CH 22 Lower Respiratory Anatomy

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CH 22 Lower Respiratory Anatomy
James F. Thompson, Ph.D.
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The Lungs
apex
cardiac notch
base

• Apex, base
• Left lung has cardiac notch
• R lung thicker, broader, shorter than L

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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

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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

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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 2/3s of a tennis court
  covered by 1 liter of blood!

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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

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The Alveolar Wall

• Capillaries (endothelial cells) surround alveoli
  for gas exchange
• Smooth muscle controls airway resistance

Alveolar-capillary (respiratory) interface
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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

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The Alveolar Space

• Alveolar fluid
• Surface tension
• Attraction of water to other water molecules
• Surfactant phospholipids decrease surface
  tension
• Respiratory distress syndrome

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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

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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

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End CH 22 Lower Respiratory Anatomy