Circulation and Gas Exchange Chapter 42 Circulation and Gas Exchange

Diffusion alone is not enough! I. Circulation Diffusion alone is not enough!

A. Invertebrates Gastrovascular Cavity - jelly fish and planarians - bring into g.v.c. and diffuses in Open Circulatory System - blood (hemolymph) bathes organs directly through sinuses Closed Circulatory System - blood kept in vessels and stays separate from interstitial fluid - heart pumps the blood

All have a closed circulatory system B. Vertebrates All have a closed circulatory system

1. Components Heart – one or two atria and one or two ventricles Arteries – carry blood away from the heart and lead to arterioles - 3 layers / connective tissue, smooth muscle, and endothelium - thick middle and outer layers - blood flows fastest through the arteries

1. Components Veins – carry blood to the heart and lead to venules - same three layers / thinner middle layer - one way check valves Capillaries – connect arterioles and venules - 2 thin layers - allow diffusion to occur

2. Types of Circulatory Schemes Fish - one atrium and one ventricle - gill circulation / from ventricle to gills and capillaries - systemic circulation / from gills to body and back to atrium

2. Types of Circulatory Schemes Amphibians (some reptiles) - 2 atria, one ventricle - pulmocutaneous circulation / from ventricle to lungs and skin, back to left atrium - systemic circulation / from ventricle to body, back to right atrium - double pump system

2. Types of Circulatory Schemes Mammals / Birds / Crocs - 2 atria and ventricles - double pump / right side only unoxygenated, left oxygenated - pulmonary and systemic circuit

3. Human Heart 4 valves - 2 arterioventricular / tricuspid (R), mitral (L) / “Lub” - 2 semilunar / pulmonary (R), aortic (L) / “Dub” - Ventricles thicker than atria - Know the pathway! Let’s review it!

3. Human Heart Cardiac Cycle - one complete pumping and filling - contraction is systole / relax is diastole Heart Beat Rhythm - sinoatrial (SA) node (pacemaker) are cells in the wall of the right atrium that sends rhythmic signal to atrioventricular (AV) node between the right atrium and ventricle which contracts the ventricles .1 seconds later - ECG picks that up

4. Blood Flow and Pressure - blood flows slower through capillaries because they spread out over a large area - precapillary sphincters and muscle move blood through the capillaries - muscles push blood back up the veins Pressure - systolic pressure – higher from contraction of ventricles (120) - diastolic pressure – lower from relaxing (80)

5. Lymphatic System Fluid is lost through capillary clefts and is regained by lymphatic system Lymph drains into the circulatory system near the vena cava and right atrium

6. Blood Specialized only in closed circulatory system organisms Plasma – water and proteins (antibodies, fibrinogens) RBC / Eurythrocytes – oxygen transport, biconcave, no nuclei or mitochondria, hemoglobin WBC / Leukocytes – fight infection

6. Blood Platelets – fragments for clotting - fibrinogen → fibrin / clotting factors Differentiation of Blood Cells - develop from pluripotent cells - What is erythropoietin?

7. Cardiovascular Diseases Heart attack Stroke Atherosclerosis (plaque) Arteriosclerosis (hardens) Hypertension

II. Gas Exchange - Respiratory Medium – source of oxygen - Respiratory Surface – part where gases are exchanged - Gills, tracheae, lungs are the most common respiratory organs

A. Gills Outfoldings of the body Ventilation – “waft” water over gill Countercurrent Exchange

B. Tracheal Systems Used in air More oxygen in air Air requires less ventilation Lose oxygen through evaporation Series of tubes open to outside Body movements act as lungs

C. Lungs Work with circulatory system to move oxygen and carbon dioxide around

1. Mammal Lungs Nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli Alveoli - site where gas exchange occurs - covered in surfactants which lower surface tension in the alveoli Breathing – ventilating lungs - negative pressure breathing / How does it work? - always retain a residual volume of air - birds have multiple air sacs - medulla controls breathing by “watching” the pH / carbonic acid lowers the pH

2. Transporting Gases Respiratory Pigments – hemoglobin (Fe) / hemocyanin (Cu) CO2 Transport – 7% plasma, 23% hemoglobin, 70% bicarbonate (dissociates into H+ and bicarbonate ion)

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