III. Muscle Tissue
- The tissues made of many muscle fibres (muscle cells).
- Muscle fibres are composed of numerous fine myofibrils.
- Muscle fibres can contract (shorten) and relax (lengthen).
- Muscles take part in locomotion and movements.
- Muscles are 3 types: skeletal, smooth and cardiac.
1. Skeletal (striated or voluntary) muscle
- They are attached to bones. E.g. Biceps.
- Striations are present in muscle fibres.
- Muscle fibres are bundled together in a parallel fashion.
- A sheath of tough connective tissue encloses several bundles of muscle fibres.
2. Smooth (non-striated or visceral) muscle
- Involuntary and fusiform (Fibres taper at both ends).
- No striations.
- Cell junctions hold them together and they are bundled together in a connective tissue sheath.
- They are seen in the wall of internal organs such as the blood vessels, stomach and intestine.
3. Cardiac muscle
- Involuntary muscle seen only in the heart.
- Cell junctions fuse the plasma membranes of cardiac muscle cells and make them stick together.
- Communication (gap) junctions (intercalated discs) at some fusion points allow cells to contract as a unit, i.e., when a cell receives signal to contract, other cells also contract.
IV. Neural Tissue
- Made up of neurons (unit of neural system).
- Responsible for control and coordination of the body.
- Neurons are excitable cells. They carry impulses.
- Neurons are protected and supported by neuroglial cells.
- Neuroglia make up more than half the volume of neural tissue.
Organ and Organ System
- Cells → tissues → organs → organ systems.
- This organization is essential for better coordinated activities of cells.
- An organ is made of one or more type of tissues. E.g. Heart has epithelial, connective, muscular & neural tissues.
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