Human beings have four types of tissue: muscle, epithelial, ner vous and connective. Muscle tissue Muscle tissue is made up of elongated cells called muscle fibres or myocytes. These contain fibrillar proteins, which become shorter in response to certain stimuli (contraction) and longer when the stimulus stops (relaxation). The cells in this tissue are highly dif ferentiated . 18 One idea for the exhibit representing this level of organisation is to use artistic drawings or paintings. You can look for photos online or study the images on these pages. You can use oil, tempera, coloured pencils, etc. 19 WORK WITH THE IMAGE. This is the epidermis. a) Why do you think the cells in this tissue are so close together, with hardly any intercellular space between them? b) Are the cells all the same? c) Why do they have the shape you see here? d) Which are the oldest cells? e) Which are the newest? 20 Which cell organelles are particularly developed in muscle fibre? And in glandular epithelial cells? 21 Bone injuries heal faster than cartilage injuries. Find out why. Skeletal muscle This is made up of elongated cells with one nucleus. Contraction is involuntar y. This tissue makes up the muscles of the walls of internal organs, such as those in the digestive system, blood vessels and the bladder. Smooth muscle This tissue looks striated and is made up of cylindrical cells with several nuclei . Contraction is voluntar y. It forms the muscles that are attached to the bones. This is made up of striated muscle cells with one or two nuclei . The cells are joined in a network. Contraction is involuntar y. Cardiac muscle, or myocardium, forms the heart wall . Cardiac muscle CHALLENGE 25 1 4. Tissues of the human body
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