8 topics with a brief review: definitions, key facts, and classroom questions.
This section lays the foundation for understanding histology. We start with the basic doctrine of tissues and analyze levels of cell potency — the basis of cambiality and the ability of tissues to undergo physiological and reparative regeneration.
The main focus is on epithelial tissues — the boundary and secretory structures of the body. The section covers the morphological classification in detail: simple and stratified epithelia. Special attention is paid to tissues with specific biomechanics and protection — the transitional epithelium of the urinary tract and the stratified squamous keratinized epithelium of the skin epidermis. Glandular epithelium and secretion mechanisms are discussed separately, in particular holocrine secretion, in which the cell is completely destroyed, turning into secretion.
Practical classes and exams most commonly require the ability to diagnose the type of epithelium on a histological slide, name the layers of stratified epithelia, and clearly understand the difference between the types of secretion in exocrine glands.
What is the difference between commitment and determination?
Commitment is the entire process of the gradual narrowing of a cell's potential. Determination is the final stage of commitment, when the cell has only one genetically programmed pathway of development.
Why is vascular endothelium classified as epithelium, given that it develops from mesenchyme?
From the standpoint of histogenesis, it is close to connective tissue, but from a morphofunctional approach, the endothelium forms a continuous sheet and acts as a barrier, which is the main criterion for epithelial tissue.
How to determine from a mesothelium preparation (top view) that it is a squamous epithelium?
On a whole-mount film preparation, it is impossible to evaluate cell height. We know that mesothelium is squamous from cross-section data, which show that the height of the cells is significantly less than their width.
Where are stem cells localized in stratified epithelia?
Stem (cambial) cells are located exclusively in the lowest — basal layer, which contacts the basement membrane.
Why is this epithelium called transitional?
The name reflects its ability to visually "transition" from one state to another: the thickness of the layer and cell shape change from tall dome-like (in an empty organ) to flat (in a stretched one).
What is the main difference between thick and thin skin?
In thick skin (palms, soles), the epidermis consists of 5 layers — the stratum lucidum is present. In thin skin, the stratum lucidum is absent, and all other layers are significantly thinner.
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