مقرر_الهيستو_بلك_الغدد_دفعة_خامسة_-مضغوط-مضغوط (2).pdf

ENDOCRINE SYSTEM
Dr. Hana Abusaida
MSc (Manchester, U.K.)
Histology Department
Faculty of Medicine,
Tripoli University
2018-2019
Lecture 1
• Overview
• PITUITARY GLAND
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OBJECTIVES LEARNING
By the end of the Lecture, students should be able to:
 Describe the histology of the following:
•Pituitary Gland (Hypophysis)
•Adrenal Glands
•Pancreatic Islets
•Diffuse Neuroendocrine system
•Thyroid Gland
•Parathyroid Glands
•Pineal Gland
Dr.Hana Abusaida, Histology Department, Tripoli University
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• The endocrine system consists of endocrine glands:
• They develop as invagination from surface epithelium,
then separate.
• Release hormones , directly into blood stream
• Have no ducts.
• These hormones are:
– chemical messengers.
– act on distant target cells
– target cells have receptors respond to the hormones.
– regulate functions of different organs.
Dr.Hana Abusaida, Histology
Department, Tripoli University
Overview
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• The endocrine system and nervous system work together.
1. Internal communication
– Nervous system - both electrical and chemical
– endocrine system- only chemical
2. Speed and persistence of response
– nervous - reacts quickly, stops quickly
– endocrine - reacts slowly (hormone release in seconds or
days), effect may continue for weeks
3. Area of effect
– nervous - targeted and specific (one organ)
– endocrine - general, widespread effects (many organs)
Comparison of Nervous and Endocrine Systems
(Differences)
Dr.Hana Abusaida, Histology Department,
Tripoli University
4

Neuron
Nerve impulse
Neurotransmitter
Target cells
Target cells
(b) Endocrine system
(a) Nervous system
Endocrine
cells
Hormone in
bloodstream
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Communication by the Nervous and Endocrine
Systems
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Chemical types of hormones
• Steroids: lipid soluble hormones of adrenal
cortex.
• Proteins: water soluble hormones of pituitary.
• Aminoacids: water soluble as catecholamine
and lipid soluble as thyroxin.
Overview
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1- paracrine secretion, cell secretes chemicals
(signals) into intercellular space, affect the neighboring
cells.
2- Endocrine secretion, cell secretes chemicals
into the bloodstream, affect . distant target cells.
3- Autocrine signaling, cell secrete signals to itself,
affect the same cell.
4- Juxtacrine signaling, also known as contact
dependent signaling, by gap junction, affecting contact
cell.
Types of hormone signals secretion
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Types of hormone signals secretion
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* Pure endocrine organs
1. Pituitary gland
2. Pineal gland
3. Thyroid gland
4. Parathyroid glands
5. Adrenal: 2 glands
* Endocrine cells in other
organs have endocrine
functions:
1. Pancreas
2. Thymus
3. Gonads
4. Hypothalamus
5. Heart
6. Gut
7. Kidney.
Organs of
endocrine system
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1- PITUITARY GLAND
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
Also called hypophysis lies in the
sella turcica
- resembles a golf club .
• The master endocrine gland.
• Controls other endocrine glands.
• Controlled by hypothalamus.
• Attached to base of brain by the
infundibulum (stalk).
Composed of:
1- Neurohypophysis (posterior lobe), resemble CNS tissue including:
* Infundibulum: stalk (IS) + median eminence.
* pars nervosa (PN).
2- Adenohypophysis (anterior lobe), typically glandular including:
* pars distalis anterior(PD).
* pars intermediate (PI).
*pars tuberalis posterior(PT)
PITUITARY GLAND
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Lobes Of The Pituitary Gland
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Lobes Of The Pituitary Gland
Hypophysis cerebri consists of 2 glands that are united
anatomically but functions differently.
Pars Distalis
(anterior lobe)
Pars
Intermedia
Pars Tuberalis
Neurohypophysis Adenohypophysis
Infundibulum Pars Nervosa
anterior lobe
posterior lobe
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Hormones of the Anterior Pituitary
• GH: growth hormone: stimulate the body growth
• Prolactin (LTH): luteotropic hormone (lactogenic hormone:
stimulates milk secretion by mammary gland during lactation
• ACTH: adrenocorticotropic hormone: stimulate adrenal cortex
• FSH: follicle stimulating hormone: stimulates growth of
follicles in the ovary & spermatogenesis in the testis.
• LH: luteinizing hormone: stimulates secretion of estrogen &
progesterone & ovulation (in female)
• ICSH: Interstitial cell stimulating hormone: stimulate release
of testosterone (in male).
• TSH: thyrotropic hormone or thyroid stimulating hormone.
• MSH: melanocyte- stimulating hormone
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Oxytocin and ADH are:
• Synthesized in nuclei of
hypothalamus.
• Travel within axons of hypothalamo-
hypophyseal tract in neural stalk to
reach pars nervosa.
• Accumulate as Herring bodies.
• Pass through fenestrated capillaries to
blood.
• Oxytocin: stimulates contraction of
smooth muscle of uterus during
labour.
• Stimulate milk ejection during
lactation.
Hormones of the posterior Pituitary
Antidiuretic hormone (ADH):
Stimulates resorption of water from kidneys.
Stimulates contraction of smooth muscle fibers to increase
blood pressure.
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Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Functions of pituitary gland
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Histology
Pituitary Stalk
pars nervosa
infundibulum
pars distalis
pars tuberalis
pars intermedia
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Blood Supply of pituitary gland
* They are two groups of vessels:
1. Superior hypophyseal arteries
supply infundibulum (median
eminence and stalk) & pars
distalis.
2. Inferior hypophyseal arteries
supply neurohypophysis.
Superior hypophyseal arteries forms a:
• primary capillary network in the stalk
• secondary capillary network in pars distalis.
• Carries neuropeptides from median eminence to adenohypophysis to stimulate
or inhibit hormone release by the endocrine cells there.
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• 1- Adenohypophysis: develops from part of the
roof of the mouth called hypophyseal (Rathke's)
pouch (oral ectoderm) and later separate.
• 2- Neurohypophysis: develops from neural
ectoderm, a bud growing down from the
diencephalon forming infundibulum still attached
to hypothalamus.
Origin of pituitary gland:
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Low magnification – the entire Pituitary Gland
Posterior Pituitary Pars Intermedia Anterior Pituitary
Pars
Tuberalis
Pituitary
Stalk
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Histology of pituitary gland:
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Pituitary
gland
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Adenohypophysis (Anterior Pituitary)
1. Pars tuberalis
2. Pars intermedia
3. Pars distalis
Anterior Pituitary
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Adenohypophysis (Anterior Pituitary)
• Forms 75% of mass of hypophysis.
• Covered by a fibrous capsule.
• Composed of irregular cords of
parenchymal cells separated by
fenestrated capillaries.
Parenchymal cells:
1- Chromophobes: 50%, are stem
cells, have no affinity for stains.
2- Chromophils: 50% , have affinity for
stains, are 2 types:
A) Acidophils (stain with acid dyes
as eosin).
B) Basophils (stain with basic dyes
as HX).
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1. Acidophils
• stain with acid dyes as eosin.
• small in size
• large in number
• at center of pars distalis
• contains acidophilic granules.
• include the somatotropic and
mammotropic cells.
2. Basophils
• stain with basic dyes as HX.
• large in size
• few in number
• at periphery of pars distalis
• contains basophilic granules.
• include gonadotropic, corticotropic,
and thyrotropic cells.
Cells of Pars distalis
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High mag of the Anterior Pituitary – note eosinophilic and basophilic cells
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Pars distalis
(Anterior)
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Pars intermedia
• Thin part between pars distalis &
nervosa.
• Secrete (MSH) which increase
melanocyte activity.
Composed of:
• Basophils
• Chromophobes
• Colloid-filled cysts (follicles), named
(Rathke's cyst), are the remaining of
Rathke’s pouch during development.
• Blood capillaries.
Cells of Pars intermedia
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Cells of Pars intermedia
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Pars tuberalis
• Funnel-shaped superior extension of
pars distalis.
• surrounding the infundibulum
• highly vascularized.
• cells cuboidal arranged in longitudinal
cords.
• Secrete gonadotrophins [FSH & LH]
Pars tuberalis
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Composed of:
1. Pars nervosa: the largest part.
2. Infundibulum (neural stalk) :
the smallest part. Composed of:
stem & Median eminence.
NEUROHYPOPHYSIS (posterior lobe)
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Pars nervosa
• Stained Pale in Hx & E sections.
• Contains no secretory cells.
Composed of:
1- Nerve fibers: axons.
2- Supportive cells: pituicytes are
Similar to neuroglial cells, highly
branched.
3- Herring bodies: accumulations of
neuro-secretion, hormones are
temporarily stored.
4- Wide fenestrated blood capillaries.
NEUROHYPOPHYSIS (posterior lobe)
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PARS NERVOSA
(Posterior)
• pituicytes (P)
• neurosecretory
(Herring) bodies
(NB)
• capillaries (C)
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High mag of the Posterior Pituitary – neurons, capillaries, and pituicytes
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High mag of the Posterior Pituitary – note Herring Bodies (arrow)
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MEDICAL APPLICATIONs
1) Benign pituitary adenomas
produce excessive numbers of functional acidophils
or basophils.
2) Gigantism Gigantism is a rare condition that
causes abnormal growth in children, occurring in
children before closure of the long bones’
epiphyseal plates, change is notable in height.
involving increasing level of somatotropin growth
hormone, due to abnormal tumor growth of pit.
gland.
3) Acromegaly in adults, enlargment of hands, feet,
jaws, forhead, nose, involving increasing level of
growth hormone, due to abnormal tumor growth of
pit. Gland, after closure of the long bones’
epiphyseal plates.
4) Dwarfism – hyposecretion in children.
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END OF LECTURE 1
Thank you
DR.HANA ABUSAIDA, HISTOLOGY
DEPARTMENT, TRIPOLI UNIVERSITY
41

ENDOCRINE SYSTEM
Dr. Hana Abusaida
Tripoli University
2018-2019
Lecture 2
THYROID GLAND
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Thyroid Gland
Overview
• Located in the cervical region, anterior to the
larynx. Surrounding trachea.
• Bilobed united by an isthmus, butterfly-
shaped
• highly vascular
• Originates from endoderm.
Synthesizes:
1. Thyroxine.
2. Calcitonin.
Controlled by:
–Thyroid-stimulating hormone (TSH)
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Thyroid Gland Histology
Stroma
• Capsule & Septa (C.T) extend
into the parenchyma, dividing it
into lobules.
• very well vascularized with
fenestrated capillaries closely
surrounding the follicles for
transfer of released hormone to
the blood.
Parenchyma
• millions of cuboidal epithelial
cells thyroid follicles (Structural &
functional units ).
Capsule
Septa
lobule
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Thyroid follicles
• Is the Structural & functional units of
thyroid gland.
Each follicle composed of:
• Epithelium ranges from squamous to
low columnar.
• Central lumen filled with a gelatinous
substance called colloid .
Colloid
• Contains glycoprotein thyroglobulin
(660 kDa), the precursor for the active
thyroid hormone ( thyroxin ).
• Storage of thyroid hormone.
Thyroid Gland structure
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Thyroid Gland histology
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Types of cells
1. follicular cells:
– Called Thyrocytes
– squamous to low columnar
Size varying with activity;
• hyperactive cells are simple columnar,
• while inactive cells are simple squamous.
– Synthesize: T4 & T3
2. Parafollicular or
– Called C or (clear cells)
– Synthesize calcitonin
Functions of follicular cells
Synthesise thyroxine (tetra-iodothyronine or T4 ) and
tri-iodothyronine (T3 Hormone), which are important
for: growth, cell differentiation, and the control of
metabolic rate.
Sufficient hormone stored in colloid follicles to supply
the body for up to three months.
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Types of cells
1. follicular cells (Thyrocytes)
• squamous to low columnar .
• with few short microvilli.
• apical junctional complexes
• rest on a basal lamina
Nucleus : round and central.
Cytoplasm:
- rich in RER, supranuclear, Golgi,
apical secretory vesicles,
mitochondria, lysosomes.
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Types of cells
2. Parafollicular or C (clear cells)
• Found inside the basal lamina of the follicular
epithelium or as isolated clusters between
follicles, derived from neural crest cells.
Characters:
larger, rounded, pale staining cells with central
rounded nuclei.
• Smaller amount of RER, large Golgi
complexes, and numerous small granules
containing calcitonin hormone.
C cells
Functions of parafollicular cells
• Secrete calcitonin hormone which is
importance for:
•Inhibits Ca2+ absorption by the intestines
Inhibits osteoclast activity in bones
Stimulates osteoblastic activity in bones.
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Thyroid gland
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Thyroid gland
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Thyroid gland
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MEDICAL APPLICATIONs
myxedema
Goiter
Graves
Hyperthyroidism,
overactive thyroid, abnormally high level of
thyroid hormone in the bloodstream,
1- Goiter: neck swelling (goiter). Endemic
Hyperthyroidism
2- Graves' disease: (Hyperthyroidism
+exophthalmos).
Hypothyroidism,
underactive thyroid, is a condition where the
thyroid gland does not create enough thyroid
hormone
1. Myxedema disease, (results in swelling and
dryness of the skin especially around the nose
and lips, dulling of the senses and difficulty in
speech)
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END OF LECTURE 2
Thank you
DR.HANA ABUSAIDA, HISTOLOGY
DEPARTMENT, TRIPOLI UNIVERSITY
54

ENDOCRINE SYSTEM
Dr. Hana Abusaida
Tripoli University
2018-2019
Lecture 3
• PARATHYROID
• PINEAL GLANDS
55

Parathyroid Gland
Overview
• 4 small ovoid glands.
• Located behind thyroid gland, one at each end
of upper and lower poles.
• Small ,yellowish brown& ovoid glands.
• derived from the pharyngeal pouches
endoderm and migrate to the developing
parathyroid
• Synthesizes:
– PTH: major regulator of blood calcium levels.
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Parathyroid Gland histology
Stroma,
– Capsule forms septa inside
parenchyma.
– Highly vascularized, lymphatics and
nerves.
– Reticular fibers.
Parenchyma
– 2 types of cells:
1. Chief cells.
2. Oxyphil cells.
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Parathyroid Gland histology
 With increasing age many secretory cells are replaced with adipocytes,
which may constitute more than 50% of the gland in older people.
 Older parathyroid glands also show increasing numbers of nonfunctional
Oxyphil cells.
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1- Chief (principal) cells:
• Most numerous cells.
• Small, polygonal, central round nuclei
• Pale-staining,
• Slightly acidophilic cytoplasm.
• With secretory granules containing the (PTH),
• Synthesise parathyroid hormone.
• PTH is the major regulator of blood calcium levels.
Parathyroid gland cells
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Function of Chief cells
 Increases blood calcium level by:
 increasing bone resorption by osteoclasts so release of Ca2+, increasing the
concentration of Ca2+ in the blood, which suppresses parathyroid hormone
production.
 Calcitonin from the thyroid gland inhibits osteoclast activity, lowering the
blood Ca2.
 Increasing reabsorption of calcium by kidneys.
 Increasing intestinal absorption of calcium by stimulating the synthesis of
vitamin D.
 Reduces blood phosphate levels.
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2- Oxyphil cells:
• Few in number but increase in number
with age.
• Large in size, present singly or in
clusters.
• Nuclei is small dense.
• Acidophilic cytoplasm,
• Abnormally shaped mitochondria,
• Small Golgi & few RER.
• Glycogen, lipid droplets and secretory
granules.
Function of Oxyphil cells
• As immature chief cells.
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oxyphil cells
Chief (principal) cells
septa
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Parathyroid Gland – note small dark staining chief cells and larger, eosinophilic
oxyphil cells
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MEDICAL APPLICATION
• Hypoparathyroidism
–Is a decreased secretion or activity of parathyroid hormone
(PTH), leads to decreased blood levels of calcium
(hypocalcemia) and increased levels of blood phosphorus
(hyperphosphatemia).
–Bones : more mineralized. denser
–striated muscle : abnormal contractions
• Hyperparathyroidism”
–Stimulates osteoclast number and
activity,
–leading to blood phosphate are decreased and hypercalcemia
– weakness and fatigue, depression, bone pain, muscle
soreness decreased
appetite, nausea and vomiting, constipation, polyuria, polydi
psia,, kidney stones and osteoporosis .
64

Pineal Gland
Overview
Pineal Gland or pineal body
• known as the epiphysis cerebri,
• regulates the daily rhythms of bodily
activities.
• A small, pine cone-shaped organ,
• develops from neuroectoderm in the
posterior wall of the third ventricle
• remains attached to the brain by a short
stalk.
• Regulates the daily rhythms of bodily
activities, responsible for regulating sleep
cycles.
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Pineal Gland histology
A. Stroma
• C.T. of pia mater.
• Septa containing blood vessels and
unmyelinated sympathetic nerve fibers.
A. Parenchyma, contains 2 types of cells:
1. Pinealocytes.
 Modified neurons.
 Slightly basophilic cytoplasm.
 large, irregular euchromatic nuclei and
nucleoli.
 secretory vesicles.
 many mitochondria.
2- Interstitial glial cells
• 5% of gland cells, between pinealocytes.
• Resemble astrocytes.
• have elongated nuclei, long cytoplasmic processes.
• deeply stained nuclei & more basophilic cytoplasm.
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Pineal Gland
Function:
Produce melatonin (Hormone of Darkness), is
promoted by darkness and inhibited by
daylight, resulting diurnal fluctuation in blood
melatonin levels induces rhythmic changes in the
activity of the hypothalamus, pituitary gland, and
other endocrine tissues.
Corpora arenacea (brain sand)
 Presence of calcified structures called Corpora
arenacea or brain sand.
 Composed of calcium and magnesium salts.
• Appear during childhood and gradually increase
in number and size with age.
• Light detected within the retinas and transmitted
to the pineal via the retinohypothalamic tract
 Unknown function.
 becomes increasingly visible on X-rays over time.
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Pineal Gland
N – Neuroglia
P –Pinealocytes
S – Brain Sand
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Pineal Gland
Pineal gland with calcifications
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END OF LECTURE 3
Thank you
DR.HANA ABUSAIDA, HISTOLOGY DEPARTMENT, TRIPOLI UNIVERSITY
70

ENDOCRINE SYSTEM
Dr. Hana Abusaida
Tripoli University
2018-2019
Lecture 4
• ADRENAL GLANDS
• PANCREATIC ISLETS
71

Adrenal glands
• Adrenal (suprarenal) glands
• Half-moon shape,
• about 4 to 6 cm long, 1 to 2 cm
wide, and 4 to 6 mm thick in
adults.
• weight and size vary with the
age and physiologic condition.
• Produce corticosteroids.
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Adrenal glands hormones
Corticosteroids
• Are classified as:
1- Glucocorticoids , such as corticosterone & cortisol, have anti-
inflammatory which suppress inflammation and immunity and assist in
the breakdown of fats, carbohydrates, and proteins,
2- Mineralocorticoids , such as aldosterone, regulate the balance of
salt and water in the body.
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ADRENAL GLANDS histology
Structure:
I. Stroma
– Capsule of dense C.T. sends thin septa
to the interior of the gland as
trabeculae.
– Network of reticular fibers. support the
secretory cells
II. Parenchyma
– Adrenal cortex.
– Adrenal medulla.
•Cortex origin from mesoderm.
•Medulla consists of cells derived from the neural crest.
Embryologically, histologically and functionally cortex and medulla are
different regions, can be considered two organs, that become united during
embryonic development.
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ADRENAL GLANDS
Medulla
Cortex
Cortex
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ADRENAL GLANDS
Adrenal Cortex
medulla
Capsule
Zona glomerulosa
Zona fasciculata
Zona reticularis
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ADRENAL GLANDS
Blood Supply of adrenal glands :
1.Superior suprarenal arteries from inferior phrenic.
2.Middle suprarenal arteries from aorta.
3.Inferior suprarenal arteries from renal artery.
These arteries plexues forming:
• Arteries supply the capsule,
• Cortical arterioles, which branch as capillaries
and sinusoids to regulate the cortex, join the:
• Medullary arterioles, form a network of
fenestrated sinusoids in medulla.
Adrenal medulla has a dual blood supply with both:
1.arterial -medullary arterioles
2.venous -capillaries of the cortex (from left
suprarenal vein).
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1- ADRENAL CORTEX
Cells have characteristic features of steroid-secreting cells:
Adrenal cortex present in 3 layers:
1. Zona glomerulosa : about 15% (outer narrow zone).
2. Zona fasciculata: 65- 80% (middle thick zone).
3. Zona reticularis: about 10% (inner narrow zone).
78

ADRENAL CORTEX
I. Adrenal Cortex
3 concentric zones
in which the cords of epithelial
steroid-producing cells are
arranged :
1. Zona glomerulosa : about 15%
(outer narrow zone).
2. Zona fasciculata: 65- 80% (middle
thick zone).
3. Zona reticularis: about 10%
(inner narrow zone).
79

ADRENAL CORTEX
Zona glomerulosa
Zona fasciculata
Zona reticularis
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ADRENAL CORTEX
I. Layers of Adrenal Cortex
1- Zona glomerulosa
Cells:
• arched cords (follicle like structure)
• columnar or pyramidal cells
• closely packed.
• surrounded by blood capillaries.
• Nuclei: round, dense.
Cytoplasm:
• Acidophilic, contain lipid droplets.
Functions
• Secrete mineralocorticoid
hormones mainly aldosterone.
• Controls water and NA+ balance.
82

ADRENAL CORTEX
I. Adrenal Cortex
2- Zona Fasciculata : 65% to 80%
Cells:
• Spongiocytes: polyhedral cells,
• arranged in long straight cords
• nuclei: large, rounded and lightly stained
• Cytoplasm:
• acidophilic, contains many lipid droplets
• pale, foamy and vacuolated.
Functions
•Secrete glucocorticoid hormones ( cortisol
and corticosterone).
•Cortisol regulate carbohydrates, fat and
protein metabolism.
•Cortisol suppress immune response by
decreasing number of circulating
lymphocytes.
83

ADRENAL CORTEX
I. Adrenal Cortex
3- Zona reticularis
Cells:
• arranged in irregular cords forming network
with wide capillaries.
• dark stained due to fewer lipid droplets and
many lipofuscin pigments (in older)
• Cytoplasm:
• deeply acidophilic.
Functions:
•Produce cortisol,
•Secrete the weak androgen
dehydroepiandrosterone (DHEA) which is
converted to testosterone.
•Controlled by ACTH of pars distalis.
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1. Zona Glomerulosa
(clumps, and follicle like
structures
2. Zona Fasciculata
(cords of spongiocytes)
ADRENAL CORTEX
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2. Zona
Fasciculata
cords of
spongiocytes
3. Zona
Reticularis
darker staining
cells
ADRENAL CORTEX
86

ADRENAL CORTEX
Adrenal Cortex
medulla
Capsule
Zona glomerulosa
Zona fasciculata
Zona reticularis
87

ADRENAL CORTEX
I. Adrenal Cortex
Hormones and control
Zona glomerulosa
Zona fasciculata
Zona reticularis
glucocorticoid
mineralocorticoid
aldosterone
androgen
cortisol
angiotensin II
ACTH
ACTH
ACTH
Hormones
glucocorticoid
88

MEDICAL APPLICATION
Addison disease: (adrenal cortical insufficiency)
• usually autoimmune in origin,
• causes degeneration in any layer of adrenal cortex,
• concomitant loss of glucocorticoids, mineralocorticoids,
or androgen production.
• chronic, fatigue, muscle weakness, loss of appetite,
weight loss
• Cushing syndrome: excessive glucocorticoids, causes
increase ACTH in pituetry.
• Conn syndrome: excessive aldosterone .
• feedback mechanism :
– Patient. treated with corticoids , if stop taking hormones
suddenly, secretion of ACTH in these patients is inhibited,
and thus the cortex will stop produce corticoids, causing
severe drops in the levels of sodium and potassium
Cushing
Cushing
Addison
89

ADRENAL GLANDS
I. Fetal adrenal Cortex
 Adrenal gland is larger than that of the adult
 produces up to 200 mg of corticosteroids per day, twice that of an adult.
 provisional cortex, a layer comprising 80% of the gland, present
between cortex and medulla.
 Thick cortex.
 The principal function is secretion of sulfated DHEA
(dehydroepiandrosterone) which is a pro-hormone converted in the
placenta to active estrogens and androgens.
 important part of a fetoplacental unit which affects endocrine systems
during pregnancy.
90

ADRENAL GLANDS
II. Adrenal Medulla
Cells:
• known as chromaffin cells.
•large, pale-staining polyhedral
cells arranged in cords or clumps.
•modified neurons with no axons
and dendrites, resemble
sympathetic neurons
• Occupies center of adrenal gland, surrounded by
adrenal cortex.
• Medulla store the hormones in granules.
• Shares an embryological origin with the sympathetic
nervous system
91

ADRENAL MEDULLA
Cytoplasm:
• basophilic.
• numerous mitochondria.
• well developed Golgi complex.
• some RER .
• many electron-dense granules for
hormone storage and secretion.
Function:
Secretes catecholamines, most is
epinephrine ( only made in the adrenal
medulla), Norepinephrine , dopamine
norepinephrine-secreting cells
epinephrine-secreting cells
92

ADRENAL MEDULLA
Types of chromaffin cells
• Epinephrine (adrenalin)
secreting cells:
– With small granules.
– less electron dense.
– contents fill the granules.
• Norepinephrine (nor-
adrenalin) secreting cells:
– found in paraganglia (collections of
catecholamine-secreting cells
adjacent to the autonomic ganglia).
– large granules.
– more electron dense.
93

ADRENAL MEDULLA
Epinephrine and norepinephrine
• During normal activity, the adrenal medulla secretes small
quantities of the hormones
• Released large quantities during:
– fasting
– hypoglycemia,
– stress,
• Causes:
– vasoconstriction,
– increased blood pressure,
– changes in heart rate,
– elevated blood glucose.
94

MEDICAL APPLICATION
II. Adrenal Medulla
• Pheochromocytoma,
– disorder of the adrenal medull
– tumor of its cells that causes
hyperglycemia and transient
elevations of blood pressure.
95

Pancreas
Pancreas
 mixed gland
 The islets of the pancreas
produce hormones
 Insulin – from beta
cells,
 Glucagon – from alpha
cells,
 These hormones are
regulate blood sugar
homeostasis
97

PANCREATIC ISLETS
Pancreatic Islets (Islets of langerhans)
• The endocrine portion of
pancreas.
• Spherical or egg-shaped masses
of endocrine cells.
• More than one million islets in
human pancreas.
• More abundant in tail region of
pancrease.
• Origin from endoderm.
• Stains by routine stains or
trichrome stains.
• acidophilic or basophilic with
fine cytoplasmic granules.
98

PANCREATIC ISLETS
Histological structure
 Types of cells:
1. A cells (α cells)
2. B cells (β cells)
3. D cells (delta cells).
4. F cells or PP cells
 Blood capillaries
99

PANCREATIC ISLETS
Cells of pancreatic islets
Type Quantity Position Hormone function
A 20%
large in size
Peripheral Glucagon Increase blood glucose level
(glycogen  glucose)
B 70%
small in size
Central Insulin Decrease blood glucose level
(glucose  glycogen)
D <5%
small in size
Variable Somatostatin Inhibit release of other islet cell
hormones through local
paracrine action.
F Rare variable Pancreatic
polypeptide
Not well established
100

PANCREATIC ISLETS
pancreatic islets
Alpha
Cells
101

PANCREATIC ISLETS
Cells of pancreatic islets
Acinar cells (secrete enzymes)
Islet of Langerhans (secretes insulin and glucagon)
102

PANCREATIC ISLETS
Acinar cells
Islet of Langerhans
103

PANCREATIC ISLETS
pancreatic islets
Acinar cells
Islet of Langerhans
104

PANCREATIC ISLETS
pancreatic islets
Islet of Langerhans
105

MEDICAL APPLICATION
• Insulin-dependent
– type 1 diabetes (juvenile diabetes)
– results from partial or total autoimmune destruction of beta
cells and lack of insulin.
• Insulin-independent diabetes
– type 2 diabetes
– occurs later in life, results from a failure of cells to respond
to insulin, and is frequently associated with obesity.
106

END OF ENDOCRINE LECTURES
Thank you
DR.HANA ABUSAIDA, HISTOLOGY DEPARTMENT, TRIPOLI UNIVERSITY
‫وقاتل‬ ‫الحلم‬ ‫ناصية‬ ‫على‬ ‫قف‬
107

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