1st Year MBBS Histology MCQs and SEQs
Q.1: a). Enlist cell surface modifications. How do cilia differ from stereocilia? 1+3
b). what is immotile cilia syndrome (Kartagener syndrome). 1
ans: a). microvilli, kinocilia, stereocilia, flagella
Difference of cilia and stereocilia:
- motility: Cilia can be motile , whereas stereocilia are characterized by their lack of motility.
- association: Stereocilia are actually more associated with microvilli, than cilia.
- function: Cilia’s function are to move cells, or propel objects, while stereocilia are mechanosensing organelles.
- location: In the human body cilia are particularly found in the respiratory passages , while stereocilia are found on the cochlea in the inner ear, ductus deferens, and epididymis.
b). Immotile cilia syndrome (kartagener syndrome): Cilia and flagella are immotile due to absence of dynein arms of the microtutbules. Associated with recurrent respiratory tract infections and infertility.
Q.2: a). Define epithelium and classify it with the help of a flow sheet diagram. Also give examples. 1+2+2
Ans: DEFINITION: It is one of the basic tissues which is made up of closely packed cells and is arranged in one or more layers with almost no intercellular spaces and only a small amount of intercellular substance.
Classification of epithelium:
two main types are glandular and covering epithelium.
Covering epithelium is of two types: simple and stratified
Simple epithelium: (any one example is enough)
- Simple Squamous (pavement) epithelium (e.g. They form the lining of cavities such as the mouth, blood vessels, heart and lungs and make up the outer layers of the skin).
- Simple Cuboidal Epithelium (e.g. Cuboidal epithelium is found in glands and in the lining of the kidney tubules, Also found in the small ducts of exocrine glands, Surface epithelium of ovary).
- Simple Columnar Epithelium (e.g. Columnar epithelium forms the lining of the stomach and intestines and gallbladder ).
- Pseudostratified epithelium (e.g.respiratory epithelium in the nose and trachea )
Stratified epithelium: (any one example is enough)
- Stratified Squamous (pavement) epithelium (e.g. epidermis of skin, epithelium of espophagus and vagina )
- Stratified Cuboidal Epithelium (e.g. large ducts of glands)
- Stratified Columnar Epithelium (e.g. found in lining of prostatic, membranous and penile urethra).
- Transitional epithelium (e.g. epithelium of urinary bladder and ureter )
Q.3: a). enlist cell junctions and briefly explain nexus 1+2.
b).explain the structure of microtubules? 2
ans: Types of intercellular junctions :
- Tight junctions/zonula occludens
- zonula adherens
- Desmosomes/macula adherens
- Gap junctions/nexus
Nexus: Adjacent plasma membrane are closely opposed. intercellular space narrows upto 2-3 nm.
- Gap junctions are made up of large protein units called CONNEXONS
- Each connexon has 6 subunits called CONNEXIN surrounding a channel
- The diameter of the channel is 2 nm and allows sugars, Amino Acids and small ions, cAMP to pass through.
- Rapid propagation of electrical activity
- Metabolic coupling
- Exchange of various chemical messangers between the cells
- Not associated with any cytoskeletal filament
- Loaction: Numerous in liver and pancreatic cells, heart and smooth muscles.
Structure of microtubules: These are slender, long, hollow and unbranched tubes. Their diameter is 25 nm and length is from 200 nm to 25 um. Tubulin heterodimer molecules (made by alpha and beta tubulin) polymerize to make the protofilaments. 13 protofilaments arranged helically make the microtubules.
Q.4: Define and briefly explain the pseudostratified epithelium. Also draw its diagram. 1+2+2
Ans: definition: single layer of cells with nuclei arranged at different levels; not all cells reach surface but all adhere to basal lamina.
Cell types: basal cells, tall columnar cells, goblet cells
Location: Lining of trachea, bronchi, nasal cavity.
Function: Protection, secretion; cilia-mediated transport of particles trapped in mucus out of the air passages.
Q.5: Draw and label transitional epithelium.5
Q.6: a).Classify glands on the basis of mode of secretion. 4
b). what are the goblet cells? 1
ans: a) Merocrine secretion (eccrine secretion): most common type of glandular epithelium secretion where secretion occurs by exocytosis. The secretory granules leave the cell with no loss of other cellular material. Mucous and serous cells exhibit this type of secretion.
- b) Apocrine secretion: A rare type of secretion dependent on sex hormones. a portion of the cytoplasm of the cell simply pinches off enclosing the granules. Within the lumen, this small secretory vesicle breaks down and releases the gland’s products. Apocrine glands become functional at puberty. They respond to emotional or sensory stimuli. Examples of apocrine glands include lactating mammary glands, apocrine glands of skin in the pubic and axilla regions.
- Holocrine secretion :This secretion consists of disintegrated cells of the gland itself. Granules fill the cell until the entire cell becomes “bloated” with secretory products. Instead of being released (merocrine) or pinched off (apocrine), the whole cell is discharged into the lumen. Once inside the lumen, the cell degenerates and the secretory products are released.
- Cytogenic glands: produce living cells e.g. testis and ovary
Goblet cells: these are Unicellular glands and secrete Mucus. These are the only example of these single-celled glands in humans. These goblet cells secrete mucus and are easily visualized in slides of the small intestine.
In routine (H&E) preparations, the cytoplasmic mucin is not preserved (and therefore, not stained) giving the cells an empty appearance.
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