Development of the nervous system ( 8-1 and 8-2 ) The central nervous system (CNS) develops from the primitive ectoderm (see 8-1 ; see Box 8-A and Box 8-B ). A simple epithelial disk, the neural plate , rapidly rolls…
SKELETAL MUSCLE ( 7-1 ) Muscle cells or fibers form a long multinucleated syncytium grouped in bundles surrounded by connective tissue sheaths and extending from the site of origin to their insertion. The epimysium is a dense connective tissue layer…
BLOOD Blood consists of cells and plasma . These components may be separated by centrifugation when blood is collected in the presence of anticoagulants. The sedimented red blood cells (RBCs) constitute about 42%–47% of blood volume. This percentage of erythrocyte…
OSTEOGENESIS (Bone development or ossification) Bone can develop either directly from an initial cell condensation of the mesenchyme (intramembranous ossification) or by gradual replacement of a pre-existing tissue, the cartilage, which acts as a template (endochondral ossification; bone formation inside…
Classification ( 4-1 to 4-3 ) Unlike epithelial cells, which are almost free of intercellular material, connective tissue cells are widely separated by components of the extracellular matrix (ECM). In addition, epithelial cells lack direct blood and lymphatic supply, whereas…
CELL SIGNALING MECHANISMS An understanding of the molecular aspects of cell signaling is clinically relevant to uncover potential targets of novel therapeutics for the treatment of metabolic dysfunctions and diseases. Signaling molecules can transmit information by acting as ligands ,…
EPITHELIAL GLANDS Types of epithelial glands ( 2-1 ) Most glands develop as an epithelial downgrowth extending into the underlying connective tissue. Exocrine glands remain connected to the surface of the epithelium by an excretory duct that transports the secretory…
CLASSIFICATION OF EPITHELIA ( 1-1 to 1-4 ) The epithelium is a tightly cohesive sheet of cells that covers or lines body surfaces and forms the functional units of secretory glands . The main characteristics of epithelia are summarized in…