Human Body Tissue

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Human Anatomy

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Human Body Tissue

Connective Tissue.The function of connective tissue is either to join bodily structures like bones and muscles to one another or hold tissues like muscles, tendons, or even organs in their correct place in the body. It also gives reinforcement to joints, strengthening and supporting the articulations between bones. Another function of connective tissue is the transport of nutrients and metabolic by-products between the bloodstream and the tissues to which it adheres. Creating dense networks of fibres, connective tissue is made up of proteins like collagen, elastin, and intercellular fluid, its form can range from a thin sheet, to a rope of fibres, its constitution is similar throughout the body.There are four major categories of bodily tissue: nervous, epithelial, muscle, and connective tissue. Nervous tissue includes forming of the brain, spinal cord, and nerves. Epithelial tissue occurs in layers and ranges from skin to the linings of organs and vessels. Muscle tissue is like connective tissue in that it is fibrous, but it is made up of units within muscle cells known as sarcomeres that are designed to expand and contract, allowing the tissue to change in length, and it metabolises nutrients much differently than connective tissue.Connective tissue is distinguished from the other fibre types by both its form and its function. It is made up both of specialised cells that affix to other tissues as well as the extracellular matrix. Its most distinctive attribute, this matrix is made up of fluid; ground substance, a gel that contains nutrient molecules like hyaluronic acid that are composed of carbohydrates and protein. Protein based fibres like collagen and elastin. The fibres give the tissue its denseness and strength and helps connective tissue function properly.Affixing to bone, muscle, or other tissues, connective tissue is distributed throughout the body, forming tendons, ligaments, cartilage, fat, and even contributing to blood and lymphatic system. Muscle is attached to the bones, moved by tendons, thick lengths of connective tissue that pull on the bones like rope. Bones are joined to each other at joints by ligaments, which resemble narrow bands or broad sheets. Ligaments hold the bones together and prevent the joints from moving beyond their normal range of motion, they also support the bones at the joint, preventing the arm from popping out of its socket at the shoulder joint. Another function of connective tissue is to encapsulate structures like muscles and joints and transport vital nutrients between these structures and the bloodstream. While connective tissue itself tends not to be very dense with capillaries, it conducts oxygen and nutrients from nearby capillary beds into the tissue to which it attaches. When waste products are removed from tissues, the connective tissue moves it back into the bloodstream for removal from the body.Connective tissue contributes to energy storage. An adipose tissue or fat is a form of connective tissue. As well as immune function, as many types of immune cells, such as those that create scar tissue, are forms of connective tissue. Connective tissue gives many organs their shape and holds them in place in their correct body cavities. By forming sacs that contain the organs and attach to nearby structures so they do not simply float about freely. (Grant, A. 2011).

Epithelial Tissue.Epithelial tissue covers the outside of the body and lines organs, vessels, blood, lymph, and cavities. Epithelial cells form the thin layer of cells known as the endothelium, which is continuous with the inner tissue lining of organs such as the brain, lungs, skin, and heart. The free surface of epithelial tissue is usually exposed to fluid or the air, while the bottom surface is attached to a basement membrane.Cells in epithelial tissue are very closely packed together and joined with little space between them. With its tightly packed structure, epithelial tissue serves a barrier and protective function. The skin is composed of a layer of epithelial tissue the epidermis that is supported by a layer of connective tissue. It protects the internal structures of the body from damage and dehydration. Epithelial tissue also helps to protect against microorganisms. The skin is the body's first line of defence against bacteria, viruses, and other microbes.Epithelial tissue functions to absorb, secrete, and excrete substances. In the intestines, this tissue absorbs nutrients during digestion. Epithelial tissue in glands secrete hormones, enzymes, and other substances. Epithelial tissue in the kidneys excrete wastes, and in the sweat glands excrete perspiration. Epithelial tissue also has a sensory function it contains sensory nerves in areas including the skin, tongue, nose, and ears. Ciliated epithelial tissue can be found in areas such as the female reproductive tract and the respiratory tract. Cilia are hair-like protrusions that help propel substances, such as dust particles or female gametes, in the correct direction.Epithelia are classified based on the shape of the cells on the free surface, as well as the number of cell layers. These types are: Simple Epithelium which contains a single layer of cells, therefore ideally suited to be a membrane where substances are exchanged. Stratified Epithelium contains multiple layers of cells, which can be replaced continuously, making it suitable as a protective covering of the skin. Pseudostratified Epithelium appears to be stratified, but is not. The single layer in this tissue contains nuclei that are arranged at various levels, giving the appearance of it being stratified. Epithelial tissues have little mechanical strength, supported by and attached to underlying connective tissue by the basement membrane. Basement membrane is a continues sheet made up of collagen and other proteins.Epithelial tissues create barriers, that keep different body systems separate. They have several other functions. The epithelial cells that line the mammalian respiratory tract inhale dust, sweep it away from the lungs and out to the throat where it is then swallowed.Epithelial tissue functions in the transportation of substances across the membranes. Epithelium is in organs, including the digestive tract, which must absorb water and digest food. Epithelial tissue forms glands that secrete hormones and enzymes. (Senior, K. 2008).

Nervous Tissue.Nervous tissue, is a component of nervous system, made up of the neurons. Some of the forms of neuroglia are astrocytes provide metabolic support to nervous tissue, oligodendrocytes, support axons, and microglia, repair the damage of neurons. Some glial cells, known as astrocytes, are found in the brain and spinal cord and form the blood brain barrier. Oligodendrocytes found in the central nervous system and cells of the peripheral nervous system wrap around some neuronal axons to form an insulating coat known as the myelin sheath. Other functions of glial cells include nervous system repair and protection against microorganismsmany neurons and supportive cells, called neuroglia. The main function of nervous tissue is to perceive stimuli and generate nerve impulses to various organs of the body.Nervous tissue is the primary tissue that composes the central nervous system and the peripheral nervous system. Neurons are the basic unit of nervous tissue. They are responsible for sensing stimuli and transmitting signals to and from various parts of an organism. In addition to neurons, specialised cells known as glial cells serve to support nerve cells. As structure and function are very much intertwined, the structure of a neuron is uniquely suited to its function within nervous tissue.A neuron consists of two major parts: The Cell Body, the central cell body contains the neurons nucleus, including cytoplasm and other organelles. Like in any other cell, the cell body is responsible for controlling metabolic activities.It powers the neuron by synthesizing energy and oversees the neuron's growth and repair. The Nerve Processes, are finger like projections from the cell body. They can conduct and transmit signals. There are two types: Axons, they carry signals away from the cell body. Dendrites, carry signals towards the cell body. Dendrites are the receptors of a neuron that receive electrical signals from other neurons. Dendritic Spines, increase the surface area of the dendrite vastly, helping to receive impulses from other axons. The axon is covered with a white fatty layer known as the myelin sheath. It serves two major functions, protecting and insulating the axon and accelerating the electrical signals during transmission.Neurons usually have one axon which can be branched. Axons terminate at a synapse through which the signal is sent to the next cell, most often through a dendrite. Unlike axons, dendrites are usually more numerous, shorter and more branched. As with other structures in organisms, there are exceptions. There are three types of neurons: sensory, motor, and interneurons. Sensory neurons transmit impulses from sensory organs, eyes and skin, to the central nervous system.These neurons are responsible for the five senses. Motor neurons transmit impulses from the brain or spinal cord toward muscles or glands. Any two neurons are connected at the synapse. This is where the electrical signal jumps from the axon terminal of one neuron to the dendrites of another neuron. Neurons are not connected; the axon and dendrites are close enough for the signal transmission to take place. Inter neurons relay impulses within the central nervous system and act as a link between sensory and motor neurons. Bundles of fibres composed of neurons form nerves.Nerves are sensory if they consist of dendrites only, motor if they consist of axons only, and mixed if they consist of both. Glial cells, called neuroglia, do not conduct nerve impulses but perform several support functions for nervous tissue. Neuroglia or glial cells are protective and supportive structures of the nervous tissue. They are found in bunches surrounding the neurons and can regenerate in case of injury. Neuroglia provide nutrition and immune protection to the neurons. They are responsible for the formation of myelin sheath and maintaining homeostasis inside the neurons. Some of the forms of neuroglia are astrocytes provide metabolic support to nervous tissue, oligodendrocytes, support axons, and microglia, repair the damage of neurons.Some glial cells, known as astrocytes, are found in the brain and spinal cord and form the blood brain barrier. Oligodendrocytes found in the central nervous system and cells of the peripheral nervous system wrap around some neuronal axons to form an insulating coat known as the myelin sheath. Other functions of glial cells include nervous system repair and protection against microorganisms. (Barbara, L. 2014).

Muscle Tissue.Muscle tissue is made of cells that are capable of contraction. Of all the different tissue types, muscle, epithelial, connective, and nervous, muscle tissue is the most abundant in the body.All muscle tissues have a superficial covering of vary thickness called fascia, made of connective tissue and laced with adipose tissue. Inside the facia, the muscle tissue is surrounded by epimysium and individual muscle bundles or fasciculus are surrounded by perimysium. Endomysium is the connective tissue that separates muscle fibers within a fasciculus. The unit of a fasciculus is a muscle fiber, or cell called myofibril. Muscle cells are like other tissues. They contain mitochondria, Golgi apparatus, ER, SER and other organelles. Muscle tissue contains numerous microfilaments composed of the contractile proteins actin and myosin. These proteins are responsible for movement in muscles.There are three major types of muscle tissue: Cardiac muscle, Skeletal muscle and Visceral muscle. Cardiac muscle is found in the heart. Cells are joined to one another by intercalated discs, which allow the synchronization of the heartbeat. Cardiac muscle is branched, striated muscle, that has a single nucleus. The cardiac muscle fibres are attached at their ends to adjoining fibres by thick plasma membranes called intercalated discs. The heart wall consists of three layers: epicardium, myocardium, and endocardium. Myocardium is the middle muscular layer of the heart. Myocardial muscle fibres carry electrical impulses through the heart, which power cardiac conduction. Skeletal muscle, is attached to bones by tendons, is controlled by the peripheral nervous system and associated with the body's voluntary movements. Skeletal muscle is striated muscle. Unlike cardiac muscle, the cells are not branched. Skeletal muscle cells are covered by connective tissue, which protects and supports muscle fibre bundles. Blood vessels and nerves run through the connective tissue supplying muscle cells with oxygen and nerve impulses that allow for muscle contraction. Skeletal muscle is organised into several muscle groups that work in a coordinated to perform body movements. Some of these groupings include head and neck muscles, facial expressions, chewing, and neck movement. Trunk muscles, move the chest, back, abdomen, and vertebral column. Upper extremity muscles, move the shoulders, arms, hands, and fingers, and lower extremity muscles move the legs, ankles, feet, and toes.Visceral muscle is found in the body including blood vessels, the bladder, digestive tract, as well as in many other hollow organs. Like cardiac muscle, most visceral muscle is regulated by the autonomic nervous system and is under involuntary control. Visceral muscle is also called smooth muscle because it doesn't have cross striations. Smooth muscle fibres are small and tapered at the ends reducing in size. Each smooth muscle has a single centrally located nucleus. Visceral muscle contracts slower than skeletal muscle, but the contraction can be sustained over a longer period. Organs of the cardiovascular system, respiratory system, digestive system, and reproductive system are lined with smooth muscle. This muscle can be described as rhythmic or tonic. Rhythmic or phasic smooth muscle contracts periodically and spends most of the time in a relaxed state. Tonic smooth muscle remains contracted for most the time and only relaxes periodically. (Barbara, L. 2014).

Human body tissue.Human body tissue consists of groups of cells with a similar structure working together for a specific function. Human body tissue is a way of describing how cells are grouped together in a highly-organized manner according to specific structure and function. These groupings of cells form tissues, which then make up organs and various parts of the body. We are composed of several distinct types of human body tissue. The four main types of tissue in a body are: Epithelial, Connective, Nervous and Muscle.

Human Body Tissue.ByJessica Bannister


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