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The Respiratory System I
Muse Bio2440
lab #7
2/17/10
Activities:
ventilation vs. respiration.
Respiration and oxygen debt.
Spirometer - tidal volume, vital capacity, inspiratory
reserve.
CO2 flush - O2 effect
pH and CO2
Cat lung inflation
Components of the Respiratory
System
Five Functions of the Respiratory System






Provides extensive gas exchange surface area between
air and circulating blood
Moves air to and from exchange surfaces of lungs
Protects respiratory surfaces from outside environment
Produces sounds
Participates in olfactory sense
Respiratory System Anatomy

Structurally

Upper respiratory system


Lower respiratory system


Nose, pharynx and associated structures
Larynx, trachea, bronchi and lungs
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
Components of the Respiratory
System

Organization of the Respiratory System

The respiratory system is divided into


Upper respiratory system: above the larynx
Lower respiratory system: below the larynx
Structures of the Respiratory System
Nose


External nose – portion visible on face
Internal nose – large cavity beyond nasal
vestibule




Internal nares or choanae
Ducts from paranasal sinuses and nasolacrimal
ducts open into internal nose
Nasal cavity divided by nasal septum
Nasal conchae subdivide cavity into meatuses


Increase surface are and prevents dehydration
Olfactory receptors in olfactory epithelium
Nasal Cavity

Superior, middle, and inferior nasal conchae



Protrude from the lateral walls
Increase mucosal area
Enhance air turbulence
Pharynx



Starts at internal nares and extends to cricoid cartilage of
larynx
Contraction of skeletal muscles assists in deglutition
Functions




Passageway for air and food
Resonating chamber
Houses tonsils
3 anatomical regions



Nasopharynx
Oropharynx
Laryngopharynx
Larynx


Short passageway connecting laryngopharynx with trachea
Composed of 9 pieces of cartilage






Thyroid cartilage or Adam’s apple
Cricoid cartilage hallmark for tracheotomy
Epiglottis closes off glottis during swallowing
Glottis – pair of folds of mucous membranes, vocal folds
(true vocal cords, and rima glottidis (space)
Cilia in upper respiratory tract move mucous and trapped
particles down toward pharynx
Cilia in lower respiratory tract move them up toward
pharynx
Larynx
Structures of Voice Production

Mucous membrane of larynx forms

Ventricular folds (false vocal cords) – superior pair


Vocal folds (true vocal cords) – inferior pair




Function in holding breath against pressure in thoracic
cavity
Muscle contraction pulls elastic ligaments which stretch
vocal folds out into airway
Vibrate and produce sound with air
Folds can move apart or together, elongate or shorten,
tighter or looser
Androgens make folds thicker and longer – slower
vibration and lower pitch
Trachea

Extends from larynx to superior border of T5


4 layers





Divides into right and left primary bronchi
Mucosa
Submucosa
Hyaline cartilage
Adventitia
16-20 C-shaped rings of hyaline cartilage

Open part faces esophagus
The Trachea
Figure 23–6 The Anatomy of the Trachea: A Diagrammatic Anterior View.
Location of Trachea
The Trachea
Figure 23–6b The Anatomy of the Trachea: A Cross-Sectional View.
Bronchi


Right and left primary bronchus goes to right lung
Carina – internal ridge


Divide to form bronchial tree


Most sensitive area for triggering cough reflex
Secondary lobar bronchi (one for each lobe), tertiary
(segmental) bronchi, bronchioles, terminal bronchioles
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
Lungs


Separated from each other by the heart and other
structures in the mediastinum
Each lung enclosed by double-layered pleural membrane



Pleural cavity is space between layers


Parietal pleura – lines wall of thoracic cavity
Visceral pleura – covers lungs themselves
Pleural fluid reduces friction, produces surface tension (stick
together)
Cardiac notch – heart makes left lung 10% smaller
than right
Relationship of the Pleural Membranes to
Lungs
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
About 25 orders of branching
Components of the Respiratory
System
Figure 23–2b, c The Respiratory Epithelium of the Nasal Cavity and
Conducting System.
Microscopic Anatomy of Lobule of Lungs
Alveoli



Cup-shaped outpouching
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)
Alveolus

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
Components of Alveolus
The Lungs
Figure 23–11a Alveolar Organization: Basic Structure of a Portion of Single
Lobule.
Components of the Respiratory
System

The Respiratory Epithelium

For gases to exchange efficiently


Alveoli walls must be very thin (<1 µm)
Surface area must be very great (about 35 times the
surface area of the body)
Surface must be moist
Concentration of oxygen in water at 20 degrees = 250 uM
Concentration of oxygen in air = 9 M
The Lungs
Figure 23–11b Alveolar Organization: A Diagrammatic View of Structure.
Pulmonary ventilation

Respiration (gas exchange) steps
1.
Pulmonary ventilation/ breathing


2.
External (pulmonary) respiration

3.
Inhalation and exhalation
Exchange of air between atmosphere and alveoli
Exchange of gases between alveoli and blood
Internal (tissue) respiration


Exchange of gases between systemic capillaries and
tissue cells
Supplies cellular respiration (makes ATP)
Inhalation/ inspiration

Pressure inside alveoli lust become lower than
atmospheric pressure for air to flow into lungs


Achieved by increasing size of lungs


760 millimeters of mercury (mmHg) or 1
atmosphere (1 atm)
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
Boyle’s Law
Inhalation

Inhalation is active – Contraction of
 Diaphragm – most important muscle of inhalation



External intercostals



Contraction elevates ribs
25% of air entering lungs during normal quiet breathing
Accessory muscles for deep, forceful inhalation
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


Flattens, lowering dome when contracted
Responsible for 75% of air entering lungs during normal quiet
breathing
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
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



Causes alveoli to assume smallest possible diameter
Accounts for 2/3 of lung elastic recoil
Prevents collapse of alveoli at exhalation
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
Lung volumes and capacities




Minute ventilation (MV) = total volume of air
inhaled and exhaled each minute
Normal healthy adult averages 12 breaths
per minute
moving about 500 ml of air in and out of lungs
(tidal volume)
MV = 12 breaths/min x 500 ml/ breath
= 6 liters/ min
Spirogram of Lung Volumes and
Capacities