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UKCD Histo Endocrine
test objective answers for endocrine
| Question | Answer |
|---|---|
| How do endocrine epithelial glands differ from exocrine glands also derived from epithelium? | Endocrine organs lack an epithelial duct. |
| Be able to list the various endocrine organs of the body. | Thymus (thymosin secreted); hypophysis; thyroid; parathyroid; suprarenals; pineal; islets of Langerhans; interstitial cells of Leydig. |
| Aside from being ductless, name one other critical feature of an endocrine gland. | It is highly vascular as the hormonal granules are released into the blood supply instead of via a duct. |
| What are the two divisions of the hypophysis? | Adenohypophysis (anterior portion) and neurohypophysis (posterior portion). |
| From where did each hypophyseal division arise embryologically? | The adenohypophysis arises from the oral ectoderm; the neurohypophyis arises from the neural ectoderm of the diencephalon. |
| List the component parts of each hypophyseal division. | Adenohypophysis: pars distalis, pars intermedia, pars tuberalis. Neurohypophysis: median eminence, infundibulum, pars nervosa. |
| What is the general role of the hypophysis endocrine gland? | The master endocrine organ of the body |
| What specific general functions does the hypophysis control? | Regulates growth, reproduction and metabolism. |
| Name the two main cell types comprising the pars distalis. | Chromophils and chromophobes. |
| List the two general types of chromophils. | Acidophils and basophils. |
| List the two types of acidophils and the main hormone each secretes and its function | Somatotrophs that secrete somatotropin to stimulate cellular metabolism; mammatrophs that secrete prolactin promoting mammary gland development during pregnancy and lactation after birth. |
| List the three types of basophils and the main hormone each secretes and its function | Corticotrophs secrete ACTH that stimulates the suprarenal cotrex; thyrotrophs secrete TSH that stimulates the thyroid gland; and gonadotrophs secrete FSH and LH that stimulate the gonads. |
| What do chromophobes do? | They are either nonspecific stem cells or partially degranulated chromophils. |
| What are folliculostellate cells and what is their function? | FS cells are a non-secretory form in the pars distalis whose exact function remains unclear but appear to be supporting cells. |
| Describe the appearance of the pars intermedia? | Colloid-containing cysts with a wall of cuboidal epithelium. |
| Between which two regions is the pars intermedia located? | Between the pars distalis and pars nervosa. |
| What cells type(s) is/are present in the pars intermedia? | Cords of basophils. |
| What do these cells secrete and what are their functions? | They secrete a hormone that becomes MSH (melanin stimulating hormone). Their exact function is unclear. |
| Where is the pars tuberalis located? | Surrounds the hypophyseal stalk but may be absent posteriorly. |
| List the hormones secreted from the pars tuberalis? | No specific hormones are known to be released from the pars tuberalis. |
| What are the three regions of the neurohypophysis? | Median eminence, infundibulum and pars nervosa. |
| What is the hypothalamo-hypophyseal tract? | A group of unmyelinated axons that extend from the supraoptic and paraventricular nuclei of the hypothalamus and terminate in the pars nervosa. |
| What does hypothalamo-hypophyseal tract convey and what is the function of each hormone? | The hypopthalamo-hypophyseal tract conveys oxytocin and vasopressin into the pars nervosa for release. Oxytocin is a smooth muscle contractant while vasopressin is antidiuretic hormone. |
| What are pituicytes and what is their function? | Glial-like cells that sheath/support the axons of the hypothalamo-hypophyseal tract and make up approximately 25% of the pars nervosa. |
| What are Herring bodies? | Terminal regions of the axons of the hypothalamo-hypohyseal tract that accumulate large volumes of neurosecretory vesicles for release into the hypophyseal blood supply. |
| What hormones are secreted by the thyroid gland and what do they control? | Thyroxine (T4) and triiodothyronine (T3) responsible for stimulation of metabolic rate. Calcitonin is also secreted and regulates blood calcium levels as well as storage of calcium in bone. |
| Which specific cell type secretes each hormone? | Principle (follicular) cells secrete TY3/T4 while parafollicular cells secrete calcitonin. |
| What is the structural arrangement of the thyroid gland? | Arranged into follicles composed of cuboidal epithelium with a central mass of colloid. |
| How do follicular cells differ from parafollicular cells aside in their placement in the follicle? | Principle cells are under the control of TSH from the adenohypophysis. Only Principle cells make contact with the lumen of the follicle. |
| What is different about the way T3 and T4 are secreted? | Principle cells do not store their secretory product, instead they release it bound to thyroglobulin into the central follicle. |
| How do active follicular cells differ from inactive structurally? | Active follicular cells become tall cuboidal in morphology whereas inactive cells become low cuboidal. |
| Where are the parathyroid glands located? | In the posterior aspect of the thyroid gland. |
| What do they secrete? | Parathyroid hormone is produced. |
| What cell types comprise the parathyroid glands? | Chief (principle) cells and oxyphil cells. |
| What is the function of Chief cells? | Chief cells secrete parathyroid hormone. |
| What is the function of Oxyphil cells? | Oxyphil cells are thought to be inactive phases of the chief cell. |
| What role does PTH have in homeostasis? | PTH is responsible for maintaining extracellular levels of calcium - binding to osteoblasts signalling them to increase secretion of osteoclast-stimulating factor to keep calcium levels high. |
| Why is PTH essential to life? | Calcium is required for muscle contractrion and the heart is composed of cardiac muscle. |
| How is each suprarenal gland organized structurally? | Into an outer cortex and inner medulla. |
| What are the three regions of the cortex and what type of hormone does each secrete? | Zona glomerulosa secretes mineralocorticoids; zona fasciculata secretes glucocorticoids; and the zona reticularis secretes androgens. |
| How does the two types of arteries arising from the subscapular sinus differ? | The short cortical aa. suppy the cortex and the medulla whereas the long cortical aa. pass unbranched into the medulla and supply only that region. |
| From where does the suprarenal medulla arise embrologically? | From ectodermal neural crest cells. |
| List the cell types that comprise the suprarenal medulla. | Chromaffin cells and sympathetic ganglion cells comprise the surparenal medulla. |
| What is the function of Chromaffin cells medullary cells? | Chromaffin cells produce catecholamines (epinephrine and norepinephrine). |
| What is unusual about the innervations of this region of the organ? | The supraneal medulla receives direct stimulation by sympathetic preganglionic fibers. |
| How does the organization relate to its function? | Catecholamines are released in response to stimulation by preganglionic sympathetic nn. In fear or stress, these fibers that originates from the hypothalamus cause increased levels of epinephrine to be release to prepare the body for ‘fight ir flight’. |
| What does the pineal gland secrete? | Melatonin. |
| What is the function of melatonin secretion? | Now thought to be able to protect the CNS by scavaging and eliminating free radicals produced during oxidative stress. |
| Which cell types comprise the pineal? | Pinealocytes and insterstitial cells. |
| Which cell type secretes the major hormone for the pineal gland? | Pinealocytes secrete melatonin. |
| What is brain sand? | Calcium phosphates and carbonates that accumulate as concentric rings around an organic matrix. |
| What causes brain sand to increase/decrease in size? | Brain sand deposits increase during short photoperiod and diminish when the pineal secretes melatonin. |
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wiechartm
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