Ch. Eleven: Respiratory System Flashcards
1
Q
External Respiration
A
4 steps:
1. Ventilation: movement of air into and out of lungs
2. O2 and CO2 exchange between air in alveoli and blood within the pulmonary capillaries
3 & 4. blood transports O2 and CO2 exchanged between tissues and blood by diffusion across systemic capillaries
2
Q
Internal Respiration
A
- cellular respiration: metabolic processes within mitochondria
- respiratory quotient (RQ): ratio of CO2 produced to O2 consumes; varies depending on foodstuff consumed
3
Q
Nonresp. Functions of Resp. System
A
- route for water loss and heat elimination
- enhances venous return
- helps maintain normal acid-base balance
- enables speech, singing, ect
- defends against inhaled foreign matte; cilia, mucous, macrophages
- removes, modifies, activates, or inactivates various materials passing through the pulmonary circulation
- nose serves as the organ of smell
4
Q
Lungs
A
- occupy most of the thoracic cavity
- 2 lungs divided into several lobes, each supplied by one of the bronchi
- highly branched airways, the alveoli, the pulmonary blood vessels, and large quantities of elastic connective tissue
5
Q
Respiratory Airways
A
- tubes that carry air between the atmosphere and the air sacs
- nasal passages
- pharynx- trachea
- larynx
- right and left bronchi
6
Q
Bronchoiles
A
- no cartilage to hold them open
- walls contain smooth muscle innervated by ANS
- sensitive to certain hormones and local chemicals
- alveoli are clustered at ends of terminal bronchioles
7
Q
Conducting Zone
A
- trachea and larger bronchi
- fairly rigid, nonmuscular tubes
- rings of cartilage prevent collapse
8
Q
Respiratory Zone
A
- bronchioles
9
Q
Alveoli
A
- thin-walled inflatable sacs; gas exchange and large surface area
- walls consist of a single layer of cells: TYPE 1
- pulmonary capillaries encircle each alveolus
- TYPE 2 alveolar ells secrete surfactant
- alveolar macrophages guard lumen
- pores of Kohn permit airflow between adjacent alveoli (collateral ventilation)
10
Q
Chest Wall
A
- outer chest wall (thorax)
- formed by 12 pairs of ribs
- rib cage protects the lungs and heart
- contains the muscles involved in generating the pressure that cause airflow
11
Q
Main Inspiratory Muscles
A
- diaphragm: dome-shaped sheet of skeletal muscle separates thoracic cavity from abdominal cavity, innervated by phrenic nerve
- external intercostal muscles: innervated by intercostal nerve
12
Q
Lungs
A
- pleural sac (serosal membrane): double-walled, closed sac
- pleural cavity
- intrapleural fluid: secreted by surfaces of the pleura, lubricated pleural surfaces
13
Q
Resp. Mechanics
A
- interrelationships among pressures inside and outside the lungs are important in ventilation
- 4 different pressure considerations important in ventilation:
1. atmospheric pressure
2. (intra)Alveloar pressure
3. (Intra)pleural pressure
4. Transpulmonary pressure: inside pressure-outside pressure
14
Q
Pressures Important in Ventilation
A
- resp. pressure are always relative to atmospheric pressure!
- measured in mmHg, cmH2O, atmopsheres (atm)
- sea level= 760mmHg or 1 atm or 1034 cmH2O
- higher altitudes = less pressure
15
Q
Transumral Pressure Gradient
A
- lungs are highly distensible and have elastic recoil
- thoracic wall is more rigid, but recoils outward
- transmural pressure: inside pressure-outside pressure
- keep lung and chest wall together
- pleural sac always has subatmospheric pressure
16
Q
Source of the Lungs Elastic Recoil
A
- how readily the lungs rebound after having been stretched
- responsible for lungs returning to their preinspiratory volume when inspiratory muscles relax at end of inspiration
- depends on 2 factors:
1. highly elastic connective tissue in the lungs; “stretchability”
2. alveolar surface tension: - thin liquid film lines each alveolus, reduces tendency of alveoli to recoil, helps maintain lung stability (newborn resp. distress syndrom)
17
Q
Alveolar Surface Tension
A
- water lines alveoli creates surface tension
- resists alveoli expansion- less compliant
- tends to shrink alveoli- recoil
- lungs would collapse if only water lined alveoli
- smaller the alveoli, greater the surface tension= collapse
18
Q
Pulmonary Surfactant
A
- pulmonary surfactant reduces surface tension
- reduces cohesive force between water molecules
- deep breathing increases secretion by stretching type 2 cells
- complex mixture of phosolipids and proteins secreted by type 2 alveolar cells
- disperses between the water molecules in the fluid lining the alveoli and lowers alveolar surface tension
- 2 important benefits:
1. reduces work of the lungs
2. reduces recoil pressure of smaller alveoli more than larger alveoli
19
Q
Lack of Pulmonary Surfactant
A
- huge problem for babies, especially those born prematurely
- infant resp. distress syndrome (IRDS) or resp. distress syndrome of the newborn (RNSD)
- too little surfactant allows the alveoli to collapse and then they have to re-inflate every time (huge energy drain)
20
Q
Pulmonary Surfactant (in uetero)
A
- normally surfactant is not made until the last two months in utero
- give mother steroid to help stimulate production
- but in most emergency births this is not possible so the baby is put on a ventilator
- artificial surfactant can help
21
Q
Alveolar Interdependence
A
- contributes to alveolar stability
- alveoli connected to each other by connective tissue
- if an alveolus starts to collapse, neighbouring alveoli resist by recoiling
- exert expanding force on the collapsing alveolus
- “tug of war” between neighbouring alveoli
22
Q
Pneumothorax
A
- demonstrates the elastic recoil of the lungs
- thoracic wall springs outward
- importance of pleural pressure to keep lungs inflated
- abnormal condition of air entering the pleural space:
- both pleural and alveolar pressure no equal atm, so pressure gradient no longer exists across lung wall or chest wall
- with no opposing neg. pleural pressure to keep inflated, lung collapses to its unstretched size
23
Q
Boyle’s Law
A
- pressure exerted by a gas varies inversely with the volume of gas
- P1V1= P2V2
- during respiration the volume of lungs is made to change
- drive air flow into or out of the lungs
24
Q
Changes in Alveolar Pressure
A
- produce flow of air into and out of lungs
- if alveolar pressure is less than atmospheric pressure= air enters the lungs
25
Q
How are changes in lung dimensions brought about?
A
- by altering lung volume:
pressure changes in the lungs and air flow is generate - respiratory muscle activity change volume of thoracic cavity
26
Q
Inspiratory Muscles
A
- diaphragm:
major inspiratory muscles; 75% of thoracic volume change at rest - external intercostal muscle
27
Q
Onset of Inspiration
A
- expansion during inspiration decreases the intra-pleural pressure
- lungs are drawn into this area of lower pressure
- lungs expand
- this increase in volume lowers the intra-alveolar pressure to a level below atmospheric pressure (Boyle’s Law)
- air enters the lungs
28
Q
Onset of Expiration
A
- relaxation of diaphragm and muscles of chest wall, plus the elastic recoil of the alveoli, decrease the size of the chest cavity
- inter-pleural pressure increases and lungs are compressed
- intra-alveolar pressure increases as air molecules are in smaller volume
- forced expiration can occur by contraction of expiratory muscles: abdominal wall muscles and internal intercostal muscles
29
Q
Air Flow and Airway Resistance
A
- air flow dependent on pressure differences and airway resistance
*remember blood flow regulation!
F= P/R - flow is proportional to the pressure difference between two points and inversely proportional to the resistance
30
Q
ANS Influence on Resistance
A
- primary determinant of resistance to airflow is radius of conducting airway
- ANS controls contraction of smooth muscle in walls of bronchioles
- both branches of ANS act on airway smooth muscle:
1. SNS causes bronchodilation: NE and Epinephrine (more important)
2. ONS causes bronchoconstriction: ACh - other neural inputs
31
Q
Factors Affecrting Airway Resistance
A
bronchoconstriction: allergy-induced spasm and histamine; physical blockage of airways; neural control and local chemical control (decrease CO2)
bronchodilation: neural control, hormonal control and local chemical control (increase in CO2)
32
Q
Under Healthy Conditions…
A
- airway resistance is much less than in cardiovascular system under healthy conditions
- but in disease states the narrow airways: flow can be severely restricted OR work harder to breathe
33
Q
Chronic Pulmonary Disease
A
- abnormally increases airway resistance
- expiration is more difficult than inspiration
- diseases affecting airway resistance:
- chronic bronchitis, emphysema, and asthma
