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The secrets of organization: How do cells weave themselves into powerful teams?
In biology, a tissue is a collection of cells with similar functions and their extracellular matrix, which originate from the same embryonic tissue and can work together to perform a specific function. This structural level is between cells and complete organs, which are the result of the integration of multiple tissue functions.
Organisms follow this hierarchy: cell < tissue < organ < organ system < organism.
The word "tissue" comes from the French word "tissu", which means "to weave". Histology is the study of these tissues, while pathological histology focuses on changes in tissues associated with disease.
Plant tissue
Plant tissues are divided into three systems: epidermal tissue, basic tissue and vascular tissue.
- Epidermis: Cells that form the outer surface layer of a plant.
- Vascular tissue: Mainly composed of xylem and phloem, responsible for internal fluid and nutrient transport.
- Basic tissue: Relatively undifferentiated, responsible for photosynthesis and nutrient storage.
Meristem
Meristems are made up of cells that continually divide, causing the plant to increase in length and thickness. They are mainly found in the roots and stem tips of plants.
In these cells, dense cytoplasm and prominent nuclei give meristem cells a unique shape and function.
Permanent Organization
Permanent tissues are formed by meristems, cells that lose the ability to divide again and become fixed within the plant. They can be divided into simple permanent tissues and compound permanent tissues.
Simple Permanent Organization
Simple permanent tissues are cells with similar morphology and function, mainly including the following three types:
- Parenchyma
- Collenchyma
- Hard tissue (Sclerenchyma)
Compound permanent tissue
This type of tissue is made up of many types of cells and includes the xylem and phloem, and is primarily responsible for nutrient and water transport in plants.
Animal Tissue
Animal tissues can generally be divided into four categories: connective tissue, muscle tissue, nervous tissue and epithelial tissue. Collections of these tissues contribute to the formation of organs and enable different parts of the body to work together.
Epithelial tissueIn all animals, the origin of all tissues can be traced back to the germ layers, with epithelial tissue arising from the ectoderm and endoderm, and connective tissue and muscle tissue arising from the mesoderm.
Epithelial tissue is distributed throughout the surface of organs and is responsible for functions such as protection, secretion and absorption. Its characteristic is that the cells are tightly connected, forming a selectively permeable barrier.
Connective tissue
Connective tissue is characterized by its composition of cells and inactive matrix, which is responsible for supporting and connecting organs and their structures. For example, blood and bones are examples of connective tissue.
Muscle tissue
Muscle tissue is the contractile tissue in the body that is responsible for causing movement. It is mainly divided into three types: smooth muscle, skeletal muscle and cardiac muscle.
Nervous tissue
Nervous tissue is composed of cells of the central nervous system and peripheral nervous system, and is responsible for the transmission and response of signals.
ConclusionThe organization of cells provides the structural and functional basis for the operation of organisms. How does their cooperation affect their respective life functions?
