Chapter 42 Circulatory Outline PDF

Chapter 42 – Circulation Overview Form and Function Must exchange energy with environment, so size and shape must adapt to function in that environment Circulatory system is an adaptation to form that allows exchange with enviro...

Chapter 42 – Circulation Overview Form and Function Must exchange energy with environment, so size and shape must adapt to function in that environment Circulatory system is an adaptation to form that allows exchange with environment to occur at the cellular level (across plasma membrane) Purpose of the Circulatory System ◦ To connect body cells that are in an aqueous environment to organs of exchange ◦ To maintain homeostasis CONCEPT 42.1: CIRCULATORY SYSTEMS LINK EXCHANGE SURFACES WITH CELLS THROUGHOUT THE BODY Invertebrates Circulation 2-cell layer Cnidaria (phylum that contains jellyfish, sea anemone, hydra) No need for a “real” circulatory system Figure 42.2 Internal Transport in Body is only 2 cell layers thick therefore material doesn’t Gastrovascular Cavities have to travel far Have gastrovascular cavity which functions for both digestion and circulation of nutrients throughout the body Ch 42 – Circulatory Revised 1  Fluid bathes both inner and outer tissue layers which facilitates exchange of gases and cellular wastes Multiple Cell Layers (more complex, need circulatory system) Components of Circulatory Systems Circulatory fluid (i.e blood) Tubes (i.e. interconnected blood vessel) Muscular pumps (i.e. heart) The circulatory system connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of wastes Open Circulatory System Arthropods and most Mollusks No distinction between circulatory fluid (hemolymph) and interstitial fluid (solution that surrounds cells) Figure 42.3 Open and Closed Circulatory Systems One or more hearts contract to pump hemolymph through vessels into sinuses Chemical exchange occurs between hemolymph and body cells Relaxation of heart(s) draws hemolymph back through pores Closed Circulatory System Ch 42 – Circulatory Revised 2  Annelids and Cephalopods Blood kept inside of vessels separate from interstitial fluid More efficient at delivering oxygen and nutrients to tissue One or more hearts pump blood into large vessels that branch into smaller vessels which infiltrate organs to allow for chemical exchange Chemical exchange occurs between blood and the interstitial fluid as well as between interstitial fluid and body cells Vertebrate Circulation Vertebrates (closed →cardiovascular system) General Structure – has blood vessels and a 2 or 4 chambered heart Arteries Carry blood away from the heart Thick Can withstand great pressure Arterioles Arteries branch into arterioles within organs Small vessels that convey blood to capillaries Capillaries Very thinned walled Site of chemical exchange between blood and interstitial fluid Will converge into venules Venules Will converge into veins Veins Ch 42 – Circulatory Revised 3  Carry blood back to the heart Remember arteries and veins are distinguished by direction of blood flow Arteries = away from heart to capillaries Veins = to heart from capillaries Higher metabolic rate = more complex circulatory system Variation between organisms Fish 2 chambered heart → 1 ventricle and 1 atrium Pathway of blood flow Ventricle to gills (gets oxygen and gets ride of carbon dioxide) Gills to other parts of body Other parts of the body to atrium Atrium to ventricle Figure 42.4a Examples of Vertebrate Circulatory Schemes (Part 1: Fish) Amphibians 3 chambered heart (1 ventricle, 2 atria) Mixing of oxygen rich and oxygen poor blood in ventricle before ventricle pumps blood to both Lungs (oxygen poor blood) Other body parts (oxygen rich blood) Ch 42 – Circulatory Revised 4  Double circulation One circuit to lungs (pulmonary) Figure 42.4b Examples of Vertebrate Circulatory Schemes One circuit to body (systemic) (Part 2: Amphibian) Reptiles 3 chambered heart (1 ventricle and 2 atria) Ventricle partially divided by a septum Double circulation Mammals and birds 4 chambered heart (2 ventricles and 2 atria) Left side chambers get oxygen rich blood from lungs Right side chambers get oxygen poor blood from body Figure 42.4c Examples of Vertebrate Circulatory Schemes (Part 3: Mammal) Form Relates to Function Endotherms require 10X the energy as ectotherms of the same size Circulatory system must deliver 10X the oxygen and nutrients to tissues therefore need a large, powerful 4-chambered heart Ch 42 – Circulatory Revised 5 CONCEPT 42.2: COORDINATED CYCLES OF HEART CONTRACTION DRIVE DOUBLE CIRCULATION IN MAMMALS Mammalian Circulation Pathway Blood from body enters right atrium via vena cavae (deoxygenated) Superior – upper body Inferior – lower body Blood goes to right ventricle through the atrial ventricular valve (Tricuspid) atrial ventricular valve = any valve between atrium and ventricle Blood pumps out of the right ventricle through a semilunar valve via the pulmonary artery to the lungs. Gets oxygen and gets rid of carbon dioxide. Blood returns from lungs and enters the left atrium via the pulmonary vein (oxygenated) Blood goes to the left ventricle through another atrioventricular valve (bicuspid/mitral) Blood is pumped out of the left ventricle through another semilunar valve via the aorta Systemic circuit First branches are the coronary arteries – supplies blood to heart muscle Blood is delivered to body tissues – unloads oxygen and picks up carbon dioxide Blood from body returns to right atrium Ch 42 – Circulatory Revised 6  Figure 42.5 The Mammalian Cardiovascular System: An Overview Mammalian Heart The human heart is about the size of a clenched fist and consists mainly of cardiac muscle The two atria have relatively thin walls and serve as collection chambers for blood returning to the heart The ventricles have thicker walls and contract much more forcefully Figure 42.6 The Mammalian Heart: A Closer Look Ch 42 – Circulatory Revised 7  How Heart Works Cardiac Cycle Rhythmic contraction and relaxation of the heart Systole – contraction (pumping) Diastole – relaxation (filling) Figure 42.7_3 The Cardiac Cycle (Step 3) Cardiac Output Volume of blood pumped into circuit (body) per minute Depends on: Heart rate – beats per minute (pulse) Stroke volume – amount of blood pumped by left ventricle in single contraction Valves Atrioventricular valve (between atrium and ventricle) Semilunar valve (between ventricle and artery) The “lub-dup” sound of a heart beat is caused by the recoil of blood against the AV valves (lub) then against the semilunar (dup) valves Defects Heart murmur Ch 42 – Circulatory Revised 8  Valves do not close completely Blood flows backward Maintaining Heartbeat Muscle Cardiac muscle is self-excitable It can contract on its own Pacemaker For humans it is the sinoatrial node (SA node) Sets the rate/timing of the cardiac muscle contraction Generates electrical impulses Impulse spreads through atria and to the AV node AV node sends the impulse to ventricle which contracts through movement of Purkinje Fibers In hospital, electrodes on skin to keep track of heart rate detects electrical impulse from SA node Impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG) Ch 42 – Circulatory Revised 9  Pacemaker good control center but affected by: Hormones, body temperature, exercise Figure 42.8 The Control of Heart Rhythm CONCEPT 42.3: PATTERNS OF BLOOD PRESSURE AND FLOW REFLECT THE STRUCTURE AND ARRANGEMENT OF BLOOD VESSELS. Blood Vessel Structure and Function Blood Vessels All blood vessels contain a central lumen lined with an epithelial layer that lines blood vessels 3-layers of tissue Outside – connective tissue (flexible) Contains elastic fibers Middle – smooth muscle Inside – endothelium Single layer of flattened epithelial cells Smooth surface therefore low resistance to flow Arteries Ch 42 – Circulatory Revised 10  Thick walls because blood pumped out of heart at high pressure Have elastic recoil to help maintain blood pressure Nerve impulses and hormones will dilate or constrict the smooth muscle, thus controlling blood flow Veins Thinner walls Blood is pushed through by contraction of skeletal muscle Veins have valves to keep blood from flowing backwards due to the low pressure Capillaries Capillaries are only slightly wider than a red blood cell Capillaries have thin walls, the endothelium plus its basal lamina, to facilitate exchange of materials Ch 42 – Circulatory Revised 11  Figure 42.9 The Structure of Blood Vessels Blood Flow Velocity Blood Flow Rate (depends on type of vessel) Physical laws governing movement of fluids through pipes affect blood flow and blood pressure Arteries – very fast Veins – slow Capillaries Slowest due to high resistance Large cross-sectional area Makes sense since capillaries are points of exchange between blood and interstitial fluid Blood Pressure Blood flows from areas of higher pressure to areas of lower pressure Blood pressure is a force exerted in all directions, including against walls of blood vessel Ch 42 – Circulatory Revised 12  The recoil of elastic arterial walls plays a role in maintaining blood pressure Systolic pressure The highest pressure in arteries during ventricular systole (contraction) AV valve closing - lub Diastolic pressure The pressure in arteries during diastole (relaxation) Semilunar valve closing - dup A pulse is the rhythmic bulging of artery walls with each heartbeat Blood pressure is generally measured for ana rtery in the arm at the same height as the heart Blood pressure for a healthy 20-year-old human at rest is about 120mmHg at systole and 70mmHg as diastole Gravity has a significant effect on blood pressure Ch 42 – Circulatory Revised 13  Figure 42.11 Measurement of Blood Pressure Function of Capillaries Overview Don’t always have blood flowing through all capillaries (5-10% of body’s capillaries have blood flowing through) Remember though that we have many capillaries, so each tissue/organ always has an ample blood supply Brain, heart, kidneys and liver are usually filled to capacity Other organs/tissues tend to vary After eating, blood supply is increased in the digestive track Regulatory Function of Capillaries Ch 42 – Circulatory Revised 14  Capillaries lack smooth muscle (they have endothelium) Two mechanisms regulate distribution of blood in capillary beds Constriction or dilation of smooth muscle of arterioles Precapillary sphincters are rings of a smooth muscle located t entrance oof capillary beds They receive signals (nerve impulses, hormones, etc.) Figure 42.13 Blood Flow in Capillary Beds which causes them to open/close, regulating blood flow. True Function of Capillaries Exchange between blood and interstitial fluid Driven by pressure Blood pressure on artery side of capillary (arteriole) is higher therefore pushes fluid out But blood proteins that don’t leave (too large) Figure 42.14 Fluid Exchange create osmotic pressure between blood and between Capillaries and the interstitial fluid, therefore causing fluid to move Interstitial Fluid back in Ch 42 – Circulatory Revised 15  Arteriole side – blood pressure high, osmotic pressure lower Venule side – blood pressure little lower osmotic pressure almost the same Fluid Return by the Lymphatic System The lymphatic system returns fluid that leaks out from capillary beds. Fluid lost by capillaries is called lymph Edema is swelling caused by disruptions in the flow of lymph Lymph nodes are organs that filter lymph and play an important role in the body’s defense CONCEPT 42.4: BLOOD COMPONENTS FUNCTION IN EXCHANGE, TRANSPORT, AND DEFENSE Blood Composition and Function It is connective tissue because there are many cell types suspended in plasma ◦ 45% of blood volume = cells ◦ 55% is plasma Plasma Plasma is similar in composition to interstitial fluid, but plasma has a much higher protein concentration Components 90% water (solvent) Ch 42 – Circulatory Revised 16  Electrolytes (dissolved ions/salts) Some are buffers (pH~7.4) Affects composition of the interstitial fluid Must be kept in a narrow concentration range Plasma Proteins Buffers against pH change Help maintain balance between blood and interstitial fluid Contributes to viscosity (thickness) Responsible for immunity, blood clotting, and transport lipids Cellular Components Erthrocytes (red blood cells) most numerous blood cells Bioconcave disks that lack nuclei Main function is to transport oxygen Due to hemoglobin (iron containing molecule that binds four oxygen molecules) Each erythrocyte has about 250 million hemoglobin molecules Leukocytes (white blood cells) White blood cell count changes when fighting infection Found also in interstitial fluid and lymphatic system Main function is to fight infection (immunity) Ch 42 – Circulatory Revised 17  Types of Leukocytes Basophils, lymphocytes, eosinophils, neutrophils, monocytes Platelets Cytoplasmic fragments of bone marrow cells Function in blood clotting Figure 42.16 The Composition of Mammalian Blood Made from stem cells Located in red marrow of bones, (ribs, vertebrae, sternum, and pelvis) Form both myeloid and lymphoid cell lineages Ch 42 – Circulatory Revised 18  Figure 42.17 Differentiation of Blood Cells Blood Clotting Blood vessel damage Exposes proteins that attracts platelets Platelets release clotting factors that trigger the making of thrombin Also makes nearby platelets sticky Sticky platelets form an emergency plug Thrombin is an enzyme that will convert fibrinogen to fibrin Fibrin aggregates into threads and forms a fibrin clot that reinforces the platelet plug Ch 42 – Circulatory Revised 19  Figure 42.18a Blood Clotting (Part 1: Detail) Types of Cardiovascular Disease Atherosclerosis Cholesterol plaque builds up in arteries (hardening of the arteries) Hypertension High blood pressure increases the chance of atherosclerosis, heart attack and stroke due to damage of the endothelium lining which promotes plaque formation Heart Attack (myocardial infarction) Damage or death of cardiac muscle tissue because of blockage of coronary artery(s) Blockage deprives oxygen Stroke Nerve tissue in brain dies due to lack of oxygen Ch 42 – Circulatory Revised 20  Usually result from rupture or blockage of arteries in the head Ch 42 – Circulatory Revised 21