HISTOLOGY

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HISTOLOGY
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I. Introduction

• Histology study of tissues
• Have 4 basic types of tissue
• Epithelial
• Covers exposed areas
• Forms glands
• Lines internal passageways and chambers

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• 2. Connective Tissue
• Fills internal spaces
• Provides structural support for other tissues
• Transports materials within the body
• Stores energy
• 3. Muscle Tissue
• Contracts to perform specific movement
• Generates heat to warm the body
• 4. Neural Tissue
• Carries information from one part of the body to
  another by electrical impulses

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II. Epithelial Tissue

• Made up of glands and epithelia
• Covers every exposed body surface
• Epithelium layer of cells that form a barrier
  with specific properties
• Glands secretory structures derived from
  epithelia
• Also lines digestive, respiratory, reproductive
  and urinary tracts

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• Also in internal cavities and passageways (chest,
  brain, eyes, ears)
• Characteristics of Epithelia
• Cellularity cells are bound closely together by
  cell junctions
• Polarity Apical surface (exposed) faces the
  exterior of the body or an internal space. Basal
  surface (attached) to underlying tissues.
  Organelles are spaced out evenly between

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• 3. Attachment basal surface is connected to a
  basement membrane
• 4. Avascularity has no blood vessels
  (nutrients from osmosis and diffusion)
• 5. Regeneration epithelial cells at the
  apical surface are continuously replaced
• Functions of Epithelial Tissues
• 1. Physical protection from abrasion,
  dehydration and destruction by chemicals

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• 2. Control permeability
• Any substance that enters or leaves the body must
  pass through the epithelium
• Permeability varies
• Stimuli can regulate it
• 3. Provide sensation large sensory nerve
  supply

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• 4. Produce specialized secretions
• Glands epithelial cells that produce secretions
• 2 kinds exocrine (discharge onto surface of the
  skin) and endocrine (release into surrounding
  interstitial fluid or blood)
• Specialization of Epithelial Cells
• 1. production of secretions
• 2. movement of fluids over epithelial surface
• 3. movement of fluids through epithelium
• 4. many have microvilli

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• 4. stereocilia (long no movement) male repro
  tract and inner ear
• 5. ciliated epithelium 250 cilia that beat in
  the same way to move the substance
• Classification
• Classified according to the number of layers and
  the shape of the exposed cells
• 2 types of layers
• 1. simple single layer of cells of the same
  shape (ex internal compartments, passageways,
  chambers of heart)

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• 2. stratified many layers of cells of
• the same shape (ex skin mouth)
• 3. transitional several layers of cells of
  different shapes
• 3 cell shapes
• 1. squamous flat scalelike (eggs)
• 2. cuboidal cube shaped
• 3. columnar higher than wider columns

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• Closer look at tissues
• A. Squamous epithelium
• Cells are thin, flat, irregular in shape
• Nuclei in thickest portion
• Types
• 1. Simple Squamous Epithelium
• single layer of thin, irregular cells
• Most delicate
• In protective areas where absorption takes place
  or where a slick surface reduces friction
• Air sacs of lungs, walls of capillaries
• Mesothelium lines ventral cavity
• Endothelium lines heart and blood vessels

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SIMPLE SQUAMOUS EPITHELIUM
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• 2. Stratified Squamous Epithelium
• Several layers
• Protection at sites of abuse (skin)
• Surface of skin, mouth, anus, esophagus
• Keratin is found on cells where dehydration and
  stress are common. Causes to be tough and
  decreases dehydration
• Nonkeratinized will dry out if not kept moist
  (oral cavity, vagina, anus, pharynx, esophagus)

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STRATIFIED SQUAMOUS EPITHELIUM
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• B. Cuboidal epithelium
• Hexagonal boxes
• Nuclei near center
• Types
• 1. Simple cuboidal epithelium
• Limited protection
• Found where absorption or secretion occurs
• Glands, ducts or parts of the kidney, thyroid
  glands

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SIMPLE CUBOIDAL
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• 2. Stratified cuboidal epithelium
• Rare
• Ducts in sweat glands and mammary glands
• 3. Transitional epithelium
• Tolerates stretching
• Appears as if changing as stretching
• Usually 10 layers of cuboidal cells of varying
  shapes when not stretched. Stretches so tissue
  expands, the layer decrease and the cells change
  shape from cuboidal to squamous
• Urinary bladder, renal pelvis, ureters

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STRATIFED CUIBOIDAL
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TRANSITIONAL
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• C. Columnar epithelia
• Hexagonal but taller and slender
• Nuclei crowded into narrow band close to
  basement membrane
• Higher than wider
• Types
• 1. Simple columnar epithelium
• Single layer of tall cells that fit closely
  together
• Found where absorption or secretion occurs
• Digestive tracts (stomach, intestine,
  gallbladder, uterine tubes)
• Helps with protection

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SIMPLE COLUMNAR
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• 2. Pseudostratified columnar epithelium
• Distance between cell nuclei and surface varies
  so it looks like epithelium is stratified
• Typically has cilia
• Protection and secretion
• Nasal cavity, trachea, bronchi, portions of male
  reproduction tract
• 3. Stratified columnar epithelium
• Rare
• Protection
• Pharynx, epiglottis, urethra and anus
• If has multiple layers, only superficial cells
  are columnar

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PSEUDOSTRATIFIED COLUMNAR
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• D. Glandular Epithelia
• Produce secretions
• Can be exocrine or endocrine
• Generally cuboidal in shape
• Types
• 1. Endocrine Glands
• Release into interstitial fluid or blood
• Ductless glands no endocrine ducts into which
  secretions are released
• Ex hormones
• Pancreas, thyroids, pituitary gland

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• 2. Exocrine Glands
• Secretions are discharged onto the surface
• Release into ducts that empty onto the surface
• Ex sweat, saliva, tears

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III. Connective Tissue

• Support
• Exs bone, fat and blood
• All have 3 basic components
• Specialized cells
• Extracellular protein fibers
• Ground substance
• Matrix extracellular fluid and ground substance

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• Found throughout the body but never exposed to
  outside environment
• Vascular
• Most abundant
• Exists in many varied forms
• Holds internal organs together and gives them
  shape
• Skin, membranes, muscles, bones, nerves internal
  fluids
• Differs from epithelial in arrangement, variety
  of cells and amount of matrix

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• Contain sensory receptors that provide pain,
  pressure and temperature
• Main functions
• 1. Structural framework
• 2. Transport fluid from 1 region of the body to
  another
• 3. Protects organs
• 4. Supports, surrounds and connect other tissues
• 5. Store energy
• 6. Defend body

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• 3 classifications of Connective Tissue
• 1. Connective Tissue Proper
• Differ in number of cells
• Types
• a. loose connective tissue
• b. dense connective tissue
• 2. Fluid Connective Tissue
• Blood
• Lymph
• 3. Supporting Connective Tissue
• Cartilage
• Bone

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• Closer look
• A. Connective Tissue Proper
• diverse cell population, viscous ground
  substance and extracellular fibers
• Cell population
• 1. fibroblasts only cell that is present in
  every connective tissue proper
• 2. macrophages engulf pathogens
• 3. adipocytes fat cells
• 4. Lymphocytes migrate turn to plasma cells
  when there is tissue damage

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• Connective tissue fibers 3 types
• 1. Collagen fibers
• Most abundant
• Strength
• Flexible but strong
• Resistant to stretching
• 2. Reticular fibers
• Thinner
• Tough but flexible framework
• 3. Elastic fibers
• Can stretch and return to normal size

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• 2 types of
• 1. Loose Fibrous Connective Tissue (Areolar)
• Glue gives form to internal organs
• Has all three fibers here
• Fills space between organs cushions
• Can distort without damage
• Forms a layer that separates skin from deeper
  structures
• 2 subtypes of
• a. Adipose tissue
• Fat tissue
• Protection and isolation
• b. Reticular tissue
• Spleen and liver
• Fibers create stroma supports cells

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AREOLAR
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ADIPOSE TISSUE
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• 2. Dense Fibrous Connective Tissue
• Collagen fibers- dominant
• 2 subtypes
• a. Dense Regular
• Fibers aligned parallel
• Tendons attach skeletal muscle to bones
• Ligaments connect bones to each other
• b. Dense Irregular
• Interwoven meshwork
• Strength and support for areas that receive
  stress from many directions
• Surrounds some internal organs liver, kidney
  and spleen

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DENSE IRREGULAR
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• B. Fluid Connective Tissue
• Blood and lymph have cells in a fluid matrix
• Types
• 1. Blood
• Liquid
• Transportation and protective function
• 2 cell types found in blood
• a. Erythrocyte RBC transport O and CO2
• b. Leukocyte WBC immune system
• Plasma watery ground substance in blood
• Platelets help with clotting

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• 2. Lymph
• Forms as interstitial fluid enters passageways
  that return it to the cardiovascular system
• C. Supporting Connective Tissue
• Cartilage and bone
• Strong framework
• Types
• Cartilage
• Matrix firm
• Chondrocytes (cartilage cells) found throughout
  the matrix
• Cells live in pockets lacunae
• Avascular

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• Nutrients and wastes exchange by diffusion in
  membranes
• Subtypes
• a. Hyaline Cartilage most common
• Found
• 1. connection between ribs and sternum
• 2. nasal cartilage
• 3. covers ends of bones
• b. Elastic Cartilage
• Numerous elastic fibers resistant and flexible
• External flaps of ears, epiglottis, larynx
• c. Fibrocartilage
• Collagen fibers
• between spinal vertebrae, between pubic bones

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HYALINE CARTILAGE
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ELASTIC CARTILAGE
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FIBROCARTILAGE
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• 2. Bone (Osseous Tissue)
• Highly specialized
• Matrix hard, calcified
• Matrix forms blocks Haversian System
• Small amount of ground substance
• Matrix made up of collagen fibers and Ca salts
• Minerals surround fibers to make strong
• Lacunae (pockets in matrix) house osteocytes
  (bone cells)
• Canaliculi passageway
• Bone covered by periostenum (except at joints)

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• Membranes
• Epithelia and connective tissue combine to form
• Cover and protect
• 4 types
• 1. Mucous Membrane
• Lines cavities that communicate with the exterior
  (digestive, respiratory)
• Surfaces kept moist
• Many lined by epithelial that perform absorptive
  and secretory functions
• Lamina propia connective tissue part

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• 2. Serous Membrane
• Line sealed internal divisions of ventral body
  cavity
• 3 types
• a. pleura pleural cavity
• b. peritoneum lines peritoneal cavity and
  internal organs
• c. pericardium pericardial cavity
• Very thin but firmly attached
• Minimizes friction
• Fluid forms on surface to keep moist and slippery

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• 3. Cutaneous Membrane
• Skin
• Covers surface of body
• Made from stratified squamous and a layer of
  loose connective tissue reinforced by underlying
  dense irregular connective tissue
• Thick, waterproof, dry
• 4. Synovial Membrane
• Bones contact each other at joints
• Joints that permit movement contain a cavity
  lined by a synovial membrane
• Incomplete layer of squamous or cuboidal cells
• Specialized connective tissue

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• Connective Tissue Framework of Body
• Makes up internal framework
• Layers connect organs within the dorsal and
  ventral body cavities with the rest of the body
• Layers
• 1. provide strength and stability
• 2. maintain positions of internal organs
• 3. route for blood vessels and nerves
• Fasciae supports organs
• 1. Superficial fascia
• Loose connective tissue and fat separate skin
  from tissues and organs
• Insulation and padding

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• 2. Deep fascia
• Dense connective tissue
• Surrounds and interconnects organs tissues
• Tendons and ligaments
• 3. Subserous fascia
• Loose connective tissue
• Between serous membrane and deep fascia

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IV. Muscle Tissue

• Specialized fro contraction
• Motion
• Contraction cell shortens
• Sarcoplasm cytoplasm
• Sarcolemma cell membrane
• Types
• 1. Skeletal Muscle Tissue
• Large muscle cells

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• Cells long and slender (muscle fibers)
• Mulitnucleated
• Fibers cannot divide but new muscle fibers can be
  produced through division of satellite cells
• Striated appearance actin and myosin filaments
• Voluntary control dont contract unless
  stimulated by nerves
• Striated voluntary control

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• 2. Cardiac Muscle
• Only in heart
• Cardiocyte
• Smaller
• Branched, striated cells with usually 1 nucleus
  but may have up to 5
• Cells form connections with one another.
  Connections at intercalated discs
• No regeneration
• Involuntary
• Striated involuntary muscle

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• 3. Smooth Muscle Tissue
• Walls of blood vessels and around hollow organs
• Bladder, respiratory, digestive and reproductive
• Small spindle shaped cells
• Single oval nucleus
• Cells can divide and regenerate
• No striations
• Not under control
• Nonstriated involuntary muscle

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V. Neural Tissue

• Specialized for conduction of nerve impulses from
  1 body region to another
• 98 of neural tissue in brain and spinal cord
• 2 types of cells
• 1. neurons conducting units
• Longest cell in the body
• Soma cell body
• Large nucleus
• Dendrites branching carry impulses
• Axon transmits impulses away from the body
• 2. neuroglia supporting cells

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