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.
Hematopoiesis is the formation of blood cells (erythrocytes, monocytes, granulocytes, platelets and lymphocytes). In the post-fetal life this takes place exclusively in the bone marrow, with exception for lymphocytes that are also formed in lymphoid tissues. In early life virtually all bones have an active bone marrow containing hematopoietic cells that participate in the formation of blood. Bone marrow display adipocytes with variable number of dispersed foci of hematopoietic cells. With increasing age, bone marrow at several sites is replaced by adipose tissue, either entirely, or only partially. The primary sites of blood formation are the vertebrae, sternum, ribs and pelvic bones. Bone marrow consisting entirely of fat is called yellow marrow, bone marrow with active hematopoiesis is referred to as red marrow.
Pluripotent hematopoietic stem cells give rise to all blood lineages, through cell division and subsequent differentiation starting from multipotent lymphoid stem cells (progenitors to lymphocytes) and multipotent myeloid stem cells (progenitors to red blood cells, neutrophils, monocytes and megakaryocytes). The stem cells are not possible to identify in H & E stained sections from the bone marrow, but various hematopoietic cells at different developmental levels can be identified by their different morphological signatures. The cell that is easiest to detect is the very large megakaryocyte that produces platelets.
