Page 50 - PRE-U STPM BIOLOGY TERM 1

Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

• They have ducts that secrete substances.
• There are little capillaries in them.
• They produce liquid with proteins or enzymes.
• They are formed by invagination of epithelia as shown in
Figure 2.45.

2
Duct
Gland

Figure 2.45 Formation of exocrine gland
• Examples include tubular glands of the large intestine
and the sweat glands.
(iv) Endocrine glands
• They do not have ducts, thus the secretion is directly
emptied into the blood capillaries around them.
• There are a lot of capillaries in them.
• They produce hormones.
• They are formed is by detachment from the epithelia as
shown below in Figure 2.46.

Detached from epithelium
Gland with capillaries
Figure 2.46 Formation of endocrine gland
• Examples include the thyroid and the adrenal gland.

Nervous tissue 2013
Exam Tips
1. Nervous tissue is a group of nerve cells or neurones together with
Remember the formation
neuroglia or supporting cells, which transmits electro-chemical of endocrine and exocrine
messages called impulses along their membrane. glands.
2. Neurone consists of two parts, the cell body and the nerve process.
3. The cell body has different shapes, depending on the types of Summary
neurone. It is surrounded by a plasma membrane and contains a
nucleus like any normal cell. It has a lot of mitochondria, Golgi Nervous tissues
apparatus, endoplasmic reticulum, ribosomes (previously called 1. Motor neurone
Nissl’s granules) but no centriole. • Short dendron, long
axon for transmitting
4. The nerve process is the thin slender structure attached to the cell impulse from CNS to
muscles
body. It includes the axon, dendron and dendrites. Dendron transmits 2. Sensory neurone
impulse towards the cell body whereas axon transmits impulse away • Long dendron, short
from the cell body. The length of dendron and axon varies. It can axon for transmitting
be very long, up to over a metre in our body. Both are protected impulses from receptors
to CNS
by myelin sheath. The end of the axon or dendron is branched to 3. Interneurone
form smaller dendrites. Axon dendrites end with little knobs called • Dendron and axon same
length for transmitting
impulses from sensory
to motor neurones

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