CorpusHuman Anatomy
Cells & TissuesOrganelle

Centrosome and centrioles

Centrosoma; centriolum

Also known as: centriole, centrioles, microtubule-organising centre, MTOC, basal body, pericentriolar material

The main microtubule-organising centre of animal cells: a pair of perpendicular centrioles (each nine microtubule triplets) embedded in pericentriolar material that nucleates microtubules and organises the mitotic spindle.

Mitosis and Cytokinesis The Eukaryotic Cell

Overview

Centriole structure9 triplets, no central pair (9×3 + 0)
Centriole size≈0.2 × 0.4–0.5 µm
DuplicationOnce per cycle, from G1/S through S phase

The centrosome lies near the nucleus, usually surrounded by the Golgi apparatus. It contains two centrioles oriented at right angles to each other. Each centriole is a short cylinder (≈0.2 µm wide, ≈0.4–0.5 µm long) whose wall consists of nine triplets of microtubules arranged like a pinwheel (9 × 3 + 0 — no central microtubules). The centrioles are embedded in an amorphous pericentriolar material (PCM) rich in γ-tubulin ring complexes, which nucleate microtubules with their minus ends anchored at the centrosome and plus ends radiating outwards (the interphase "aster").

The centrosome duplicates once per cell cycle, beginning at the G1/S transition (regulated by PLK4 and CDK2): each centriole templates a new daughter at right angles during S phase, and the two centrosomes separate in late G2/prophase to become the spindle poles of mitosis, ensuring each daughter cell inherits one.

A centriole can migrate to the cell surface and become a basal body, which templates the axoneme of a cilium or flagellum. Ciliated epithelial cells generate hundreds of basal bodies. Neurons and many differentiated cells have no active centrosome-based spindle function but retain centrioles that form primary cilia.

Parts & subdivisions

  1. Mother and daughter centrioles
    9 triplet-microtubule cylinders at right angles; the mother bears distal and subdistal appendages.
  2. Pericentriolar material
    γ-Tubulin ring complexes and scaffold proteins (pericentrin) that nucleate microtubules.
  3. Basal body
    Modified centriole at the base of a cilium or flagellum.

Function

  • Nucleates and organises cytoplasmic microtubules.
  • Forms the poles of the mitotic spindle.
  • Gives rise to basal bodies of cilia and flagella.
  • Helps establish cell polarity and positions the Golgi apparatus.

Clinical significance

Primary microcephaly

Autosomal recessive mutations in centrosomal genes (e.g. ASPM, CDK5RAP2, CENPJ) impair spindle orientation and division of neural progenitors, producing a small brain.

Centrosome amplification in cancer

Extra centrosomes cause multipolar spindles and chromosome mis-segregation, contributing to aneuploidy and genomic instability in tumours.

Compiled from standard anatomy and physiology references — see the Cells & Tissues sources. For education only; not medical advice.