Cell Biology

Topics: Cell, Epithelium, Cell membrane Pages: 31 (8110 words) Published: May 22, 2013
Task one:

* Light Microscopy: Drawing of plant and animal cells

Plant Cell First Magnification x 40

Plant cell Second Magnification x 100

Actual size= Image sizeMagnification

Actual size=62.5 mm100

Actual size=0.625 x 1,000

Actual size=625 um
Plant Tissue in Magnification x100

Plant cell Third Magnification x400

Animal Cell Magnification x40

Animal Cell Magnification x 100

Animal Cell Magnification x400

As shown by the diagrams of pant and animal cells as seen under light microscope there are few differences between the cells of each Kingdom. The cells of each Kingdom share commonalities in having a nucleus, cell membrane and cytoplasm. However, the plant cell has a cell wall, lacking from the animal cell, as well as a cell membrane. Another difference is the shape of the cells; the animal cell is relatively spherical whereas the plant cell is cuboidal in shape.

Task two:

i. Name and describe the four main types of tissue in animals, stating their functions, their location in the body, and give two examples of each type

Tissues are an aggregate of specialized cells that have both a similar structure and function. An aggregate of similar tissue are called organs. The Animalia Kingdom has four main types of tissue:

* Epithelium Tissue

Description – epithelium tissue are innervated, avascular, membranous tissue with very little by way of extracellular matrix. They are dependent on underlying cells for nutrients and extraction of waste - so as to maintain homeostasis - by diffusion through the basement membrane.

Structure – epithelial tissue as formed by epithelial cells densely packed together forming a continuous sheet like tissue, which attach to each other by tight junctions and by desmosomes. The cells rest on a scaffold called a basement membrane, allowing cell growth and regeneration.

There are two classifications of epithelial tissue; they are classified according to their morphology:

Simple epithelium - are a single cell layer with each cell coming in to direct contact with the basement membrane and are found lining the internal organs where epithelial tissue are found.

Stratified epithelium – are multi cell layered and found on areas of the body that need to withstand trauma, be it physical or chemical.

Location - epithelium tissue is to be found lining the cavities, structures and organs that come in to contact with the external environment, such as the skin, or the lining of the intestines, or bronchia and trachea, to use some examples.

Functions of epithelium tissue:

* In glands, specialized epithelial tissues secrete chemical substances such as lubricating fluids, hormones and enzymes;

* Epithelial tissue absorbs nutrients from the small intestines;

* Excretion of waste products in the kidney, and the removal of foreign bodies in the respiratory system;

* The diffusion of gases, liquids and nutrients;

* Specialized epithelium contains nerve endings in the sensory organs and provides sensation to the organism;

* Protection of the underlying cells from physical trauma, radiation, harmful chemicals, invading pathogens, and excessive water loss;

* Reduces friction in the circulatory system, which aids the movement of blood around the body.

Two examples of epithelium tissue I will describe are:

* Squamous Epithelium – squamous epithelial tissue is a thin, flat, sheet-like tissue often described as scale like; this allows the tissue to have a large surface area. They are often found on the skin and in the kidneys, heart, lungs, or in cavities such as the mouth and nose.

* Columnar Epithelium – made from elongated, narrow and connected in tight junction, thus column like cells. Columnar epithelial tissue has a mainly protective function, they are found in intestinal lining so as to prevent digestion of harmful bacteria; however, they can serve a function in the sensory...
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