Respiratory
System
RESPIRATORY STRUCTURES
OUR GOALS TODAY...
Identify and give functions for each of the
following:
– nasal cavity
– pharynx
– larynx
– trachea
– bronchi
– bronchioles
– alveoli
– diaphragm and ribs
– pleural membranes
– thoracic cavity
Explain the roles of cilia and mucus in the
respiratory tract
Explain the relationship between the structure and
function of alveoli
Upper Respiratory Tract
• Nostrils – mucousal cell layer
• Pharynx – common passage for air
and food
• Epiglottis
Trachea
• Connects pharynx to smaller air
passageways
• C-shaped rings of cartilage
– Keep Trachea Open
– Structural Support
• Larynx (vocal box)
• Vocal Cords are composed
to 2 tendons that adjust the
pitch of sounds
Bronchi
• Trachea branch
into bronchi
• Cartilage Present
• Bronchi branch
further into
bronchioles
• Bronchiole Tree
• End at Alveoli
Alveoli
• Blind sac-like ends on bronchioles
• Millions per lung
Alveoli
• Highly specialized:
– Walls only 1 cell thick to help with the diffusion of
gases
– Coated with lipoproteins in their inner surface to
sustain surface tension (required so they don`t
collapse when you exhale)
– Stretch receptors – nerve endings that respond
to stretch (send message to medulla oblongata
that signals you to exhale when alveoli are full)
– Highly vascularized with pulmonary capillaries for
gas exchange and to prevent alveoli from drying
out
REMEMBER OUR GOALS TODAY...
Identify and give functions for each of the
following:
– nasal cavity
– pharynx
– larynx
– trachea
– bronchi
– bronchioles
– alveoli
– diaphragm and ribs
– pleural membranes
– thoracic cavity
Explain the roles of cilia and mucus in the
respiratory tract
Explain the relationship between the structure and
function of alveoli
Assignment
• Describe the location and function of
the following structures:
– Diaphragm and Ribs
– Thoracic Cavity
– Pleural Membrane
MECHANICS OF BREATHING
Our Goals Today...
• Describe the interactions of the following structures in
the breathing process:
–
–
–
–
–
–
Respiratory centre in the medulla oblongata
Lungs
Pleural membranes
Diaphragm
Intercostal (rib) muscles
Stretch receptors
• Compare the processes of inhalation and exhalation
• Explain the roles of carbon dioxide and hydrogen ions
in stimulating the respiratory centre in the medulla
oblongata
• Explain the roles of oxygen, carbon dioxide, and
hydrogen ions in stimulating carotid and aortic bodies
Medulla Oblongata
• Sensitive to the concentration of CO2
and H+ in the blood plasma
• Considered toxins and must be
excreted
• When concentrations get high enough
the medulla oblongata sends nerve
impulses to the diaphragm and
intercostal muscles
Diaphragm & Intercostal
Muscles
• Diaphragm – muscles located below the
lungs
– Moves down when it contracts
• Intercostal Muscles – between ribs
– Moves rib cage up and out during
contraction
• These muscle contractions increase the
volume of the thoracic cavity – creates a
vacuum effect drawing air in (negative
pressure)
• Contraction requires ATP
Pleural Membrane
•
•
•
•
Double membrane
1 surrounds the lungs
1 lines the inside of the thoracic cavity
2 functions:
– Allow lungs to slide in the chest cavity
easily
– Seals thoracic cavity (so negative
pressure can develop for inhalation)
• Pneumothorax
Exhalation
• Stretch receptors detect when the
alveoli are stretched open
• This signals the Medulla Oblongata to
direct the diaphragm and intercostal
muscles to relax
• Diaphragm moves upwards and
ribcage moves in and down – causing
exhalation
Chemoreceptors
• Located in the aortic arch and carotid
arteries
– Sensitive to oxygen levels in the blood
– If it gets too low then it will signal
inhalation
• Secondary mechanism
– Blood Plasma CO2 and H+ primarily cause
inhalation
Remember Our Goals...
• Describe the interactions of the following structures in
the breathing process:
–
–
–
–
–
–
Respiratory centre in the medulla oblongata
Lungs
Pleural membranes
Diaphragm
Intercostal (rib) muscles
Stretch receptors
• Compare the processes of inhalation and exhalation
• Explain the roles of carbon dioxide and hydrogen ions
in stimulating the respiratory centre in the medulla
oblongata
• Explain the roles of oxygen, carbon dioxide, and
hydrogen ions in stimulating carotid and aortic bodies
GAS EXCHANGE
Our Goals Today...
• Describe the exchange of carbon dioxide and
oxygen during internal and external respiration,
including
– location of exchange
– conditions that favour exchange (e.g., pH,
temperature)
• Explain the roles of oxyhemoglobin,
carbaminohemoglobin, reduced hemoglobin,
bicarbonate ions, and carbonic anhydrase in the
transport of carbon dioxide and oxygen in the
blood
• Write the chemical equations for internal and
external respiration
Air is Conditioned in 3 Ways
1) Thoroughly Cleaned
– Nose hairs and mucus of nasal
passageways
– Mucosal lining and cilia along trachea
and bronchi (trap and move anything
other than gases and move them up to
mouth)
2) Temperature adjusted to around 37˚C
3) Becomes saturated with water
Overview
• Breathing (Inhaling and Exhaling)
• External Respiration (gases exchanged
between the lungs and blood)
• Internal Respiration (gases exchanged
between the blood and tissues)
• Cellular Respiration (ATP production by
mitochondria)
External Respiration
• In the alveoli blood is around 37˚C
and has a pH of 7.4
– Under these conditions hemoglobin freely
combines with oxygen
• Hemoglobin has 4 binding sites for
oxygen (oxyhemoglobin – HbO2)
• HbO2 delivers O2 to tissues for internal
respiration
Internal Respiration
• At the tissues the blood is around 38˚C
and has a pH of 7.35
– These conditions cause HbO2 to release
O2 as blood enters the capillary beds
• O2 diffuses into tissues with water
(capillary fluid exchange)
Internal Respiration
• At the venule side of the capillary recall
that water re-enters the blood with CO2
due to osmotic pressure
• pH and temperature conditions result in
most of the CO2 reacting with H2O
CO2 + H2O → [H2CO3] → HCO31- + H1+
– Catalyzed by Carbonic Anhydrase
– Bicarbonate ions act as a buffer throughout
the body
– Hydrogen ions are transported in hemoglobin
(HHb) so that they don`t change the pH of
the blood
Internal Respiration
• Rest of the CO2 either bonds to
hemogloblin (carbaminohemoglobin
/HbCO2)
• OR is transported as dissolved gas in
the plasma
• Blood enters the veins and goes
through the heart and the pulmonary
circuit back to the lungs
Back at the Lungs...
• Blood returning to the alveolar capillaries
is transporting bicarbonate ions and
some carbon dioxide gas
• Hemoglobin is transporting either H+ or
CO2
• Temperature is slightly lower and pH is
slightly higher causing hemoglobin to
release H+ and CO2
• Enzyme carbonic anhydrase catalyzes
the reverse reaction
HCO31- + H1+ → [H2CO3] → CO2 + H2O
The end of the story...
• Carbon dioxide diffuses into the
alveoli and is exhaled
• Some water is also exhaled
• Hemoglobin is free to bind to oxygen
Remember Our Goals Today...
• Describe the exchange of carbon dioxide and
oxygen during internal and external respiration,
including
– location of exchange
– conditions that favour exchange (e.g., pH,
temperature)
• Explain the roles of oxyhemoglobin,
carbaminohemoglobin, reduced hemoglobin,
bicarbonate ions, and carbonic anhydrase in the
transport of carbon dioxide and oxygen in the
blood
• Write the chemical equations for internal and
external respiration