CH 22 Lower Respiratory Anatomy
James F. Thompson, Ph.D.
The
Lungs
apex
cardiac
notch
• Apex, base base
• Left lung has cardiac notch
• R lung thicker, broader, shorter than L
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
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
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!
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
The Alveolar Wall
• Capillaries (endothelial cells) surround alveoli for gas exchange
• Smooth muscle controls airway resistance
Alveolarcapillary
(respiratory)
interface
The Alveolar Wall
Alveolar-capillary (respiratory) interface
O2
•
Interface consists of:
1.
2.
3.
4.
CO2
•
Alveolar epithelium
Epithelial basement membrane
Capillary basement membrane
Endothelial cells of capillary
Total thickness
– 0.5 µm
– short diffusion distance
The Alveolar Space
• Alveolar fluid
– Surface tension
– Attraction of
water to other
water molecules
• Surfactant:
phospholipids
decrease surface
tension
• Respiratory
distress
syndrome
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
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
End CH 22: Lower
Respiratory Anatomy