Download CHAPTER 23

RESPIRATORY SYSTEM
As you recall from the chapter on metabolism - cells need oxygen to carry out the
process of ATP production - they also produce carbon dioxide as a waste product.
The main function of the respiratory system and circulatory system is to ensure that
enough oxygen reaches the tissues and that carbon dioxide is removed . The exchange of
gases between the atmosphere, the lungs, and the tissues is called respiration In order to
get oxygen to the tissues three processes are involved:
1. Pulmonary ventilation (breathing) is the exchange of gases between the
atmosphere and the lungs
2. External respiration is the exchange of gases between the lungs and the blood.
3. Internal respiration is the exchange of gases between the blood and the tissues.
Components
- Upper respiratory system
- nose, pharynx (throat) and associated structures
- Lower respiratory system
- larynx, trachea, bronchi, lungs
- functionally there are two divisions:
1. Conducting portion - cavities and tubes
2. Respiratory portion - where gas exchange occurs - bronchioles
alveolar ducts, and alveoli
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Nose
- two portions - an external and an internal portion
- the external portion consists of:
- the bone and cartilage framework with its mucous membranes that make up the
structure that protrudes from your face
- the two openings called the external nares or nostrils
- the internal portion of the nose (the nasal cavity) consists of:
- the large cavity bounded anteriorly by the external nose and posteriorly by
the opening into the nasal pharynx called the internal nares
- contains the nasal conchae and the openings to the paranasal sinuses:
- consists of four different sinuses (named after the bones they are in);
- Maxillary, Frontal, Ethmoidal, Sphenoidal (see figure above)
- Physiology
- the function of the nose is to:
- warm the air
- clean the air
- moisten the air
- the concha (turbinate bones) cause a vortex and also increase surface area
- they are covered with mucous, hair cells, and are very moist and highly
vascularized
- the superior nasal concha contains the olfactory region for smell and
pheromone reception
- between the concha are regions known as meatus
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Pharynx
- serves as an airway for the respiratory system and partially (oropharynx and
laryngopharynx) as a passageway for the digestive system
- 3 portions
(1) Nasopharynx
- above the soft palate
- openings to the eustachian tubes
- covered with pseudostratified columnar epithelium
- posterior wall contains the pharyngeal tonsils
(2) Oropharynx
- posterior to the mouth
- the opening between the oral cavity and the oropharynx is called the fauces
(3) Laryngopharynx
- stratified squamous epithelium
- is continuous with the esophagus
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Larynx
- the voice box
- connects the laryngopharynx with the trachea
- passageway for air going to and from the lungs
- consists of 9 pieces of cartilage held together with muscles and membranes
- the glottis is the opening through the larynx through which air passes. It is
covered by the epiglottis during swallowing
- voice production - 2 pairs of folds
(1) Ventricular folds
- uppermost
- false focal folds - not involve in sound production
- closes to prevent passage of foreign substances into trachea
(2) Vocal folds
- lowermost folds
- true vocal folds
sound production requires:
- vocal folds, pharynx, mouth, tongue, nasal cavity, sinuses
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Trachea
- 4.5 inches long
- divides into left and right primary bronchi
- histology - 4 layers
1. mucosa - pseudostratified columnar epithelium with lots of mucous cells
- traps dust and cila beats to transport mucous and dust into
laryngopharynx
2. Submucosa - contains the mucous glands
3. Cartilagenous layer 16 to 20 incomplete (c shaped) rings closed by trachealis
muscle and elastin
4. Adventitia - serosal layer
- carina
- ridge at junction of trachea/bronchi
- very sensitive - location of cough reflex center
Bronchi
- primary bronchi go to left and right lungs
- the right primary bronchi is more vertical , shorter, wider and more likely to
receive foreign objects
-each primary bronchi splits up into secondary bronchi - each goes to the lobe
of the lung:
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Lungs
- gross anatomy of the lungs
- base - sits on the diaphragm
- apex - rises above the clavicles
- hilus - where the bronchi and blood vessels enter
- cardiac notch - the scooped out area of the left lung where the heart fits
- lobes and fissures
- oblique fissure on left and right lungs
- horizontal fissure on right side only
- 3 lobes on the right - superior, middle, and inferior
- 2 lobes on the left - superior and inferior
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Alveolus (alveoli)
- air pockets
- lined with capillaries
- where gas exchange occurs
Alveolar Sacs - common space into which alveoli empty
Septal Cells - found in walls of alveoli - secrete surfactant to lower surface tension
so walls of the alveoli do not stick together if lung loses all its air.
Dust Cells (Alveolar Macrophages)
- phagocytes that remove debris
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Pulmonary Ventilation
- exchange of gases between the atmosphere and the lungs
- involves the movement of air (gases) due to pressure changes
Boyle's Law - the pressure of a gas in a closed container is inversely proportional to
the volume of the container
Inspiration
- the diaphragm is contracted and moves down (called deep or diaphragmatic
breathing) or the External Intercostal muscle pull the ribs upward and outward
(called eupnea or shallow breathing)
- either action above causes the volume inside the thorax to increase, thereby lowering
the intrapulmonary pressure (Boyle's law)
- the air moves from regions of high pressure (the atmosphere) to regions of lower
pressure (inside the lungs (intrapulmonary))
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Expiration
- diaphragm relaxes or gravity pulls ribs down (or internal intercostal muscles pull the
ribs down - in forced expiration)
- either action above causes the volume inside the thorax to decrease, thereby raising
the intrapulmonary pressure (Boyle's law)
- the air moves from regions of high pressure (inside the lungs) to regions of lower
pressure (the atmosphere)
Note: the intrapleural space is always subatmospheric so that the lungs adhere to the
parietal pleura
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Atelectasis (at-e-LEK-ta-sis)
- collapse of the lungs
- surfactant (a phospholipid) prevents the walls of the alveoli from remaining
in contact due to surface tension
- respiratory distress syndrome
- infants
- deficiency in surfactant
- can lead to CIDS
Compliance
- the ease with which the lungs and thoracic walls can be expanded
- related to:
- elasticity
- surface tension
- compliance decreases if:
- lung tissue is destroyed
- lung is filled with fluid
Pulmonary Volumes
Tidal Volume - quiet breathing, amount breathed in and out - about 500 ml
Anatomic Dead Space - amount of air in the respiratory tract that does not reach the
lungs - about 150ml
Minute Volume - the amount of air taken in - in one minute
Inspiratory Reserve - the amount of air that the lung can take in after a normal
inhalation
Expiratory Reserve - the amount of air the lung can breathe out after a normal
exhalation
Residual Volume - the amount of air left in the lungs after expiratory reserve
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Exchange of Respiratory Gases
Charle's Law - the volume of gas is directly proportional to its temperature
- means that the gas in the lungs expands due to warming
Dalton's Law - Each gas in a mixture of gases exerts its own pressure as if all
other gases were not present
Atmospheric Pressure = PO2 + PCO2 + PN2 + PH2O
- can be determined for each gas as follows:
- atmospheric PO2 = 21% X 760 mmHg = 160 mmHg
-atmospheric PCO2 = .04% X 760 mmHg = .3 mmHg
Henry's Law - the quantity of gas that will dissolve in a liquid is proportional to
the partial pressure of the gas and its solubility coefficient, when the temperature
remains constant
- the solubility coefficients of:
- CO2 = 0.57
- O2 = 0.024
- N2 = 0.01
- this means that CO2 can dissolve in blood but O2 and N2 cannot (unless the
partial pressure of that gas increases)
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Physiology of External Respiration
External Respiration - the exchange of gases between the alveoli of the lungs and
the blood in the respiratory capillaries
- results in: deoxygenated blood becoming oxygenated blood
NOTE: the gases diffuse down the concentration gradient
ALVEOLI
BLOOD
PO2 105 mmHg ----------------------------------------> PO2 40 mmHg
PCO2 40 mmHg <--------------------------------------- PCO2 45 mmHg
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Physiology of Internal Respiration
Internal Respiration - the exchange of gases between blood and the tissues
BLOOD
TISSUES
PO2 105 mmHg -----------------------------------------> PO2 40 mmHg
PCO2 40 mmHg <---------------------------------------- PCO2 45 mmHg
Transportation of Respiratory Gases
Oxygen
- does not dissolve in plasma
- combines with the heme portion of hemoglobin to form oxyhemoglobin
Carbon Dioxide
- each l00 ml of deoxygenated blood contains 4 ml of carbon dioxide
- 7% of this is dissolved in the plasma
- 23% combines with Hb to form carbaminohemoglobin
- 70% is transported in plasma as bicarbonate ions
Carbonic Anhydrase
CO2 + H2O <----------------------> H2CO3 <----------> H+ + HCO3
Carbonic
Bicarbonate
acid
ion
- the bicarbonate ions leave the RBC and enter the blood plasma
- in exchange Cl- ions diffuse from the plasma into the RBC and combine with K+
to form KCl
- in the lungs the opposite reactions occur to release the CO2 into the alveoli
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