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1. Previous exams' questions
Histology
1- Describe microscopic structure of the follicular cells of the thyroid gland
2- Describe microscopic structure of parafollicular cells of the thyroid gland
Answer:
Follicular cells Parafollicular cells
Percentage 99.9% 0.1%
Shape Cuboidal Larger
Nucleus Central rounded nucleus
Stain Basophilic cytoplasm Pale cytoplasm
LM Rest on basement membrane,
extend to lumen
Columnar (active)
Squamous (inactive)
Rest on basement membrane
Apex never reach the lumen
EM  polypeptide synthesizing
cell
 rER
 Mitochondria with
lamellar cristae
 Supranuclear golgi
apparatus
 Small apical secretory
granules
 Luminal border with
microvilli
 Phagosomes and
lysosomes
 Moderate amount of
organelles of polypeptide
secreting cell
 Infranuclear golgi
apparatus
 Basal dense secretory
granules
 No phagosomes or
lysosomes
Secretions Secretions are stored extracellular
in lumen
Secretions stored inside cell
Hormones Secrete thyroid hormones Secrete calcitonin
3- Enumerate cells of pars distalis in pituitary gland
Answer:
Chromophils 48% & chromophobes 52%
Chromophils
Acidophils 37% Basophils 11%
Somatotrophs
mamotrophs
Thyrotrophs
Gonadotrophs
Corticotrophs

2. 4- What are chromaffin cells? Describe the EM of it?
Answer:
 Chromaffin cells are one type of cells in adrenal medulla which undergo chromaffin reaction by
adding chromic salts lead to deep brown color +Ve chromaffin , it secretes EP/NE
 Arranged in rounded groups or short cords , related to blood capillaries
 Large ovid cells with large spherical nucleus, pale basophilic cytoplasm
EM
Protein synthesizing cell with rER, golgi, mitochondria with lamellar cristae, secretory granules
NE granules EP granules
Larger
Eccentric core within the limiting membrane
Electron dense
Smaller
Content fill the granule
Less dense
5- Mention four main histological structures of post pituitary gland?
6- Enumerate the structures in pars nervosa of pituitary gland?
Answer:
 Unmyelinated nerve fibers :coming from supraoptic & paraventricular nuclei of
hypothalamus, carry neurosecretions to pars nervosa
 Hering bodies: acidophilic homogenous bodies (accumulation of neurosecretions at dilated
end of axons)
 Pituicytes: modified branching glial cells with isolative, nutritive, supportive function
 Fenestrated blood capillary plexus
7- The diagram show part of one of the endocrine glands:
Name this gland?
 Thyroid gland
Name the pointed organelles at A,B &C ,
correlate them to cell's function?
 A: microvilli to ↑ surface area for hormone
secretion into lumen & facilitate exo &
endocytosis
 B: rER synthesize thyroglobulin
 C: secretory granules :contain calcitonin
which lower blood calcium level
Name & describe the LM of the cell pointed at C?
 Parafollicular cell
 Large cell with pale cyroplasm resting on basement membrane , apical part never reach
the lumen

3. 8- What are spongiocytes? Describe the EM features of these cells?
 Spongiocytes are the cells of zona fasciculata of adrenal cortex
 The are arranged in cords (1 or 2 cell thickness) trapping blood capillaries
 Large polyhedral cells with large pale nucleus & pale cytoblasm with numerous lipid droplets
(so called spongiocytes)
EM :
Steroid secreting cell with sER, mitochondria with tubular cristae, lipid droplets of cholesterol &
ascorbic acid
9- Describe the histological characteristics of beta cells of islets of Langerhans
Answer:
Beta cells Alpha cells Delta cells
Site &
percentage
Occupy the central part of islets
70% of the islet cells
Occupy the periphery
20% of islet cell
5-10% of islet
cells
Shape Small oval large Small
Gomori
technique
Deep basophilic Red
EM Rectangular crystalline granules
surrounded by electronlucent halo
Large with homogenous Dense
core surrounded by clear halo
Secretion Insulin secretion Glucagon secretion Somatostatin
Granules Alcohol soluble, not water soluble Water soluble not alcohol
soluble