Organelles

Organelles are specialized portion of the cell with a
characteristic shape that assume specific role in growth,
maintenance, repair and control.

a) Nucleus, Oval in shape and is the largest structure in the
cell. Contain the hereditary factor in the cell. Hence it
controls cell activity & structure. Most cell contain single
nucleus but some like matured Red Blood cell do not
contain. However Muscle cell contain several nucleuses.
The nucleus separated from other cell structure by double
membrane called nuclear membrane. Pores over the
nuclear membrane allow the nucleus to communicate with
the cytoplasm. In the nucleus a jelly like fluid that fill the
nucleus is karylymph (neucleoplasm), which contain the
genetic material called chromosome. Nucleus also
contain dark, somewhat spherical, non-membrane bound
mass called nucleolus. It contains DNA, RNA and protein,
which assist in the construction of ribosome.
b) Ribosome, tiny granules, composed of Ribosomal RNA
(rRNA). They are site of protein synthesis Human Anatomy and Physiology
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c) Endoplasmic reticulum is a double membrane channel. It
is continuous with the nuclear membrane. It involved in
intracellular exchange of material with the cytoplasm.
Various products are transported from one portion of the
cell to another via the endoplasmic reticulum. So it is
considered as intracellular transportation. It is also
storage for synthesized molecules. Together with the
Golgi complex it serves as synthesis & packaging center.

Endoplasmic reticulum (ER) is divided in to two. These
are, granular E.R. Containing granule and involving in
synthesis of protein and agranular E.R. that synthesize
lipid & involves in detoxification.
d) Golgi Complex, near to the nucleus. It consist 4-8
membranous sacs. It process, sort, pack & deliver protein
to various parts of the cell.
e) Mitochondria, a small, spherical, rod shaped or
filamentous structure. It generates energy. Each
mitochondria posses two membrane, one is smooth
(upper) membrane and the other is arranged with series
of folds called cristae. The central cavity of a
mitochondrion enclosed by the inner membrane is the
matrix.
f) Lysosomes appear as membrane enclosed spheres. They
are formed from Golgi complexes & have single
membrane. They contain powerful digestive (hydrolytic Human Anatomy and Physiology
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enzyme capable of breaking down many kinds of
molecules. The lysosomal enzyme believed to be
synthesized in the granular endoplasmic reticulum and
Golgi complex.
g) The cyto-skeleton, the cytoplasm has a complex internal
structure consisting of a series of exceedingly small
microfilaments, microtubule & intermediate filaments
together referred to as the cyto-skeleton.
h) Centrosme, a dense area of cytoplasm generally
spherical and located near the nucleus it contain
centrioles. It also contains DNA that controls their
replication. Centrosmes are made of microtubules, which
seam drinking straws. They are Involved in the movement
of chromosome during cell division.
i) Cilia/flagella, thread like appendages, which are made of
microtubules. When they are beating forms rhythmic
movement. They are found in female reproductive organ
and upper respiratory tube.