Respiratory System b

Chapter 24

Lungs• Gas exchange organs• Delicate structure of Airways, Alveoli, capillaries• Right lung

– 3 lobes– Superior, middle, inferior

• Left lung– 2 lobes– Superior, inferior

• Cardiac notch accommodates heart• Located in separate pleural cavities

Lung Lobes

Lung

Alveoli Structure• 3 cell types• Epithelial Cells (type I)

– Simple Squamous• Alveolar macrophages

– Phagocytic WBC– Engulf inspired particles (dust)

• Surfactant secreting cells (Type II)– Secrete surface active agent– Surfactant

• Decreases intra-alveolar surface tension• Prevents alveolar collapse

Alveoli Structure

Type I

Exchange gas with capillaries

Type II aka Surfactant Secreting Cell

Regeneration & surfactant production

Surfactant Secreting Cell

Surfactant

Macrophages

Macrophages “Eat” Debris & Bacteria

Macrophages eating soot

Macrophage

Alveolar Pores

Alveoli Function

• Simple squamous epithelium• Provide favorable diffusion surface

– Small diffusion distance– Large surface area

• 300 million alveoli produce ~760 sq ft

• Contribute to respiratory membrane

Gas Exchange

• Gas exchange between air in alveoli & blood in capillaries

• High blood perfusion to lungs• Alveolar capillaries surround alveoli

Highly Vascularized

Alveolar Capillaries

Alveolar Capillaries

Respiratory Membrane

• 2 cell layers of simple squamous– Alveolar epithelial cells– Capillary endothelial cells

• Total diffusion distance– ~0.1 – 1.5 microns

• Efficient diffusion distance– Carbon dioxide diffuses into alveoli– Oxygen diffuses out of alveoli

Diffusion distance

Respiratory Membrane

Respiration• Breathing

– Cycle of inhalation & exhalation• Involuntary contraction of diaphragm• Driven by change in pressure• Body creates negative pressure in body

cavity• Regulated chemically

– Amounts of CO2 in blood stream

Respiration

• Ventilation– Movement of air in & out of lungs

• Systemic respiration– Exchange of gas between inhaled air & blood

• Cellular respiration– Cell use of O2 to make ATP

Ventilation• Involves changes in pressure to move air in &

out• Respiratory muscles• Diaphragm

– Increases volume of thoracic cavity by “dropping” floor • External intercostal

– Elevate ribs expanding chest cavity• Internal intercostal

– Depress ribs to reduce volume of thoracic cavity

Diaphragm

Diaphragm important in respiration

Muscles Associated with Breathing

Serous membranes

• Parietal pleura– Lines pleural cavity

• Visceral pleura– Covers lung

• Ventilation– Movement of chest wall– Membranes adhere to each other– Movement of chest wall “pulls” lungs open

Serous Membranes

Serous membranes adhere via cohesion

Respiration• Inhalation

– Rib cage expands- increases volume– Diaphragm contracts- increases volume– Creates negative pressure in lungs– Air rushes in

• Exhalation– Rib cage contracted- decrease volume

• Internal intercostals contract• Inhalation muscles relax

– Diaphragm relaxes- decrease volume– Increases pressure IN lungs – Air rushes out

Inhalation

Exhalation

Respiration

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Systemic Respiration

• Exchange of gas across respiratory membrane

• Passive transport down concentration gradient

Neural control

• Blood gas levels monitored by breathing control centers

• Adjust breathing to meet body’s needs

Smoking & You

Smoking is the leading cause of death in America

Lung disease

• Lining of respiratory surface- delicate• Molecules bind & impair function• Protected by

– Mucus– Cilia

• Lung cancer• Emphysema

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Emphysema

• Alveoli over-inflate because of a breakdown of alveolar walls

• Resulting decrease in respiratory function• 3 million Americans

– 15th most common chronic condition• Leading cause

– Cigarette smoking

Emphysema

Emphysema

Smoking is BAD!

Smoking Results in all kinds of BAD days!

Don’t Despair…

Pollution and Your Lungs

• http://www.cleanair.utah.gov/SWF/lung_control.swf