Khusboo Ramchandani 12301016027
Histology Homework #1 & 2
1. How is the H & E staining technology applied in histology?
Hematoxylin and Eosin have long been used in staining tissues and cell sections in histology because most cells are transparent and observing structures and features under bright light microscopy can prove to be difficult. Nuclei are usually stained bluish-purple while cytoplasm and other structures stain in various shades of pink. This is because Eosin is an acidic dye and stains basic structures whereas hematoxylin is a basic due that stains acidic structures.
2. What are the features of electron microscopy? How to apply it?
Electron microscopy is mainly used to observe details of cells, tissues and organs, i.e. organelles. It uses a beam of electrons to create an image of the specimen in high magnification and great clarity as compared to the light microscope.
1. What are the common features of the epithelial tissue?
Epithelial tissues cover surfaces of the body and serve to protect by acting as a boundary or barrier because the tissue is formed by an uninterrupted layer of cells. There is no extra-cellular matrix and the tissue is not vascularized. However it is polarized and has apical surfaces where three main functions occur – secretion, absorption and excretion. The tissue also rests on a basement membrane which separates it from underlying tissue.
2. How to classify the various types of epithelia?
Epithelia can be classified according to the number of layers of cells and shape of the cells. Common terminology in classification include simple (single layer), stratified (two or more layers), squamous (flattened cells), cuboidal (box-shaped cells) and columnar (tall pillar-like cells).
3. Why is it called endoothelia / mesothelia?
Endothelia – These tissues line the “inside” or interior surfaces of blood vessels and lymphatic system.
Mesothelia – These tissues are found to protect cavities in the ‘middle’ of the body including thoracic cavity, abdominal cavity and the heart sac.
4. How many specializations have you learnt? What are the features in structure and function?
Microvillus is a striated, brush border. It has fingerlike cytoplasmic projection which increase the surface area of absorption. Also, It has microfilamentous core attached to the terminal web for ‘movement’ of microvilli to increase efficiency.
Under a light microscope, it is seen as a cone-shaped structure. It is not a true cilia and is non-motile.
The cilia is a long, highly motile cytoplasmic projection. It has an elongated axoneme core which ahs one central pair of microtubules and 9 pairs of peripheral microtubules. The cilia is mainly involved in rapid back-and forth movement.
1. Basal laminae
Basal laminae is made up of glycoproteins and proteoglycans. It has 2 parts – lamina densa (dense layer, dark colour) and lamina lucida (lucid, light colour). Main functions include structural support, filtering functions in the renal complexes, influencing cell polarity and metabolism, regulating cell proliferation, differentiation and migration, epithelial regeneration and cell-to-cell interaction.
2. Plasma membrane infolding
Plasma membrane infoldings are mainly infoldings of the basal membrane which contains many longitudinal mitochondria. This is because the membrane is involved in active transport of water and electrolytes.
Hemidesmosomes are technically half a desmosome. Desmosomes are a specialized junction and are single spots. They do not encircle the membrane. Main function is for firm adhesion.
1. Tight junction/occluding junction
It complete encircles a cell by fusion of membranes. It seals to protect the flow of materials between cells.
2. Adhesive junction/anchoring junction
It is band-like and encircles the cell. Mainly involved in the adhesion of one cell to another.
3. Gap junction
Circular patches formed by aggregated transmembrane protein complexes. It serves to communicate and exchange materials between cells.