Respiratory physiology Flashcards
What is the respiratory tract
The respiratory tract is the path of air from the nose to the lungs
Its structures include; nasal cavity, pharynx, larynx, trachea, primary bronchi and lungs
What are the divisions of the respiratory tract (divided structurally)
Upper and Lower
What structures are of the upper respiratory tract
Structures above the vocal cords:
👉 Nose
👉 Nasal passages
👉 Paranasal sinuses
👉 Larynx
👉 Pharynx
the respiratory system is composed of 2 parts :
a gas exchanging organ
ii) a pump that ventilates (process of gas exchange between the lungs and the environment, includes both inspiration and expiration) the lungs. This pump consists of;
* Chest wall
* Respiratory muscles (which increase or decrease size of the thoracic cavity)
* Brain areas that control these muscles
* Tracts and nerves which connect the brain to the muscles
what are the components of the ‘pump’ of the respiratory system
- Chest wall
- Respiratory muscles (which increase or decrease size of the thoracic cavity)
- Brain areas that control these muscles
- Tracts and nerves which connect the brain to the muscles
a normal person breathes how many times a minute
12-15
what is the volume of air breathed per minute
500mL of air/breath ie 6-8L/min
how much O2 enter the body/ min
250mL
how much CO2 is excreted from the body/ min
200mL
what structures are of the lower respiratory tract
portion of larynx below the vocal cord:
-trachea,
-bronchi-primary, secondary & tertiary, and
-bronchioles.
-Lungs can be included; (respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli)
functionally what are the divisions of the respiratory system
Conducting zone and Respiratory zone (transporting gases vs exchanging gases)
generation 0
Trachea
generation 1-2
Bronchi (Primary {2}, secondary, tertiary)
generation 3-4
bronchiole
generation 5-16
Terminal bronchioles
generation 17-19
respiratory bronchioles
generation 20-22
alveolar ducts
generation 23
alveolar sacs
what are the significance of the multiple divisions of the respiratory tree
-They greatly increase the cross sectional surface area of the respiratory tract from about 2.5cm2 in the trachea to 11,800cm2 in the alveoli
-They reduce the velocity of airflow in the small airways. This helps prevent the entry of large particles into the lungs.
what is the conducting zone
Includes the upper airways from the nose and mouth to the terminal airways (terminal bronchioles). Serve as conduit for the passage of air, but do not function in gas exchange
Structures in the conducting zone undergo an irregular branching for 16 generations, each subsequent generation of airway increasing the total cross-sectional area of the conducting zone. They begin as a relatively narrow passage way, the larynx having the smallest cross-sectional area
what are the structures in the conducting zone
-Upper airways (nose, mouth, pharynx and larynx)
-Trachea (0)
-Left & right bronchi (primary bronchus-singular; 1-2)
Secondary bronchi (1-2)
Tertiary bronchi/segmental bronchi (1-2)
-Bronchioles (3-4)
-Terminal bronchioles (5-16
what is the blood supply to conducting zone
bronchial arteries
What are the functions of the conducting zone
-conditioning of air
-removal of foreign materials
-reaction of foreign materials
explain the conditioning of air function of the conducting zone
inspired air is adjusted to body temperature and saturated with water vapour by the time it reaches the trachea during nasal breathing
explain the conditioning of air function of the conducting zone
inspired air is adjusted to body temperature and saturated with water vapour by the time it reaches the trachea during nasal breathing
explain the removal of foreign materials function of the conducting zone
particulate matter in inspired air is removed by several mechanisms:
-Filtration: as inspired gas passes through the nose, nasal vibrissae (coarse hairs) filters out particles that are larger than 50µ in diameter.
-Impaction: by impaction on the walls of the upper airways (the momentum of these particles cause them to stick to the mucous lining of the airways), particles that are 2-50µm in diameter are removed from inspired gas
-Sedimentation: particles that are 0.01-2µm are largely deposited in the small airways (where flow velocity is very low) and alveoli because of the effect of gravity
-Diffusion: inflammation develops and thus the activation of macrophages when particles less than 0.01µm reach the walls of the terminal airways and alveoli by diffusion.
how does filtration remove foreign particles from the conducting zone
as inspired gas passes through the nose, nasal vibrissae (coarse hairs) filters out particles that are larger than 50µ in diameter.
how does impaction remove particles from the conducting zone
by impaction on the walls of the upper airways (the momentum of these particles cause them to stick to the mucous lining of the airways), particles that are 2-50µm in diameter are removed from inspired gas
how does sedimentation remove particles from the conducting zone
particles that are 0.01-2µm are largely deposited in the small airways (where flow velocity is very low) and alveoli because of the effect of gravity
how does diffusion remove particles from the conducting zone
inflammation develops and thus the activation of macrophages when particles less than 0.01µm reach the walls of the terminal airways and alveoli by diffusion.
explain the ‘reaction of foreign materials’ function of the conducting zone
-Irritant receptors are located in the large bronchi, they are stimulated by foreign materials
-This leads to reflex bronchoconstriction, cough, and increase secretion of mucous
-Foreign particles and vapour which reach the alveolar surface leads to the presence of increased alveolar macrophages which in turn releases proteolytic enzymes into the lung tissue (proteolytic enzymes are also called proteinase: they break long chain of protein molecules into shorter fragments-peptides-and eventually into amino acids).
draw a diagram of the divisions of the respiratory system
check the book
what are the divisions of the the respiratory zone of the respiratory system
Respiratory bronchiole (17-19)
Alveolar ducts (20-22)
Alveolar sac/alveoli (23)
what is the blood supply of the respiratory zone
branches of pulmonary artery
what is the function of the respiratory zone
Primarily in gas exchange across the respiratory membrane (ie between alveolar gas and pulmonary capillary blood, by the process of diffusion).
what are some non-respiratory functions of the respiratory tract
-Olfaction
-Vocalization
-Prevention of foreign particles entering the lungs: By filtration, macrophages, cough reflex, sneeze reflex.
-Immunity: leucocytes, macrophages, lung defensins, lung cathelidicins, mast cells, dendritic cells, Natural killer cells.
-Maintainance of water balance by expiration
-regulation of body temperature: by expiration
-regulation of acid-base balance
-anticoagulant: mast cells secrete heparin
-secretion of angiotensin converting enzyme
-secretion of hormones: serotonin, prostaglandins, acetylcholine
what is the respiratory tree
Also called the tracheobronchial tree. It refers to the branching structure of airways supplying air to the lungs, and includes:
Trachea
Main bronchus
Lobar bronchus
Segmental bronchus
Conducting bronchiole
Terminal bronchiole
Respiratory bronchiole
Alveolar duct
Alveolar sac
alveolus
what is the difference(s) between the respiratory tract and respiratory tree
- Location: The respiratory tract extends from the nose/mouth down to the lungs, while the respiratory tree is located within the lungs.
- Function: The respiratory tract is responsible for conducting air into and out of the lungs, while the respiratory tree is responsible for distributing air within the lungs and facilitating gas exchange.
- Structure: The respiratory tract includes several structures such as the nasal cavity, pharynx, larynx, trachea, bronchi and bronchioles. The respiratory tree is a network of progressively smaller tubes, starting with the main bronchi and branching out into smaller bronchioles.
- Size: The respiratory tract is generally larger in diameter than the respiratory tree, which consists of progressively smaller tubes as they branch out.
- Composition: The respiratory tract is lined with a variety of tissues including mucous membranes, cartilage, and smooth muscle. The respiratory tree is composed of smooth muscle, elastic fibers, and a thin layer of epithelial cells.
- Cross sectional area: The respiratory tract has a smaller cross sectional area than the respiratory tree. (2.5cm2 < 11800cm2)
the epithelial cell of the respiratory tract line what
The trachea and bronchus
the mesenchymal cells of the respiratory tract line what
The lungs
out of the 13 cells of the lung, how many are epithelial, how many are mesenchymal
11 are epithelial cells, and 2 are mesenchymal cells
whats the distrubution of the goblet cells in the respiratory tract
are abundant in the upper RT, but fewer down, and absent in the bronchioles.
from the nose to the bronchi, the epithelium is
most of the epithelium is covered in ciliated pseudostratified columnar epithelium
cilia moves mucus towards
the throat
cartilage is present until …
the bronchioles, where it is replaced with smooth muscle
what type of cartilage is in the bronchi (left and right)
hyaline cartilage (the rigid cartilage prevents the bronchi from collapsing and blocking airflow to the lungs)
what epithelium lines the bronchi (left and right)
ciliated pseudostratified epithelium
the right bronchi branches into how many secondary bronchi
3
the left bronchi branches into how many secondary bronchi
2
when do the bronchioles constrict
They constrict to prevent pollution from dust and other pollutants.
when do the bronchioles dilate
during exercise, to let more air in
what are the functions of the lungs?
-Respiration
-Alter the pH of blood by facilitating alterations in the partial pressure of CO2
-Converts angiotensin I to angiotensin II by the action of angiotensinogen-converting enzyme
-Serves as a reservoir of blood in the body, blood volume of the lung is about 9% of the total blood volume of the entire circulatory system.
-Serves as a layer of soft, shock-absorbent protection for the heart which the lungs flank and nearly enclose
what cells line the alveoli
simple squamous epithelium, (TYPE I)
what is the function of septal cells (type II cells)
Septal cells produce alveolar fluid/pulmonary surfactant which coats the inner surface of the alveoli, helps to maintain the elasticity of the lungs, and prevents the thin alveolar walls from collapsing.
-They also help stabilise the alveoli
what is the function of macrophages in the alveoli
Macrophages in the alveoli keep the lungs clean and free of infections by capturing and phagocytizing pathogens and other foreign matter that enter the alveoli along with inhaled air
what is the percentage of oxygen in inspired air
20.95
what is the percentage of CO2 in inspired air
0.04
what is the percentage of nitrogen in inspired air
79.01
what is the percentage of CO2 in the alveoli air
5.5
what is the percentage of O2 in the alveoli air
13.8
what is the percentage of nitrogen in alveoli air
80.7
what is the percentage of oxygen in expired air
16.4
what is the percentage of CO2 in expired air
4.0
what is the percentage of nitrogen in expired air
79.6
what is residual volume
the volume of air left in the respiratory tract after the most forceful expiration. (1200mL)
what is the significance of residual volume
-Prevents collapse of the airways/lungs
-It allows for gas exchange even in periods of low ventilation (such as in sleep)
in normal quiet breathing, what volume of air is drawn in
500mL
Out of the amount of air inhaled in normal quiet breathing, what volume mixes with residual volume
350mL
what air is concerned with the gas exchange
alveoli air
the movement of air, in and out of te lungs is due to…
the air pressure changes within the lungs
what is inspiration
inspiration also called inhalation is the active process of breathing air from the mouth/nose, through the respiratory tract, and into the lungs
what is normal quiet breathing
Normal quiet breathing, also known as resting or tidal breathing, is the process of breathing that occurs during rest or light activity.
During normal quiet breathing, the diaphragm and other muscles involved in respiration contract and relax in a rhythmic pattern to move a small amount of air in and out of the lungs. The volume of air moved in and out with each breath is relatively small, typically around 500 mL, and the frequency of breaths is relatively low, typically around 12-20 breaths per minute.
Normal quiet breathing is sufficient for maintaining normal levels of oxygen and carbon dioxide in the blood during rest or light activity. It is an involuntary process that is controlled by the respiratory center in the brainstem and can be influenced by factors such as
-emotions,
-stress, and
-physical activity.
what is forced breathing?
Forced breathing, also known as hyperpnea, is the process of breathing that occurs when the body’s demand for oxygen increases, such as during exercise or in response to respiratory distress.
During forced breathing, the respiratory muscles work harder and contract more forcefully to move a larger volume of air in and out of the lungs. This increased effort requires more energy and can be achieved through the use of additional muscles (accessory muscles of respiration). Forced breathing can also involve an increase in respiratory rate (breaths per minute) to meet the increased demand for oxygen. Forced breathing is an active process that requires conscious effort and can feel more uncomfortable or difficult than normal quiet breathing.
It is necessary for maintaining adequate levels of oxygen in the body during periods of increased demand (such as in exercise) or respiratory compromise.
what are the primary muscles of inspiration
-Diaphragm
-External intercostal
describe the diaphragm
-A dome-shaped muscle supplied by 2 phrenic nerves
-Its contraction causes an increase in the superior-inferior diameter of the thoracic cavity (contraction of the diaphragm involves its lowering to a more flattened shape; this increases the thoracic volume and thus increases lung volume and thus reduces lung pressure)
-Contraction of the diaphragm accounts for 2/3rd of the air that flows into the lungs in quiet inspiration and 75% of the change in intrathoracic volume during quiet inspiration.
-Contraction of the diaphragm is limited by
-advanced pregnancy,
-obesity, and
-tight abdominal clothing
contraction of the diaphragm is limited by
-advanced pregnancy
-obesity
-overeating
-tight abdominal clothing
describe the external intercostals
This muscle runs obliquely downward and forward from rib to rib
On contraction, it elevates the lower ribs, thus pushing the sternum outward and thus increase the anterior-posterior diameter of the chest
The transverse diameter also increases, but to a lesser degree
This elevating the ribs and expansion of the rib cage also increases the thoracic volume
Contraction of the external intercostal muscle accounts for the remaining 1/3rd of air that fills the lungs during normal quiet breathin
what are the muscles of normal quiet inspiration
-diaphragm
-external intercostal
what are the accessory muscles of respiration
These group of muscles are usually called to play in forced inspiration.
They include;
-Scalene
-Sternocleidomastoid
-Alae Nasi
-Small muscles of the head and neck
-Elevators of the scapula and pectoralis major
-In forced/deep inspiration, these muscles on contraction elevate the ribs in an anteroposterior direction (thus increasing thoracic volume)
-At the same time, their contraction stabilizes the upper rib cage so that the external intercostal muscle becomes more effective
describe the actions of the accessory muscles of inspiration
-In forced/deep inspiration, these muscles on contraction elevate the ribs in an anteroposterior direction (thus increasing thoracic volume).
-At the same time, their contraction stabilizes the upper rib cage so that the external intercostal muscle becomes more effective
why is expiration in normal quiet breathing passive
No muscle which causes reduced intrathoracic volume contract
Normal expiration results from muscle relaxation and elastic recoil of lungs and thoracic cage
In expiration, the reduction in lung volume that results raises the pressure within the alveoli above the atmospheric pressure, this pushes air out of the lungs into the atmosphere
what is expiration sef
expiration also called exhalation is the removal of air, containing the by-products of respiration from the lungs, through the respiratory tract, out of the nose/mouth
what are the muscles of forced expiration
Rectus abdominis muscle
Transversus abdominis muscle
Internal oblique muscle
External oblique muscle
Internal Intercostal Muscle (on contraction, it depresses the rib cage)
explain the action of the muscles of forced expiration
-During forced expiration, these anterior abdominal wall muscles by their contraction force abdominal organs up against the diaphragm thus further reducing the volume in the thorax
-This way, alveolar pressure within the pleural cavities can raise to 20mmHg or 30mmHg above atmospheric pressure
state Boyles law…
The pressure of a given mass of gas is inversely proportional to its volume
state boyles law…
The pressure of a given mass of gas is inversely proportional to its volume
explain the pressure changes in inspiration
-During inspiration, the diaphragm and the external intercostal muscles contract. The diaphragm increases the superior-inferior volume of the thoracic cavity, when it contracts and the external intercostals increases the anterior-posterior volume of the thorax (and also the transverse).
-As the thoracic volume increases, the intrapleural pressure reduces
-Inspiration begins when the alveolar reduces below atmospheric pressure, by 2.5mmHg. This is because the reduction of intrapleural pressure, increases alveolar volume and thus reduces alveolar pressure
-Thus air flows into the lungs, because the alveolar pressure is lower than the atmospheric pressure
explain the pressure changes in inspiration
-During inspiration, the diaphragm and the external intercostal muscles contract. The diaphragm increases the superior-inferior volume of the thoracic cavity, when it contracts and the external intercostals increases the anterior-posterior volume of the thorax (and also the transverse).
-As the thoracic volume increases, the intrapleural pressure reduces
-Inspiration begins when the alveolar reduces below atmospheric pressure, by 2.5mmHg. This is because the reduction of intrapleural pressure, increases alveolar volume and thus reduces alveolar pressure
-Thus air flows into the lungs, because the alveolar pressure is lower than the atmospheric pressure
explain the pressure changes during expiration
-During expiration, the diaphragm and any other muscles involved relax, and the thoracic volume reduces
-The reduction of intrathoracic volume, increases the intrapleural pressure
-As expiration begins, the alveolar pressure is higher than the atmospheric pressure, by 3mmHg. Thus is because the increased intrapleural pressure, reduces the alveolar volume, and thus increases the alveolar pressure.
-Thus air flows out of the lungs because the alveolar pressure is greater than the atmospheric pressure.
what are the differences between normal quiet breathing and forced breathing
- Volume of air: During normal quiet breathing, only a small amount of air is moved in and out of the lungs with each breath, while during forced breathing, a larger volume of air is moved in and out of the lungs.
- Frequency of breaths: During normal quiet breathing, the frequency of breaths is relatively low (typically around 12-20 breaths per minute), while during forced breathing, the frequency of breaths may increase.
- Muscles used: In normal quiet breathing, accessory muscles are not involved. In forced breathing the accessory muscles are involved
- Energy expenditure: Forced breathing requires more energy than normal quiet breathing due to the increased use of muscles.
- Purpose: Normal quiet breathing is sufficient for maintaining normal levels of oxygen and carbon dioxide in the blood during rest or light activity, while forced breathing is necessary during periods of increased demand such as exercise or when respiratory function is compromised due to illness or injury.
- Lung capacity: Forced breathing can utilize a larger portion of lung capacity than normal quiet breathing, which typically only uses about 10% of total lung capacity.
- Airflow: During forced breathing, airflow through the airways increases due to the increased volume of air being moved in and out of the lungs.
- Gas exchange: Forced breathing may result in greater gas exchange due to the increased airflow and volume of air being moved in and out of the lungs.
- Respiratory rate: During forced breathing, respiratory rate may increase to meet the increased demand for oxygen.
- Sensation: Forced breathing can feel more uncomfortable or difficult than normal quiet breathing due to the increased effort required to move air in and out of the lungs.
- In normal quiet breathing, the expiration is passive. In forced breathing, expiration is active
what is work of breathing
The work of breathing refers to the amount of energy required to move air in and out of the lungs during respiration
why is there no work of breathing for expiration
This is because expiration is a passive process that requires no energy (except in forced expiration)
the work on inspiration is divided into:
3 parts:
-compliance
-tissue resistance
-airway resistance
what is compliance?
it is the ability of the lungs to expand against the lungs and chest elastic forces. It is simply the ability of the lungs to expand, according to changes in pressure. In easier terms, compliance shows how easily the lungs expand to accommodate a given volume of air
-Also called elastic work
-It accounts for about 65% of the work of breathing
-Compliance work can be calculated from:
∆V x ∆P/2
{∆V (increase in volume), ∆P (decrease in pressure)}
what are the types of compliance
-static compliance
-dynamic compliance
what is static compliance
Static compliance is the compliance measured under
static conditions, i.e. by measuring pressure and
volume when breathing does not take place. Static compliance is the pressure required to overcome the elastic resistance of respiratory system for a given tidal volume under zero flow (static) condition.
what is dynamic compliance
Dynamic compliance is the compliance measured during
dynamic conditions, i.e. during breathing.
what does dynamic compliance reduction mean
stiff lungs
what is tissue resistance
It is the work required to overcome the viscosity (resistance to a change in form or shape) of the lungs and chest wall structures
Also called viscous resistance, it accounts for about 7% the work of breathing
what is airway resistance
It is the work required to overcome airway resistance during the movement of air into the lungs
It accounts for about 25% of the work of breathing
what is the 4th type of work of breathing
additional work. It is the work required to expand and contract the thoracic cage
what is additional work
It is the work required to expand and contract the thoracic cage
what differentiates compliance, tissue resistance, airway resistance from additional work
The 3 (compliance, tissue resistance, airway resistance) only concern the lungs and NOT the thoracic cage, while the additional work concerns the thoracic cage
energy needed for compliance of the lungs is how many times that of the lung-thorax system
2X.
-The compliance of the total lung-thorax system is only slightly more than half that of the lungs alone
-Thus, almost two times as much energy is required for normal expansion and contraction of the total lung-thorax system as for expansion of the lungs alone
so why is more energy needed for the compliance of the lung-thorax system than the lungs alone
this is because not only do the lungs expand and contract, but the chest wall and other muscles involved in respiration also move to allow air to enter and exit the lungs.
during heavy breathing, the work of breathing is mainly concentrated on what
During heavy breathing when air must flow through the respiratory passage at high velocity, the greater proportion of the work of breathing is used to overcome AIRWAY RESISTANCE
diseases that cause fibrosis concern what work of breathing
compliance and tissue resistance
diseases that obstruct the airways greatly increase which which work of breathing
airway resistance
comment on the work of breathing in expiration
No work is done in expiration (normal quiet breathing), however in deep breathing, or when airway resistance and tissue resistance are great, expiratory work does occur and could even become greater than inspiratory work
-In asthma, airway resistance is increased many fold during expiration but much less so during inspiration
comment on the energy required for work of breathing in both normal quiet breath and forced/heavy breathing
-During normal quiet breathing, only 3 - 4% of total energy expended by the body is required to energize the pulmonary ventilatory process
-But during exercise (esp heavy exercise), the amount of energy required can increase by as much as 50-fold (esp in persons with any degree of increased airway resistance or reduced pulmonary compliance)
what is a major limitation to the exercise a person can perform
the person’s ability to provide enough muscle energy for the respiratory process alone
define compliance in terms of transpulmonary pressure
Compliance can also be defined as the change in lung volume as a function of change in the transpulmonary pressure (difference between Palv and the Pip)
This means, a given Ptp will cause greater or lesser expansion depending on the compliance of the lungs
what is the normal total compliance of both lungs in an adult human
200ml/cmH2O (ie 0.2L/cmH2O)’
This means every time the Transpulmonary pressure increases by 1cm of H2O, the lungs expand by 200ml
what does 200ml/cmH2O (ie 0.2L/cmH2O) mean
This means every time the Ptp increases by 1cm of H2O, the lungs expand by 200ml
how can you measure compliance
Compliance can be determined by using the Oesophageal balloon (clinical method for measuring pleural pressure) which will give the Intrapleural pressure
The oesophageal ballon gives what value of compliance
Intrapleural pressure
draw a compliance graph
check the book man.
what is the volume of functional residual capacities
2.3L or 2300mL
What factors affect compliance
👉Lung Volume; FRC (functional residual capacity, about 2.3L or 2300ml) = ERV + RV is the amount of air that remains in the lungs at the end of normal expiration, FRC affects volume of distribution. Compliance reduces with less lung filling
👉Posture; lung volumes are usually reduced in supine position due to increase in intrathoracic blood volume. Compliance reduces in the supine position due to this reduction in lung volumes
👉Lung diseases; Compliance increases in emphysema (excess air in the lungs, its both obstructive and destructive, and mostly a consequence of long-term smoking) and reduces in fibrosis (which cause loss of elasticity of lung tissue)
👉Thoracic cage disease like Kyphoscoliosis (a musculoskeletal disorder in which there is an abnormal curvature of the spine in both the coronal and sagittal plane, results in under-ventilation of the lungs, and pulmonary hypertension) reduces compliance
👉Alveolar Surface Tension; a very important factor which affects (i.e. it resists distension) the compliance of the lungs is alveolar surface tension
what is functional residual volume
FRC (functional residual capacity, about 2.3L or 2300ml) = ERV + RV is the amount of air that remains in the lungs at the end of normal expiration, FRC affects volume of distribution
state the law of laplace
The law of LaPlace describes this; the pressure created is directly promotional to the surface tension and inversely promotional to the radius of the alveolus
P = 2 x T / R
P (pressure, also known as collapse pressure)
T (surface tension)
r (radius of alveolus)
what is the implication of the law of laplace
the pressure in a smaller alveolus would be greater than that in a larger alveolus if the surface tension is the same in both
comment on surface tension in the lungs
-A very important factor affecting (i.e. it resists distension) the compliance of the lungs is surface tension that is exerted by fluid in the alveoli
-Although the alveoli is relatively dry, it contains a very thin film of fluid
-Surface tension is created because H2O molecules at the surface are attracted more to other H2O molecules than to air
-Because whenever water forms a surface with air, the water molecules on the surface of the water have an extra strong attraction for one another
-As a result, the surface water molecules are pulled tightly together by attractive forces from underneath.
-The surface tension of an alveolus produces a force that is directed inwards, and as a result creates pressure within the alveolus
why is surface tension created in the lungs
H2O molecules at the surface are attracted more to other H2O molecules than to air. Because whenever water forms a surface with air, the water molecules on the surface of the water have an extra strong attraction for one another
another name for the respiratory zone
acinus
functions of surfactant
-Reduction of surface tension; thus increasing the compliance of the lungs and reducing work of breathing
-Increases the alveolar radius by filling irregularities in the alveolar surface thus reducing the transpulmonary pressure.
This effect increases compliance and reduces the work of breathing
-Surfactant enhances alveoli stability
what is surfactant
Surfactant is a surface active agent (in that when it spreads over the surface of a fluid, it greatly reduces surface tension), produced by the type II pneumocytes. It is a complex mixture of
-phospholipids (dipalmitoylphosphatidylcholine [DPPC], also called dipalmitoyl lecithin),
-protein (surfactant apoprotein)
-ions (calcium ions, e.t.c)
what is the action of surfactant
-They don’t dissolve in the fluid, instead, they spread over its surface because one portion of each phospholipid molecule is hydrophilic and dissolves in the water lining the alveoli
-Whereas the lipid portion of the molecule is hydrophobic and oriented towards the air, forming a lipid hydrophobic surface exposed to the air
-The surface thus formed has between 1/12 to 1/2 the surface tension of a pure water surface
what is the function of surfactant apoprotein and calcium ion in the surfactant
in their absence, the DPPC spreads so slowly over the fluid surface that it cannot function effectively
what is the surface tension unit
dynes/cm
what is the surface tension of water
72
what is the surface tension of normal fluid lining the alveoli (without surfactant)
50
what is the surface tension of the fluid lining the alveoli (with surfactant)
5-30 (increasing as surface increases)
what is the %composition of phosphatidylcholine in surfactant
65
what is mechanics of breathing
It is the sum total of processes that must occur for air to enter the lungs from the atmosphere, and for air to leave the lungs into the atmosphere, as a result of pressure change in lung volume.
%composition of Phosphatidylglycine in surfactant
5
%composition of Other Phospholipids in surfactant
10
%composition of neutral lipids in surfactant
13
%composition of CHO in surfactant
2
%composition of PROTEINS in surfactant
8
What is RDS
-Surfactant does not normally begin to be secreted into the alveoli until between the 6th and 7th month of gestation and in some babies even later than that
-Thus, many premature babies have little or no surfactant in their alveoli, and so the lungs of this babies have extreme collapse tendencies, and this causes their alveoli to collapse
-This condition is called respiratory distress syndrome (RDS)
-It does not occur in all premature babies because the rate of development of the lungs depends on hormonal conditions (esp. thyroxine and hydrocortisone) and genetic factors
-RDS is fatal if not treated immediately with strong measures (properly applied continuous positive pressure breathing)
-Infants with RDS have inadequate gas exchange
what is the treatment for RDS
properly applied continuous positive pressure breathing
why does RDS not occur in all premature infants
It does not occur in all premature babies because the rate of development of the lungs depends on
-hormonal conditions (esp. thyroxine and hydrocortisone) and
-genetic factors
what diseases are related to surfactant
Respiratory distress syndrome
Atelectasis
what is atelectasis
Atelectasis refers to partial or complete collapse of
lungs, (in an entire lobe, or in an entire lung
). When a large portion of lung is collapsed, the
partial pressure of oxygen is reduced in blood, leading
to decreased partial pressure of oxygen, leading to dyspnea (shortness of breath).
causes of atelectasis
- Deficiency or inactivation of surfactant. It causes collapse of lungs due to increased surface tension, which leads to respiratory distress syndrome.
- Obstruction of a bronchus or a bronchiole. In this
condition, the alveoli attached to the bronchus or
bronchiole are collapsed. - Presence of air (pneumothorax), fluid (hydrothorax),
blood (hemothorax) or pus (pyothorax) in the pleural
space.
what is asthma
asthma is the respiratory disease characterized
by difficult breathing with wheezing. Wheezing refers
to whistling type of respiration. It is due to bronchiolar
constriction, caused by contraction of smooth
muscles in bronchioles, leading to obstruction of air
passage. Obstruction is further exaggerated by the
edema of mucus membrane and accumulation of
mucus in the lumen of bronchioles. Carbon dioxide accumulates, resulting in acidosis, dyspnea and cyanosis.
what are the causes of asthma
- Inflammation of air passage: Leukotrienes released
from eosinophils and mast cells during inflammation
cause bronchospasm. - Hypersensitivity of afferent glossopharyngeal
and vagal ending in larynx and afferent trigeminal
endings in nose: Hypersensitivity of these nerve
endings is produced by some allergic substances
like foreign proteins. - Pulmonary edema and congestion of lungs caused
by left ventricular failure: Asthma developed due to
this condition is called cardiac asthma.
in asthma there is a reduction of what
i. Tidal volume
ii. Vital capacity
iii. Forced expiratory volume in 1 second (FEV1)
iv. Alveolar ventilation
v. Partial pressure of oxygen in blood.
what is emphysema
Emphysema is a type of chronic obstructive pulmonary disease (COPD) that affects the lungs. It is characterized by damage to the air sacs (alveoli) in the lungs, which causes them to lose their elasticity and become enlarged. This reduces the surface area available for gas exchange and makes it difficult to breathe.
-Emphysema is most commonly caused by long-term exposure to cigarette smoke or other irritants, and is often associated with chronic bronchitis.
-Symptoms of emphysema include shortness of breath, wheezing, coughing, and chest tightness.
-Treatment may include medications, oxygen therapy, and lifestyle changes such as quitting smoking.
what are the causes of emphysema
- Cigarette smoking
- Exposure to oxidant gases
- Untreated bronchitis
What are the symptoms of emphysema
shortness of breath,
wheezing,
coughing, and
chest tightness.
What is the treatment for emphysema
medications,
oxygen therapy, and
lifestyle changes such as quitting smoking.
What is spirometry
It’s one of the primary Pulmonary Function Tests (PFT) used to check the health of the lungs and respiratory passageways.
What is a spirometer
When a spirometry test is performed, the subject breathes through a mechanical or electronic airflow sensor called a spirometer.
What are the types of spirometer
Mechanical
Electrical
Recording of a subjects airflow
Spirogram
The readings of a spirogram are compared against
normal values for an
-individual’s height,
-weight,
-sex, and
-age.
A reduced rate of airflow in a spirogram indicates
blockage in one or more of the airways (an obstructive disorder),
Reduced volume in a spirogram indicates what
inability to fully expand the lungs (a restrictive disorder).
The amount of air in the lungs is divided into _ and _
4 volumes and 4 capacities
The 4 lung volumes added together gives what
it equals the maximum volume to which the lungs can be expanded
What is tidal volume
the amount of air that can be inhaled and exhaled during one normal (quiet) breathing cycle (about 500 ml for men & women).
What is the value of tidal volume
500mL in both male and female
What lung volume is synonymous with forced inspiration
Inspiratory reserve volume
What lung volume is synonymous with forced expiration
Expiratory reserve volume
What is inspiratory reserve volume
the amount of air that can be forcibly inhaled beyond a tidal inhalation (about 3,000 ml for men & 2,000 ml for women).
What is the value of inspiratory reserve volume
about 3,000 ml for men &
2,000 ml for women
What is the value of expiratory reserve volume
the amount of air that can be forcibly exhaled beyond a tidal exhalation (about 1100 ml for men & 700 ml for women).
What is the value of expiratory reserve volume
About 1100 ml for men &
700 ml for women
Inspiratory reserve volume of males
3000mL
Expiratory reserve volume of females
700mL
Inspiratory reserve volume of females
2000mL
Expiratory reserve volume of males
1100mL
What is residual volume
theamount of air remaining in the lungs after an ERV (most forced expiration) (= about 1,200 ml in men & women).
What is the value of residual volume in male and female
1200mL
The older you get,…
the harder it is for your lungs to breathe in and hold air.
What is the implication of breathing less oxygen
our body and cells also receive less oxygen, forcing our heart to work harder to pump oxygen throughout the body
What forms a respiratory lung capacity
2 or more respiratory volumes added together
What 2 lung volumes give inspiratory capacity
Tidal volume (Vt) + Inspiratory reserve volume (IRV)
What is the value of inspiratory capacity
3500mL
What is inspiratory capacity
About 3,500 mL, is the amount of air a person can breath in, beginning at the normal expiratory level and distending(outwardly expanding) the lungs to the maximum amount
What 2 lung volumes form functional reserve capacity
Expiratory reserve volume (ERV) + Reserve volume (RV)
What is the value of functional reserve capacity
2300mL
What is functional reserve capacity
About 2,300 mL, is the amount of air remaining in the lungs after a normal expiration
What lung volumes form vital capacity
Tidal volume(Vt) + Inspiratory reserve volume (IRV) + Expiratory reserve volume (ERV)
What is the value of vital capacity
4600mL
What is vital capacity
-About 4,600 mL, is the total amount of air a person can expel from the lungs after first filling the lungs to their maximum extent
-It is approximately 80 percent of TLC.
-The value varies according to age and body size.
Vital capacity varies according to
-age
-body size
Vital capacity is what % of total lung capacity
80%
What lung volumes constitute total lung capacity
Residual volume (RV) + Vital capacity (VC).
OR
Tidal volume (Vt) + Inspiratory reserve volume (IRV) + Expiratory reserve volume (ERV) + Residual volume (RV)
What is the value of total lung capacity
5800mL
What is the physiological distribution of lung volumes and capacities
-All pulmonary volumes and capacities are usually about 20 to 25% less in women than in men, and
- they are greater in large and athletic people than in small and asthenic people
Draw a graph to show the lung volumes and capacities
Check the book.
What is structural dead space
Some air breathed doesn’t reach the gas exchange areas, but fills respiratory passages where gas exchange don’t occur (nose, pharynx, trachea)
What is the functional dead space
On occasion, some of the alveoli are nonfunctional or only partially functional because of absent or poor blood flow (poor perfusion) through the adjacent pulmonary capillaries.
What air is expired first in expiration
Dead space
What is anatomical Dead space
-Anatomical dead space is the total volume of the conducting airways from the nose or mouth down to the terminal bronchioles, its about 150ml on the average.
-It can also be described as the portion of the tidal volume that does not take part in gas exchange
What is the volume of anatomical Dead space
150mL
What is physiological Dead space
-Physiological dead space is when alveolar dead space is included in the total measurement of dead space
-Physiological dead space includes the anatomical dead space and alveoli which are well ventilated but poorly perfused, and are thus less efficient at exchanging gas with the blood
Comment on the dead space in normal people
Normally (in healthy individuals), anatomical and physiological dead spaces are nearly equal because all the alveoli are functional in the normal lung
Comment on dead space as a disorder
But in a person with partially functional or nonfunctional alveoli in some parts of the lungs, the physiological dead space may be as much as 10 times the volume of the anatomical dead space (1L – 2L).
Why is physiological Dead space more useful in a clinical setting
in a person with partially functional or nonfunctional alveoli in some parts of the lungs, the physiological dead space may be as much as 10 times the volume of the anatomical dead space (1L – 2L).
What is the implication of high rates of air exchange in functional alveoli
High rates of air exchange in functioning alveoli –> that is higher alveolar ventilation, would bring in fresh oxygen-rich air and efflux carbon dioxide-laden air rapidly; –> consequently, the concentration of oxygen would be higher and the –> concentration of carbon dioxide would be lower within alveoli.
What is the implication of low rates of gas exchange
low rates of air exchange in functioning alveoli, —> that is lower alveolar ventilation, would bring in fresh oxygen-rich air and efflux carbon-dioxide-laden air slowly; —> consequently, the concentration of oxygen would be lower and —> the concentration of carbon dioxide would be higher within the alveolus.
What is alveolar ventilation per minute (Va)
- The total volume of new air that enters the alveoli (tidal volume) and adjacent gas exchange areas each minute.
-It equals the respiratory rate times the amount of new air that enters these areas per minute
What is the formula for alveolar ventilation per minute
VA = Freq x (VT – VD)
VA (volume of alveolar ventilation per minute)
VT (tidal volume)
VD (physiological dead space volume)
Freq (frequency of respiration per minute ie respiratory rate)
VA = 12 x (500 – 150)
= 4200ml/min
What is the value of alveolar ventilation per minute
4200ml/min
A major factor that determines the concentration of oxygen and carbon dioxide in the alveoli is…
alveolar ventilation
