Lesson 6: Tissues PDF

Lesson 6: Tissues Tissues group of similar cells combines together to perform a similar function These are cluster of cells (specialized cells) which functions uniquely. Found only on multicellular organisms Study of tissue: histology; disease re-related to tissue: histopathology There are 2...

Lesson 6: Tissues Tissues group of similar cells combines together to perform a similar function These are cluster of cells (specialized cells) which functions uniquely. Found only on multicellular organisms Study of tissue: histology; disease re-related to tissue: histopathology There are 2 types of tissues in multicellular organisms: Animal tissues Plant tissues Animal Tissues Animal tissue vary in their structure, function, and the origin. It provides medium for material exchange between cells and vascular supply underneath. Animal tissue were classified into: Epithelial tissue muscular tissue Connective tissue Nervous tissue Plant Tissues These are the tissues which help in providing the elasticity and flexibility to the plants organs Tissues made up of dead cells provide structural strength Two types of Plant Tissues: Permanent Tissue Meristematic tissue Permanent Tissues Permanent tissues are formed by the division of the meristematic tissue cells which have lost their ability to multiply. Types of Permanent Tissues: Simple permanent tissue Complex permanent tissue Simple Permanent Tissue Helps in storage of food and gives mechanical support to plants Made up of only one type of cells Also known as the ground tissues Simple Permanent tissue is classified into three: Parenchyma tissue Collenchyma tissue Sclerenchyma tissue Complex Permanent Tissue Made up of more than one type of cells Helps in transportation of water, sugars, minerals and other metabolites all over the plant. Vascular/conducting tissues Two types of complex permanent tissue: Xylem Phloem Protective tissues Protective tissues: Epidermis: It is the outer covering of cells in plants. It carries out protective function (protecting plants from some unfavorable conditions). It is generally made up of a single layer of cells. In arid habitats, the epidermis is thicker to protect the plant from undue loss of water. Cork: As plants grow big, a strip of secondary meristem known as cork cambium replaces the epidermis of the stem. It is a plain tissue with only one type of cell. The cork cambium gives off fresh cells on both sides, forming cork. These cells are lifeless with no intercellular spaces and are greatly thickened with suberin. Cork cells avert desiccation, infection, and mechanical injury. Meristematic Tissues A plant tissue that has the ability to divide actively throughout its life. Tissues that has small vacuoles and single, large and central nucleus. These tissues have high metabolic activities. Three categories of meristematic tissues: Apical Meristems – These meristems are located on the tip of the root, stem etc. They help in the growth of the root system as well as the shoot system. The various cell divisions along with the cellular enlargement help in the growth of the stem above the ground and the growth of the root below the ground. Intercalary Meristems – The intercalary meristems are located at the internodes or the base of the leaves. The intercalary meristems help in increasing the length of the internode. This is usually seen in monocotyledonous plants. Lateral Meristems – The lateral meristems are present on the lateral side of the stem and root of a plant. These meristems help in increasing the thickness of the plants. The vascular cambium and the cork cambium are good examples of a lateral meristematic tissue.