Animal tissues

Muscular tissue

Muscular tissue consists of elongated cells called muscle fibres. This tissue is responsible for movement in our body. Muscle contain special proteins called contractile proteins, which contract and relax to cause movement.

Unstriated muscles

The cells are long with pointed ends (spindle-shaped) and uninucleate having a single nucleus. They are also called unstraited muscles.

Skeletal or Striated muscles

Under the microscope, these muscles show alternate light and dark bands or striations when stained appropriately. As a result, they are also called striated muscles.

Voluntary muscles

Voluntary muscles: Muscles present in our limbs move when we want to, and stop when we so decide. Such muscles are called voluntary muscles.

Connective tissue

Blood is a type of connective tissue. The cells of connective tissue are loosely spaced and embedded in an inter-cellular matrix. The matrix may be a jelly like, fluid, dense or rigid. The nature of matrix differs in concordance with the function of the particular connective tissue. Blood has a fluid matrix called plasma, in which red blood cells, white blood cells and platelets are suspended. The plasma contains proteins, salts and hormones. Example: Bone is a connective tissue, it forms the framework that supports the body. Example: Cartilage is another type of connective tissue which has widely spaced cells. Example: Areolar connective tissue is found between the skin and muscles, around blood vessels and nerves and in the bone marrow.

Glandular epithelium

Sometimes a portion of the epithelial tissue folds inward, and a multicellular gland is formed. This is glandular epithelium.

Nervous Tissue

All cells possess the ability to respond to stimuli. Cells of the nervous tissue are highly specialized for being stimulated and then transmitting the stimulus very rapidly from one place to another within the body. The brain, spinal cord and nerves are all composed of the nervous tissue. The cells of this tissue are called nerve cells or neurons. Neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair-like parts arise. Each neuron has a single long part, called the axon, and many short, branched parts called dendrites. An individual nerve cell may be up to metre long. Many nerve fibres bound together by connective tissue makeup a nerve. Nerve impulses allow us to move our muscles when we want to. The functional combination of nerve and muscle tissue is fundamental to most animals.

Cuboidal epithelium

Cuboidal epithelium forms the lining of kidney tubules and ducts of salivary glands, where it provides mechanical support. Epithelial cells often acquire additional specialization as gland cells, which can secrete substances at the epithelial surface.

Different Epithelia

Different epithelia show differing structures that correlate with their unique functions. Example: In cells lining blood vessels or lung alveoli, where transportation of substances occurs through a selectively permeable surface, there is a simple flat kind of epithelium. This is called the simple squamous epithelium. Simple squamous epithelial cells are extremely thin and flat.and form a delicate lining. The oesophagus and the lining of the mouth are also covered with squamous epithelium.

Epithelial Tissue

The covering or protective tissues in the animal body are epithelial tissues. Epithelium covers most organs and cavities within the body. It also forms a barrier to keep different body systems separate. examples: Skin, the lining of the mouth, the lining of blood vessels,lung alveoli and kidney tubules are all made of epithelial tissue. Epithelial tissue cells are tightly packed and form a continuous sheet. They have only a small amount of cementing material between them and almost no intercellular spaces. Any thing entering or leaving the body must cross at least one layer of epithelium. As a result, the permeability of the cells of various epithelia play an important role in regulating the exchange of materials between the body and external environment and also between different parts of the body. Regardless of the type, all epithelium is usually separated from the underlying tissue by an extracellular fibrous basement membrane.

Cardiac muscles

The muscle of the heart show rhythmic contraction and relaxation throughout life. These involuntary muscles are called cardiac muscles. Heart muscle cells are cylindrical, branched and uninucleate.

Stratified squamous epithelium

The skin, which protects the body, is also made of squamous epithelium. The skin epithelial cells are arranged in many layers to prevent wear and tear. Since they are arranged in pattern of layers, the epithelium is called stratified squamous epithelium.

Ciliated columnar epithelium

Where absorption and secretion occur, as in the inner lining of the intestine, tall epithelial cells are present. This columnar epithelium facilitates movement across the epithelial barrier. In the respiratory tract, the columnar epithelial tissue also has cilia, which are hair-like on the outer projections on the outer surfaces of epithelial cells. These cilia can move, and their movement pushes the mucus forward to clear it. This type of epithelium is thus ciliated columnar epithelium.

Smooth muscles or involuntary muscles

the movement of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary movements. We cannot really start them or stop them simply by wanting to do so. Smooth muscles or involuntary muscles control such movements. Example: They are found in the iris of the eye, in ureters and in the bronchi of the lungs.