Transcript Respiratory System

Respiratory System
Cellular Respiration
• Most cells utilize cellular respiration to
convert the chemical energy stored in
nutrient macromolecules to the chemical
energy utilized by cells  ATP
• This process is an oxidation reaction  a
steady supply of oxygen is required to
combust glucose to carbon dioxide and
water
Cellular Respiration
Cellular Respiration
• Respiratory systems support cellular
respiration by facilitating gas exchange of
oxygen and carbon dioxide between the
organism and the environment
Evolution of Respiratory Systems
1. Simple Diffusion – gases are exchanged
across the moist exterior surface of the
organism’s body
e.g. single cell organisms; sponges; cnidaria;
and worms
2. Gills – large surface areas that are richly
supplied with blood capillaries are in close
contact with water containing dissolved gases
e.g. some mollusks and crustacea; and fish
Evolution of Respiratory Systems
3. Book Lungs – a series of moist, page-like
membranes within a chamber of the
organism that facilitate gas exchange
e.g. spiders and scorpions
4. Tracheae – system of highly branched
tubes that extend from the exterior
surface of the organism to every cell in
its’ body
e.g. insects
Book Lungs
Evolution of Respiratory Systems
5. Lungs – chambers containing moist,
delicate respiratory surfaces that are
protected within the body
e.g. amphibia through to mammals
Human Respiratory System
Four distinct stages in respiration:
1. Breathing – entrance and exit of air into
and out of lungs
2. External respiration – gas exchange
between air and blood
3. Internal respiration – gas exchange
between blood and body cells
4. Cellular respiration – in body cells
Human Respiratory System
•
The human respiratory system consists
of two distinct parts:
1. Conducting portion – a series of
passageways that carry air by bulk flow into
the gas exchange portion
2. Gas exchange portion – membraneous sacs
where gases are exchanged between air in
sacs and blood in capillaries
Conducting Portion
Purpose – to carry air to the respiratory
membranes in the lungs
1. Nose Nasal cavity Pharynx, or Mouth
Oral cavity Pharynx (common chamber)
2. Pharynx Larynx (contain vocal cords)
3. Larynx Trachea (rings of cartilage)
4. Trachea Left or Right Bronchus
5. Bronchus Bronchioles
6. Bronchioles Alveoli (singular : alveolus)
The Lungs
• Paired, cone shaped organs that lie on
either side of the heart in the thoracic
cavity
• Right lung has 3 lobes, the left lung has 2
lobes (allowing room for the heart)
• Bronchus, bronchioles and alveoli are
contained in each lung
Conducting Portion
•
As air travels through the conducting
portion, it is:
1. Warmed
2. Moistened
3. Filtered
by mucus and cilia (tiny hairs) that line the
conducting portion
Gas Exchange Portion - Alveolus
• Each lung contains approximately 300
million alveoli
• Individual alveoli are tiny – 0.2 mm
diameter – but collectively the alveoli
provide 70 square meters of surface area
for gas exchange
• This surface area is the size of a tennis
court, and is 40x the surface area of your
skin
Alveolus
• The alveoli cluster together at the end of a
bronchiole like a cluster of grapes
• The cluster of alveoli are surrounded by an
intricate network of blood capillaries
• Because the alveolus is only one cell layer thick,
and the blood capillary is one cell layer thick,
gases are able to move by diffusion between our
blood and the air we breathe in
• This diffusion of gases is facilitated by a thin
layer of water that coats the interior surface of
each alveolus
Gas Exchange: External
Respiration
1.
2.
3.
4.
High CO2/ low O2 blood is pumped from the right
ventricle of the heart, through the pulmonary arteries,
to the capillaries that surround each alveolus
The air in the alveoli is high in oxygen, so oxygen
moves by diffusion into the blood of the alveolar
capillaries
The blood in the lung capillaries is high in carbon
dioxide, so carbon dioxide moves by diffusion into the
alveoli sacs
High O2/ low CO2 blood leaves the alveolar capillaries,
through the pulmonary vein, to the left atrium of the
heart
Gas Exchange: Internal Respiration
1.
2.
3.
4.
The left ventricle pumps high O2/ low CO2 blood along
the aorta and arteries to the capillaries that are in
contact with individual cells
The blood in the body capillaries has more oxygen
than the body cells, so oxygen diffuses from the blood
into the body cells
The body cells have more carbon dioxide than the
blood, so carbon dioxide diffuses from the body cells
into the blood in the body capillaries
High CO2/ low O2 blood leaves the body capillaries,
travels through veins and the vena cava to the right
atrium
Chemistry of Gas Exchange
Oxygen
• <5% of oxygen travels in
blood as a dissolved gas
• >95% of oxygen travels in
blood attached to
hemoglobin
(oxyhemoglobin)
Carbon Dioxide
• 10% of carbon dioxide
travels in blood as
dissolved gas
• 20% of carbon dioxide
travels in blood attached
to hemoglobin
(carbaminohemoglobin)
• 70% of carbon dioxide
reacts with water in blood
plasma to form the
bicarbonate ion (HCO3-)
Hemoglobin
• Hemoglobin preferentially binds oxygen
over carbon dioxide (but oddly, binds
carbon monoxide preferentially over
oxygen!)
• 1 hemoglobin molecule is able to bind 4
oxygen molecules
• Because of hemoglobin our blood can
carry 70x more oxygen than it would as a
dissolved gas in plasma
Bicarbonate Ion
CO2 + H20  H2CO3 (carbonic acid)
H2CO3  H+ + HCO3• This reaction is catalyzed by carbonic
anhydrase embedded in the capillary walls
• This reaction is reversible
External Respiration
1. HbCO2

Hb
carbaminohemoglobin
2. H+
+
HCO3-
3. H2CO3

+ CO2 (g)↑

H2O +
4. Hb
+
O2(g)↓ 
deoxyhemoglobin
5. HHb

Hb
reduced hemoglobin
H2CO3
CO2 (g)↑
HbO2
oxyhemoglobin
+
H+
HHb
HbCO2
Hb
O2
Internal Respiration
1. HbO2 
Hb
+
2. Hb
+
CO2

HbCO2
3. CO2
+
H 2O

H2CO3
O2
4. H2CO3 
H+
+
HCO3-
5. Hb
H+

HHb
+
HbCO2
Hb
HHb
Binding Capacity of Hemoglobin
• pH and temperature affect the binding
capacity of hemoglobin
• Cooler temperature (37 C) and higher pH
(7.40) of lungs raises oxygen binding
capacity of hemoglobin to 98%
• Warmer temperature (38 C) and lower pH
(7.38) of body cells lowers the oxygen
binding capacity of hemoglobin to 60%
Binding Capacity of Hemoglobin
• This is important as the hemoglobin/RBC
in the lung capillaries want to be able to
bind as much oxygen as possible from the
air in the alveoli
• The hemoglobin/RBC in the body
capillaries want to be able to release
oxygen to the body cells and pick up
carbon dioxide from the body cells
Mechanics of Breathing
• Breathing is the entrance and exit of into
and out of the lungs
• Exhalation= Expiration= air exiting the
lungs
• Inhalation= Inspiration= air entering the
lungs
• Breathing is a biomechanical process
Features of Thoracic Cavity
•
For breathing to occur, the thoracic cavity must
be air-tight:
1. The interior of the thoracic cavity is lined with an airtight membrane called the parietal pleura
2. Each lung is surrounded with an air-tight membrane
called the visceral pleura
3. The space between the two pleura (interpleural
cavity) contains a lubricant
4. The muscular diaphragm seals the bottom of the
thoracic cavity
Thoracic Cavity
Inhalation
1. Diaphragm contracts and drops down
2. Intercostal muscles in the rib cage
contract and push up and out
3. The thoracic cavity increases in volume
4. Pressure in the lungs decreases
5. Air rushes into the lungs
Inhalation
Exhalation
1. Diaphragm relaxes and moves up
2. Intercostal muscles in the rib cage relax
and move down and in
3. The thoracic cavity decreases in volume
4. Pressure in the lungs increases
5. Air rushes out of the lungs
Exhalation
Stimuli for Breathing: Inhalation
• Primary stimuli: rising
CO2 and H+ ion levels
trigger the respiratory
center in the medulla
oblongata of the brain 
nerve impulse is sent
along intercostal nerve to
contract intercostal
muscles and along
phrenic nerve to contract
diaphragm
Stimuli for Breathing: Inhalation
• Secondary stimuli:
decreasing O2 levels
trigger
chemoreceptors in
carotid bodies of
carotid arteries and
aortic bodies of aorta
 nerve impulse to
respiratory center of
medulla oblongata
Stimuli for Breathing: Exhalation
• Primary stimulus: as air moves into the
lungs during inhalation, the alveoli sacs
expand  this stimulates stretch receptors
around the alveoli  initiates a nerve
impulse sent to the respiratory center to
turn off inhalation nerve impulse