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Microanatomy > Endocrine System > Flashcards

Endocrine System Flashcards

1
Q

Endocrine

A

Ductless glands that secrete hormones

Hormones are released from endocrine glands into surrounding tissue fluid and then enter the circulatory system. Circulate within body via bloodstream to affect cells in a specific organ

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2
Q

Hormones (Examples. Can be…)

A

Proteins (Insulin), glycoproteins (LH, FSH, TSH), or polypeptides (oxytocin, prolactin)

Amino Acids: T3, T4; catecholamines (epi and norepi)

Steroids: testosterone, estrogen, progesterone, cortisol, aldosterone

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3
Q

Hormones Path

A

Hormones travel to target cells by bloodstream where most will bind to receptors on target cell surface.
Steroids pass through plasma membrane of target cell and bind the nucleus.
Hormones produce slow sustained response

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4
Q

An endocrine system

A

Stimulus -> endocrine gland -> Hormone -> target tissue -> response

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5
Q

Hormone Functions (endocrine system controls..)

A

Body energy levels and metabolism
Internal balance of body systems (homeostasis)- ions and water balance
Responses to surroundings, stress, and injury
Reproduction
Growth and development

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6
Q

Primary Endocrine Organ

A

First function is to secrete hormones

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7
Q

Primary Endocrine Organ Examples

A
  1. Pituitary gland, hypophysis cerebri
  2. Pineal gland, Epiphysis cerebri
  3. Thyroid gland
  4. Parathyroid gland
  5. Adrenal glands
    Hypothalamus
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8
Q

Secondary Endocrine Organ

A

A secondary function is to secrete hormones

The first function is something else

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9
Q

Secondary Endocrine Organ Examples

A 
Pancreas
Testes
Ovaries
Kidneys
Stomach
Intestines
Thymus
Heart
Placenta
Adipose Tissue
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10
Q

Overview of Major endocrine organ function

A

Growth and development
Internal environment
Energy production, storage, and utilization
Reproduction

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11
Q

Hypothalamus

A

Portion of the brain that links the nervous system to the endocrine system via the pituitary gland/hypophysis

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12
Q

Hypothalamic nuclei

A

Collections of neurons
Control distant cells via hormones in 2 ways:
1. Production of releasing hormones- released into portal system to target cells in the adenohypophysis
2. Hormones axonally transported and stored in the neurohypophysis, then released into the blood to target distant sites (ADH and Oxytocin)

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13
Q

Endocrine Pathway ??/

A

In hypothalamus, releasing hormones are secreted into a portal blood system. They stimulate a variety of cells in the anterior (adenohypophysis) pituitary and secondary hormones released to effect other organs.

OR ADH/oxytocin is produced in nerves and stored in axons extending into the neural lobe of pituitary and is released directly into blood stream

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14
Q

Origin of Pituitary

A

Adenohypophysis: Epithelial- Roof of pharynx
Neurohypophysis: Neuroectodermal (from diencephalon)

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15
Q

Neurohypophysis: Important Portions

A 
Pars Nervosa (Pars posterior, posterior pituitary)
Infundibular stalk (Infundibulum)
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16
Q

Neurohypophysis

A

Cell bodies of large neurons (magnocelluolar neurons) in hypothalamus nuclei produce: ADH (vasopressin) and oxytocin
Their axons comprise the infundibulum and pars nervosa (posterior pituitary)
Swellings along these axons known as herring bodies- where hormones are accumulated

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17
Q

Herring Bodies

A

Swelling along axons in neurohypophysis where hormones are accumulated.

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18
Q

Neurohypophysis- Pars nervosa

A

Axons terminate on vessels and blood then transports hormones to target organs

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19
Q

Oxytocine

A

Causes release of milk
Calf suckling is the stimulus that causes a release of oxytocin from herring bodies into the blood and to the mammary glands. The oxytocin stimulates contraction of myoepithelial cells to let milk down

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20
Q

Adenohypophysis Portions

A

Pars distalis
Pars intermedia
Pars tuberalis

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21
Q

Adenohypophysis- Pars distalis

A 
The bulk of adenohypophysis and secretes majority of hormones
Cells:
Acidophils (red)
Basophils (bluish)
Chromophobes (no color)

Cells in the anterior pituitary are difficult to differentiate.

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22
Q

Adenohypophysis

A

Relative size and orientation depend on species
Require a releasing hormone from hypothalamus
Hypothalamic neurons produce releasing hormones into portal vessels which travel to Adenohypophysis (esp pars distalis) where they stimulate acidophils or basophils to produce another hormone.
The second hormone travels to a target endocrine organ where a third hormone is produced. This will cause an effect on the target organ/cell.

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23
Q

Adenohypophysis- Pars intermedia

A

Source of melanocyte-stimulating hormone (MSH)
Contains large pale cells that produce large molecule POMC which can be sectioned into a number of hormones including endorphins, melanotropins, and lipotropins

Can have an interglandular cleft (remnant of Rathke’s Pouch cavity

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24
Q

Acidophils

A

Found in pars distalis
Somatotropes secrete Growth Hormones
Mammotropes secrete prolactin (lacticotropes)

25
Q

Basophils

A

Found in Pars Distalis
Thyrotropes secrete thyrotropin (TSH)
Gonadotropes secrete FSH, LH
Adrenocorticotropes secrete ACTH

26
Q

Pineal Gland

A

One on each side in brain near middle

27
Q

Epiphysis

A

Main function is to regulate daily rhythms of bodily activity and have pinealocytes that secrete melatonin

28
Q

Pinealocytes

A

Secretory cells in epiphysis. They produce melatonin.

Respond to stimuli detected in the retina; darkness stimulates secretion of melatonin= circadian 24 hour rhythm

29
Q

Melatonin

A

Manufactured by pinealocytes
Mainly secreted at night (in darkness) and is exclusively involved in signaling the time of day and time of year
Effective antioxidant
Immune-enhancing and oncostatic properties

30
Q

Melatonin- Seasonal Breeders

A

Long-day Breeders: Horses. Cycle when days are getting longer: late spring, summer, early fall
Short-day breeders: Sheep, goat, deer, elk. Cycle when days are getting shorter: fall. Anestrus in spring and summer

31
Q

Thyroid Gland

A

Bilateral- one on each side except in dogs where they do not connect

32
Q

Thyroid Gland: Follicles

A

Lining cells produce thyroglobulin which is stored in follicle lumen (colloid) and combined with iodine
Lining cells endocytose thyroglobulin and covert to active T3/T4
Synthesis, iodination, proteolysis of thyroglobulin regulated by TSH

Single layer of cuboidal cells (follicular cells) that secrete into the lumen

33
Q

Thyroid Gland: C cells

A

In between follicular cells and have a neural crest origin.
Parafollicular cells
Secrete calcitonin in response to high blood calcium
Target organs are bone, kidney
Main function is to lower serum calcium
(calcitonIN brings Calcium IN)

34
Q

Parathyroid Gland: location

A

1 internal parathyroid embedded in each thyroid lobe, and 1 external parathyroid beside each lobe.

35
Q

Parathyroid Gland: Chief Cell

A

The endocrine secretory cell

36
Q

Parathyroid Gland: Function

A

Composed of tightly packed chief cells
Secrete parathormone (PTH) into capillaries
PTH increases Ca via effects in SI, bone, kidney. Increased intestinal and renal Ca resorption.
Stimulates osteoclasts for bone resorption

37
Q

Adrenal Gland: Location

A

Above kidneys

Separation between cortex and medulla only seen in mammals

38
Q

Adrenal Gland: Cortex

A

Arises from mesoderm
Secretes steroid: mineralocorticoid, corticosteroids, and sex hormones

Zona Glomerulosa: mineralocorticoids (aldosterone) (typical steroid secreting appearance)
Zona Fasciculata: corticosteroids (cortisol) (Spongiocytes)
Zona reticularis: weak androgens (more cellularly dense) (lipid vacuoles and vascularity)
GFR. Salt, sugar, sex

39
Q

Adrenal Gland: Medulla

A

Arises from neural crest
Secretes catecholamines

Epinephrine&raquo_space; norepinephrine

40
Q

Adrenal Medulla

A

Large sympathetic ganglion, composed of modified neurons with no axons.
Chromaffin cells secrete epinephrin and norepinephrine, stored in secretory granules
Columnar to cuboidal cells, do not have distinct vacuoles

41
Q

Endocrine pathway???

A

Corticotropin-releasing hormone (CRH) exocytosed from hypothalamic neurons, enters primary plexus of portal system, en route to pars distalis

CRH, delivered to corticotrophs by the secondary plexus, binds its GPCR on corticotrophs and signals exocytosis of ACTH

ACTH stimulates zona faciculata

ACTH binds to its GPCR, signaling via cAMP, glucocorticoid synthesis; these hormoens diffuse from cortical cells into peripheral target cells

Release of glucocorticoids and effects a lof of cells: Hepatocytes, adipocytes etc

Glucocorticoids enter cells by diffusion, bine to their cytoplasmic receptor, enter the nucleus, bind to their hormone response element, and effect transcription of responsive genes

42
Q

Pancreas

A 
Has Endocrine and exocrine functions
In fascium near duodeum
Empties into duodeum- exocrine
Endocrine portion produces hormones
Composed of exocrine acinar and endocrine tissue
Exocrine=98%
Endocrine= 2%
43
Q

Pancreas: Islets of Langerhan

A 
Islets of Langerhan have multiple cells types
Alpha: glucagon, CCK, GIP
Beta: Insulin, IAPP
Delta: Somatostatin
Other: Gastrin
44
Q

Gastrointestinal Endocrine Tissue

A

Pyloric region of the stomach secretes gastrin
Enteroendocrine cells in epithelium mucosae of the small intestine secrete hormones such as cholecystokinin (CCK) for gall bladder contraction
Secretin and Gastric inhibitory polypeptide are also secreted by endocrine cells within the small intestine

45
Q

Kidney

A

2 hormones: Renin and Erythropoietin

46
Q

Kidney: renin

A

a hormone and an enzyme
Produced by juxtaglomerular cells (smooth muscle in wall of glomerular afferent arterioles)
secreted in response to decrease in BP in aa. and increase in Na concentration in distal tubule
part of RAAS

47
Q

Kidney: Erythropoietin

A

Produced by interstitial fibroblasts in kidney = O2 concentration
It is a cytokine for RBC precursors
Increase in erythropoiesis is an increase in RBC production

48
Q

Atrial Myocardium

A

Atrial muscle cells contain membrane bound granules that are especially numerous in right atrium
Atrial granules have an endocrine function due to presence of atrial natriuretic peptide (ANP)
Increase stretch of atrial myocytes -> increase ANP -> promotes Na and water loss -> decreased BP
ANP target: distal tubules of kidneys

49
Q

Components of adenohypophysis

A

Pars tuberalis, pars intermedia, pars distalis

50
Q

Components of Neurohypophysis

A

Pars nervosa, infundibular stalk, eminetia mediana

51
Q

Cells of Pars Distalis

A

acidophile (GH, PRL)
Basophils (TSH, FSH, ACTH, LH)
Chromophobes

52
Q

Cells of pars intermedium

A

Secrete melanocyte stimulating hormone

53
Q

Cells of Pars Nervosa

A

Store ADH and oxytocin. Both originate from nuclei in the hypothalamus.

54
Q

Pineal gland secretes what hormone

A

Melatonin

55
Q

Colloid contains

A

thyroglobulin. Converted to thyroxine

56
Q

Follicular lining cells function

A

secretion of thyroglobulin and conversion into thyroxine

57
Q

Clear cell

A

Secretes calcitonin which reduces serum C

58
Q

Chief Cells

A

Part of parathyroid. Secrete parathyroid hormone

Increases serum calcium. Targets bone, intestines, and kidneys

59
Q

Chromaffin Cells

A

Adrenal medulla. Form Neural crest and secrete noradrenaline, and adrenaline

Microanatomy (21 decks)

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