Tissues and organs

Epithelial tissue is necessary for protection, diffusion, filtration, secretion, absorption and others. Simple epithelium with its single layer of cells is found in organs in which the principal functions are diffusion (lungs), filtration (kidneys), secretion (glands), or absorption (intestines). The selective movement of materials through epithelium would be hindered by a stratified epithelium, which is found in areas where protection is a major function. The multiple layers of cells in stratified epithelium are well adapted for a protective role. Damaged cells are replaced by cells from deeper layers and a continuous barrier of epithelial cells is maintained in the tissue. Stratified squamous epithelium is found in areas of the body where abrasion can occur such as the skin, mouth, throat, esophagus, and anus. Cells involved in diffusion and filtration are normally flat and thin. For example, simple squamous epithelium forms blood and lymph capillaries, the alveoli of the lungs, and parts of the kidney tubules.

Connective tissue is found in tendons, ligaments, cartilages, bones, dermis of skin, arteries, spleen and others. This tissue produces new blood cells, allows growth of long bones, connects different structures, provides great strength and support for bones, transports oxygen, carbon dioxide, hormones, nutrients, waste products and has some other functions.

Muscular tissue has the ability to contract. Muscles contract to move the entire body, to pump blood through the heart and blood vessels, and to decrease the size of hollow organs such as the stomach. Skeletal muscles represent a large portion of the human body's total weight. Skeletal muscle attaches to the skeleton and by contracting causes the major body movements. Cardiac muscle is the muscle of the heart. The contraction of the cardiac muscle is responsible for pumping blood. Smooth muscles are widespread throughout the body and are responsible for a wide range of functions such as movements in the digestive, urinary, and reproductive systems.

Nervous tissue conducts impulses all over the body. Nerve cells, or neurons, located in the brain, spinal cord, and cell processes, conduct not only impulses and store "information", and in some ways integrate and evaluate data. Neuroglia support neurons and form a selectively permeable barrier between neurons and other cell types.

Ex. 24. Answer the following questions:

1. What is the function of epithelial tissue? 2. Where is connective tissue located? 3. What is the function of connective tissue? 4. What is cardiac muscle? 5. Where are nervous cells located? 6. What is the function of nervous tissue?

Ex. 25. Read the data of the following table and speak on the location and functions of different tissues:

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