Cells => tissues => organs => systems

Our body has varying degrees of complexity. The simplest functional unit in our body is the cell. Cells, in turn, are organised into tissues. Tissues are groups of similar cells that have a common structure and function. In fact all the tissues found in the body fall into four categories:
- nervous,
- muscle,
- epithelial and
- connective.

Two or more different types of tissues may be arranged together to form organs that perform specific tasks.

For example:

- the heart includes cardiac muscle tissue, nerve tissue, epithelial tissue that line the blood vessels, as well as fat tissue, which is a type of connective tissue.

- the eye includes , muscle tissue, nerve tissue, epithelial tissue and also connective tissue.

- the ear is also a fine example of of an organ composed of many tissues including connective tissue and nerve tissue.

Organs are in turn, organised in groups to form systems.

The systems in our bodies include:
- respiratory,
- circulatory,
- immune,
- muscular,
- excretory,
- integumentary system,
- nervous .

 
   

Activities:

- heart dissection

- eye dissection.
1) Which of the following options best represents the hierarchy of organisation in the body?
2) A structure composed of two or more tissues is known as
3) A cross section of the skin is shown on the right. The skin has groups of cells that work together to perform a specific functions that include protection from infection, dehydration and the Sun. The skin is best classified as a

 

4) A connective tissue is defined as living cells immersed in a non-living matrix. Bone, blood and cartilage are considered connective tissue.

The structure labelled "A" is best classified as a

5) The heart and blood vessels form a
6) The kidney is an organ that forms part of the
7) Nervous tissue
8) Muscle cells lined side by side all beating together can be classified as a

9) Consider the picture on the right.

a) In the order of hierarchical complexity the lungs are considered a

b) The diaphragm is considered a

c) All of the items labelled, together form a

d) What is the function of all the labelled items put together?