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Histology

The study of Tissues

https://www.youtube.com/watch?v=i5tR3csCWYo

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Tissue:

Groups of cells that perform a common function.

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Components:

  • Cells
  • Matrix (Intercellular substance)

Matrix

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Main Types of Tissues:

  1. Epithelial
  2. Muscular
  3. Connective
  4. Nervous

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Epithelial Tissue

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Functions

  1. Protection
  2. Secretion
  3. Excretion
  4. Absorption

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Location

  1. Covers body surfaces
  2. Covers & lines internal organs
  3. Makes up glands

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Distinguishing Characteristics

  1. Tightly packed cells
  2. Lack of blood vessels
  3. Free surface
  4. Basement membrane
  5. Readily divides

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How to identify epithelial tissue:

  1. Free surface: the one side of the tissue is always exposed.
  2. Basement membrane: the non-free surface that is attached to underlying connective tissue.
  3. Very little matrix since cells are tightly packed together.
  4. Very few blood vessels.

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Check point...is it epithelial tissue?

Yes

No

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Check point...label basement membrane and free surface.

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How to classify epithelial tissue

  1. By the number of layers.
    1. Simple = 1 layer

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b. Stratified = more than 1 layer

c. pseudostratified = appears layered because nuclei are on different levels, not truly layered

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2. By the shape.

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Check point...what shape is it?

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3. If they have cilia or not.

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4. If they are keratinized or not.

Keratinized

Cells are dead at surface, note lack of nuclei

Cells are living, note the nucleus in every cell

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Use the key to identify epithelial tissue.

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Muscle Tissue

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Function:

  • Movement

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Location:

  1. Attached to a bone (skeletal)
  2. Walls of hollow internal organs (smooth)
  3. Heart (cardiac)

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Distinguishing Characteristics:

  1. Thin elongated, cylindrical cells
  2. Elongated nuclei
  3. Contractile

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How to identify muscle tissue

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  1. Smooth Muscle Tissue
  1. Makes up walls of hollow organs
  2. Uni-nuclei
  3. Involuntary contractions

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2. Skeletal Muscle Tissue

  1. Found attached to bone
  2. Long, thread-like cells
  3. Multi-nuclei
  4. Voluntary

*Most abundant tissue in the body

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3. Cardiac Muscle Tissue

  1. Found in the heart
  2. Long, striated, branched cells
  3. Uni-nuclei
  4. Intercalated disks joining each cell
  5. Involuntary

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Check point...identify the muscle tissue

Smooth Muscle

Skeletal Muscle

Cardiac Muscle

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Connective Tissue

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Function

  1. Bind (loose and dense connective)
  2. Support (bone and cartilage)
  3. Fill spaces between structures
  4. Store fat (adipose)
  5. Produce blood cells (bone)
  6. Transport nutrients and waste (blood)

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Location

  • Widely distributed

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Distinguishing Characteristics

  1. Good blood supply
  2. Cells are not tightly packed together
  3. Matrix between cells - the abundance and consistency varies from:
  4. Fluid (blood)
  5. Semisolid (adipose)
  6. Solid (bone)

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*Warning: needles and flesh about to be shown*

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How to classify connective tissue:

  1. By the matrix and fibers it includes
    1. Protein matrix - has a dominance of protein fibers.
      1. Collagen fibers - white, thick, flexible, slightly elastic, very strong
      2. Elastin fibers - yellow, thin, very elastic, somewhat weak
      3. Reticular fibers - very thin, branched, delicate

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b. Protein/ground substance matrix - some protein fibers and a great deal of non-fibrous protein

Fibrocartilage

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c. Fluid matrix - water-based solution

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2. By the types of cells

  1. Fixed cells - reside in tissue for an extended period of time (fibroblasts, osteocytes, chondrocytes, mast cells)
  2. Wandering cells - appear in

tissue usually in response to an

injury or infection (macrophages)

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Know your connective tissue

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Fibrous Tissue

What is the difference in appearance between loose and dense connective tissue?

What is the difference between dense regular and dense irregular?

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You try it!

Word Bank: Collagen Fiber, Elastin Fiber, Fibroblast

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Adipose Tissue

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Word Bank: cell membrane, nucleus, simple cuboidal

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Cartilage Tissue

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Identify each type of cartilage.

​

Word bank: chondrocyte, lacuna, matrix

Elastic

Fibrocartilage

Hyaline cartilage

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Bone Tissue

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Label each picture.

Which letter is pointing to an osteocyte?

A

What is a lacuna?

A disc-like structure, a depression

Compact Bone

Spongy Bone

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Blood Tissue

What letter is pointing to a platelet?

C

What letter is pointing to an erythrocyte?

A

What letter is pointing to a leukocyte?

B

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Nervous Tissue

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Function:

-Transmit impulses (messages)

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Location:

  1. Brain
  2. Spinal cord
  3. Nerves

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Distinguishing characteristics:

  1. Cells have long tendrils
  2. Cells connect to each other and to other body parts

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Nervous Tissue:

Two basic type of cells are found in this tissue: neurons (impulse-conducting cells) and neuroglial cells (support cells). Neurons are large cells with nucleated bodies and projections called axons and dendrites. There are many types of neuroglial (glia) cells. They are generally smaller than neurons but much more abundant. Neuroglia cells surround and support neurons physically or biochemically.

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What number is theā€¦

Axon

Cell body

Dendrites

Neuroglial cells

Nucleus