Biology 277: Cardiovascular System, Lymphatic System

Chapter 18: Blood

Fluid connective tissue

• Transported by the cardiovascular system
  • Arteries
  • Veins
  • Capillaries
• Formed element in plasma matrix
  • Erythrocytes
  • Leukocytes
  • Platelets

Functions of blood

• Transportation
  • Respiratory gasses
  • Formed elements
  • Hormones
  • Nutrients
  • Waste
• Regulation of body conditions
  • Body temperature
    • Absorb heat and release heart at the skin
  • Body pH
    • Can absorb acids and bases
    • Has buffers to maintain normal pH range
  • Fluid balance
    • Add water through GI tract
    • Lose water in skin, urinary tract, respiration
    • Exchange between blood and interstitial fluid
• Protection
  • Leukocytes
  • Plasma proteins
  • Platelets

Characteristics of blood

• Color
  • Degree of oxygenation
    • High oxygen: bright red
    • Low oxygen: deep red
• Volume
  • About 5L
• Viscosity
  • 4-5 times more viscous than water
  • Depends on the dissolved and suspended substances
  • High erythrocytes = high viscosity
  • Low fluid levels = high viscosity
• Plasma concentration
  • Concentration of solutes
  • Direction of osmosis in capillary wall
• Temperature
  • 1 degree (celcius) higher than body temperature
• pH
  • Between 7.35-7.45
  • Slightly alkaline
  • If altered plasma protein becomes denatured

Components of blood

• Plasma - 55%
• Formed elements
  • Buffy coat - 1%
    • Leukocytes
    • Platelets
  • Erythrocytes - 44%
• Hematocrit - percentage of erythrocytes
  • Adult males 42-56%
    • Higher due to testosterone, stimulate kidney to produce EPO to increase RBC production
  • Adult females 38-46%
  • High levels
    • Dehydration
    • In athletes, due to blood doping
  • Low levels
    • Anemia
    • Hemorrhage

Plasma components

• Water (92%)
• Plasma proteins (7%)
  • Exert colloid osmotic pressure
  • Albumin
  • Globulins
  • Fibrinogen
  • Regulatory proteins
• Dissolved molecules and ions, nutrients, hormones, vitamins, enzymes, and waste products (1%)

Plasma proteins

• Albumins
  • Most abundant (58%)
  • Greatest colloid osmotic pressure
  • Produced in liver
  • Control osmotic pressure with Na+
  • Transports hormones, ions, and some lipids
• Globulins
  • 37%
  • Alpha and beta
    • Transport some water insoluble molecules, hormones, and metals and ions
  • Gamma
    • Antibodies
• Fibrinogen
  • 4%
  • Produced by liver
  • Crucial in blood clotting
  • Soluble form of fibrin
• Regulatory proteins
  • <1%
  • Hormones and enzymes

Other solutes in blood

• Electrolytes
  • Cl- and Na+ or K+
• Nutrients
  • Glucose, amino acids, lactic acid, lipids (CHO, HDL, LDL, triglycerides, phospholipids
• Respiratory gasses
  • Oxygen and carbon dioxide
• Wastes
  • Urea, creatinine, bilirubin, ammonia

Hematopoiesis - occur in red bone marrow

• Hemocytoblast - multipotent stem cell
  • Myeloid line
    • Erythropoiesis
      • Erythrocytes

1. The myeloid stem cell under the influence of multi-CSF forms a progenitor cell. EPO hormone will increase rate of production
2. Progenitor cell forms a proerythroblast (large and nucleated)
3. Proerythroblast becomes an erythroblast which has ribosomes that produce the hemoglobin protein
4. A large erythroblast will form a normoblast - a small cell with more hemoglobin and an ejected nucleus
5. Formation of a reticulocyte - only ribosomes to synthesize hemoglobin
6. Reticulocyte matures into an erythrocyte - which only contains hemoglobin as ribosomes have degenerated
   • • Leukopoiesis
       • Leukocytes
7. Myeloid stem cell is stimulated by multi-CSF and GM-CSF to form a progenitor cell
8. Granulocyte line develops when the progenitor cell forms a myeloblast under the influence of G-CSF.
   1. This will differentiate into granulocytes (eosinophil, basophil, neutrophil)
9. Monocyte line develops when the progenitor cell forms a myeloblast under the influence of M-CSF
   1. This will differentiate into a monocyte
   • Lymphoid line
     • Leukopoiesis
       • Lymphocytes
       • Natural killer T cell
10. Lymphoid stem cell will differentiate into either a B-lymphoblast or T-lymphoblast
    1. B-lymphoblast will mature into a B-lymphocyte
    2. T-lymphoblast will mature into a T-lymphocyte
11. Some will differentiate into a natural killer cell directly

• Hemocytoblast
  • Myeloid line
    • Thrombopoiesis
      • Megakaryocyte
      • Platelets

1. From the myeloid stem cell, a committed cell called a megakaryoblast is produced
2. It matures under the influence of thrombopoietin to form a megakaryocyte
3. Megakaryocytes produce platelets by forming long extensions from themselves called proplatelets
   1. These proplatelets extend through the blood vessel wall in the red bone marrow
   2. The force from the blood flow “slices” these proplatelets into the fragments we know as platelets
4. Megakaryocytes remain within the red bone marrow, whereas the cellular fragments that become platelets enter the blood

Erythrocytes

• Small, flexible formed element
• Biconcave disc
  • Surface area
  • Allows stacking
• Transports
  • Oxygen and carbon dioxide

Hemoglobin

• Four protein molecules called globins
  • 2 alpha
  • 2 beta
• All contain heme group - each alpha/beta chain has this
  • Porphyrin ring
  • Iron ion - in the center of porphyrin ring
    • Where oxygen forms a weak bond for easy attachment/detachment
  • Globin molecule
    • Where carbon dioxide forms a weak bond for easy attachment/detachment

EPO Regulation of Erythrocyte Production

• Produced in kidneys
• Secretion release stimulated by decrease in blood oxygen levels
• Causes: removal of aged RBC, blood loss

Negative Feedback:

1. Chemoreceptors in kidney detect low blood oxygen levels
2. EPO released
3. EPO travels to red bone marrow
4. Erythrocytes are stimulated from myeloid stem cells
5. Blood oxygen levels go up
6. Increased blood oxygen levels inhibit EPO release

Higher rate in males due to testosterone

Recycling and Elimination of Erythrocytes

• Aged erythrocytes - 120 day lifespan
  • Cannot repair - no organelles
  • Phagocytized by macrophages - in the liver and spleen
  • Hemoglobin components separated
    • Globin proteins
      • Get broken down into amino acids that enter blood to synthesize protein
    • Iron ion
      • Transferrin
        • Transports iron ion to liver and spleen (storage)
    • Heme group - converted within macrophages to (below)
      • Biliverdin - green pigment
        • Bilirubin - yellow pigment
        • Transported by albumin to the liver
        • Released as a component of bile to the small intestine converted to urobilinogen

Urobilinogen

1. Small intestine to large intestine
   1. Converted by bacteria to stercobilin (brown pigment)
   2. Expelled in feces
2. Absorbed back into the blood
   1. Converted to urobilin (yellow pigment)
   2. Excreted by urine

Erythrocyte disorders

• Anemia
  • Aplastic
    • Decrease in formation of erythrocytes and hemoglobin due to defective bone marrow
    • Bone marrow cannot produce erythrocytes
  • Congenital hemolytic
    • Genetic defect
    • Abnormal membrane proteins cause a fragile plasma membrane
    • Causes destruction of erythrocytes
  • Erythroblastic
    • Heredity
    • Large number of immature nucleated cells
    • Causes abnormal acceleration
  • Hemorrhagic
    • Blood loss
    • Chronic ulcers
    • Heavy menstrual flow
  • Pernicious
    • Failure to absorb vitamin B12
    • Lack an intrinsic factor
  • Sickle cell anemia
    • Genetic defect
    • Autosomal recessive anemia
    • Red blood cell is sickle shaped with lower oxygen levels
    • Cannot flow seamlessly to vessels

ABO Blood Group

• Erythrocytes
  • Surface Antigen
    • ABO
    • Rh
  • Antibody
    • Anti-A antibody
    • Anti-B antibody

Rh factor

• Surface Antigen D - positive or negative

Rh Incompatibility

• Rh negative mother
  • Rh positive fetus
• 1st Pregnancy:
  • Antigen D introduced to mother’s blood
• Between pregnancies:
  • Anti-D antibodies produced in the mother
• 2nd Pregnancy:
  • Anti-D antibodies attack Rh+ fetal erythrocytes
• Treatment:
  • Immunoglobulins
  • Bind to antigens so mom doesn’t make antibodies

Clinical considerations about blood types

• Agglutination reaction
  • Clumped cells block blood vessels
  • Cause hemolysis
    • Lead to organ damage

Leukocyte Characteristics

• Defend against pathogens
• Motile and flexible
  • Diapedesis - leukocytes squeezed thru endothelial cells of blood vessel wall
  • Chemotaxis - release of chemicals to attract leukocytes
• Two classes
  • Granulocytes - basophil, eosinophil, neutrophils
  • Agranulocytes - lymphocytes and monocyte

Granulocytes

• Neutrophil
  • Most numerous (50-70%)
  • Light purple granules
  • Multilobed
  • Phagocytose pathogens during bacterial infections
• Eosinophil
  • 1-4%
  • Bilobed nucleus
  • Reddish granules
  • Go after antibody-antigen complexes and allergens
  • Attack parasitic worms via apoptosis
• Basophil
  • 0.5-1%
  • Bilobed nucleus
  • Dark purple granules
  • Histamine (vasodilator), heparin (anti-coagulant)

Agranulocytes

• Monocytes
  • 2-8%
  • C-shaped nucleus
  • Exit blood to reside in tissues
  • Transform into macrophages that phagocytize bacteria, dead cells, viruses, cell fragments, etc.
• Lymphocytes
  • 20-40%
  • Dark stained nucleus
• T-Lymphocytes
  • Manage and direct immune response
  • Go after foreign cells
• B-Lymphocytes
  • Become plasma cells
  • Produce antibodies
• Natural Killer
  • Apoptosis inducing cells against abnormal cells or infected tissues

Platelets (Thrombocytes)

• Irregular shape
• From megakaryocytes
• Role in homeostasis

Hemostasis

1. Vascular spasm - blood vessel constricts to limit blood loss
   1. Limits blood leakage
   2. Platelets and endothelial cells release chemicals for further constriction
2. Platelet plug formation - platelets arrive at site of injury and adhere to exposed collagen fibers
   1. Platelets change and adhere
      1. Von Willebrand factor - platelets swell and become sticky - adhere to collagen fibers - mitosis stimulating substances releases - repair of blood vessel wall.
   2. Release chemicals - prolong vascular spasm and attract more platelets
      1. Serotonin
      2. Thromboxane A2
      3. ADP
      4. Procoagulants
   3. Thrombocytopenia
      1. Low platelet count
3. Coagulation phase - coagulation cascade converts inactive proteins to active forms, which ultimately form fibrin strands of a blood clot
   1. Network of fibrin (from fibrinogen) forms mesh (fibrin network, trapped RBC, platelets, WBC, plasma proteins)
   2. Clotting requires
      1. Calcium
      2. Clotting factors
      3. Platelets
      4. Vitamin K - synthesis of clotting factors 2, 7, 9, 10
   3. Clotting begins with two pathways
      1. Intrinsic pathway (inside) - platelets adhere to vessel wall - various factors releases - factor IX binds with Ca2+ and platelet factor III - complex - active factor VIII - activate factor X
      2. Extrinsic pathway (outside) - release of tissue thromboplastin - combines with factor VII and Ca2+ - complex activates factor X
   4. Both pathways converge to one common

• Factor X - prothrombin activator - prothrombin - thrombin (enzyme) - thrombin - fibrinogen - fibrin threads (mesh)

Elimination of the clot

• Clot reaction
  • Actinomyosin contracts - squeeze serum out of clot - vasoconstriction
• Fibrinolysis
  • Plasmin - enzyme that digest fibrin

Bleeding Disorders

• Hemophilia
  • Hemophilia A - lack factor 8
  • Hemophilia B - lack factor 9
  • Hemophilia C - lack factor 11
• Vitamin K deficiency
• Thrombocytopenia - low platelet count

Blood clotting disorders

• Hypercoagulation - tendency to clot
  • Thrombus - clot
  • Embolus - clot is dislodged

Chapter 19: Heart

Cardiovascular System

• Function
  • Transport blood, nutrients, and carbon dioxide
  • Maintain adequate perfusion - sufficient delivery of nutrients to cells

Components of Cardiovascular System

• Blood vessels
  • Arteries - away
  • Capillaries - exchange
  • Veins - towards
• Heart - 4 chambers, 2 pumps

Anatomic Features of the Heart

• 2 sides
  • Right side
    • Right atrium - receive deoxygenated blood from the body
    • Right ventricle - pumps deoxygenated blood to lungs
  • Left side
    • Left atrium - receives oxygenated blood from lungs
    • Left ventricle - pumps oxygenated blood to body
• Great vessels
  • Right side
    • SVC and IVC - drain deoxygenated blood into right atrium
    • Pulmonary trunk - receive deoxygenated blood pumped from right ventricle
  • Left side
    • Pulmonary veins - drain oxygenated blood into left atrium
    • Aorta - receives oxygenated blood pumped from left ventricle
• Valves
  • Right side
    • Right AV valve - between right atrium and right ventricle
    • Pulmonary semilunar valve - between right ventricle and pulmonary trunk
  • Left side
    • Left AV valve - between left atrium and left ventricle
    • Aortic semilunar valve - between left ventricle and aorta
  • AV valves close when ventricles contract
  • Semilunar valves open when ventricles contract

Circulation Routes

• Pulmonary Circulation
  • Deoxygenated blood enters the right atrium from the IVC and SVC and coronary sinus
  • Blood passes through the right AV valve
  • Blood enters right ventricle
  • Blood passes through the pulmonary semilunar valve
  • Blood enters pulmonary trunk
  • Blood continues through the right and left pulmonary arteries to both lungs
  • Blood enters pulmonary capillaries of both lungs for gas exchange
  • Oxygenated blood exits the pulmonary capillaries of the lungs and returns to the heart by right and left pulmonary veins
  • Blood enters the left atrium of the heart
• Systemic circulation
  • Oxygenated blood enters the left atrium
  • Blood passes through the left AV valve
  • Blood enters the left ventricle
  • Blood passes through the aortic semilunar valve
  • Blood enters the aorta
  • Blood is distributed by the systemic arteries
  • Blood enters systemic capillaries for exchange
  • Deoxygenated blood exits systemic capillaries and returns to the heart by systemic veins
  • Drain into IVC, SVC, coronary sinus
  • Blood enters right atrium

*Coronary Circulation*

• Coronary Arteries
  • Right coronary artery
    • Right marginal artery - feed lateral wall of right ventricle
    • Posterior interventricular artery - feed posterior wall of both ventricles
  • Left coronary artery
    • Circumflex artery - feed lateral wall of left ventricle
    • Anterior interventricular artery - feed anterior wall of left ventricle and interventricular septum
• Coronary veins
  • Transport deoxygenated blood from heart wall to heart (drain to coronary sinus)
    • Great cardiac, middle cardiac, small cardiac

Microscopic Anatomy of Cardiac Muscle (myocardium)

• Sarcolemma
• T-tubules
• Sarcoplasmic reticulum
  • Surrounds bundles of myofilaments - arranged in sarcomeres
• Intercalated discs - cells connect by this
  • Desmosomes - mechanical connection of cells
  • Gap junctions - ion flow

Metabolism of Cardiac Muscle

• Extensive blood supply
• Numerous mitochondria
• Myoglobin - bind oxygen at muscle rest
• Creatine kinase - catalyze creatine phosphate
• Able to use different fuel molecules
• Relies on aerobic cellular respiration
  • Rely on oxygen, susceptible to failure in low oxygen conditions - lead to cell death (myocardial infarction)

Heart Conduction System - ANS influence

• Sinoatrial node
  • Initiate heartbeat
• Atrioventricular node
  • Located in floor of right atrium
• Atrioventricular bundle
  • Extends from AV node
  • Divides into left and right bundles
• Purkinje fibers
  • Extends from left and right bundles at apex

Innervation of Heart

• Cardiac center (medulla oblongata)- rate/strength of contractions
  • Signaled by chemoreceptors and baroreceptors
• PNS - decrease HR
  • Cardioinhibitory center
  • Vagus nerve
    • Right vagus innervates SA node
    • Left vagus innervates AV node
• SNS - increase HR
  • Cardioacceleratory center
  • Cardiac nerves through T1-T5 segments of spinal cord
    • Extend to SA node, AV node, myocardium, and coronary arteries
    • Promote vasodilation - blood flow to myocardium

Heart Contraction

• Conduction system
  • Initiation - SA node initiates an action potential
  • Spread of action potential - throughout atria and conduction system
• Cardiac muscle cells
  • RMP: -90mV
  • Action potential propagated along sarcolemma of cardiac muscle cells
  • Muscle contraction - thin filaments slide past thick filaments and sarcomeres shorten within cardiac muscle cells
• SA nodal cells
  • Pacemaker cells - initiate a heartbeat via depolarization
  • Generate AP
  • RMP = -60mV

Electrical Events at SA node - spontaneous depolarization

• Initiation of action potential
• RMP: -60mV
• Reaching threshold - allow influx of Na+ (-60mV to -40mV)
• Depolarization - fast voltage gated Ca2+ channels open (-40mV to 0mV)
• Repolarization - voltage gated K+ channels open (0mV to -60mV)
• @ rest: SA node starts an action potential after 0.8 secs after the last one
  • Resting rate: 70 bpm
  • Fire faster but don’t due to vagal tone (by PNS)

Spread of action potential

• Generated at SA node - spread to gap junctions throughout atria to AV node - action potential delayed at AV node - AV bundle conducts the action potential along the left and right bundle branches to purkinje fibers - action potential is spread via gap junctions throughout ventricles

Electrical Events of Cardiac Muscle Cells

• Action potential opens fast voltage gated Na+ channels - depolarization (-90mV to 30mV) - channels close - plateau (K+ in, Ca2+ out) - repolarization (K+ out, 30mV to -90mV) - RMP

Mechanical Events of Cardiac Muscle Cells

• Ca2+ from SR and interstitial fluid used for crossbridge cycling - Ca2+ binds to troponin - crossbridge, powerstroke, release of myosin head, reset of myosin head

Refractory Period

• Longer in cardiac muscle - cannot exhibit tetany - can’t fire another action potential during refractory period (plateau)

ECG

• Waves
  • P wave - atrial depolarization
  • QRS complex - ventricular depolarization
  • T wave - ventricular repolarization
• Segments
  • PQ segment - atrial plateau
  • ST segment - ventricular plateau
• Intervals
  • P-R interval - time needed to transmit action potential to entire conduction system
  • Q-T interval - time required for AP to occur in ventricles

Cardiac Cycle

• Atrial relaxation/ventricular filling
  • Chambers relaxed - blood return to atrium - passive filling of ventricles - arterial BP>>ventricular BP - semilunar valves close - AV valves open
• Atrial contraction/ventricular filling
  • SA nodes are stimulated - push remaining blood into ventricles - filled to EDV (vol. Of blood within ventricle @ end of diastole, 130mL)
• Isovolumic contraction
  • Purkinje fibers start ventricular contraction - ventricular pressure rises - AV valves close
• Ventricular ejection
  • Semilunar valves open - SV (amount of blood ejected by each ventricle 70mL) - ESV (remaining blood in ventricle after contraction, EDV-SV)
• Isovolumic relaxation
  • Ventricles relax - arterial pressure>>ventricular pressure - semilunar valves close

Cardiac output

• Amount of blood pumped by a single ventricle in one minute (L/min)
• Determined by heart rate and stroke volume
  • HR x SV = CO (75 bpm x 70mL/beat = 5.25L/min)
• Function of HR and SV - maintain resting CO
  • Increased by exercise
  • Small heart = small SV - higher bpm
  • Big heart = large SV - low bpm

Cardiac reserve

• Level of exercise a person can endure
• Increase in cardiac output above its resting level
• Subtract CO at rest from CO during exercise

Variables that Influence HR

• Positive chronotropic agents - increase HR
  • SNS - release NE (hormone and NT) - act on SA nodal cells - adrenal medulla release its hormones -
  • TH - increase number of beta-1 receptors (for NE/EPI)
  • Nicotine - increase release of NE - beta-1 receptors
  • Caffeine - inhibit breakdown of cAMP
  • Cocaine - inhibit reuptake of NE
• Negative chronotropic agents - decrease HR
  • PNS - Ach release on nodal cells - bind to muscarinic receptors - hyperpolarization - slow HR
  • Beta blockers - interfere with binding of EPI and NE on to beta-1 receptors - slow HR
• Autonomic reflexes
  • Atrial reflex - prevent heart from overfilling
    • Stimulated by increased venous return - cardiac center - cardioacceleratory center - SNS - increase HR - lessen stretch on atrial walls

Variables that Influence Stroke Volume

• Venous return - blood returned to heart per unit time
  • Frank-Starling Law - the more blood put in, the more it will stretch - great overlapping of filaments - greater crossbridge formation - increased SV
  • Increase
    • Increase venous pressure (exercise)
    • Increased time (to fill ventricles)
  • Decrease
    • Low blood volume (hemorrhage)
    • High heart rate - small EDV - small preload - small SV
• Inotropic agents - substances that act on the myocardium to alter contractility
  • Positive - increase available Ca2+/cross bridges
    • SNS - NE/EPI - beta-1 receptors - increase Ca2+
    • TH - increase beta-1 receptor in cardiac muscle cells
    • Drugs - digitalis - boost CO by increasing contractility
  • Negative - decrease available Ca2+/cross bridges
    • Electrolyte imbalance
    • Drugs
• Afterload - resistance in arteries to ejection of blood
  • Atherosclerosis - narrow lumen - increase peripheral resistance - decrease SV

Variables Affecting Cardiac Output

• Chronotropic agents, venous return, inotropic agents, after load
• Increase SV and HR = increase CO
• Decrease SV and HR = decrease CO

Chapter 20: Vessels/Circulation

Anatomy and Physiology of Blood Vessels

• 3 Types
  • Artery, capillary, vein
• 3 layers
  • Tunica intima, tunica media, tunica externa

Comparison of Different Vessel Types

• Arteries
  • Elastic - conducting from the heart to muscular arteries
  • Muscular - distributing blood to the organ
  • Arterioles - undergo vasomotor tone
• Capillaries
  • Continuous - skin, lungs, CNS, muscles
  • Fenestrated - pores - SI, kidneys, choroid plexus
  • Sinusoid - liver, spleen, red bone marrow, endocrine glands
  • Diffusion of solutes
  • Vesicular transport - pinocytosis, exocytosis
  • Bulk flow - movement of large amounts of fluid and dissolved substances, down a pressure gradient
    • Filtration - fluid moves out of the blood - on arterial end
    • Absorption - fluid moves into the blood - on venule end
  • Blood hydrostatic pressure - force exerted per unit of area by the blood on vessel wall - arterial end, greater than blood colloid osmotic pressure
  • Blood colloid osmotic pressure - promote reabsorption (in) - oppose hydrostatic pressure - greater in venous end to promote reabsorption
• Veins
  • Venules
  • Small-medium - valves
  • Large - valves
  • Systemic veins - blood reservoirs that can move out of circulation during activity

Pathways of Blood Vessels

• Simple Pathways - 1 major artery delivers blood to organ or region
• Alternative Pathways
  • Anastomosis - joining of blood vessels
    • Arterial (2 or more aa. join), venous (2 or more vv. drain), arteriovenous (shunt)
  • Portal system - 2 capillary beds in sequence
    • Arteriole - capillary bed - portal vein - capillary bed - vein

Factors of local blood flow

• Degree of vascularization
  • Angiogenesis - blood vessels create new ones in the tissue - exercise, weight gain
  • Regression - return to the previous state before angiogenesis
• Myogenic response - constant blood flow
  • BP rises - more blood in the arteriole - stretches - smooth muscle of arterial wall will constrict vessel
  • BP lowers - less blood in arteriole - less stretch - smooth muscle of arterial wall relaxes vessels
• Local regulatory factors
  • Vasodilators - dilate arterioles, relax precapillary sphincters - increase blood flow in capillary bed
  • Vasoconstrictors - constrict arterioles - contraction of precapillary sphincters - decrease blood flow in capillary bed
  • Autoregulation - inadequate perfusion - vasodilators activated - increase blood flow in capillary bed - adequate perfusion
  • Short-term regulation (immunity) - endothelial cells release nitric oxide (vasodilator) and thromboxane (vasoconstrictor)
• Total blood flow
  • May increase with exercise
  • Depends on both heart and vessels

Blood Pressure: force per unit area that blood exerts against the inside wall of a vessel

Blood pressure gradient: change in pressure from one end of the vessel to the other - propel blood through the vessels - high in arteries - low in veins

Arterial blood pressure: blood flow in arteries that pulses cardiac cycle

• Systolic - max stretch of artery
• Diastolic - recoil of artery
• Pulse - systolic/diastolic - additional pressure placed on arteries by heart contraction

Venous Blood Pressure:

• Venous return - depend on BP gradient
  • Skeletal muscle pump - moves blood during physical activity
  • Respiratory pump - venous return in thorax

Peripheral Resistance: amount of friction blood experiences traveling through blood vessels

• Viscosity - resistance of fluid to its flow - less = less resistance; more = more resistance
• Vessel length - the longer the vessel, the greater the resistance
• Vessel radius - smaller radius = more resistance; bigger radius = less resistance

Regulation of Blood Pressure and Flow (ANS)

• BP decrease
  • Baroreceptors sense decreased stretch - decrease firing rate sent to cardiac and vasomotor centers – cardioacceleratory center increases nerve signals; cardioinhibitory center decreases nerve signals - vasomotor center increases nerve signals - vasoconstriction - increase peripheral resistance
• BP increase
  • Baroreceptors sense increased stretch - increase firing rate to cardiac and vasomotor centers - cardioacceleratory center decreases nerve signals; cardioinhibitory center increases nerve signals - vasomotor center decreases nerve signals - vasodilation - decrease peripheral resistance

Chemoreceptor Reflexes

• Aortic (vagus) and carotid (glossopharyngeal) bodies - send signals to cardiovascular center
• Stimulated by high CO2, low pH, very low 02 - increases firing rate to cardiovascular center
• Vasomotor center - increases SNS to veins and increases venous return - increase blood flow including to lungs

Higher Brain Centers

• Hypothalamus - increase CO and resistance
  • Temp increase - high BP
  • Fight or flight - high BP
• Limbic system - alter BP in response to emotional memories

Renin-Angiotensin System

• Kidney detects low BP or stimulated by SNS, renin enzyme released - renin converts angiotensinogen to angiotensin I - ACE converts angiotensin I into angiotensin II - angiotensin II increases BP by - vasoconstriction, stimulate thirst center, decreased urine formation - releases ADH and aldosterone
• Aldosterone: triggered by angiotensin II - increased H20 and Na+ in kidneys - decrease urine output
• ADH: triggered by angiotensin II - increases H20 absorption - maintain blood volume - stimulate thirst centers
• ANP: released due to increased stretch of heart atria - stimulates vasodilation - decrease resistance - increase urine output to lower blood volume

Blood Flow Distribution During Exercise

• Increase - stronger, faster heartbeat - skeletal muscles help remove blood from reservoirs
• Redistribution - according to needs of tissues

Pulmonary Circulation

• Pulmonary arteries
  • Less elastic CT
  • Wider lumens
• Pulmonary vessels
  • Shorter than systemic BP
  • Lower BP

Hepatic Portal System

• Blood from digestive organs sent to liver - blood returned to heart
• Hepatic portal vein drains from - splenic vein - inferior mesenteric vein - superior mesenteric vein

Fetal Circulation

• Fetal lungs - non functional
• Fetal vessels - shunt blood to organs in need
• Route
• Oxygenated blood from placenta enters fetus through umbilical veins (round ligament of liver)
• Blood sent to IVC via ductus venosus (ligamentum venosum)
• Mixing of oxygenated blood and deoxygenated blood
• Blood from IVC and SVC empty in right atrium
• Blood shunted to L atrium via foramen ovale (fossa ovalis)
• Small amount enters right ventricle, pumped to pulmonary trunk
• Shunted to aorta through ductus arteriosus (ligamentum arteriosum)
• Blood travels to body and returns to placenta through umbilical arteries (medial umbilical ligaments)

Chapter 21: Lymphatic System

Functions

• Transport and house lymphocytes and other immune cells
• Return excess interstitial fluid to the blood

Components:

• Lymph vessels
• Lymphoid tissues
• Lymphoid organs
• Lymph (fluid) - water, dissolved solutes, protein, foreign material, cancer cells

Lymph capillaries

• Close-ended
• Occur everywhere except red bone marrow and avascular tissues
• Resemble blood capillaries
• Lacteals - SI

Movement of lymph into lymph capillaries

• Hydrostatic pressure - push lymph fluid into openings
• Anchoring filaments - prevent from collapsing

Lymphatic vessels

• Capillaries merge to form
• Adjacent to arteries and veins
• Resemble veins
• Rely on respiratory/skeletal muscle pumps, pulsatile movement of blood and nearby arteries, rhythmic contraction of smooth muscle

Lymphatic Trunks

• Jugular trunks - drain from head and neck
• Subclavian trunks - drain upper limbs, breast, superficial thoracic walls
• Bronchomediastinal trunks - drain deep thoracic structures
• Intestinal trunks - drain most of abdominal structures
• Lumbar trunks - drain lower limbs, abdominal and pelvic walls, pelvic organs

Lymphatic Ducts

• Right lymphatic duct
  • Drains upper right quadrant of body
  • Delivers to junction of right subclavian and right internal jugular vein
• Thoracic duct
  • Drains from left side of head and neck, left upper limb, left side of thorax, abdomen , and both lower limbs
  • Delivers to junction of left subclavian and left jugular veins
• Cisterna chyli
  • Receive lipid rich chyle from GI tract
  • Both lumbar and intestinal trunks drain into this

Lymphoid Tissues and Organs

• Primary lymphoid structures
  • Formation and maturation of lymphocytes
  • Red bone marrow (hematopoiesis) , thymus
• Red Bone Marrow:
  • Hematopoiesis
  • B-cells:mature in bone marrow
  • T-cells: migrate to thymus and matures in thymus
• Thymus:
  • T-lymphocyte maturation and differentiation
  • Inner medulla - mature T cells
  • Outer cortex - immature T cells
• Secondary lymphoid structures
  • House lymphocytes and other immune cells - Site of immune response initiation
  • Lymph nodes, spleen, tonsils, MALT
• Lymph nodes:
  • Afferent (many) and efferent (one) lymphatic vessels
  • Capsule
  • Outer cortex
    • Germinal center - house proliferating B cells and macrophages
    • Mantle zone - T cells, macrophages, dendritic cells
    • Cortical sinuses - tiny channels lined by macrophages
  • Inner medulla
    • Medullary cords - CT fibers that support T and B cells and macrophages
    • Medullary sinuses - tiny channels lined by macrophages
• Spleen:
  • White pulp - monitor foreign substances
  • Red pulp - store RBC and platelets
• Tonsils:
  • Immune surveillance for anything we inhale or ingest
  • Pharyngeal, palatine, lingual
• Lymphoid nodules:
  • Clusters of lymphoid cells
  • Walls of appendix and body organs
  • Defend against infections
• MALT:
  • Prominent in SI
  • Peyer patches
  • Prominent in lamina propria of mucosa layers