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Morphology of
Major Endocrine Glands
Amornpun Sereemaspun M.D., Ph.D.
Depicha Jindatip Ph.D.
Department of Anatomy, Faculty of Medicine
Chulalongkorn University
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Topics to be discussed and studied
Endocrine Gland
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Organization
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Clinical
Relevance
Microscopic
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Gross
Structure
Function
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Structure
Cell
Structure/Fn.
Intracellular
organelles
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PART I :
Endocrine & Concept of
Cell Communications
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Intercellular communication
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• Communication between cells
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– Direct electrical coupling
• Synaptic or anatomical junction
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– Chemical substances
• hormones or neurotransmitters
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Homeostasis & Endocrine
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Homeostasis
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(physiological state in which the physical and chemical conditions of
the internal environment are being maintained)
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Most organ systems
contribute to homeostasis
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Nervous
System
Endocrine
System
Electrical
Means of
communication (±chemical)
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Chemical
reacts slower
continue ~ weeks
adapts quickly and
response declines
more persistent
responses
targeted and
specific
widespread effects
on many organs
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Adaptation to
long-term
stimuli
Area of effect
reacts faster
stops quicker
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Speed and
persistence of
response
Endocrine
Systems
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Nervous
Systems
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Endocrine vs. Nervous System
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Vertebrate Hormones Functions
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Control …
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Chemical Hormone Groups
• secreted by adrenal
cortex, ovary, testis
• molting hormone of
insects
Steroid
hormones
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Fatty acid
derivative
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• Prostaglandins
• juvenile hormone
of insects
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Amino
acid
derivatives
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• thyroid hormones
• epinephrine
Peptides
and
proteins
• antidiuretic hormone
(ADH), glucagon
(peptide hormones)
• insulin (protein)
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Components of Endocrine System
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• Secreting cell
• Hormone
– chemical messenger secreted into bloodstream,
stimulates response in another tissue or organ
• Target cells : have receptors for hormone
Endocrine system
includes hormone producing cells in organs
e.g. brain, heart and GI
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Types of Endocrine Signaling
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Part II :
Hypothalamus & Pituitary gland
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Thalamus
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Anatomy of Hypothalamus
Tuber cinereum
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Infundibular stalk
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Median eminence
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Anatomy of Hypothalamus:
Boundaries
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Medial boundary = 3rd ventricle
Lateral boundary - indistinct
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Hypothalamic Nuclei
Nucleus = groups of neurons in hypothalamus
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Hypothalamus : Functions
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The Hypothalamus: Hormones
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• Hormones – control secretion of hormones in the anterior pituitary
– Releasing hormones (factors)
– Inhibitory hormones (factors)
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ADH and Oxytocin
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Hypothalamus and Pituitary Gland
Main source of releasing/inhibitory
factors
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ACTH
TSH
FSH, LH
GH
prolactin
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ADH/oxytocin
Releasing factors: CRH, TRH, GnRH, GHRH
Inhibiting factors: somatostatin, dopamine
ADH/oxytocin
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Pituitary Gland
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(Hypophysis, Master gl., Neuroendocrine gl.)
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Pituitary: Gross Anatomy
• 0.5 – 1 g in weight
• In sella turcica
(bony cavity at the base of the brain)
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• 1 cm in diameter
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• Connected to the hypothalamus via pituitary stalk
(infundibulum)
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Mamillary body
Optic chiasma
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Pituitary stalk
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Pituitary gland in sella turcica
Sphenoidal air sinus
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Embryonic Development of Pituitary
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Adenohypophysis : Neuroectoderm
Neurohypophysis : Oral epithelium
Adenohypophysis
Pituitary Subdivision
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Terminology based on
embryonic origin
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Pituitary Subdivisions
Pars distalis
Clinical Terminology
Anterior lobe
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Pars tuberalis
Neurohypophysis
Pars intermedia
Pars nervosa
Infundibulum
Posterior lobe
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Adenohypophysis
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Pars tuberalis
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Pars distalis
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Pars intermediate
General Cell
Types
Diameter of
secretory
granules
(nm)
Somatotrope
hGH
Acidophilic
300-400
Mammotrope
Prolactin
Acidophilic
200
ACTH
Basophilic
400-550
TSH
Basophilic
120-200
FSH, LH
Basophilic
250-400
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Thyrotrope
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Corticotrope
Gonadotrope
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Hormones
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Specific Cell
Types
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Cells in pars distalis
Histology: Pars Distalis
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 very cellular, arranged in clumps and cords between sinusoids
Chromophils
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Somatotropes (GH)
Mammotropes (Prl)
Basophils (blue/black)
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Acidophils (red/pink)
Chromophobes
(orange/gray)
Thyrotropes (TSH)
smallest cell type
Corticotropes (ACTH)
few granules
Gonadotropes (FSH, LH)
unstained cytoplasm
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ACTH immunoperoxidase stain
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Prolactin immunoperoxidase stain
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Pituitary immunohistology
Human growth hormone (HGH) immunoperoxidase stain
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Extension of the hypothalamus
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– pars nervosa
– pituitary stalk
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– median emminence
Axons from supraoptic nuclei
– vasopressin (ADH)
Axons from paraventricular nuclei
– oxytocin
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Neurohypophysis
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Neurohypophysis histology
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• Axons
:
unmyelinated
• Pituicytes
:
as glia cell
• Fenestrated capillaries : from inferior hypophyseal a.
Nerve fibers in relation to capillaries and pituicytes
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Neurohypophysis : H&E Histology
Axon
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- Herring bodies – neurosecretory granules
accumulated close proximity to
axon terminal
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Herring body
(Immunohistochemical staining of ADH)
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Herring body
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Pituitary Hormones & Effects
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Growth Hormone (hGH)
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Prolactin (PRL)
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Gonadotropins (LH, FSH)
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Thyroid stimulating hormone
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Adrenocorticotropic Hormone
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Hypothalamic-hypophysial vessels
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Fenestrated capillaries in pituitary gland
Transmission electron microscope
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Scanning electron microscope
Capillary
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E: Endothelial cells
H: Hormone producing cells
P: Pericytes
F: Fenestration
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PITUITARY ADENOMA
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Hypophysectomy
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Transsphenoidal Approach
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PART III : Pineal gland
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Cone-shaped, 5-8 mm. in length
Connected to roof of 3rd ventricle by a stalk
No direct nerve connection with brain
Function is regulated by numerous postganglionic
sympathetic nerves from the superior cervical ganglion
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–
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Pineal Gland : Anatomy
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Embryonic Development of Pineal gland
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- Capsule = Pia mater
- Cells Parenchyma
•Pinealocyte
–Round shape, slightly stained
cytoplasm
–Nuclei relatively large with
prominent nucleoli
–2 or more processess with bulb
ending (not demonstrated with
H&E)
–organized into cords/clusters
•Glial-like interstitial cell
–surround and mingle with the
pinealocytes making up peculiar
aggregates
- Stroma
•CNT, fenestrated vessels, nerves
•Corpora arenacea
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Pineal Histology
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Brain Sand (Corpora Arenacea)
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• Adult pineal contain lamellated, calcified,
basophilic glycoprotein
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Radiologic marker
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Pineal gland: Histology
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Pineal Histology : EM
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Pineal Gland : Melatonin
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• Peak secretion 1-5 yr. olds, by puberty 75% lower
• Produces serotonin by day, converts it to melatonin at
night
• May regulate timing of puberty/ circadian rhythms
(biological clock)
• During sleep, plasma levels of melatonin increase &
then decrease before awakening
• Clinical Use : insomnia, jet lag
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PART IV : Thyroid
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• Inferior to larynx, anterior and
lateral sides of trachea
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Thyroid Gland : Gross Anatomy
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• Functions
- Produces - thyroid hormone
- calcitonin
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Thyroid Gland : Gross Anatomy
• Consists of
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1. Lateral lobes
3. Pyramidal lobe
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(remnant of development)
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Thyroid Gland : Gross Anatomy
• Venous Drainage
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- Superior thyroid artery
- Inferior thyroid artery
- Thyroidea ima artery (10%)
branch from brachiocephalic
trunk
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• Arterial Supply
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- Superior and middle thyroid v.
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to internal jugular v.
- Inferior thyroid v. to
brachiocephalic v.
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• Normal size : 15-30 gram
• Abnormal size
(reported by weight)
1. Diffused enlargement
2. Thyroid nodule
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Thyroid Gland : Gross Anatomy
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• Moved with swallowing
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Thyroid Gland : Gross Anatomy
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– by anterior and posterior suspensory ligament of
thyroid gland (posterior = ligament of Berry)
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Fibrous CNT
Loose CNT, Fenestrated capillary
Thyroid follicles, Parafollicular cells
Follicular cells
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Capsule:
Stroma:
Parenchyma:
Follicles :
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Thyroid : H&E Histology
Colloids : Thyroglobulin
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Thyroid Gland : Parenchyma
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Follicular Cells
• Acini form
• Lumen with colloid
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• C (Calcitonin ) cells
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Parafollicular Cells
• Round shape/round nucleus
• Pale cytoplasm
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• Simple cuboidal epithelium
• Small cytoplasmic granule
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C cell : H&E, IHC and EM
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Thyroid Functions
• Thyroid follicles
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– filled with colloid and lined with simple cuboidal epith. (follicular cells)
that secretes 2 hormones, T3+T4
– Thyroid hormone
•  body’s metabolic rate and O2 consumption
• calorigenic effect -  heat production
•  heart rate and contraction strength
•  respiratory rate
• stimulates appetite and breakdown CHO, lipids & proteins
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Calcitonin Functions
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• C (calcitonin or parafollicular) cells
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– produce calcitonin that  blood Ca+2, promotes Ca+2
deposition and bone formation especially in children
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Thyroid : Hormone Synthesis
• More potent
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• Mostly bind with TBG
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• Less potent
• Short halflife (18 hr)
• Produced 20-30 µg/d
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– Peripheral conversion from
T4
– Follicular cell
T4 = Thyroxine
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T3 = Triiodothyronine
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Thyroid Hormones
• Long halflife (5-7 days)
• Mostly bind with TBG
• Produced 80-100 µg/d
– Follicular cell
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Hashimoto's Thyroiditis
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Thyroid : Follicular Adenoma
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Thyroid : Grave’s Disease
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exophthalmos
pretibial myxedema
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Thyroid : Grave’s Disease
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Thyroid : Grave’s Disease
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Thyroid : Medullary carcinoma
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“C” Cells Cancer
Related with Multiple Endocrine Neoplasia (MEN)
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Thyroid : Medullary carcinoma
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“C” Cells Cancer
Related with Multiple Endocrine Neoplasia (MEN)
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PART V : Parathyroid
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• 10% of individual have 2-3 glands
• Each weighs 35-40 g
• Landmark : Fatty Mass
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Parathyroid Glands Anatomy
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Parathyroid Histology : H&E
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Parathyroid Histology : H&E
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Parathyroid Histology : H&E
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Parathyroid Histology : H&E
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Parathyroid Gland : Parenchyma
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• Smaller, rather basophilic
• Larger cells, eosinophilic
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• Unknown function
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• Arranged in small cluster
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Oxyphil Cells
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• Predominate and contain
cytoplasmic granule
• Synthesize parathyroid hormone
(PTH)
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Chief (Principal) Cells
Parathyroid Gland : Stroma
• Fat, increase with age up to 25 years, occupied 30% of adult gland
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Parathyriod Hormone: Functions
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Parathyriod v.s. Calcitonin
• Overactive neuron, resulting in Tetany
• Too low Calcium
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Hypo PTH
• Moderate : impaired muscle/kidney
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Hyper PTH
• Severe : Bone destruction
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Parathyroid Homeostatic Imbalances
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PART VI : Adrenal Glands
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ADRENAL (SUPRARENAL) GLANDS
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Adrenal Gland Anatomy
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• Cortex
– Corticosteroid
– glandular
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• Medulla
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– Catecholamines
– neurohormonal
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• Epinephrine
• Norepinephrine
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Cortical Adrenal Zones
(L. Glomus=ball)
thin
outermost zone
15% of cortical vol.
• zona fasiculata
(L. Fascis=bundle)
thick
middle zone
80% of cortical vol.
(L. rete=net)
thin
inner zone
5-7% of cortical vol.
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• zona glomerulosa
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• zona reticularis
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Cortical Adrenal Histology:
Low magnification
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Adrenal Gland Histology
reticularis
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fasciculata
capsule
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medulla
glomerulosa
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Zona glomerulosa
Renin-angiotensin
system (RAS)
Aldosterone
Na+ resorption
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• columnar in shape and are arranged in irregular cords
• cells adjacent to the capsule are arranged in regular "arcades".
• cells have less cytoplasm than the Zona Fasciculata, so appears as a
darker layer (at lower powers)
• boundaries between zones are indistinct.
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Adrenal gland and RAAS system
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• Polyhedral in shape
• Light appearance (abundant lipid droplets)
• Arranged in long straight columns
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Zona fasiculata
CRF
ACTH
glucocorticoids
Sex steroids
Metabolic control
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Zona reticularis
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• Cells are noticeably smaller & darker than ZF cells
• Arranged in an irregular network of branching cords and clumps
• Anastomose with one another, some cells contain lipofuscin
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Androgens
(esp.DHEA)
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ACTH
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glucocorticoids
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Cortical Adrenal Cells : EM
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• Features of steroid-secreting cells
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– Abundant smooth endoplasmic reticulum
– Mitochondria with tubular cristae in the zona
fasciculata and zona reticularis, shelf-like cristae in
the zona glomerulosa
– Numerous lipid droplets
– Secretion is by diffusion, with no hormone storage
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Adrenal Medulla
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• columnar in shape and rather basophilic
• pale-staining granular cytoplasm
• arranged in clusters,
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Chromaffin cell
• mixed with sinusoidal capillaries /preganglionic sympathetic fiber
Ganglion cells
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• round or polygonal with prominent nuclei
• arranged in clusters
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Medullary Hormones
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• Innervated by preganglionic sympathetic fibers
– consists of modified neurons called chromaffin cells
– stimulation causes release of (nor-epinephrine)
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Adrenal Medulla : EM
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TEM (magnification = 8400x)
Epinephrine-Secreting cells (ESC)
- 75%approximately
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- small homogenous granule
Norepinephrine-Secreting cells (NSC)
- 25% approximately
- dense-core, larger granules
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Hormone related to adrenal gland
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– Superior adrenal a.
– Middle adrenal a.
– Inferior adrenal a.
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• via the 3 suprarenal arteries
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Vasculature of the adrenal gland
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0) Capsular capillaries
1) Cortical sinusoidal capillaries
2) Medullary capillaries
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• Intra-adrenal arterial subdivisions
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Vasculature of the adrenal gland (2)
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2
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Addison’s
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Adrenal Cortex Disorder
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Normal
ACTH
hypersecretion
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• Hyposecretion leads to
Addison’s Disease
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– Deficits in glucocorticoids
and mineralcorticoids
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– ACTH-releasing tumors or
side effects of corticoid
drugs.
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• Hypersecretion leads to
Cushing’s disease
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Adrenal Cortex Imbalances
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Adrenal medulla tumor :
Pheochromocytoma
• Tumor arising most commonly from the adrenal gland
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• Cause headaches, sweating, rapid rise and fall in blood pressure,
fast heartbeat , etc.
• From making excessive adrenaline (catecholamine)
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PART VII :
Other endocrine organs
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Exocrine 98% produces digestive enzymes
Endocrine pancreas (Islets of Langerhans) (1-2%)
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• cells: glucagon (15-20%)
• cells: insulin (60-80%)
• cells: somatostatin (less than 5%)
•F cells: pancreatic polypeptide (PP)
•Etc: motilin, serotonin, substance P, Vasoactive intestinal peptide (VIP)
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•
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Pancreas
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Thymus
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Gonads
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Ovary
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Testis
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Other Hormones
Organs
Hormones
Heart
Atrial Natriuretic Peptide (ANP)
Skin
Cholecalciferol
Adipose Tissue
Leptin
Kidney
Erythopoietin
Gastrointestinal
Digestive hormones
Liver
Albumin
Liver hormones