack visible cytoplasmic granules
• Are similar structurally, but are functionally
  distinct and unrelated cell types
• Have spherical (lymphocytes) or kidney-shaped
  (monocytes) nuclei

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Lymphocytes

• Account for 25 or more of WBCs and
• Have large, dark-purple, circular nuclei with a
  thin rim of blue cytoplasm
• Are found mostly enmeshed in lymphoid tissue
  (some circulate in the blood)
• There are two types of lymphocytes T cells and B
  cells
• T cells function in the immune response
• B cells give rise to plasma cells, which produce
  antibodies

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Monocytes

• Monocytes account for 48 of leukocytes
• They are the largest leukocytes
• They have abundant pale-blue cytoplasms
• They have purple-staining, U- or kidney-shaped
  nuclei
• They leave the circulation, enter tissue, and
  differentiate into macrophages

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Monocytes

• Macrophages
• Are highly mobile and actively phagocytic
• Activate lymphocytes to mount an immune response

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Formation of Leukocytes
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Leukocytes Disorders Leukemias

• Leukemia refers to cancerous conditions involving
  white blood cells
• Leukemias are named according to the abnormal
  white blood cells involved
• Myelocytic leukemia involves myeloblasts
• Lymphocytic leukemia involves lymphocytes
• Acute leukemia involves blast-type cells and
  primarily affects children
• Chronic leukemia is more prevalent in older
  people

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Leukemia

• Immature white blood cells are found in the
  bloodstream in all leukemias
• Bone marrow becomes totally occupied with
  cancerous leukocytes
• The white blood cells produced, though numerous,
  are not functional
• Death is caused by internal hemorrhage and
  overwhelming infections
• Treatments include irradiation, antileukemic
  drugs, and bone marrow transplants

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Platelets

• Platelets are fragments of megakaryocytes with a
  blue-staining outer region and a purple granular
  center
• Their granules contain serotonin, Ca2, enzymes,
  ADP, and platelet-derived growth factor (PDGF)
• Platelets function in the clotting mechanism by
  forming a temporary plug that helps seal breaks
  in blood vessels
• Platelets not involved in clotting are kept
  inactive by NO and prostaglandin I2

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Detailed Events of Coagulation
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• HemoglobinIs the protein attahced to the red
  blood cell that carries oxygen around the blood
  stream. It gets its help from an iron molecule.
• Antigens- Substances that stimulate an immune
  response. They recognize foreign objects.

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ABO Blood Groups

• Type A (antigen A- antibody B)
• Type B(antigen B- antibody A)
• Type AB(antigens A and B, anibodies A and B)
• Type O (No antigens or antibodies A and B)
• rH factor (antigen rH-Either you have it
  (positive) or you dont (negative).

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ABO Blood Groups

• The ABO blood groups consists of
• Two antigens (A and B) on the surface of the RBCs
  
• Two antibodies in the plasma (anti-A and anti-B)
• An individual with ABO blood may have various
  types of antigens and spontaneously preformed
  antibodies
• Agglutinogens and their corresponding antibodies
  cannot be mixed without serious hemolytic
  reactions

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ABO Blood Groups
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Rh Blood Groups

• There are eight different Rh agglutinogens, three
  of which (C, D, and E) are common
• Presence of the Rh agglutinogens on RBCs is
  indicated as Rh
• Anti-Rh antibodies are not spontaneously formed
  in Rh individuals
• However, if an Rh individual receives Rh blood,
  anti-Rh antibodies form
• A second exposure to Rh blood will result in a
  typical transfusion reaction

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Blood Typing

• When serum containing anti-A or anti-B
  agglutinins is added to blood, agglutination will
  occur between the agglutinin and the
  corresponding agglutinogens
• Positive reactions indicate agglutination

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Prevention of Undesirable Clots

• Substances used to prevent undesirable clots
  include
• Aspirin an antiprostaglandin that inhibits
  thromboxane A2
• Heparin an anticoagulant used clinically for
  pre- and postoperative cardiac care
• Warfarin used for those prone to atrial
  fibrillation

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Hemostasis Disorders Bleeding Disorders

• Thrombocytopenia condition where the number of
  circulating platelets is deficient
• Patients show petechiae (small purple blotches on
  the skin) due to spontaneous, widespread
  hemorrhage
• Caused by suppression or destruction of bone
  marrow (e.g., malignancy, radiation)
• Platelet counts less than 50,000/mm3 is
  diagnostic for this condition
• Treated with whole blood transfusions

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Hemostasis Disorders Bleeding Disorders

• Hemophilias hereditary bleeding disorders
  caused by lack of clotting factors
• Hemophilia A most common type (83 of all
  cases) due to a deficiency of factor VIII
• Hemophilia B results from a deficiency of
  factor IX
• Hemophilia C mild type, caused by a deficiency
  of factor XI

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Hemostasis Disorders

• Disseminated Intravascular Coagulation (DIC)
  widespread clotting in intact blood vessels
• Residual blood cannot clot
• Blockage of blood flow and severe bleeding
  follows
• Most common as
• A complication of pregnancy
• A result of septicemia or incompatible blood
  transfusions

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RBC formation animation
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The Lymphatic System
White Blood Cells
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Intracellular fluids and proteins are returned
to the blood by the lymphatic system
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Blood clotting animation
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Fun Facts
Just Fun! You Don't Have to Memorize These!

• There are almost 60,000 miles of blood vessels
  in the human body.
• Red blood cells are formed at the rate of 2
  million per second.
• Within a tiny droplet of blood, there are 5
  million red blood cells, 300,000 platelets and
  10,000 white cells.
• It takes about 1 minute for a red blood cell
  to circle the whole body.