Physiology Post-Midterm Flashcards
How thin is the blood-gas barrier?
1/3 micron
What is the major principle of gas diffusion?
[pressure gradient]area/thicknessdiffusion coefficient
- diffusion coefficient = solubility/ sq(MW)
Which main stem bronchus is more vertical?
right
Type 1 alveolar cells
Main structural cell of alveoli
Type 2 alveolar cells
Produce surfactant
Alveolar macrophage
Ameboid motion, phagocytose
* No mucociliary elevator in the respiratory zone
What is an acinus?
Group of alveoli branching from a terminal bronchiole
What is the bronchial circulation?
Supplies blood to the conducting airways. Delivers deoxygenated blood into the pulmonary vein
What is a normal tidal volume?
500 mL
What is total ventilation?
Tidal volume x Respiratory frequency
How do you calculate alveolar ventilation?
P(expired CO2)/Arterial PCO2
Why does the partial pressure of oxygen decrease once inspired?
We humdify the air with gaseous water, thus PO2 becomes 149
Where is there convection vs. diffusion?
Convection: bulk flow
Diffusion: across capillary and into tissue
Where is there greater ventilation of the lung? Lower or upper region?
Lower region because of gravity
What is the relationship between anatomic dead space, breathing rate and alveolar ventilation?
Slower breathing rate combined with larger tidal volumes will maximize alveolar ventilation.
What is the equation for He-dilution FRC testing?
V1*(He in/He out -1)
What is the Band 3 protein?
Cl-HCO3 exchange transporter; takes place in peripheral RBC’s; offloading of HCO3 from Hb
Differentiate between Bohr and Haldane effects.
Bohr: reduced Hb affinity for O2 because high H+/CO2
Haldane: reduced Hb affinity for H+ because of high O2 partial pressure
A V/Q > 0.8
Results from “wasted” ventilation, or a PE; PCO2 drops
Bronchi constrict
A V/Q < 0.8
Results from an obstructed airway, or “wasted” perfusion.
Hypoxia-induced vasoconstriction
Where in the lung is there better ventilation and perfusion?
At the base of the lung; perfusion affect is stronger
Where in the lung are alveoli biggest at rest?
At the apex of the lung
What determines the rate of ventilation: size of alveoli or change in size of alveoli?
Change in size
Where in the lung is there both decreased pressure and increased resistance?
Upper zone; decreased pressure because of gravity; resistance in the lung is increased because capillaries are compressed by the large alveoli
What is LaPlace’s law?
P = 2T/R
- T = surface tension
- P = collapsing pressure
Surface tension in alveoli can cause 3 major problems
- Alveoli tend to collapse
- Large/small alveoli; small become underventilated, large become hyperventilated
- As alveoli collapse, they pull water in from blood – pulmonary edema
A high surface tension in the lungs leads to…
Stiff lungs, decreased compliance
* Atelectasis
At what week does synthesis of surfactant begin?
24th week
If a baby is born before 35th week, what might be a problem?
IRDS – not enough surfactant
What are 3 roles of surfactant?
- Reduce work of breathing
- Keep alveoli dry
- Opsonization
- Equalizes ventilation in adjacent alveoli
Smaller alveoli have more/less surfactant than larger alveoli?
More
Intracellular K+ will build up when what happens at the carotid body.
PO2 lower than normal
Cells at the carotid body depolarize with what type of ion influx: Na or Ca
Ca2+
What is the Herring Bruer reflex?
Lung stretch reflex
Where are the lung stretch receptors?
Smooth muscles in bronchi and bronchioles
Irritation receptors in the mucosal lining of the airways cause bronchodilation or constriction?
Constriction
Particularly with histamine
Pulmonary edema irritates what types of cells in the lung?
J cells (juxta-capillary) specially activated by pulmonary edema --> rapid shallow breathing * Dyspnea
What is the definition of “dynamic lung compliance”?
* A higher/lower airway resistance results in higher/lower dynamic lung compliance
For a given pressure, the change in volume
* Thus, a higher airway resistance, lower dynamic lung compliance
Which are perfusion-limited and diffusion-limited gases?
Perfusion: CO2, O2, N2O
Diffusion: CO
Under what conditions is CO diffusion capacity increased/decreased?
Decreased in PE, emphysema, fibrosis, anemia
Increased in exercise, polycythemia
Describe the 3 different zones of the lungs.
Zone 1: PA > Pa > Pv
Zone 2: Pa > PA > Pv - intermittent
Zone 3: Pa > Pv > PA - continuous
The exercising lung has increased/decreased resistance to blood flow. How does the lung increase/decrease its resistance?
Decreased; capillary recruitment & distension
O2 content is …
the actual amount of oxygen in ml per volume dissolved in blood; includes dissolved O2 and O2 in Hb
Differentiate between tense and relaxed Hb
Tense: de-oxy
Relaxed: oxy
2,3 BPG is increased in…
COPD, high altitude, anemia, shunts, emphysema
Where does the formation of bicarbonate take place?
In the RBC
How does bicarbonate leave the RBC?
Cl-shift
What is the Haldane effect?
Increasing Hb O2 saaturation reduces the CO2 concentration in the blood (opposite of Bohr effect)
What is pickwickian syndrome?
Chronic hypo ventilation and respiratory acidosis
T/F Deoxy-Hb is a good buffer
True
What is base excess?
Respiratory acidosis, compensated with bicarbonate excess
At a high altitude, is there compensatory base excess or base deficit?
Base excess
What is the equation for determining % of supplemental oxygen?
PAO2 = FIO2 - PACO2/0.8
How can you determine an anatomical shunt from other forms of hypoxemia?
Breathe 100% O2
Under what circumstances is the difference between PA o2 and Pa o2 increased?
Shunt, V/Q inequality, diffusion impairment
Dorsal/Ventral respiratory group neurons in MO
Dorsal: inspiration
Ventral: inspiration + expiration
Primary and secondary sensitivity of the glomus cell
Primary: low PO2
Secondary: PCO2, pH
The main driver of respiration centrally… (PO2 or PCO2)
PCO2
During the Valsalva maneuver,
Alveolar pressure > intrapleural pressure
An increased respiratory rate inc/dec dead space breathing
Increases (hence a decrease in alveolar ventilation)
Where in the lung is the intrapleural pressure most negative: apex or base?
Apex
Differentiate between Hb’s carrying capacity and affinity
Carrying capacity: anemia/polycythemia
Affinity: right/left shift
What is the alveolar ventilation equation (that doesn’t use CO2)
(TV-DS)*RR
Define proximal/distal with respect to the equal pressure point.
Proximal: mouth
Distal: towards alveoli
* EPP = PA = PIP
Which of the following is the correct spirometric term for the largest tidal volume that this patient can generate during the course of pulmonary function testing?
FVC
DKA, central/peripheral chemoreceptors, H+ or O2 or CO2
Peripheral; H+
Glucose, fat, protein digestion in the small intestine
Glucose, fat, protein –> Duodenum, jejenum, ileum
This feature of ____________ smooth muscle in the GIT enables tonic contractions.
Unitary; gap junctions
Differentiate between the submucosal and muscular plexuses in the GIT
Submocosal: Meisner’s plexus
Muscle: Myenteric (Auerbach’s)
Differentiate between absorption and secretion
Abs: apical Na in – Cl paracellular in
Sec: apical Cl out – Na paracellular in
The digestive enzymes (exocrine) of the mouth
Lingual lipase, alpha-amylase
The digestive enzymes (exocrine) of the stomach
Gastric lipase, pepsin
The digestive enzymes (exocrine) of the duodenum
Enterokinase, maltase, lactase
The digestive enzymes (exocrine) of the pancreas
Amylase, trypsin, chymotrypsin, PLA2, cholesterol esterase
The 4 layers of the GIT (histological)
Mucosa, submucosa, muscularis, serosa
Muscle contraction of smooth muscle is dependent on this enzyme….
Ca2+
Endocrine secretions of the stomach
Gastrin (G cells), somatostatin (D cells)
Exocrine secretions of the stomach
Pepsin, gastric lipase
Exocrine secretions of the mouth
Alpha-amylase, lingual lipase
Describe the 4 different types of exocrine cells in the stomach
Mucus surface/neck (mucus, HCO3, water)
Parietal/oxyntic (H+, Cl-, IF, H20) (only in body)
Cheif/peptic (lipase, pepsinogen)
Parietal cells are found only in this part of the stomach
Body
Where are the endocrine cells of the stomach?
Antrum (G+D)
What are the 4 stages of gastric motility?
- Fasting/MMC
- Meal –> vago-vagal reflex of fundus
- peristalsis (increased pressure)
- antral systole (retropulsion)
Describe gastric acid secretion
Na/K ATP-ase H+ proton pump Cl-HCO3 shift (alkaline tide) CO2 diffusion / carbonic anhydrase Na/H exchanger
The majority of gastric stimulation: interdigestion, cephalic, gastric, intestinal
Cephalic (30%) & gastric (50%)
Parietal cells are stimulated by …
Histamine (ECL cells), which are stimulated by gastrin and ACh (Gq, Gq)
Where are ECL cells found in the stomach?
Body
What receptors are present on parietal cells (4)?
H2, gastrin, ACh, SST
Oxyntic secretion of parietal cells is high in…
HCl
Describe the negative feedback of the stomach
1/2. Body/Antrum (H+ –> D cells –> SST –> parietal and ECL) ** parietal are not in antrum **
3. Small intestine (enterogastrones – secretin, CCK, GIP, VIP, pep YY, SST)
Chief cells are stimulated by…
ACh (neural and H+), secretin
Describe several aggressive factors against the integrity of the gastro-mucuosal barrier.
H+, pepsins, ETOH, NSAIDS, bile acids, ischemia
Endocrine/Exocrine panceras
Endocrine: insulin
Exocrine: trypsinogen, chymotrypsinogen
Describe the acinus/ductal aspects of a pancreatic exocrine gland
Acinus: low volume, enzymes
Ductal: high volume bicarb
The pancreas doesn’t digest itself because…
- Zymogen granules
- Enterokinase requirement
- Trypsin inhibitor
Is there an acid tide or alkaline tide in the exocrine pancreas?
Acid
CCK/Secretin/M3 on exocrine panceras
CCK: acinar
Secretin: ductal
M3: both acinar and ductal
Majority of pancreatic regulation occurs during this period of digestion
Intestinal (CCK, secretin, vagus)
What type of cells secrete secretin and bicarbonate?
S cells
Cells in zone 1 or 3 are more prone to ischemia in the liver?
Zone 3
The major regulator of the digestive phase of the gallbladder
CCK (20% ACh)
The bile flow rate changes based on: bile-dependent or bile-independent flow?
Bile-acid dependent
Components of bile
Bile salts, cholesterol, phospholipids, bilrubin, HCO3-
Function of bile
Emulsify fat, elimination of cholesterol, neutralize acid in duodenum
What duct delivers bile to/fro gallbladder?
Cystic duct
In a hepatocyte, which side is apical vs. basolateral
Apical: central vein
Differentiate between bile acid and salt
Salt more soluble (conjugated)
Differentiate between primary and secondary bile salts
Secondary are dehydroxylated by bacteria in intestines
Functions of liver
Bile/bilrubin Metabolism (vitamin D, t4-->t3) Proteins Immune (Kupfer) Endocrine (angiotensinogen) Detoxify
