ch 22 quiz review Flashcards
alveolus
alveolus
is a pouch about 0.2 to 0.5 mm in diameter
alveolus
squamous type 1 alveolar cells
thin, broad cells
cover about 95%
alveolus
type II alveolar cells
round, cuboidal cells
covers 5%
alveolus
dust cells
macrophages that eat bacteria
most numerous of all cells in the lung
wander the lumens of the alveoli and the connective tissue between them
alveolus
each alveolus is surrounded by a
web of blood capillaries supplied by small branches of the pulmonary artery
alveolus
respiratory membrane
the barrier between the alveolar air and blood
consists of
* squamous alveolar cells,
* the squamous endothelial cell of the capillary
* and their shared basement membrane
henry’s law
henry’s law
states that at the air-water interface, for a given temp, the amount of gas that dissolves in the water is determine by its solubility in water and its partial pressure in the air
henry’s law
thus the greater the
- PO2PO2 in the alveolar air, the more O2O2 the blood picks up.
- And since blood arriving at an alveolus has a higher Pco2Pco2 than air, it releases CO2CO2 into the air.
- At the alveolus, the blood is said to unload CO2CO2 and load O2O2.
- Each gas in a mixture behaves independently; the diffusion of one gas does not influence the diffusion of another.
hemoglobin
hemoglobin does not unload the same amount of
oxygen to all tissues
hemoglobin
some tissues need more and some less depending on their
state of activity
hemoglobin
hemoglobin responds to such variations and unloads
more oxygen to the tissues that need it most
hemoglobin
when temp rises the oxyhemoglobin dissociation curve shifts to the
right
* in other words elevated temp promotes oxygen unloading
hemoglobin
active tissues are wamer than
less active ones and thus extract more oxygen from the blood passing through them
hemoglobin
active tissues also generate extra
CO2 which raises the H+ concentration and lowers the pH of the blood
hemoglobin
hydrogen ions weaken the bond between
hemoglobin and oxygen and thereby promote oxygen unloading
* a phenomenon called the Bohr effect
this can be seen in the oxyhemoglobin dissociation curve where a drop in pH shifts the curve to the right
air that actually enters the alveoli becomes available for
gas exchange
* but not all inhaled air gets that far
anatomical dead space
- about 150 mL of it fills the conducting zone of the airway
- since this air cannot exchange gases with the blood
- typically about 1 mL per pound of bodyw weight in a healthy person
Systemic gas exchange
Systemic gas exchange
is the unloading of O2 and loading of CO2 at the systemic capillaries.
Systemic gas exchange
Oxygen Unloading
- When H+ binds to oxyhemoglobin (HbO2), it reduces the affinity of hemoglobin for O2 and tends to make hemoglobin release it.
- Oxygen consumption by respiring tissues keeps the PO2 of tissue fluid relatively low, thus the liberated oxygen diffuses from the blood into the tissue fluid.
Systemic gas exchange
Carbon Dioxide Loading
- Aerobic respiration produces a molecule of CO2 for every molecule of O2 it consumes.
- The tissue fluid contains a relatively high Pco2, thus CO2 diffuses into the bloodstream.
- Most of it reacts with water to produce bicarbonate and hydrogen ions
Systemic gas exchange
chloride shift
An antiport called the chloride-bicarbonate exchanger then pumps most of the HCO3− out of the RBC in exchange for Cl– from the blood plasma.
the automatic unconscious cycle of breathing is controlled by
3 pairs of respiratory centers in the reticular formation of the medulla oblongata and pons
ventral respiratory group (VRG)
the primary generator of the respiratory rhythm
dorsal respiratory group (DRG)
an integrating center that receives input from several sources
* respiratory center in the pons
* a chemosensitive center of the anterior medulla oblongata
* chemoreceptors in certain major ateries
* and stretch and irritant receptors in the airway
the DRG issues output to the
VRG that modifies the respiratory rhythm to adapt to varying conditions
furthermore each side of the pons has a
pontine respiratory group (PRG) that modifies the rhythm of the VRG
the pontine group receives input from higher brain centers including the
- hypothalamus
- limbic system
- cerebral cortex
- and issues output to both DRG & VRG
multiple sensory receptors also provide info to the
respiratory centers
central chemoreceptors
brainstem neurons that respond especially to changes in the pH of the cerebrospinal fluid
peripheral chemoreceptors
- located in the carotid and aortic bodies of the large arteries above the heart
- they respond to the O2 and CO2 content of the blood but most of all to ph
normally the systemic arterial blood has a
PO2 of 95 mm Hg
PCO2 of 40 mm Hg
pH of 7.40
systemic arterial blood
the rate and depth of breathing are adjusted to
maintain these values
systemic arterial blood
this is possible only because the
brainstem respiratory centers receive input from central and peripheral chemoreceptors that monitor the composition of the blood and CSF
systemic arterial blood
of these 3 chemical stimuli the most potent
stimulus for breathing is pH, followed by CO2; perhaps suprisingly the least significant is O2
systemic arterial blood
PO2:
PCO2
PO2: partial pressure of oxygen
PCO2: partial pressure of carbon dioxide
size of cell changes
the inner lining of the trachea is a
pseduostratified columnar epithelium composed mainly of mucus-secreting goblet cells, ciliated cells, and short basal stem cells
size of cell changes
the mucus traps inhaled particles and the upward
beating of the cilia drives the debris-laden mucus toward the pharynx where is it swallowed
this mechanism of debris removal is called the mucociliary escalator
size of cell changes
all of the bronchi are lined with
pseduostratified columnar epithelium but the cells grow shorter and the epithlium thinner as we progress distally
bronchioles
bronchioles have a
ciliated epithelium and a well-developed layer of smooth muscle in their walls
bronchioles
the terminal bronchioles have no
mucous glands or goblet cells
bronchioles
they do have cilia however
so that mucus draining into them from above can be driven back by the mucociliary escalator preventing congestion of the terminal bronchioles and alveoli
bronchioles
each respiratory bronchiole divides into
alveolar ducts which also have alveoli along their walls
bronchioles
the alveolar ducts and smaller divisions have
nonciliated simple squamous epithelia
