Function
 Obtain oxygen for cellular
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respiration
Remove carbon dioxide
Filter and entrap particles
from air
Control temperature of the
air
Control water content of the
air
Produce vocal sounds
Participate in smell
Major Organs of the Respiratory
System
 Trachea (windpipe)
-Extends downward anterior into right and left bronchi
-Has ciliated mucous membrane that filters incoming air and moves
entrapped particles into the pharynx
 Bronchi
-Branches off into left and right primary bronchi
-Makes up bronchial tree which consists of branched airways leading
from trachea to microscopic air sacs in the lungs
 Bronchioles
-Smaller tubes that branch from the tertiary bronchi, which
branched from the secondary bronchi
 Alveoli
-Smaller microscopic air sacs within the capillary networks
Upper Respiratory Tract
Major Structures
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Nostrils
Nasal Cavity
Mouth
Pharynx
Larynx
Inhaled air is
moistened, warmed,
and cleansed by the
tissue that lines the
nasal cavity.
Larynx
Location
 Anterior aspect of the neck
 Inferior to pharynx
 Superior to trachea
Includes:
 Cricoid cartilage
 Thyroid cartilage
 Epiglottis cartilage
3 Cartilaginous Structures
 Cricoid cartilage: ring of hyaline
guards glottis, prevents food
from going into trachea,
involved in gag reflex
 Thyroid cartilage (Adam’s apple)
protect vocal folds, changes
pitch of voice
 Epiglottis
Provides attachment for
muscles involved in opening
Lower Respiratory Tract
Major Structures
 Trachea
 Bronchi
 Tertiary Bronchi
 Bronchioles
 Alveoli
 Diaphragm
Lungs
Structure
 3 lobes in right lung
 2 lobes in left lung
 Pleura
 Pleura cavity
 Pleural fluid
 Diaphragm muscle
Air enters each lung through a single bronchi, which
branches out into bronchioles, and eventually alveoli
Pleura
 Double layered serous membrane that surrounds the lungs
 The pleural cavity is the space within, which the lung has grown
 Serous membranes secrete serous fluid that keeps the lungs from being
irritated when breathing
Diaphragm
The diaphragm controls
breathing
 Contracted during inhalation,
relaxed during expiration
 Air flows from high pressure to low
pressure
 When inhaling, air pressure lower
on the outside of lungs than the
inside lungs
 When exhaling, air pressure higher
on the outside of lungs than the
inside of lungs
Steps of Respiration
1. Ventilation: movement of air in/out of lungs
2. External respiration: gas exchange between blood and
air in lungs
3. Gas transport in blood between blood and body cells
4. Internal respiration: gas exchange between blood and
cells
Respiratory Volume & Capacity
 Tidal volume: amount of air inhaled and exhaled in a natural breath
 Expiratory and inspiratory reserve volume: amounts of air possible to
inhale or exhale
 Residual volume: residual air constantly remaining in the lungs
 Total lung capacity: volume of air contained in lungs at end of a
maximal inspiration
Gas Exchange in Alveoli
 When the partial pressures in the lungs are different than
the partial pressures in the capillaries, diffusion occurs
O2 diffuses from lungs
into alveolar capillaries
during inhalation
CO2 diffuses into the
lungs from the alveolar
capillaries during
exhalation
How Blood Carries Gases
 Oxygen and carbon
dioxide are carried by
hemoglobin in the red
blood cells
 2 or 4 oxygen can be
carried by a single blood
cell
Carbon Dioxide Transport
 Can be carried in solution, bound to hemoglobin, or as
bicarbonate ion
 CO2 + H2O  H2CO3
-Carbon dioxide reacts w/ water to form carbonic acid
 H2CO3  H+ + HCO3- Resulting carbonic acid dissociates, releasing hydrogen
ions and bicarbonate ions
 H+ + HCO3-  H2CO3  CO2 +H2O
- Hydrogen ion and bicarbonate ions recombine to form
carbonic acid, and carbonic anhydrase breaks down to yield
carbon dioxide and water
Lung- Heart Relationship
 The pulmonary artery
start from the heart
carrying oxygen depleted
blood to the lungs
 The pulmonary vein
returns oxygen rich blood
from the lungs to the
heart
Respiratory Center in the Brain
 Although we can control our breath, most respiration is autonomic
 The respiratory system, located in brainstem, is made up of neurons,
widely scattered in medulla oblongata and pons
 Medulla rhythmicity area contains 2 groups
Dorsal: controls basic rhythm of inspiration and emit bursts of
impulses that signal the diaphragm and other inspiratory
muscles to contract
Ventral: during heavy breathing neurons generate impulses that
increase inspiratory movements
Factors That Affect Breathing
Factors:
Chemicals, stretching of lung
tissues, emotional states, and
chemoreceptors
Hyperventilation:
Diaphragm and chest muscle
spasms and/or airways become
constricted, causing person to
breathe rapidly
Asthma:
Thickens muscle in bronchial
tubes, restricting airways and
making it harder to breathe
Lung Cancer
Lung cancer results in large parts of the lung becoming
inactive
Causes:
Family history of lung disease or
cancer, smoking, being regularly
exposed to unsafe chemicals or air
Effects:
Shortness of breath, dizziness,
painful breathing, chronic coughing
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