Development of Cell Theory

Cytology

• Scientific study of cells began with Robert Hooke
• 1663 - observed empty cell walls of cork
• Hooke coined the word, Cellulae (little cells)
• Living cells filled w/fluid later called protoplasm

Theodor Schwann

• Studied a wide range of animal tissues
• Concluded that all animals are made of cells
• Spontaneous generation - living things arise
• from nonliving matter

Louis Pasteur

• Established beyond a reasonable doubt that
• cells arise only from other cells
• Discredited spontaneous generation

Modern Cell Theory

• all living matter consists of cells
• cells are structural & functional units of life
• all cells come from pre-existing cells
• have many similarities in chemical
• composition and metabolic mechanisms

Cells shapes and sizes

There are 200 kinds of cells in the human body. They all have different variety of shapes, sizes, and functions.

Squamous, cuboidol, and columnar

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• Squamous- a thin flat scaly shape, often with a bulge where the nucleus is.
• Squamous cells line the esophagus and they form the epidermis of the skin.
• Cuboidol- Looking in frontal tissues, equal in height and width.
• Cudoidol cell shape are best represented in liver cells.
• Columnar- distinctly taller than wide. Are best shown in the stomach.

Polygonal, stellate, and spheriodal

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• Polygonal- having irregularly angular shape with 4 or 5 sides.
• Polygonal cell shapes are found in Carcinoma, which is cancer.
• Stellate- having multiple pointed processes, slightly star shaped.
• Stellate cell shapes are found in the bodies of nerve cells.
• Spheriodal- round to oval shaped, as in egg and white blood cells.

Discoid, fusiform and fibrous

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• Discoid- disc- shaped and in red blood cells.
• Fusiform- spindle shaped and elongated, with thick middle and tapered ends.
• Fusiform as in smooth muscle cells.
• Fibrous- long, and slender threadlike cells.
• Fiberous as in skeletal muscle cells.

Micrometers

• Are the most useful unit of measurement for designating cell size.
• The smallest objects most people can see are at 100 micrometers.
• Most human cells are about 10-15 micrometers wide.
• Example pg. 80, figure 3.2

Cell support

• There is a limit to how large a cell can be.
• Due to the relationship between its volume and surface area.
• A cell that is too big cannot support itself, and risks rupturing. 

Basic Components of a Cell

Cytoplasm

• Fluid between the nucleus and surface membrane.
• Originally thought to be a gelatinous mix of chemicals and vague particles.
• True identity found by the Transmission Electron Microscope (TEM).

Tranmission Electron Microscope (TEM)

• Invented mid-twentieeth century
• Uses electron beam instead of light to see ultrastructure
• Reveals far more detail due to high resolution

Scanning Electron Microscope (SEM)

• Produces dramatic 3D images
• High magnification & resolution
• Can only view surface figures

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Magnification vs Resolution

• The more detail, the better
• Enlarged images with little detail - Empty Magnification

Plasma Membrane

• Composed of proteins & lipids
• Surrounds cell
• Functions can differ from one region of a cell to another

Cytoskeleton

• Supportive frame made of
• protein filaments & tubules,
• organelles, and inclusions.
• Inclusions - foreign matter or
• stored cell products

Cytosol

• a.k.a. Intracellular fluid (ICF)
• clear gel holding cytoskeleton,
• organelles & inclusions.

Extracellular Fluid (ECF)

• All body fluids not contained in the cells
• The ECF amid the cells is also called tissue (interstitial) fluid

Illustrations

• Ultrastructure of white blood cell - pg. 80 Figure 3.3
• Light microscope vs. TEM - pg. 81 Figure 3.4
• Structure of representative cell - pg. 82 Figure 3.5