Respiratory Mechanics
During inspiration, the diaphragm contracts. Explain the changes in thoracic volume, intrapulmonary pressure, and airflow.
Thoracic volume increases, intrapulmonary pressure decreases, and air enters the lungs.
Alveolar PO₂ is 104 mmHg, and pulmonary capillary PO₂ is 40 mmHg. Which direction does oxygen diffuse, and why?
From alveoli into blood because gases diffuse from high pressure to low pressure
A person smells their favorite food before eating. Why might their stomach begin secreting gastric juices before food arrives?
The cephalic phase activates neural pathways that stimulate gastric secretion in anticipation of food.
A person eats a piece of bread. Why does carbohydrate digestion begin before the food reaches the stomach?
Salivary amylase begins breaking starch into smaller carbohydrates in the mouth.
A patient with COPD has narrowed bronchioles due to inflammation and mucus accumulation. Explain why breathing becomes more difficult.
Narrowed airways increase resistance, reducing airflow and making ventilation more difficult.
A patient has narrowed bronchioles due to inflammation. What happens to airflow?
Airflow decreases because resistance increases.
Explain how CO2 is formed into Bicarbonate.
CO2 enters erythrocyte and binds with water to create bicarbonate and H+ ions. The H+ ions bind to the globin portion of hemoglobin and the bicarbonate exits the cell where a Cl- ion takes its place to ensure a neutral charge.
Food enters the stomach and causes its walls to stretch. How does this affect gastric secretion and motility?
Stretching activates neural reflexes and promotes gastrin release, increasing gastric secretion and motility.
A patient has damaged intestinal villi but normal digestive enzyme activity. Why might the patient still experience malnutrition?
Digestion may occur normally, but the reduced surface area prevents efficient nutrient absorption.
A patient experiences severe diarrhea for several days. They are now experiencing dehydration. Why?
Excess water remains in the intestinal lumen and is eliminated in feces instead of being absorbed into the body.
A patient breathes 15 times/min with a tidal volume of 400 mL. Calculate minute ventilation.
15 × 400 = 6,000 mL/min
6L/min
During exercise, skeletal muscle produces more CO₂ and becomes more acidic. How does this affect hemoglobin's affinity for oxygen? What type of shift is this?
Hemoglobin's affinity for oxygen decreases (right shift), allowing more oxygen to unload into active tissues.
A person eats a large meal rich in fat. As the meal enters the duodenum, stomach emptying slows. Explain why this is beneficial.
It gives the small intestine additional time to process and digest the incoming nutrients.
A patient has insufficient bile entering the duodenum. How would fat digestion be affected even if pancreatic lipase is functioning normally?
Without sufficient emulsification, less fat surface area is available for pancreatic lipase, reducing digestive efficiency.
A person has celiac disease. What does this mean?
Flattening of villi, malabsorption
A person's anatomic dead space is 150mL. Their alveolar dead space is 50 mL. What is their physiologic dead space? Is this person healthy or not?
200 mL. No a healthy person should not have any alveolar dead space.
Blood enters the pulmonary capillaries with a PO₂ of 40 mmHg, while alveolar PO₂ is 104 mmHg. As blood travels through the capillary, oxygen diffuses into it. At what point would net oxygen diffusion stop, and why?
When capillary blood PO₂ reaches approximately 104 mmHg. At this point, oxygen partial pressures are equal, and there is no longer a gradient driving net diffusion. This is diffusion equilibrium.
What do parietal cells secrete? What is important about their secretions?
HCl, but they produce the ingredients because producing HCl itself within the cell would destroy it. They also produce intrinsic factor which is important for vitamin b12 absorption.
Explain the flowchart starting with enteropeptidase in protein digestion
Enteropeptidase activates trypsinogen into trypsin. Trypsin then activates the other 3 (more trypsin, chymotrypsin, and carboxypeptidase)
A patient is stabbed in the chest. Why did they experience a pneumothorax?
The pleura must maintain a slightly negative pressure to keep the lungs inflated. If this pressure is made positive by a stab wound, the pressure would collapse the lung
Two patients have the same minute ventilation. One breathes rapidly and shallowly, while the other breathes slowly and deeply. Assuming equal dead-space volume per breath, which patient has greater alveolar ventilation, and why?
The slow, deep breather. A smaller proportion of each breath is wasted in anatomic dead space, allowing more fresh air to reach the alveoli per minute.
xygen and carbon dioxide must have equally large partial pressure gradients to diffuse at similar rates. Explain why this is incorrect.
CO₂ is approximately 20 times more soluble than oxygen, allowing it to diffuse efficiently despite a much smaller partial pressure gradient.
Acidic, fat-rich chyme enters the duodenum. Explain how CCK and secretin help coordinate digestion while preventing the stomach from overwhelming the small intestine.
CCK reduces gastric contractions and motility, while secretin reduces gastric secretions. Together, they help slow gastric activity while intestinal digestion proceeds.
Name which nutrients (carbs, lipids, proteins) are chemically digested at each part of the GI tract.
-Mouth
-Stomach
-Duodenum
-Rest of small intestine (brush border enzymes)
Mouth: Carbohydrates (salivary amylase)
Stomach: Proteins (HCl and pepsin) and lipids (activated lingual lipase, and gastric lipase)
Duodenum: ALL! Carbohydrates (pancreatic amylase) Proteins (Trypsin, chemotrypsin, carboxypeptidase) and Lipids (pancreatic lipase
Small intestine: Carbohydrates (maltase, lactase, sucrase) and Proteins (dipeptidase, and aminopeptidase)
A patient has severe anemia but normal lung function and normal arterial PO₂. Explain why the patient may still experience tissue hypoxia.
Arterial PO₂ reflects dissolved oxygen, but reduced hemoglobin limits the total oxygen-carrying capacity of the blood.