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Lecture 22

ANP 1105 Lecture Notes - Lecture 22: Hemoglobin

Anatomy and Physiology
Course Code
ANP 1105
John Copeland

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Anatomy Lecture 22
Structural Characteristics of the Respiratory Membrane – we’re at Internal respiration
- Thickness of the membrane is about
- Type 1 cells are squamous epithelial (Type 1 is the dominant type in alveoli)
- Oxygen is carried in the serium of the blood, will diffuse through the ‘basement
of the cell and then through the vessel wall into the blood stream
- Pneumonia >>>>fluid uptake, increased thickness and decreasing rate of gas
- Surface area of the alveoli are huge, surface area of the lung is approx. 40 times
that of the skin, approx.. 140m^2 if healthy, large SA needed to carry out
diffusion. Emphysema, tumors, mucus and inflammatory material decrease this
area and inhibit effective oxygenation of the blood
Ventilation-perfusion coupling
- Regulated by local autoregulation
- It is the coupling between the amount of gas reaching the alveoli and the blood
flow in pulmonary capillaries
- Arterial diameter is based on PO2 (Partial pressure of O2): in alveoli where
veintialation is poor, PO2 is low and arterioles constrict>>>>blood redirected to
where PO2 is high (arterioles dilate)
- Bronchiole dimater is influenced by PCO2 (partial pressure of CO2): High
alveolar PCO2 causes bronchioles to dilate>>>>CO2 eliminated more rapidly;
where PCO2 low, bronchioles constrict
- When ventilation is less that perfusion, we have stale air in the alveoli. Arterioles
constrict which shunts blood away from the region of stale air to the region of
fresh air. Decrease in ventilation causes a decrease in perfusion
- Ventilation greater than perfusion, alveoli dilate, bronchioles involved. When we
dilate the alveoli we increase the transport capacity.
Partial pressure gradients are at work in internal and external respiration
In tissues, the oxygen partial pressure is approx. 40mmHg; this is in the interstitial
fluid. Arteriole pressure, PO2, is approx. 104mmHg. Causes it to move into the
tissue interstitial space where it is much lower
PCO2 in tissues is approx. 45mmHg and leaving tissues capillaries. Aprox. 40mmHg
in blood entering tissue capillaries.
Solubility of Oxygen vs. CO2 in plasma. CO2 is much high which evens out the
difference between pressures.
Internal and external respiration: diffusion is driven by partial pressure gradients
How Oxygen is carried in the blood?
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