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Flashcards in lecture 16 part 2 Deck (17):

three main phases of gas exchange

1. breathing
-exposes a lrage moist internal surface to air
-oxygen diffuses across the cells lining the lung into surrounding blood vessels
-carbon dioxide diffuses out of the blood and into the lung
2. transport of gases
-oxygen that diffused into the blood blinds to hemoglobin in red blood cells
-carbon dioxide is also transported in the blood from the tissues to the lungs
3. bodily cells take up oxygen from the blood and release Co2
-oxygen is the terminal electron acceptor during cellular respiration in the mitochondria


gas exchange across moist body surfaces

-the respiratory surface is the location of gas exchange within the animal
-composed of living cells that must be kept moist to maintain function
-gas exchange occurs by diffusion
-must have large surface area
-entire outer skin surface is used for gas exchange
-no specialized organs
-a capillary layer immediately below the surface receives oxygen
-must live in damp places as the entire organism must be wet
-organisms that ventilate this way are usually small and many long and thin


other mechanisms of gas exchange: gills

-extensions/outfolding of the body surface
-specialized for gas exchange
-oxygen diffuses across the gill surface into a capillary bed
-carbon dioxide diffuses out of the fish from the capillary bed out of the gill
-maintaining a moist surface is not problematic


other mechanisms for gas exchange: tracheal system

tracheal system:
-respiratory system is contained within the animal
-extensive system of branching internal tubes
-respiratory system is at the tips of the tubes
-gases are exchanged directly with body cells
-circulatory system is not required


other mechanisms of gas exchange: lungs

-found in the most terrestrial vertebrates
-internal sacs lined with moist epithelium
-large amount of branching internally
-forms a large respiratory surface
-gases are moved between the lungs and the body cells via the circulatory system



-oxygen is present in water as dissolved gas
-respiratory surfaces are easily kept moist
-less oxygen in water than in air
-gills must be very efficient


gill structure

-four gill arches on each side of the body
-two rows of gill filaments project from each gill arch
-each filament has many plate-like structures called lamallae
-the lamallae are the actual respiratory surfaces
-the lamallae are full of tiny capillaries, so small that the RBC's must pass through single file
-ventilation is illustrated by the blue arrows in the diagram
-water goes into the mouth of the fish and out the side
-the may simply open the mouth allowing water to flow
-fish may also actively pump water across the gills by the opening and closing of the mouth and opeculum


counter current exchange

-blood flows opposite the movement of water past the gills
-called counter current exchange
-transfer of material from a fluid moving in one direction to a fluid moving in the opposite direction


tracheal systems

-breathing air is advantageous
-much higher oxygen concentration
-air is very light weight, requires less energy
-trachae: largest tubes
-open to the outside of the animals
-reinforced with chitin
-enlarged portions form air sacs near organs that require high oxygen supply
-trancheoles are the smallest branches extending to every cell in the animal body
-gas is exchanged with body cells directly across this surface
-no circulatory system necessary
-some insects alternately contract and relax flight muscles to pump air rapidly through the tracheal system
-do not use circulatory system (simple organisms)



-mammalian lungs located in the thoracic cavity
-separated from abdominal cavity by thick muscle called the diaphragm
-air enters through nostrils
-filtered by cilia and warmed and humidified as it travels
-moves through to pharynx
-because there is joining of the mouth contents to the respiratory epiglottis evolved
-covers the trachea when we swallow food in order to prevent choking
-air then travels through the larynx where vocal cords are located
-from the larynx air travels down the trachea
-lined with cilia and a thin mucus layer
-moist epithelial cells
-cartilaginous rings keep trachea open
-from the trachea air passes through the bronchi
-two bronchi branch from the trachea and enter each lung
-the bronchi further branch into smaller tubules called bronchioles
-bronchioles end in sacs called aveoli which are the site of gas exchange
-each alveolus is surrounded by a dense network of capillaries
-oxygen diffuses across the alveous and into the capillary network
-alveolus covered with a thin layer of surfacant ( waxy layer)
-decreases surface tension


blood transports respiratory gases

-oxygen enters the blood at the lung and carbon dioxide is subsequently unloaded
-this occurs by diffusion of gases down their concentration gradient


circulation facilitates exchange
2 types of systems:

-two basic types of circulatory systems:
-open circulatory system
-closed circulatory system


open circulatory system

-found in most invertebrates
-fluid pumped through open-ended vessels
-flows out among cells
-there is no distinction between blood and interstitial fluid
-bodily movements help to circulate fluid throughout
-fluid returns to the heart through several pores
-each pore has a valve to protect against back flow


closed circulatory system

-vertebrate circulatory system
-called cardiovascular system
-blood is confined to vessels
-keeps it distinct from interstitial fluid
-ex) closed of a fish
-2 chambered heart
-atrium receives blood from veins
-ventricle pumps blood to gills
- after passing through gills large arteries carry oxygenated blood to the rest of the body
-arteries become arterioles which become capillaries which exchange material between blood and intestinal fluid
-capillaries become venules which become veins


three types of vessels

-arteries: carry blood away from the heart to body tissues
-veins: return blood to the heart
-capillaries: convey blood between arteries and veins at the tissue level


double circulation

-after loosing pressure in the capillaries of the lung blood is pumped a second time
-pulmonary circuit: carries blood between the heart and the rest of the body
-amphibians such as frogs have three chambered heart
-mixing of blood (oxygenated and deoxygenated occurs in the ventricle)
-some animals such as turtles and snakes have the ventricle partially divided to minimize mixing
-birds and mammals have a four chambered heart:
-two atria
-two ventricles
-right side of heart handles deoxygenated blood
-left side of heart handles oxygenated blood
-supports the high metabolic rate of endothermic mammals


human cardiovascular system

-right ventricle pumps deoxygenated blood into lungs via pulmonary arteries
-blood flowing through the lung capillaries unloads carbon dioxide and picks up oxygen
-oxygen rich blood returns to the heart via pulmonary veins into the left atrium which then flows into left ventricle
-from the left ventricle this blood exits into systematic circulation via the aorta
-aorta has branched called coronary arteries which supply the heart with blood
-also has branches to supply head, neck, arms, and into the abdomen
-in the tissues arteries lead into arterioles and then capillaries
-capillaries become venules and then veins
-veins converge into the inferior and superior vena cava which return deoxygenated blood to the right artira of the heart
-blood then flows into the right ventricle and back into pulmonary circulation