Histology Of Endocrine Organs Flashcards
Organs of the endocrine system
Hypothalamus Pineal Pituitary Thyroid Parathyroid Heart Adrenal glands Kidneys Pancreas GI tract Gonads Integument Adipose
Epithelial cells lack a _____ and are arranged as cords/follicles and some isolated individual cells
Well vascularized because release hormones into the ____.
Vessels have a ____ endothelium.
Free surface
Bloodstream
Fenestrated
Hypothalamus is posterior to the ____ and inferior to the ____.
Hanging from hypothalamus is the ____ housed in the hypophyseal fossa (sella turcica) of the sphenoid bone.
Pituitary gland is connected to hypothalamus by the ____ and separated into two parts ___ and ____.
Optic chiasm
Thalamus
Pituitary gland
Infundibulum
Anterior (adenohypophysis) and posterior (neurohypophysis)
Hypothalamus directly targets what organs?
Anterior pituitary gland
Kidneys and uterus (ADH, oxytocin)
Adrenal medulla (sympathetic innervation)
Indirect targets of the hypothalamus
Releases hormones that stimulate or inhibit releases of other hormones from the anterior pituitary gland
Thyroid gland Adrenal cortex Mammary gland Gonads Bone
Pituitary gland is derived from the ____.
Posterior pituitary more specifically derived from ____.
Anterior pituitary is derived from a ____ leading to _____ at ____ weeks.
Pouch loses connection with the outside and is in its final location at ___ weeks.
Pouch joins diverticulum from developing ____.
_____ forms posterior pituitary and infundibular stalk
Ectoderm
Diencephalon of neural tube
Ectodermal placode; Rathke’s pouch; 3
8
Diencephalon of neural tube
Infundibulum
Anterior pituitary contains ____ epithelium cells controlled by _____ released by hypothalamus.
Posterior pituitary made of ___ from hypothalamus and support cells that carry ____ and ____.
Glandular; neurohormones
Axons; carry ADH and oxytocin
Major cell types in anterior pituitary
Acidphils stain pink and include Somatotropin cells: GH
Mammotropic cells: prolactin
Basophils stain purple and include
Thyrotropic cells: TSH
Corticotropic cells: ACTH, MSH
Gonadotropic cells: FSH, LH
Chromophobes stain with least color
Sinusoidal (fenestrated) capillaries stain red
Where is the pars intermedia?
What cells does it contain?
Derived from what?
Between the pars distalis and pars nervosa
Basophils and colloid-filled follicles lined by cuboidal epithelium
Rathke’s pouch
The pars nervosa is a continuation of the ____ through the ____.
It stores and releases hormones from ____.
Consists of hypothalamic ____ axons called ____ that store _____.
____ support the nerve fibers.
Median eminence of the hypothalamus; Infundibular stalk
Axon terminals
Unmyelinated; herring bodies; ADH/oxytocin
Pituicytes
Suspends the pituitary gland from the hypothalamus
Neural portion is part of what? And connects what?
What kind of axons?
Adenohypophysis surrounds what?
Infundibulum
Neurohypophysis; connecting the pars nervosa and median eminence of hypothalamus
Unmyelinated
Pars tuberalis enveloping the infundibular stalk
Describe the blood flow to the anterior pituitary gland
Hypothalamic-hypophyseal portal system
Tertiary hormone travels down an axon to the median eminence of the hypothalamus -> hypothalamus releases a hormone into the capillaries -> blood is collected into hypophyseal portal veins -> enter sinusoidal capillaries in anterior pituitary -> receptors bind hormone and signal release of secondary hormone through venous system of anterior pituitary
Describe the blood flow to the posterior pituitary gland
Hypothalamic-hypophyseal portal system
Neurons in the hypothalamus travel down axons through the infundibulum to posterior pituitary -> hormones released into sinusoidal bed arterial supply in posterior pituitary -> exit through vessels to go to target
Targets the kidney, regulates Na and water retention
ADH
Targets uterine smooth m and stimulates lactation, induces birth, sexual arousal, social bonding
Oxytocin
Two pituitary disorders
Explain
Gigantism: excess production of GH because of tumor; if occurs before bone growth plates close growth, will grow taller; after growth plates close, extremities and organs enlarge (acromegaly)
Pituitary dwarfs: hyposecretion of GH; have achondroplasia from mutation in fibroblast growth factor
Actions of pineal gland
Cells of the pineal gland
Control circadian rhythm and synthesizes melatonin and serotonin; cycles every 90 minutes
Pinealocytes, neuroglia, calcified granular material (brain sand)—-Ca phosphate crystals located in intercellular spaces
Location and blood supply of the thyroid
Below larynx and anterior to trachea
Superior thyroid vessels and inferior thyroid vessels
Cells of the thyroid
What do colloid cells contain?
Actions of thyroid gland?
Follicles with follicular cells surrounding a fluid called colloid
Colloid contains thyroglobulin (storage form of T3 and T4)
Control basal metabolism, O2 usage, body temp
Describe the synthesis of thyroid hormone
Generated and stored as thyroglobulin in thyroid
Sythesized in rER of follicle cells -> glycosylated -> exocytosis into lumen of follicle (colloid) -> iodinated at apical surface forming T3 and T4 that remains bound to thyroglobulin -> TSH stimulates internalization of thyroglobulin by endocytosis and degradation -> frees T3 and T4 which are released from basal surface of the follicle cells into circulation
Location of parafollicular C cells
Action?
Outside of the thyroid follicles
Secrete calcitonin when blood Ca levels are high
Lower Ca by: stimulating secretion of kidneys, decreasing
Ca-releasing activity of osteoclasts, increase osteogenesis by osteoblasts
Describe the hypothalamic-anterior pituitary-thyroid negative feedback loop
Hypothalamus releases TRH into portal system -> stimulates thyrotrophs in the anterior pituitary gland to release TSH -> thyroid gland has TSH receptor -> thyroid released thyroid hormone (T3/T4) into blood target organs in body -> increased overall metabolism -> as symptoms return to normal, negative feedback to hypothalamus
Thyroid hormone also negatively feeds back to inhibit TRH receptors
Disease of thyroid gland
Grave’s disease
Hypothyroidism
Goiters
What causes grave’s disease?
Symptoms?
Abnormal antibodies mimic TSH and cause over-secretion of T3 and T4
Elevated metabolism, sweating, rapid HR, weight loss, protruding eyeballs, thyroidectomy
What causes hypothyroidism?
Symptoms?
Insufficient T3 and T4 production usually from an autoimmune disease causing follicle cell death
Low metabolic rate, weight gain, lethargy, cold, edema, mental sluggish
What causes goiters?
Thyroid enlargement due to iodine deficiency
Follicle keep producing thyroglobulin but can’t iodinate it to make TH
Thyroid keeps receiving TSH because detects low TH levels; thyroid enlarges from overstimulation
Location of parathyroid glands
Function?
Cells?
Posterior surface of thyroid gland
Release parathyroid hormone; regulates serum Ca and phosphate levels
Chief cells: release PTH when Ca levels low
Oxyphil cells
Describe Ca regulation by PTH
Ca levels drop below 9.5
Parathyroid releases PTH: sitmulates osteoclasts to reabsorb bone and release its Ca stores; increase Ca retention by kidneys; stimulates kidneys to convert inactive vitamins D to calcitriol (active vitamin D) which increases Ca absorption in SI
Ca increases and inhibits further PTH secretion
Components of the adrenal gland
Cortex: zona glomerulosa (gland looking) zona fasiculata (rays/fasicles) zona reticularis (irregular)
Medulla
Hormones and their function in the zones of the adrenal cortex
Zona glomerulus: mineralocorticoids -> influence Na and K levels; aldosterone (targets kidney fx; secreted in response to low BP)
Zona fasiculata: glucocorticoids -> influence glucose metabolism and immune system; released after ACTH stimulation; cortisol (stress and glucose metabolism and anti-inflammatory of immune system)
Zona reticularis: androgens -> influence secondary sex characteristics
Cells and function of adrenal medulla
Where are they derived from?
Chromafin cells (target of sympathetic neurons)
Sympathetic stimulation causes adrenal medulla chromaffin cells to secrete E and NE
Neural crest cells (ectoderm)
Addison’s diseases
Causes?
Symptoms?
Hyposecretion of glucocorticoids and mineralocorticoids; because of an autoimmune disease or inherited metabolic disease w/ deficiencies in hormone producing enzymes
Blood glucose and Na levels drop, dehydration, low BP, fatigue, loss of appetite
Cushing’s syndrome
Causes?
Symptoms?
Hypersecretion of glucocorticoids because or either ACTH secretions pituitary tumor or tumor in adrenal cortex
High glucose, protein loss in muscles, muscle weakness, weight gain, lethargy, swollen face, buffalo hump, moon face
Cells of the pancreas
Function?
Exocrine cells = Pancreatic acini
Endocrine cells = Pancreatic islets of Langerhans including:
Alpha cells: glucagon (release glucose from liver)
Beta cells: insulin (glycogen storage)
Delta cells: somatostatin (slows release of insulin and glucagon)
F-cells: pancreatic polypeptide (inhibit release of somatostatin)
Describe pancreatic blood supply
Each islet has its own blood supply of fenestrated capillaries (insuloacinar portal system)
Supplies blood to the pancreatic acini surrounding the islet
Enable local action on exocrine pancreas from hormone produced in the islets
Endocrine organs and the hormones they secrete
Gonads: estrogen, testosterone, progesterone
Heart: atrial natriuretic peptide
GI tract: peptides regulating digestion
Placenta: estrogen, progesterone, HCG
Kidney: renin, erythropoietin
Skin: precursor to vitamin D
