7. STRUCTURAL ORGANISATION IN ANIMALS
ANIMAL TISSUES
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 co-ordination 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.
