Anatomy

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Anatomy Physiology

• Lesson 4

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HISTOLOGY

• Histology is the study of the structure of
  tissues.
• A tissue is a group of similar cells and their
  intercellular substance, function together to
  perform a specialized activity.
• Tissues in the body can be classified into four
  principle types, according to their structure and
  function.

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TYPES OF TISSUES

• Epithelial tissuecovers body surfaces, lines
  hollow organs, body cavities, and ducts, and
  forms glands.
• Connective tissueprotects and supports the body
  and its organs, binds organs together, stores
  energy reserves as fat, and provides immunity.
• Muscle tissueresponsible for movement and
  generation of force.
• Nervous tissueinitiates and transmits action
  potentials (nerve impulses) that help coordinate
  body activities.

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EPITHELIAL TISSUE

• Epithelial tissue (or epithelium) can be divided
  into two types
• Covering and lining epitheliumforms skin, outer
  covering of some organs, lines body cavities and
  the inside of the respiratory and digestive
  tracts, blood vessels, and ducts.
• Glandular epitheliumforms the secreting portion
  of glands.

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GENERAL FEATURES OF EPITHELIAL TISSUES

• Consist of mostly or entirely tightly packed
  cells with little or no extracellular material
  between cells.
• Cells are arranged in continuous sheets, in
  either single or multiple layers.
• Cell layers have an apical (free) surface, which
  is exposed to a body cavity, lining of an
  internal organ, or the exterior of the body, and
  a basal surface, which is attaced to the
  basement membrane.
• Cells have many junctions, providing secure
  attachments between cells.
• Tissues are avascularblood vessels that supply
  nutrients and remove wastes are located in the
  adjacent connective tissue. Materials move
  between epithelium and connective tissue by
  diffusion.
• Have a nerve supply.
• Diverse in originare derived from all three
  primary germ layers.

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GENERAL FEATURES OF EPITHELIAL TISSUES

• Adhere firmly to adjacent connective tissue,
  which holds the epithelium in place and prevents
  it from tearing. Connection between the
  epithelium and the connective tissue is via a
  thin basement membrane, which is composed of the
  basal lamina (collagen, laminin, and
  proteoglycans) and the reticular lamina
  (reticular fibers, fibroconectin, and
  glycoproteins). The basement membrane provides
  cell attachment and physical support for the
  epithelium, acts a filter in the kidneys, and
  guides cell migration during development and
  tissue repair.
• Have a high capacity for renewal (high mitotic
  rate) because they are subject to wear and tear
  and injury.
• Functions include protection, filtration,
  lubrication, secretion, digestion, absorption,
  transportation, excretion, sensory reception, and
  reproduction.

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EPITHELIAL TISSUE
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TYPES OF EPITHELIAL TISSUE

• Simple squamous epithelium
• Description Single layer of flat cells.
• Location Lines heart, blood vessels, lymphatic
  vessels, air sacs of lungs, glomerular capsule of
  kidneys, and inner surface of the eardrum. Forms
  epithelial layer of serous membranes.
• Function Filtration, diffusion, osmosis, and
  secretion in serous membranes.

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TYPES OF EPITHELIAL TISSUE

• Simple cuboidal epithelium
• Description Single layer of cube-shaped cells.
• Location Covers surface of ovary, lines anterior
  surface of eye lens capsule, forms pigmented
  epithelium at back of eye, lines kidney tubules
  and smaller ducts of many glands.
• Function Secretion and absorption.

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TYPES OF EPITHELIAL TISSUE

• Nonciliated simple columnar epithelium
• Description Single layer of nonciliated
  rectangular cells. Contains goblet cells
  (secrete mucus) and microvilli (fingerlike
  projections that increase the plasma membrane
  surface area) in some locations.
• Location Lines GI tract from the stomach to the
  anus, ducts of many glands, and gallbladder.
• Function Secretion and absorption.

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TYPES OF EPITHELIAL TISSUE

• Ciliated simple columnar epithelium
• Description Single layer of ciliated rectangular
  cells. Contains goblet cells in some locations.
• Location Lines a few portions of upper
  respiratory tract, Fallopian tubes, uterus, some
  paranasal sinuses, and central canal of spinal
  cord.
• Function Moves fluids or particles along a
  passageway by ciliary action.

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TYPES OF EPITHELIAL TISSUE

• Stratified squamous epithelium
• Description Multiple cell layers. Deep layers
  are cuboidal to columnar in shape. Superficial
  layers consist of squamous cells. As surface
  cells are lost, they are replaced by basal cells.
• Location Keratinizing variety forms superficial
  layer of skin. Nonkeratinizing variety lines wet
  surfaces, such as lining of the mouth, esophagus,
  part of epiglottis, vagina, and covers tongue.
• Function Protection.

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TYPES OF EPITHELIAL TISSUE

• Stratified cuboidal epithelium
• Description Two or more layers of cells in which
  the superficial cells are cube-shaped.
• Location Ducts of adult sweat glands and part of
  male urethra.
• Function Protection.

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TYPES OF EPITHELIAL TISSUE

• Stratified columnar epithelium
• Description Several layers of polyhedral cells.
  Columnar cells are only in the superficial layer.
• Location Lines part of urethra, large excretory
  ducts of some glands, small areas in anal mucus
  membrane, and part of the conjuctiva of the eye.
• Function Protection and secretion.

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TYPES OF EPITHELIAL TISSUE

• Transitional epithelium
• Description Appearance is variable. Shape of
  superficial cells ranges from squamous to
  cuboidal, depending on the degree of distention
  (stretching).
• Location Lines urinary bladder and portions of
  ureters and urethra.
• Function Permits distention.

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TYPES OF EPITHELIAL TISSUE

• Pseudostratified columnar epithelium
• Description Not a true stratified tissue.
  Nuclei of cells are at different levels. All
  cells are attached to the basement membrane, but
  not all reach the free surface.
• Location Ciliated lines most of upper
  respiratory tract. Nonciliated lines larger
  ducts of many glands, epididymis, and part of
  male urethra.
• Funtion Secretion and movement of mucus by
  ciliary action.

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TYPES OF EPITHELIAL TISSUE (GLANDULAR)

• Exocrine glands
• Description Secretory products released into
  ducts.
• Location Sweat, oil, ear wax, and mammary glands
  of the skin, digestive glands (like salivary
  glands and pancreas).
• Function Produce mucus, perspiration, oil, ear
  wax, milk, or digestive enzymes.
• Endocrine glands
• Description Secretory products (hormones)
  diffuse into blood after passing through
  extracellular fluid.
• Location Pituitary gland, pineal gland, thyroid
  and parathyroid glands, adrenal glands, pancreas,
  ovaries, testes, thymus gland, etc.
• Function Produce hormones that regulate various
  body activities.

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CONNECTIVE TISSUE

• Connective tissue is the most abundant, widely
  distributed (and diverse) tissue in the body. It
  can be divided into two classifications, with
  several subclasses
• Embryonic connective tissue
• Mesenchyme
• Mucous connective tissue
• Mature connective tissue
• Loose connective tissue
• Areolar connective tissue
• Adipose connective tissue
• Reticular connective tissue
• Dense connective tissue
• Dense regular connective tissue
• Dense irregular connective tissue
• Elastic connective tissue
• Cartilage
• Hyaline cartilage
• Fibrocartilage
• Elastic cartilage
• Bone (osseous) tissue
• Blood (vascular tissue)

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GENERAL FEATURES OF CONNECTIVE TISSUE

• Consists of three basic elements Cells, ground
  substance, and fibers. Together, the ground
  substance and fibers form the extracellular
  matrix. Connective tissue cells are surrounded
  by large amounts of matrix, so they seldom touch
  eachother.
• Connective tissues usually do not occur on free
  surfaces. However, joint cavities are lined by
  areolar connective tissue.
• Except for cartilage, connective tissue has a
  nerve supply.
• Usually is highly vascular (has a rich blood
  supply). Exceptions are cartilage (no blood
  supply) and tendons (scant blood supply).
• The matrix, which may be fluid, semifluid,
  gelatinous, fibrous, or calcified, is usually
  secreted by the connective tissue cells and
  adjacent cells and determines the tissues
  physical qualities.

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CONNECTIVE TISSUE CELLS

• Derived from embryonic mesodermal cells
  (mesenchymal cells).
• The immature cells have names that end in blast
  (fibroblasts, chondroblasts, osteoblasts). These
  cells retain the ability to undergo mitosis and
  produce matrix.
• The mature cells have names that end in cyte
  (chondrocyte, osteocyte). Mature cells have
  decreased capacity for cell division and matrix
  formation. They are mostly responsible for
  maintaining the matrix.

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CONNECTIVE TISSUE CELLS

• Some connective tissue cells include
• FibroblastsLarge, flat, spindle-shaped cells
  with branching processes. Secrete the molecules
  that form the matrix.
• Macrophages (histiocytes)Develop from monocytes
  (a type of white blood cell). Irregular shape
  with short, branching projections that engulf
  bacteria and cellular debris by phagocytosis,
  providing defense for the body. Wandering
  macrophages leave the blood and travel to
  infected tissues while fixed macrophages remain
  in certain tissues and organs.
• Plasma cellsSmall and either round or
  irregularly shaped. Develop from B lymphocytes
  (a type of white blood cell). Secrete antibodies
  and provide immunity. Found throughout the body,
  but mostly in connective tissuesespecially in
  the GI tract and mammary glands.
• Mast cellsAbundant alongside blood vessels.
  Produce histamine, which dilates small blood
  vessels during inflammation.

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CONNECTIVE TISSUE MATRIX

• Ground Substance
• Supports cells, binds them together, provides a
  medium for transport of substances between blood
  and cells, influences tissue development,
  migration, proliferation, shape, and metabolic
  functions of tissues.
• Contains a variety of large, complex molecules,
  including
• Hyaluronic acidviscous, slippery substance that
  binds cells together, lubricates joints, and help
  maintain shape of eyeball.
• Chondroitin sulfatejellylike substance that
  provides support and adhesiveness in cartilage,
  bone, skin, and blood vessels.
• Dermatan sulfateexists in skin, tendons, blood
  vessels, and heart valves.
• Keratan sulfateexists in bone, cartilage, and
  the cornea of the eye.
• Adhesion proteins(fibronectin, laminin,
  collagen, fibrinogen) interact with receptors on
  plasma membranes to anchor cells in position and
  provide traction for cell movement.

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CONNECTIVE TISSUE MATRIX

• Fibers
• Synthesized by fibroblasts. Provide strength and
  support for tissues.
• Collagen fibersat least five different types.
  Very tough and resistant to pulling forces, yet
  allow some flexibility in the tissue. Often
  occur in bundles composed of many tiny fibrils
  lying parallel to each other. Bundle arrangement
  provides great strength. Composed of the protein
  collagen (most abundant protein in the body).
  Found in most CT typesespecially bone,
  cartilage, tendons, and ligaments.
• Elastic fiberssmaller diameter than collagen
  fibers. Branch and join together to form a
  network within a tissue. Composed of the protein
  elastin and the large glycoproteins (especially
  fibrillin). Provide strength. Can be stretched
  up to 150 of their relaxed length without
  breaking. Plentiful in skin, blood vessel walls,
  and lung tissue.
• Reticular fibersconsist of collagen and a
  glycoprotein coating. Much thinner that collagen
  fibers and form a branching network. Provide
  support in blood vessel walls. Form a network
  around fat cells, nerve fibers, and skeletal and
  smooth muscle cells. Provide support and
  strength and form the stroma (supporting
  framework) of many soft organs (spleen, lymph
  nodes). Help form basement membrane.

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TYPES OF CONNECTIVE TISSUE (EMBRYONIC)

• Mesenchyme
• Description Irregularly shaped mesenchymal cells
  embedded in a semifluid ground substance that
  contain delicate reticular fibers.
• Location Deep to skin, along developing
  embryonic bones. Some mesenchymal cells found in
  adult CTespecially along blood vessels.
• Function Forms all other kinds of CT.
• Mucous connective tissue
• Description Star-shaped cells embedded in a
  viscous, jellylike ground substance that contain
  fine collagen fibers.
• Location Umbilical cord.
• Function Support.

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TYPES OF CONNECTIVE TISSUE

• Areolar connective tissue
• Description Fibers (collagen, elastic, and
  reticular) and several kinds of cells
  (fibroblasts, macrophages, plasma cells,
  adipocytes, and mast cells) embedded in a
  semifluid ground substance.
• Location Subcutaneous layer of skin, papillary
  (superficial) region of dermis of skin, mucous
  membranes, blood vessels, nerves, and around body
  organs.
• Function Strength, elasticity, support.

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TYPES OF CONNECTIVE TISSUE

• Adipose tissue
• Description Consists of adipocytes, specialized
  cells that store triglycerides (fats and oils) in
  a large central area. Nuclei are peripherally
  located.
• Location Subcutaneous skin layer, around heart
  and kidneys, yellow bone marrow of long bones,
  padding around joints, and behind eyeball in eye
  socket.
• Function Heat regulation, energy reserve,
  support and protection. In newborns, brown fat
  generates heat to help maintain body temperature.

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TYPES OF CONNECTIVE TISSUE

• Reticular connective tissue
• Description Network of interlacing reticular
  fibers and reticular cells.
• Location Stroma (framework) of liver, spleen,
  lymph nodes. Red bone marrow that gives rise to
  blood cells. Reticular lamina of basement
  membrane.
• Function Forms stroma of organs. Binds smooth
  muscle tissue cells together.

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TYPES OF CONNECTIVE TISSUE

• Dense regular connective tissue
• Description Matrix has shiny white appearance.
  Mostly composed of collagen fibers arranged in
  parallel bundles. Fibroblasts present in rows
  between bundles.
• Location Tendons, most ligaments, and
  aponeuroses (sheetlike tendons that attach muscle
  to other muscle or bones).
• Function Provides strong attachment between
  various structures.

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TYPES OF CONNECTIVE TISSUE

• Dense irregular connective tissue
• Description Predominantly collagen fibers,
  randomly arranged, and a few fibroblasts.
  Usually forms a sheet.
• Location Fascia, reticular (deeper) region of
  dermis of skin, perichondrium (membrane around
  cartilage), periosteum (membrane around bone),
  joint capsules, dura mater (outer membrane around
  brain and spinal cord), membrane capsules around
  various organs, heart valves.
• Function Provides strength.
• Elastic connective tissue
• Description Predominantly freely branching
  elastic fibers. Fibroblasts present in spaces
  between fibers.
• Location Lung tissue, walls of elastic arteries,
  trachea, bronchial tubes, true vocal cords,
  suspensory ligament of penis, and ligamenta flava
  of vertebrae (ligaments between vertebrae).
• Function Allows stretching of various organs.

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TYPES OF CONNECTIVE TISSUE

• Hyaline cartilage
• Description Bluish-white, shiny ground substance
  with fine collagen fibers. Contains numerous
  chondrocytes. Most abundant type of cartilage.
• Location Ends of long bones, anterior ends of
  ribs, nose, parts of larynx, trachea, bronchi,
  bronchial tubes, embryonic skeleton.
• Function Provides smooth surfaces for movement
  at joints, flexibility, and support.

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TYPES OF CONNECTIVE TISSUE

• Fibrocartilage
• Description Chondrocytes scattered among bundles
  of collagen fibers within the matrix.
• Location Pubic symphysis, intervertebral discs,
  menisci (cartilage pads) of knees.
• Function Support and fusion.
• Elastic cartilage
• Description Chondrocytes located in a threadlike
  network of elastic fibers within the matrix.
• Location Epiglottis of larynx, external ear,
  auditory (Eustacian) tubes.
• Function Support and shape maintenance.

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TYPES OF CONNECTIVE TISSUE

• Bone (osseous) tissue
• Description Compact bone consists of osteons
  (Haversian systems) that contain lamellae,
  lacunae, osteocytes, canaliculi, and central
  (Haversian) canals. Spongy bone consists of thin
  plates called trabeculae with red bone marrow
  between the trabeculae.
• Location Both compact and spongy bone form the
  various parts of the bodys bones.
• Function Support, protection, storage, houses
  blood-forming tissue, serves as levers that act
  with muscles to provide body movement.

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TYPES OF CONNECTIVE TISSUE

• Bone (osseous) tissue

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TYPES OF CONNECTIVE TISSUE

• Blood (vascular tissue)
• Description Plasma and formed elements. Formed
  elements are erythrocytes (red blood cells),
  leukocytes (white blood cells), and platelets.
• Location Within blood vessels (arteries,
  arterioles, capillaries, venules, and veins).
• Function Erythrocytes transport oxygen and
  carbon dioxide. Leukocytes are involved in
  phagocytosis, allergic reactions, and immunity.
  Platelets are essential for blood clotting.

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TYPES OF CONNECTIVE TISSUE

• Blood (vascular tissue)

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MEMBRANES

• Epithelial membraneThe combination of an
  epithelial layer and the underlying connective
  tissue layer. Principal epithelial membranes
  are
• Mucous membrane
• Serous membrane
• Cutaneous membraneSkin. An organ of the
  integumentary system. Will be discussed later.
• Synovial membraneContains connective tissue
  onlyno epithelium.

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MUCOUS MEMBRANES

• Line body cavities that open directly to the
  exterior (entire digestive, respiratory, and
  reproductive systems, and much of the urinary
  system).
• Consist of a lining layer of epithelium and an
  underlying layer of connective tissue
• Epithelial layer provides barrier against
  microbes and other pathogens, secretes mucus
  (moisturizes body cavities, traps particles in
  the respiratory tract, and lubricates food),
  secretes enzymes digestive enzymes, and is the
  site for food and fluid absorption in the GI
  tract.
• Connective tissue layer is called the lamina
  propria. It binds the epithelium to underlying
  structures while allowing some flexibility, holds
  blood vessels in place, and protects underlying
  muscles from abrasion or puncture. Oxygen and
  nutrients diffuse from the lamina propria to the
  epithelial layer while carbon dioxide and wastes
  diffuse in the opposite direction.

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SEROUS MEMBRANES

• Line body cavities that do not open to the
  exterior and cover the organs lying within those
  cavities.
• Composed of two layers
• Parietal layerattached to the cavity wall.
• Visceral layerattached to and covering the
  organs within the cavity.
• Epithelial layer secretes a watery fluid called
  serous fluid, which allows organs to glide freely
  against each other and against the cavity wall.
• Epithelial layer is composed of mesothelium
  (simple squamous epithelium).
• Connective tissue layer is composed of a thin
  layer of areolar CT.
• Serous membrane of the thoracic cavity is called
  the pleura, of the pericardial cavity is the
  pericardium, and of the abdominal cavity is the
  peritoneum.

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SYNOVIAL MEMBRANES

• Do not contain epithelium.
• Line cavities that do not open to the exterior.
• Line the cavities of freely movable joints,
  bursae (cushioning sacs), and tendon sheaths in
  our hands and feet.
• Composed of areolar CT, with elastic fibers and
  varying amounts of fat.
• Secrete synovial fluid, which lubricates the
  cartilage at the end of bones during movement and
  nourishes the cartilage at joints.

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MUSCLE TISSUE

• Muscle tissue consists of fibers (cells) that are
  designed to generate force for contraction. It
  provides motion, maintains posture, and generates
  heat. Muscle tissue is classified into three
  types, based on location, structure, and
  function
• Skeletal muscle tissue
• Cardiac muscle tissue
• Smooth muscle tissue

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TYPES OF MUSCLE TISSUE

• Skeletal muscle tissue
• Description Long, cylindrical, striated (having
  alternating light and dark bands) fibers with
  many peripherally located nuclei. Voluntary
  control (can be made to contract or relax by
  conscious control).
• Location Usually attached to bones by tendons.
• Function Motion, posture, heat production
  (thermogenesis).

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TYPES OF MUSCLE TISSUE

• Cardiac muscle tissue
• Description Branched, striated fibers with one
  or two centrally located nuclei. Contains
  intercalated discs (unique end-to-end attachments
  between muscle fibers). Involuntary control
  (contractions are usually not under conscious
  control).
• Location Heart wall.
• Function Pumps blood to all parts of the body.

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TYPES OF MUSCLE TISSUE

• Smooth muscle tissue
• Description Spindle-shaped, nonstriated (smooth)
  fibers with one centrally located nucleus.
  Usually involuntary control.
• Location Walls of hollow internal structures
  such as blood vessels, airways to the lungs,
  stomach, intestines, gallbladder, urinary
  bladder, and ureters.
• Function Motion (constriction of blood
  vessels/airways, propulsion of food through GI
  tract, contraction of urinary bladder/gallbladder)
  .

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NERVOUS TISSUE

• Composed of only two principal cell types
• NeuronsNerve cells. Convert stimuli into nerve
  impulses, which they conduct to other neurons,
  muscle tissue, or glands. Most neurons consist
  of
• Cell bodycontains the nucleus and other typical
  organelles.
• Dendritestapering, highly branched, usually
  short extensions that are the major input
  receiving portions of neurons.
• Axonsingle, thin, cylindrical process that may
  be very long. Output portion of a
  neuronconducts nerve impulses toward another
  neuron or other tissue.
• NeurogliaDo not generate or conduct nerve
  impulses but do perform many important support
  functions in nervous tissue.

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NERVOUS TISSUE

• Description Consists of neurons and neuroglia.
• Location Nervous system.
• Function Exhibits sensitivity to various
  stimuli, converts stimuli into nerve impulses,
  and conducts nerve impulses to other neurons,
  muscle fibers, or glands.