Covers the cell centre, or centrosome, as the main microtubule-organising centre of most somatic cells, and the paired centrioles it contains. Describes centriole structure, including the nine microtubular triplets, approximate dimensions and their perpendicular arrangement. Then explains centrosome functions in shaping the cell, positioning the nucleus, duplicating before division, forming the mitotic spindle, and aiding chromosome separation and cytokinesis, ending with the centriole's role in cilia and flagella.
Topic 30 of 97 in the MU Sofia syllabus for Cytology (Medicine, Year 1). The free AceMed note covers it in 6 sections, about 368 words (3 min of reading), with 15 flashcards.
In this note
Cell Centre and Centrioles:
Cell Centre (Centrosome)
Centrioles: Structure
Centrioles and Centrosome: Functions
Duplication and Mitotic Role
Role in Cilia and Flagella
Cell Centre (Centrosome)
Definition and Location: The cell centre, also known as the centrosome, is the dominant microtubule-organising centre (MTOC) in most somatic cells. It is an amorphous region adjacent to the nucleus in non-dividing cells.
Composition: It consists of paired centrioles surrounded by a pericentriolar matrix, which is a dense matrix of free tubulin subunits and other proteins.
Centrioles: Structure
Composition: Centrioles are cylindrical structures made up of tubulin. Each centriole is composed of nine highly organised microtubular triplets.
Dimensions: Each centriole is approximately 0.2 μm in diameter and 0.3-0.5 μm in length.
Arrangement: The two centrioles within a centrosome are typically positioned with their long axes at right angles to each other.
Centrioles and Centrosome: Functions
Microtubule Organisation: The centrosome, with its centrioles, plays a key role in organising microtubules. Microtubules are essential for maintaining cell shape and serve as tracks for the transport of vesicles and organelles.
Cell Shape and Polarity: By organising microtubules, the centrosome helps maintain the cell's shape and polarity.
Nuclear Positioning: The position of the centriole determines the position of the nucleus within the cell.
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