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Histology Of Endocrine Organs Flashcards

1
Q

What are humoral stimuli?

A

Release of hormone controlled by monitoring levels of ions and nutrients in blood and body fluids
Ex. Monitoring Ca levels - release of PTH stimulated by low serum Ca)

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2
Q

What are neuronal stimuli?

A

Release of hormone stimulated by nerve signals

Ex. Release of epinephrine from adrenal gland in response to a signal from sympathetic nerve fibers

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3
Q

What are hormonal stimuli?

A

Release of hormone caused by a hormone secreted into bloodstream by another endocrine organ or cell
Ex. Release of thyroid hormone stimulated by release of TSH from the pituitary

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4
Q

Describe the organization of endocrine glands

A

Endocrine cells are arranged in cords, clusters or follicles and some are found as isolated individual cells
Are derived from epithelium and are epithelioid in nature (lack a free luminal surface)
Well vascularized with capillaries lined with fenestrated endothelium

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5
Q

What are the direct targets of the hypothalamus?

A

Anterior pituitary gland by secreting releasing or inhibiting factors
Kidney and uterus by releasing ADH and oxytocin in the posterior pituitary
Adrenal medulla via sympathetic innervation

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6
Q

What are the indirect targets of the hypothalamus?

A

Hypothalamus releases hormones (collectively referred to as the trophic hormones) that stimulate or inhibit the release of hormones from the anterior pituitary
Indirectly influences other endocrine organs by stimulating secretion of hormones by the anterior pituitary gland
Ex include hypothalamic hormones that stimulate release of TSH, somatotropin, ACTH, FSH and LH, prolactin and MSH from anterior pituitary

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7
Q

What is the embryological origin for the pituitary gland?

A

Anterior pituitary - from an ectoderm diverticulum that forms a vesicle called Rathke’s pouch and this ouch translocates towards and joins the developing infundibulum of the diencephalon
Posterior pituitary and infundibular stalk - from infundibular diverticulum of the diencephalon of the brain

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8
Q

What is the anterior pituitary gland composed of?

A

Glandular epithelial cells controlled by neurohormones released from hypothalamus
Includes the pars distalis (anterior most lobe of the pituitary), pars intermedia (intermediate lobe) and pars tuberalis (wraps around infundibular stalk)

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9
Q

What is the posterior pituitary composed of?

A

Axons from hypothalamus and support cells
Axons carry ADH and oxytocin for storage and release in posterior pituitary
Includes pars nervosa (posterior lobe), median eminence (base of the hypothalamus), and infundibular stalk (thin portion extending down from the eminence)

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10
Q

What are the major cell types in the anterior pituitary gland?

A

Somatotropin cells, thyrotropic cells, corticotropic cells, gonadotropic cells and mammotropic cells

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11
Q

What do somatotropin cells secrete?

A

GH

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12
Q

What do thyrotropic cells secrete?

A

TSH regulating thyroid gland secretion

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13
Q

What do corticotropic cells secrete?

A

ACTH and melanocyte stimulating hormone (MSH)
ACTH stimulates adrenal cortex to secrete stress related hormones and mediate metabolism
MSH stimulates melanocytes to produce melanin

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14
Q

What do gonadotropic cells secrete?

A

FSH and LH that act on the gonads

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15
Q

What do mammotropic cells secrete?

A

Prolactin which stimulates milk production

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16
Q

What cells comprise the pars distalis of the anterior pituitary?

A

Acidphils, basophils, chromophores (unknown function) and sinusoidal (fenestrated) capillaries

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17
Q

Which cells are acidphils?

A

Somatotrophs (GH) and mammotrophs (prolactin)

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18
Q

What cell types are basophils?

A

Corticotrophs (ACTH), thyrotrophs (TSH) and gonadotrophs (LH and FSH)

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19
Q

Describe the pars nervosa

A

Continuous with median eminence of the hypothalamus via infundibular stalk
Does not manufacture hormones rather stores and releases them from axon terminals

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20
Q

What does the pars nervosa consist of?

A

Hypothalamus unmyelinated axons (contain Herring bodies which are expanded axonal terminals storing ADH and oxytocin)
Pituicytes (glia-like) supporting the nerve fibers
Fenestrated capillaries

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21
Q

What is the function of ADH?

A

Targets the kidney and regulates Na and water retention

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22
Q

What is the role of oxytocin?

A

Targets uterine smooth muscle and stimulates lactation

Induces brith and may be involved in sexual arousal and pair and social bonding

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23
Q

Describe the hypothalamic portal system

A

Responsible for delivery of hypothalamic trophic hormones to the anterior pituitary
Hypothalamic neurons secrete hormones and the capillary plexus supplying it takes up the released hormones
Venous capillaries carrying the hormones then drain into the hypothalamic portal veins leaving the hypothalamus
Hypothalamic portal wins enter ant pit and break up into capillary plexus where they signal ant pit cells
Ant pit releases hormones into the same surrounding capillary plexus that then drains into the pituitary veins and enters the systemic circulation

24
Q

Describe the pineal gland

A

Out pocketing of diencephalon’s roof of 3rd ventricle
Flattened and cone shaped covered with pia mater
Role in growth, development and circadian rhythms
Synthesizes melatonin and serotonin

25
What does the pineal gland consist of?
Pinealocytes and neuroglia Calcified granular material (brain sand) - ca phosphate crystals located in the intercellular spaces that show up beginning early childhood; important radiogenic marker (for midline brain); secreted by pinealocytes
26
Describe the microscopic anatomy of the thyroid gland
Characterized by structures called follicles consisting of a layer of follicular cells (simple cuboidal to columnar epithelium) surrounding a fluid called colloid Colloid contains thyroglobulin (a storage form of T3 and T4)
27
What is the only gland to store a hormone outside of the cell?
Thyroid gland
28
Thyroid hormones control what?
Basal metabolism, O2 usage, body temp, etc
29
Describe the synthesis and turnover of thyroid hormones
Generated and stored extracellularly as thyroglobulin Thyroglobulin synthesized in rER, glycosylated in golgi and secreted by exocytosis into the lumen of follicle (colloid) Thyroglobulin is iodinated at the apical surface forming T3 and T4 TSH stimulates internalization of thyroglobulin via endocytosis where it is degraded freeing T3 and T4 T3 and T4 are released from the basal surface of the follicle cells into the circulation
30
What are parafollicular C cells?
Lie just outside the follicles Secrete calcitonin when blood levels of Ca are high Lower circulating Ca levels by stimulating secretion by kidneys, decreasing the Ca releasing activity of osteoclasts and increasing osteogenesis by osteoblasts
31
What is Graves’ disease?
Abnormal Abs stimulating TSH receptors causing over secretion of T3 and T4 Sx: elevated metabolism, sweating, rapid HR, weight loss, eye balls may protrude May need thyroidectomy or anti-thyroid drugs More common in women
32
What is hypothyroidism?
Insufficient T3 and T4 production Often an autoimmune disease causing follicle cell death Sx: low metabolic rate, weight gain, lethargy, chilliness, edema, mental sluggishness Treated with synthetic T3 and T4
33
What are goiters?
Thyroid enlargement most commonly due to iodine deficiency | Follicle cells keep producing thyroglobulin but cannot iodinate it to make TH
34
What are the parathyroid glands?
Small ovoid glands (usually two pairs) lying on the posterior surface of the thyroid gland that release PTH Major importance in regulating serum Ca and phosphate levels Blood supply to the parathyroid glands is similar to the thyroid
35
What cells are within the parathyroid glands?
Chief (principle) cells and oxyphil cells (function unknown but increase with age)
36
What are chief (principle) cells?
Located in the parathyroid glands and release PTH Secretion occurs when the blood concentrations of Ca falls below the normal range of 9.5-10.5 mg/dL Secretion stops when the level of Ca returns to normal
37
Describe the Ca regulation that occurs by PTH
PTH released from chief/principle cells when blood levels drop below 9.5mg/dL Stimulates osteoclasts to resorb bone and release its Ca stores, increase Ca retention by the kidneys, stimulates kidney to convert an inactive form of vitamin D to calcitriol (active form) which then increases Ca absorption by the intestines Blood Ca levels increase and then inhibit further PTH release
38
Describe the adrenal cortex
Distinctive yellow color due to lipids in its cells | Divided into structurally and functionally 3 zones including the zona glomerulosa, zona fasciculata, zona reticularis
39
Describe the zona glomerulosa
Mineralocorticoids Influence Na and K levels (salt) Aldosterone is released from this layer
40
What is the function of aldosterone?
Targets kidney function Mostly secreted in response to low BP or blood volume Controlled by renin-angiotensin system
41
Describe the zona fasciculata
Glucocorticoids like cortisol Influence glucose metabolism and immune system Released under the control of ACTH from the anterior pituitary
42
What is the function of cortisol?
Deals with stress and mediates glucose metabolism Serves as negative feedback mechanism to the immune system (anti-inflammatory action) Released primarily by the zona fasciculata but also the zona reticularis
43
Describe the zona reticularis
Androgens | Influence secondary sex characteristics
44
Describe the adrenal medulla
Forms the inner core of each adrenal gland Primarily consists of clusters of large spherical cells called chromaffin cells (target of presynaptic sympathetic neurons)
45
Describe what occurs when the adrenal medulla is stimulated by the sympathetic NS
When stimulated by the sympathetic NS one population of cells primarily secretes the hormone epinephrine (adrenaline) and a second population primarily secretes the hormone NE (noradrenaline) These hormones work with the sympathetic NS to prepare the body for an emergency or fight or flight situation
46
What is Addison’s disease?
Hyposecretory disorder usually in both glucocorticoids and mineralocorticoids Blood glucose and Na levels drop and there is severe dehydration and low BP along with fatigue and loss of appetite Causes include autoimmune disease or due to an inherited metabolic disease leading to deficiencies in hormone producing enzymes
47
What is Cushing’s syndrome?
Due to hyper secretion of glucocorticoids because of either an ACTH secreting pituitary tumor or a tumor in the adrenal cortex Characterized by high serum glucose levels, protein loss in muscles, muscle weakness, depressed immune system and lethargy
48
What are some sx of Cushing’s syndrome?
Swollen face, fat redistribution (buffalo hump and moon face), high glucose levels, weight gain, sweating, thinning skin, muscle weakness, lethargy, depression of immune and inflammatory responses
49
Describe the exocrine portion of the pancreas
Makes up most of the gland Aids in digestion Exocrine cells are organized in structures called pancreatic acini
50
Describe the endocrine portion of the pancreas
Endocrine cells are organized into clusters called pancreatic islets or islets of Langerhans The islets are scattered amongst the exocrine cells
51
What cells make up the pancreas?
Alpha, beta, delta and F-cells
52
What are alpha cells?
Secrete glucagon when blood glucose levels drop | Stimulates release of glucose from liver glycogen stores
53
What are beta cells?
Secrete insulin when blood glucose levels are elevated | Promotes glycogen storage in the liver and entry into cells
54
What are delta cells?
Secrete somatostatin slowing the release of insulin and glucagon thereby controlling the rate of nutrient entry into the bloodstream and cells Regulates several digestive related hormones Stimulated by high levels of nutrients in bloodstream
55
What are F cells?
Secrete pancreatic polypeptide that inhibits the release of somatostatin Has a role in appetite regulation
56
Describe pancreatic blood supply
The pancreas has two arterial capillary flows: one entering the islets and the other supplying the pancreatic acinar cells hence providing arterial blood separately to the endocrine and exocrine portion of the gland Venous capillaries draining the islets flow over the acinar cells to apply local action of islet hormones more directly to the exocrine cells of the pancreas

NE Exam 3 (16 decks)

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