Histology is the study of cells and tissues that are too small to see with the naked eye using microscopy. It involves sectioning tissues into thin slices and staining them so they can be examined under microscopes. The basic unit of life is the cell. Cells come in different shapes depending on their function. Groups of common cell types form tissues, and combinations of tissues make up organs in the body like the heart, stomach, and liver. The cell is bounded by a membrane and contains a nucleus for DNA and cytoplasm with organelles that perform different functions. The cell membrane regulates what enters and exits the cell and maintains its shape while allowing for specialized functions in different cell types.

1. M.Sc Hamid K AL-Tameemi

2. Histology, is the study of cells and tissues of animals,
humans and plants that are too small to be seen with the
naked eye.
Cytology a branch of biology dealing with the structure,
function, multiplication, pathology, and life history of
cells : CELL BIOLOGY
Cell is the basic structural and functional unit of life.
Cells have various shapes due to their functions.

3. By looking at tissue under the microscope, For example,
if a person has cancer, examining the tissue under the
microscope will reveal how the cancer cells are acting
and how they affect normal human tissue.
Each cells take their shapes and adepted to achive
ceratian functions, such as neuron cells specialized to
transmit the nerve impulse , RBCs to transport oxygen
and so on

5. This commonly involves studying tissues and cells
using histological techniques such as sectioning and
staining, and then looking at them under an electron or
light microscope.
Sectioning involves cutting tissue into very thin slices
so they can be examined. Histological stains are added
to biological structures, such as tissues, to add colors or
to enhance colors so they can be more easily
distinguished when they are examined.

7. Cells, Tissues And Organs
The human body, like that of most other animals and plants,
is made up of units called cells. Cells can differ greatly in
their structure. However, most of them have certain features
in common.
Aggregations of cells of a common type (or of common
types) constitute tissues. Apart from the cells many tissues
have varying intercellular substances that may separate the
cells from one another. Organs (e.g., the heart, stomach or
liver) are made up of combinations of various kinds of
tissue.

8. Cell Structure
A cell is bounded by a cell membrane (or plasma
membrane) within which is enclosed a complex material
called protoplasm. The protoplasm consists of a central,
more dense, part called the nucleus; and an outer less
dense part called the cytoplasm.

9. The nucleus is separated from the cytoplasm by a nuclear
membrane. The cytoplasm has a fluid base (matrix) which is
referred to as the cytosol or hyaloplasm. The cytosol
contains a number of organelles which have distinctive
structure and functions.

11. Cell membrane
The cell membrane is a physical and chemical barrier
which separates the inside of the cell from the outside
environment
Physical properties of the cell membrane:
1- Impermeable to water-soluble molecules (but not to
water)
2- Soft and flexible
3- Spontaneously prone to forming self-repairing pores

12. Composition of the cell
membrane:
Lipids
-Outer membrane: phosphatidylcholine and sphingomyelin
-Inner membrane: phosphatidylethanolamine, phosphatidylserine
and phosphatidylinositol
Variable amounts of cholesterol
Proteins
-Integral proteins
-Peripheral proteins

13. Polysaccharides
Glycosylated components of glycolipids and glycoproteins
These form the cellular glycocalyx
Water
Present between lipid molecules in a highly organised form, as
well as bulk water in pores and channels
Ions
-Adsorbed ions (eg. calcium, sodium)
-Attracted to the membrane by the intrinsic negative charge of the
phospholipid heads.

15. The cell membrane is of great importance in
regulating the activities as follows.
(a) The membrane maintains the shape of the cell.
(b) It controls the passage of all substances into or out of
the cell
(c) The cell membrane forms a sensory surface. This
function is most developed in nerve and muscle cells.

16. (d) The surface of the cell membrane bears
receptors that may be specific for particular
molecules (e.g., hormones or enzymes).
(e) Membrane proteins help to maintain the
structural integrity of the cell by giving attachment
to cytoskeletal filaments
(f) Cell membranes may show a high degree of
specialisation in some cells.