Pulmonary Ventilation Flashcards
lungs can be contracted or expanded in two ways which are
(1) by downward and upward movement of the diaphragm to lengthen or shorten the chest cavity, and (2)
by elevation and depression of the ribs to increase and
decrease the anteroposterior diameter of the chest cavity
quite breathing is accomplished by
movement of diaphragm
during inspiration diaphragm moves?
pulls the lungs downwards
during expiration the diaphragm?
, the diaphragm simply relaxes, and the
elastic recoil of the lungs, chest wall, and abdominal structures compresses the lungs and expels the air
during inspiration the rib cage moves?
forwards and upwards away from the sternum ( increasing the anteroposterior thickness of chest by 20%)
the muscles that elevate
muscles of inspiration (opposite are muscles of expiration)
The most important muscles that raise the rib cage
are
external intercostals, but others that help are the
(1) sternocleidomastoid muscles, which lift upward on the
sternum; (2) anterior serrati, which lift many of the ribs;
and (3) scaleni, which lift the first two ribs
The muscles that pull the rib cage downward during
expiration are mainly
(1) the abdominal recti, which have
the powerful effect of pulling downward on the lower ribs
at the same time that they and other abdominal muscles
also compress the abdominal contents upward against the
diaphragm, and (2) the internal intercostals
tell the contraction and relaxation of intercoastal muscles and external coastal muscles during inspiration
external intercoastal muscles contract
inter intercoastal muscles relax
ribs move forward (elevate)
pleural pressure
Pleural pressure is the pressure of the fluid in the thin
space between the lung pleura and the chest wall pleura.
The normal
pleural pressure at the beginning of inspiration is
-5 cm of h2o
During normal inspiration, expansion of the chest cage
pulls outward on the lungs with greater force and creates
more negative pressure, to an average of abou
-7 cm of h20
whne the glottis is open what is the pressure inside the lungs?
the pressures in all parts of the
respiratory tree, all the way to the alveoli, are equal to
atmospheric pressure, which is considered to be zero reference pressure in the airways—that is, 0 centimeters
of water pressure.
the cause inspiration the pressure falls inside the alveoli to
-1 cm of h20 (makes 0.5 liter of o2 to flow inwards into the lungs)
transpulmonary pressure
transpulmonary pressure is the pressure difference between that in the alveoli and that on the outer surfaces of the lungs (pleural pressure), and it is a measure
of the elastic forces in the lungs that tend to collapse the lungs at each instant of respiration, called the recoil pressure.
what is lung compliance
a measure of the lung expandability
It refers to the ability of the lungs to stretch and expand
The total compliance of both lungs together
200 milliliters of air
per centimeter of water transpulmonary pressure.
The characteristics of the compliance diagram are
determined by the elastic forces of the lungs. These forces
can be divided into two parts:
- elastic forces of lung tissue
2) elastic forces caused by surface tension of the
fluid that lines the inside walls of the alveoli and other lung
air spaces.
if the lungs are filled with saline what happes
there is no interaction between the air and the alveolar fluid so there is no surface tension present
surface tension elastic force
the nect effect is to cause an elastic contractile force of the entire lung
function of surfactant
reduces the surface tension of water molecules
It is
secreted
type II alveolar epithelial cells,
most important component of surfactant
phospholipid dipalmitoyl phosphatidylcholine,
surfactant apoproteins, and calcium ions.
dipalmitoyl phosphatidylcholine,
surfactant apoproteins works how
They perform this function by not dissolving uniformly
in the fluid lining the alveolar surface. Instead, part of the
molecule dissolves while the remainder spreads over the
surface of the water in the alveol
