18. anatomy of ventilation

Question 1

what is pulmonary ventilation (breathing)

Answer 1

the physical movement of air into and out of the respiratory tract

Question 2

what is the function of pulmonary ventilation

Answer 2

to ensure a continuous supply of oxygen

to prevent build up of CO2

Question 3

how is pressure made

Answer 3

by gas particles bouncing off each other and walls of containers

Question 4

what is boyles law

Answer 4

the pressure of a given quantity of gas is inversely proportional to its volume

Question 5

how does air flow

Answer 5

from an area of high pressure to an area of low pressure

Question 6

if we pull a plunger back does air move out or into the syringe

Answer 6

pulling plunger back increases the volume so the pressure in syringe decreases so air moves in

Question 7

when will air enter the lungs in inspiration

Answer 7

when the atmospheric pressure Is greater than the intrapulmonary/intra alveolar pressure due to lung volume increasing

Question 8

how can we increase thoracic volume (3)

Answer 8

increasing the
vertical diameter
the anterior posterior diameter
the transverse diameter

Question 9

how can we increase vertical diameter

Answer 9

contraction of the diaphragm

responsible for 75% increase in thoracic capacity

Question 10

how can we increase the anteroposterior and transverse diameters

Answer 10

elevation of the ribs

responsible for 25% of the increase in thoracic capacity

Question 11

why does elevation of the ribs increase A diameter

Answer 11

elevation of the ribs at the sternal end makes them more horizontal and pushes the sternum forward
pump handle movement (pulling handle up)

Question 12

why does elevation of the ribs increase the transverse diameter

Answer 12

many ribs are lowest at their middle and rise at each end like the handle of a bucket.
if the middle of the rib rises it moves away from the midline of the body making the chest wider from left to right

Question 13

what is the role of pleura in ventilation

Answer 13

the surface tension created by the layer of serous fluid between the visceral and parietal pleura means they cant be pulled apart
and so when the thorax increases in the volume the lungs also increase in volume

Question 14

what is the interpleural pressure and how is it generated

Answer 14

pressure within the pleural cavity
is always lower than the atmospheric and intrapulmonary pressure
is created by the elastic recoil of the lungs

Question 15

what is pneumothorax

Answer 15

accumulation of air or gas in the pleural cavity
occurs as a result of disease or injury
loss of negative interpleural pressure causes the lungs to collapse

Question 16

inspiration is an _____ process

Answer 16

ACTIVE

Question 17

what are the muscles of quiet inspiration and what do they do

Answer 17

diaphragm- contracts and flattens, increasing vertical diameter
external intercostals- elevate the ribs and increase AP + transverse diameter

Question 18

what are the muscles of forced inspiration

Answer 18

pectoralis major
pectoralis minor 
scalenes 
serratus anterior 
sternocleidomastoid

Question 19

what do the muscles of forced inspiration do

Answer 19

assist in rib elevation , increase the speed and amount of movement

Question 20

is expiration an active or passive process

Answer 20

it is both
when at rest expiration is passive
but when forced is active

Question 21

quiet expiration

Answer 21

relaxation of the diaphragm and external intercostal muscles

Question 22

muscles of forced expiration

Answer 22

internal and innermost intercostals depress the ribs, reducing the size of the thoracic cavity
abdominal muscles compress the abdomen and force the diaphragm upwards

Question 23

neural control of ventilation

Answer 23

chemoreceptors detect changes in PO2, PCO2 and pH
sends signal through afferent nerve pathways to the respiratory centres in the brain stem
then sends signal down efferent pathways (eg phrenic nerve) to the muscles of ventilation