Unit 2A
Human Form & Function
Body systems
The respiratory system
Further information
• Further information about this topic can be found in Our Human Species (3rd edtn)
Chapter 11, sections 1-2, 4-6
Background reading
• Our Human Species (3rd edtn.)
Chapter 11, Gas Exchange
Sections 1, 2, 4, 5, 6, 7
Student work book
Topic 9, Respiratory system
The respiratory system
Structure
Organs of the respiratory system
Larynx
TracheaRib cage
Bronchus
Mediastinum
Lung
Diaphragm
Section through the head
Nasal cavity
Palate
TonguePharynx
Hyoid bone
Epiglottis
Larynx
Esophagus
Teeth
Vocal cords
The Miles Kelly Art library, Wellcome Images
The mucous lining• The nasal cavity and upper airways
have a mucous lining.
• The epithelial lining contains goblet cells which secrete a clear, sticky mucus.
• The function of mucus is to trap dirt particles and microbes before they enter the lungs.
The nose (nasal cavity)• Air enters and leaves the body
through the nose.
• Here it is cleaned, warmed and moistened before entering the body.
• The nasal secretions contain an anti-bacterial enzyme – lysozyme.
A section through the nasal cavity
The Miles Kelly Art library, Wellcome Images
Nostril
Hard palateSoft palate
Sinus
NASAL CAVITY
The larynx (Adam’s apple or voice box)
• The larynx is a box-like structure constructed from nine cartilages and is the entrance to the trachea and lungs.
• The larynx houses the vocal folds or vocal cords.
• The entrance to the larynx is protected by the epiglottis.
Gray’s Anatomy
The bronchial tree
Larynx
Trachea
Bronchus
Bronchiole
The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989)
Trachea & bronchi
• The trachea & bronchi are reinforced with C-shaped rings of cartilage (these prevent the tubes collapsing during inhalation).
The bronchi
The Miles Kelly Art library, Wellcome Images
Mucous lining
Muscular wall
Cartilage rings
• The upper airways are lined with a ciliated mucous membrane–The sticky mucus traps dirt &
microbes–The cilia sweep the dirty mucus
up the trachea and into the throat.
The ciliated lining tissue
Mucus-secreting goblet cells
Cilia
G. Meyer, ANHB-UWA,
EM of ciliated epithelium & goblet cells
D Gregory & D Marshall, Wellcome Images
Alveoli
• The brochioles terminate in microscopic clusters of air sacs – the alveoli.
• Gas exchange takes place in the alveoli.
AlveoliG. Meyer, ANHB-UWA
The alveoli (air sacs)
The Miles Kelly Art library, Wellcome Images
Section through a lung showing alveoli and blood supply
M I Walker, Wellcome Images
The respiratory system
Gas exchange
Exchange surfaces
• Like all exchange surfaces, the alveoli:
–are very thin
–have a large surface area
–are moist
–have a rich blood supply
Breathing
• Breathing (sometimes referred to as ventilation) is the process of moving air into and out of the lungs.
• The purpose of breathing is to exchange oxygen and carbon dioxide between the lungs and the air .
Boyle's law
• Boyle's law states that: for a fixed amount of gas kept at a fixed temperature, pressure (P) and volume (V) are inversely proportional (while one increases, the other decreases).
• This can be stated mathematically as:PV = k
• where: P is the pressure, V is the volume & k is a constant value representative of the pressure and volume of the system.
Respiration
• Respiration is the transport of oxygen from the air to the tissues and the transport of carbon dioxide in the opposite direction.
[not to be confused with the process of cellular respiration discussed earlier]
External respiration and Internal respiration
• External respiration is the movement of O2 and CO2 between the lungs and the bloodstream.
• Internal respiration is the exchange of O2 and CO2 between the blood and the tissues.
External respiration
Partial pressure (mmHg)
Alveolar air Deoxygenated blood
Oxygenated blood
Oxygen 100 40 100
Carbon Dioxide
40 44 40
Breathing maintains the correct concentration of gases in the lungs
Concentration gradient
Breathing – inhaling(remember P1V1 = P2V2)
Anatomical changes
V P1 P1:P2 Result
• Rib cage raised• Diaphragm flattens
Increases Decreases P1<P2 Air drawn into lungs
V = volume of thoracic cavity
P1 = pressure in thoracic cavity
P2 = air pressure
Thoracic volume
Rib cage relaxes Diaphragm domed
Rib cage raised Diaphragm flattens
P1V1 = P2V2
A bicycle pump works in much the same way
as the lungs
The lungs work in much the same way as a bicycle pump
If you increase the volume of the chamber air is sucked in
If you decrease the volume of the chamber air is forced out
Breathing – exhaling(remember P1V1 = P2V2)
Anatomical changes
V P1 P1:P2 Result
• Rib cage relaxes• Diaphragm domed
Decreases Increases P1>P2 Air forced out of lungs
V = volume of thoracic cavity
P1 = pressure in thoracic cavity
P2 = air pressure
The Miles Kelly Art library, Wellcome Images
INHALE EXHALE
Ribcage raised
Ribcage lowered
Diaphragm domed
Diaphragm flattened
Thoracic volume increasedThoracic pressure < air pressure
Thoracic volume decreasedThoracic pressure > air pressure
Why breathe?Fresh air passing through the lungs delivers oxygen to the red blood cells. At the same time, waste carbon dioxide is removed from the blood. This can only occur if fresh air is constantly circulating through the lungs.
Wellcome Photo Library
Carbon dioxide
Oxygen
Oxygen transport
• Oxygen combines with haemoglobin in RBCs to form oxyhaemoglobin.
Carbon dioxide transport• Most CO2 is transported in the plasma as
dissolved bicarbonate ions. -
Oxygen saturation
Diseased lung tissue
Photo by Pöllö
CDC
A. healthy lung tissue
B. Smoker’s lung
C. Emphysema
A
B
C
Study Guide
Read:• Our Human Species
Chapter 11, sections 1-2, 4-6
Complete:• Workbook
Topic 9, Respiratory system