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The endodermis is the boundary between the cortex and the stele. In many seedless plants, such as ferns, the endodermis is a distinct layer of cells immediately outside the vascular cylinder (stele) in roots and shoots. In most seed plants, especially woody types, the endodermis is present in roots but not in stems.
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.
The discovery of the Casparian strip dates back to the mid-19th century, and advances in the understanding of the endodermis of plant roots. [15] In 1865, the German botanist Robert Caspary first described the endodermis of the root of plants, found that its cell wall was thickened, and named it Schuchtzscheide.
The mycorrhizae of the fungus then uses its extended system to help the plant find the correct area of nutrition, signaling the direction in which the roots should grow. [13] This makes root growth more efficient, preserving energy for other metabolic processes, which in turn benefits the fungus that feeds off those metabolic products.
The Haversian canal contains the bone's blood supplies. The boundary of an osteon is the cement line. Each Haversian canal is surrounded by varying number (5-20) of concentrically arranged lamellae of bone matrix. Near the surface of the compact bone, the lamellae are arranged parallel to the surface; these are called circumferential lamellae.
A germ layer is a primary layer of cells that forms during embryonic development. [1] The three germ layers in vertebrates are particularly pronounced; however, all eumetazoans (animals that are sister taxa to the sponges) produce two or three primary germ layers.
In a long bone it is a thin disc of hyaline cartilage that is positioned transversely between the epiphysis and metaphysis. In the long bones of humans, the epiphyseal plate disappears by twenty years of age. physis, "the growth part" metaphysis: The region of a long bone lying between the epiphysis and diaphysis.
The outer surface of a bone is lined by a thin layer of connective tissue that is very similar in morphology and function to endosteum. It is called the periosteum , or the periosteal surface. During bone growth , the width of the bone increases as osteoblasts lay new bone tissue at the periosteum.