Histology of Endocrine Organs Flashcards
3 basic classes of hormones; which one is the largest?
Peptide/protein hormones - largest class, chains of amino acids
Biogenic amines - produced by altering the structure of a specific amino acid
Steroid hormones - derived from cholesterol
_______ stimuli control hormonal release by monitoring levels of ions and nutrients in the blood; ex: release of PTH stimulated by low [Ca]
Humoral
______ stimuli control hormonal release using nerve signals; ex: release of epinephrine from adrenal gland in response to a signal from sympathetic nerve fibers
Neuronal
_______ stimuli control hormone release by another hormone secreted into bloodstream by another endocrine cell or organ; ex: release of thyroid hormone stimulated by release of TSH from pituitary
Hormonal
Endocrine gland organization consists of ____________ cells that lack a free surface, arranged as cords/follicles and some as isolated individual cells
Endocrine glands are derived from epithelia and are well vascularized, often with ________ endothelium
Epithelioid
Fenestrated
Primary site where CNS controls endocrine function via pituitary gland
Hypothalamus
The hypothalamus is located below the _______, behind the _______ and surrounding the _____ ventricle
Thalamus; optic chiasma; 3rd
The pituitary gland, aka the _______, is located inferior to the hypothalamus
It is a small, slightly oval gland housed within the hypophyseal fossa (sella turcica) of the ______ Bone
It is connected to the hypothalamus by a thin stalk of tissue known as the ________
Hypophysis
Sphenoid
Infundibulum
The pituitary gland is partitioned structurally and functionally into what 2 portions?
Anterior = adenohypophysis Posterior = neurohypophysis
What are the 3 direct targets of hypothalamic hormones?
Anterior pituitary gland (releasing and inhibiting factors)
Kidney and uterus (releasing ADH, oxytocin, in posterior pituitary)
Adrenal medulla (sympathetic innervation)
The hypothalamus releases hormones, collectively referred to as _____ hormones that stimulate or inhibit release of other hormones from the _____pituitary, thus they cause an effect with indirect targets of the hypothalamus
Tropic; anterior
Tropic hormones from the hypothalamus have an indirect influence by stimulating secretion of the anterior pituitary gland; what are some of the indirect targets of this master control?
Thyroid gland —> TSH
Adrenal cortex —> ACTH
Mammary gland —> Prolactin
Gonads (testes or ovaries) —> FSH, LH
Bone and other organs —> growth hormone, melanocyte stimulating hormone
The anterior pituitary is initially derived from an _________ placode leading to ______ pouch by 3 weeks gestation
The pouch loses its connection with the outside and is near final by 8 weeks. It joins the diverticulum from the developing diencephalon of the _____ _____
The _________ forms the posterior pituitary and infundibular stalk; and ______ pouch form the rest of the pituitary
Ectodermal; rathke’s
Neural tube
Infundibulum; rathke’s
What hormones are released from the pituitary beginning at 7 weeks thru 13 weeks gestation?
ACTH (7 weeks)
GH (8-9 weeks)
TSH and LH (12 weeks)
FSH (13 weeks)
______ = space left between the migrated diencephalon and rathke’s pouch forming anterior and posterior pituitary
Pars intermedia
Which part of the pituitary constitutes 80% of the gland, comprised of glandular epithelium cells controlled by neurohormones released from the hypothalamus?
Anterior pituitary
The posterior pituitary is comprised of axons from the _______ and glial/support cells.
These axons carry _____ and _____ for storage and release in the posterior pituitary
Hypothalamus
ADH; oxytocin
_______ = part of rathke’s pouch that wraps around the stalk/infundibulum of the pituitary gland
Pars tuberalis
3 components of anterior pituitary
Pars tuberalis Pars intermedia Pars distalis (aka pars anterior)
2 components of posterior pituitary
Infundibular stalk
Pars nervosa
What is the remnant of rathke’s pouch that may be seen on a microscopic slide of pituitary?
Cyst intermedia
Major cell types of anterior pituitary and what they secrete
Somatotropic cells - GH
Thyrotropic cells - TSH
Corticotropic cells - ACTH and MSH
Gonadotropic cells - FSH and LH
Mammotropic cells - Prolactin
Acidophils are lighter staining cells of the pars anterior. What 2 cell types in this region are acidophils?
Somatotrophs
Mammotrophs
Basophils are darker staining cells of the pars anterior. What 3 cell types in this region are basophils?
Corticotrophs
Thyrotrophs
Gonadotrophs
Acidophils and basophils are the primary cells of interest on a histological slide of the pars anterior. What other landmarks might be seen on these slides?
Chromophobes - don’t stain as well, unknown function
Sinusoidal (fenestrated) capillaries
On viewing a histological slide, you note small basophils and colloid-filled follicles lined by cuboidal epithelium as well as the appearance of a cleft. What part of the pituitary is this?
Pars intermedia
[note this is rudimentary in adults; found b etween pars distalis and pars nervosa]
T/F: the pars nervosa is continuous with the median eminence of the hypothalamus via the infundibular stalk
True
What are the components of the pars nervosa (specifically those that can be seen on histological slide)
Hypothalamic unmyelinated axons - herring bodies = expanded axonal nerve terminals storing ADH/oxytocin
Pituicytes (glia-like) supporting the nerve fibers
Fenestrated capillaries
The infundibulum suspends the pituitary gland from the hypothalamus.
The neural portion (infundibular stalk) is part of the _________ connecting the pars nervosa and median eminence of hypothalamus
The ________ portion surrounds the pars tuberalis and envelopes the infundibular stalk, possibly forming a partial or total collar, consisting of numerous cuboidal cells arranged in cords
Neurohypophysis
Adenohypophysis
What is the primary source of blood supply to the hypophysis?
Hypothalamo-hypophyseal portal system
In the hypothalamo-hypophyseal portal system, hypothalamic hormones travel through portal veins to the ______ pituitary where they stimulate or inhibit release of hormones made there. Hormones are then secreted into the secondary capillary plexus, with blood that first entered via the ______ artery.
Blood from secondary capillary plexus enters general circulation
Anterior; superior hypophyseal
What are the 3 components of the hypophyseal portal system?
Primary capillary plexus
Hypophyseal portal veins
Secondary capillary plexus
When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the ______ capillary plexus of the hypophyseal portal system
Primary
What artery supplies the anterior vs posterior pituitary?
Anterior = superior hypophyseal a.
Posterior = inferior hypophyseal a.
________ hormone is released from the posterior pituitary and targets the kidneys, regulating Na and H2O balance
ADH
_______ is released from the posterior pituitary and targets uterine smooth muscle and stimulates lactation; induces birth. May be involved in sexual arousal and social bonding
Oxytocin
By what process are ADH and Oxytocin made and released?
Hypothalamic neurons synthesize ADH and oxytocin, then they are transported down axons of hypothalamohypophyseal tract to posterior pituitary
They are stored in neurosecretory bodies in the posterior pituitary. When associated hypothalamic neurons fire, nerve impulses cause them to be released into the blood
What pituitary disorder is characterized by excess production of GH due to a tumor? How does the disease differ if it occurs prior vs. after bone growth plate closure?
Gigantism
Prior to closure - individual very tall
After closure - enlargement of extremities and organs (acromegaly)
What are “pituitary dwarfs”?
Caused by hyposecretion of GH; normal body proportion but rarely exceed 4 ft
If given GH, many reach normal stature
Outpocketing of diencephalon’s roof of 3rd ventricle with role in growth, development, and circadian rhythms
Pineal gland
Describe composition of pineal gland
Covered with pia mater
Consists of pinealocytes, neuroglia, and calcified granular material (brain sand)
What 2 hormones are synthesized by the pineal gland?
Melatonin
Serotonin
The thyroid is a butterfly shaped bilobed endocrine gland just inferior to the ______ and anterior to the ______
Larynx; trachea
What are the 2 major groups of vessels that supply the thyroid and parathyroid glands?
Superior thyroid vessels
Inferior thyroid vessels
The thyroid is characterized by structures called ______ consisting of a specialized layer of simple cuboidal to columnar cells, surrounding a fluid called ______, which is a storage form of thyroid hormone
Follicles; colloid
The colloid in thyroid tissue contains _______, a storage form of thyroid hormones ____ and _____ (_____-containing hormones)
Thyroglobulin; T3; T4; iodine
What is the only gland to store hormone outside the cell?
Thyroid
What do thyroid hormones control?
Basal metabolism
O2 usage
Body temp
Thyroid hormone is generated and stored extracellularly as thyroglobulin
Thyroglobulin is synthesized in the _______, _________ in the golgi, and secreted by exocytosis into the lumen of the ________
It is __________ at the apical surface, forming T3 and T4 that remains bound to thyroglobulin
rER; glycosylated; follicle (colloid)
Iodinated
In order to release stored thyroglobulin, ______ stimulates its internalization via endocytosis where it is degraded, freeing ____ and _____ which are released from the _____ surface of the follicle cells into circulation
TSH; T3; T4; basal
What is T4
Thyroxine
What cells type lies just outside the follicles of the thyroid?
Parafollicular C cells
What do parafollicular C cells secrete and what is its action?
Secrete calcitonin when blood Ca is high —> lowers circulating calcium by stimulating secretion by kidneys, decreasing activity of osteoclasts, and increasing osteogenesis by osteoblasts
The hypothalamic-anterior pituitary-thyroid axis is characterized by what type of feedback loop? What is an example?
Negative feedback
- Stimulus such as low body temp causes hypothalamus to secrete TRH which acts on anterior pituitary
- Thyrotropic cells in AP release TSH
- TSH acts on cells of thyroid gland. Follicular cells are stimulated to release thyroid hormone
- Thyroid hormone stimulates target cells to increase metabolic activity, increasing basal body temp
- Hypothalamus detects increased blood temp and inhibits further secretion of TRH, as well as inhibits interactions of TRH and AP gland
Condition characterized by abnormal Abs stimulating TSH receptors causing oversecretion of T3 and T4
Grave’s disease
Symptoms of Grave’s disease
Elevated metabolism, sweating, rapid HR, eyeball protrusion
T/F: Grave’s disease is 4-8x more common in men
False; women
Tx for grave’s disease
Thyroidectomy or anti-thyroid drugs
Condition characterized by insufficient T3 and T4 production, often an autoimmune disease causing follicle cell death
Hypothyroidism
Symptoms of hypothyroidism
Low metabolic rate, weight gain, lethargy, chilliness, edema, mental sluggishness
Tx for hypothyroidism
Synthetic T3/T4
Goiters = thyroid enlargement most commonly due to ______ deficiency; follicle cells keep producing thyroglobulin but cannot _______ it to make TH
Iodine; iodinate
Describe the parathyroid glands
Small ovoid glands lying on the posterior surface of the thyroid gland that release parathyroid hormone (PTH); usually 2 pairs but can be more
Parathyroid glands have major importance in regulating serum _____ and ____ levels
Calcium; phosphate
What are the 2 main cell types associated with parathyroid gland? What are their functions?
Chief (principle) cells - release PTH when blood calcium is low
Oxyphil cells - function unknown
PTH opposes the action of what hormone?
Calcitonin
How does PTH increase serum calcium levels?
Stimulates osteoclasts to resorb bone and release calcium stores
Increases calcium retention by kidneys
Stimulates kidneys to convert an inactive form of vitamin D to calcitriol, which increases calcium absorption by intestines
Regions of adrenal gland
Adrenal cortex (zona glomerulosa, zona fasciculata, zona reticularis)
Adrenal medulla
The adrenal cortex has a distinctive _____ color d/t stored lipids in its cells. More than 25 different steroid hormones (_______) are secreted from the cortex, vital for survival
Yellow; corticosteroids
The zona glomerulosa secretes _______, specifically ________
Mineralocorticoids; aldosterone
The zona fasciculata secretes _______, specifically _____
Glucocorticoids; cortisol
The zona reticularis secretes _______
Androgens
The adrenal medulla primarily consists of clusters of large, spherical cells called ______ cells, which are derived from neural crest cells
Chromaffin cells
When the chromaffin cells of the adrenal medulla are stimulated by pre-synaptic sympathetic neurons, one population secretes _____ and a second population secretes ______
Epinephrine (adrenaline); norepinephrine (noradrenaline)
Compare size and density of electrons associated with epinephrine vs. norepinephrine cells
Epinephrine cells = smaller with granules less electron dense than NE cells
Norepinephrine cells = larger with granules more electron dense than epi cells
What condition is characterized by hyposecretory adrenal cortex, usually affecting both glucocorticoids and mineralocorticoids, causing hypoglycemia, hyponatremia, hypotension, dehydration, fatigue, and anorexia?
Addison’s disease
What causes addison’s disease?
Autoimmune or inherited metabolic disease leading to deficiencies in hormone producing enzymes
Condition characterized by hypersecretion from adrenal gland affecting glucocorticoids, either because of ACTH secreting pituitary tumor or a tumor in the adrenal cortex
Cushing’s syndrome
The _____ portion of the pancreas makes up most of the gland and participates in digestive function. Exocrine cells are organized in structures called _________. Endocrine cells are organized into clusters called __________, which are scattered throughout the exocrine cells
Exocrine; pancreatic acini; islets of Langerhans
What cell types are associated with the endocrine pancreas?
Alpha cells
Beta cells
Delta cells
F-cells
Function of alpha cells of the endocrine pancreas
Secrete glucagon with BG is low; stimulates release of glucose from liver glycogen stores
Function of beta cells of the endocrine pancreas
Secrete insulin when blood glucose levels are elevated and promotes glycogen storage in liver and entry into cells
Function of delta cells of the endocrine pancreas
Secrete somatostatin which slows the release of insulin and glucagon, thereby controlling the rate of nutrient entry into bloodstream and cells; stimulated by high levels of nutrient in blood
Function of F cells of the endocrine pancreas
Secrete pancreatic polypeptide that inhibits the release of somatostatin
The pancreas has dual blood supply from what 2 sources?
- Insuloacinar portal system
2. Acinar vascular system
The pancreas has dual blood supply from the acinar and insuloacinar vascular systems
Each islet of langerhans is supplied by ______ arterioles, forming a network of capillaries lined by fenestrated epithelial cells. This network is called the insuloacinar portal system. Capillaries leaving the islet supply blood to the _____ ______ surrounding the islet. This vascular system enables a local action on the ______ pancreas of hormones produced in the islet.
An independent arterial system, the acinar vascular system, supplies the pancreatic ______
Afferent; pancreatic acini; exocrine
Acini
