Histology

1. Histology

2. Histology:
-Histology is the study of the tissues of the body & how
these tissues are arranged to form organs.

3. Cell
ECM
-Both cells & extracellular cellular matrix (ECM)
comprise the tissues.
-Cells produce the ECM locally.

4. -The ECM supports the cells & through which the
nutrients & waste products can be transported.

5. Cytology

6. Cytology:
Study the structure of the cells which make up tissues &
organs.

7. Cell:
-Smallest structural & functional unit of living matter of
an organism.
-The cell consists of nucleus & cytoplasm.

8. Nucleus:
-The main component of the cell, guiding the cell
structurally & functionally.
-The nucleus usually appears as a rounded or oval
structure, often near the cell’s center.
Cell
Nucleus

9. Components of
the nucleus
Nuclear
envelop
Chromatin Nucleolus

10. Nuclear envelop:
- Transmission electron microscopy (TEM) reveals that the
envelope has two concentric membranes (outer &
inner) separated by a narrow perinuclear space.

11. -The two membranes are fused to form channels; nuclear
pores.

12. -The pores play a role in exchange of material (ions
& molecules)between the nucleus & cytoplasm.

13. Chromatin:
- Chromatin consists of double helix of deoxyribonucleic
acid (DNA) & all associated proteins.
- The DNA is organized in chromosomes which carry the
genetic information (genes).

14. EC:
Euchromatin
HC:
Hetrochromatin
Microscopically two types of chromatin can be recognized
in nuclei of non dividing cells.
1. Euchromatin appears as finely dispersed granular
material in the electron microscope & as lightly stained
basophilic areas in the light microscope.

15. EC:
Euchromatin
HC:
Hetrochromatin
2. Heterochromatin appears as coarse, electron-dense
material in the electron microscope & as intensely
basophilic clumps in the light microscope.

16. The euchromatin is active for protein synthesis that
produces 3 types of ribonucleic acids (RNA):
A- Messenger (m RNA).
B- Transfer (t RNA).
C- Ribosomal (r RNA).

17. Nucleolus:
- Spherical basophilic body within the nucleus, the
basophilia of nucleolus is due to the presence of
concentrated ribosomal RNA (rRNA).
- It is not surrounded by unit membrane.
- It is synthesized rRNA molecule & ribosomal subunits.
Nucleolus

18. Cell membrane or plasma membrane or plasmalemma:
-It surrounds the cell & acts as a selective barrier
regulating the passage of substances into & out of the
cell.

19. -It is range from 7.5 to 10 nm in thickness.
- With TEM appears as a trilaminar that consists of outer
& inner electron dense layers enclosing intermediate non
staining layer.

20. -- The “fuzzy” material on the outer surface of the
membrane represents the glycocalyx of oligosaccharides
chains.
Glycocalyx

21. -It consists of phospholipid bilayer containing cholesterol
& proteins (integral & peripheral) with chains of
oligosaccharides; glycoproteins or glycolipids (externally).