There are four main types of tissues in animals: epithelial, muscle, connective, and nervous tissue. Epithelial tissue covers surfaces and forms glands. It includes squamous, cuboidal, columnar, and glandular cells. Muscle tissue includes smooth, skeletal, and cardiac muscle that enable movement. Connective tissue binds other tissues together and includes loose connective tissue like areolar tissue, dense connective tissue like dermis, and specialized tissue like blood, bone, and cartilage. Nervous tissue forms the brain, spinal cord, and nerves to transmit electrical signals around the body.

1. ANIMAL TISSUES

2. 1. Epithelial tissue
⮚ The function of the epithelial tissue varies depending on its location.
⮚ But this epithelial tissue can be divided into two kinds:
● Simple epithelium
⮚ Consists of one cell layer.
● Stratified epithelium
⮚ Has more than one layer.
• Types of Epithelial tissue
• Squamous epithelium
• Thin flat cells that are closely packed.
• The squamous epithelial cells line the cavities of the mouth, esophagus, alveoli and blood vessels.
• This tissue gives protection against mechanical injury and also blocks the entry of organs.
• Cuboidal epithelium
• Cells that are cuboidal in shape. They are fund in the salivary glands, kidney tubules, sweat glands, etc.
• Their main function includes absorption, secretion and excretion.
• It is found on the inner side of the pancreatic ducts and salivary glands. They mainly help in protection.

3. ● Columnar epithelium
⮚ Have cells that are pillar-like and column-like.
⮚ We can find them in the lining of the stomach and intestine. Its function includes absorption and secretion.
● Ciliated epithelium
⮚ When the columnar epithelium tissues have cilia, then they are called epithelium.
⮚ They are present in the lining of the trachea, kidney tubules, etc.
⮚ The rhythmic movement of the cilia helps in the movement of material in one direction.
● Glandular epithelium
⮚ These are modified columnar epithelial tissues.
⮚ Their main function is secretion.
⮚ They are large cells that present in the tear glands, sweat glands, etc.

4. 2. Muscle tissue
⮚ The one that helps in the movement of the various body parts. They are generally attached to the bones, and thus
help in movement. There are three types of muscular tissue
● Smooth muscle - these muscle cells do not have striations or stripes. Hence, they are called smooth muscle cells.
They are also called involuntary muscles.
● Skeletal muscle- the skeletal muscles have stripes or striations. Hence, they are also called the striated muscles.
● Cardiac muscle- found in the heart. Rhythmic contractions of this muscle help in the pumping blood.
3. Connective tissue
⮚ Connective tissue in animals, acts as a connecting medium, with some specialized functions.
⮚ The connective tissue is very complex and has a vital role to play.
⮚ They provide internal support as well as give and maintain form to the body.
⮚ It can be classified into three categories:
● Loose connective tissue
⮚ The areolar tissue and the adipose tissue are classified under the loose connective tissue. This tissue has cells and
fibers that are loosely arranged in the semifluid ground substance.
⮚ The areolar tissue is a loose connective tissue that can be seen between the skin and muscles; in the bone marrow
as well as around the blood vessels and nerves.

5. ● Dense connective tissue
⮚ Dense connective tissue is for strength.
⮚ The compact arrangement of collagen fibers serves to resist stretch.
⮚ Sheets of dense connective tissue cover muscles, separate neighboring muscle and also serve to give attachment to
muscle fibers.
⮚ The largest single mass of dense connective tissue is seen as the dermis (specifically, the reticular dermis) of the
skin. In some animal’s dermis is thick enough to be processed as leather.
● Specialized connective tissue
• 3 specialized connective are:
⮚ Blood: a fluid connective tissue. It consists of a liquid matrix called the plasma, in which blood cells are present.
⮚ Bones: the hard connective tissue. They give support and framework to the body. They protect the internal organs
and the muscle tissue attached to the bones helps in movement. The bone tissue is strong and non-flexible.
⮚ Cartilage: is another type of connective tissue that has a solid matrix. It contains proteins and sugars.

6. 4. Nervous tissue
⮚ The nervous tissue is a highly specialized tissue that is present in the animals. They help in transmitting
messages from the brain to various parts of the body and vice versa.
⮚ It is made of some specialized cells called neurons or nerve cells.
⮚ They can receive and transmit electrical impulses from different areas of the body to specific locations. The
nervous tissue cells are present in the brain, spinal cord, and the nerves.