Tissue Definition

Tissues are groups of cells that have a similar structure and act together to perform a specific function. The word tissue comes from a form of an old French verb meaning “to weave”.

Types of Tissues in Animals

The tissues in animals are classified in four categories

Connective tissue

Connects or separates groups of other tissues. It is found in between all the other tissues and organs in the body. Connective tissue is made up of cells and ground substance, which is a gel that surrounds cells. Most connective tissue, except for lymph and blood, also contains fibers, which are long, narrow proteins. Fibers can be collagenous, which bind bones to tissues; elastic, which allow organs like the lungs to move; or reticular, which provide physical support to cells. Connective tissue also allows oxygen to diffuse from blood vessels into cells.

About 1 in 10 people have a disorder involving connective tissue. Some connective tissue disorders include sarcomas, Marfan syndrome, lupus, and scurvy, which is a Vitamin C deficiency that leads to fragile connective tissue.

in short connective tissue performs:

  • Binding
  • Supporting
  • Protecting
  • Forming Blood
  • Storing Fats
  • Filling Space

Types of Connective Tissues

  1. Supporting Connective Tissue
  2. Dense Connective Tissue
  3. Loose Connective Tissue
  4. Adipose Tissue

Muscle Tissue

Muscle tissue contains numerous microfilaments composed of actin and myosin, which are contractile proteins. Muscle tissue contracts in response to stimulation. It cannot lengthen by itself but is lengthened by the contraction of other muscles.Muscle tissue is used for locomotion, food movement in gut, and heat production.

Types of Muscle Tissue

There are three types of muscle tissue

Skeletal muscle: Skeletal muscle anchors tendons to bones and allows the body to move.

Cardiac muscle: Cardiac muscle is found in the heart and contracts to pump blood. 

Smooth muscle:  Smooth muscle is found in the intestines, where it helps move food through the digestive tract, and it is also found in other organs like blood vessels, the uterus, and the bladder.

Skeletal and cardiac muscles are striated; this means that they contain sarcomeres (a unit of muscle tissue) that are arranged in a uniform pattern. Smooth muscle does not have sarcomeres.

Epithelial Tissue

Epithelial tissue covers external surfaces and internal cavities and organs. Glands are also composed of epithelial tissue. Epithelial tissue helps to protect organisms from microorganisms, injury, and fluid loss. Absorption is an importan function of epithelial tissue, Glandular epithelium secretes chemicals.

Types of Epithelial Tissue:

Epithelia are commonly classified based on the shape of the cells on the free surface, as well as the number of cell layers. Sample types include:

Simple Epithelium: A simple epithelium has a single layer of cells. 

Stratified Epithelium: A stratified epithelium has multiple layers of cells.

On the basis of shape epithelial tissues are following types

  • Columnar 
  • Cuboidal
  • Squamous

Nervous Tissue

Nervous tissue is the fourth basic tissue type of the body and is organized into two basic systems

  1. The Central Nervous System (CNS) and
  2. The Peripheral Nervous System (PNS).

The peripheral system responds to stimuli and sends impulses to the central system (brain and spinal cord). These impulses are interpreted by the CNS and then other impulses initiated in the CNS travel back through the PNS to effector organs to produce the proper response.

The basic cell of the nervous system is called a neuron. Structurally, a neuron consists of:

  1. The cell body, containing the nucleus and synthetic organelles
  2. The axon, a long cytoplasmic process associated with the cell body used to communicate with target organs; and 
  3. The dendrites, shorter cytoplasmic processes off the cell body used to communicate between neurons.
 
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