BIO211 Weekly Guide #6
RESPIRATORY
SYSTEM
After completing this laboratory you should be able to:
1) Identify the major divisions and structures of the respiratory system
2) Identify the lungs in gross anatomical models and histological section
3) Distinguish between conducting and respiratory passages in the respiratory tree
4) Recognize and characterize each level of the respiratory tree in histological sections
5) Fully characterize the epithelium lining each level of the respiratory tree
6) Recognize and describe the structure of the pleural sac, distinguishing between the visceral and parietal pleura
7) Identify the primary and accessory muscles of respiration and describe how each participates in inspiration and/or expiration
8) Identify the phrenic nerves and describe their function in respiration
9) Describe the CNS respiratory control system
10) Describe the standard respiratory volumes and how they are measured
Guide to Gross Anatomy Guide to Histology Guide to Physiology
Outline
I. Respiratory System Organization [FAP 23-1]
A. Conducting Division
functions
conduct, warm, humidify air, filter particles, supply olfactory system, voice
parts
external nares<-->nasal cavity<-->internal nares<-->nasopharynx<-->
oropharynx<-->larynx<-->trachea<-->bronchi<-->bronchioles
B. Respiratory Division
functions
exchange gases air<-->blood, accommodate for blood pH changes
parts
respiratory bronchioles<-->alveolar ducts<-->alveolar sacs<-->
alveoli<-->pulmonary capillaries
C. Lungs [FAP 23-5]
location - surrounding the mediastinum
structure
elastic C.T.
lobes (3 right, 2 left), segments, lobules
respiratory "tree"
conducting and respiratory passages
D. Circulatory systems
pulmonary [FAP Fig 21-18]
bronchial [FAP Fig 21-23]
E. Pleura [FAP 23-5]
visceral and parietal layers
fibrous and serous layers
pleural "space" and fluid
II. Conducting Division Structure
A. Nostrils [FAP 23-2]
location
structure
nasal bones, cartilaginous septum, alae, external nares
lining
stratified squamous epithelium
sebaceous & sweat glands
vibrissae
B. Nasal cavity [FAP 23-2]
boundaries
structure
septum, conchae (turbinates), meatuses, choanae(internal nares),
paranasal sinuses
lining - respiratory epithelium
olfactory epithelium
paranasal sinuses
C. Pharynx - 3 sections (only 2 are respiratory) [FAP 23-2]
nasopharynx
boundaries
features - Eustachian tube openings, pharyngeal tonsils
lining - respiratory epithelium
oropharynx
boundaries
features - shared with digestive system, palatine tonsils
lining - stratified squamous moist epithelium
laryngeopharynx - NOT part of respiratory system
D. Larynx [FAP 23-3]
boundaries
structure
9 cartilages - 4 hyaline & 5 elastic; 3 unpaired & 3 paired
thyroid, cricoid, epiglottis, arytenoids, corniculates, cuneiforms
2 pairs vocal cords - "true" and "false"
muscles
lining - respiratory epithelium, except superior epiglottis and vocal cords
E. Trachea [FAP 23-4]
boundaries
structure
mucosa - respiratory epithelium, lamina propria, lymph nodules
submucosa - C.T., blood vessels, nerves, deep mucous glands
hyaline cartilage C-rings, smooth muscle (trachealis muscle)
adventicia - C.T.
F. Bronchi [FAP 23-4; Fig 23-9]
structure - similar to trachea
1o (--> lung) cartilage C-rings
2o (--> lobe) irregular cartilage plates
3o (--> segment) "
4o (--> lobule) "
G. Bronchioles [FAP 23-5]
structure - like small bronchi except:
no cartilage (all smooth muscle)
fewer goblet cells
epithelial transition to simple columnar ciliated, then simple cuboidal
terminal bronchioles - final branch of conducting portion
constriction --> asthma
III. Respiratory Division Structure [FAP 23-5; Fig 23-10]
A. Respiratory bronchiole
structure - simple cuboidal epithelium, some smooth muscle and fibers
B. Alveolar ducts
structure - simple cuboidal epithelium
C. Alveolar sacs and alveoli
structure - simple squamous epithelium
function - gas exchange
relationship to capillaries
cell types
type I alveolar - exchange
type II alveolar (septal) - surfactant production
dust cells - macrophages
endothelial - capillaries
IV. Respiratory Physiology [FAP 23-6]
A. Meanings of Respiration
cellular respiration
internal respiration
external respiratoion
ventilation
B. Pulmonary ventilation [FAP 23-7, Spotlight Fig 23-15]
negative pressure inspiration
inspiratory respiratory muscles
accessory inspiratory muscles
pleura
air embolism
pneumothorax
expiration
lung compliance
emphysema
active expiration
respiratory volumes and capacities [FAP Fig 23-16]
CNS control [FAP 23-10, Spotlight Fig 23-25]
carotid, aortic, and hypothalamic sensors
lung mechanoreceptors
brainstem nuclei
medullary rhythmicity centers
pontine pneumotaxic and apneustic centers
C. Pulmonary and peripheral gas exchange [FAP Fig 23-18]
concentration dependent
membrane diffusion processes
D. Gas transport [FAP 23-8, 23-9]
ideal gas laws
PV = nRT
Boyles's - pressure and volume
Charles's - volume and temperature
Dalton's - partial pressures
Henry's - solubility in a liquid, temperature and partial pressure
oxygen
hemoglobin Hb structure [FAP Fig 23-19 to 23-22]
hemoglobin saturation curves and responses
carbon dioxide and carbon monoxide interactions
carbon dioxide
binding to Hb [FAP Fig 22-22, 22-23]
bicarbonate buffer system and pH
role of carbonic anhydrase
Gross Anatomy List
Respiratory Structures:
Nose Trachea
external nares cartilage rings
alae bronchi
septum primary
vestibules secondary
vibrissae
Lungs
Nasal Cavity pleura
choanae (internal nares) parietal pleura
septum visceral pleura
turbinates base
meatuses apex
paranasal sinuses root (hilus)
bronchi
Nasopharynx pulmonary arteries
pharyngeal tonsil pulmonary veins
Eustachian tube openings lobes
Oropharynx Diaphragm
uvula crura
palatine tonsils vena caval foramen
esophageal hiatus
Oral Cavity aortic hiatus
hard palate nerves
soft palate vagus nerves- esp. recurrent branch
phrenic nerves
laryngeopharynx
esophagus
Larynx
hyoid bone
thyroid cartilage
cricoid cartilage
epiglottis
arytenoid cartilages
corniculate cartilages
cuneiform cartilages
true vocal cords
false vocal cords
thyroid gland
Key: Respiratory structures: Identify, know location and function
Related structures: Identify, know location and function
Guide to Gross Anatomy
[APL 22 Exercise 1]
Nasal Passageways [APL Fig 22.2, 22.4]
The nasal passageways consist of the nostrils, nasal cavity, and the paranasal sinuses. Besides providing passage for air, they filter and condition it, add resonance to the voice, and house the olfactory receptors.
a) Locate the following structures on the models, charts and (where appropriate) skeleton:
external nares nasal septum olfactory epithelium
alae conchae (turbinates) choanae (internal nares)
vibrissae meatuses
- What kinds of cartilage are found in the nostrils? What is the function of the vibrissae?
- Note that the nasal septum that it is formed of three component vertical plates - one cartilaginous and two bony. What two bones contribute to the septum? Do you think that it is more correct to speak of the nasal cavity or cavities?
- Note the location of the olfactory epithelium on the roof of the nasal cavity, superficial to the cribriform plate of the ethmoid bone. More on this in a later week.
- Note on the skull the three small spiral shelves projecting from each lateral wall of the nasal cavity - the superior, middle, and inferior conchae (turbinates). From which bone does each of these arise? The conchae are covered with a small amount of highly vascular connective tissue and respiratory epithelium. What is the function of these structures? Note that each turbinate overhangs a partially enclosed channel, or meatus.
b) The paranasal sinuses are hollow cavities, lined with respiratory epithelium, in five of the bones surrounding the nasal cavity. They communicate with the nasal cavity via passageways which open into the meatuses. On the models identify the following:
frontal sinuses ethmoid sinus
maxillary sinuses sphenoid sinus
- Note that the nasolacrimal canal also opens into the nasal cavity. What is the function of this canal?
Pharynx [APL Fig 22.2, 22.4]
The pharynx is a muscular tube extending from the internal nares to the esophagus. It has three parts - the nasopharynx, the oropharynx, and the laryngeopharynx. It is important to recognize that the nasopharynx is a respiratory passage, the laryngeopharynx is a digestive passage, and the intervening oropharynx is shared by the respiratory and digestive systems.
a) On the models and charts identify the three regions of the pharynx.
b) Locate the openings of the Eustachian tubes on the lateral walls of the nasopharynx.
- Where do these tubes lead and what is their function?
c) Locate the pharyngeal and palatine tonsils. If necessary review the structure and function of the tonsils from last week.
Larynx [APL Fig 22.5]
The larynx extends from the oropharynx to the trachea. It is constructed around the hyoid bone and 9 cartilages - 3 unpaired and 3 paired; 4 hyaline and 5 elastic. The intrinsic musculature regulates the glottis and the vocal cord tension.
a) Locate the following unpaired cartilages on the models and charts:
thyroid cricoid epiglottis
Locate the following paired cartilages on the models:
arytenoids corniculates cuneiforms
- Which cartilages are hyaline and which are elastic cartilage?
- Palpate the anterior aspects of the cricoid and thyroid cartilages and the hyoid bone. Note that the laryngeal prominence ("Adam's apple") of the thyroid cartilage is much more pronounced in the male. What hormone is responsible for promoting development of this "secondary sexual characteristic"
b) Study the locations and actions of the following intrinsic laryngeal muscles on the models and charts:
posterior cricoarytenoid lateral cricoarytenoid cricothyroid
c) Locate the vestibular (quadrangular) membranes and the cricothyroid membrane (conus
elasticus).
d) Locate the vocal folds (true vocal cords), the ventricular folds (false vocal cords), and the ventricle between them. Note that the true vocal folds regulate the size of the glottis, or entrance to the larynx.
e) Locate the recurrent branch of the vagus nerve bilaterally on the charts and models (if possible). It is the motor innervation of the larynx, and thereby controls the size of the glottis.
- What would the consequences be of bilateral damage to this nerve?
Bronchial Tree [APL Fig 22.5]
The bronchial tree completes the conducting portion of the respiratory passages by ramifying out into the lungs.
a) Locate the trachea on the models and charts. It extends from the inferior margin of the larynx (vertebral level C6) to its bifurcation in the mediastinum (vertebral level T5). What is the muscular tube which runs just posterior to the trachea? What is the function of the gap in the C-rings of cartilage which hold the trachea open?
b) Study the branching bronchial tree in the models and plasticized sheep lungs. The tree consists of the trachea, 2 primary (1o) bronchi, 5 secondary (2o) bronchi, etc. Pay specific attention to the orientation and relative sizes of the right and left primary bronchi.
- Note that the branching of the bronchi parallels the lobulation of the lung, that is, successive "generations" of bronchi correspond exactly to successively small divisions of the lung:
1o bronchus ---- lung
2o bronchus ---- lobe
3o bronchus ---- segment
4o bronchus ---- lobule
Lungs [APL Fig 22.3]
The lungs consist of the distal portion of the conducting pathway, the alveolar surface for gas exchange with the pulmonary capillaries, as well as the larger vessels of the pulmonary and bronchial circulations, all imbedded in fibroelastic connective tissue.
a) Study the models and prepared lungs. Locate the following structures and regions:
apex inferior border fissures
base root lobes
hilus
- Use the following criteria to distinguish the right and left lungs:
# of lobes
size of the cardiac impression
orientation of the gap in the bronchial C-rings
- Study the hilus region of each prepared lung (if available). The large structures of the root are the bronchi, pulmonary arteries, and pulmonary veins. Be able to distinguish these structures. The following criteria may help:
bronchi - round X-section, thick walls, cartilage C-rings, wide lumen
arteries - round to oval X-section, thin walls, narrow lumen
veins - oval to irregular X-section, very thin walls, wide lumen
- The pulmonary arteries have much thinner walls than do the major systemic arteries. Why?
b) Note that the relationship of each lung to its pleura is analagous to the relationship of the heart to the pericardium. Locate the visceral and parietal layers.
Mechanical Respiration
The term respiration refers to four very distinct processes: 1) the mechanics and control of inspiration and expiration, 2) the exchange of gases across the alveolar-capillary interface, 3) the exchange of gases across the capillary/tissue interface, and 4) the cellular process whereby sugars are oxidized to form carbon dioxide and water. With reference to meaning 1 above:
a) Review the thoracic musculature involved in respiration. What additional muscles function as "accessory" respiratory muscles in forced respiration or respiratory distress? What is the function of the elasticity of the lungs in relaxed breathing?
b) Locate the phrenic nerves on the charts. What muscle does each phrenic nerve innervate?
c) Why is the pleural fluid essential to efficient lung function? What are the consequences of a severe pneumothorax (entry of air into the pleural cavity)?
Guide to Histology
[APL Exercise 22-2]
Respiratory System
After working through the respiratory slides, you should be able to define and distinguish between the following successive divisions of the respiratory tree: trachea, primary bronchi, secondary bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. In addition you should be able to define: respiratory epithelium, types I & II alveolar cells, surfactant, dust cells, and capillary endothelial cells. We will not deal directly here with the nasal, pharyngeal, and laryngeal passages, although you should be able to describe the type of epithelium found in each region.
a) Trachea [APL Fig 22.8]
The tracheal wall has 4 layers: mucosa, submucosa, cartilage rings and smooth muscle, and adventitia.
- Identify the four layers of the tracheal wall.
- Identify the pseudostratified columnar epithelium with cilia and goblet cells. This is often called simply "respiratory epithelium". What do the goblet cells do?
- Can you find any lymphoid aggregations (nodules) in the tracheal wall? In what part of what layer would you expect to find these? Try also to identify the deep mucous glands of the submucosa.
- Note the C-shaped rings of hyaline cartilage What is their function? What is the function of the trachealis muscle which bridges the gap in the cartilage C-rings?
b) Lungs [APL Fig 22.9, 22.10]
In the deeper portions of the respiratory system, there are progressive changes in the epithelium and wall of the airways. In primary bronchi, C-shaped rings of cartilage break up into plates, and the cartilage support becomes more and more fragmentary in the secondary and tertiary bronchi. The epithelium changes progressively, first having fewer goblet cells (primary bronchus), then becoming simple columnar (secondary and tertiary bronchi).
At the level of bronchioles, hyaline cartilage disappears. Goblet cells completely disappear at the level of terminal bronchioles. Cilia also begin to disappear; they are present in terminal bronchioles, but absent from respiratory bronchioles. The simple columnar epithelium flattens to cuboidal at the level of terminal and respiratory bronchioles, then becomes squamous in the alveolar sacs. Smooth muscle fibers are seen in the walls of respiratory bronchioles and alveolar ducts, but not in the alveolar sacs or alveoli.
- Scan these slides to identify, where possible: alveoli, alveolar sacs, alveolar ducts, respiratory bronchioles, terminal bronchioles, bronchioles, bronchi, and branches of the pulmonary arteries and veins.
- On high power try to distinguish type I and type II (septal) pneumocytes, and dust cells (macrophages) in the alveoli. What is the function of each of these cell types?
- Compare the sections of normal and coal miner's lungs. What kind of differences do you see? Try to identify the dust cells (macrophages) by the ingested carbon particles. If you are a 1-pack-a-day smoker, guess which lung sample more closely resembles your lungs.
Guide to Physiology
Modeling Lung Ventilation [APL Exercise 23-1]
Mechanical ventilation in humans, as in all mammals, operates as a negative pressure system. Follow exercise 1 in the laboratory text to model the action of the diaphragm and the effect on lung volume and the respiratory cycle.
Spirometry - Respiratory Volumes [APL Exercise 23-2]
A wet spirometer is used to measure the "classical respiratory volumes" - specifically tidal volume, inspiratory capacity, inspiratory reserve volume, expiratory capacity, expiratory reserve volume, and vital capacity. (Calculating the final relevant respiratory volume, residual volume or respiratory dead space, requires the additional monitoring of gas concentrations in inspired and expired air).
Use exercise 2 in the lab text, or the guide below, to measure, calculate, and record your own respiratory volumes.
1) Zero the spirometer by positioning the pointer and the slide together at the zero mark. Put a fresh mouthpiece in the spirometer hose. Sit down, get comfortable and breathe in a normal rhythm for at least 30 seconds.
2) Count the number of breaths you take in the next 30 seconds and multiply by 2 to determine your resting respiration rate. RR = bereaths per minute
3) After a normal, resting inspiration, place the mouthpiece between your lips and breath out in normal unforced manner. Record where the pointer stops, then slide the pointer back to the zero mark. Repeat this process twice more and average the three readings, this is the tidal volume. TV = liters
4) Resume unforced, resting breathing for at least 30 seconds. After a normal expiration, place the mouthpiece between your lips and forcibly exhale all the air possible. Record where the pointer stops, then slide the pointer back to the zero mark. Repeat this process twice more and average the three readings, this is the expiratory reserve volume. ERV = L
5) Resume unforced, resting breathing for at least 30 seconds. After a normal expiration, breathe in as deeply as possible, place the mouthpiece between your lips and forcibly exhale all the air possible. Record where the pointer stops, then slide the pointer back to the zero mark. Repeat this process twice more and average the three readings, this is the vital capacity. VC = L
6) Calculate the following additional respiratory volumes:
inspiratory reserve volume (IRV) = VC - (TV + ERV) IRV = L
inspiratory capacity (IC) = TV + IRV = VC - ERV IC = L
expiratory capacity (EC) = TV + ERV = VC - IRV C = L
minute volume (MV) = TV x RR x 1 minute MV = L
7) Weigh the yourself on the scale. Use your weight, and breath rate to determine a predicted basal tidal volume, using the graph on the table.
How do your predicted and actual tidal volumes compare?
What other information would you need to calculate the respiratory dead space?
Hemoglobin as a Respiratory Pigment
As you are probably aware, blood changes color depending on the degree of oxygenation. This is due to a color change as deoxyhemoglobin takes on oxygen to become oxyhemoglobin. This part of the lab will investigate and graphically demonstrate that change.
1) Obtain two 4 ml samples of sheep blood in 15 ml centrifuge tubes and label them #1 and #2.
2) Use the air line to gently bubble air through Sample #1 for two minutes. Reseal the tube when you are finished.
3) Use the CO2 line to gently bubble CO2 through Sample #2 for two minutes. Reseal the tube when you are finished.
4) Compare the color the blood in the two tubes. Do you see any differences in color between the two tubes? How does this correlate to the differences between oxy- and deoxyhemoglobin?
5) Set up 11 matched Sepc-20 tubes with 1ml RO water in each. Use the following procedure to produce abbreviated apsorption spectra for the two samples in the 400-460 nm range.
a) Set the Spec-20 to 400 nm. Zero the spec-20 and blank it with an RO water sample.
b) Using a pipetter transfer 20uL of blood from oxygenated Sample 1 to one of the Spec-20 tubes. Measure and record its absorbance.
c) Repeat steps a and b at 415, 430, 445, and 460 nm.
d) Repeat steps a, b, and c to produce a corresponding set of absorbance reading for the deoxygenated Sample 2.
6) Plot your two spectra on Excel so that the two plots superimpose.
The oxyhemoglobin spectrum should peak at 410 nm. The deoxyhemoglobin spectrum should peak at 430 nm. Do your results agree with this expectation/
Carbon Dioxide and pH [APL Exercise 23-3]
Most carbon dioxide is carried in the blood in the form of bicarbonate ion. The corollary of this is that the bicarbonate provides the primary buffering system which maintains blood pH at a fairly constant pH of 7.4 + 0.1.
The central reaction is: CO2 + H20 <-> H2CO3 (carbonic acid) <-> H+ HCO3- (bicarbonate)
Exercise creates CO2 as a waste biproduct and drives this reaction to the right, lowering blood CO2. The CNS respiratory control center responds to this falling pH by increasing the depth and rate of respiration. CO2 is removed from the blood in exhaled air, raising pH back towards 7.4.
Follow Exercise 3 in the lab text to study the effects of exercise on respiratory rate and expired CO2.