#biology #tissue #organs #organsystems #organism

Pg:- 35,36,37 Textbook

Ch:- 2

Tissues:

Definition: Tissues are groups of similar cells that work together to perform a specific function. They are the building blocks of organs and provide structural and functional support.

Types of Tissues:

1. Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands. It serves as a protective barrier, involved in absorption, secretion, and filtration. Examples include skin, the lining of the intestines, and glands.

2. Connective Tissue: Supports, binds, and protects other tissues and organs. It includes a variety of structures such as bones, tendons, blood, and fat. This tissue type provides structural support, stores energy, and helps in immune responses.

3. Muscle Tissue: Responsible for movement. It can contract and relax, allowing voluntary movement (like skeletal muscles) and involuntary movement (like cardiac and smooth muscles). Examples include heart muscles and muscles in the digestive tract.

4. Nervous Tissue: Composed of neurons and supporting cells, nervous tissue is responsible for transmitting electrical signals throughout the body. It enables communication between different body parts and controls bodily functions. Found in the brain, spinal cord, and nerves.

Organs:

Definition: An organ is a structure composed of two or more types of tissues that work together to perform specific, complex functions. Each organ has a unique role in the body.

Examples of Organs:

• Heart: Made up of cardiac muscle tissue, connective tissue, and epithelial tissue, the heart pumps blood throughout the body, supplying oxygen and nutrients to cells.

• Lungs: Comprising epithelial tissue and connective tissue, the lungs facilitate the exchange of oxygen and carbon dioxide between the blood and the air.

• Stomach: Contains muscle tissue for churning food, epithelial tissue for lining, and connective tissue to support the structure; it helps in digesting food.

Organ systems:

Definition: Organ systems are groups of organs that work together to perform major functions or meet physiological needs of the body. Each system is specialized for a specific set of tasks and relies on coordinated organ interactions.

Major Organ Systems:

1. Circulatory System: Includes the heart, blood vessels, and blood. It transports nutrients, gases, and wastes throughout the body.

2. Respiratory System: Composed of the lungs, trachea, and nasal passages. It facilitates breathing, allowing oxygen intake and carbon dioxide expulsion.

3. Digestive System: Includes the mouth, esophagus, stomach, intestines, and liver. It breaks down food, absorbs nutrients, and eliminates waste.

4. Nervous System: Composed of the brain, spinal cord, and nerves. It controls body activities through nerve signals and maintains homeostasis.

5. Skeletal System: Includes bones, joints, and cartilage. It provides structural support, protects organs, and facilitates movement.

6. Muscular System: Composed of skeletal muscles, cardiac muscles, and smooth muscles. It enables movement, posture, and heat production.

7. Endocrine System: Consists of glands that produce hormones, regulating growth, metabolism, and reproductive processes.

8. Immune System: Composed of white blood cells, lymph nodes, and spleen. It defends the body against infections and diseases.

9. Reproductive System: Includes organs like the ovaries, testes, and associated structures. It is responsible for producing gametes and enabling reproduction.

10. Integumentary System: Composed of the skin, hair, and nails. It protects the body, regulates temperature, and senses the external environment.

11. Excretory System: Includes kidneys, bladder, and urethra. It removes waste products from the body and maintains water and salt balance.

The organism:

Definition: An organism is a complete living entity that represents the highest level of organization. It can be a single-celled organism, like bacteria, or a complex multicellular organism, like humans.

• Integration of Systems: In a multicellular organism, all organ systems work in harmony to maintain life. For example, the circulatory and respiratory systems work together to deliver oxygen to tissues, while the nervous and endocrine systems regulate body functions.

• Homeostasis: The organism strives to maintain internal balance (homeostasis) despite external changes. This dynamic equilibrium is crucial for survival and involves complex feedback mechanisms.

Summary of Hierarchical Organization:

1. Tissues: Groups of similar cells performing a function.

2. Organs: Structures composed of tissues working together.

3. Organ Systems: Groups of organs coordinating to perform bodily functions.

4. Organism: The complete living being with all systems working together.