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First teaching 2023

First exams 2025

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Recognising Tissues (CIE AS Biology)

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Recognising Tissues in the Gas Exchange System

Cartilage

  • The cartilage in the trachea has a ‘glassy’ appearance due to its translucent protoplasm
  • It contains no nerves or blood vessels

Cartilage micrograph diagram

Cartilage micrograph

Cartilage micrograph, similar to that found in the gas exchange system

Cartilage SEM diagram

Cartilage SEM

Electron micrograph of cartilage tissue

Ciliated epithelium

  • Ciliated epithelial cells are distinctive due to their narrow cell bodies and hair-like cilia located along the apical layer
  • The cilia are tiny projections which greatly increase the surface area of the cell

Ciliated epithelium photomicrograph diagram

Ciliated Epithelium Photo Micrograph

Photomicrograph of a ciliated epithelium tissue in the gas exchange system

 

Ciliated epithelium electron micrograph diagram

Ciliated Epithelium Electron Micrograph

Electron micrograph of a ciliated epithelium tissue in the gas exchange system

Goblet cells

  • Goblet cells can be found scattered among the ciliated epithelium of the trachea and bronchi
  • They are distinctive in the epithelium due to their lack of cilia (although they still have some microvilli projecting outwards)
  • The nucleus is found towards the basal (bottom) layer of the cell, with a large Golgi apparatus and mucus granules found towards the apical layer

Light micrograph of some goblet cells diagram

Goblet Cell Light Micrograph

Light micrograph showing goblet cells as they would be found in the gas exchange system

 

Electron micrograph of some goblet cells diagram

Goblet Cells Electron Micrograph

Electron micrograph showing goblet cells as they would be found in the gas exchange system

Squamous epithelium

  • Squamous epithelium is made of thin, flat squamous cells

Light micrograph of the squamous epithelium diagram

Squamous Epithelium Light Micrograph

Light micrograph showing the squamous epithelium as it would be found in the gas exchange system

 

Electron micrograph of the squamous epithelium diagram

Squamous Epithelium Electron Micrograph

Electron micrograph showing the squamous epithelium as it would be found in the gas exchange system

Smooth muscle

  •  The cells of smooth muscle are tightly packed and are found beneath the ciliated epithelium
  • Unlike skeletal muscles, they are not striated and so don’t show any cross stripes under a microscope

Light micrograph of the smooth muscle diagram

Smooth Muscle Light Micrograph

Light micrograph showing the smooth muscle as it would be found in the gas exchange system

 

Electron micrograph of the smooth muscle diagram

Smooth Muscle Electron Micrograph

Electron micrograph showing the smooth muscle as it would be found in the gas exchange system

Capillaries

  • Capillaries are distinctive from other blood cells due to their tiny diameter (~4 μm)
  • Their walls consist of a single layer of epithelial cells

Light micrograph of capillary tissue diagram

Capillary Photomicrograph

Light micrograph showing the capillaries as they would be found in the gas exchange system

 

Electron micrograph of the capillaries diagram

Capillary Electron Micrograph

Electron micrograph showing the capillary tissue as it would be found in the gas exchange system

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Emma

Author: Emma

Expertise: Biology

Prior to working at SME, Emma was a Biology teacher for 5 years. During those years she taught three different GCSE exam boards and two A-Level exam boards, gaining a wide range of teaching expertise in the subject. Emma particularly enjoys learning about ecology and conservation. Emma is passionate about making her students achieve the highest possible grades in their exams by creating amazing revision resources!