Download Respiratory System

The Respiratory System
Why do we need oxygen?
Answer: We need it to make energy
through aerobic respiration!
Organs of the Respiratory System
 Nose
 Pharynx
 Larynx
 Trachea
 Bronchi
 Bronchioles
 Lungs –
alveoli
Functions of the Respiratory System
1. Gas exchange between the blood and
external environment
2. Purification, warming, and humidifying
of incoming air
3. Provides olfactory sensations to the
brain for sense of smell
4. Produces sounds for communication
Divisions of the Respiratory Tract
1. Conduction portion: nasal cavity 
larger bronchioles (cleans and warms
the air)
2. Respiratory portion: smallest
bronchioles  alveoli (permits gas
exchange)
Upper Respiratory Tract
Nose
 Olfactory receptors are located on the
superior surface
 Mucosa: lines the nasal cavity; moistens
air and traps incoming foreign particles
 Conchae: projections of the nasal cavity;
increases air turbulence within the nasal
cavity
 Sinuses: cavities within bones surrounding
the nasal cavity; lighten the skull, resonate
sounds for speech, and produce mucus
Pharynx (Throat)
 Muscular passage from nasal cavity to
larynx
 Common passageway for air and food
 Contains tonsils
 Auditory tubes enter here (equalize
pressure and drain mucus)
Larynx (Voice Box)
 Routes air and food into proper channels
 Made of eight rigid cartilages and a spoonshaped flap of elastic cartilage (epiglottis)
 Epiglottis: routes food to the esophagus
and air toward the trachea
 Contains vocal cords (folds) that vibrate
with expelled air to create sound (speech)
 Glottis: opening between vocal cords
Trachea (Windpipe)
 Connects larynx with bronchi
 Lined with ciliated mucosa that:
 Beat continuously in the opposite direction of
incoming air
 Expel mucus loaded with dust and other
debris away from lungs
 Walls are reinforced with C-shaped firm
cartilage (open posteriorly)
Primary Bronchi
 Trachea divides into right and left
bronchi
 Right bronchus is wider, shorter,
and straighter than left
 Bronchi then subdivide into smaller
and smaller branches
Lungs
 Occupy most of the thoracic cavity
 Apex is near the clavicle (collar bone) and
base rests on the diaphragm
 Each lung is divided into lobes by fissures:
a. Left lung – two lobes
b. Right lung – three lobes
Coverings of the Lungs
 Pulmonary (visceral) pleura covers the
lung surface
 Parietal pleura lines the walls of the
thoracic cavity
 Pleural fluid fills the area between
layers of pleura to allow gliding
Lungs
Bronchioles
 Smallest branches of the bronchi
 All but the smallest branches have
reinforcing cartilage
 Terminal bronchioles end in alveoli
Alveoli
 Consist of a duct and the alveolus
 Gas exchange takes place within the
alveoli in the respiratory membrane
 Respiratory membrane (air-blood barrier)
 Thin epithelium lines alveolar walls
 Pulmonary capillaries cover external
surfaces of alveoli
Bronchioles and Alveoli
Gas Exchange in the Alveoli
 Gas crosses the respiratory membrane
by diffusion
 Oxygen enters the blood
 Carbon dioxide enters the alveoli
 Macrophages protect against infectious
microorganisms
 Surfactant coats gas-exposed alveolar
surfaces to keep alveoli inflated
Respiratory Membrane of Alveoli
Events of Respiration
 Pulmonary ventilation: moving air in and out
of the lungs
 External respiration: gas exchange between
pulmonary capillaries and alveoli
 Internal respiration: gas exchange between
blood and tissue cells in systemic capillaries
Mechanics of Breathing
(Pulmonary Ventilation)
 Two phases:
1. Inspiration/inhalation – flow of air into lung
2. Expiration/exhalation – air leaving lung
Inspiration/inhalation
 Diaphragm contracts (flattens), external
intercostals contract raising the rib cage
 Volume of the thoracic cavity increases
 Pressure in thoracic cavity decreases
 Air is pulled into the lungs (from high to
low pressure)
Inspiration/inhalation
Expiration/exhalation
 Largely a passive process which depends
on natural lung elasticity
 Diaphragm relaxes (pushes up), external
intercostals relax depressing the rib cage
 Air is pushed out of the lungs
 Forced expiration can occur mostly by
contracting internal intercostal muscles to
depress the rib cage further
Expiration/exhalation
Breathing Animation
Respiratory Volumes and Capacities
 Tidal volume (TV) is normal breathing and
moves about 500 mL of air with each breath
 Many factors affect respiratory capacity:
1. A person’s size
2. Sex
3. Age
4. Physical condition
 Residual volume (RV) of air: amount of air
remaining in the lungs after normal
exhalation (~1200 mL)
Respiratory Volumes and Capacities
 Inspiratory reserve volume (IRV): amount of air
that can be taken in forcibly over the tidal
volume (5x TV)
 Expiratory reserve volume (ERV): amount of air
that can be forcibly exhaled (approx. = to RV)
Respiratory Volumes and Capacities
 Vital capacity (VC): the total amount of
exchangeable air
 Vital capacity = TV + IRV + ERV
 Dead space volume: air that remains in
conducting zone and never reaches alveoli
(150 mL)
 Functional volume: air that actually
reaches the respiratory zone (350 mL)
Respiratory Volumes and Capacities
Gas Transport in the Blood
1. Oxygen transport in the blood
 Inside red blood cells attached to hemoglobin
 A small amount is carried dissolved in the
plasma
2. Carbon dioxide transport in the blood
 Most is transported in the plasma as bicarbonate
ion (HCO3–)
 A small amount is carried inside red blood cells
on hemoglobin, but at different binding sites than
those of oxygen
Respiration
Neural Regulation of Respiration
 Activity of respiratory muscles is transmitted
to the brain by the phrenic and intercostal
nerves
 Phrenic nerve controls the diaphragm
 Neural centers that control rate and depth are
located in the medulla
 The pons appears to smooth out respiratory
rate
 Normal respiratory rate is 12–16 respirations
per minute
Neural Regulation of Respiration
Chemical Regulation of Respiration
1. Carbon dioxide levels

Level of carbon dioxide in the blood is the main
regulatory chemical for respiration

Increased carbon dioxide increases respiration

Changes in carbon dioxide act directly on the
medulla oblongata
2. Oxygen levels

Changes in oxygen concentration in the blood are
detected by chemoreceptors in the aorta and
carotid artery

Information is sent to the medulla oblongata
Other Factors Influencing
Respiratory Rate and Depth
 Physical factors:
1. Increased body temperature
2. Exercise
3. Talking
4. Coughing
 Volition (conscious control)
 Emotional factors
Effects of Aging on the Respiratory System
 Elasticity of lungs decreases
 Vital capacity decreases
 Blood oxygen levels decrease
 Respiratory rate often increases
 Stimulating effects of carbon dioxide
decreases
 More risks of respiratory tract infection
Diagnostic Tests for the Respiratory System
 Spirometry: measures how much and how
quickly a person can move air out of the lungs
 Pulse-oximetry: non-invasive measure of the
oxygen saturation of the blood
 Arterial blood gas: measures the amount of
oxygen and carbon dioxide in a blood sample
 Stress test: lung function is measured during
exercise
 Chest x-ray: x-ray of the thorax while holding
breath