Download Respiratory System Chapter 15

Respiratory System
Chapter 15
The main function of the respiratory system is to
supply oxygen to, & eliminate carbon dioxide
from the body
In order to accomplish this task, the respiratory
system must work in conjunction with the
cardiovascular system
“Respiration” refers to the overall exchange of
gases between the atmosphere, blood & cells
Respiration involves 3 processes
 Pulmonary ventilation
 Gas exchange (gas diffusion)
 External respiration
 Internal respiration
 Gas transport
Anatomy Overview
Nasal cavity
Pharynx
Larynx
Trachea
The respiratory tract includes:
Nose (nasal cavity) Pharynx
(nasopharynx, oropharynx,
laryngopharynx) Larynx
Trachea Bronchi (primary,
secondary (lobar), tertiary
(segmental) Bronchioles
Terminal bronchioles  Alveolar
ducts Alveoli
Bronchi
Bronchioles
Respiratory
bronchioles
Right
Lung
Left
Lung
Alveolar duct
Alveoli
Histology
Respiratory Epithelium =
Pseudostratified Ciliated
Columnar (PSCC)
Nose (nasal cavity)
Air normally enters through external nares through nasal vestibule into nasal
cavity.
Functions of nasal cavity include: warming, moistening & filtering air; olfaction
Pharynx
Air passes from nasal cavity into nasopharynx, past oropharynx & through
laryngopharynx to larynx
Nasopharynx lined with PSCC epithelium, but oro & laryngopharynx lined with
stratified squamous epithelium
Larynx
Air passageway made of 9 pieces of cartilage – (1) Thyroid cartilage, (1) Epiglottis,
(1) Cricoid cartilage, (2) Arytenoid, (2) Corniculate, (2) Cuneiform
A.K.A your “voicebox” because it contains the vocal cords
 Thyroid cartilage – protects anterior & lateral walls of
airway
 Epiglottis – leaf-shaped cartilage that protects opening
(“glottis”) of airway when swallowing
 Cricoid cartilage – complete ring of cartilage; protects
posterior wall of airway; attaches to trachea
 Arytenoid, corniculate &
cuneiform cartilages –
attach to upper (false)
vocal folds & lower (true)
vocal cords
Trachea
 Tough but flexible “windpipe”, anterior
to esophagus
 attached to cricoid cartilage (at about
C6 vertebral level) & ends within
mediastinum by branching into left &
right primary bronchi (at T5 vertebral
level)
 End of trachea known as Carina
Carina
Trachea
 Lined with respiratory
epithelium
 “C”-shaped pieces of
hyaline cartilage
protecting airway while
allowing for swallowing
 Trachealis muscle
(smooth muscle) runs
across posterior wall of
trachea connecting ends
of tracheal cartilage
Bronchi
Carina
 Trachea splits into a left & right
primary bronchus which enters into
the hilus (hilum) of each lung
 Within the lung, the primary
bronchi branch into secondary
(lobar) bronchi (3 in right lung/2 in
left lung)
 Secondary bronchi then branch
into 10 tertiary (segmental) bronchi
 Tertiary bronchi then continue to
branch into smaller & smaller
bronchi & then into very narrow
bronchioles
This branching patterns creates
the “bronchial tree”
Changes In Airway
As you go further down into the bronchial
tree of each lung, changes in the airway
occur:
 increased number of airways (1 primary;
2 or 3 secondary; 10 tertiary bronchi; 6000
terminal bronchioles; millions of alveolar
ducts)
 decreased diameter of each airway
 decreased amount of cartilage in the
airways (no cartilage at all by terminal
bronchioles)
 increased amount of smooth muscle
(relative to diameter)
 lining epithelium changes from PSCC 
simple squamous epithelium (in alveoli)
Lungs
Located within the thoracic cavity,
surrounded by the double-layered pleural
membrane –
parietal pleura – lines cavity wall
visceral pleura – covers the lungs
Lungs- Anatomical Features
Apex – extends 1” above clavicle
Hilum – at medial surface;
where primary bronchus,
pulmonary artery & veins
enter/exit lung
Superior
lobe
Horizontal
fissure
Middle lobe
Superior lobe
Right
lung
Left
lung
Oblique
fissure
Oblique fissure
Cardiac notch
Inferior
lobe
Inferior lobe
Base – rests on diaphragm
Airways within Lungs
 Each lung has a primary
bronchus entering at the hilum
 Each lobe of a lung has a
secondary (a.k.a. lobar)
bronchus
 Lobes are functionally
divided into bronchopulmonary
segments & each segment has
a tertiary (segmental)
bronchus
 Segments are functionally
divided by elastic CT partitions
into many lobules & each
lobule receives a terminal
bronchiole
Relationship of Airways &
Pulmonary Vessels
 As airways branch within
lungs, they are accompanied
by branches of the pulmonary
artery (carrying de-oxygenated
blood into the lungs), &
branches of the pulmonary
veins (carrying oxygenated
blood out of the lungs)
 As the alveolar ducts
expand to form alveoli,
pulmonary arterioles will
branch to form a network
of pulmonary capillaries,
surrounding the alveoli
Alveoli
 Alveoli are expanded
chambers of epithelial
tissue that are the
exchange surfaces of the
lungs
 There are about 150
million alveoli in each lung
 Multiple alveoli usually
share a common alveolar
duct, creating “alveolar
sacs”
Alveoli
There are three types of cells
found within alveoli:
 Alveolar Squamous epithelial
(aka “type I”) cells – primary cells
making up the wall of the alveoli
 Septal (aka “type II”) cells –
sectrete “surfactant” to reduce
surface tension which prevents
alveoli from sticking together &
allows for easier gas exchange
 Alveolar macrophages (aka
“dust cells”) – phagocytic cells
that remove dust, debris &
pathogens
Gas “exchange” (external respiration) occurs across the
Respiratory membrane – the fused membranes of the alveolar
epithelium & the pulmonary capillary endothelium
Physiology of Respiration
“Respiration” refers to the overall exchange of
gases between the atmosphere, blood & cells
Respiration involves 3 processes
 Pulmonary ventilation
 Gas exchange
 External respiration
 Internal respiration
 Gas transport
Physiology of Respiration
Pulmonary Ventilation – “exchange” (movement) of gases
between the atmosphere & lungs; movement of gases
occurs because of pressure differences between the
atmosphere (atmospheric pressure (Po)) & lungs
(intrapulmonic pressure (Pi))
Two phases of ventilation:
 Inspiration
 active process involving contraction of diaphragm &
external intercostal muscles
 Expiration
 normally passive due to relaxation of above muscles
 can be made active (forced expiration) due to
contraction of abdominals & internal intercostal muscles
Pulmonary Ventilation
Lung Volumes & Capacities
Respiratory frequency (f) – number of ventilations
(inspiration+expiration) per minute

 Tidal volume (TV) - amount of air moved in or out of the
lungs during a normal breath
 Minute ventilation (VE=TV x f)- amount of air inhaled or
exhaled in one minute
Lung Volumes & Capacities (cont.)
Inspiratory reserve volume (IRV) – amount of air that
can be inhaled after a normal inspiration (above the resting
TV)

 Inspiratory capacity (IC = TV+IRV) – amount of air
inhaled after a normal expiration
 Expiratory reserve volume (ERV) – amount of air that
can be exhaled after a normal expiration
 Residual volume (RV) – amount of air remaining in lungs
even after maximal expiration
Lung Volumes & Capacities (cont.)
Vital capacity (VC=TV+IRV+ERV) – maximum amount of
air you can exhale, following a maximal inhalation

 Total lung capacity (TLC=TV+IRV+ERV+RV) –
maximum amount of air in your lungs, following a maximal
inhalation
Gas Exchange (gas diffusion)
 External respiration - the diffusion of O2 & CO2 between the alveoli &
blood across the respiratory membrane
 occurs because of pressure differences of each gas within alveolar
air & pulmonary (deoxygenated) blood
 results in creation of oxygenated blood
Gas Exchange
 Internal respiration – the diffusion of O2 & CO2 between the blood
& interstitial fluid across the endothelium of systemic capillaries
 occurs because of pressure differences of each gas between
systemic (oxygenated) blood & interstitial fluid
 results in creation of deoxygenated blood
Gas Transport - O2
 During external respiration O2 diffuses across respiratory membrane into
blood plasma
 The majority of O2 (98.5%) then immediately diffuses into RBCs & binds
(loosely) to the iron (Fe+3) in hemoglobin for transport
 only 1.5% is transported freely dissolved within plasma
Gas Transport – CO2
 During internal respiration CO2 diffuses from interstitial fluid into plasma
 Only 7% of CO2 remains in plasma for transport, the rest diffuses into RBCs
 Within RBCs 23% binds to the globin proteins of hemoglobin (Hb)
(“carbaminohemoglobin”)
 Most (70%) of CO2 gets converted within RBCs to bicarbonate ions (HCO3-) –
CO2 + H2O
H2CO3 (carbonic acid)
HCO3- + H+
HCO3- diffuses out to plasma (as Cl- diffuses in); the H+ attach to Hb to
maintain normal plasma pH (so plasma does not become too acidic)
Control of Respiration
Unconscious control of breathing occurs through the activity of the
respiratory centers of the brain
 Medulla oblongata – “Rhythmicity center” controls basic pattern of
breathing; inhale 2 seconds, exhale 3 seconds
 Pons – has 2 centers (apneustic & pneumotaxic centers) that can
unconsciously modify the rate & depth of respiration
Respiratory centers can be influenced by
mechanoreceptors (i.e. stretch receptors
in lungs) & chemoreceptors (sensitive to
CO2 levels, arterial pH, & O2 levels) in the
body, as well as by higher brain centers