Page 77 - Understanding NCERT Science 09
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of epithelium. This is called the simple of skin). Simple squamous epithelial cells are
squamous epithelium (squama means scale extremely thin and flat and form a delicate
lining. The oesophagus and the lining of the
mouth are also covered with squamous
epithelium. The skin, which protects the body,
is also made of squamous epithelium. Skin
epithelial cells are arranged in many layers to
prevent wear and tear. Since they are arranged
(a) Squamous
in a pattern of layers, the epithelium is called
stratified squamous epithelium.
Where absorption and secretion occur, as
in the inner lining of the intestine, tall epithelial
cells are present. This columnar (meaning
‘pillar-like’) epithelium facilitates movement
across the epithelial barrier. In the respiratory
tract, the columnar epithelial tissue also has
cilia, which are hair-like projections on the
outer surfaces of epithelial cells. These cilia can
move, and their movement pushes the mucus
forward to clear it. This type of epithelium is
thus ciliated columnar epithelium.
Cuboidal epithelium (with cube-shaped
cells) forms the lining of kidney tubules and
ducts of salivary glands, where it provides
(b) Stratified squamous mechanical support. Epithelial cells often
acquire additional specialisation as gland cells,
which can secrete substances at the epithelial
surface. Sometimes a portion of the epithelial
tissue folds inward, and a multicellular gland
is formed. This is glandular epithelium.
6.3.2 CONNECTIVE TISSUE
Blood is a type of connective tissue. Why would
it be called ‘connective’ tissue? A clue is
(c) Cuboidal
provided in the introduction of this chapter!
Now, let us look at this type of tissue in some
more detail. The cells of connective tissue are
loosely spaced and embedded in an
intercellular matrix (Fig. 6.10). The matrix may
be jelly like, fluid, dense or rigid. The nature
of matrix differs in concordance with the
function of the particular connective tissue.
Activity 6.4
(d) Columnar (Ciliated) Take a drop of blood on a slide and
observe different cells present in it
Fig. 6.9: Different types of epithelial tissues under a microscope.
66 SCIENCE
Rationalised 2023-24
