Recognising Tissues (Cambridge (CIE) A Level Biology): Revision Note

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

Ciliated epithelium

• Ciliated epithelial cells are distinctive due to their:

  • Narrow cell bodies

  • Hair-like cilia located along the apical layer

• The cilia are tiny hair-like projections that beat to sweep mucus (with trapped dust and pathogens) up and away from the lungs

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

• 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

Squamous epithelium of alveoli

• Squamous epithelium is made of thin, flat squamous cells

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

Capillaries

• Capillaries are distinctive from other blood vessels due to their tiny diameter (about 7 μm, roughly one red blood cell wide)

• Their walls consist of a single layer of epithelial cells