Respiration Flashcards
What are the lungs and lower respiratory passages contained in?
The thorax
What is the thorax?
the part of the body between the neck and
the abdomen (“the chest”)
What make up the walls of the thorax, laterally, anteriorly, and posteriorly?
Laterally = the ribs and
intercostal muscles
– Anteriorly = sternum (breastbone)
and costal cartilages
– Posteriorly = thoracic part of the
vertebral column (spine)
What is the thoracic cavity? How is it separated from the abdominal cavity?
The space within the thoracic walls. It is separated
from the abdominal cavity by the diaphragm, a large sheet of muscle.
What is in the thoracic cavity?
the lungs, separated by a central compartment
containing the heart, oesophagus, trachea and major blood vessels
How many lobes are in the right vs length lung and why?
Right lung = 3 lobes (superior, middle, inferior)
Left lung = 2 lobes (superior, inferior)
(heart takes up space in the left side of the thorax)
Through which passage does air enter the lungs
Trachea
The trachea divides into 2 main _______
Bronchi
The smallest air passages are called ________
Bronchioles
The bronchioles terminate at _______
Alveoli - tiny air-filled sacs that expand and contract during respiration
What prevents the trachea and bronchial walls from closing?
Rings and plates of cartilage
Does the diameter of the trachea and bronchi change?
No - fixed diameter (i.e. the amount of
air travelling through them can’t
change
What do bronchiole walls consist of?
Circular muscle
Contraction and relaxation of this
circular muscle layer change the
diameter of bronchioles
→ decreases or increases the
amount of air travelling along the
bronchiole
Alveoli are surrounded by a dense network of blood vessels called _______
Capillaries
As blood flows past the thin alveolar walls, ______ diffuses into the blood from the air in the alveoli into the blood (oxygenation) and ________ diffuses out of the blood into the air in the alveoli
- oxygen
- carbon dioxide
What are the lungs immediately surrounded by?
The pleural cavity
What is the pleural calvity
A fluid filled sac surrounding the lungs, lined with a membrane (the pleura).
The lung pushes into the side of the pleural cavity so that the lung is
surrounded by a double layer of pleura (like a fist pushing into a water balloon)
The inner pleural layer is adhered to the _______________
Outer surface of the lungs
The outer pleural layer is adhered to the internal surface of the ________ and superior surface of the ________
- thoracic wall
- diaphragm
What is the function of the pleural fluid?
- Lubrication - minimises friction
between the pleural surfaces as they slide over one another - Adhesion - sticks the pleural
surfaces together via surface tension - like a cup sticking to a wet coaster
Air moves into and out of the lungs in response to ___________
pressure gradients
Gases move from an area of high
pressure to an area of lower
pressure in an attempt to ____________________
equalise pressure differences
At the end of expiration, atmospheric pressure an alveolar pressure are ________
Equal - therefore no movement into or out of the lungs takes place
Inspiration begins with _________ of inspiratory muscles to increase ________________
- contraction
- thoracic volume
Inspiration begins with contraction of inspiratory muscles to increase thoracic volume. This results in expansion of the lungs and _________ in alveolar volume
increase
Increase in alveolar volume creates a decrease in _____________
alveolar pressure
–> alveolar pressure becomes lower than atmospheric pressure, so air flows into the lungs
At the end of inspiration, the thorax and alveoli _____ ___________
stop expanding
At the end of inspiration, when the thorax and alveoli stop expanding, airflow into the lungs causes alveolar pressure to become equal to ___________
atmospheric pressure
During expiration, volume of the thorax decreases as the ___________ relaxes and the thorax and lungs recoil
diaphragm
Relaxation of the diaphragm and recoil of the thorax and lungs causes a decrease in alveolar volume, and _________ in alveolar pressure
increase
–> as alveolar pressure becomes greater than atmospheric pressure, air moves out of the lungs until pressure equalises
Changes in thoracic cavity volume occur due to movements of the __________ and _________
thoracic wall and diaphragm
How do the thoracic wall and diaphragm move during inspiration?
Thoracic wall: Outward (lateral) and upward (elevation)
Diaphragm: Downward
How do the thoracic wall and diaphragm move during expiration?
Thoracic wall: Inward (medial) and downward (depression) movements
Diaphragm: Upward
a. ribs
b. vertebral column
c. costal cartilages
d. intercostal spaces
e. sternum
The shoulder blade is called the _______
scapula
How many ribs are there in total?
12
What is the difference between true ribs, false ribs and floating ribs? How many are there?
True ribs - (pairs 1-7)
False ribs - (pairs 8-10)
Floating ribs - (pairs 11-12)
True ribs: Anterior ends attach directly to sternum via costal
cartilages
False ribs: Anterior ends do not attach directly to the sternum, but
to other costal cartilages
Floating ribs: Do not attach to sternum,
anterior ends are free
What type of joints are the posterior rib joints?
What type of joints are anterior rib joints?
posterior rib joints - Synovial joints
anterior rib joints - Cartilaginous joints
What kind of movement do the posterior rib joints allow?
The arrangement of the posterior rib joints allows the posterior end of the rib to rock up and down against the spine
Movement at the posterior rib joints
produces slight rotation and elevation of the ribs - like the movement of a bucket handle. What effect does this have on the volume of the thoracic cavity
Increases volume of the thoracic cavity
How many layers of intercostal muscles run between adjacent ribs? What are they?
3
External intercostal muscles
Internal intercostal muscle
Innermost intercostal muscle
What are the functions of the external intercostal muscles?
Elevate the ribs
Expand the thoracic cavity
“Ribs up and out”
What are the functions of the internal intercostal muscles?
Depress the ribs
Compress the thoracic cavity
“Ribs down and in”
What 3 structures does the diaphragm attach to?
Inferior edge of the rib cage
Inferior part of the sternum
Lumbar (“lower back”) portion of the vertebral column
How does the diaphragm move when its muscle fibres contract?
Contraction of the diaphragm muscle fibres pulls the diaphragm
down towards the abdominal cavity
How does the diaphragm move when its muscles fibres relax?
Relaxation of the diaphragm muscle fibres allows the diaphragm to rise up towards the thoracic cavity (pushed up by pressure of the organs in the abdominal cavity
What conditions in the body influence respiration rate?
Levels of O2 and CO2
Is quiet inspiration an active or passive process?
Quiet inspiration is an active process, meaning that it requires muscle contraction:
(External intercostal muscles contract
Ø Ribs move upwards and outwards
Ø Sternum lifts upwards
* Diaphragm contracts
Ø Diaphragm moves downwards)
What causes lung volume to increase when the thoracic cavity expands?
As the thoracic wall moves outwards and the diaphragm moves downwards, the adhesion between the inner and outer pleural layers means that the lung is pulled outwards as well
During expansion of the thoracic cavity and lung volume, how does the pressure inside the thorax and lungs change? What is the result of this pressure change?
Pressure inside the
thorax and lungs reduces
Air flows into the lungs down the pressure gradient
Is quiet expiration an active or passive process?
Largely passive:
External intercostal muscles and diaphragm relax (stop contracting)
* Pressure within the abdominal cavity pushes diaphragm back up
* Gravity pulls the ribcage down
* Thoracic cavity reduces in volume
Describe what is meant by ‘elastic recoil’ of the lungs
The lungs are elastic and will spring back to their resting shape after
expansion (= elastic recoil)
Once the external intercostal muscles and diaphragm relax, elastic recoil is unopposed and the lungs contract back to their resting shape
* Adhesion between the pleural layers means that as the lung volume reduces with elastic recoil, the chest wall is pulled inwards
What muscles does forceful inspiration involve contraction of?
- The muscles of quiet inspiration (external intercostal muscles and diaphragm)
PLUS - The accessory muscles of inspiration
* Sternocleidomastoid muscles (left and right)
* Scalene muscles (left and right groups)
* (With some assistance from pectoral (anterior chest) and upper back muscles)
Sternocleidomastoid muscles are involved in forceful inspiration.
What are these muscles attached to, and what is their role in forceful inspiration
Runs from top of sternum
and clavicle, to mastoid
process at base of skull
behind ear
Elevates the sternum
Scalene muscles are involved in forceful inspiration. What are these muscles attached to and what is their role in forceful inspiration?
Run from vertebrae to
upper ribs
Elevate the 1st and 2nd ribs
Which muscles contract during forceful expiration?
Internal intercostal muscles – depress ribs and narrow thoracic cavity
PLUS
2. Abdominal wall muscles
* Rectus abdominis (Lat. rectus ‘straight’) – left and right
* External oblique muscles (oblique = diagonal) – left and right
What do the abdominal wall muscles (rectus abdominis and external oblique muscles) do during forceful expiration?
During forceful expiration, the abdominal wall muscles contract:
* Depress (pull down) the lower ribs, aiding the action of the internal
intercostal muscles
* Forcefully compress the contents of the abdominal cavity, which
pushes the diaphragm upwards
