Benha University
Faculty of Veterinary Medicine
Histology and Cytology Department
Histology Exam
(‫)برنامج جودة ومراقبة األغذية‬
February 2012
Complementary Histology Course
Time: - 3 hours
Please answer the following questions and illustrate your answers with diagrams.
‫مـــــن فضــــــــلك دعــــــم جمــــــيع اإلجـــــابات بالرســـوم التـوضــيحية و لن يلتفت إلى اإلجابات الزائدة‬
A- Give a full account on:-
Soma
It is the nucleus & surrounding cytoplasm except that of the processes.
Nucleus → large vesicular, euochromatic and centrally located with large nucleolus.
Mitochondria → abundant number especially at axon terminal
Golgi apparatus → in the form of tubules around the nucleus.
R.E.R. → it contain large number of R.E.R with free ribosome. RER arranged as parallel cisternae between
the cisternae are the free ribosome.
Under light microscopy, the free ribosomes “appear as basophilic granules “Nissle’s bodies and not present
in axon and in the area axon hillocks. SER are absent in perikaryon but present in the axon and dendrites as
tubules cisternae & irregular vesicles.
-Lysosome, is present as in normal cell .Lysosome coaless & form lipofuchsin granule which are observed in
neuron.
** Neurofilaments
Present in perikaryon & process.
when impregnated in the silver they form neurofibrils
** Inclusions
Perikaryon contains dark brown or black granules (melanin pigment) or light brown granules (lipofuchsin
pigment). They increase in advanced age.
Cortex of lymph node
Afferent lymphatics empty into the subcapsular (or cortical) sinus located immediately beneath the capsule.
This sinus connects to the medullary sinuses via intermediate or paratrabecular sinuses which run alongside
the trabeculae.
The outer cortex is populated primarily by B-lymphocytes along with macrophages, plasma cells, and
reticular cells. Lymphoid follicles are found here.
The inner (or deep) cortex contains mostly T-lymphocytes. This area also called paracortex or
paracortical zone. Few lymphoid nodules will be
found in this area. Contains specialized vessels called high endothelial venules (HEVs). They are lined with
plump, cuboidal endothelial cells with large nuclei. These vessels serve as the point of entry for lymphocytes
from the peripheral blood into the lymph node parenchyma.
Cornea of the eye
The second part of this tunic, the cornea, is the principal light refracting structure.
It forms the anterior part of the corneoscleral tunic, joining the sclera at the limbus or corneoscleral
junction.
The cornea is exposed to the environment on its outer surface, and is epithelial in nature.
The outermost part of the cornea is a stratified squamous layer, the corneal epithelium. This layer isn't
normally keratinized, of course.
The curvature of the cornea is what refracts light coming into the eye and provides for most of the
focusing; alterations in the shape of the cornea can have profound effects on vision, and surgical
procedures to correct vision problems take advantage of this fact.
The cells of the corneal epithelium sit on a thick basal lamina, Bowman's membrane,
The corneal epithelium varies in thickness among different species.
The bulk of the tissue in the cornea is the substantia propria, a thick collagenous CT in the form of
regular lamellae.
The inner surface of the cornea has a very thin, single layer of cuboidal epithelium, and between these
cells and the substantia propria
The Descemet's membrane and their basal lamina.
B- What do you know about:
Axon and dendrites.
Dendrites
Most nerve cells have numerous dendrites.
They are short & thick toward soma & thinner away of it.
It branched like tree branch.
The cytoplasm as like soma except pigment granules.
The dendrites covered by numerous spinous projections “ small “ known as ( synaptic spine ) ( dendritic
spine ) ( gemmules ) .
The dendrites not covered with myelin sheath.
Function → carry impulse to soma.
2-Axon
Neuron has only one axon.
Start from body soma in pyramidal region called axon hillock.
Long cylindrical & varies in length & diameter.
It has the same structure as body soma except pigment granules & Nissle's granules & endoplasmic
reticulum is smooth.
The axon cytoplasm "axoplasma" & Axon membrane ( Axolema ) covered by myelin sheath ( dendrites
not cover ).
The axon gives collateral branch.
Function → carry impulse away of the perikaryon
The Axon
The Dendrite
-Single.
-Usually multiple.
-Usually thin, and long.
-Usually stout, and short.
-Has a constant diameter throughout
- Thick near its origin, and
its length.
tapering towards its apex.
-Has a smooth contour.
Irregular contour.
-Branches at its terminal end only.
-Extensive branching along its
But it may give off "branches" which
course. The branches arise at
arise along its course at right angles.
acute angles.
-Contains neurofibrils but No Nissl
-Contains Nissl granules and
granules, which are also absent in the
neurofibrils which extend in its
axon hillock.
finest branches.
-Centrifugal conduction of nerve
-Centripetal conduction of nerve
impulse (i.e. away from the cell
impulse (i.e. to the cell body).
body).
Lymph node medulla.
Medulla
The medulla is composed of medullary cords of lymphatic tissue separated by medullary sinuses
which contain lymph.
Medullary cords contain lymphocytes (both T and B), macrophages, and plasma cells. This is the area
where plasma cells are formed, and, therefore, where antibody production takes place.
Follicles
Primary follicles are nodules or aggregates of small B-lymphocytes.
When a germinal center develops in a primary follicle, it becomes a secondary follicle. The presence of
germinal centers indicates the lymph node is being antigenically-stimulated. The lighter-staining germinal
center contains activated B-cells which eventually give rise to antibody-forming plasma cells. The germinal
center is surrounded by a cuff of small, dark B-lymphocytes called the mantle zone.
Dendritic Reticulum Cells (DRCs) are found in the germinal center. They trap antigens on their surface and
present them to B-lymphocytes. They are long-lived and difficult to see by light microscopy.
The B-cells found in the germinal center are large and have vesicular nuclei. These are proliferating cells, so
mitotic figures are not uncommon in this area.
Tingible body macrophages can also be found in the germinal center. These are large cells whose cytoplasm
contains phagocytized debris. Because their cytoplasm is not conspicuous (unless it's filled with something),
they appear as "clear areas" in the tissue.
Circulation of lymph
Afferent lymphatic vessels → subcapsular sinus → intermediate sinuses → medullary sinuses → efferent
lymphatic vessels.
Lymphatic vessels contain one-way valves to assure flow of lymph in proper direction.
Neuroglia cells.
Neuroglia cell (Glia cells):1- Astrocyte
2- Oligodendroglia
3- Microglia
4- Ependymal
1- Astrocyte
Protoplasmic Astrocyte
Fibrous Astrocyte
cytoplasm
Granular
Non granular
process
Short, thick and branched
Long, slender, smooth and
less branched
location
Abundant in gray matter
Abundant in white matter
function
Formation of myelin sheath in the CNS
Astrocyte gives pedicle or end feet on the capillary of the
brain that making change between materials from the blood
and the neuron.
2-Oligodendroglia:-
ectodermal in origin
-
small – spherical dense nuclei
-
short and small process than other
neuroglia
-
less branched process
-
it present in both gray and white matter
of
the CNS
-
It form myelin sheath in the CNS and also has phagocytic function.
3- Microglia:-
Mesodermal in origin
-
Small elongated with short branches
-
The
branches
appear
as
thorny
due to very small expansion over the
-
It present in both gray and white matter
-
It has phagocytic function
appearance
branches
4-Ependymal cells
-
Ectodermal in origin
-
It is the epithelial cell of the
CNS
-
Form
chorid
epithelial
layer
of
plexus which is ciliated
-
They may posses microvilli
& they are
columnar cell
-
They lined the central canal
and
the
cerebral ventricles
-
They may implicated in the formation of a diffusion barrier between spinal fluid & neuron in
CNS
Function
1- Supportive function.
2- Cerebrospinal fluid brain barrier.
3- Removal of toxic material from CSF.
4- Active transport system for the addition of material.
1. Describe Fully Your Internet Research.
C- Draw (ONLY) with complete data on your drawing the following:-
1. Spinal cord.
2. Retina.
3. Organ of Corti.
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‫سوف يعقـــــد امتحـــان الشفــــــوي بعـد اآلمتحــان النــظرى‬
‫مباشـــــــــرة بالقســـــــم‬
GOOD LUCK