tenocyte
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Vertebrates

Tendon cells, or tenocytes, are elongated
fibroblast A fibroblast is a type of cell (biology), biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (Stroma (tissue), stroma) for animal Tissue (biology), tissues, and plays a critical role in wound ...

fibroblast
type cells. The cytoplasm is stretched between the
collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...

collagen
fibres of the tendon. They have a central
cell nucleus The cell nucleus (pl. nuclei; from Latin or , meaning ''kernel'' or ''seed'') is a membrane-bound organelle found in eukaryote, eukaryotic cell (biology), cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as ma ...

cell nucleus
with a prominent
nucleolus The nucleolus (, plural: nucleoli ) is the largest structure in the Cell nucleus, nucleus of eukaryote, eukaryotic cell (biology), cells. It is best known as the site of Ribosome biogenesis#Eukaryotes, ribosome biogenesis, which is the synthes ...

nucleolus
. Tendon cells have a well-developed
rough endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ...
and they are responsible for synthesis and turnover of tendon fibres and
ground substance Ground substance is an amorphous gel-like substance in the extracellular space that contains all components of the extracellular matrix (ECM) except for fibrous materials such as collagen and elastin. Ground substance is active in the development, m ...
.


Invertebrates

Tendon cells form a connecting
epithelial Epithelium or epithelial tissue is one of the four basic types of animal Tissue (biology), tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed Cell (biology), ...
layer between the
muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

muscle
and shell in
molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are recognized. The number of fossil sp ...

molluscs
. In
gastropods The gastropods (), commonly known as snails and slugs, belong to a large Taxonomy (biology), taxonomic class (taxonomy), class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater ...

gastropods
, for example, the retractor muscles connect to the shell via tendon cells. Muscle cells are attached to the collagenous myo-tendon space via
hemidesmosomes Hemidesmosomes are very small stud-like structures found in keratinocyte Keratinocytes are the primary type of Cell (biology), cell found in the epidermis (skin), epidermis, the outermost layer of the skin. In humans, they constitute 90% of ep ...
. The myo-tendon space is then attached to the base of the tendon cells via basal hemidesmosomes, while apical hemidesmosomes, which sit atop
microvilli Microvilli (singular: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption (chemistry), a ...

microvilli
, attach the tendon cells to a thin layer of
collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...

collagen
. This is in turn attached to the shell via organic fibres which insert into the shell. Molluscan tendon cells appear columnar and contain a large basal
cell nucleus The cell nucleus (pl. nuclei; from Latin or , meaning ''kernel'' or ''seed'') is a membrane-bound organelle found in eukaryote, eukaryotic cell (biology), cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as ma ...

cell nucleus
. The
cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryote, eukaryotic Cell (biology), cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear envelope, nuc ...
is filled with granular
endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ...
and sparse
golgi
golgi
. Dense bundles of
microfilaments Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cell (biology), cells that form part of the cytoskeleton. They are primarily composed of biopolymer, polymers of actin, but are modified by and inte ...

microfilaments
run the length of the cell connecting the basal to the apical hemidesmosomes.


See also

*
List of human cell types derived from the germ layers This is a list of Cell (biology), cells in humans derived from the three embryonic germ layers – ectoderm, mesoderm, and endoderm. Cells derived from ectoderm Surface ectoderm Skin * Trichocyte (human), Trichocyte * Keratinocyte Anterior pi ...


References

* * Human cells Connective tissue cells GAG secreting cells {{Cell-biology-stub