Tissues of the Body Four Main Categories Epithelial Tissue Cell types Squamous, or flat Cuboidal Columnar If there is only a single layer it is called ‘simple’ If there are lots of layers it is called ‘stratified’ Sometimes a single layer can look like multiple layers. This is called ‘pseudostratified’ The wall of the bladder has cells of many different shapes to allow for stretching. This is called transitional epithelium. Types of Connective Tissue Areolar Tissue A loose, semifluid tissue containing collagen and elastic fibres. This tissue often holds internal organs in their position and is also found in the subcutaneous layer of the skin. Adipose Tissue A type of areolar tissue which contains mainly fat cells. It is found in the subcutaneous layer of the skin, around the kidneys and heart, and in the breasts. Dense Connective Tissue This consists mostly of collagen arranged in parallel bundles, which makes it very strong. Tendons and ligaments are made of this tissue Elastic Connective Tissue This mainly consists of elastic fibres which give the tissue a yellowish colour. It is found in the respiratory system and the walls of arteries Reticular Connective Tissue This contains lots of thing fibres which branch to form a supportive network Reticular tissue is found in lymph nodes, the spleen and red bone marrow Cartilage This is a strong, resilient tissue, more flexible than bone. There are three types. 1. Hyaline cartilage – found in synovial joints and forming part of the nose 2. Fibrocartilage – much tougher, containing large amounts of collagen, this is found in the intervertebral discs 3. Elastic Cartilage – this has more elastic fibres and is found in the external ear and epiglottis Bone (osseous) Tissue and Blood, are the final two connective tissues Muscle Tissue This has the ability to contract and create movement. The three types are: Cardiac Skeletal Smooth Nerve Tissue This category includes both nerve cells and glia.