How Many Types of Tissues are Found in Animals

Introduction

Animal tissues can be divided into four categories: Epithelial, Connective, Muscular, and Nervous tissues. Let us see how animal tissues differ from one another and how each tissue's structure and function interacts.

Epithelial Tissue

Most organs are covered by or lined with epithelial tissue. The exchange of materials between different organs is greatly facilitated by the epithelial tissue's permeability. It is crucial for osmoregulation as well.

Four types of epithelial tissues exist:

1. The simple epithelium consists of a single layer of cells.

2. For instance, the alveoli and blood vessel lining.

3. Cuboidal epithelium has cells that have the shape of cubes.

4. Salivary gland ducts and kidney tubule lining.

5. Offer mechanical assistance.

6. Function as secretors and go by the name glandular epithelium.

7. The columnar epithelium has cells that are formed like columns.

8. Promotes absorption and secretion.

9. For instance, the intestinal lining

10. Columnar epithelium in several organs possesses cilia on the outer surface.

The mucus is propelled forward by the ciliated epithelium of the respiratory system.

1. The stratified epithelium's cells are arranged in numerous layers.

2. A stratified epithelium is an example of the skin.

3. Stratification layers stop deterioration.

Along with connective tissue, muscular tissue, and nerve tissue, the epithelium is one of the four fundamental forms of animal tissue. It is made up of a thin, continuous layer of tightly packed cells and a minimal intercellular matrix. The body's external organs and blood vessels, as well as the interior surfaces of many internal organ chambers, are all lined with epithelial tissues. The epidermis, the skin's top layer, serves as an illustration.

The three main types of epithelial cells are cuboidal, columnar, and squamous (scaly). These can be organised in layers of two or more cells deep as stratified (layered), or compound, either squamous, columnar, or cuboidal, or in a single layer of cells as simple epithelium, either squamous, columnar, cuboidal, or square. Due to the positioning of the nuclei, a layer of columnar cells in some tissues may appear to be stratified.

Pseudostratified tissue is this kind of tissue. Epithelial cells make up every gland. Diffusion, filtration, secretion, selective absorption, germination, and transcellular transport are among the tasks performed by epithelial cells. The compound epithelium serves as a barrier. Since epithelial layers lack blood vessels (are avascular), they must be nourished by substances diffusing through the basement membrane from the connective tissue beneath. Particularly many cell junctions can be found in epithelial tissues

Muscular Tissue

Muscle cells make up muscular tissue. Specialised cells like muscle cells can contract and expand. Muscle contraction and expansion allow the body to move in a variety of ways. There are three types of muscular tissues: The many types of muscles in most animals are made up of muscle tissue, which gives the muscles their capacity to contract. The process of myogenesis, which forms muscle tissue throughout embryonic development, is known. Actin and myosin, two unique contractile proteins found in muscle tissue, contract and relax to move. Two regulatory proteins, troponin and tropomyosin, are among the numerous additional muscle proteins that are present.

The placement and use of a muscle's tissue will affect that tissue's appearance. Skeletal or striated muscle tissue, smooth muscle (non-striated muscle), and cardiac muscle are the three types found in animals. Skeletal muscle tissue, which is made up of elongated muscle cells known as muscle fibres, is what moves the body. Tendons and other tissues can be found in the skeletal muscle, Perimysium. Without conscious effort, the smooth and cardiac muscles contract.

These muscle groups might be stimulated by the interaction of the central nervous system, peripheral plexus innervation, or endocrine (hormonal) stimulation. Skeletal or strained muscle only freely contracts under the control of the central nervous system. Although they include the nonconscious activation of skeletal muscles, reflexes nonetheless involve the central nervous system, even though the cortical structures are not activated until after the contraction has taken place.

1) Striated Muscles: Striated muscles have long, unbranched fibres that make up their cells.

2) Smooth Muscles: The spindle-shaped cells of smooth muscles have one nucleus apiece.

Cardiac Muscles: These muscles have branched fibre-like cells as their constituent parts.

Connective Tissue

In a matrix, connective tissue cells are haphazardly dispersed. The matrix may be jelly-like, stiff, thick, or fluid. The numerous connective tissues are listed below:

(a) Connective tissue in the areola:

(i) Found in bone marrow, around blood arteries and nerves, and between skin and muscles.

(ii) Provides support and fills the space between tissues.

(iii) It also aids in tissue restoration.

(b) Adipose tissue

(i) Fat globules make up adipose tissue.

(ii) Found beneath the organs and the skin.

(iii) Serves as a cushion and a source of insulation.

(c) Fibrous tissue

(i) There are few cells or matrix components and plenty of collagen fibres.

(ii) The strands of the fibres can be lined up in parallel or organised randomly.

(iii) Areas of the body under constant stress, like the dermis of the skin, have irregularly distributed fibrous connective tissues.

(d) Cartilage

(i) Both the matrix and the fibres are present in significant concentrations.

(ii) The tissue's matrix and fibres are made by the cells, known as chondrocytes.

(iii) Chondrocytes are located in lacunae, which are voids in the tissue.

(iv) Routine histological stains give the tissue's matrix a milky or washed look, and the lacunae are dispersed at random throughout the tissue.

(e) Bone

(i) Osteoblasts make up the majority of bone tissue.

(ii) The skeletal system is made of bone.

(iii) In charge of giving the body its structural framework..

(f) Blood

(i) Blood is made up of platelets, plasma, and blood cells.

(ii) Has a crucial role in the movement of different substances throughout the body.

(iii) Aids in osmoregulation and temperature regulation as well.

(g) Lymph

(i) Lymphocytes play a key role in the immune system's reaction to invading antigens or substances.

(ii) Different types of lymphocytes produce antibodies that are specifically adapted to foreign antigens and regulate their synthesis.

Connective tissue fills the gaps between various tissues all over the body, including the nervous system. Connective tissue makes up the three meninges, which are membranes that surround the brain and spinal cord. Three basic elements typically make up connective tissue: cells, ground material, and elastic and collagen fibres. Specialised fluid connective tissues without fibres include blood and lymph. Everyone is submerged in the water. Fibroblasts, adipocytes, macrophages, mast cells, and leukocytes are some of the cells that make up connective tissue.

Johannes Peter Müller coined the phrase "connective tissue" (in German, Bindegewebe) in 1830. The 18th century saw the recognition of tissue as a separate class. Loose connective tissue and dense connective tissue make up the connective tissue in its right form (which is further subdivided into dense regular and dense irregular connective tissues.) [8] The proportion of ground substance to fibrous tissue distinguishes between loose and thick connective tissue.

In contrast to dense connective tissue, loose connective tissue contains a greater amount of ground substance and a lesser amount of fibrous tissue. Collagen fibres are arranged in an orderly parallel pattern in dense regular connective tissue, which is present in tissues like tendons and ligaments and gives it tensile strength in one direction. Due to its dense bundles of fibres arranged in all directions, dense irregular connective tissue provides strength in multiple directions.

Nervous Tissue

The embryonic ectoderm, the layer that covers the embryo and later gives rise to the epidermis, is the source of nerve tissue. Neurons and glia are the two cell types that make up the nervous system. The primary job of the nervous system is to process information from both the internal and external environments before evoking a reaction. Numerous other essential bodily processes, including respiration, digestion, cardiac blood pumping, blood flow management, endocrine system control, and many others are also under its control.

Most of these operations rely on the electrical characteristics of nerve cells. Electrical potentials that spread through the plasma membranes of the neurons serve as the stimuli's translation into their language. Similarly to this, the nervous system communicates with many body organs, particularly the muscle cells.

The nervous system is made of specialised cells called neurons found in nervous tissue. There are two separate sections to a neuron, called the head and tail. The nucleus and some other cell components are located in the head, which has a star-like form. It is known as cyton. The cyton has many outgrowths that resemble hair. Dendrites are what these are. Axon terminals are where the tail ends. Axons transmit nerve signals, while dendrites receive nerve impulses.

The cell bodies of neurons and glia, as well as their cell processes, make up the majority of the nervous system. A nervous system region with many cell processes is called neuropil. Additionally, a sparse extracellular matrix that is rich in glycoproteins is present. The extracellular matrix plays a role in a variety of processes, including synaptic development and movement, axonal growth, pathfinding, and cell movement. The peripheral nervous system, which includes nerve ganglia, nerves, and neurons dispersed throughout the body, as well as the central nervous system, which includes the brain and spinal cord, are both made up of nervous tissue. The central nervous system has regions that are densely populated with both glial and neuronal cell bodies.

These regions are referred to as grey matter because they appear greyish in fresh tissue. Other components of the central nervous system are primarily composed of cell processes and have few cell bodies (mainly myelinic axons). These regions are referred to as white matter because they are whitish in young nerve tissue. The larger axonal tracts are found in white matter. Grey matter is typically found superficially in the encephalon (brain), whereas it is deeper in the spinal cord. Typically, neurons are linked together in functional layers, such as the cerebral cortex.

Summary

Four fundamental tissues serve as the basic building blocks of complex animals. These are united to create organs, such as the skin and kidney, each of which has a distinct, specialised purpose within the body. Systems are created by grouping organs together to carry out shared tasks. Epithelium, connective tissues, muscle tissues, and nerve tissues make up the four main tissue types.