Think About It

How would the movement of mucus in the respiratory tract be affected if cilia were equally stiff on both their power and recovery strokes?

10cilium = eyelash

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

3. Cellular Form and Function

Text

© The McGraw-H Companies, 2003

Microtubules And Microfilaments

Glycocalyx

- Plasma membrane

Actin microfilaments

Actin microfilaments

Cytosol

Cilia

Microvilli

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Cilia

Microvilli

Microtubules And Microfilaments

Peripheral microtubules

Central microtubules

Dynein arms

Peripheral microtubules

Central microtubules

Dynein arms

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Shaft of cilium

Dynein arms Central microtubules Peripheral microtubules s

Axoneme membrane

s membrane

Third microtubule of basal body terminates at cell surface

Plasma

Microvilli And Cilia

Figure 3.11 Microvilli and Cilia. (a and b) Electron micrograph and diagram of microvilli in cross section. (c and d) Electron micrograph and diagram of cilia in cross section. (e) Three-dimensional structure of a cilium at the point where it meets the cell surface.

Third microtubule of basal body terminates at cell surface

Plasma

Figure 3.11 Microvilli and Cilia. (a and b) Electron micrograph and diagram of microvilli in cross section. (c and d) Electron micrograph and diagram of cilia in cross section. (e) Three-dimensional structure of a cilium at the point where it meets the cell surface.

Saladin: Anatomy & I 3. Cellular Form and I Text I © The McGraw-Hill

Physiology: The Unity of Function Companies, 2003 Form and Function, Third Edition

Chapter 3 Cellular Form and Function 105

Cilia could not beat freely if they were embedded in sticky mucus (see insight 3.2). Instead, they beat within a saline (saltwater) layer at the cell surface. Chloride pumps in the apical plasma membrane produce this layer by pumping Cl_ into the extracellular fluid. Sodium ions follow by electrical attraction and water follows by osmosis. Mucus essentially floats on the surface of this layer and is pushed along by the tips of the cilia.

Mechanical Organisms

Figure 3.12 Cilia of the Trachea. Several nonciliated, mucus-secreting goblet cells are visible among the ciliated cells. The goblet cells have short microvilli on their surface.

Insight 3.2 Clinical Application

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