System Physiology Ch 13

Coronary Artery Disease (CAD)

• ↓ blood flow to heart (ischemia)

• Can lead to heart attack (myocardial infarction)

What Happens in CAD

Arteries supplying heart get blocked

heart muscle gets less oxygen
cells die

Heart Attack

• Chest pain

• Shortness of breath

• Tissue death

Middle-aged patient with chest pain during exercise

reduced blood flow to heart →
➡ CAD → possible heart attack

Alveoli (Gas Exchange Site)

2 Important Cells

• Type I cells → gas exchange

• Type II cells → make surfactant

• HUGE surface area → fast gas exchange

Damage to alveoli (smoking)

↓ surface area → poor oxygen exchange

3. Steps of Respiration

• Ventilation (air in/out)

• Exchange (lungs ↔ blood)

• Transport (blood carries gases)

• Tissue exchange

• Tissue use (cells use O₂)

• “Ventilate → Exchange → Transport → Tissue → Use”

Breathing Basics (Flow Rule)

Formula Idea

Flow = ΔPressure / Resistance

Air moves:

High pressure → Low pressure

3 Pressures

• Atmospheric (Patm) = outside air

• Alveolar (Palv) = inside lungs

• Intrapleural (Pip) = pleural cavity

• Pip must ALWAYS be negative

• Keeps lungs open

Lung Collapse

Atelectasis / Pneumothorax

• Air enters pleural space

• Pip = Palv
  ➡ lung collapses

Knife wound to chest → air enters pleural cavity

lung collapses → pneumothorax

Transpulmonary Pressure

Formula

keep lungs open:

Ptp​=Palv​−Pip​

• ↑ difference = lungs expand

• If difference lost → collapse

Boyle’s Law

Pressure ↑ → Volume ↓
Pressure ↓ → Volume ↑

“Big lungs = low pressure”

Inspiration (Breathing IN)

• Diaphragm contracts ↓

• Thoracic volume ↑

• Pressure ↓

• Air flows IN

• Muscles

  • Diaphragm

  • External intercostals

During exercise:

deeper inspiration using accessory muscles

Expiration

Quiet Expiration

• Passive (no effort)

• Lungs recoil

• Forced Expiration

  • Active

  • Uses abdominal + internal intercostals

Blowing out candles

forced expiration

Inspiration

Palv ↓ (below atmospheric)
➡ air enters

Expiration

Palv ↑
➡ air leaves

Pneumothorax

• Air in pleural space

• Lung collapse

Atelectasis

• Collapsed alveoli

• Causes:

  • blockage

  • loss of pressure

Blocked airway → alveoli collapse

atelectasis

CAD → Respiratory Link

Poor heart function → ↓ oxygen delivery

Heart attack → less oxygen to tissues

shortness of breath