Billy Staggs Cahill
Onondaga Community College
Notes by: Billy Staggs Cahill
Respiratory and Urinary (Renal) Systems
When we think of the respiratory and urinary systems, we think of only breathing and urination. However, these systems are not so simplistic! There’s many cycles and functions, that are vital for human life.
Let us take a deeper look beginning with the respiratory system:
The conducting portion of the respiratory system carries air to the lungs.
Gas exchange occurs in the alveoli.
O2 and CO2 are transported using different mechanisms.
Air is inhaled actively and exhaled passively.
Breathing rate is controlled by the RESPIRATORY CENTER of the brain.
Assuming that you already know most of the basics of the respiratory system, let us take an extensive look into gas exchange:
The alveoli of the respiratory zone, is the site where gas exchange occurs.
Note: The PCO2 is noted here, because the process is cyclic, as we know.
Diffusion of O2 occurs at a PO2 104 (give or take) → PO2 100, and PCO2 46 → PCO2 40. The O2 will then travel in the bloodstream via Hb (hemoglobin) / pulmonary circuit.
The RBC will reach the tissues, and the PO2 has equilibrated to PO2 104 and will diffuse into the tissues: PO2 104 → (PO2 40, inside tissue). Coming from cellular respiration, is the CO2, which is waste. It will have a PCO2 46 → (PCO2 40, inside RBC).
As we know, there’s three ways CO2 is transported to the lungs / alveoli:
- 70% is transported buffered with water as carbonic acid.
- 20% CO2 bound to proteins, particularly Hb.
- 10% via plasma.
Pick up CO2 → CO2 + H2O (H2O from RBC) → H2CO3 (carbonic acid) → HCO3 and H+Hb (Hb in RBC)
Note: HCO3 diffuses into plasma
CO2 → CO2 + Hb (Hb in RBC)
CO2 → CO2 in plasma
Arrival at alveoli
HCO3 diffuses back into RBC
H+Hb → H → Hb
H → HCO3 → H2CO3 → CO2 and H2O
All CO2 diffuses into alveoli at a PCO2 46 → PCO2 40
All via systemic circuit / deoxygenated blood.
Our gas exchange is complete. The cycle will continue repetitively!
The next concept is the pleural cavity.
Note: These notes are abstract and review, and not in particular order.
Pleura is a serous membrane, that surrounds the lung, doubled layered:
parietal and visceral
parietal pleura is attached to the chest wall, and the visceral pleura covers the surface of the lungs.
Between these layers of pleura is a potential space; a space that doesn’t exist but it could exist, if something goes wrong.
There’s a small amount of fluid in this potential space, this serous fluid acts like a lubricant.
The purpose for the pleura is to move inside the body cavity without friction, as friction would cause damage to the lungs. The pressure inside the pleura membrane is – 4 mmHg, intrapleural pressure is 756 mmHg, as we know atmospheric pressure is 760 mmHg. The pressure keeps the lungs ‘stuck’ to the chest wall so they don’t collapse.
Ease at which lungs can be stretched . . . elasticity.
More ELASTIC → greater the compliance
surface tension of lungs
Greater tension → less compliant
distensibility of thoracic cavity: deformities of thorax, ossification of costal cartilages, paralysis of intercostal muscle – hinder thoracic expansion
- chronic inflammation, infections – scar tissue – fibrosis.
- decrease of surfactant.
Spirometry Measurements :
PULMONARY FUNCTION TEST
Vt – tidal volume – normal respiratory cycle
IRV – inspiratory reserve volume – after a normal inspiration
ERV – expiratory reserve volume – after a normal expiration
RV – risidual volume – after maximal exhalation
Why is a PFT given?
To test your lung function before surgery. To help diagnose lung conditions or diseases such as asthma, emphysema, chronic bronchitis, or pulmonary fibrosis. To check the extent of lung disease or to help explain new breathing symptoms. To find out if your breathing medicine is working.
Diffusion capacity/DLCO tests
This test determines how well the oxygen in your lungs is able to move to the bloodstream. You will be asked to keep a tight seal on a mouthpiece with a clip on your nose and breathe normally. After several breaths, you will take in as deep a breath as possible and blow it out slowly. You will keep blowing out until you are told to take a deep breath in and hold it for 10 to 15 seconds. Then, you will blow out again through the mouthpiece.
Taken from UPMC, life changing medicine.
4200 female capacity
6000 male capacity
Acidosis and Alkalosis
Acidosis – abnormal physiological state characterized by a plasma PH below 7.35.
Alkalosis – A condition of a plasma PH above 7.45; deficiency oh hydrogen ions or an excess of bicarbonate ions.
Respiratory response to acidosis –
Increased respiratory rate lowers PCO2 effectively converting carbonic acid molecules to water.
H2CO3 → H2O
Respiratory response to alkalosis –
Decreased respiratory rate elevates PCO2 effectively converting CO2 molecules to carbonic acid.
CO2 → H2CO3
Renal response to acidosis –
Kidney tubules respond by secreting H ions, removing CO2, Reabsorbing HCO3 to help replenish bicarbonate reserves.
Renal response to alkalosis –
Kidney tubules respond by conserving H ions and secreting HCO3.
Factors Controlling Glomerular Filtration:
55 mm Hg – (30+15)
55 mm Hg – 45 mm Hg
= 10 mm Hg
If at ZERO = No Filtration