7. STRUCTURAL ORGANISATION IN ANIMALS
ANIMAL TISSUES
II. CONNECTIVE TISSUE
·
It links and supports
other tissues/organs.
·
They are most abundant in
complex animals.
·
All connective tissues
except blood have fibroblast cells.
They secrete structural fibrous proteins called collagen & elastin. They give
strength, elasticity & flexibility to tissue.
·
The cells also secrete
modified polysaccharides (matrix),
which accumulate between cells and fibres.
· Types
of connective tissues: Loose, Dense & Specialised.
1. Loose Connective Tissues
In this,
cells (fibroblasts, macrophages, mast
cells etc.) and fibres are loosely arranged in a semi-fluid matrix.
It is 2 types: Areolar & Adipose.
o
Areolar tissue:
-
Present beneath the skin.
-
It serves as a support
framework for epithelium.
o
-
Seen mainly under skin.
-
Its cells (adipocytes) store fats.
- Excess nutrients which are converted into fats are stored in this tissue.
2. Dense Connective Tissues
In this, fibres and fibroblasts are compactly packed.
2 types:
o
Dense regular connective
tissues:
-
-
Collagen fibres are
present in rows between many parallel bundles of fibres.
-
E.g. tendons &
ligaments.
i. Tendons: Attach
muscles to bones.
ii. Ligaments: Attach
one bone to another.
o
Irregular
pattern of fibres.
- Fibroblasts & fibres (mostly collagen) are
oriented differently.
- This tissue is present in skin.
3. Specialized Connective Tissues
·
o In this, intercellular material (matrix) is solid and pliable (due
to chondroitin
salts) and resists compression.
o Cartilage
cells (chondrocytes) are enclosed in
small cavities within the matrix secreted by them.
o Most
of the cartilages in vertebrate embryos are replaced by bones in adults.
o Cartilage
is present in the tip of nose, outer
ear, joints in the vertebral column, limbs and hands in adults.
·
o It
has hard and non-pliable matrix rich in calcium
salts and collagen fibres which
give bone its strength.
o Bone cells (osteocytes)
are seen in spaces called lacunae.
o Functions:
§ It
provides structural frame to the body.
§ Support
and protect softer tissues and organs.
§ Limb
bones serve weight-bearing functions.
§ Take
part in locomotion and movements.
§ Blood
cells are produced in bone marrow.
· Blood:
o A
fluid connective tissue containing plasma,
red blood cells (RBC), white blood cells (WBC) and platelets.
o Helps in the circulation of various substances.
Fab work.
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