Club cells, also known as Clara cells, are found in the respiratory bronchioles of the lungs. They secrete substances that line the airways and help metabolize inhaled toxins. Club cells also act as stem cells that regenerate ciliated cells of the lungs. Disorders of the lungs like COPD, pulmonary fibrosis, and lung cancer can involve abnormal club cells. Levels of proteins secreted by club cells can indicate lung damage and serve as biomarkers for lung diseases.

1. Presentation
on
Club Cell
Presented by-
ID-17VPhy-JJ14M
-17VPhy-JJ15M
Department of Physiology

2. Presentation Outlines
• Introduction
• Club cell
• Location
• Histology
• History of origin
• Functions
• Role in diseases

3. Introduction
The respiratory system of mammals is comprised of
two anatomical parts:
1. The conducting zone: trachea, bronchi and
bronchioles.
2.The respiratory zone: lung parenchyma proper
which consists of respiratory bronchioles, alveolar
ducts and pulmonary alveoli.

4. The epithelium lining of the primary airways includes
the following types of cells:
A. ciliated cells
B. goblet (or beaker) cells which produce and secrete
mucus
C. brush cells with numerous microvilli
D. undifferentiated basal cells
The respiratory bronchioles: forming the margin between
the conducting and respiratory zones .
A. ciliated cells (the most common)
B. microvillar cells (few)
C. small granule cells (few)
D. club cells or Clara cells (CCs)

5. pulmonary alveolar epithelium:
A. type I pneumocytes,
B. type II pneumocytes,
C.type III pneumocytes (rare),
D. numerous pulmonary macrophages.
Basal cell
Goblet cell Ciliated cell Brush cell
Small granule cell Club cell Microvillar cell
Type II
pneumocyte typeIII pneumocyte Macrophage
Type I
pneumocyte

6. What is Club Cell?
• Known as bronchiolar exocrine cells.
• Originally known as Clara cells.
• They are cubical & dome-shaped cells with short
microvilli and
• they do not have cilia or secrete mucus.
Location:
small airways (respiratory bronchioles) of the
lungs. Apart from lungs, in the human body, CCs
are also present in the gravid uterus, kidneys,
and prostate.

7. Histology:
smooth and rough endoplasmic reticulum.
A large number of mitochondria is present.
The Golgi apparatus is well developed.
The centrally located cell nucleus forms approx. 30% of
the cell.
Each cell also contains approximately 6 dense membrane-
coated granularities.
contains many nucleoli.
The secretory activity of CCs is stimulated by adrenergic
fibers.
apocrine and a merocrine mannered secretion.

8. History of Origin
Max Clara was an ardent Nazi supporter and discovered a
specific type of cells present in the bronchial epithelium;
the cells were initially called Clara cells, but are now
known as club cells (CCs) or bronchiolar exocrine cells.
The results of his studies were based on the examination
of lung samples acquired from prisoners murdered in
concentration camps around Dresden during world war II.

9. Fundamental functions:
• they secrete the primary components of the extracellular
substance lining the respiratory bronchioles,
• they are progenitor cells for both themselves and ciliated
cells,
• they regulate the contents of secretion (fluid) in the distal
segments of the respiratory tract,
• in the lungs, they play a key role in the biotransformation
of inhaled xenobiotics together with cytochrome P-450
and mixed-function monooxygenases.

10. Role in Diseases
Club cells contain tryptase, which is believed to be
responsible for cleaving the hemagglutinin surface protein
of influenza A virus, thereby activating it and causing the
symptoms of flu.
Malignant club cells are also seen in bronchioalveolar
carcinoma of the lung.
Serum club cell proteins are used as a biomarker of lung
permeability.
Airway epithelium is renewed, maintained, and repaired
primarily by endogenous stem cells (progenitor cells).
Bronchiolar CCs are believed to play a key role in the
regulation of pulmonary homeostasis and inflammatory
conditions (both acute and chronic).

11. However, it is believed that progenitor CCs participating in
the repair of airway epithelial damage. Some diseases are
listed below in which they take part in-
• mucoviscidosis (cystic fibrosis),
• ARDS,
• COPD,
• pulmonary fibrosis,
• pulmonary emphysema,
• pulmonary hypertension,
• subglottic tracheal stenosis,
• tracheomalacia

12. Club cells secrete various proteins into the bronchial tree,
blood, and urine; labeling these proteins has found its
application in the diagnosis of some conditions:
increase in both pulmonary fluid and blood serum of
patients with sarcoidosis or pulmonary fibrosis and in
patients undergoing mechanical ventilation.
the serum concentration of protein CC16 would rapidly
rise immediately after the injury.
Labeling this protein in blood and urine as a good marker
for fibrotic changes in pneumoconiosis patients.
the serum concentration of the CC16 protein can be used
to predict a mortality risk in lung cancer.

13. References:
https://en.wikipedia.org/wiki/Club_cell
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4860431/
Encyclopedic medical dictionary
http://erj.ersjournals.com/content/45/6/1544