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Mitochondria (Inferior)
Secondary Oocyte

Mitochondria (Inferior)


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Quick Facts

Mitochondria are the small spherical to rod-shaped cytoplasmic organelles, consisting of inner and outer bilayer membranes with a space between them. The inner membrane is infolded to form a series of projections (cristae), and the space between the cristae is filled by the mitochondrial matrix, which contains DNA, RNA, ribosomes, and granules. Mitochondria generate energy (in the form of ATP synthesis) by the oxidation of nutrients, and they contain the enzymes of the tricarboxylic acid (Krebs) cycle and for fatty acid oxidation and oxidative phosphorylation. In response to toxic insults, they release enzymes that cause apoptosis. Mitochondria can replicate independently and code for the synthesis of some of their proteins; inheritance of mitochondrial DNA is maternal, and mitochondrial DNA defects cause a variety of diseases (Dorland, 2011).

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Related parts of the anatomy


Mitochondria are small, membrane-bound, ovoid organelles approximately 0.5-2 μm long. Each mitochondrion is lined by an inner and outer membrane. The inner membrane is deeply folded to form deep invaginations, called cristae. The lumen of the mitochondria is surrounded by the inner membrane and contains the mitochondrial matrix (Gouspillou and Hepple, 2017).

Mitochondria contain their own unique DNA, referred to as mitochondrial DNA (or mtDNA), and is different from the nuclear DNA. During fertilization, mitochondria from sperm do not enter the oocyte, therefore, mitochondria in the developing zygote are inherited from the oocyte.

Key Features/Anatomical Relations

There are numerous mitochondria present in the cytoplasm of the oocyte.


Mitochondria are the powerhouse and energy production station of the oocyte. They also play a role in apoptosis, as it stores proapoptotic factors, and calcium homeostasis (Dumollard, Duchen and Carroll, 2007).

The mitochondria play a role in the development process of the oocyte, the fusion of the oocyte and the sperm, as well as the growth of the embryo. They modulate growth and development by regulating calcium signaling, producing ATP, reactive oxygen species, and intermediary metabolites (Dumollard, Duchen and Carroll, 2007).

List of Clinical Correlates

- Infertility

- Assisted reproductive technology

- Heteroplasmy


Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.

Dumollard, R., Duchen, M. and Carroll, J. (2007) 'The Role of Mitochondrial Function in the Oocyte and Embryo', Current Topics in Developmental Biology: Academic Press, pp. 21-49.

Gouspillou, G. and Hepple, R. T. (2017) Mitochondria in Skeletal Muscle Health, Aging and Diseases. Frontiers Research Topics.

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