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Sectional organization of spinal cord. The spinal cord is the main pathway for information connecting the brain and peripheral nervous system. [3] [4] Much shorter than its protecting spinal column, the human spinal cord originates in the brainstem, passes through the foramen magnum, and continues through to the conus medullaris near the second lumbar vertebra before terminating in a fibrous ...
Various types of specialized tissues and cells are classified under the spectrum of connective tissue, and are as diverse as brown and white adipose tissue, blood, cartilage and bone. [23]: 158 Cells of the immune system—such as macrophages, mast cells, plasma cells, and eosinophils—are found scattered in loose connective tissue, providing ...
The matrix is hardened by the binding of inorganic mineral salt, calcium phosphate, in a chemical arrangement known as bone mineral, a form of calcium apatite. [8] [9] It is the mineralization that gives bones rigidity. Bone is actively constructed and remodeled throughout life by specialized bone cells known as osteoblasts and osteoclasts.
Skeletal muscle cells are the individual contractile cells within a muscle, and are often termed as muscle fibers. [3] A single muscle such as the biceps in a young adult male contains around 253,000 muscle fibers. [22] Skeletal muscle fibers are multinucleated with the nuclei often referred to as myonuclei.
The Haversian canals surround blood vessels and nerve cells throughout bones and communicate with osteocytes (contained in spaces within the dense bone matrix called lacunae) through connections called canaliculi. This unique arrangement is conducive to mineral salt deposits and storage which gives bone tissue its strength.
The origin of true muscle cells is argued by other authors to be the endoderm portion of the mesoderm and the endoderm. However, Schmid & Seipel (2005) [30] counter skepticism – about whether the muscle cells found in ctenophores and cnidarians are "true" muscle cells – by considering that cnidarians develop through a medusa stage and polyp ...
Nerves that exit from the brain are called cranial nerves while those exiting from the spinal cord are called spinal nerves. The nervous system consists of nervous tissue which, at a cellular level, is defined by the presence of a special type of cell, called the neuron. Neurons have special structures that allow them to send signals rapidly ...
Cells comprising the central nervous system and peripheral nervous system are classified as nervous (or neural) tissue. In the central nervous system, neural tissues form the brain and spinal cord. In the peripheral nervous system, neural tissues form the cranial nerves and spinal nerves, inclusive of the motor neurons.