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77 Cards in this Set
- Front
- Back
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How do exocrine and endocrine glands secrete?
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Exocrine - products are secreted via ducts directly onto the surface.
Endocrine - ductless glands that secrete their products into the blood or lymph, involve signaling cells and target cells. |
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Describe the development of the pituitary.
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The oral cavity comes up to wrap around the extension of the hypothalamus forming the adenohypophysis and neurohypophysis respectively.
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What are the divisions of the adenohypophysis?
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The pars distalis, pars tuberalis, pars intermedia.
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What are the divisions of the neurohypophysis?
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The pars nervosa and infundibulum.
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What are the parts of the infundibulum?
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The infundibular stalk and the median eminence (or tuber cinereum)
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What are the subsets of acidophils and basophils?
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Acidophils - somatotrops and mammotrops
Basophils - gonadotrops, POMC's and thryotrops |
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True or false: cells migrate from the pars intermedia to the pars nervosa.
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True.
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What is a common feature of pars tuberalis tissue?
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Channels within the tissue
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What enzymes do the alpha cells or acidophils secrete?
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Somatotrophs - somatotropin
Mammotrophs - prolactin |
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What enzymes do the beta cells or basophils secrete in the thyroid?
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Gonadotrops - FSH and LH
POMC - ACTH Thyrotrops - thyroid secreting hormones |
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What pars wraps the hypophyseal stalk?
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The pars tuberalis.
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What vascularizes the pars tuberalis?
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By arteries and the hypophyseal portal system.
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What is the function of pituicytes?
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The pituicytes support the axons in the pars nervosa.
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What do the nerve terminals in pars nervosa secrete?
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ADH (vasopressin), oxytocin, and neurophysins.
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What are neurophysins?
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They are released from the nerve terminals in the pars nervosa. They are thought to be ADH and oxytocin carriers.
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What are Herring bodies?
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Herring bodies are structures found in the posterior pituitary. They represent the terminal end of the axons from the hypothalamus, and hormones are temporarily stored in these locations.
ADH and oxytocin are both stored in Herring bodies |
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What is primary function of the hypothalamus and pituitary?
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The primary function is to maintain homeostasis.
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How does the hypothalamus act as the "master controller"?
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The neurons from the hypothalamus work together with capillary plexuses to deliver neuroendocrine hormones to the two lobes of the pituitary. The hypothalamus delivers neuroendocrine hormones into the primary capillary plexus where they are delivered to the pituitary secretory cells within the pars distalis that then secrete hormones in response into a secondary capillary plexus for distribution to the rest of the body via the hypophyseal vein. This hypophyseal portal system is used by the hypothalamus to regulate hormone secretion in the pars distalis.
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What are the two mechanisms by which the hypothalamic neurons can stimulate hormonal secretion in to the hypophyseal vein?
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They can stimulate the direct release of hormones into the hypophyseal vein by releasing through the posterior pituitary (neurohypophysis).
Or they can stimulate the anterior pituitary (adenohypophysis) to release hormones into the hypophyseal vein by putting releasing hormone from the hypothalamus into the hypophyseal ARTERY as that enters the adenohypophysis. |
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What clue in the names of hormones tells you that they come from the hypothalamus?
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"RH" - or releasing hormone. Those hormones will be released into the hypophyseal artery to stimulate the release of hormones from the pars distalis or pars intermedia of the anterior pituitary into the hypophyseal vein.
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What sort of "releasing hormones" are put into the hypophyseal artery by the hypothalamus?
Where will these hormones be received? |
Thyroid releasing hormone
Somatotropin releasing hormone Corticotropin releasing hormone etc. They will be received by the target cells in the anterior pituitary. |
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Compare the adrenal gland of mammals and that of birds?
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In mammals, the cortex and medulla are distinct.
In birds, they are mixed together. |
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What are the three circulation patterns of the adrenal gland?
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1. subcapsular capillary bed
2. cortical capillary bed 3. medullary capillary bed |
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What embryonic tissue does the adrenal gland develop from?
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The mesoderm (cortex) and neural crest ectoderm (medulla).
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What type of fiber are the adrenal capsules high in?
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Reticular fibers.
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What are the three zones of the adrenal cortex?
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Remember GFR from the outside to the medulla:
zona glomerulosa zona fasciculata zona reticularis |
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What is a characteristic formation of cells in the zona glomerulosa?
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Curved cords (or arcades) of cells in the subcapsular zone (beneath the capsule) in horse, pigs, and carnivores.
Or clusters of cells resembling the glomeruli of the kidney in ruminants and humans. The cells are columnar (humans, horses, carnivores, pigs) or polyhedral in other species. |
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How do cells of the zona glomerulosa stain?
How do their nuclei differ from the zona fasciculata? How do they appear when active? |
Acidophilically. Nuclei are smaller than adjacent zones.
When active, you may see lipid droplets in the cells. |
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Which is the widest zone of the adrenal cortex?
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The zona fasciculata.
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What shape are the cells of the zona fasciculata?
How are they arranged? |
The cells are cuboidal to polyhedral arranged in radial cords separated from adjacent cords by an extensive sinusoidal network.
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How does the more superficial 2/3 of the zona fasciculata differ in appearance from the deeper 1/3?
What is another name for the cells in the more superficial 2/3? |
The more superficial 2/3 has large euchromatic nuclei and very foamy cytoplasm. These cells are called spongiocytes.
The deeper third has cells free of lipids with more basophilic cytoplasm. |
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What is the lipid content of the zona reticularis in comparison to the zona fasciculata?
How do they stain in comparison? What aging pigment is common to the cells of the zona reticularis? |
The cells of the zona reticularis have less lipids, but nuclei and cytoplasm that stains more darkly.
Lipofuscin is the aging pigment common to these cells. |
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What do the three zones of the adrenal cortex secrete?
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Zona glomerulosa - mineralocorticoids and aldosterone
Zona fasciculata - glucocorticoids and cortisol Zona reticularis - sex hormones (DHEA and DHT) |
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What are the "positive" and "negative" efffects of cortisol? Where is cortisol released from? What stimulates that release, and where does the stimulant come from?
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Cortisol causes increased blood glucose, it maintains ECF volume during stress and has signifigant anti-inflammatory properties. On the "not-so-good" side, it depresses the immune system, delays wound healing and increases lipid storage.
Cortisol is released from the zona fasciculata of the adrenal cortex when stimulated by ACTH released from the adenohypophysis. |
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What is the difference between hyperadrenalcorticism and hypoadrenalcorticism?
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Hypoadrenalcorticism (or Addison's) is too little aldosterone in the system resulting in hyponatremia, hyperkalemia, and hypovolemia.
Hyperadrenalcorticism (Kushing's) is too much cortisol in the system resulting in increased lipid storage. |
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What does the medulla of the adrenal gland secrete?
What are these cells called? |
Epinephrine or norepinephrine are released from chromaffin cells.
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How are chromaffin cells of the adrenal medulla polarized?
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One pole opposes a capillary and the other a venule.
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How are the epinephrine and norepinephrine chromaffin-cells arranged in the medulla?
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In most mammals the catecholamine secretors are mixed, but in cattle the central cells secrete norepinephrine and the outer layer secretes epinephrine.
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What part of the brain is the pineal gland a part of?
What type of connective tissue covers it? What are the primary cellular components? |
The diencephalon.
Pia mater covers the pineal gland. Astrocytes and pinealocytes make up the majority of the pineal gland. |
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What are the secretions of the pinealocytes? When are they released?
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Serotonin and melatonin.
Serotonin is released in the light periods and melatonin in the dark periods. |
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What are the normal kinds of structures found in pineal glands? What are the weirdnesses found in there?
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Microfilament, microtubules, dense tubular structures.
Weird things: skeletal muscle, brain sand. |
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What are the four parts of the pancreas?
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Head, neck, body, tail
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What part of the pancreas contains the most islets of langerhans?
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The tail.
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What are the five cell types and their hormones released from the pancreatic islets?
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alpha (glucagon), beta (insulin), delta (somatostatin), PP (pancreatic polypeptide), and gamma (gastrin)
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What do the beta cells of the Islets of Langerhans secrete?
Are the granules alcohol-soluble or insoluble? What percentage of the islets of langerhans are beta cells? |
Insulin.
Alcohol-soluble. 75% |
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Where is proinsulin changed to insulin in beta cells?
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The Golgi apparatus.
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What do the alpha cells of the Islets of Langerhans secrete?
Are the granules alcohol-soluble or insoluble? |
Glucagon
Alcohol-insoluble |
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What stain is used to show alpha and beta cells of the islets of langerhans?
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Gomori's aldehyde fuchsin stain.
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Where are the alpha and beta cells located in the islets of langerhans?
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Alpha cells are on the periphery and beta cells are in the center.
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Which is bigger insulin or glucagon?
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Insulin.
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What do delta cells of the islets of langerhans secrete?
What does the release of this hormone regulate? |
Somatostatin
It regulates both insulin and glucagon secretion. |
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What do PP-cells secrete?
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Pancreatic polypeptides.
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What do gamma-cells secrete from the Islets of Langerhans?
What does over-production of gastrin lead to? |
Gastrin
Hyperplasia leads to Zollinger-Ellison syndrome leading to duodenal ulcers and pernicious anemia. |
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Do the thyroid and parathyroid originate from the same embryologic structure? What do they arise from?
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No.
The thyroid gland arises from the floor of the buccal cavity and the parathyroid from the 3rd (external) and 4th (internal) pharyngeal pouches. [from wiki: pharyngeal pouches form on the endodermal side between the pharyngeal arches] |
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Where is the parathyroid located in relation to the thryoid?
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It depends, the external parathyroid could be on cranial portion of the thyroid, or anywhere down to the level of the thoracic inlet. The internal parathyroid may be nonexistent, embedded within or near the thyroids.
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What species are missing the internal parathyroids entirely?
Will they be paired organs, when present? |
Birds and pigs.
Both the internal and external parathyroid glands are paired when present. |
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What are the capsule and septa of the thyroid made of?
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Capsule - dense irregular CT
Septa - loose CT |
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What type of endocrine gland are thyroid glands?
What are the two main cell types? |
Follicular-type
The two cell types are follicular lining cells (90%) and parafollicular cells (C-cells) |
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What fiber network do C-cells of the thyroid contain?
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C-cells, or parafollicular cells, of the thyroid contain extensive reticular fibers.
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What is the gel-like material inside thyroid follicular cells called? What is it made of?
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Colloid - made of the follicular epithelial secretions, glycoproteins, proteins, enzymes. Main component: thyroglobulin, binding the thyroid hormones.
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How can you differentiate an active follicle cell from an inactive one in the thyroid?
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All of the lining epithelium will be high columnar and the follicles themselves will be smaller - as the contents are being excreted. The colloid will be irregular, with vacuoles and strongly acidophilic.
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How are the C-cells of thyroid glands differentiated?
What do they secrete? What does that hormone do? |
They are located within or next to the lining of the follicle and have pale staining cytoplasm.
They secrete calcitonin, which regulates calcium and phosphorus metabolism. |
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Do the follicular thyroid cells secrete constitutively or periodically?
Describe the mechanics of the secretion? |
Both.
The thyroid hormones (T3 and T4) are secreted constitutively, but stored as colloid. When the TSH signal comes from the pituitary, the colloid is taken up, T3 and T4 cleaved from the thyroglobulin and secreted into the capillaries. |
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Where will you not find the C-cells of thyroid cells?
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Inside the lumen.
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What is the basic function of the thyroid gland?
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Regulate metabolism.
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How is iodine used in the thyroid gland?
Describe the mechanism of its storage. |
It is metabolized to T3 (triiodothyronine) and T4 (tetraiodothyronine) which are bound to thyroglobulin and stored in the colloid.
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What organ regulates the thyroid?
What is hypo/hyperthyroidism? Which occurs mostly in dogs/cats? |
The hypothalamus releases TRH stimulating the pituitary to release TSH.
Hyperthyroidism is seen more in cats, characterized by hyperactivity, weight loss, and poor hair coat - due to excessive stimulation of the thyroid gland by TSH. Hypothyroidism is more common to dogs and is charatcterized by fatigue, low body temp, weight gain and abnormal hair growth. Due to thyroid's inability to respond to TSH. |
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What's the relationship between iodine and goiters?
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Iodine allows T3 and T4 metabolism. These hormones negatively feedback to the hypothalamus asking it to stop releasing the TRH that stimulates the pituitary to release TSH that stimulates the thyroid to release T3 and T4.
If iodine is low, then there isn't enough iodine to make sufficient T3 and T4 to feedback to the hypothalamus and excess TSH is released from the pituitary causing thyroid hypertrophy (goiter). |
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What type of endocrine gland are the parathyroids?
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Cord-type gland
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What type of connective tissue makes up the capsules of the external and internal parathyroid?
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External - dense irregular CT.
Internal - loose CT Both have loose CT septa |
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What structures course with the parathyroid septa?
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Lymph, blood vessels, nerves.
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Are the capillaries and sinusoids of most endocrine organs fenestrated or unfenestrated?
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fenestrated.
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What are the primary cell types of parathyroid glands? Which is more predominant?
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Principal cells and oxyphil cells are the components of the parathyroid tissue. Principal cells are more abundant and can be divided into light and dark cells.
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How are the light and dark principal cells of the parathyroid differentiated?
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They are the same cell type, only in different physiologic states. The light cells are either inactive or exhausted dark cells, and predominant in domestic animals and humans.
The dark cells are active and less frequent, with small nuclei, acidophilic cytoplasm, and secretory granules of PTH. |
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What is the function of PTH?
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Secreted from the active (dark) principal cells of the parathyroid, PTH regulates calcium and phosphorus (with the thyroid).
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What is the entire mechanism of calcium regulation?
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The C-cells of the thyroid release calcitonin. The parathyroid releases PTH.
When calcium is low, PTH is released leading to osteoclast activity, the retention of calcium in the kidneys and increased absorption of it in the intestines. High calcium stimulates calcitonin release that leads to bone formation and the reversal of the other effects by PTH. |
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What are oxyphil cells?
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Cells in the parathyroid glands of cattle, horses, and humans. Large cells with granular, acidophilic cytoplasm (even darker than principal cells), with a small nucleus.
Usually seen in small clusters, they are thought to be derived from principal cells, though their function is unknown. They may be pre-principal cells, like stem cells. |
