![This is blank.](https://digitalhistology.org/wp-content/themes/histology-unified/imgs/trans.png)
Secretory units
These electron micrographs compare the structure of a mucous tubule (left) with that of a serous acinus (right). 5000x
![Mucous tubule > <p>The tubule cells contain numerous irregular mucous-containing secretory granules. This mucus is often lost during routine histological processing resulting in the foamy appearance of the cytoplasm. Nuclei are located at the base of the cells and the tubule shows a wide lumen.</p>](https://digitalhistology.org/wp-content/uploads/2017/10/Or.Dig_.OC_.Sal-20-1-ping.png)
Mucous tubule >
The tubule cells contain numerous irregular mucous-containing secretory granules. This mucus is often lost during routine histological processing resulting in the foamy appearance of the cytoplasm. Nuclei are located at the base of the cells and the tubule shows a wide lumen.
![- Nuclei <p>The tubule cells contain numerous irregular mucous-containing secretory granules. This mucus is often lost during routine histological processing resulting in the foamy appearance of the cytoplasm. Nuclei are located at the base of the cells and the tubule shows a wide lumen.</p>](https://digitalhistology.org/wp-content/uploads/2017/10/Or.Dig_.OC_.Sal-20-2-ping.png)
- Nuclei
The tubule cells contain numerous irregular mucous-containing secretory granules. This mucus is often lost during routine histological processing resulting in the foamy appearance of the cytoplasm. Nuclei are located at the base of the cells and the tubule shows a wide lumen.
![- Mucous granules <p>The tubule cells contain numerous irregular mucous-containing secretory granules. This mucus is often lost during routine histological processing resulting in the foamy appearance of the cytoplasm. Nuclei are located at the base of the cells and the tubule shows a wide lumen.</p>](https://digitalhistology.org/wp-content/uploads/2017/10/Or.Dig_.OC_.Sal-20-3-ping.png)
- Mucous granules
The tubule cells contain numerous irregular mucous-containing secretory granules. This mucus is often lost during routine histological processing resulting in the foamy appearance of the cytoplasm. Nuclei are located at the base of the cells and the tubule shows a wide lumen.
![- Wide lumen with mucus <p>The tubule cells contain numerous irregular mucous-containing secretory granules. This mucus is often lost during routine histological processing resulting in the foamy appearance of the cytoplasm. Nuclei are located at the base of the cells and the tubule shows a wide lumen.</p>](https://digitalhistology.org/wp-content/uploads/2017/10/Or.Dig_.OC_.Sal-20-4-ping.png)
- Wide lumen with mucus
The tubule cells contain numerous irregular mucous-containing secretory granules. This mucus is often lost during routine histological processing resulting in the foamy appearance of the cytoplasm. Nuclei are located at the base of the cells and the tubule shows a wide lumen.
![Serous acinus > <p>The acinus consists of pyramidal-shaped cells, whose apical cytoplasm is filled with darkly-stained, uniformly-sized, secretory granules. The small central lumen contains the serous secretory product contained in the granules.</p>](https://digitalhistology.org/wp-content/uploads/2017/10/Or.Dig_.OC_.Sal-20-5-ping.png)
Serous acinus >
The acinus consists of pyramidal-shaped cells, whose apical cytoplasm is filled with darkly-stained, uniformly-sized, secretory granules. The small central lumen contains the serous secretory product contained in the granules.
![- Nucleus <p>The acinus consists of pyramidal-shaped cells, whose apical cytoplasm is filled with darkly-stained, uniformly-sized, secretory granules. The small central lumen contains the serous secretory product contained in the granules.</p>](https://digitalhistology.org/wp-content/uploads/2017/10/Or.Dig_.OC_.Sal-20-6-ping.png)
- Nucleus
The acinus consists of pyramidal-shaped cells, whose apical cytoplasm is filled with darkly-stained, uniformly-sized, secretory granules. The small central lumen contains the serous secretory product contained in the granules.
![- Serous granules <p>The acinus consists of pyramidal-shaped cells, whose apical cytoplasm is filled with darkly-stained, uniformly-sized, secretory granules. The small central lumen contains the serous secretory product contained in the granules.</p>](https://digitalhistology.org/wp-content/uploads/2017/10/Or.Dig_.OC_.Sal-20-7-ping.png)
- Serous granules
The acinus consists of pyramidal-shaped cells, whose apical cytoplasm is filled with darkly-stained, uniformly-sized, secretory granules. The small central lumen contains the serous secretory product contained in the granules.
![- Small lumen with serous product <p>The acinus consists of pyramidal-shaped cells, whose apical cytoplasm is filled with darkly-stained, uniformly-sized, secretory granules. The small central lumen contains the serous secretory product contained in the granules.</p>](https://digitalhistology.org/wp-content/uploads/2017/10/Or.Dig_.OC_.Sal-20-8-ping.png)
- Small lumen with serous product
The acinus consists of pyramidal-shaped cells, whose apical cytoplasm is filled with darkly-stained, uniformly-sized, secretory granules. The small central lumen contains the serous secretory product contained in the granules.