Structural Organisation in Animals class 11 Neet

 

Structural Organisation in Animals class 11 Neet

What is Tissue ?

Tissue refers to a group or collection of similar cells that work together to perform a specific function in the body. Different types of tissues, such as epithelial, connective, muscle, and nervous tissue, make up the organs and structures of living organisms. They are the building blocks of organs and help in carrying out various physiological processes.

Animal Tissue ?

Animal tissue refers to the collection of specialized cells that make up the different structures and organs in animals. Animal tissues can be broadly classified into four main types: epithelial tissue, connective tissue, muscle tissue, and nervous tissue.

1. Epithelial tissue: This tissue covers the surfaces of the body, lines the cavities and tubes within the body, and forms the outer layer of organs. It serves as a protective barrier and can also be involved in secretion and absorption.

2. Connective tissue: Connective tissue provides support, structure, and protection to various organs and body parts. It includes a wide range of tissues, such as bone, cartilage, blood, adipose tissue (fat), and fibrous tissue.

3. Muscle tissue: Muscle tissue is responsible for movement. There are three types of muscle tissue: skeletal muscle (voluntary muscle responsible for body movements), smooth muscle (involuntary muscle found in organs and blood vessels), and cardiac muscle (specialized muscle found in the heart).

4. Nervous tissue: Nervous tissue forms the nervous system, which is responsible for transmitting and processing information throughout the body. It consists of neurons that carry electrical signals and neuroglial cells that support and protect the neurons.

These different types of animal tissues work together to maintain the structure and function of organs and systems within an animal's body.

Epithelial tissue ?

Epithelial tissue is a type of animal tissue that covers the surfaces of the body, lines body cavities and tubes, and forms the outer layer of organs. It is composed of closely packed cells that are tightly joined together, forming continuous sheets or layers.

Epithelial tissue serves various functions, including protection, absorption, secretion, and sensation. It acts as a barrier, protecting underlying tissues from injury, pathogens, and dehydration. Epithelial cells also play a role in absorbing nutrients and substances from the environment, as well as in the secretion of hormones, enzymes, mucus, and other substances.

There are different types of epithelial tissue based on their shape and arrangement of cells. These include simple epithelium (a single layer of cells), stratified epithelium (multiple layers of cells), and pseudostratified epithelium (appearing stratified but actually a single layer). Additionally, epithelial tissue can have various cell shapes, such as squamous (flat), cuboidal (cube-shaped), or columnar (column-shaped).

Epithelial tissue is found in many parts of the body, such as the skin, respiratory tract, digestive tract, urinary tract, and blood vessels. Its structure and function vary depending on its location and specific role in the body.

Type of Epithelial tissue ?

Epithelial tissue can be classified into several types based on the shape of the cells and the arrangement of cell layers. The main types of epithelial tissue are:

1. Simple squamous epithelium: This type of epithelium consists of a single layer of flat, scale-like cells. It is found in areas where efficient diffusion and filtration occur, such as the lining of blood vessels (endothelium) and the air sacs of the lungs (alveoli).

2. Simple cuboidal epithelium: It is made up of a single layer of cube-shaped cells. Simple cuboidal epithelium is found in various glands and in the lining of kidney tubules, where it performs functions like secretion, absorption, and excretion.

3. Simple columnar epithelium: This epithelium consists of a single layer of tall, column-shaped cells. It lines the digestive tract, including the stomach and intestines, where it helps with absorption and secretion. Simple columnar epithelium often has specialized structures like microvilli or cilia to increase its surface area or aid in movement.

4. Pseudostratified columnar epithelium: Although it appears stratified, this type of epithelium is actually a single layer of cells with varying heights. It is typically found in the respiratory tract, where it helps in the movement of mucus and the protection of underlying tissues.

5. Stratified squamous epithelium: It consists of multiple layers of flattened cells. Stratified squamous epithelium is present in areas that undergo mechanical stress or abrasion, such as the outer layer of the skin (epidermis) and the lining of the oral cavity and esophagus.

6. Transitional epithelium: This epithelium is specialized to accommodate stretching and changes in volume. It is found in organs like the urinary bladder, ureters, and urethra, which need to expand and contract.

These are some of the main types of epithelial tissue, each with its own structure and function, suited to the specific needs and environments of different organs and body regions.

Connective tissue is a type of animal tissue that provides support, structure, and connection between different tissues and organs in the body. It is characterized by an abundance of extracellular matrix, which is a complex mixture of proteins, fibers, and ground substance that fills the spaces between cells.

Connective tissue ?

Connective tissue has various functions, including providing structural support, maintaining shape and integrity of organs, transporting nutrients and waste products, defending against infection, and participating in wound healing.

There are several types of connective tissue, including:

1. Loose connective tissue: This type of connective tissue has loosely arranged fibers and cells suspended in a gel-like ground substance. It fills spaces around organs, supports blood vessels, and provides a cushioning effect.

2. Dense connective tissue: Dense connective tissue has densely packed collagen fibers that provide strength and support. It can be further classified into regular and irregular types. Regular dense connective tissue, found in tendons and ligaments, has collagen fibers aligned in a parallel manner to withstand forces in one direction. Irregular dense connective tissue, found in the dermis of the skin, has collagen fibers arranged in a random pattern, providing strength in multiple directions.

3. Adipose tissue: Adipose tissue, also known as fat tissue, is specialized for energy storage and insulation. It consists of adipocytes (fat cells) that store triglycerides, providing a source of energy and thermal regulation.

4. Cartilage: Cartilage is a firm and flexible connective tissue that provides support and cushioning between bones. It is found in areas such as the joints, nose, and ears. The most common types of cartilage are hyaline cartilage, elastic cartilage, and fibrocartilage.

5. Bone tissue: Bone tissue, or osseous tissue, is a hard and rigid connective tissue that forms the skeletal system. It provides support, protection, and aids in movement. Bone tissue is composed of osteocytes embedded in a matrix of collagen fibers and mineral salts, such as calcium and phosphorus.

6. Blood: Blood is a fluid connective tissue that circulates throughout the body, transporting oxygen, nutrients, hormones, and waste products. It consists of red blood cells, white blood cells, and platelets suspended in a liquid matrix called plasma.

Connective tissue is diverse in structure and function, contributing to the overall stability, movement, and protection of the body.

Muscle tissue?

Muscle tissue is a type of animal tissue that is specialized for contraction, resulting in movement and generating force. It is responsible for various types of movements, ranging from voluntary actions like walking and grasping to involuntary actions like heartbeat and digestion.

• There are three main types of muscle tissue in animals:

1. Skeletal muscle tissue: Skeletal muscle is attached to bones and allows voluntary movements of the body. It is composed of long, cylindrical cells called muscle fibers. Skeletal muscle is striated (having a striped appearance) due to the arrangement of contractile proteins within the fibers. It works in pairs or groups, with one muscle contracting while its counterpart relaxes to produce coordinated movements.

2. Smooth muscle tissue: Smooth muscle tissue is found in the walls of internal organs, blood vessels, and the respiratory and digestive tracts. It is responsible for involuntary movements, such as the contraction of blood vessels and peristalsis (wave-like contractions) in the digestive system. Smooth muscle cells are spindle-shaped and lack striations.

3. Cardiac muscle tissue: Cardiac muscle is exclusively found in the heart. It is responsible for the contraction and pumping of blood throughout the circulatory system. Cardiac muscle cells are striated like skeletal muscle but differ in their branching and interconnection. They are interconnected by specialized junctions called intercalated discs, allowing for coordinated contractions.

Muscle tissue is composed of contractile proteins, primarily actin and myosin, which slide past each other during contraction, resulting in muscle shortening and force generation. Nerve signals from the central nervous system control the contraction and relaxation of muscle fibers.

Muscle tissue plays a crucial role in maintaining posture, generating body heat, facilitating movement, and supporting vital functions in the body.

Neural tissue ?

Neural tissue, also known as nervous tissue, is a specialized type of animal tissue that forms the nervous system. It is responsible for transmitting and processing information throughout the body, enabling communication and coordination of various physiological processes.

Neural tissue is composed of two main types of cells:

Neurons: Neurons are the functional units of the nervous system. They receive, transmit, and process electrical signals, called nerve impulses or action potentials. Neurons have a cell body, which contains the nucleus and other cellular components, and extend long processes called dendrites and axons. Dendrites receive signals from other neurons or sensory receptors, while axons transmit signals to other neurons, muscles, or glands.

Neuroglial cells (glial cells): Neuroglial cells provide support, protection, and nourishment to neurons. They are non-neuronal cells that outnumber neurons in the nervous system. Glial cells have various functions, including insulating neurons, providing structural support, regulating the chemical environment around neurons, and assisting in repair and defense mechanisms.

Neural tissue forms the brain, spinal cord, and nerves throughout the body. It is responsible for sensory perception, motor control, coordination, memory, learning, and many other essential functions. Neurons communicate with each other and with other cells through specialized connections called synapses, where electrical signals are converted to chemical signals and vice versa.

The complexity and interconnectedness of neural tissue allow for the integration and processing of information, enabling the body to respond to stimuli, initiate movements, regulate internal processes, and maintain homeostasis.

Overall, neural tissue is critical for the functioning of the nervous system and plays a vital role in coordinating and controlling the body's activities.

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