Tissue Histology

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Chapter 5

• Tissue Histology

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Epithelial Tissues

• Characteristics
• Covers organs, forms inner lining of body
  cavities, and lines hollow organs
• Always has a surface exposed to the outside or an
  internal space.
• Basement Membrane Thin non living layer that
  anchors the tissue to connective tissue below.
• Lack blood vessels
• Nutrients get to epithelium through diffusion
  from connective tissues
• Rapid division of new cells to replace old tissue
  cells

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Types of Epithelial Tissues
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Types of Epithelium
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Epithelial Tissue Simple Squamous Epithelium

• Single Thin layer of flattened cells
• Nuclei are broad and thin
• Found in sites of filtration and diffusion
• Alveoli of Lungs
• Lymph vessels
• Capillaries
• Covers membranes that line body cavities

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Epithelial Tissue Simple Cuboidal Epithelium

• Single layer of cube-shaped cells
• Centrally located spherical nuclei
• Function is secretion and absorption
• Found
• Covering ovaries
• Lines most kidney tubules
• Ducts of glands
• Salivary
• Thyroid
• Pancreas
• Liver

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Epithelial Tissue Simple Columnar Epithelium

• Elongated cells
• Single layer of cells
• Nuclei located near basement membrane
• Tissue is thick to protect underlying tissues
• Found
• Most of the digestive tract
• Functions
• Absorption containing microvilli
• Secretion and production of mucus and digestive
  enzymes through goblet cells

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Epithelial Tissue Pseudostratified Squamous
Epithelium

• Appear layered but are not
• Nuclei at different levels with each cell
• Possess Cilia
• Goblet cells secrete mucus
• Found
• Passages of respiratory system

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Epithelial Tissue Stratified Squamous Epithelium

• Layered or Stratified
• Thick
• Cells towards the top flattened
• Found
• Epidermis of skin (keratinized)
• Mouth
• Vagina
• Anal canal
• throat

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Epithelial Tissue Stratified Cuboidal Epithelium

• Two to three layers of cuboidal cells
• Provides more protection than a single layer
• Found
• Larger ducts of mammary glands, sweat glands,
  salivary glands and pancreas
• Ovarian follicles
• Seminiferous tubules
• Vas Deferens

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Epithelial Tissue Transitional Epithelium

• Changes in response to tension
• Found in organs where the walls contract or
  stretch
• Provides protective barrier against unwanted
  diffusion
• Found In
• Urinary bladder
• Ureter
• Urethra

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Epithelial Tissue Glandular Epithelium

• Composed of cells that produce and secrete
  substances into ducts or body fluids
• Found within columnar and cuboidal epithelia
• Exocrine and Endocrine glands
• Types of exocrine Glands
• Merocrine releases watery, protein rich fluids
• Salivary glands, pancreatic glands, and sweat
  glands of skin
• Apocrine loses small portions of their cell
  bodies.
• Mammary glands and ceruminous glands of ear canal
• Holocrine entire cell lyses during secretion
• Sebacious glands of skin

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Epithelial Tissues Glandular Epithelium
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Connective Tissue

• Bind structures
• Support and protect parts of the body
• Serve as framework
• Connective Tissue Cells are further apart and
  have an abundant matrix
• Can usually divide
• Most have a good blood supply
• Some quite rigid others are flexible

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Connective Tissue Cells

• 3 Types of Cells
• Fibroblasts
• Fixed Cell
• Star shaped
• Produces fibers

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Connective Tissue Cells

• Macrophages
• Originate as WBCs
• Carry out phagocytosis
• Wandering Cells
• Function as scavenger and defensive cells

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Connective Tissue Cells

• Mast Cells
• Large and widely distributed in connective tissue
• Found near blood vessels
• Release Heparin which prevents clotting and
  Histamine which is involved in the inflammatory
  response

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Connective Tissue Fibers

• Fibroblasts produce three types of fibers
• Collagenous Fiber
• Thick threads of protein
• Held together in long parallel bundles
• Flexible but only slightly elastic
• Resist considerable tension
• Ligaments and Tendons

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Connective Tissue Fibers

• Elastic Fibers
• Elastin
• Thin fibers
• Branch forming networks
• Weaker
• Stretch easily and resume original shape
• Found in vocal cords

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Connective Tissue Fibers

• Reticular Fibers
• Very thin collagenous fibers
• Highly Branched
• Form Delicate networks
• Found in Lymph Nodes

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Connective Tissue Loose Connective Tissue

• Also known as Areolar Tissue
• Forms delicate thin membranes within the body
• Composed mainly of fibroblasts
• Gel-like matrix with collagenous and elastic
  fibers
• Many Blood Vessels
• Functions
• Binds Skin to underlying organs
• Fills space between muscles
• Beneath epithelium

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Connective Tissue Adipose Tissue

• Fat tissue
• Stores fat in droplets within cytoplasm
• Lies beneath the skin, between muscles, around
  kidneys, behind eyes, abdominal membranes, on the
  surface of the heart, and around joints
• Functions
• Cushion from shock
• Insulation
• Store energy

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Connective Tissue Dense Connective Tissue

• Closely packed, thick collangenous fibers
• Fine network of elastic fibers
• Relatively few cells (mostly fibroblasts)
• Very strong able to withstand pulling action
• Blood supply poor
• Function
• Binds body together (ligaments and tendons)
• Found in sclera of eyeball
• Deeper skin layers

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Connective TissueCartilage

• Rigid connective tissue
• Provides support
• Serves as a framework
• Protects underlying organs and tissues
• Structural model for developing bone
• Largely composed of collagen fibers in gel like
  ground substance
• Cartilage Cells Chondrocytes
• Enclosed in Perchondrium which contains blood
  vessels, but cartilage lacks a direct blood
  supply
• Three Types of Cartilage are distinguished by
  their matrix
• Three Types of Cartilage are
• Hyaline cartilage
• Elastic cartilage
• Fibro cartilage

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Connective Tissue Hyaline Cartilage

• Very fine collagenous fibers in matrix
• Looks like white glass
• Ends of bones, nose, supporting rings of trachea
• Important to bone growth

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Connective Tissue Elastic Cartilage

• Dense network of elastic fibers
• More flexible than hyaline
• External ear (pinna)
• Parts of larynx

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Connective Tissue Fibrocartilage

• Tough tissue
• Many collagen fibers
• Shock absorber
• Forms pads between bones of vertebrae
• Cushions bones in knees and pelvic girdle

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Connective Tissue Bone

• Most rigid of the connective tissues
• Hardness is due to calcium phosphate and calcium
  carbonate between cells
• Matrix also contain collagen
• Bone matrix is deposited in layers called
  lamellae, which wrap around osteonic canals
  (haversian canals)
• Contains nerves and blood vessels
• Bones cells (osteocytes) located in lacunae
• Have cytoplasmic processes called cannaliculi
• Allows for material to move rapidly between cells
• Osteon basic unit of bone
• Heals more rapidly than cartilage
• Functions
• Support
• Frameworks
• Produces blood cells
• Stores fat and minerals (calcium and phosphorous)

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Connective Tissue Bone
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Connective Tissue Blood

• Transports a variety of materials between tissues
  and the external environment
• Helps maintain a stable internal environment.
• Composed of
• Formed Elements
• Red blood cells
• White blood cells
• Cell Fragments
• Platelets
• Formed in red marrow of long bones

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Connective Tissue Blood
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Muscle Tissue Skeletal Muscle

• Found in muscle attached to bone
• Voluntary muscle
• Striated
• Each cell has many nuclei

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Muscle Tissue Smooth Muscle

• Lacks striations
• Involuntary
• Single centrally located nucleus
• Found in digestive tract (peristalsis)
• Blood vessels
• Urinary bladder

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Muscle Tissue Cardiac Tissue

• Involuntary
• Self contracting
• Striated and branching
• Has intercalated disks separated cells
• Found in the heart

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Nervous Tissue

• Found in the brain, spinal cord and nerves
• Basic cell neuron
• Function sense changes in the environment
• Coordinate, regulate and integrate many functions
  within the body
• Neuroglial cells
• support and bind parts of nervous tissue
• Carry out phagocytosis
• Supply nutrients to neurons by connecting them to
  blood vessels