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Each lacuna is occupied during life by a branched cell, termed an osteocyte, bone-cell or bone-corpuscle. Lacunae are connected to one another by small canals called canaliculi. A lacuna never contains more than one osteocyte. Sinuses are an example of lacuna.
Lacuna (histology), a small space containing an osteocyte in bone, or chondrocyte in cartilage Muscular lacuna , a lateral compartment of the thigh Vascular lacuna , a medial compartment beneath the inguinal ligament
Human embryology is the study of this development during the first eight weeks after fertilization. The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus.
Two proteins, bone morphogenetic protein 4(BMP-4) and fibroblast growth factor 2(FGF2) have been seen to influence the amount of differentiation into chondrocytes. [4] Both proteins are known to play a role in embryonic stem cell differentiation into mesodermal cells, through signaling with BMP-4 and as FGF2 acting as a stimulator.
The embryo of a given species never resembles the adult form of a lower one. The embryo of a given species does resemble the embryonic form of a lower one. [1] Using Darwin's theory evolutionary embryologists have since been able to distinguish between homologous and analogous structures between varying species.
Trophoblasts are specialized cells of the placenta that play an important role in embryo implantation and interaction with the decidualized maternal uterus. [5] The core of placental villi contain mesenchymal cells and placental blood vessels that are directly connected to the fetus’ circulation via the umbilical cord .
The initiation of endochondral ossification starts by proliferation and condensation of mesenchymal cells in the area where the bone will eventually be formed. Subsequently, these mesenchymal progenitor cells differentiate into chondroblasts, which actively synthesize cartilage matrix components.
Bone canaliculi are microscopic canals between the lacunae of ossified bone. The radiating processes of the osteocytes (called filopodia) project into these canals. These cytoplasmic processes are joined together by gap junctions. Osteocytes do not entirely fill up the canaliculi.