On the welcome page of the dictionary, three major sections are shown: Normal tissues, Cancer and Cell structure. Below the image of each section are links to introductory texts for i) normal tissue histology, ii) hallmarks of cancer, and iii) cell structure overview. For the cancer-section there is also a link to current cancer statistics (incidence, survival, etc) for Sweden and the rest of the world. Within each section there are direct links to histology descriptions of different tissue types and tumor forms as well as descriptions of cell structures.
For the 'Tissue & cell types' and 'Tumor' sections, tissue-slides stained with hematoxylin and eosin (HE) are shown at three different levels of magnification. On the top level, an overview of the whole tissue-sample is shown with boxes in black indicating where zoomed-in representative parts of the tissue are available for viewing. Clicking on these boxes will zoom in on that part to show tissue structures, cells and features in greater detail. Throughout these sections, arrows indicate relevant tissue structures, cell-types and other features.
For the 'Cell structure' section, immunofluorescent images of formaldehyde-fixed cell lines are shown. The various cell structures that are demonstrated are always shown in the green channel using an antibody found in the Human Protein Atlas. The antibody name is linked to the subcellular location summary page of the target gene. The other channels: nucleus, microtubules and endoplasmic reticulum, are always shown in the blue, red and yellow channels, respectively. The channels can be toggled on and off by clicking on the respective coloured button above the image. When applicable, the immunofluorescent images are complemented by immunohistochemically stained cells where the location of the particular cell structure is shown in brown.
A common feature for all sections is that a general descriptive text about the tissue, tumor-type or cell structure is provided when browsing a particular topic.
The rectum is approximately 20 cm long. It is continuous with the sigmoid colon and anal canal and functions as a reservoir for feces before excretion. Histologically it resembles the colon with straight tubular glands that extend through the thickness of the mucosa. The glands are almost entirely lined by mucous secreting gobletcells but some scarce enterocytes are also seen.
There is more diffuse lymphoid tissue in the rectum than in the remainder of the large intestine and both plasmacells and occasional eosinophilicgranulocytes are often present.
General histology of gastro-intestinal tract (GI-tract)
The gastrointestinal canal consists of the esophagus, stomach, duodenum, jejunum, ileum, colon, rectum and anal canal. It is best viewed as a long tube passing from the oral to the anal opening. It supplies the body with water, electrolytes and nutrients from the food we eat. Our main sources of food are carbohydrates, proteins and fats, which in general cannot be absorbed in the form they are ingested. First they have to be broken down into small enough compounds. The process of digestion and absorption is carried out in a stepwise fashion as the food passes down the different parts of the gastrointestinal tract.
The general structure of all parts of the GI-tract is
1) tunica serosa /adventitia ? Loose connective tissue with elastic and collagen fibers, nerves and vessels, covered by a single layer of flat mesothelial cells. Where there is no mesothelial cover the outermost layer is called adventitia.
2) tela subserosa ? thin layer of loose connective tissue separating the serosa and muscle layer.
3) tunica muscularis ? which for most parts is composed of an inner circular and outer longitudinal smooth muscle layer. Between the muscle fibers the myenteric plexus of Auerbach can be identified.
4) tela submucosa ? a thick layer of loose connective tissue with numerous of blood and lymphatic vessels. Here is where the ganglion cells of the submucosal plexus of Meissner might be seen.
5) tunica mucosa ? the innermost layer that comes in contact with the gastrointestinal content. It has secretory and absorptive function. The mucosa consists of the innermost epithelium that forms surface cells and glands, embedded in the lamina propria containing mainly of loose connective tissue with small blood vessels and immune cells. A thin layer of smooth muscle, lamina muscularis mucosae, demarcates the division of the mucosa and submucosa.
