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Respiratory System
VNSG 1420 Anatomy & Physiology
Chapter 16
Respiration
Process by which oxygen is obtained from the
environment & delivered to the cells (scientific definition)
Carbon dioxide is transported to outside of body
in a reverse pathway
3 phases of respiration
 Pulmonary ventilation
 External exchange of gases
 Internal exchange of gases
See Figure 16-1, p 306
Three Phases of Respiration
Pulmonary Ventilation
 air
exchanged between atmosphere & air sacs of lungs
by inspiration & expiration
External exchange of gases
 oxygen
passes from air sacs into blood & carbon
dioxide passes out of blood by diffusion (lungs &
environment)
Internal exchange of gases
 oxygen
carried to cells & carbon dioxide carried from
tissue cells to lungs in circulating blood (blood & body cells)
Cellular Respiration
Oxygen is taken into cell & used in
breakdown of nutrients with the release of
energy
Carbon dioxide is waste product of cellular
respiration
Respiratory System
Conducts air into lungs
Exchange of oxygen & carbon dioxide
between atmosphere & blood
Components (anatomy)
 Nasal
cavities
 Pharynx - throat
 Larynx - voice box
 Trachea - windpipe
 Bronchi
Nasal Cavities
Nostrils (nares) - initial site of air entry
Nasal cavities - 2 spaces inside nostrils - separated
by septum
Septum & walls - mucous membrane covering with blood vessels to deliver heat & moisture
Secrete up to 1 quart of liquid per day
 Mucous membranes filter out foreign bodies, warm &
moisten air

More on Nasal Cavities . . .
Conchae
3 paired bony projections in lateral walls - increase
surface for travel of air
Air changes with contacting lining of nose
 Foreign
bodies filtered by nostril hairs or surface
mucus
 Air warmed by vascular membrane blood
 Air moistened by liquid secretions
Sinuses
 small
mucous membrane lined cavities in bones of
skull - communicate with nasal cavities
Pharynx
Pharynx / throat - carries air to respiratory tract &
carries food & liquids to digestive system
 Nasopharynx - superior (upper) part behind nasal
cavity
 Oropharynx - middle section behind mouth
 Laryngeal pharynx – inferior (lowest) portion opens
into larynx (voice box) toward front & toward
esophagus in back
See Figure 16-2, p 307
Pharynx
Larynx
Larynx / voice box - cartilage framework between
pharynx & trachea
 Adam’s apple - projection of thyroid cartilage
 Vocal cords - paired mucous membrane folds - for
producing speech - air flow cause vibrations
 Glottis - space between vocal cords
 Epiglottis - leaf shaped cartilage - covers larynx
during swallowing
See Figures 16-3 & 16-4, pp 308 & 309
Larynx
Trachea
Trachea / windpipe - conducts air between larynx &
lungs
 Tubular - from lower larynx edge to upper chest
above heart
 C- shaped (horseshoe) frame of cartilage - to keep
structure open
 Framework of separate cartilages
 Open sections in cartilage lined up in back so
esophagus can bulge into area when swallowing
See Figures 16-2 & 16-3, pp 307 & 308
Trachea
Main Stem Bronchi
Main Stem Bronchi branches off trachea enter
lungs then subdivide into secondary bronchi
 Walls
contain cartilage - to keep airways open
 Right bronchus - larger diameter than left - extends
down in vertical direction (inhaled foreign bodies
usually enter right bronchus)
 Each bronchus enters lung at hilum - notched
depression
Blood vessels & nerves also connect with lungs at
hilum region of each lung
Bronchi / Bronchioles
Lining of Air Passages
Simple columnar epithelium - appear stratified,
but are not
 Pseudo-stratified
- falsely stratified
See Figure 16-6, page 310
Epithelial cells have cilia to filter out impurities &
to move fluids toward throat
Impurities eliminated by coughing, sneezing or
blowing nose
Lungs
Organs of gas exchange - diffusion of gases
occurs through thin delicate tissues
 Left lung indented to accommodate heart
 Right lung - 3 lobes with 3 secondary bronchi
 Left lung - 2 lobes with 2 secondary bronchi
Bronchi divide like tree branches
Bronchioles - smallest conducting tubes - no
cartilage - mostly smooth muscle
Bronchial tree – bronchi & bronchioles
Lung Structures & Related Structures
Lobes
Bronchi
Bronchioles
Alveoli
Lung cavities
Pleura
Mediastinum
Diaphragm
Alveoli
Clusters of tiny air sacs where gases are
exchanged
 located
at end of terminal bronchioles
Single squamous cell epithelium wall
 easy
passage of gases entering & leaving blood
circulating through millions of capillaries covering
alveoli
Surfactant
 reduces
alveoli surface tension - eases expansion of
lungs & prevents collapse of alveoli
Lung Cavities & Pleura
Lungs occupy thoracic cavity
Diaphragm - muscular partition between thoracic &
abdominal cavities
Pleura - doubled membrane sac - encloses each lung
 Visceral pleura - attached to lung surface
 Parietal pleura - attached to chest wall
Pleural space - between layers of pleura
 allows lung surfaces to slide easily & enlarge
effortlessly as thoracic volume changes during
breathing
More on Lung Cavities . . .
Mediastinum - space & organs between lungs
 Contains
heart, great blood vessels, esophagus
trachea & lymph nodes
See Figure16-2, page 307
Process of Respiration
Respiration - exchange of gases in lungs & transport
of gases in blood
Pulmonary ventilation / breathing
 movement
of air in & out of the lungs
2 phases of ventilation
 Inhalation (inspiration) – active phase
 Drawing
of air into lungs
 Exhalation
 Expulsion
(expiration) - passive phase
of air from lungs
Inhalation
Respiratory muscles contract – active phase
Diaphragm flattens & presses abdominal organs
down & forward - rib cage rises up & out
Thoracic cavity size increases
 gas
pressure decreases with cavity
Air drawn into lung by suction
Compliance
 ease
with which lungs & thorax can be expanded
Exhalation
Muscles of respiration relax – passive phase
Thorax decreases in size
Ribs & diaphragm return to usual positions
Lungs become smaller during exhalation
Forceful exhalation uses muscles of chest &
abdomen
See Figure 16-7, p 311
Lung Volume
Lung volumes used to evaluate respiratory
function
Tidal volume - amount of air moved in & out of
lungs in quiet relaxed breathing
Residual volume - volume of air that is always
in the lungs
See Table 16-1, p 312 & Figure 16-9, p 313
Lung Capacity
Lung capacity = tidal volume + residual volume
Vital capacity - amount of air that can be expelled
from lungs by maximum exhalation following
maximum inhalation
Total lung capacity - volume of air in lung after
maximum inhalation
Functional residual capacity - amount of air in
lungs after normal inhalation
Gas Exchange in the Lungs
Gases move from area of higher concentration
to area of lower concentration (diffusion)
Respiratory membrane - thin & moist
 separates
alveolar wall from capillary walls
External exchange
 gases
move between alveoli & capillary blood
Internal exchange
 occurs
between tissues and blood - oxygen leaves
blood as carbon dioxide enters from tissue cells
More on Gas Exchange . . .
Inspired air = 21 % oxygen (O2) & 0.04 %
carbon dioxide (CO2)
Expired air = 16 % oxygen (O2) & 3.5 % carbon
dioxide (CO2)
Diffusion - 2 way process - takes place through
wall of alveoli & capillaries around alveoli
See Figure 16-10, p 314
Gas Transport
Oxygen almost totally bound to heme portion of
hemoglobin in RBCs
 Separates
from hemoglobin when oxygen
concentration is low (in tissues)
Oxygen (O2) has to separate from hemoglobin to be
able to enter cells
Carbon dioxide (CO2) - most carried as
bicarbonate ion
 Regulates
pH of blood
Partial Pressure of Gases
Air is mixture of gases
Gas concentrations - expressed as pressures
Oxygen (O2) & carbon dioxide (CO2) exert
only partial pressures
PO2 - partial pressure of O2
PCO2 - partial pressure of CO2
Transport of Oxygen (O2)
O2 bound to heme portions is released as
concentrations (partial pressure) of O2 drops in
tissues
O2 must separate from hemoglobin to enter cells
Arterial blood in systemic arteries & pulmonary
veins - 97 % O2 saturation
Venous blood in systemic veins & pulmonary
arteries - 70 % O2 saturation - cells take up
other 27 %
Transport of Carbon Dioxide
CO2 - constantly produced in tissues
 Byproduct
of metabolism
CO2 diffuses from cells into blood for transport
to lungs in 3 ways
 10
% dissolved in plasma & fluid in RBCs
 15% combined with hemoglobin protein & plasma
proteins
 75% transported as bicarbonate ion – from CO2
dissolving in blood fluids
More on Carbon Dioxide Transport . . .
Bicarbonate ion formed slowly in plasma
 Carbonic anhydrase (enzyme) - aids rapid
formation of bicarbonate ion in RBCs
 Carbonic
acid - ionizes into bicarbonate &
hydrogen ions
Reactions reverse when blood reaches lungs &
CO2 is exhaled
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3carbonic
acid
hydrogen
bicarbonate
ion
ion
Carbon Dioxide & Acid-Base Balance
CO2 - important in regulating blood pH
(acid-base balance)
Exhalation of CO2-  in pH
 Blood
becomes more base (alkaline)
Retention of carbon dioxide -  in pH
 Blood
becomes more acid as blood CO2
increases
Bicarbonate ion - buffer to keep pH of 7.4
Regulation of Respiration
Primary control of respiration occurs in
respiratory control centers located in medulla
oblongata & pons of brain stem
 Centers
respond to changes in hydrogen ion
concentrations in cerebrospinal fluid
 Blood chemistry changes are detected by
chemoreceptors outside medulla
 H+ ions related to blood CO2 concentration
Nervous System Control
Respiratory control center located partly in
medulla & partly in pons of central nervous
system
 Main
part of control center in medulla - sets basic
pattern of respiration - can be modified by pons
centers
Breathing - continuously regulated
 O2,
CO2 & acid stay within normal limits
Phrenic nerve - controls diaphragm
More on Nervous System Control . . .
Motor nerve fibers from medulla centers extend
into cervical (neck) part of spinal cord
 On
to phrenic nerve to diaphragm
Respiratory centers in brain stem are under
involuntary control
Diaphragm & other breathing muscles can
control breathing rate & depth by voluntary
control of messages from cortex brain centers
Chemical Control
Central & peripheral chemorecptors detect
changes in CO2, hydrogen ion, & O2
composition of blood to regulate breathing
 Central
- located near medulla respiratory centers –
respond to ↑ CO2 levels
 Peripheral – located in neck & aortic arch - respond
to considerably low O2 levels
CO2 is main controller of respiration
Breathing must  when CO2 levels 
Breathing / Respiratory Rates
One cycle of inhalation & exhalation counts as 1
breath
 Normal adult = 12-20 per minute
 Children = 20-40 per minute
 Higher in infants
Count for at least 30 seconds
Best to count if patient is unaware
Abnormal Ventilation
Hyperventilation
 High O2 levels
 Low CO2 level (hypocapnia)
 Increase blood pH (alkalosis)
Hypoventilation
 Insufficient air in alveoli
 Decrease blood pH (acidosis)
Lung Scan
Altered Breathing Terms
Hyperpnea
Hypopnea
Tachypnea
Apnea
Dyspnea
Orthopnea
Results of Inadequate Respiration
Cyanosis
Hypoxia
Anoxia
Hypoxemia
Suffocation
Aging & Respiratory Tract
Respiratory tract tissues lose elasticity &
become more rigid with age
Chest wall rigidity, arthritis & loss of strength in
breathing muscles - lead to decrease lung
capacity & compliance
Increased susceptibility to infection
Emphysema from smoking & other irritants
 activity & exercise can decrease capacity
Emphysema