Download Chapter 42: Circulatory System Circulatory System – Heart, blood

Chapter 42: Circulatory System
Circulatory System – Heart, blood, & vessels
 Functions
o Transports dissolved gases, nutrients, hormones, & metabolic wastes (e.g. urea, lactic acid)
o Regulation of pH, electrolytes (ions)
o Repair damaged tissue & vessels
o Defense against toxins & pathogens
o Stabilization of body temp
 Open Circulatory System
o Insects (most arthropods), & most molluscs
o Hemolymph bathes organs directly
 No distinction b/w blood & interstitial fluid (just body fluid)
o ‘Heart’ pumps into open cavities
 Closed Circulatory System
o Annelids, cephalopods, & vertebrates
o Blood confined to vessels & distinct from interstitial fluid
o More efficient at transporting circulatory fluids to tissues & cells
Cardiovascular System – Circulatory & Lymphatic Systems
 Blood Vessels (~50,000 miles)
o Arteries
 Carry blood away from heart
 Branch into arterioles which lead to capillary beds
 Heavy smooth muscle w/ elastin fibers, endothelial lining
 Deals w/ high pressure
 Very elastic (arterioles = less)
o Veins
 Return blood to the heart
 Capillaries converge into venules, then converge into veins
 Same layers w/ less muscle
 Very low pressure
 B/w muscles (contract = blood moves)
 Valves – prevent blood backflow
 Diaphragm pressure also moves blood
o Capillaries
 Thin-walled vessel
 One endothelial cell thick
 Facilitates exchange using all diffusion & bulk transport types
 Form dense, branched beds; 1,000 mi2 (only 250 of 5,000 ml of blood)
 Blood 500x slower than in artery
 Nutrient Exchange
 Occurs b/w blood & interstitial fluid across thin endothelial walls
 Difference b/w blood pressure & osmotic pressure drives fluids…
o Out of capillaries at arteriole end
o Into capillaries at the venule end
 Most blood proteins & all blood cells too large to pass thru endothelium
 Lymphatic System
o Fluid called lymph
o Transports lipids from digestion, contains lymphocytes, returns interstitial fluid to circulatory system
 Lymphatic ducts drain into subclavian veins in neck
o Valves in vessels prevent backflow
o Lymph Node
 Oval shaped gland
 Filled w/ honey-combed sacs made from connective tissue
 Space filled w/ lymphocytes
 Made in bone marrow, mature in thymus, spleen, tonsils
 Filter foreign materials & fight infections (multiply = swelling)
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Heart
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4 muscular chambers enclosed in pericardium (i.e. sac)
 2 Atria – collect venous blood & pump into…
 2 Ventricles – pump blood to lungs & body
Cardiac Muscle
 Striated & involuntary
Cardiac Valves
 Atrioventricular Valves (lub)
 B/w Atria & Ventricles
o Close during ventricular systole
 Right = Tricuspid Valve
 Left = Bicuspid Valve
 Semilunar Valves (dub)
 B/w Ventricles & 1st artery
o Close during ventricular diastole
 Right Ventricle & Pulmonary Artery
 Left Ventricle & Aorta
Cardiac Cycle
 Diastole – relaxation phase
 Systole – contraction phase
 Process
 Atrial/Ventricular diastole (filling up)
 Atrial systole fills up ventricle (diastole)
 Ventricular systole propels blood out
Cardiac Output (resting ~5 L/min)
 Blood volume pumped per minute
 = Heart rate (beats/minute) & Stroke volume (amount pumped)
Blood Pressure
 Systolic Pressure (big #) – pressure exerted on arterial walls during ventricular systole
 Diastolic Pressure (small #) – pressure exerted on arterial walls during ventricular diastole
Heartbeat
 Occurs w/o nervous stimulation
 Contraction starts in Right Atrium
 Sinoatrial (SA) Node = Pacemaker
 Cell mass that starts heartbeat
 Impulse spreads thru gap junctions & causes atrial contraction
 Atrioventricular (AV) node
 B/w Right Atrium & Ventricle
 Impulse pauses to allow full filling of ventricles
 Impulse spreads thru Bundle of HIS (‘hiss’) & Purkinje Fibers (muscle)
 Ventricles Contract
Cardiac Control
 Pacemaker regulated by…
 Nervous System
o Sympathetic speeds up heart
 Accelerator nerve from spine (spinal nerve)
o Parasympathetic slows down heart
 Vagus nerve form brain (cranial nerve)
 Hormones (epinephrine = fast)
 Temperature
 Blood Flow
 High resistance = slow flow
o Capillaries have highest resistance & slowest flow
 Vasodilation – smooth muscles relax in arterioles; blood pressure down
o Nitric oxide is a major inducer
 Vasoconstriction – smooth muscles contract in arteriole walls; blood pressure up
 Precapillary sphincters can reduce capillary blood flow; helps divert blood elsewhere
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Pulmonary Circulation
 Right Ventricle-Lungs-Left Atrium
 Right Ventricle pumps de-oxy blood through Pulmonary Arteries
 Arteries to arterioles to lung capillaries
o O2 in & CO2 out (now oxy blood)
 Capillaries to Venules to Pulmonary Veins to Left Atrium
o Systemic Circulation
Systemic Circulation
 Left Ventricle-Body-Right Atrium
 Left Ventricle pumps oxy blood through Aorta to…
 Systemic Arteries to arterioles to body capillaries
 Venules to Superior & Inferior Vena Cavae to Right Atrium
 Systemic Divisions
 Coronary Circuit – Heart
o Coronary Arteries & Veins
 Cranial Circuit – Head
o Carotid Arteries & Jugular Veins
 Brachial Circuit – arms
o Brachial Arteries & Subclavian Veins
 Mesenteric Circuit – Digestive System & Liver
o Mesenteric Arteries, Hepatic Portal Vein, Hepatic Vein
 Renal Circuit – Kidney
o Renal Arteries & Veins
 Lower Appendage Circuit – legs
o Femoral Arteries & Iliac Veins
General Blood Path
 Right Atrium – Tricuspid Valve – Right Ventricle – Semilunar Valve – Pulmonary Arteries –
Arterioles – Lung Capillaries – Venules – Pulmonary Veins – Left Atrium –Bicuspid Valve –
Left Ventricle – Semilunar Valve – Aorta – Systemic Arteries – Arterioles – Body/Organ
Capillaries – Venules – Superior & Inferior Vena Cavae
Blood
 Characteristics
o Temp – 38° C (100.4 ° F)
o Viscosity – 5x Water
o pH – 7.35-7.45
o Volume
 5-6 L adult males & 4-5 L adult females
 Blood Plasma (55%)
o Water
 92% of plasma volume
 Solvent for transport
 Gases – O2 & CO2
 Organic wastes – urea, uric acid, NH4+, creatinine, bilirubin
o Plasma Proteins
 7% of plasma volume
 Made in Liver
 Albumin – osmotic balance & transports insoluble molecules
 Globulin
o Transport globulin – move lipids, ions, others (e.g. LDL)
o Immunoglobulin – antibodies
 Fibrinogen (inactive) – clotting
 Hormones & enzymes (regulatory)
o Ions
 aka blood electrolytes
 1% of plasma volume
 Osmotic balance, pH buffer, regulate membrane permeability
 Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, HPO42-, SO42-
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Blood Cells (45%)
o Hematopoiesis
 Process of blood cell formation
 Liver & spleen – embryo only
 Red (bone) Marrow
 Hematopoietic stem cells
o Can become all blood cells
o Mitosis makes more
o Differentiate & released
o Erythrocyte (RBC)
 Biconcave disc
 No nucleus, mitochondria, ribosomes
 Transports O2 & some CO2
 250 million hemoglobins (4 O2)
 ~25 trillion RBCs in humans
 Erythropoiesis stimulated by Erythropoietin (EPO; Low O2)
 Ribs, vertebrae, sternum, & pelvis
o Leukocyte (WBC)
 Larger, colorless, nucleated
 Often mature in lymph tissue
 e.g. T Lymphocyte named for Thymus
 Can leave circulatory system
 Basophil, eosinophil, neutrophil, lymphocyte, monocyte
 Dendritic cell, NK cell, T & B lymphocytes, macrophage
o Platelet
 Very small amount of blood cells
 Cellular fragments that bud off from large stem cells in marrow
 Plays a critical role in coagulation (formation of solid clot from liquid blood)
 Blood Clotting
 Triggered when endothelium damaged & connective tissue exposed
 Platelets adhere to collagen
o Release substance making surface sticky & more platelets stick
o Tissue Factor (III; protein) released by damaged cells & platelets (starts
cascade)
 Clotting Cascade
o Mulit-step Clotting Factor cascade ends w/ inactive prothrombin (II)
converted into thrombin
 Turns fibrinogen (I) into fiber
 Surround platelets & RBCs
 Shrink, pull together = clot
o Thrombus – clot inside blood vessel
 Embolus – free-floating thrombus
Cardiovascular Disease
 Disorders of heart & vessels, #1 cause of death
 Cholesterol
o Steroid is a temp buffer for membrane
o Low-density lipoprotein (LDL from liver) delivers cholesterol to cells for membrane production
o High-density lipoprotein (HDL) scavenges cholesterol for return to liver
o High LDL/HDL ratio = High heart disease
 Atherosclerosis
o Growth of plaques in inner wall of arteries (narrows lumen)
o Endothelium Inflammation (injury) starts process
 LDL enters artery lining; macrophages come & engulf (form foam cells)
 Extracellular matrix forms attracting more LDL & macrophages (plaque grows)
o Plaque can rupture; blood clot formed
o Arteriosclerosis (artery hardening) occurs if calcium is deposited
 Blockages
o Heart Attack (myocardial infarction)
 Death of cardiac muscle tissue resulting from blockage of one or more coronary arteries
(supply oxy blood to heart muscle)
o Stroke
 Death of nervous tissue in brain, usually resulting from rupture or blockage of arteries in head
o Angina pectoris
 Caused by partial blockage of coronary arteries & results in chest pains
 Hypertension
o High Blood Pressure
 Promotes atherosclerosis & increases risk of heart attack & stroke
 Increases chances of endothelium inflammation (increases pressure)
o Can be reduced by dietary changes, exercise, and/or medication