Histology π¬ Flashcards
what is the definition of endocrine gands?
ductless glands secreting hormonesβblood streamβtarget organ.
what are the major encocrine glands in the body?
- Pituitary gland
- Pineal body
- Thyroid & parathyroid glands
- Suprarenal gland
what are the master organs of the endocrine system?
The pituitary gland and the hypothalamus are called the master organs of the endocrine system.
What is the hypothalamus?
The portion of the brain to which the pituitary gland is attached.
what is the median eminence?
a structure at the base of the hypothalamus which acts as a functional link between the hypothalamus and the anterior pituitary gland.
what is the size of the pituitary gland?
pea-sized, compound endocrine gland.
what is the site of the pituitary gland?
at the base of the brain, where it lies in a depression in the sphenoid bone called the sell turcica.
what is the infindibulum?
a short stalk connecting the pituitary gland to the
hypothalamus.
what forms the pituitary gland?
* Anterior lobe (adenohypophysis):
a- Pars distalis.
b- Pars tuberalis.
c- Pars intermedia.
* Posterior lobe (neurohypophysis):
a- Pars nervosa.
b- Infundibulum (infundibular stalk, pituitary stalk).
compare between the anterior lobe (adenohypophysis) & the posterior lobe (neurohypophysis) accoding to staining, structure & parts
what is the histological structure of pars distalis?
stroma & parenchyma
stroma of pars distalis
a- Dense fibrous capsule.
b- Trabeculae extending from the capsule.
c- Reticular fibres surround the cords of cells
parenchyma of pars distalis
- Irregular anastomosing cords of cells.
- Surrounded with fenestrated capillaries.
- The cells are classified on the basis of their affinity or lack of affinity for dyes of routine staining (haematoxylin & eosin)
what are the cells in the parenchyma of pars distalis?
compare between acidophilic cells (alpha cells) and basophilic cells of pars distalis
what is the EM of pars distalis?
The cells of pars distalis reveal rER, mitochondria, a well developed Golgi apparatus & electron dense granules of variable size.
what is the site of Somatotrophs (somatotropic cells)?
They occur in groups along the blood sinusoidal capillaries.
what is the LM of Somatotrophs (somatotropic cells)?
- Shape: rounded cells.
- Stain:
H & E: stain intensely with eosin
PAS: -ve.
what is the EM of Somatotrophs (somatotropic cells)?
- rER, mitochondria, Golgi apparatus.
- Granules: numerous, spherical & electron dense (300-350 nm).
what is the function of Somatotrophs (somatotropic cells)?
secrete growth hormone.
what is the LM of Mammotrophs (prolactin cells) (Lactotroph cells)?
Site: They are distributed singly in the interior of the cell cords.
Shape: fusiform.
Stain: H & E: stain intensely with eosin, PAS: -ve.
what is the EM of Mammotrophs (prolactin cells)?
- rER, mitochondria, Golgi apparatus.
- Granules: numerous & electron dense (200 nm).
what happens to Mammotrophs (prolactin cells) during pregnancy?
- The cells hypertrophy under the stimulating effect of estrogen.
- Their granules become larger and irregular (600 nm) & they are called pregnancy cells.
what is the function of Mammotrophs (prolactin cells)?
secrete prolactin hormone.
what is the LM of Thyrotrophs?
- Shape: polygonal.
- Stain:
H & E: stain poorly.
PAS: +ve.
what is the EM of Thyrotrophs?
- rER, mitochondria, Golgi apparatus.
- Granules: small (140-160 nm).
what is the function of Thyrotrophs?
secrete thyrotrophic hormone (thyroid stimulating hormone) TSH.
what is the LM of Corticotrophs?
- Shape: oval or round.
- Stain:
H & E: stain poorly.
PAS: +ve.
what is the EM of Corticotrophs?
- rER, mitochondria, Golgi apparatus.
- Granules: 100-200 nm.
what is the function of Corticotrophs?
secrete synthesise a pro-hormone, by cleavage, they produce:
* ACTH which controls the function of suprarenal cortex.
* Melanocyte stimulating hormone & endorphin.
what is the LM of Gonadotrophs or (FSH-LH cells)?
- Shape: rounded.
- Stain:
H & E: stain poorly.
PAS: +ve.
what is the EM of Gonadotrophs or (FSH-LH cells)?
- rER, mitochondria, Golgi apparatus.
- Granules: variable in size & electron density (200-400 nm).
what is the function of Gonadotrophs or (FSH-LH cells)?
secrete follicle stimulating hormone (FSH) & luteinizing hormone (LH).
what is the LM of Chromophobic Cells?
- They occur in groups.
- Shape: rounded.
- Stain: lack affinity to stains.
what is the EM of Chromophobic Cells?
- Organelles: few.
- Granules: no or few.
what is the function of Chromophobic Cells?
- reserve cells capable of differentiation into either acidophils or basophils.
- exhausted glandular cells.
what does pars tuberalis form?
- It forms a collar surrounding the infundibulum of the neurohypophysis.
vascularity of pars tuberalis
It is a highly vascular region containing veins of the hypothalamo-hypophyseal system.
what do the cells of pars tuberalis secrete?
Most of the cells of the pars tuberalis secrete gonadotropins (FSH & LH) and are arranged in cords alongside the blood vessels.
what is pars intermedia?
It is a rudimentary region in human.
what cells does pars intermedia contain?
- It contains pale basophilic cells that contain small secretory granules.
- The cells often surround follicles filled with colorless colloid.
what is the function of pars intermedia?
It plays a role in the production of melanocyte-stimulating hormone (MSH).
β2 components, 2 cells & 2 fibersβ
what is the histological structure of pars nervosa?
1- Nerve fibres:
- Unmyelinated axons of hypothalamic neurosecretory neurons of the paraventricular and supra-optic nuclei.
- The axons end close to the fenestrated capillaries
2- Herring bodies:
- Basophilic masses formed of accumulation of neurosecretion in the terminal ends of the nerve fibres.
3- Fenestrated capillaries.
4- Pituicytes:
- Are branched neuroglial cells.
- Form about 25% of the pars nervosa volume.
5- Neuroglia cells.
6- Reticular fibres: around the capillaries.
N.B: Pars nervosa does not contain secretory cells.
what are the functions of pars nervosa?
- It is the reservoir for the neurosecretion (oxytocin & vasopressin or antidiuretic hormone), which is formed by the neurons of the supraoptic and paraventricular nuclei of the hypothalamus.
what happens to the secretory granules of pars nervosa?
- The secretory granules descend along the axons of the pituitary stalk and accumulate in the terminal bulbs nearby the fenestrated capillaries as Herring bodies.
- The secretory granules are absorbed to the circulation.
what is the Pineal body (Epiphysis cerebri)?
A small Cone shaped median endocrine gland
what is the site of the Pineal body (Epiphysis cerebri)?
- located at the posterior wall of the third ventricle near the center of the brain.
- It is attached to the roof of 3rd ventricle by a short stalk.
what is the histlogical structure of Pineal body (Epiphysis cerebri)?
Stroma:
A- Capsule: CT covered with pia mater.
B- Trabeculae: Septa between poorly defined lobules carrying blood vessels.
The parenchyma: (consists of)
A-Pinealocytes
B-Astrocytes
C-Calcified concretions (Brain sand)
what is the LM of Pinealocytes?
Shape: irregular.
Cytoplasm: pale basophilic
Nucleus: large, ovoid or polymorphic with one or two prominent nucleoli.
what are the types of processes of Pinealocytes?
- Short and thin processes which end on the adjacent pinealocytes.
- Longer and thinner processes which terminate on the blood vessels.
what is the EM of Pinealocytes?
sER, rER, free ribosomes, mitochondria, microtubules and electron dense granules.