lecture 16 part 2

Question 1

three main phases of gas exchange

Answer 1

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

Question 2

gas exchange across moist body surfaces

Answer 2

• 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
• earthworms:
• 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

Question 3

other mechanisms of gas exchange: gills

Answer 3

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

Question 4

other mechanisms for gas exchange: tracheal system

Answer 4

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

Question 5

other mechanisms of gas exchange: lungs

Answer 5

• 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

Question 6

gills

Answer 6

• 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

Question 7

gill structure

Answer 7

• 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

Question 8

counter current exchange

Answer 8

• 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

Question 9

tracheal systems

Answer 9

• 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)

Question 10

lungs

Answer 10

• 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

Question 11

blood transports respiratory gases

Answer 11

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

Question 12

circulation facilitates exchange

2 types of systems:

Answer 12

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

Question 13

open circulatory system

Answer 13

• 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

Question 14

closed circulatory system

Answer 14

• 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

Question 15

three types of vessels

Answer 15

• 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

Question 16

double circulation

Answer 16

• 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

Question 17

human cardiovascular system

Answer 17

• 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