CAMPBELL BIOLOGY IN FOCUS URRY CAIN WASSERMAN MINORSKY REECE 34 Circulation and Gas Exchange Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge, Simon Fraser University 2016 Pearson Education, Inc. SECOND EDITION Open Circulatory Systems Circulatory systems have different-sized vessels that facilitate bulk flow and diffusion. Open circulatory systems: no vessels to transport hemolymph (blood & interstitial fluid) Mollusks (snails, oysters, clams), Arthropods (insects, spiders,

lobsters) Closed Circulatory Systems Closed circulatory systems: also called cardiovascular systems Well-defined blood vessels Earthworms, echinoderms, chordates, all vertebrates Vessel Size Artery: away from the heart;(NOTE: most arteries carry oxygenated blood, but not always) Arterioles: smaller Capillaries: consist only of endothelium for diffusion of gases Venule: small vein Vein: to heart (NOTE: usually carries deoxygenated blood, but not always) Gas exchange Arteries and veins are composed of

3 layers: Outer: connective tissue with elastin fibers Middle: smooth muscle (more elastin fibers; thicker in arteries than veins) Inner: endothelium (only layer in capillaries) NOTE: veins are much thinner than arteries Figure 34.9 Vein LM Artery Red blood cells 100 mm

Basal lamina Endothelium Connective tissue Smooth muscle Smooth muscle Capillary Arteriole Venule 15 mm Capillary bed LM

Red blood cells in capillary 2016 Pearson Education, Inc. Valve Endothelium Connective tissue Vessel Area Vs. Flow Velocity Capillaries in total have largest area, therefore slowest velocity (blood flow comes to a standstill in capillaries) Arteries have faster velocities than veins BP: main force driving blood from heart to capillaries; BP is highest in aorta and arteries; lowest in veins SO, how does blood flow in veins?

Contracting skeletal muscles of veins Have one-way valves Keeps blood moving to the heart If we sit or stand too long, the lack of muscular activity make our feet swell, with stranded fluid Must avoid DVT (Deep Vein Thrombosis) Figure 34.11 Direction of blood flow in vein (toward heart) Valve (open) Skeletal muscle Valve (closed) 2016 Pearson Education, Inc.

4,000 2,000 0 40 20 0 120 2016 Pearson Education, Inc. Venae cavae Arteries 40 Diastolic pressure 0 Veins

80 Arterioles Capillaries Venules Systolic pressure Aorta Pressure (mm Hg) Velocity (cm/sec) Area (cm2) Figure 34.10

BLOOD FLOW IN CAPILLARY BEDS Pre-capillary sphincters regulate passage of blood into capillary beds If sphincters relaxed, blood flows into beds I.e. into digestive system after we eat If sphincters contracted, capillary beds are closed; blood flow reduced to thoroughfare channel I.e. into skeletal muscles after we eat Therefore, might have a leg cramp swimming too soon after eating Pressure Fish Heart & Circulatory System The evolution of animal hearts reflects selection for a higher

metabolic rate, achieved by increasing the delivery of oxygen to metabolically active cells. Fish: 2-chambered heart and 1 circuit of blood flow Amphibian Heart & Circulatory System Amphibians and reptiles: 3-chambered heart and a partially divided circulatory path Figure 34.4 (a) Single circulation: fish Gill capillaries Artery Heart: Atrium (A)

Ventricle (V) Vein Body capillaries Oxygen-rich blood Oxygen-poor blood 2016 Pearson Education, Inc. (b) Double circulation: amphibian (c) Double circulation: mammal Pulmocutaneous circuit Pulmonary circuit Lung

and skin capillaries Atrium (A) Atrium (A) Right V Left Lung capillaries A V Right

A V Left Systemic capillaries Systemic circuit Systemic capillaries Systemic circuit Mammalian Heart & Circulatory System Birds and mammals: 4-chambered heart Fully divided pulmonary and systemic circulations Pulmonary circulation:

From heart to lungs Systemic circulation: From heart to rest of body Figure 34.5 Superior vena cava Pulmonary artery Capillaries of right lung Pulmonary vein Right atrium Right ventricle Inferior vena

cava 2016 Pearson Education, Inc. Aorta Capillaries of head and forelimbs Pulmonary artery Capillaries of left lung Pulmonary vein Left atrium Left ventricle Aorta Capillaries of abdominal organs and hind limbs

FLOW OF BLOOD THROUGH PULMONARY & SYSTEMIC SYSTEMS From body (deoxy) Down from superior vena cavae and up from inferior vena cavae (deoxy) Right atrium (deoxy) Right ventricle (deoxy) To lungs (via Pulmonary Arteries: deoxygenated) Back to left atrium (via Pulmonary Veins: oxygenated) Left ventricle (oxy) Arch of aorta (oxy) To body Figure 34.6 Pulmonary artery Aorta Pulmonary artery

Right atrium Left atrium Semilunar valve Semilunar valve Atrioventricular (AV) valve Atrioventricular (AV) valve Right Left ventricle ventricle

2016 Pearson Education, Inc. HEART Heart: mostly cardiac muscle; striated and branched Cone-shaped organ; size of clenched fist, just under sternum Enclosed in pericardial sac Atrium/atria: receive blood to heart Top 2 chambers, thinner walled.only pump to ventricles Right atrium: received deoxygenated blood from body Left atrium: receives oxygenated blood from lungs Ventricles: pump blood out of heart Bottom 2 chambers; thicker walled Right ventricle: pumps deoxygenated blood to lungs Left ventricle: pumps oxygenated blood to body Heart Valves Between right atrium and right ventricle: Tricuspid AV Valve

Between left atrium and left ventricle: Bicuspid or Mitral AV Valve Between right ventricle and lungs: Pulmonary Semilunar Valve Between left ventricle and aorta: Aortic Semilunar Valve 2016 Pearson Education, Inc. BLOOD PRESSURE Blood pressure: pushing force exerted by blood against walls of blood vessels Greatest in major arteries attached directly to heart (aorta, pulmonary artery) Decreases with distance from heart BP is main force driving blood flow Creates a blood pressure gradient (I.e. blood flows into lower pressure arteries from higher pressure ones) Brachial artery: on upper arm; most frequent site for taking BP using stethescope and sphygmomanometer (mm Hg)

Cardiac Cycle Figure 34.7-s3 Atrial systole and ventricular diastole Atrial and ventricular diastole 0.1 sec 0.4 sec 2016 Pearson Education, Inc. 0.3 sec Ventricular systole

and atrial diastole Blood Pressure Contd Systolic BP: upper number Average 120 mm Hg Caused by systole (contracting and emptying); lasts 0.4 secs Diastolic BP: lower number Average 80 mm Hg Caused by diastole (relaxing and filling); lasts 0.4 secs Entire cardiac cycle lasts 0.8 secs, giving a pulse (heart beat) of about 75 beats/min 2016 Pearson Education, Inc. Hypertension versus Hypotension Hypotension (low BP): below normal BP; <100/60 i.e. accidentally cut an artery Hypertension (high BP): above normal BP, >140/90 High BP may overstretch, thin out arterial walls May create aneurysms.abnormally widened out

arteries that will rupture Arteriosclerosis: hardening of walls of artery with calcium Hypertension and arteriosclerosis worsen each other; called positive feedback mechanisms (just continues to get worse) Heart Beat Basics Control of Heart Beat: initiated by SA (sino-atrial) node ; also called natural pacemaker SA node controls contraction of atria AV node controls contraction of ventricles Heart Beat Process Heart Rate: same as pulse Number of times the heart beats/min; usually about 75 beats/min at rest Increases during anxiety and/or exercise Decreases severely in seniors (they may need a pacemaker)

EKG & Cardiac Output Heart Sounds: detected by stethoscope Lub: 1st low pitch; contraction of ventricles and closing of AV valves Dupp: 2nd high pitch; closing of semilunar valves Atherosclerosis, Heart Attacks, and Stroke Damage or infection can roughen the lining of arteries and lead to atherosclerosis, the hardening of arteries due to accumulation of fatty deposits Cholesterol is a key player in the development of atherosclerosis Low-density lipoprotein (LDL) delivers cholesterol to cells for membrane production High-density lipoprotein (HDL) scavenges excess cholesterol for return to the liver Risk for heart disease increases with a high LDL to HDL ratio Inflammation, the bodys reaction to injury, is also a factor in cardiovascular disease

2016 Pearson Education, Inc. A heart attack, or myocardial infarction, is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries Coronary arteries supply oxygen-rich blood to the heart muscle A stroke is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head Angina pectoris is caused by partial blockage of the coronary arteries and may cause chest pain 2016 Pearson Education, Inc. Risk Factors and Treatment of Cardiovascular Disease A high LDL to HDL ratio increases the risk of cardiovascular disease The proportion of LDL relative to HDL is increased by smoking and consumption of trans fats and decreased by exercise

Drugs called statins reduce LDL levels and risk of heart attacks 2016 Pearson Education, Inc. Inflammation plays a role in atherosclerosis and thrombus formation Aspirin inhibits inflammation and helps reduce the risk of heart attacks and stroke Hypertension (high blood pressure) contributes to the risk of heart attack and stroke Hypertension can be reduced by dietary changes, exercise, medication, or some combination of these 2016 Pearson Education, Inc. Figure 34.16 Endothelium Lumen

Thrombus Plaque 1 mm 2016 Pearson Education, Inc. Figure 34.12 Lymphatic System Blood capillary Interstitial fluid Adenoid Tonsils Lymphatic vessels Thymus

(immune system) Spleen Tissue cells Lymphatic vessel Lymphatic vessel Lymph nodes Appendix (cecum) Peyers patches (small intestine) 2016 Pearson Education, Inc. Lymph node Masses of

defensive cells LYMPHATIC SYSTEM Circulatory function Collect excess fluids/plasma proteins (stranded fluid) from surrounding tissue and return them to deoxygenated blood in right atrium Immune function Filters lymphhas WBC waiting in lymphatic organs and lymph nodes to trap antigens and lyse them Consists of the following components: Lymph..has the same composition as interstitial fluid (also known as stranded fluid, or edema); composed of fluid, plasma proteins, escaped blood cells Lymph vessels.returns excess fluid to blood ; drains into right atrium; has one-way valves Lymphatic organs: thymus, spleen, tonsils/adenoids, appendix, Peyers patch on small intestines Lymph nodes: small bodies interspersed along lymph vessels; act as

cleaning filters and immune centers against infection; get large with infections or cancer SPLEEN Largest lymphatic organ; on left side; between diaphragm and stomach 4 functions: Filters blood for immune function; has macrophages waiting inside Destroys old RBC/recycles iron (overlaps with liver) RBC do not mitose. Old ones are destroyed and new ones made in bond marrow every 120 days. Iron is recycled for use in liver. The rest of hemoglobin is converted to bilirubin, the chief component of bile. Provides a reservoir of blood Retains large quantities of blood; contains about 33% blood platelets Spleen (and liver) produce blood cells during fetal development (before bone takes over) Figure 34.13 Mammalian Blood

Plasma 55% Constituent Major functions Water Solvent Ions (blood electrolytes) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Osmotic balance, pH buffering, and regulation

of membrane permeability Plasma proteins Albumin Leukocytes (white blood cells) 5,000-10,000 Osmotic balance, pH buffering Clotting Substances transported by blood Nutrients (such as glucose, fatty acids, vitamins) Waste products of metabolism Respiratory gases (O2 and CO2) Hormones

2016 Pearson Education, Inc. Separated blood elements Cell type Number per mL (mm3) of blood Basophils Immunoglobulins Defense (antibodies) Apolipoproteins Lipid transport Fibrinogen Cellular elements 45%

Functions Defense and immunity Lymphocytes Eosinophils Neutrophils Monocytes Platelets Erythrocytes (red blood cells) 250,000-400,000 5,000,0006,000,000 Blood clotting

Transport of O2 and some CO2 COMPOSITION OF MAMMALIAN BLOOD Blood is a type of connective tissue About 5 liters in body; pH 7.35-7.45 55% Plasma (fluids) Water, ions, hormones, fibrinogen, antibodies 45% cellular elements Erythrocytes, RBC; transport O2; nonnucleated; 1 loop RBC = 20 secs Leukocytes, WBC: defense & immunity Monocytes:/macrophages: phagocytic Lymphocytes: primary immune system cells Basophils Eosinophils Neutrophils Platelets, also called thrombocytes. Blood

clotting Figure 34.13-1 2016 Pearson Education, Inc. Figure 34.13-2 Cellular elements 45% Cell type Leukocytes (white blood cells) Basophils Number per mL (mm3) of blood 5,000-10,000 Functions Defense and immunity

Lymphocytes Eosinophils Neutrophils Monocytes Platelets Erythrocytes (red blood cells) 2016 Pearson Education, Inc. 250,000-400,000 5,000,000-6,000,000 Blood clotting Transport of O2

and some CO2 DIFFERENTIATION OF BLOOD CELLS All blood cells originate from stem cells in red marrow of bones (ribs, vertebrae, pelvis, breastbone) These differentiate into lymphoid stem cells & myeloid stem cells Lymphoid stem cells give rise to: B and T lymphocytes ( a type of leukocyte) Myeloid stem cells: RBC Platelets Other 4 WBC Figure 34.14 Stem cells (in bone marrow) Differentiation of Blood Cells

Lymphoid progenitor cells Myeloid progenitor cells B cells T cells Lymphocytes Erythrocytes Basophils Neutrophils Monocytes 2016 Pearson Education, Inc. Platelets Eosinophils

BLOOD CLOTTING Caused by appearance of rough spot in lining of blood vessel Platelets stick; get platelet plug Finally fibrin clot Figure 34.15-1 Collagen fibers Platelet plug Platelet Clotting factors from: Platelets Fibrin clot formation

Damaged cells Plasma (factors include calcium, vitamin K) Enzymatic cascade Prothrombin Fibrinogen 2016 Pearson Education, Inc. Fibrin clot Thrombin Fibrin Gas Exchange by Diffusion Respiration and circulation depend on diffusion over short distances and bulk flow over long distances. Human Gas Exchange System: Called respiration or breathing

Uptake of O2 from air; release of CO2 Gas Exchange Organs Respiration provides oxygen and eliminates carbon dioxide in support of cellular respiration. Aquatic animals exchange gases with water thru gills Terrestrial animals breathe air by internal trachae or lungs. Diffusion Diffusion: net movement of molecules from regions of higher concentration to regions of lower concentration Unicellular organisms Simple plants & animals Effective only over short distances and requires large surface areas with thin barriers I.e. sponges, sea anemones, flatworms

2016 Pearson Education, Inc. BULK TRANSPORT Bulk transport: physical movement of fluid and gases over a given distance Occurs in 2 steps: Ventilation: movement of respiratory medium (air or water) past a specialized respiratory surface Circulation: movement of specialized body fluid that carries O2 and CO2 Circulatory fluid in invertebrates: hemolymph Circulatory fluid in vertebrates: blood O2 delivered to tissues in 4 steps:

Bulk flow of water or air past lungs or gills Diffusion of O2 across lungs into circulatory system Bulk flow thru circulatory system Diffusion of O2 into tissues/cells PARTIAL PRESSURE OF A GAS With a gas, we discuss its partial pressure instead of concentration pp = the concentration of a gas in air/dissolved water At sea level: the pp of O2 = 160 mm Hg Gas will diffuse from a region of higher pp to lower Calculated as: O2 makes up 21% of atmosphere; 0.21 x 760 mm Hg (atmospheric pressure at sea level) = 160 mm Hg

Therefore, for O2 to diffuse from the air into cells, the pp of O2 inside cells must be less than the pp of O2 in the atmosphere (<160 mm Hg). Pp of CO2 = 0.23 mm Hg Figure 34.18 O2-poor blood Lamella O2-rich blood Gill arch Blood vessels Gill arch Water

flow Operculum Water flow Blood flow Countercurrent exchange P O2 (mm Hg) in water Gill filaments 2016 Pearson Education, Inc. 150 120 90 60 30 Net diffusion of O2 140 110 80 50 20 PO2 (mm Hg) in blood

Respiration by Fish Gills Countercurrent flow of water relative to blood in gills enhances O2 extraction from water Concurrent & countercurrent Exchange Countercurrent exchange: Used widely in nature i.e. fish gills Two fluids exchange properties efficiently (such as oxygen, carbon dioxide, heat, etc) Lung Anatomy Gas Transport & Exchange Coordination of Circulation and Gas Exchange Blood (deoxy) entering capillaries of lungs has a lower pO2

and a higher pCO2 than air in alveoli Therefore, O2 diffuses into capillaries and CO2 diffuses out In tissue capillaries, oxygenated blood diffuses O2 into tissues and CO2 into blood Tidal Ventilation Terrestrial vertebrates inflate/deflate lungs by bidirectional tidal ventilation driven by changes in pressure Called a Negative Pressure System Inhalation: lungs & rib cage expand, intercostal muscles of diaphragm contract/move down; air is pulled into lungs Exhalation:

lungs & rib cage compress, muscles of diaphragm relax/ move up; forces air out Figure 34.20 Branch of pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasal cavity Left lung Pharynx

Larynx (Esophagus) Trachea Right lung Branch of pulmonary artery (oxygen-poor blood) Alveoli 50 mm Bronchus Capillaries Bronchiole Diaphragm (Heart)

2016 Pearson Education, Inc. Dense capillary bed enveloping alveoli (SEM) RESPIRATORY SYSTEM Nose: warms and moistens air Trachea: cartilaginous tube that leads to lungs Epiglottis: flap of tissue that prevents food from entering trachea Swallowing blocks lungs: trachea moves up, covered by epiglottis Bronchi: 2 smaller tubes in lungs; from trachea; have primary bronchi, secondary and tertiary Bronchioles: even smaller tubes in lungs; terminal bronchioles end in air sacs called alveoli Alveoli: site of gas exchange Coated with surfactants, which keep them from sticking closed Right lung: has 3 lobes; Left lung: has 2 lobes

Diaphragm Tidal Volume Tidal Volume: volume of air inhaled and exhaled during normal breathing 0.5 l of air every cycle Ventilation Rate: breathing frequency x tidal volume I.e. with a breathing rate of 12 breaths/min, ventilation rate = 6 l/min When more O2 is needed during exercise, both breathing frequency and tidal volume increase Figure 34.UN02 Exhaled air

Alveolar epithelial cells Inhaled air Alveolar spaces CO2 O2 Alveolar capillaries Pulmonary arteries Pulmonary veins Systemic veins

Systemic arteries Heart CO2 O2 Systemic capillaries Body tissue 2016 Pearson Education, Inc. Homeostasis in Breathing Breathing Control Centers; pons and medulla oblongata in brain Autonomically regulate breathing Respond first to high CO2 levels, then lowered pH, then low O2 levels Figure 34.23-s4

Blood CO2 level falls and pH rises. NORMAL BLOOD pH (about 7.4) Medulla detects decrease in pH of cerebrospinal fluid. Cerebrospinal fluid Signals from medulla to rib muscles and diaphragm increase rate and depth of ventilation. 2016 Pearson Education, Inc.

Medulla oblongata Carotid arteries Aorta Medulla receives signals from major blood vessels. Blood pH falls due to rising levels of CO2 in tissues (such as when exercising). Sensors in major blood vessels detect decrease

in blood pH. Structure of Hemoglobin & Myoglobin Red blood cells produce hemoglobin, greatly increasing the amount of oxygen transported by the blood. Blood plasma cannot hold very much O2 in solution due to its low solubility Hemoglobin: specialized respiratory pigment found in all vertebrate RBCs RBC contain hemoglobin with iron-containing heme groups that reversibly bind and release O2 Myoglobin: binds and stores O2 in muscle cells; has greater affinity for O2 than hemoglobin; it will give up its O2 only when concentrations get very low 100 O2 unloaded to tissues at rest 80

O2 unloaded to tissues during exercise 60 40 20 0 0 20 40 60 80

100 O2 saturation of hemoglobin (%) O2 saturation of hemoglobin (%) Figure 34.26 100 pH 7.4 80 pH 7.2 Hemoglobin retains less O2 at lower pH (higher CO2 concentration) 60 40

20 0 0 20 40 PO2 Tissues during Tissues at rest exercise PO2 (mm Hg) (a) PO2 and hemoglobin dissociation at pH 7.4 2016 Pearson Education, Inc. 60 80

(mm Hg) Lungs (b) pH and hemoglobin dissociation 100 O2 saturation of hemoglobin (%) Figure 34.26-2 100 pH 7.4 80 pH 7.2 Hemoglobin retains less O2 at lower pH (higher CO2

concentration) 60 40 20 0 0 20 40 60 80 PO2 (mm Hg) (b) pH and hemoglobin dissociation 2016 Pearson Education, Inc. 100

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