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

The Lungs Apex, 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

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

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

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