Glossary: Structural Organisation in Animals | Biology for Grade 11 PDF Download

Animal Tissues

• Tissue: In multicellular animals, a group of similar cells alongwith intercellular substances perform a specific function. Such an organisation is called tissue.
• Simple Epithelium: Simple epithelium is composed of a single layer of cells and functions as a lining for body cavities, ducts, and tubes.
• Compound epithelium: The compound epithelium consists of two or more cell layers and has protective function as it does in our skin.
• Squamous epithelium: The squamous epithelium is made of a single thin layer of flattened cells with irregular boundaries.
• Cuboidal epithelium: The cuboidal epithelium is composed of a single layer of cube-like cells. This is commonly found in ducts of glands and tubular parts of nephrons in kidneys and its main functions are secretion and absorption.
• Columnar epithelium: The columnar epithelium is composed of a single layer of tall and slender cells. Their nuclei are located at the base.
• Ciliated epithelium: If the columnar or cuboidal cells bear cilia on their free surface they are called ciliated epithelium.
• Glandular epithelium: Some of the columnar or cuboidal cells get specialised for secretion and are called glandular epithelium 
• Tight junctions: Tight junctions help to stop substances from leaking across a tissue.
• Adhering junctions: Adhering junctions perform cementing to keep neighbouring cells together. 
• Gap junctions: Gap junctions facilitate the cells to communicate with each other by connecting the cytoplasm of adjoining cells, for rapid transfer of ions, small molecules and sometimes big molecules.
• Loose connective tissue: Loose connective tissue has cells and fibres loosely arranged in a semi-fluid ground substance, for example, areolar tissue present beneath the skin.
• Adipose tissue: Adipose tissue is another type of loose connective tissue located mainly beneath the skin. The cells of this tissue are specialised to store fats. 
• Dense regular connective tissue: In the dense regular connective tissues, the collagen fibres are present in rows between many parallel bundles of fibres.
• Tendons: Tendons, which attach skeletal muscles to bones and ligaments which attach one bone to another.
• Dense irregular connective tissue: Dense irregular connective tissue has fibroblasts and many fibres (mostly collagen) that are oriented differently.
• Cartilage: The intercellular material of cartilage is solid and pliable and resists compression. Cells of this tissue (chondrocytes) are enclosed in small cavities within the matrix secreted by them.
• Bones: Bones have a hard and non-pliable ground substance rich in calcium salts and collagen fibres which give bone its strength.
• Blood: Blood is a fluid connective tissue containing plasma, red blood cells (RBC), white blood cells (WBC) and platelets.

Earthworm

• Earthworm: Earthworm is hermaphrodite (bisexual), i.e., testes and ovaries are present in the same individual.

Cockroach

• Malphigian tubules: Excretion is performed by Malpighian tubules. Each tubule is lined by glandular and ciliated cells. 
• Uricotelic insect: They absorb nitrogenous waste products and convert them into uric acid which is excreted out through the hindgut. Therefore, this insect is called uricotelic. 

Frogs

• Cutaneous respiration: Frogs respire on land and in the water by two different methods. In water, skin acts as aquatic respiratory organ (cutaneous respiration).
• Pulmonary respiration: On land, the buccal cavity, skin and lungs act as the respiratory organs. The respiration by lungs is called pulmonary respiration.