Exercise 6A

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Exercise 6A

• Classification of Tissues
• Note Histology is the study of tissues

Muse 2430 lab 3
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Tissues

• Tissues consist of groups of cells similar in
  structure function
• 4 main types
• Epithelial
• Connective
• Muscle
• Nervous

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Epithelial Tissues

• Cover surfaces
• Functions protection, absorption, filtration,
  excretion, secretion, sensory reception

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Epithelial Tissues

• Characteristics
• Cellularity - cells fit closely together to form
  membranes or sheets
• Polarity - always have a free surface (apical
  surface)
• Supported by connective tissue (basal surface)
• Avascular - no blood supply rely on diffusion of
  nutrients
• Regeneration - if well nourished, they can
  regenerate

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Epithelial Tissues

• Classification - based on 2 criteria
• Number of layers (arrangement)
• Cell shape

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Epithelial Tissues

• Arrangement
• Simple - 1 layer
• Stratified - gt1 layer
• Shape
• Squamous - scale-like
• Cuboidal - cube-like
• Columnar - column-shaped

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Epithelial Tissues

• Alternate arrangements
• Pseudostratified - actually simple, but cells are
  of varying height nuclei lie at different
  levels, which gives false appearance of being
  stratified often ciliated
• Transitional - stratified squamous rounded
  cells have ability to slide over one another,
  giving an organ the ability to stretch (bladder)

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Epithelial Tissues

• Glands
• Endocrine - lose surface connection excretions
  go directly into bloodstream or lymphatic vessels
• Exocrine - retain ducts secretions empty
  through ducts onto epithelial surface

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Epithelial tissues

• Simple squamous
• Single layer of flattened cells
• Disc-shaped central nuclei
• Sparse cytoplasm
• Simplest of epithelia

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Epithelial Tissues

• Simple cuboidal
• Single layer of cube-like cells
• Large, spherical, central nuclei

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Epithelial Tissues

• Simple columnar
• Single layer of tall cells
• Round to oval nuclei
• Can be ciliated

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Epithelial Tissues

• Pseudostratified columnar
• Single layer of cells of differing heights
• Nuclei at different levels
• Can be ciliated

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Epithelial Tissues

• Stratified squamous
• Several cell layers
• Basal cells cuboidal or columnar
• Surface cells squamous (named for surface layer)

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Epithelial Tissues

• Stratified cuboidal
• Typical 2 layers of cuboidal cells

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Epithelial Tissues

• Stratified columnar
• Several cell layers
• Basal cells usually cuboidal
• Surface cells columnar (named for surface cells)

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Epithelial Tissues

• Transitional (relaxed)
• Resembles both stratified squamous stratified
  cuboidal
• Basal cells cuboidal or columnar
• Surface cells dome-shaped or squamous, depending
  on amount of organ stretch

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Connective Tissues

• Most abundant tissue type
• Functions to protect, support, bind together
  other tissues
• Most have rich blood supply (few exceptions)
• Composed of many cell types
• Great deal of noncellular, nonliving material
  (matrix) between cells

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Connective Tissues

• Matrix
• Produced by the cells, then extruded
• Provides strength
• The more matrix, the stronger
• 2 components
• Ground substance - may be liquid, semi-solid,
  gel-like, or hard
• Fibers
• Collagen (white)
• Elastic (yellow)
• Reticular (fine collagen)

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Connective Tissues

• Other notes
• When matrix is firm, cells lie in cavities,
  called lacunae
• Ground substance functions as a sieve through
  which nutrients diffuse between the blood and
  cells
• Fibers make ground substance less pliable
• All types of adult connective tissue are
  variations of areolar

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Connective Tissues

• Classification
• Embryonic
• Adult
• Connective tissue proper
• Cartilage
• Bone
• Blood

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Connective Tissues

• Embryonic
• Mesenchyme

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Connective Tissues

• Connective tissue proper
• Loose
• Areolar
• Adipose
• Reticular
• Dense
• Regular
• Irregular

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Connective Tissues

• Cartilage
• Hyaline
• Elastic
• Fibrocartilage
• Bone
• Blood

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Connective Tissues

• Embryonic connective tissue mesenchyme
• Gives rise to all other connective tissue types
• Clear-appearing background
• Fine, sparse fibers

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Connective Tissues

• Connective tissue proper
• Loose
• Areolar
• Gel-like matrix
• All 3 fiber types
• Many cell types

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Connective Tissues

• Connective tissue proper
• Loose
• Adipose
• Matrix similar to areolar, but sparse
• Closely packed adipocytes
• Nuclei pushed to side by fat droplets

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Connective Tissues

• Connective tissue proper
• Loose
• Reticular
• Loose ground substance
• Reticular fibers

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Connective Tissues

• Connective tissue proper
• Dense
• Dense regular
• Primarily parallel collagen fibers
• Dense matrix

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Connective Tissues

• Connective tissue proper
• Dense
• Dense irregular
• Irregularly arranged collagen fibers
• Some elastic fibers
• Arrangement is what tells regular from irregular
• Otherwise, they look similar

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Connective Tissues

• Cartilage
• Hyaline
• Amorphous but firm matrix
• Collagen fibers form imperceptible network
• Chondrocytes lie in lacunae

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Connective Tissues

• Cartilage
• Elastic
• Similar to hyaline, but has more fibers in matrix
• Chondrocytes lie in lacunae

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Connective Tissues

• Cartilage
• Fibrocartilage
• Matrix similar to hyaline, but less firm
• Thick collagen fibers
• Chondrocytes lie in lacunae

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Connective Tissues

• Bone
• Hard, calcified matrix
• Many collagen fibers
• Osteocytes lie in lacunae
• Well vascularized

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Connective Tissues

• Blood
• Probably the most easily recognized
• Fluid matrix (plasma) containing red blood cells,
  white blood cells, platelets

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Muscle Tissues

• Highly specialized to contract
• Produces most types of body movement
• Tend to be elongated
• 3 types
• Skeletal
• Cardiac
• Smooth

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Muscle Tissues

• Skeletal
• Meat or flesh of body
• Attached to skeleton
• Under voluntary control
• Contraction moves limbs, etc.
• Cells are long, cylindrical multinucleate
• Nuclei pushed to periphery
• Striated

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Muscle Tissues

• Cardiac
• Only in heart
• Striated
• Branching, uninucleate cells
• Cells interdigitate at intercalated discs
• Involuntary control

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Muscle Tissues

• Smooth
• Also called visceral
• Mainly in walls of hollow organs
• Typically, 2 layers that run at right angles
• Contraction can constrict or dilate cavity of an
  organ
• Cells spindle-shaped, uninucleate
• Not striated

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Nervous Tissue

• Composed of 2 major cell populations
• Neuroglia - protect, support, insulate neurons
• Neurons - highly specialized to receive stimuli
  conduct impulses to all parts of body
  (irritability conductivity)

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Nervous Tissue

• Neurons
• Nucleus-containing cell body
• Cytoplasm drawn out into cell processes (can be 1
  meter long)

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