Page 54 - PRE-U STPM BIOLOGY TERM 1

Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

(c) Smooth muscle
(i) Smooth muscle is also known as involuntary muscle, as it
is not under our conscious control but it is controlled by
the autonomic nervous system.
(ii) It is found in the alimentary canal, dermis, uterus, arteries
and trachea.
(iii) It is arranged in strands or layers. It is not branched or 2
attached to the bone.
(iv) It is made up of individual cells, each having its own
nucleus and plasma membrane.
(v) It has no striations, as its myofibrils do not align themselves
with thick and thin filaments forming bands.
(vi) It is supplied with nerves from the viseral motor neurone,
a part of the autonomic nervous system.
(vii) The muscle can contract rhythmically like peristalsis and
produces waves of contraction as in intestines. Its structure
is shown in Figure 2.54.

Nucleus
Cytoplasm
containing
actin and
myosin
filaments Cell surface
membrane

Figure 2.54 Smooth muscle
Connective Tissues
1. Connective tissues are groups of cells together with their products
that attach or are simply found between two different tissues.
They originate from the mesoderm layer of the embryo, becoming Language Check
Language Check
mesenchyme and later form the bones, cartilages, blood cells and
fibroblasts, which produce matrices. The matrices include the bone,
cartilage, fine fibres produced by fibroblasts. Blood cells produce
special proteins.
2. The compact bone has the following features:
(a) Bone is formed from osteocytes that secrete the matrix of
Language Check
calcium phosphate and carbonate, together with proteins. Language Check
(b) Compact bone consists of Haversian systems of cylindrical shape
with a Haversian canal in the centre. • Canaliculus – singular
Cannaliculi – plural

(c) The Haversian canal is supplied with blood vessels that bring • Lacuna – singular
raw materials for bone construction or it can be reversed as in Lacunae – plural
osteoporosis (a disorder of brittle bone).
(d) The Haversian canals are linked by a Volkmann’s canal, forming
an inter-connecting system for blood circulation.
(e) The osteocytes are found in small spaces called lacunae with
intricate tiny canaliculi for distributing the matrix during bone
formation.

99

02[STPM Bio T1].indd 99 3/29/18 5:08 PM