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Respiratory SystemsChapter 37
2Respiratory Systems
Gas Exchange Surfaces
Respiration:The events associated with gas exchange between the cells and the external environment
Consists of these steps:Ventilation = inspiration (air in) & expiration (air out)External Respiration = gas exchange between external environment & the blood within respiration surfaces. Blood then transports oxygen to the tissues. Internal Respiration = gas exchange between blood & tissue fluid. Cells exchange gases with tissue fluid. Blood transports carbon dioxide back to respiratory surfaces.
3Respiratory Systems
Gas Exchange SurfacesFor diffusion to be effective, gas-exchange
tissues must be:Moist because gases must be in solutionThin to allow for rapid diffusionRelatively large in relation to size of body to ensure that cells get oxygen in a timely fashion
Relatively small, and flat, animals don’t need a specialized respiration system:
Planaria - flat, 2-dimensional body allows surface of animal to be gas-exchange surface
Larger, more 3-dimensional animals need specialized gas-exchange surfaces such as gills or lungs.
4Respiratory Systems
Gas Exchange Surfaces
Effectiveness of diffusion is enhanced by vascularization:
• Gas-exchange surfaces are usually associated with capillary beds so that oxygen and carbon dioxide can be exchanged efficiently.
Delivery of oxygen to cells is promoted by respiratory pigments such as hemoglobin that can pick up the oxygen and carry it.
5Respiratory Systems
Gas Exchange in Water Environments
I. Difficulties obtaining oxygen in water compared to air:
A. Water contains only a fraction of the oxygen that would be present in the same volume of air 1. Oxygen has low solubility in water
0.004% in seawater; 21% in air. B. Diffusion of oxygen in water is thousands of
times slower than in airC. Water is more dense than air
1. Use more energy to respire than do land animals.
•Fish use up to 25% of energy output torespire while terrestrial animals
only use 1-2% of their energy output.
6Respiratory Systems
Gas Exchange in Water Environments
II. Small, simple multicellular animals: A. Planaria, hydra
1. Gastrovascular cavity helps put cells in contact with oxygenated water
B. Aquatic worms 1. Use skin that is supplied with blood
vessels
7Animal Shapes and Gas Exchange
8Respiratory Systems
Gas Exchange in Aquatic Environments
III. Larger aquatic animals like bony fishes •Often have gills:
Outward extensions of pharynx; said to be evaginated
Have finely subdivided surfaces with a huge total surface area
Contain a rich supply of blood vessels (vascularized)
Ventilation is brought about by combined action of the mouth drawing water in and gill covers (operculum) forcing water out of head area
9Anatomy of Gills in Bony Fishes
10Respiratory Systems
Countercurrent Exchange System
Countercurrent Exchange System in Fish Gills: •In lamella of gills:
Blood flows in the direction opposite to the movement of water across the gills.
This maximizes the amount of oxygen picked up by the blood:
- As the blood gains oxygen, it always encounters water having an even higher oxygen content.
- No equilibrium is ever reached. 80-90% of dissolved oxygen is extracted.
If flow of blood was concurrent to water (same direction) an equilibrium point would occur and less oxygen would be transferred into blood.
11Anatomy of Gills in Bony Fishes
12Respiratory SystemsRespiration in
Terrestrial Environments:
Air has much more available oxygen than water but it is a drying environment. Thus, terrestrial animals tend to have invaginated respiratory systems to protect them from too much water loss.
- Exception is earthworms which breathe through their skin but must keep body surface moist by secreting mucus, etc. - Earthworms also do their best to remain in
damp soil during the daytime.
13Respiratory SystemsLand Environments:
Tracheae
Insects and other terrestrial arthropodsRespiratory system consists of branched air tubes called tracheae
Oxygen enters tracheae at spiracles, valvelike openings on each side of the body.
Tracheae branch & branch until they end in tiny channels, the tracheoles, that are in direct contact with body cells.
Very efficient system for delivering oxygen to cells that does NOT involve any respiratory pigments or circulatory system.
14Tracheae of Insects
15Respiratory SystemsLand Environments:
Lungs of VertebratesTerrestrial vertebrates have evolved lungs
Vascular outgrowths from lower pharyngeal region Lungs of amphibians Possess a short tracheae which divides into two bronchi that
open into lungs Many also breathe to some extent through skin
Reptiles Inner lining of lungs is more finely divided in reptiles than in
amphibians Lungs of birds and mammals are elaborately subdivided
All terrestrial vertebrates, except birds, use a tidal ventilation system Air moves in and out by the same route. Thus, fresh incoming air is mixed with some left-over stale air.
16Ventilation in Frogs
Amphibians use both negative & positive pressure to ventilate their lungs:
1. Negative pressure: With mouth closed but nostrils open, the floor of the mouth is lowered. The lower air pressure will cause air to rush into their mouth cavity.
2. Positive pressure: With mouth & nostrils shut, floor of mouth rises & pushes air into the lungs.
17Respiratory SystemsVentilation in
Terrestrial Vertebrates Inspiration in mammals (Inhalation)Create negative pressure in lungs
The rib cage is elevated by intercostal muscles. The diaphragm contracts and pushes down towards belly Thoracic pressure decreases to less than atmospheric pressure
Atmospheric pressure forces air into the lungsExpiration in mammals (Exhalation)Create positive pressure in lungs
The rib cage is lowered as intercostal muscles relax The diaphragm relaxes and rises back up towards chest Thoracic pressure increases to more than atmospheric pressure
Forces air out the lungs
18Inspiration Versus Expiration
19Respiratory Systems
Ventilation in Birds
Birds use a one-way ventilation mechanism in lungsHow does this work? - Incoming air does not directly enter the lungs,
instead it is carried by trachea to a set of posterior air sacs.
- Air is then pushed through tiny tubes called parabronchi which are surrounded by capillaries
- Air ends up in anterior air sacs which expel it from body.
Thus, fresh & used air never mix in the lungs of birds. Results in a higher partial pressure of oxygen in the lungs
Oxygen uptake with each breath is greater than in other vertebrates
20Respiratory System in Birds
21Respiratory Systems
Human Respiratory System
As air moves through upper respiratory system (nostrils, nasal cavities, pharynx, larynx, trachea): It is filtered to free it of debris (cilia help thisWarmed, andHumidified
When air reaches lungs It is at body temperature, and Its humidity is 100%
22The Human Respiratory Tract
23Respiratory Systems
Human Respiratory SystemAir passes from pharynx through glottis, an opening in
larynxLarynx (voice box) contains vocal cords which allow us
to produce soundsTrachea
Permanently held open by cartilage rings Facilitates movement of air
When food is swallowed: The larynx rises, and The glottis is closed by a flap of tissue called the epiglottis
Backward movement of soft palate covers the entrance of nasal passages into the pharynx
24The Human Respiratory Tract
25Respiratory Systems
Human Respiratory System
Trachea divides and forms two primary bronchiBronchi enter the right and left lungs
Bronchi branch until there are a great number of tiny bronchioles. The walls of bronchioles get thinner & rings of cartilage are no longer present. Each bronchiole terminates in an elongated space enclosed by a great number of air pockets, or sacs, called alveoli. Gas exchange occurs between air in sacs and blood in surrounding capillaries.
26The Human Respiratory Tract
27Respiratory Systems
Control of Breathing Rate in Humans
Average person takes a breath about 14 times per minute when at restRespiratory control center, located in pons & medulla oblongata of the brain, can change the normal rate according to circumstances.
- When a drop in pH is noted (due to increase in CO2) the control center increases rate & depth of breathing.
- Normally, O2 concentration in blood has little effect on breathing rate. However, if O2 level is very low detectors in aorta & carotid arteries send an alarm to resp. control centers in brain.
28Respiratory Systems
Gas Exchange and Transport
External Respiration 1. Blood flowing into pulmonary capillaries has
higher CO2 concentration than air in the alveolar air sacs.
CO2 diffuses out of pulmonary capillaries & into air sacs.
2. Blood coming into pulmonary capillaries has lower concentration of O2 than alveolar air.
O2 diffuses from alveoli into capillaries.
29External and Internal respiration
30Respiratory Systems
Transport of OxygenMost oxygen that enters the pulmonary capillaries combines with hemoglobin in red blood cells to form oxyhemoglobin.
- Each of the 4 polypeptide chains of hemoglobin is folded around a heme (iron) group. Iron forms a loose bond with oxygen.
•At normal partial pressure of O2 in lungs, hemoglobin is almost saturated with oxygen.
•At partial pressure of O2 in tissues, oxyhemoglobin gives up much of its oxygen during internal respiration.- Acidity & warm temperatures promote this response in the tissues.
31Hemoglobin
32Hemoglobin Saturationin Relation to Temperature and Acidity
33Respiratory Systems
Transport of Carbon DioxideInternal RespirationCarbon dioxide enters blood from the tissues 1. Some carbon dioxide combines with hemoglobin to
form carbaminohemoglobin 2. Most carbon dioxide is transported in the form of
bicarbonate ions (HCO3-)
- CO2 combines with water, forming carbonic acid (H2CO3) & then dissociates into H+ & HCO3
-.- Carbonic anhydrase, an enzyme, speeds up
this reaction. - H+ combines with globin part of hemoglobin
(HHb) & HCO3- diffuses into plasma. This plays
vital role in maintaining proper pH of blood.
34External and Internal respiration
35Respiratory Systems
Transport of Carbon DioxideExternal Respiration 1. As blood enters the pulmonary capillaries,
most of the CO2 is present in plasma as HCO3
-
2. HHb gives up the H+ it has been carrying & carbonic anhydrase speeds up this
reaction:
H+ + HCO3- H2CO3 H2O + CO2
3. Now free CO2 diffuses out of blood into the
alveoli of lungs.
36External and Internal respiration
37Respiratory Systems
Respiration and Health
Upper Respiratory Tract Infections
Consists of nose, pharynx & larynx. Infections can spread from nasal cavities to sinuses, to middle ears & to larynxStrep ThroatUsually starts as viral infection that becomes a secondary bacterial infection.Caused by Streptococcus pyogenes. Can become generalized upper respiratory infection.Symptoms: severe sore throat, high fever, white patches on dark red throat
38Respiratory Systems
Respiration and Health
Sinusitis Infection of sinuses, facial cavities that drain into nasal cavitiesDevelops when nasal congestion blocks openings into the sinuses
Tonsillitis Infection of tonsils, masses of lymphatic tissue.Tonsils help to remove pathogens from pharynx
Laryngitis Infection of larynx accompanied by hoarseness & possibly an inability to talk.
39Respiratory Systems
Respiration and Health
Lower Respiratory Tract Infections Infections of trachea, bronchi, bronchioles &
lungsAcute bronchitis Infection of primary and secondary bronchiUsually preceded by a viral upper respiratory infection that led to secondary bacterial infection
40Respiratory Systems
Respiration and Health
PneumoniaViral, bacterial or fungal infection of the lungs in which bronchi and alveoli fill with pus & fluidMost often preceded by influenza, the “flu”.Can be localized in specific lobules of lungs; more lobules the more serious the infectionAIDS patients often get a rare pneumonia caused by a fungus called Pneumocystis carinii.
41Respiratory Systems
Respiration and Health
Pulmonary tuberculosis (TB)Caused by tubercle bacillus, a type of bacterium.Can test people with a simple skin test to see if they have been exposed to tuberculosisReaction to bacterium: 1. When the bacteria invade the lung, the cells
build a protective capsule around the bacteria. This capsule is called a tubercle.
2. With a good immune system the body might kill the encapsulated bacteria
3. With a weakened immune system, like in AIDS, the bacteria can be released & hurt the
body
42CommonBronchial and Pulmonary Diseases
43Respiratory Systems
Disorders
Pulmonary fibrosisFibrous connective tissue builds up in the lungsDue to inhalation of particles such as silica, coal dust, asbestos & fiberglass.
Lungs can’t inflate properlyAsbestos also associated with cancer
Chronic bronchitisAirways inflamed and filled with mucusCoughing causes bronchi to undergo changes, including loss of cilia & normal cleansing action
Most frequent cause is smoking.
44CommonBronchial and Pulmonary Diseases
45Respiratory Systems
Disorders
EmphysemaAlveoli are distended (stretched) and walls are damaged reducing surface area available for gas exchange
Often preceded by chronic bronchitisElastic recoil of lungs is reduced; thus expiration is very difficult
Heart works harder to force more blood to lungsSymptoms: breathlessness & cough, depression & irritability
46CommonBronchial and Pulmonary Diseases
47Respiratory Systems
Disorders
AsthmaAirways are unusually sensitive to specific irritantsWhen exposed to the irritants, the smooth muscles in the bronchioles undergo spasms Irritants can be pollen, animal dander, dust, cigarette smoke, fumes & even cold airNot curable but is treatable with inhalers that can control inflammation of bronchioles & prevent attack or stop muscle spasms during an attack
48CommonBronchial and Pulmonary Diseases
49Respiratory Systems
Disorders
Lung CancerBegins with thickening and callusing of the cells lining the airways
Loss of cilia follows; thus it is impossible to prevent dust & dirt from settling into lungs
Atypical nuclei appear in callused liningCreates a tumor of such cellsFinal step is when some cells break loose & penetrate other tissues (metastasis)