Tissue in the lungs

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  • Created by: Abby
  • Created on: 25-09-12 18:32

The Lungs

For air to reach the lungs, it must travel through the 3 main airways: Trachea, Bronchi, and Bronchioles.

The following requirements determine efficiency:

  • Larger airways must be exactly that, larger, so that the required volume of air can flow without obstruction
  •  These airways must divide into smaller airways to deliver air to alveoli
  • Must be strong enough so that when the pressure drops during inhalation, they don't collapse.
  • Must be flexible, to allow movement
  • Must be able to stretch and recoil.
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The Trachea and Bronchi

Have a similar structure. Different sizes (Bronchi narrower than Trachea).

Thick Walls - consist of several layers of tissue

  • Majority of wall is Cartilage( in form of incomplete rings/C-rings in Trachea, less regular in Bronchi)
  • Inside Surface of Cartiladge is a layer of Glandular Tissue, Connective Tissue, Elastic Fibres, Smooth Muscle and Blood Vessels. Often called 'Loose Tissue'


  • Inner Lining is an Epithelial layer: Majority (Cilliated Epithelial Cells), others Goblet Cells.
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The Bronchioles

  • Narrower than Bronchi,
  • Cartilage may be found in larger Bronchioles, none in smaller.
  • Walls made of mostly smooth muscle and elastic fibres


  • Smallest Bronchioles have alveoli at their ends
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Role Of Tissues


  • Structure (supports Trachea+Bronchi and prevents collapsing)
  • Incomplete ring so some flexibility -allows movement without constriction of airways

Smooth Muscle

  •  Contracts and narrows lumen (in bronchiole can restrict flow to&from alveoli*)
  • *Important if harmful substances are in air (not voulntary e.g asthma)

Elastic Fibres

  • when smooth muscle contracts, airway constricts-deforms elastic fibres-, as smooth muscle relaxes -elastic fibres recoil-. Helps to dilate (widen) airway
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Role Of Tissues ...Continued

Goblet Cells and Glandular Tissue

  • Secrete Mucas
  • Mucas traps tiny particles in the air e.g pollen, bacteria.
  • Removing reduces risk of Infection

Cilliated Epithelium

  • Epithelium consists of ciliated cells
  • Cilia- small hair like structures waft in synch to move Mucus to back of throat
  • Mucus swallowed- Stomach acid kills bateria
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