Tissue Level of Organisation || B Pharmacy || 1st Semister ||

Tissue Level of Organisation

 

Classification of tissues:

 

Tissues are classified into four main types based on their structure, function, and location in the body:

 

1. Epithelial tissue: This tissue covers the body's surfaces, lines internal organs and cavities, and forms glands. It is further classified based on its shape (squamous, cuboidal, or columnar) and layering (simple or stratified).

 

2. Connective tissue: This tissue provides support and connects different tissues and organs in the body. It is further classified based on its structure (loose, dense, or specialized) and the type of extracellular matrix it contains (cartilage, bone, blood, or adipose).

 

3. Muscle tissue: This tissue is responsible for movement in the body, including skeletal, cardiac, and smooth muscle tissue. It is classified based on its structure (striated or smooth) and location in the body.

 

4. Nervous tissue: This tissue is responsible for transmitting and processing information in the body, including neurons and supporting cells called glia. It is classified based on its structure (central or peripheral) and the type of neurons it contains (sensory, motor, or interneurons).

 

Each of these tissue types has specific characteristics that make them suited for their unique roles in the body. Additionally, there are other specialized tissues such as glandular tissues, lymphoid tissue, and sensory receptors that are also classified based on their specific structures and functions.

 

Epithelial tissue:

 

Epithelial tissue is a type of tissue that covers the body's surfaces, lines internal organs and cavities, and forms glands. It is one of the four main types of tissues in the human body and is responsible for providing a protective barrier, absorbing nutrients, secreting hormones, and other functions.

 

Epithelial tissue is classified based on its shape and layering. The three main shapes of epithelial cells are squamous (flat and scale-like), cuboidal (cube-shaped), and columnar (tall and column-shaped). The layering of epithelial tissue can be either simple (one layer) or stratified (multiple layers).

 

Simple squamous epithelium is found in areas where diffusion and filtration occur, such as the lungs and blood vessels. Simple cuboidal epithelium is found in areas where secretion and absorption occur, such as in the kidneys and glands. Simple columnar epithelium is found in areas where absorption and secretion occur, such as in the digestive tract. Stratified squamous epithelium is found in areas that experience mechanical and chemical stress, such as the skin and mouth.

 

Epithelial tissue also includes specialized types such as pseudostratified columnar epithelium, transitional epithelium, and glandular epithelium. Pseudostratified columnar epithelium is found in the respiratory tract and appears to have multiple layers but all cells are connected to the basement membrane. Transitional epithelium is found in the bladder and is able to stretch and contract. Glandular epithelium forms glands, such as sweat and oil glands, and can be either simple or compound (with branching ducts).

 

Connective tissue:

Connective tissue is a type of tissue that provides support and connects different tissues and organs in the body. It is one of the four main types of tissues in the human body and is composed of cells, fibers, and an extracellular matrix.

 

Connective tissue is classified based on its structure and the type of extracellular matrix it contains. The three main types of connective tissue fibers are collagen (strong and flexible), elastic (stretchy), and reticular (thin and delicate).

 

 

The types of connective tissue include:

1. Loose connective tissue: This type of tissue is found in areas where support and protection are needed, such as around organs and under the skin.

 

2. Dense connective tissue: This type of tissue is composed of collagen fibers and provides strength and support to tendons, ligaments, and the dermis of the skin.

 

3. Cartilage: This type of tissue is found in joints, the nose, and ears, and provides cushioning and support.

 

4. Bone: This type of tissue is composed of calcium and provides support and protection to the body.

 

5. Blood: This type of tissue is composed of cells and plasma, and is responsible for carrying oxygen and nutrients throughout the body.

 

6. Adipose tissue: This type of tissue is composed of fat cells and provides insulation and energy storage.

 

In addition to these types of connective tissue, there are also specialized types such as lymphoid tissue, which plays a role in the immune system, and hematopoietic tissue, which produces blood cells.

 

Muscle tissue:

 

Muscle tissue is a type of tissue that is responsible for movement in the body. It is one of the four main types of tissues in the human body and is composed of muscle fibers or cells that are able to contract and generate force.

 

There are three types of muscle tissue:

 

1. Skeletal muscle tissue: This type of tissue is attached to bones and is responsible for voluntary movement such as walking, lifting weights, and running. It is striated in appearance due to its alternating dark and light bands under the microscope.

 

2. Cardiac muscle tissue: This type of tissue is found in the heart and is responsible for involuntary contractions that pump blood throughout the body. It is also striated in appearance but has a unique branching pattern of muscle fibers and is self-excitable, meaning it can initiate its own contractions.

 

3. Smooth muscle tissue: This type of tissue is found in the walls of organs and blood vessels and is responsible for involuntary contractions that move substances through the body, such as food through the digestive tract. It does not have a striated appearance and is controlled by the autonomic nervous system.

 

Muscle tissue can also be classified as slow-twitch or fast-twitch based on their contraction speed and endurance. Slow-twitch muscle fibers are better suited for endurance activities such as long-distance running, while fast-twitch muscle fibers are better suited for activities that require quick, explosive movements such as sprinting or weightlifting.

 

The structure of muscle tissue allows for contraction and relaxation in response to electrical impulses generated by the nervous system. The sliding filament theory describes the molecular mechanism of muscle contraction, in which actin and myosin filaments slide past each other to shorten the muscle fiber and generate force.

 

 

 

 

Nervous tissue:

 

Nervous tissue is a type of tissue that is responsible for communication and coordination in the body. It is one of the four main types of tissues in the human body and is composed of neurons and supporting cells such as glial cells.

 

Neurons are specialized cells that transmit electrical and chemical signals throughout the body. They have a cell body, dendrites that receive signals from other neurons or sensory receptors, and an axon that transmits signals to other neurons, muscles, or glands.

 

Glial cells are supporting cells that surround and protect neurons. They play a role in providing nutrients and support, as well as insulating and protecting neurons.

 

Nervous tissue is organized into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord, while the PNS includes the nerves that connect the CNS to the rest of the body.

 

The function of nervous tissue is to receive and process sensory information, integrate it with existing knowledge, and generate an appropriate response. This includes sensory processing, motor control, and higher cognitive functions such as memory, learning, and emotions.

 

Disorders of nervous tissue can result in a range of neurological and psychiatric conditions, such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, and depression.

 

Structure of tissues:

The structure of tissues can vary depending on their type and function. However, all tissues are composed of cells, extracellular matrix, and intercellular junctions.

 

1. Cells: The cells in a tissue are specialized and perform specific functions. For example, epithelial cells line the surfaces of the body and organs and protect them from damage, while muscle cells contract and generate force. Connective tissue cells produce and maintain the extracellular matrix, and nerve cells transmit electrical and chemical signals.

 

2. Extracellular matrix (ECM): The ECM is a complex mixture of proteins, carbohydrates, and other molecules that surround and support the cells in a tissue. It provides mechanical strength and elasticity, as well as regulating cell behavior such as adhesion, migration, and differentiation. The composition and organization of the ECM can vary widely depending on the tissue type.

 

3. Intercellular junctions: These are specialized structures that connect adjacent cells in a tissue and allow for communication and coordination. Examples of intercellular junctions include tight junctions, which seal the gaps between cells and prevent the movement of molecules between them, and gap junctions, which allow for the exchange of ions and small molecules between cells.

 

In addition to these basic components, tissues can also contain blood vessels, lymphatic vessels, and nerves that provide oxygen, nutrients, and signaling molecules to the cells within the tissue.

 

The specific organization and structure of tissues can be observed using different techniques such as microscopy, histology, and imaging. Understanding the structure of tissues is important in the diagnosis and treatment of diseases and disorders that affect different organs and tissues in the body.

 

Location and functions of epithelial:

 

Functions of epithelial:

 

 

Epithelial tissue is found throughout the body, lining the surfaces of organs, cavities, and structures. It has a variety of functions depending on its location and type.

 

1. Protection: Epithelial tissue forms a barrier that protects underlying tissues and organs from physical damage, infection, and harmful substances. For example, the stratified squamous epithelium that lines the skin and mucous membranes prevents the entry of pathogens and other harmful agents.

 

2. Absorption and secretion: Epithelial tissue can absorb and secrete substances such as nutrients, gases, hormones, and waste products. For example, the simple columnar epithelium lining the small intestine absorbs nutrients from digested food and secretes digestive enzymes and mucus.

 

3. Sensory reception: Epithelial tissue can contain specialized cells that detect changes in the environment and transmit signals to other cells in the body. For example, the olfactory epithelium in the nasal cavity contains sensory cells that detect different odors.

 

4. Transportation: Epithelial tissue can facilitate the movement of substances between different parts of the body. For example, the ciliated epithelium lining the respiratory tract moves mucus and trapped particles out of the lungs.

 

5. Secretion of lubricants: Epithelial tissue can also secrete lubricating fluids that reduce friction and irritation. For example, the serous membranes lining the cavities of the body produce a lubricating fluid that reduces friction between organs.

 

The specific functions of epithelial tissue can vary depending on its location and type. For example, the stratified squamous epithelium in the skin protects against mechanical damage and infection, while the simple squamous epithelium lining blood vessels allows for the exchange of gases and nutrients between the bloodstream and surrounding tissues.

 

 

Location of epithelial:

 

Epithelial tissue is found throughout the body, lining the surfaces of organs, cavities, and structures. Here are some examples of the location of epithelial tissue in the body:

 

1. Skin: The outer layer of the skin is composed of stratified squamous epithelium, which provides protection against physical damage, infection, and dehydration.

 

2. Digestive system: The lining of the mouth, esophagus, stomach, small intestine, and large intestine is composed of different types of epithelial tissue. The epithelial cells in the digestive system absorb nutrients from food and secrete digestive enzymes and mucus.

 

3. Respiratory system: The lining of the nasal cavity, trachea, and bronchi is composed of ciliated epithelium, which helps to move mucus and trapped particles out of the lungs.

 

4. Urinary system: The lining of the bladder, ureters, and urethra is composed of transitional epithelium, which allows for expansion and contraction of these structures.

 

5. Reproductive system: The lining of the uterus, fallopian tubes, and vagina in females is composed of various types of epithelial tissue. The epithelial cells in the reproductive system secrete mucus and other substances that help to protect and nourish the developing embryo.

 

6. Endocrine system: The epithelial cells in the endocrine glands secrete hormones that regulate various functions in the body, such as growth and metabolism.

 

The specific location and type of epithelial tissue can vary depending on its function and location in the body.

 

Muscular Tissue:

 

Muscular tissue is a type of tissue that is specialized for contraction and generating force. There are three types of muscular tissue in the body:

 

1. Skeletal muscle: This type of muscle tissue is attached to bones and is responsible for movement of the body. Skeletal muscle cells are long and cylindrical, and they have multiple nuclei. They are striated, which means they have a banded appearance under the microscope, and they are under voluntary control.

 

2. Smooth muscle: This type of muscle tissue is found in the walls of hollow organs such as the intestines, uterus, and blood vessels. Smooth muscle cells are spindle-shaped and have a single nucleus. They are not striated and are under involuntary control.

 

3. Cardiac muscle: This type of muscle tissue is found in the heart and is responsible for pumping blood throughout the body. Cardiac muscle cells are short and branched, and they have a single nucleus. They are striated, like skeletal muscle, but they are under involuntary control.

 

Muscular tissue functions to create movement and maintain posture, generate heat, and circulate blood and other fluids throughout the body. Skeletal muscle is the primary type of muscle tissue responsible for movement, while smooth muscle and cardiac muscle are responsible for regulating the diameter of blood vessels, movement of food through the digestive tract, and contraction of the heart, respectively.

 

 

The structure and function of muscular tissue can be affected by various diseases and disorders, such as muscular dystrophy, myasthenia gravis, and heart failure. Treatment options for these conditions may include medications, physical therapy, or surgery.

 

nervous Tissue:

 

Nervous tissue is a specialized type of tissue that is responsible for transmitting and processing nerve impulses throughout the body. It is composed of two main types of cells: neurons and glial cells.

 

1. Neurons: These are the cells that transmit nerve impulses. Neurons have a cell body, dendrites, and an axon. The dendrites receive signals from other neurons or from sensory receptors, while the axon transmits signals to other neurons or to muscles or glands. Neurons communicate with each other at specialized junctions called synapses.

 

2. Glial cells: These are non-neuronal cells that provide support and protection for neurons. Glial cells include astrocytes, oligodendrocytes, and microglia, among others. They provide structural support for neurons, regulate the chemical environment of the brain and spinal cord, and help to repair damage to nervous tissue.

 

Nervous tissue is found throughout the body, but it is most concentrated in the brain and spinal cord, which make up the central nervous system (CNS). The nervous tissue in the CNS is responsible for processing and integrating information from the senses, controlling movement, and regulating organ function. Peripheral nervous system (PNS) contains nervous tissue located outside the CNS, which is responsible for transmitting signals to and from the CNS and the rest of the body.

 

The structure and function of nervous tissue can be affected by various diseases and disorders, such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, and epilepsy. Treatment options for these conditions may include medications, surgery, or other therapies that target the nervous system.

 

Connective Tissue:

 

Connective tissue is a type of tissue that provides support and structure to the body. It is made up of cells, fibers, and extracellular matrix, which is a substance secreted by the cells that provides a framework for the tissue.

 

There are several types of connective tissue in the body:

 

1. Loose connective tissue: This type of tissue is found throughout the body, and it provides support and flexibility to organs and tissues. It contains collagen and elastin fibers, which give it strength and elasticity.

 

2. Dense connective tissue: This type of tissue is found in tendons, ligaments, and other structures that require high tensile strength. It contains tightly packed collagen fibers that run in parallel to each other.

 

3. Cartilage: This is a flexible, rubbery tissue that provides cushioning and support to joints, such as the knee and hip. It contains collagen and proteoglycans, which give it its unique properties.

 

4. Bone: This is a hard, mineralized tissue that provides support and protection to the body. It contains collagen and calcium phosphate, which give it its strength and rigidity.

 

5. Blood: This is a specialized connective tissue that is responsible for transporting oxygen, nutrients, and other substances throughout the body. It is made up of red and white blood cells, as well as plasma, which is the liquid component of blood.

 

Connective tissue performs several functions in the body, including support and protection of organs, maintenance of tissue structure, and storage of energy. The structure and function of connective tissue can be affected by various diseases and disorders, such as osteoporosis, arthritis, and scurvy. Treatment options for these conditions may include medications, physical therapy, or surgery.