Respiration in Vertebrates

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Every eukaryotic cell needs oxygen.
So the big question is...
How does the organism get oxygen to every cell?
2
Small Organisms (single or few cells)

• Single-celled organisms can simply absorb Oxygen
  from the environment through diffusion
• No circulatory or pulmonary system needed
• Just a large surface area that is moist is all
  that is needed.

http//www.mhhe.com/biosci/genbio/biolink/j_explor
ations/ch02expl.htm
Cell size
3
Large organisms use special respiratory
structures, eg.
Gills in fish
Skin in frog
Lungs in mammals

• Skin
• Gills
• Lungs

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Two basic strategies in multicellular organisms
28.2
28.4

• Respiratory surface has thin lining
• Develop specialized respiratory exchange surfaces
  that maximize surface area for diffusion of
  respiratory gases

5

• In order to maintain the maximum possible rate of
  diffusion respiratory surfaces have a number of
  characteristics
• 1. Large surface area to volume ratio
• This may be the body surface in small
  organisms or
• infoldings of the surface such as lungs,
  gills
• 2. Permeable
• 3. Thin - Diffusion is only efficient over very
  short distances, e.g. 1 mm
• Rate of diffusion is inversely proportional to
  the square of the distance between the
  concentrations on the two sides of the
  respiratory surface.

6

• 4. Moist - since oxygen and carbon dioxide
  diffuse in solution form
• 5.Efficient transport system - This is necessary
  to maintain a diffusion gradient and may
  involves a vascular system.

7
Constraints on gas exchange in land animal

• Diffusion across cell membranes requires that
  respiratory gases are first dissolved at the cell
  membrane surface
• cell membranes must be wet
• water loss is a unavoidable consequence of gas
  exchange in most environments
• Two designs
• internal
• external

28.9
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Types
1
2
4
3
6
5
9
Gas exchange in terrestrial animals

• Most terrestrial animals have invaginated
  respiratory structures
• lungs
• tracheae

28.18
10
Ventilation is needed

• Moving the air or water past the respiratory
  structures greatly increases their effectiveness.

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• TABLE 20.1 Water and Air as Respiratory Media

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• TABLE 20.1 Water and Air as Respiratory Media

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• TABLE 20.1 Water and Air as Respiratory Media

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• TABLE 20.1 Water and Air as Respiratory Media

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• TABLE 20.1 Water and Air as Respiratory Media

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• TABLE 20.1 Water and Air as Respiratory Media

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• TABLE 20.1 Water and Air as Respiratory Media

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19
Anatomical dead space
20
Lung volumes
Vital capacity
Volume of air in lung
Tidal volume
Residue volume
Time
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20.4 Measurement of Lung Capacity
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• Measurement of Lung Capacity
• Tidal volume is the volume of air breathed in or
  out during each respiratory cycle 
• Vital capacity is the total amount of air that
  can be forcibly inspired or expired 
• Residue volume is the amount of air that remains
  in the lungs even after maximum expiration
• Ventilation rate is the process of exchanging
  gases in the lungs/gills with gases from the
  environment per unit time. 

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Human Lungs Structure and Function
28.19

• Human lungs are very finely partitioned into
  blind sacs called alveoli
• Gas exchange facilitated by
• large surface area
• high breathing rates

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Lung tissue
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How large are the respiratory surfaces provided
by the lungs ?
About half the size of a tennis court.

• Alveoli - a respiratory surface with a total area
  of about 100 m2

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• Features for efficient gas exchange
• 1. Very thin so that gases can diffuse through
  very quickly
• 2. A large surface area to diffuse more gases
  per unit time
• 3. Moist so that gases can pass through in
  solution forms
• 4. An excellent transport system of blood
  capillaries to transport gases

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Mechanism of Breathing
Animation
Photo
28
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The 4 steps of Respiration in Mammals
1. Air or water, containing oxygen, is moved past
a respiratory surface by bulk flow. 2. O2 and CO2
are exchanged through the respiratory surface by
diffusion. O2 enters the capillaries and CO2 is
removed. 3. Gases are transported between the
respiratory system the tissues by the bulk flow
of blood (pumped by the heart) 4.Gas exchange
between tissue and circulatory system. O2
diffuses out of capillaries and CO2 diffuses into
them.
Diffusion movement of particles from a region
of high concentration to one of low
concentration. Bulk flow movement of many
particles from an area of higher pressure to
one of lower pressure
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Gaseous Exchange in the alveoli
Capillary from pulmonary artery
Red blood cell
Owing to concentration differences
Oxygen diffuses into RBCs
Epithelium of alveolus (1-cell thick)
Film of moisture
Carbon dioxide diffuses into alveolus
Capillary to pulmonary vein
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• Carbon dioxide in the form of hydrogen carbonate
  ions in plasma diffuses to the alveoli because of
  its higher concentration in blood

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Human Respiratory System
http//krupp.wcc.hawaii.edu/BIOL100/present/respir
at/index.htm
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Diffusion of O2 and CO2

• When a cell carrying O2 nears another cell that
  is lacking in O2, diffusion will occur
• When a cell is lacking in O2 and nears an O2 rich
  region, diffusion will occur
• The same process happens with CO2

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Summary of diffusion in the lungs and tissue
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So now we understand how this diffusion works
between neighboring cells
The next question is...
How do the cells far away get oxygen?
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Transporting O2 and other stuff(The Circulatory
System)

• A liquid conduit containing the liquid blood
• This Bulk Flow is necessary to bring O2 to every
  cell in the body
• Also necessary to protect and upkeep cells
• The liquid that is circulated around has a number
  of components...

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Human Lungs
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Human Alveoli
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Gas Exchange
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20.3 Control of Ventilation in Man
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Control of Breathing
Respiratory centre
Chemoreceptor
pCO2
42

• Control of Ventilation in Man
• Rate and depth of breathing is controlled by the
  respiratory centre in the medulla oblongata of
  the hind-brain by changes in blood CO2
  concentration
• Blood CO2 in blood
• ?? detected by chemoreceptors
• ?? nerve impulses
• ?? respiratory centre in medulla

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Control of Ventilation in Man
44

• Control of Ventilation in Man
• Rate and depth of breathing is controlled by the
  respiratory centre in the medulla oblongata of
  the hind-brain by changes in blood CO2
  concentration
• Blood CO2 in blood
• ?? detected by chemoreceptors
• ?? nerve impulses
• ?? respiratory centre in medulla

• ?? phrenic thoracic nerves
• ?? diaphragm intercostal muscle contractions
• ?? Inspiration

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Control of Ventilation in Man
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• ?? stretch receptors in lungs stimulated
• ?? vagus
• ?? expiratory centre in medulla to switch off
  the inspiratory centre
• ?? expiration takes place

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20.3 Control of Ventilation in Man
48

• ?? stretch receptors in lungs stimulated
• ?? vagus
• ?? expiratory centre in medulla to switch off
  the inspiratory centre
• ?? expiration takes place

?? stretch receptors not stimulated ??
expiratory centre switched off ?? inspiratory
centre switched on ?? inspiration again
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Control of Ventilation in Man
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• The ventral portion of the breathing centre is
  the inspiratory centre
• the remainder is the expiratory centre
• Chemoreceptors in the carotid and aortic bodies
  of the blood system

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• The breathing centre may also be stimulated by
  impulses from the forebrain resulting in a
  conscious increase or decrease in breathing rate.
• The main stimulus for ventilation is carbon
  dioxide
• Changes in oxygen concentration have relatively
  little effect.

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• At high altitudes the reduced atmospheric
  pressure makes it more difficult to load the
  haemoglobin with oxygen.
• In an attempt to obtain sufficient oxygen a
  mountaineer takes very deep breaths.
• This forces more carbon dioxide out of the body
  and the level of carbon dioxide in the blood
  therefore falls.
• The inspiratory centre is no longer stimulated
  and breathing becomes increasingly laboured,
  causing great fatigue.

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Gas Exchange in Plants
28.6
28.3

• Epidermis dry and impermeable
• large intercellular spaces between spongy
  mesophyll cells means each cell has direct
  contact with air
• air enters the leaf through gates called
  stomata, controlled by guard cells
• humidity within leaf near 100, water loss is
  minimized

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How do stomata work?
28.5

• Thickened walls along the inside edges force
  guard cells closed when cells lack water pressure
  (low turgor)
• no water loss and no gas exchange
• When turgid, thickened walls cause a pore to open
  between guard cells
• water loss (transpiration) and gas exchange occur

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Stems and Roots Must Exchange CO2 and O2 also
28.8

• Pores in stems called lenticels allow gas
  exchange
• many cells of living stems are dead (providing
  strucural support only)
• Root can be deprived of oxygen in waterlogged
  soils