RIZAL.PDF - Tissues in the Body PDF

In the body’s organizational hierarchy, tissues occupy a place between cells and organs. That is, a tissue is a group of cells with a similar shape and function. In turn, organs (which make up the body) are comprised of various tissues. Broadly there are four types of tissues namely, Epithelial...

In the body’s organizational hierarchy, tissues occupy a place between cells and organs. That is, a tissue is a group of cells with a similar shape and function. In turn, organs (which make up the body) are comprised of various tissues. Broadly there are four types of tissues namely, Epithelial tissue is the body’s protection against the outside environment. Connective tissue holds the body together. Muscle tissue is is contractile tissue and Nervous tissuecomprises the body’s wiring system as it conducts signals between the nervous system and various organs. Embryonic Origin They are embryonically derives from ectoderm, mesoderm and endoderm. It covers body and organ surfaces, lines body cavities and lumina (the hollow portions of body organs or vessels) and forms various glands. Characteristics of Epithelial tissue: Composed of continuous and tightly packed cells covering the surfaces of the body and stand on a basement membrane which provides a site of attachment for the epithelium, and acts as a selective ltration barrier. With very little intercellular material, they do not have their own blood supply (avascular), relying on diffusion for exchange of oxygen and metabolites. They contain specialized cell-cell junctions that bind adjacent cells to each other. Epithelial cells exhibit polarity which means there are intrinsic asymmetry observed in cells, either in their shape, structure, or organization of cellular components especially along the apical-basal axis. These can include receptors and channels for transportation of substances. Classi cation of Epithelia Two major types of epithelia: the Covering Epithelia and Glandular Epithelia COVERING EPITHELIA Covering epithelia are sheets of tissue that cover the external surfaces (skin, lungs, gut) and line the internal cavities (blood and lymphatic vessels, pleura) of the body. fi fi  This type can be classi ed according to the number of layers: simple or strati ed; and according to shape: squamous, cuboidal, columnar. filtrationador · i · GLANDULAR EPITHELIA · fi  These are glands consists of one or more cells that produce and secrete a speci c - product. Are classi ed into two groups based on characteristics: where they release their product, glands can be endocrine (lack ducts and secrete their products hormones directly into the bloodstream) or exocrine (with ducts) ; and the number of cells they contain, glands can be unicellular (one-celled)or multicellular (more than one cell). BONE TISSUES Muscle tissue is composed of cells that optimize the universal cell property of contractility. As in all cells, actin micro laments and associated proteins generate the forces necessary for the muscle contraction, which drives movement within organ systems, of blood, and of the body as a whole. There are three types of muscle tissue that can be distinguished on the basis of morphologic and functional characteristics, with the structure of each adapted to its physiologic role. 1. Skeletal muscle contains bundles of very long, multinucleated cells with cross-striations. Their contraction is quick, forceful, and usually under voluntary control. 2. Cardiac muscle also has cross-striations and is composed of elongated, often branched cells bound to one another at structures called intercalated discs which are unique to cardiac muscle. Contraction is involuntary, vigorous, and rhythmic. 3. Smooth muscle consists of collections of fusiform cells which lack striations and have slow, involuntary contractions. CONNECTIVE TISSUE This is the most abundant and widely distributed of the primary tissues. Its functions include binding and supporting; protection ; insulation; storing reserve fuel and transporting fi fi substances within the body. All connective tissue originate from mesoderm germ layers. Two major categories of connective tissue are Embryonic and Adult connective tissue. Embryonic connective tissue include Mesenchyme and Mucous connective tissue. By eight weeks of development most of the embryonic tissue has become specialized to form the types of connective tissue seen in the adults. CONNECTIVE TISSUE PROPER loose irregular connective tissue: contains many cells, with loose arrangement of ber and moderately viscous uid matrix dense irregular connective tissue: contains a dense woven network of collagenous (and some elastic) bers in a viscous matrix. Found in joint capsules, in the connective tissue that envelops muscles (muscle fascia), and it forms dermis of skin. It is impact resistant. https://www.histology.leeds.ac.uk/tissue_types/connective/connective_tissue_types.php LOOSE CONNECTIVE TISSUE Areolar also called Loose connective tissue(LCT), function for binding and packing; protection & nourishments; holds uids, secretes heparin and located deep to skin, surrounding muscles, vessels and organs Adipose/adipocytes, are fat cells. Two types are white fat cells, which are the most common type in adults and brown fat cells which are are smaller than white adipocytes and present in large amounts in the new-born, but restricted to areas around kidney, aorta and regions of the neck and mediastinum of an adult.https://www.histology.leeds.ac.uk/ tissue_types/connective/connective_tissue_types.php Reticular, a type of loose connective tissue in which reticular bers are the most prominent brous component, forms the supporting framework of the lymphoid organs (lymph nodes, spleen, tonsils), bone marrow and liver. https:// histologylab.ctl.columbia.edu/lab03/reticular-connective-tissue/ DENSE CONNECTIVE TISSUE This is enriched in collagen bers with little ground substance. If the closely packed bundles of bers are located in one direction, like in tendons it is called regular; if oriented fi fi fi fl fi fl  in multiple directions like in dermis it is referred to as irregular. http://medcell.med.yale.edu/ histology/connective_tissue_lab.php# Elastic connective tissue: for exibility and distensibility and located in the arteries , larynx, trachea and bronchi. SPECIALIZED CONNECTIVE TISSUE Cartilage is a connective tissue with a large amount of the matrix and variable amounts of bers. The cells, called chondrocytes, make the matrix and bers of the tissue. Chondrocytes are found in spaces within the tissue called lacunae. Cartilage is avascular and its cells rely on diffusion for nutrients. Because of this, damaged cartilage heals poorly after injury. Cartilage occurs where exibility is required. ·. II. BONE Bones support and protect the body and its organs. They also produce various blood fi fl fl cells, store minerals, and provide support for mobility in conjunction with muscle. Bone is made of bone tissue, a type of dense connective tissue. Bone (osseous) tissue is the structural and supportive connective tissue of the body that forms the rigid part of the bones that make up the skeleton. Overall, the bones of the body are an organ made up of bone tissue, bone marrow, blood vessels, epithelium, and nerves. There are two types of bone tissue: cortical and cancellous bone. Cortical bone is compact bone, while cancellous bone is trabecular and spongy bone. Cortical bone forms the extremely hard exterior while cancellous bone lls the interior. The tissues are biologically identical but differ in the arrangement of their microstructure. Blood is considered a connective tissue because it has a matrix. The living cell types are red blood cells, also called erythrocytes, and white blood cells, also called leukocytes. The uid portion of whole blood, its matrix, is commonly called plasma. In humans, all blood cells originate from hematopoietic stem cells. Its is estimated that about 95 percent of the body's blood cells are produced in the bone marrow. In an adult, most of the bone marrow is concentrated in the breastbone and in the bones of the spine and pelvis. Several other organs help to regulate the production of blood cells such as liver and lymphatic system structures (lymph nodes, spleen andthymus). The human nervous system correlates, coordinates, and reacts to impulses transmitted by sensory receptors known as nerves. Nerve tissue is distributed throughout the body as an integrated communi-cations network. Anatomically, the two major divisions of the nervous system are: 1. Central Nervous System(CNS), consisting of the brain and spinal cord 2.Peripheral nervous system(PNS) composed of the cranial, spinal and peripheral nerves conducting to and from the CNS(sensory and motor nerves, respectively) and ganglia that are small aggregate of nerve cells outside the CNS. The CNS is the processing center of the body and consists of the brain and the spinal cord. Both of these are protected by three layers of membranes known as meninges. In terms of tissue, the CNS is divided into grey matter and white matter fi Grey matter contains the cell bodies (perikarya) of neurons and the supporting cells (neuroglia) as well as unmyelinated dendrites. White matter does not contain any cell bodies, but mostly contains myelinated nerve bres. The central region of the spinal cord is grey matter, and the surrounding region is white matter. https://www.histology.leeds.ac.uk/ tissue_types/nerves/nerves_cns.php The functional division of nervous system is the Autonomic nervous system. Structures within the brains are ANS control centers and speci c nerves are the pathways for conductions of autonomic nerve impulse. This ANS functions automatically to speed or slow down body activities. Synapses are specialized sites for chemical or electrical transmission for communication between neurons, interneurons, and effector cells, such as the muscle bers or glands At each synapse, there is a presynaptic neuron and a postsynaptic neuron (or other cell). The synaptic terminals of the axon of the presynaptic terminal form the synapse with the dendrites, soma, or sometimes the axon of the postsynaptic neuron, or a part of another type of cell such as a muscle cell. The synaptic terminals contain vesicles lled with chemicals called neurotransmitters. When the electrochemical signal moving down the axon reaches the synapse, the vesicles fuse with the membrane, and neurotransmitters are released, which diffuse across the synapse and bind to receptors on the membrane of the postsynaptic cell, potentially initiating a response in that cell. That response in the postsynaptic cell might include further propagation of an electrochemical signal to transmit information or contraction of a muscle ber fi fi fi