LEVELS OF
ORGANIZATION
Lecture 2
Levels of organization
• The human body consists of basic units of life known as
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cells.
Groups of cells similar in appearance, function and origin
join together to form tissues.
Different tissues then interact with each other to form
organs.
Finally groups of organs interact to form body systems.
Thus there are four levels of organization in the human
body:
• cells, tissues, organs and systems.
• Let us begin by examining the first level of organization.
Cells
• The cell is the basic unit of life and the bodies of
all plants and animals are built up of cells.
• Your body consists of millions of very small
specialized cells.
• It is interesting to note that all non-infectious
disorders and diseases of the human body are
really due to the abnormal behaviour of cells.
• Body cells are all built on the same basic plan.
• Most cells have the same basic
components as are shown in the figure but
they are all specialized to carry out
particular functions within the body.
• In your studies you will come across many
terms that relate to different types of cell.
• Now we will examine our first word root
which refers to cells:
Root Word
• Cyt
• (From a Greek word kytos, meaning cell.)
• Combining forms Cyt/o, also used as
the suffix -cyte
• (Remember that combining forms are
made by adding a combining vowel to the
word root.)
• Here we have a word that contains the root cyt:
• Reading from the suffix back, cytology means
the study of cells.
– (Remember when trying to understand medical
words, first split the word into its components, then
think of the meaning of each component and finally
write the meaning beginning with the suffix.)
• Cytology is a very important topic in
medicine as many diseases can be
diagnosed by studying cells.
• Cells removed from patients are sent for
cytological examination to a hospital
cytology laboratory where they are
examined with a microscope.
• (In the word cytological, -ical is a compound
suffix meaning pertaining to or dealing with.)
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• Name the components of the word and give their
meanings:
• Reading from the suffix back, the meaning of
cytopathy is:
………………………………………………..
Root Word
• The root -path- can be used at the beginning and in the
middle of a compound word as in the next two examples.
• Write the meaning of these words:
path/o/logy …………………………………………..
C. cyt/o/path/o/logy ………………………………….
B.
• write the meaning of the words below. Remember to read
the meaning from the suffix back to the beginning of each
word:
cyto/lysis…………………………
E. cyto/tox/ic ……………………………..
F. cyto/logist …………………………………..
D.
• In the above examples cyt/o was used at the beginning of
words. It can also be used at the end of words in
combination with other roots, its meaning remaining the
same.
• Name the components of the following word and find its
meaning.
• The meaning of erythrocyte is: ………………………
• find the combining forms of melanin and fibre to build
words that name these cells.
• A cell containing melanin……………………..
• A cell that produces fibre …………………..
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• Complete the table by looking up the combining
forms of the following roots and build words that refer
to cell types.
Root Word
• Blast
• A Greek word meaning bud or germ.
• It is used to denote an immature stage in cell
development or a cell that is forming something
• Combining forms Blast/o, also used as the suffix
–blast
• 4- write the meaning of:
• osteo/blast ………………..
• fibro/blast …………………..
• haemo/cyto/blast ………………………..
Tissues
• As cells become specialized, they form groups of
cells known as tissues.
• Definition
• A tissue is a group of cells similar in appearance,
function and origin.
• There are four basic types of tissue:
• epithelial, muscle, connective and nervous tissue;
• these form the second level of organization in the body.
• The study of tissues is known as histology, the
combining form coming from a Greek word histos
meaning web (web of cells).
• Histology is an important branch of biology and
medicine because it is used to identify diseased
tissues.
• The histology and cytology laboratories are
usually sections of the pathology laboratory of a
large hospital.
Root Word
• Hist
• (From a Greek word histos, meaning web. It is
used to mean the tissues of the body.)
• Combining forms Hist/i/o
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• Find the meaning of:
• histo/chemistry ………………………..
• histo/patho/logy ……………………….
• histo/logist ……………………………
• histo/lysis ……………………………
• Cells and tissues are very small and need
to be examined using an instrument known
as a microscope.
• Find the meaning of:
• micro- …………………..
• micro/scope ………………….
• micro /scopy …………………..
• micro/scop/ist …………………….
CASE HISTORY 1
• The object of this exercise is to understand
words associated with a patient's medical
history.
Diagnosis of an AIDs related infection
• Mr A, a 34-year-old HIV positive patient with symptoms of AIDs,
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was admitted to the unit following a chest X-ray that revealed a
left upper lobe mass.
A CT scan confirmed the presence of a mass within the
peripheral aspect of the left upper lobe, and a small left pleural
effusion.
CT guided fine needle aspiration of the left upper lobe mass was
performed and the biopsy material sent to the histology
laboratory for analysis by the duty pathologist.
Cytological examination of direct smears using optical
microscopy revealed a mucoid background, moderate
cellularity, polymorphonuclear leucocytes , and lymphocytes .
A significant number of oval yeast-like cells
No malignant cells were observed.
• A sample of the biopsy material was sent for culture and
sensitivity testing to the microbiology laboratory.
• The report was positive for encapsulated fungal yeast
forms morphologically compatible with pathogenic
cryptococcus species (Cryptococcus neoformans).
• Mr A's diagnosis was cryptococcosis, a condition seen
mainly in AIDs patients and others with compromised
immune systems.
Word Help
• AIDs acquired immune deficiency syndrome
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• aspect part of a surface facing a designated
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direction
aspiration withdrawal by suction of a fluid
biopsy removal and examination of living tissue
budding performing asexual reproduction by
producing buds that grow into new cells
cellularity state/condition of being made up of
cells
compromised lacking the ability to mount an
adequate immune response
cryptococcus a yeast-like fungus that causes
disease in humans
cryptococcosis abnormal condition of infection
with cryptococcus
CT computed tomography, a technique of using
X-rays to image a slice or section through the body
culture & sensitivity testing growing
microorganisms in the laboratory and testing them
for sensitivity to antibiotics
effusion a fluid discharge into a part/escape of
fluid into an enclosed space
encapsulated enclosed on a capsule or sheath
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histiocytes the word means a tissue cell
(actually a large cell found in connective
tissue that helps defend against infection)
HIV-positive presence of antibodies to the
human immunodeficiency virus in the blood, it
indicates the virus has infected the body
lobe a division of an organ into smaller
sections, here a lobe of the lung
malignant dangerous, life threatening
mass lump/collection of cohering cells
morphologically referring to the form and
structure of an organism
mucoid resembling mucus
peripheral pertaining to the periphery i.e. the
surface of an organ
pleural pertaining to the pleura/pleural
membranes that surround the lungs
polymorphonuclear pertaining to or having
nuclei of many shapes