Lecture Seven: Monday, January 18 , 2010th
A.-M. Lauzon, Ph.D.
Class notes 2010
“Human Physiology” by Widmaier, Raff, Strang
“Respiratory Physiology- the essentials” by West
"The Normal Lung" by Murray
STRUCTURE OF THE LUNGS AND CHEST WALL
A. Function of Respiration
The primary function of respiration is gas exchange. In mammals, gas exchange
occurs in the lungs. During inspiration, air rich in O2 is inhaled in the lungs. During
expiration, CO2 produced during the oxidative processes of the body is exhaled from
the lungs. Both gases are transported by the blood. Therefore, both the
cardiovascular system and the respiratory system are involved with supplying body
cells with O2 and eliminating their waste product, CO2.
B. The respiratory tract
know the anatomy
Notes from pictures:
-Nasal turbinets clean air coming in.
-The lung on the right hand side has 3 lobes, and 2 lobes on the left hand side.
Therefore 3 lobar bronchi on the right side and 2 on the left.
-Diaphragm= main muscle of respiration
-Space between the lungs and the ribcage= the pleural space. Very small and
containts a very small amount of water (no air).
-Visceral vs. Perietal pleura (define)
-Branching in the lungs even continues upwards
-Pleural space feels like a fist punching into a fluid filled balloon.
Air flows through a series of air passages that connect the lungs to the nose and
mouth. Inhaled air passes over a complex series of surfaces when it goes through
the nose: the nasal septum and the nasal turbinates. These surfaces clean the air of
big dust particles. see picture in slides
From the nose, warmed and moistened air flows through the common passages for
air and food, the pharynx, and then continues through the larynx. Air finally reaches
the periphery of the lungs via the trachea and bronchi.
The lungs and the airways share the chest cavity with the heart, the great vessels,
and the esophagus. The airways consist of a series of tubes that branch and become
narrower, shorter and more numerous as they penetrate into the lungs. The trachea
divides into 2 main bronchi, each of which divides into lobar and segmental bronchi.
The right main bronchus has 3 lobar bronchi (the right lung has 3 lobes), while the
left main bronchus divides into only 2 bronchi (the left lung has only 2 lobes). The
segmental bronchi divide further into smaller branches. The smallest airways without
alveoli are the terminal bronchioles (figure 2).
see pictures in slides
Pleura and pleural surfaces Pleura: Thin cellular sheet attached to the thoracic cage interior (parietal pleura)
and, folding back upon itself, attached to the lung surface (visceral pleura; forms two
enclosed pleural sacs in thoracic cage (“Human Physiology” by Widmaier, Raff,
A way to visualize the apposition of the two pleural surfaces is to put a drop of water
between two glass microscope slides. The two slides can easily slide over each other
but are very difficult to pull apart.
(“Human Physiology” by Widmaier, Raff, Strang)
-Brain sends signal to the chest, makes chest expand. Due to drop of water, lungs
expand as well and inspiration occurs.
The pressure in the pleural space is negative. This will become clearer after the
discussion of pneumothorax (figure 35).
Lungs are just like balloons.
The chest always wants to expand, while the lungs always want to
collapse, therefore pressure in pleural space is negative.
-Hole in chest, air goes in because the pressure inside is less than the pressure
-The chest expands and the lungs collapse.
-Luckily we have 2 pleural spaces (one for each lung) which are not connected to
-Therefore if you get one pneumothorax, you won’t get it on the other side as well.
see pictures in slides
don’t need to know very intricate anatomy
-Bronchi split into bronchioles until you get to the terminal bronchioles.
C. Conducting and Respiratory Zones
The airways are divided into 2 zones: the conducting zone (made up of the
conducting airways) and the respiratory zone (figure 2). The conducting airways
consist of the airways from the mouth and nose openings, all the way down to the
terminal bronchioles. These airways conduct air from the atmosphere to the
respiratory part of the lungs. The conductive airways do not contribute to gas
exchange, and are thus said to compose the anatomical dead space.
->alveoli everywhere in alveolar ducts, in alveolar sacs
The respiratory part of the lungs (the respiratory zone) begins where the terminal
bronchioles divide into respiratory bronchioles, which have some alveoli opening into
their lumena (figure 3). Beyond the respiratory bronchioles are the alveolar ducts
lined with alveoli. The alveolated region of the lungs is the site of gas exchange, and
is called the respiratory zone. Because of such abundant branching of the airways,
the respiratory zone makes up most of the lungs. The smallest physiological unit of
the lungs (distal to the terminal bronchioles) is the acinus (figure 3).
see pictures in slides
D. Functions of the Conducting Airways
The conducting airways have 4 main functions: 1.Defense against bacterial infection and foreign particles: the epithelial lining of the
bronchi has hair-like projections called cilia. The epithelial glands secrete a thick
substance, mucous, which lines the respiratory passages as far down as the
bronchioles. Foreign particles stick to the mucous and the cilia constantly sweep the
mucous up into the pharynx. This is called the mucociliary defense system.
2.Warm and moisten inhaled air.
3.Sound and speech are produced by the movement of air passing over the vocal
4.Regulation of air flow: smooth muscle around the airways may contract or relax to
alter resistance to air flow-> usually negatively.
E. Function of the Respiratory Zone
The respiratory zone is the site of gas exchange between the air in the alveoli and
the blood in the pulmonary capillaries. There are roughly 300 million alveoli in the
human lungs, and each alveolus may be associated with as many as 1000 capillaries.
F. Blood Supply
The lungs have two circulations: the pulmonary circulation (figures 4 & 5),