Lessons 4 · 1 lessons · O. Mavlonov, T. Tilavov, B. Aminov. Biology (Human body and health), Grade 8. Revised and expanded 6th edition. “O‘qituvchi” Publishing and Printing Creative House, Tashkent, 2019
4
Tissues, organs and the organism
Textbook: pp. 14–16
GoalDistinguish tissue types, organs, organ systems and body cavities.
New words
tissue · to‘qimaorgan · organorgan system · organlar sistemasidiaphragm · diafragma
Explanation
Cells of similar structure and function, together with intercellular substance, form a tissue. Humans have four kinds: epithelial (covers the body and organ surfaces, protects, secretes juices), connective (blood, lymph, bone, cartilage, tendons, fat), muscle (contracts to produce movement; striated skeletal, cardiac and smooth muscle) and nervous tissue (neurons and neuroglia, which link and control organs). A part of the body made of one or several tissues and having a definite shape and function is an organ. Organs that do one job together form a system: musculoskeletal, circulatory, respiratory, digestive, excretory, nervous, sensory and reproductive. Body cavities: the cranial cavity (brain), spinal canal (spinal cord), chest cavity (heart, lungs), abdominal cavity (stomach, liver, intestines) and pelvis; the muscular diaphragm separates the chest and abdominal cavities.
Worked examples
The stomach contains several tissues: epithelium on the inside, smooth muscle in the wall, nervous tissue and blood vessels – therefore it is an organ.
Running is not only muscle work: the nervous, respiratory, circulatory, musculoskeletal and sweating systems work together.
Class activity
Draw a human outline on paper, mark the cavities (chest, abdomen, pelvis) and write the organs inside them.
Practice
1
Name the four kinds of tissue.
Epithelial, connective, muscle and nervous tissue.
2
Which tissue does blood belong to and why?
Connective tissue: the type whose intercellular substance is liquid (plasma).
3
Where is the diaphragm and what does it do?
Between the chest and abdominal cavities; it separates them and, by contracting and relaxing, changes their volume.
4
How does muscle tissue differ from a whole muscle (e.g. the biceps)? What about a whole bone?
Muscle tissue is a group of similar cells, i.e. a tissue. A whole muscle also contains connective-tissue sheaths, blood vessels and nerves, so it is an organ; a whole bone (bone tissue, cartilage, marrow, vessels and nerves) is an organ too.