1. CH 22 Lower Respiratory Anatomy
James F. Thompson, Ph.D.

2. The Lungs Apex, base Left lung has cardiac notch
R lung thicker, broader, shorter than L

3. The Lobes of the Lungs Lobes are separated by fissures
Each lobe has a secondary bronchus and tertiary bronchi
10 tertiary bronchi/lung
tertiary bronchi supply each bronchopulmonary (BP) segment
Tumors, infections or abscesses initially localized

4. The Lobules of the Lungs
Each bronchopulmonary segment has elastic connective tissue around a lymphatic vessel, an arteriole, a venule, and the terminal bronchiole
Terminal bronchiole continues to branch
Respiratory bronchiole  Alveolar duct  Alveolar sac  Alveoli

5. The Alveoli of the Lungs
Alveolar ducts open into alveolar sacs & alveoli
Alveolar sacs - 2 or more alveoli
Thin walls
simple squamous epithelium
thin elastic basement membrane
capillary endothelium
~300 million alveoli
Total surface area 1/2 to 2/3’s of a tennis court covered by ~1 liter of blood!

6. The Alveolus 2 cell types in walls
type I alveolar pulmonary epithelial (squamous) cells
Make ACE
type II alveolar or septal cells
secrete surfactant alveolar fluid
(detergent-like substance)
Alveolar macrophages (“dust cells”) patrol the alveolar walls

7. Alveolar-capillary (respiratory) interface
The Alveolar Wall
Capillaries (endothelial cells) surround alveoli for gas exchange
Smooth muscle controls airway resistance
Alveolar-capillary (respiratory) interface

8. Alveolar-capillary (respiratory) interface
The Alveolar Wall
Alveolar-capillary (respiratory) interface O2
CO2
Interface consists of:
Alveolar epithelium
Epithelial basement membrane
Capillary basement membrane
Endothelial cells of capillary
Total thickness
0.5 µm
short diffusion distance

9. The Alveolar Space Alveolar fluid
Surface tension
Attraction of water to other water molecules
Surfactant: phospholipids decrease surface tension
Respiratory distress syndrome

10. Blood Supply for the Resp. System
Pulmonary circulation
blood for gas exchange
low pressure system - 25/6 mm Hg
Bronchial (systemic) circulation
a small supply from the aorta for nutrients and O2
supplies entire lung (except alveoli)
high pressure system
bronchial arteries to bronchial capillaries, then to both pulmonary veins and bronchial veins
Pulmonary plexus
Area of root where nerve fibers enter lung
Sympathetic/parasympathetic/visceral sensory

11. The Pleura Lungs – housed in the bony thorax
Two pleural membranes with pleural cavity between
outer - parietal pleura
inner - visceral pleura
pleural cavity – lowered intraplural pressure is normal
Rib cage
protective and flexible

12. End CH 22: Lower Respiratory Anatomy