Histology of Endocrine Organs Flashcards
Major Glands and Organs associated with Endocrine System
LO1
- hypothalamus
- pineal
- pituitary
- thyroid
- parathyroid glands
- adrenal glands
- pancreas
- Gonads
Why is the blood supply to endocrine organs so robust?
LO1
hormones are distributed throughout the body by cardiovascular system
- communication is much slower but effects on target cell.organs are of longer duration
Location of hypothalamus
LO2
part of the brain located below the thalamus, behind the optic chiasma and surrounding the 3rd ventricle
Hypothalamus
- anatomical relationship with pituitary gland
LO2
above the pituitary gland
primary site where CNS controls endocrine functions via pituitary glands
Target Organs and cells the are directly targeted by the hypothalamus
LO2
- anterior pituitary glands ( releasing and inhibiting factors)
- Kidney and uterus (releasing antidiuretic hormone and oxytocin, in posterior pituitary)
- Adrenal medulla (sympathetic innervation)
Major lobes and parititions of the pituitary gland
- location
- nickname
LO3
aka Hypophysis
location: inferior to hypothalamus
- small, slightly oval gland house within hypophyseal (sella turcica) of sphenoid bone
- connected to hypothalamus by a thin stalk of tissue (infundibulum)
- partitioned structurally and functionally into anterior (adenohypophysis) and posterior (neurohypophysis) portions
Steroid Hormones
types of lipids derived from cholesterol
exm. estrogen , testosterone, cortisol
What controls hormonal release? (3)
- humoral stimuli
- neuronal stimuli
- hormonal stimuli
Humoral stimuli
release controlled by monitoring levels of ions and nutrients in blood and body fluids
exm. release of parathyorid hormone stimulated by low serum calcium levels
Neuronal Stimuli
release stimulated by nerve signals
exm. release of epinephrine from adrenal glands in response to a signal form sympathetic nerve fibers
Hormonal Stimuli
release caused by a hormone secreted into bloodstream by another endocrine organ or cell
exm. release of thyroid hormone stimulated by release of hormone, TSH from pituitary
Endocrine Gland Organization
Epitheloid cells (lacking free surface) arranged as cords/follicles and some as isolated individual cells
derived from epitheia
well- vascularized- vesels often have fenestrated endothelium
Indirect Targets of hypothalamus hormones
- Tropic (releasing/inhibitory) hormones
- hypothalamus releases hormones (tropic) that stimulate or inhibit release of other hormones from anterior pituitary - indirectly influences by stimulating secretion of hormones by anterior pituitary glands
- thyroid glands
- adrenal cortex
- mammary gland
- gonads- testes or ovaries
- bone and other organs
Microscope features of both anterior and posterior pituitary glands
LO4
- Pars distalis
- Pars Nervousa
- pars tuberalis
- pars intermedia
- cyst intermedia - remnants of lumen of Rathke’s pouch
Major cell types found within the anterior and posterior pituitary gland
- short description
LO4
- somatotropic cells
- secrete growth hormone (GH) - thyrotropic cells
- secrete thyroid stimulating hormone (TSH) regulating thyroid gland secretion - Corticotropic cells
- secrete adrenocorticotropic hormone (ACTH)- stimulate adrenal cortex to secrete stress-related hormones and mediate metabolism
- melanocyte-stimulating hormone (MSH) - stimulate melanocytes to produce melanin
- stimulate adrenal cortex to secrete stress-related hormones and mediate metabolism
- Gonadotropic cells
- secrete follicle-stimulating (FSH) and luteinizing hormone that act on the gonads - Mammotropic cells
- secrete prolactin that stimulates milk productions
Hypothalamic-hypophyseal portal system
- ANTERIOR PITUITARY
- what does it consist of
- steps
LO5
blood supply to ANTERIOR pituitary
Consist of primary capillary plexus, hypophyseal portal veins, and secondary capillary plexus
- When appropriately stimulated, hypothalamic neurons secrete releasing and inhibiting hormones into primary capillary plexus
- hypothalmic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in anterior pituitary
- In response to releasing hormones, the anterior pituitary secretes hormones into secondary capillary plexus. This in turn empties into the general circulation
Causes of gigantism and pituitary dwarfism
LO6
Gigantism
- excess production of GH due to tumor
- excessive bone growth, enlargement of extremities (acromegaly) and organs
Pituitary Dwarfs
- hyposecretion of GH
- normal body proportion but rarely 4 feet
Pineal Gland
- location
- microscopic organization
- basic functions
LO7
out pocketing of diencephalon’s roof of 3rd ventricle
flatten cone-shaped 3-5mm diameter
fxn: growth, development, and circadian rhythms
cover with pia mater
synthesizes melatonin and serotonin
Consists of:
- Pinealocytes
- Neuroglia
- Calcified granular material (brain sand) - calcium phosphate crystals located intercellular spaces showing up beginning early childhood
- important radiogenic marker ( secreted by pinealocytes)
Cell of Pars Distalis (anterior)
(4)
LO4
- Acidphils
- somatotroph- GH
- mammotrophs- prolactin - Basophils
- corticotrophs- ACTH
- thyrotrophs- TRH
- Gonadotrophs- FSH/ LH - Chromophobes- unknown function
- Sinusoidal fenestrated capillaries
Pars Intermidia
LO4
- between pars distalis and pars nervosa
- rudimentary in adults
- unknown function
- small basophils and colloid-filled follicles lined by cuboidal epithelium
- Frequently has cleft (remnant of lumen and Rathke’s pouch)
Pars Nervousa
LO4
continuous with median eminence of hypothalamus via infundibular stalk
- does not manufacture hormones, rather stores adn releases them from axon terminals
consists of:
- hypothalamic unmyelinated axons
- herring bodies- expanded axonal nerve terminals storing ADH/ oxytocin - Pituicytes (glia-like) supporting the nerve fibers
- Fenestrated capillaries
Pituitary Gland embryological origin
* supplement
from ECTODERM
Diverticulum-> diencephalon of neural tube-> infundibulum forms posterior and infundibular stalk and Rathke’s pouch forms rest of pituitary
Infundibulum
-portion
LO4
suspend pituitary gland from hypothalamus
- Neural portion (infundibular stalk) - part of neurohypohysis connecting pars nervosa and median eminence of hypothalamus
- unmyelinated axons ( nerve body in hypothalamus, terminals in pars nervosa) - Adenhypophysis portion- surrounding pars tuberalis enveloping the infundibular stalk. May for a partial or total collar
- consist of number cuboidal cells arranged in cords
Hypothalamo-hypophyseal tract
- Posterior Pituitary Gland
- hormones
- steps
LO5
Antidiuretic Hormone and Oxytocin
- Hypothalamic neurons synthesize oxytocin and ADH
- Oxytoxin and ADH are transported down the axons of hypothalmohyposeal tract to posterior pituitary
- Oxytoxin and ADH are stored in neurosecretory bodies in posterior pituitary
- When associated hypothalmic neurons fire, nerve impulses arriving at the neurosecretory bodies cause oxytoxin or ADH to be released into blood
Thyroid Gland
- location
- blood supply
- cells
- hormones
- function
- importance
LO8
bi-lobed gland just below larynx and anterior to trachea
blood supply: from superior and inferior thyroid vessels
Cell types
- follicular cells
- Parafollicular C cells
Parts of the thyroid
- Thyroid follicle
- Follicle lumen
Hormones
- thyroid hormone
Target organs
- hypothalamus
- thyroid gland
- kidney
- bone
Function
- control basal metabolism
- control O2 usage
- control body temperature
- only gland to store hormone outside cell
Follicular Cell
- cell types
simple cuboidal to columnar epithelium
many of them make follicles
they surround a fluid called colloid
Colloid
- composition
thyroglobulin
- storage form of T3 and T4
- must have iodine to activate
Thyroid Hormone Synthesis and Turnover
- steps
made and stored in thryoglobulin
- thyroglobulin synthesized in RER, glycoslyated in golgi, secreted by EXOcytosis into lumen of follicle (colloid)
- Iodinated at apical surface forming T3 and T4 that remains to thyroglobulin
- TSH stimulates internalization of thyroglobulin via endocytosis where it is degrade, freeing T3 and T4
- T3 and T4 is released from basal surface of follicle cells into circulation
Parafollicular Cells
- hormone
- derived from neural crest cells
lie outside the follicle
secrete calcitonin when blood levels of calcium are high
lowers CA2+ in blood by:
- stimulating secretion by kidneys
- decreasing the calcium-releasing activity of osteoclasts
- increasing osteogenesis by osteoblasts
Negative feedback loop for Hypothalmamic- Anterior Pituitary Thyroid Axis
- steps
- stimulus causes hypothalamus to secrete TRH -> acts on anterior pituitary
- Thyrotropic cells in anterior pituitary are stimulated to release TSH
- TSH acts on cells on thryoid gland. Follicular cells are stimulated to release TH
- TH stimulates target cells to increase metabolic activities=> increase in basal body temperature
- high TH levels=> increase heat production in cells=> inhibit TRH secretion
Thyroid diseases
-list
- Grave’s disease
- Hypothyroidism
- Goiters
Grave’s disease
- describe
- symptoms
LO9
abnormal antibodies stimulating TSH receptors causing over secretion of T3 and T4
symptoms
- elevated metabolism
- sweating
- rapid HR
- weight loss
- protruding eyes
more common in women
Hypothyroidism
- describe
- symptoms
LO9
insufficient T3 and T4
(opposite of graves)
symptoms
- low metabolism
- weight gain
- lethargy
- chillness
- edema
- mental sluggish
Goiters
- describe
LO9
thyroid enlargement most commonly due to IODINE deficiency
follicle cells keep producing thyroglobulin but cannot iodinate it to make TH
Parathyroid Glands
- location
- blood supply
- cell types
- main target organs and signficance
LO10
small ovoid glands
-posterior surface of thyroid gland
important in regulating serum calcium and phosphate levels (ESSENTIAL FOR LIFE)
blood supply: from superior and inferior thyroid vessels
cell types
- chief cells
- Oxyphil cell
Target organs
- bone
- kidney
- intestine
- bloodstream
Chief principle cell
LO10
in parathyroid gland
release parathyroid hormone
secretion occurs when blood Ca2+ drops below normal and stops when levels return to normal
- looks like nuclei
Oxyphil Cells
unknown function
-looks like cytoplasm surrounding chief cells (nuclei)
Calcium Regulation of PTH
if blood Ca2+ drops below 9.5 mg/dl=> Parathyroid releases PTH into bloodstream
- increase osteoclast activity to resorb bone and release its calcium stores
- increase calcium retention by kidneys
- stimulates kidney to convert an inactive form of vit D to calcitriol (active vit D)
- calcitriol increase calcium absorption by intestines
PTH will be inhibit when blood Ca2+ levels increases
Adrenal glands
- location
- layers and secretion
- cell types
- hormones
LO11
Adrenal Cortex (outer) below capsule 1. zona glomerulosa - secrete aldosterone 2. zona fasciculata - secrete cortisol and androgens 3. Zona reticularis - secrete cortisol and androgens
Medulla (inner core)
- secrete epinephrine and noepinephrine
Adrenal Cortex
distinct yellow
secretes 25 steroid hormones (corticosteroids)
Zona Glomerulosa
-hormone
in adrenal cortex
(mineralcorticoids)
- influence sodium and potassium levels
aldosterone
- target kidney fxns
- in response to low blood pressure or blood volume
- controlled by RAAS
Zona fasciculata
-hormone
in adrenal cortex
glucocorticoids
- influence glucose metabolism and immune system
- released under control of ACTH from anterior pituitary
Cortisol
- deals with stress
- mediates glucose metabolism
- negative feedback mechanism for immune system
Zona reticularis
in adrenal cortex
androgens
influence secondary sex characteristics
Adrenal Medulla
inner core of each adrenal gland
consists of large, spherical cells (chromaffin cells)
when stimulated by ANS (SYMPATHETIC division) => secrete both epinephrine and noepinephrine
Chromaffin Cells
- cell types
target of sympathetic neurons
- Epinephrine cells
- smaller with granules less electron dense than NE cells - Norepinephrine cells- larger with granules more electron dense
Suprarenal Gland Syndromes
- Addison’s disease
2. Cushing’s syndrome
Addison’s disease
LO12
HYPOsecretory disordder in glucocorticoids and mineralcorticoids
- blood glucose and sodium levels drop
- severe dehydration and low BP
- fatigue
- loss of apetite
- autoimmune disease or inherited metabolic disease
RARE
Cushing’s syndrome
LO12
hypersecretion of glucocorticoids bc of ACTH-secreting pituitary tumor or tumor in adrenal cortex
- high serum glucose levels
- protein loss in muscle
- muscle weakeness
- sweating
- lethargy
- fat distribution
Pancreas Histology
-portions
LO13
Exocrine
- glands
- aids in digestion
- organized in pancreatic acini
Endocrine
- organized in pancreatic islets (langerhans)
- scatteered amongst the exocrine cells
Cells of Endocrine Pancreas
- describe
LO13 (list cells only)
- Alpha Cells
- secrete glucagon when blood glucose levels drop
- stimulates release of glucose from liver glycogen - Beta Cells
- secrete insulin when blood glucose levels are elevated
- promote glycogen storage in liver and entry into cells - Delta cells
- secrete somatostatin (slows insulin and glucose release)
- control rate of nutrient entry into bloodstream and acell
- stimulated by high levels of nutrients and in bloodstream - F cells
- secrete pancreatic polypeptide that inhibit somatostatin release
Pancreatic Blood Supply
- Insuloacinar portal system
- supply islets of langerhand and pancreatic acini
- enable local action of exocrine pancreas of hormones - Acinar vascular system
- independent arterial supply
- supply pancreatic acini
Other endocrine organs/cell
LO14
- gonads- estrogen, testosterone, progesterone
- Heart- atrial natriuretic peptide
- GI tract- peptides regulating digestion (gastrin and secretin)
- placenta- estrogen, progesterone, HCG
- Kidney- renin, erythropoietin
- Skin- precursor to vitamin D
