Respiratory system

PREPARED BY: JEGAN.S. NADAR
THE RESPIRATORY SYSTEM

Copyright 2009, John Wiley & Sons, Inc.
Jegan

RESPIRATORY SYSTEM ANATOMY
A. Structurally
 Upper respiratory system
• Nose, pharynx and associated structures
 Lower respiratory system
• Larynx, trachea, bronchi and lungs
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RESPIRATORY SYSTEM ANATOMY
B. Functionally
 Conducting zone – conducts air to lungs
• Nose, pharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles
 Respiratory zone – main site of gas exchange
• Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli
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STRUCTURES OF THE RESPIRATORY SYSTEM
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NOSE
Nose is divided into
 External nose – portion visible on face
 Internal nose – large cavity beyond nasal vestibule
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 Internal nares or choanae
 Ducts from paranasal sinuses and nasolacrimal ducts open into internal nose
 Nasal cavity divided by nasal septum
 Nasal conchae subdivide nasal cavity into groovelike passageway called
meatuses (i.e.,Superior, middle, inferior meatuses)
 Increase surface area and prevents dehydration
 Olfactory receptors in olfactory epithelium
 Goblet cell
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Frontal sinus
(b) Parasagittal section of left side of head and neck showing
location of respiratory structures
Olfactory epithelium
Superior
Middle
Inferior
Nasal vestibule
External naris
Oral cavity
Palatine bone
Soft palate
Mandible
Middle
Superior
Nasal
conchae
Nasal meatuses
Regions of the pharynx
Nasopharynx
Oropharynx
Laryngopharynx
Parasagittal
plane
Tongue
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PHARYNX
 Funnel shaped tube
 13cm long
 Starts at internal nares and extends till larynx
 Contraction of skeletal muscles assists in deglutition
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 Functions
 Passageway for air and food
 Resonating chamber
 Houses tonsils
 3 anatomical regions
 Nasopharynx
 Oropharynx
 Laryngopharynx
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(b) Parasagittal section of left side of head and neck showing
location of respiratory structures
Hyoid bone
Ventricular fold (false
vocal cord)
Vocal fold (true vocal cord)
Larynx
Thyroid cartilage
Cricoid cartilage
Thyroid gland
NASOPHARYNX
Opening of auditory
tube
Uvula
Palatine tonsil
Fauces
OROPHARYNX
Epiglottis
LARYNGOPHARYNX
Esophagus
Trachea
Regions of the pharynx
Nasopharynx
Oropharynx
Laryngopharynx
Parasagittal
plane
Tongue
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LARYNX
 Short passageway connecting laryngopharynx with trachea
 Composed of 9 pieces of cartilage
 Epiglottis closes off glottis during swallowing
 Glottis – pair of folds of mucous membranes, vocal folds (true vocal cords), and rima
glottidis
 Cilia in upper respiratory tract move mucous and trapped particles down toward
pharynx
 Cilia in lower respiratory tract move them up toward pharynx Jegan

Hyoid bone
Epiglottis
Epiglottis:
Leaf
Stem
Corniculate cartilage
Thyroid cartilage
(Adam’s apple)
Arytenoid cartilage
Cricothyroid ligament
Cricoid cartilage
Cricotracheal ligament
Thyroid gland
Parathyroid glands (4)
Tracheal cartilage
Thyroid glandLarynx
(a) Anterior view (b) Posterior view
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TRACHEA
 Windpipe, 12cm long
 Extends from larynx to superior border of T5 where it divides into right and left
primary bronchi
 4 layers
• Mucosa ,Submucosa, Hyaline cartilage, Adventitia
 16-20 C-shaped rings of hyaline cartilage stacked one above the other
 Open part faces esophagus
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Location of Trachea
Copyright 2009, John Wiley & Sons, Inc. Jegan

BRONCHI
 At T5 trachea divides into Right and left primary bronchus
 Carina – internal ridge where the trachea divide
• Most sensitive area for triggering cough reflex
 Primary bronchi divide to form bronchial tree
• Secondary lobar bronchi (one for each lobe), tertiary (segmental) bronchi,
bronchioles, terminal bronchioles
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 Structural changes with branching
• Mucous membrane changes
• Incomplete rings become plates and then disappear
• As cartilage decreases, smooth muscle increases
 Sympathetic ANS – relaxation/ dilation
 Parasympathetic ANS – contraction/ constriction
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Larynx
Anterior view
Trachea
Left lung
Location of carina
Left secondary bronchus
Left tertiary bronchus
Left primary bronchus
Left bronchiole
Left terminal bronchiole
Diaphragm
Right lung
Visceral pleura
Parietal pleura
Pleural cavity
Right primary
bronchus
Right secondary bronchus
Right tertiary
bronchus
Right bronchiole
Right terminal
bronchiole
Cardiac notch
BRANCHING OF
BRONCHIAL TREE
Trachea
Primary bronchi
Secondary bronchi
Tertiary bronchi
Bronchioles
Terminal bronchioles
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LUNGS
 Separated from each other by the heart and other structures in the mediastinum
 Each lung enclosed by double-layered pleural membrane
• Parietal pleura – lines wall of thoracic cavity
• Visceral pleura – covers lungs themselves
 Pleural cavity is space between layers
• Pleural fluid reduces friction, produces surface tension (stick together)
 Cardiac notch – heart makes left lung 10% smaller than right
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POSTERIOR
Sternum
Visceral pleura
Superior vena cava
Left lung
Ascending aorta
Pulmonary arteries
Pulmonary vein
Esophagus
Thoracic aorta
Body of T4
Spinal cord
Parietal pleura
Right lung
Pleural cavity
MEDIALLATERAL
Inferior view of transverse section through thoracic cavity
showing pleural cavity and pleural membranes
Transverse
plane
View
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ANATOMY OF LUNGS
 Lobes – each lung divides by 1 or 2 fissures
– Each lobe receives it own secondary (lobar) bronchus that branch into tertiary
(segmental) bronchi
 Lobules wrapped in elastic connective tissue and contains a lymphatic vessel,
arteriole, venule and branch from terminal bronchiole
 Terminal bronchioles branch into respiratory bronchioles which divide into
alveolar ducts
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(b) Lateral view of right lung
Apex
View (b)
Superior lobe
ANTERIOR
Horizontal
fissure
Cardiac notch
Middle lobe
Base
Oblique fissure
Inferior lobe
POSTERIOR
(c) Lateral view of left lung
Oblique fissure
Inferior lobe
POSTERIOR
View (c)
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(a) Diagram of portion of lobule of lung
Terminal
bronchiole
Pulmonary
venule
Elastic
connective
tissue
Pulmonary
capillary
Visceral
pleura
Alveoli
Pulmonary
arteriole
Lymphatic
vessel
Respiratory bronchiole
Alveoli
Alveolar ducts
Alveolar sac
MICROSCOPIC AIRWAYS
Terminal bronchioles
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli
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ALVEOLI
 Cup-shaped pouch
 Alveolar sac – 2 or more alveoli sharing a common opening
 2 types of alveolar epithelial cells
 Type I alveolar cells – form nearly continuous lining, more numerous than type II,
main site of gas exchange
 Type II alveolar cells (septal cells) – free surfaces contain microvilli, secrete
alveolar fluid (surfactant reduces tendency to collapse)
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 Respiratory membrane
 Alveolar wall – type I and type II alveolar cells
 Epithelial basement membrane
 Capillary basement membrane
 Capillary endothelium
 Very thin – only 0.5 µm thick to allow rapid diffusion of gases
 Lungs receive blood from
 Pulmonary artery - deoxygenated blood
 Bronchial arteries – oxygenated blood to perfuse muscular walls of bronchi and
bronchioles
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Red blood cell
(a) Section through alveolus showing cellular components
Capillary endothelium
Capillary basement
membrane
Epithelial basement
membrane
Type I alveolar cell
Interstitial space
Type I alveolar
cell
Respiratory
membrane
Type II alveolar
(septal) cell
Alveolar
macrophage (dust cell)
Red blood cell
in pulmonary capillary
Alveolus
Elastic fiber
Reticular fiber
Monocyte
Alveolar fluid with surfactant
(b) Details of respiratory membrane
Alveolus
Diffusion
of CO2
Diffusion
of O2
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RESPIRATION (GAS EXCHANGE)
Respiration (gas exchange) steps
 Pulmonary ventilation/ breathing
 Inhalation and exhalation
 Exchange of air between atmosphere and alveoli
 External (pulmonary) respiration
 Exchange of gases between alveoli and blood
 Internal (tissue) respiration
 Exchange of gases between systemic capillaries and tissue cells
 Cellular respiration (makes ATP)
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INHALATION/ INSPIRATION
 Breathing in is called Inhalation (Inspiration)
 Pressure inside alveoli just become lower than atmospheric pressure for air to flow into
lungs
 760 millimeters of mercury (mmHg) or 1 atmosphere (1 atm)
 Achieved by increasing size of lungs
 Boyle’s Law – pressure of a gas in a closed container is inversely proportional to the
volume of the container
 Inhalation – lungs must expand, increasing lung volume, decreasing pressure below
atmospheric pressure
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 Inhalation is active – Contraction of
 Diaphragm – most important muscle of inhalation
 Flattens, lowering dome when contracted
 Responsible for 75% of air entering lungs during normal quiet breathing
 External intercostals
 Contraction elevates ribs
 25% of air entering lungs during normal quiet breathing
 Accessory muscles
 For deep, forceful inhalation
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 When thorax expands, parietal and visceral pleurae adhere tightly due to
subatmospheric pressure and surface tension – pulled along with expanding thorax
 As lung volume increases, alveolar (intrapulmonic) pressure drops
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I
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A
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EXHALATION/ EXPIRATION
 Breathing out is called as exhalation (Expiration)
 Pressure in lungs greater than atmospheric pressure
 Normally passive – muscle relax instead of contract
• Based on elastic recoil of chest wall and lungs from elastic fibers and surface tension of
alveolar fluid
• Diaphragm relaxes and become dome shaped
• External intercostals relax and ribs drop down
 Exhalation only active during forceful breathing
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Alveolar pressure =
758 mmHg
2. During inhalation (diaphragm contracting)
Intrapleural pressure =
754 mmHg
1. At rest (diaphragm relaxed)
3. During exhalation (diaphragm relaxing)
Atmospheric pressure = 760 mmHg Atmospheric pressure = 760 mmHg
Alveolar pressure =
760 mmHg
Intrapleural pressure
=
756 mmHg
Alveolar pressure =
762 mmHg
Intrapleural pressure =
756 mmHg
Atmospheric pressure = 760 mmHg
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E
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H
A
L
A
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During normal quiet inhalation, the
diaphragm and external intercostals
contract. During labored inhalation,
sternocleidomastoid, scalenes, and
pectoralis minor also contract.
Alveolar pressure
increases to 762 mmHg
Atmospheric pressure
is about 760 mmHg
at sea level
Alveolar pressure
decreases to 758 mmHg
During normal quiet exhalation,
diaphragm and external
intercostals relax. During forceful
exhalation, abdominal and internal
intercostal muscles contract.
Thoracic cavity
decreases in size
and lungs recoil
Thoracic
cavity increases
in size and volume of
lungs expands
(a) Inhalation (b) Exhalation
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AIRFLOW
 Air pressure differences drive airflow
 3 other factors affect rate of airflow and ease of pulmonary ventilation
 Surface tension of alveolar fluid
 Lung compliance
 Airway resistance
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Surface tension of alveolar fluid
 Causes alveoli to assume smallest possible diameter
 Accounts for 2/3 of lung elastic recoil
 Prevents collapse of alveoli at exhalation
Lung compliance
 High compliance means lungs and chest wall expand easily
 Related to elasticity and surface tension
Airway resistance
 Larger diameter airway has less resistance
 Regulated by diameter of bronchioles & smooth muscle tone
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EXCHANGE OF OXYGEN AND CARBON DIOXIDE
DALTON’S LAW
 Each gas in a mixture of gases exerts its own pressure as if no other gases were present
 Pressure of a specific gas is partial pressure Px
 Total pressure is the sum of all the partial pressures
 Atmospheric pressure (760 mmHg) = PN2 + PO2 + PH2O + PCO2 + Pother gases
 Each gas diffuses across a permeable membrane from the area where its partial pressure
is greater to the area where its partial pressure is less
 The greater the difference, the faster the rate of diffusion

PARTIAL PRESSURES OF GASES IN INHALED AIR
PN2 =0.786 x 760mm Hg = 597.4 mmHg
PO2 =0.209 x 760mm Hg = 158.8 mmHg
PH2O =0.004 x 760mm Hg = 3.0 mmHg
PCO2 =0.0004 x 760mm Hg = 0.3 mmHg
Pother gases =0.0006 x 760mm Hg = 0.5 mmHg
TOTAL = 760.0 mmHg
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HENRY’S LAW
 Quantity of a gas that will dissolve in a liquid is proportional to the partial
pressures of the gas and its solubility
 Higher partial pressure of a gas over a liquid and higher solubility, more of the
gas will stay in solution
 Much more CO2 is dissolved in blood than O2 because CO2 is 24 times more
soluble
 Even though the air we breathe is mostly N2, very little dissolves in blood due to
low solubility
 Decompression sickness (bends) Jegan

External Respiration in Lungs
 External respiration or pulmonary gas exchange is the diffusion of O2 from air
in the alveoli of the lungs to blood in pulmonary capillaries and the diffusion of
CO2 in the opposite direction
 External respiration in the lungs converts deoxygenated blood (depleted of some
O2) coming from the right side of the heart into oxygenated blood (saturated
with O2) that returns to the left side of the heart
 As blood flows through the pulmonary capillaries, it picks up O2 from alveolar air
and unloads CO2 into alveolar air.
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CO2 exhaled
O2 inhaled
Atmospheric air:
PO2 = 159 mmHg
PCO2 = 0.3 mmHg
Alveolar air:
PO2 = 105 mmHg
PCO2 = 40 mmHg
Oxygenated blood:
PO2 = 100 mmHg
PCO2 = 40 mmHg
Deoxygenated blood:
PO2 = 40 mmHg
PCO2 = 45 mmHg
Systemic tissue cells:
PO2 = 40 mmHg
PCO2 = 45 mmHg
Pulmonary capillaries
(a) External respiration:
pulmonary gas
exchange
(b) Internal respiration:
systemic gas
exchange
Systemic capillaries
To lungs
To right atrium
To left atrium
To tissue cells
Alveoli
CO2 O2
CO2 O2
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 Oxygen
 Oxygen diffuses from alveolar air (PO2 105 mmHg) into blood of pulmonary capillaries
(PO2 40 mmHg)
 Diffusion continues until PO2 of pulmonary capillary blood matches PO2 of alveolar air
 Carbon dioxide
 Carbon dioxide diffuses from deoxygenated blood in pulmonary capillaries (PCO2 45
mmHg) into alveolar air (PCO2 40 mmHg)
 Continues until of PCO2 blood reaches 40 mmHg
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INTERNAL RESPIRATION
 The exchange of O2 and CO2 between systemic capillaries and tissue cells is called
internal respiration or systemic gas exchange
 Oxygen
 Oxygen diffuses from systemic capillary blood (PO2 100 mmHg) into tissue cells
(PO2 40 mmHg) – cells constantly use oxygen to make ATP
 Blood PO2 drops to 40 mmHg by the time blood exits the systemic capillaries
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 Carbon dioxide
 Carbon dioxide diffuses from tissue cells (PCO2 45 mmHg) into systemic capillaries
(PCO2 40 mmHg) – cells constantly make carbon dioxide
 PCO2 blood reaches 45 mmHg
 At rest, only about 25% of the available oxygen is used
 Deoxygenated blood would retain 75% of its oxygen capacity
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RATE OF PULMONARY AND SYSTEMIC GAS EXCHANGE
Rate of pulmonary and systemic gas exchange depends on
 Partial pressures of gases
Alveolar PO2 must be higher than blood PO2 for diffusion to occur – problem with
increasing altitude
 Surface area available for gas exchange
 Diffusion distance
 Molecular weight and solubility of gases
O2 has a lower molecular weight and should diffuse faster than CO2 except for its low
solubility
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TRANSPORT OF OXYGEN
AND CARBON DIOXIDE
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TRANSPORT OF OXYGEN
 Oxygen transport
 Only about 1.5% of O2 is dissolved in plasma
 98.5% bound to hemoglobin in red blood cells
 Heme portion of hemoglobin contains 4 iron atoms – each can bind one O2 molecule
 Oxygen binds to hemoglobin to form Oxyhemoglobin
 Only dissolved portion can diffuse out of blood into cells
 Oxygen must be able to bind and dissociate from heme

Transport of CO2
7% dissolved in plasma
23% as Hb-CO2
70% as HCO3
–
Transport of O2
1.5% dissolved in plasma
98.5% as Hb-O2Alveoli
(a) External respiration:
pulmonary gas
exchange
(b) Internal respiration:
systemic gas
exchange
7% 23%70% 1.5% 98.5%
1.5%70%
7%
23%
CO2
(dissolved)
HCO3
– O2
(dissolved)
O2
(dissolved)HCO3
–
Hb
Hb
To lungs
To right atrium
To left atrium
To tissue cells
Systemic
capillaries
Systemic
tissue cells
Plasma
Red blood cell
Pulmonary
capillaries
CO2 O2
CO2 O2
Hb + O2
Hb–O2
CO2 + Hb
Hb–CO2
Hb
Hb–CO2 Hb–O2
O2
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Relationship between Hemoglobin and Oxygen Partial Pressure
 Higher the PO2, More O2 combines with Hb
 Fully saturated – completely converted to oxyhemoglobin
 When reduced hemoglobin (Hb) is completely converted to oxyhemoglobin (Hb—O2), the
hemoglobin is said to be fully saturated; when hemoglobin consists of a mixture of Hb and Hb—
O2, it is partially saturated.
 Percent saturation expresses average saturation of hemoglobin with oxygen
 Oxygen-hemoglobin dissociation curve
 In pulmonary capillaries, PO2 is high so O2 loads onto Hb
 In tissues, PO2 is low O2 is not held and unloaded
 75% may still remain in deoxygenated blood (reserve) Jegan

P (mmHg)O2
Oxygenated blood
in systemic arteries
Deoxygenated blood
in systemic veins
(average at rest)
Deoxygenated blood
(contracting skeletal muscle)
Percentsaturationofhemoglobin
Oxygen-hemoglobin
Dissociation Curve
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HEMOGLOBIN AND OXYGEN
 Other factors affecting affinity of Hemoglobin for oxygen
 Each makes sense if you keep in mind that metabolically active tissues need
O2, and produce acids, CO2, and heat as wastes
 Acidity
 PCO2
 Temperature
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ACIDITY
 As acidity increases (pH decreases),
affinity of Hb for O2 decreases
 Increasing acidity enhances unloading
 When pH decreases, the entire oxygen–
hemoglobin dissociation curve shifts to the
right; at any given PO2, Hb is less
saturated with O2, a change termed the
Bohr effect
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PARTIAL PRESSURE OF CARBON DIOXIDE
 PCO2
 Also shifts curve to right
 As PCO2 rises, Hb unloads oxygen more
easily
 Low blood pH can result from high PCO2
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TEMPERATURE CHANGES
 Within limits, as temperature increases, more
oxygen is released from Hb
 Heat is a by-product of the metabolic
reactions of all cells
 Metabolically active cells require more O2
and liberate more acids and heat.
 The acids and heat in turn promote release
of O2 from oxyhemoglobin
 During hypothermia, more oxygen remains
bound
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BPG
 2,3-bisphosphoglycerate
 Decreases the affinity of hemoglobin for O2 and thus helps unload O2 from hemoglobin.
 BPG is formed in red blood cells when they break down glucose to produce ATP in a
process called glycolysis
 The greater the level of BPG, the more O2 is unloaded from hemoglobin.
 Certain hormones, such as thyroxine, human growth hormone, epinephrine, norepinephrine,
and testosterone, increase the formation of BPG.
 The level of BPG also is higher in people living at higher altitudes. Jegan

CARBON DIOXIDE TRANSPORT
 Under normal resting conditions, each 100 mL of deoxygenatedblood contains the
equivalent of 53 mL of gaseous CO2, which is transported in the blood in three main
forms
 Dissolved CO2
 Smallest amount, about 7%
 Carbamino compounds
 About 23% combines with amino acids including those in Hb
 Carbaminohemoglobin
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 The formation of carbaminohemoglobin is greatly influenced by PCO2 .
 For example, in tissue capillaries PCO2 is relatively high, which promotes
formation of carbaminohemoglobin.
 But in pulmonary capillaries, PCO2 is relatively low, and the CO2 readilysplits
apart from globin and enters the alveoli by diffusion.
 Bicarbonate ions
 70% transported in plasma as HCO3
-
 CO2 diffuses into systemic capillaries and enters red blood cells, it reacts with
water in the presence of the enzyme carbonic anhydrase (CA) to form carbonic
acid, which dissociates into H and HCO3
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3
-

 Chloride shift
 HCO3
- accumulates inside RBCs as they pick up carbon dioxide
 Some diffuses out into plasma
 To balance the loss of negative ions, chloride (Cl-) moves into RBCs from plasma
 This exchange of negative ions,which maintains the electrical balance between blood plasma
and RBC cytosol, is known as the chloride shift
 Reverse happens in lungs – Cl- moves out as moves back into RBCs
 Haldane effect
 The amount of CO2 that can be transported in the blood is influenced by the percent saturation
of hemoglobin with oxygen.
 The lower the amount of oxyhemoglobin (Hb—O2), the higher the CO2-carrying capacity of the
blood, a relationship known as the Haldane effect.

CONTROL OF RESPIRATION
 The size of the thorax is altered by the action of the respiratory muscles,
which contract as a result of nerve impulses transmitted to them from centers
in the brain and relax in the absence of nerve impulses.
 These nerve impulses are sent from clusters of neurons located bilaterally in
the medulla oblongata and pons of the brainstem.
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 This widely dispersed group of neurons, collectively called the respiratory
center, can be divided into three areas on the basis of their functions:
(1) The medullary rhythmicity area in the medulla oblongata;
(2) The pneumotaxic area in the pons; and
(3) The apneustic area, also in the pons
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MEDULLARY RHYTHMICITY AREA
 The function of the medullary rhythmicity area is to control the basic rhythm of
respiration.
 There are inspiratory and expiratory areas within the medullary rhythmicity area.
 During quiet breathing,
 Inhalation lasts for about 2 seconds
 Exhalation lasts for about 3 seconds
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 At the end of 2 seconds, the inspiratory area becomes inactive and nerve impulses
cease.
 With no impulses arriving, the diaphragm and external intercostal muscles relax for
about 3 seconds, allowing passive elastic recoil of the lungs and thoracic wall.
 Then, the cycle repeats.
 The neurons of the expiratory area remain inactive during quiet breathing.
 However, during forceful breathing nerve impulses from the inspiratory area
activate the expiratory area
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PNEUMOTAXIC AREA
 Although the medullary rhythmicity area controls the basic rhythm of respiration, other sites
in the brain stem help coordinate the transition between inhalation and exhalation.
 One of these sites is the pneumotaxic in the upper pons , which transmits inhibitory impulses
to the inspiratory area.
 The major effect of these nerve impulses is to help turn off the inspiratory area before the
lungs become too full of air.
 In other words, the impulses shorten the duration of inhalation.
 When the pneumotaxic area is more active, breathing rate is more rapid.
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APNEUSTIC AREA
 Another part of the brain stem that coordinates the transition between inhalation
and exhalation is the apneustic area in the lower pons.
 This area sends stimulatory impulses to the inspiratory area that activate it and
prolong inhalation.
 The result is a long, deep inhalation.
 When the pneumotaxic area is active, it overrides signals from the apneustic area.
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LUNG VOLUMES
 While at rest, a healthy adult averages 12 breaths a minute, with each inhalation
and exhalation moving about 500 mL of air into and out of the lungs.
 The volume of one breath is called the tidal volume (VT).
 The minute ventilation (MV)—the total volume of air inhaled and exhaled each
minute—is respiratory rate multiplied by tidal volume:
MV = 12 breaths/min X 500 mL/breath
= 6 liters/min
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 The apparatus commonly used to measure the volume of air exchanged during
breathing and the respiratory rate is a spirometer or respirometer
 In a typical adult, about 70% of the tidal volume (350 mL) actually reaches the
respiratory zone of the respiratory system—the respiratory bronchioles, alveolar
ducts, alveolar sacs, and alveoli—and participates in external respiration.
 The other 30% (150 mL) remains in the conducting airways of the nose, pharynx,
larynx, trachea, bronchi, bronchioles, and terminal bronchioles.
 Collectively, the conducting airways with air that does not undergo respiratory
exchange are known as the anatomic (respiratory) dead space.
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 The alveolar ventilation rate is the volume of air per minute that actually reaches
the respiratory zone. In the example just given,
Alveolar ventilation rate = 350 mL/breath X 12 breaths/min
= 4200 mL/min.
 By taking a very deep breath, you can inhale a good deal more than 500
mL. This additional inhaled air, called the inspiratory reserve volume.
 It is about 3100 mL in an average adult male and 1900 mL in an average
adult female
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 If you inhale normally and then exhale as forcibly as possible, you should be able
to push out considerably more air in addition to the 500 mL of tidal volume.
 The extra 1200 mL in males and 700 mL in females is called the expiratory reserve
volume.
 The FEV1.0 is the forced expiratory volume in 1 second, the volume of air that can
be exhaled from the lungs in 1 second with maximal effort following a maximal
inhalation
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 Even after the expiratory reserve volume is exhaled, considerable air remains in the
lungs. This volume, which cannot be measured by spirometry, is called the residual
volume and amounts to about 1200 mL in males and 1100 mL in females.
 If the thoracic cavity is opened, the intrapleural pressure rises to equal the
atmospheric pressure and forces out some of the residual volume. The air remaining
is called the minimal volume
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LUNG CAPACITIES
 Inspiratory capacity is the sum of tidal volume and inspiratory reserve volume
Inspiratory capacity in males = 500 mL + 3100 mL
= 3600 mL
Inspiratory capacity in females = 500 mL + 1900 mL
= 2400 mL
• Functional residual capacity is the sum of residual volume and expiratory reserve volue
Functional residual capacity in males = 1200 mL +1200 mL
= 2400 mL
Functional residual capacity in females =1100 mL +700 mL
= 1800 mL Jegan

Vital capacity is the sum of inspiratory reserve volume, tidal volume, and expiratory
reserve volume
Vital capacity in male = 3600 mL + 500 mL + 1200 mL
= 4800 mL
Vital capacity in females = 1900 mL + 500 mL + 700
= 3100 mL
Total lung capacity is the sum of vital capacity and residual volume
Total lung capacity in males = 4800 mL + 1200 mL
= 6000 mL
Total lung capacity in females = 3100 mL +1100 mL
= 4200 Jegan

Respiratory system

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