Endocrine System Flashcards Preview

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Flashcards in Endocrine System Deck (76):
1

Glands in which ducts carry secretions to surface or organ cavity and have extracellular effects such as food digestion

Exocrine Glands

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Glands without ducts which secrete hormones into tissue fluids, capillary networks and the bloodstream

 

Endocrine Glands

Secretions have intracellular effects, altering cell metabolism

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What is the general function of the endocrine system?

Controlling and integrating the function of other organ systems via hormones

4

What is the difference in nervous vs. endocrine communication?

nervous - electrical and chemical signals

endocrine - chemical signals only

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What is the difference in nervous vs. endocrine response speed and effect persistence?

nervous - quick reaction (milliseconds), effect stops quickly

endocrine - slow reaction (seconds to days), effect may continue for weeks

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What is the difference between nervous vs. endocrine adaptation to long-term stimuli?

nervous - adapt quickly and response declines

endocrine - response persists

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The 3 Main Endocrine System Components

- Endocrine Glands

- Hormones

- Target Cells

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Hormone

- a chemical "messenger" molecule secreted into the bloodstream which stimulates a response in another tissue or organ

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Target Cells

- cells with receptors for a certain hormone

(ex: thyroid cells are target cells for TSH secreted by the anterior pituitary)

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Receptor Site

the site on a cell membrane or in its cytoplasm/nucleus to which a hormone binds

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Three Types of Endocrine Glands

1. Pure endocrine

2. Endocrine/exocrine (mixed)

3. "Neuroendocrine" glands

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Pure Endocrine Glands

- thyroid

-parathyroid

- adrenal cortex

- thymus

- pineal gland

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Endocrine/Exocrine (Mixed) Glands

- pancreas

- ovaries

- testes

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"Neuroendocrine" Glands

- Adrenal medulla

- Hypothalamus

- Posterior pituitary

 

- contain specialized nervous cells which produce hormones

 

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Hypothalamus

- directly below thalamus in diencephalon

- composed of several groups of nuclei ( neurons & neuroglia)

- regulates anterior pituitary hormones

- sends ADH and Oxytocin to posterior pituitary for storage and future release

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What is this entire structure?

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Pituitary Gland (AKA Hypophysis)

- sits in sella turcica of sphenoid bone

- attaches to hypothalamus via the infundibulum

- secretes nine homeostatic hormones

- two lobes: Adenohypophysis (Anterior, "adeno" = glandular) and Neurohypophysis (Posterior, "neuro" = neural)

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What is #4 and what hormones does it secrete?

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Anterior Pituitary (AKA Adenohypophysis)

- releases 7 hormones:

  • Growth Hormone (GH)
  • Prolactin (PRL)
  • Thyroid-stimulating Hormone (TSH)
  • Adrenocorticotropic Hormone (ACTH)
  • Melanocyte-Stimulating Hormone (MSH)
  • Follicle-Stimulating Hormone (FSH)
  • Luteinizing Hormone (LH)

 

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What is #6 and what hormones does it secrete?

Posterior Pituitary (AKA Neurohypophysis)

- Secretes 2 hormones:

  • Anti-diuretic Hormone (ADH)                 (AKA Vasopressin)
  • Oxytocin

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What is the fancy latin name for #4?

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pars distalis

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What's the fancy latin name for #6?

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pars nervosa

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A general name for hormones that stimulate other endocrine glands and the 4 of them secreted by the anterior pituitary

Tropic Hormones

  • TSH
  • ACTH
  • FSH
  • LH

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A general name for hormones that stimulate the gonads and the two secreted by the anterior pituitary

 

gonadotropins
  • FSH
  • LH

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follicle-stimulating hormone

- stimulates production of egg or sperm cells

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Luteinizing Hormone

- stimulates hormone production

males - stimulates interstitial teste cells to secrete testosterone

females - stimulates ovulation and corpus luteum to secrete progesterone and estrogen

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Thyroid-Stimulating Hormone

- stimulates growth of thyroid gland and secretion of TH

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Adrenocorticotropin Hormone

- regulates stress response by stimulating adrenal cortex

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Prolactin

females - stimulates milk synthesis after childbirth

males - increases LH sensitivity, thus increasing testosterone secretion

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Growth Hormone

AKA Somatotropin

- promotes tissue growth

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Melanocyte Stimulating Hormone

- involved in skin pigmentation

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How does the hypothalamus regulate the adenohypophysis?

Via releasing and inhibiting hormones sent through the hypothalamo-hypophyseal portal system

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What is a portal system?

- a system in which blood moves from organ to organ without first passing through the heart

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What is #9?

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Primary capillaries

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What is # 2?

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Portal Venule

- between hypothalamus and adenohypophysis

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What is part #4?

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Secondary capillary bed

(in adenohypophysis)

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What is #6? And what hormones does it secrete?

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Posterior Pituitary (AKA Neurohypophysis)

- secretes two hormones: ADH and Oxytocin

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ADH

Anti-Diurectic Hormone (AKA Vasopressin)

- produced in hypothalamus, sent to neurohypophysis, secreted from there

- targets kidneys to increase water retention, reduce urine and increase blood pressure

- functions as neurotransmitter

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Oxytocin

- produced in hypothalamus, sent to neurohypophysis, secreted from there

- stimulates lactation and labor contractions

- possible role in sperm transport and emotional bonding

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How does the hypothalamus communicate with the posterior pituitary?

Via the hypothalamo-hypophyseal tract, a neural connection between the two glands

- neuron cell bodies in the hypothalamus transport ADH and oxytocin via their axons to a capillary bed in the neurohypophysis

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thyroid gland

- the largest endocrine gland

- secrete thyroid hormones which increase metabolic rate, etc.

- located anterior and laterally to trachea, inferior to larynx

- two lobes connected by the isthmus

- bulbous inferiorly, tapered superiorly

 

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the central part connecting the two sides of this gland

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Isthmus of the thyroid gland

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#1 (whole structure, not just cells lining it)

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Thyroid Follicle

- microscopic pockets within thyroid filled with colloid and lined with simple cuboidal epithelial cells which release T3 and T4

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What are the thyroid hormones and what do they do?

T3 (tri-iodothyronine) and T4 (thyroxine)

  • increase metabolic rate and O2 consumption
  • increase heat production via calorigenic effect
  • increase heart rate and contraction strength
  • increase respiratory rate

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#2 (the liquid within, not the structure)

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Colloid, AKA thyroglobulin

- fluid within thyroid follicles containing precursors to thyroid hormones

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#4

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Parafollicular Cells (AKA Calcitonin or C Cells)

- found between cuboidal follicular cells

- produce calcitonin

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Calcitonin

- hormone produced by parafollicular cells of thyroid

- Decreases blood Ca2+, promotes Ca2+ deposition and bone formation (via osteoblast activity)

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square cells lining circular structures here:

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follicular cells

- simple cuboidal epithelium

- produce thyroid hormones

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green structure

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Pineal Gland (or body)

- located in the posterior roof of the diencephalon

- produces melatonin, which regulates sleep cycles

- may play a role in the onset of puberty

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Small, pinto bean-like structures on the surface of the larger structure. (Posterior view)

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Parathyroid Glands

- located on posterior surface of thyroid

- usually 4, up to 8

- produce parathormone (PTH) in their chief cells

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Parathormone

AKA Parathyroid hormone or parathyrin

- secreted by chief cells of parathyroid

function:

  • increase blood Ca2+ levels
  • promotes synthesis of calcitriol (active form of vitamin D), thereby...
  • increasing digestive absorption of Ca2+
  • decreasing urinary excretion of Ca2+
  • increasing bone resorption (via osteoclasts)

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Calcitriol

- active form of vitamin D synthesized in the kidney when stimulated by PTH

- increases Ca absorption and bone resorption, decreases Ca excretion, thus increasing blood Ca

- opposes action of Calcitonin from parafollicular cells of thyroid

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What is the left structure composed of more densely packed cells? And what are its cells called?

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parathyroid gland

chief cells - synthesize parathormone

 

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The top, unlabeled lumpy structures

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Adrenal Glands

- triangular gland embedded in adipose tissue on superior surface of kidneys

- almost entirely sympathetic innervation

- "two glands in one" - adrenal medulla deep to adrenal cortex

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pink interior portion of magnified gland

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adrenal medulla

- neuroendocrine tissue

- Chromaffin Cellsmodified postganglionic sympathetic cells division of ANS

- create and secrete Epinephrine, Norepinephrine and some Dopamine

- exception to long postganglionic axon rule in sympathetic ANS, preganglionic sympathetic fiber runs into medulla

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epinephrine and norepinephrine

- hormones produced and secreted by Chromaffin cells of the adrenal medulla

- have some different effects but generally contribute to fight-or-flight response:

  • increase heart rate and BP
  • constrict skin and GI blood vessels
  • dilate smooth muscle
  • increase metabolism

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distinct layer of more randomly arranged cells in right half of image sandwiched between two layers of cells arranged in strands

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adrenal medulla

(chromaffin cells in spherical clusters)

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Chromaffin Cells

- cells of the adrenal medulla which synthesize epinephrine or norepinephrine

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Outer layer of gland indicated by pointer

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adrenal cortex

- glandular tissue of adrenals

- makes up bulk of adrenal gland

- secretes corticoid hormones

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The 3 Types of Corticoid Hormones, Where They Are Synthesized and Examples of Each

  1. Mineralocorticoids from the Zona glomerulosa, specifically Aldosterone
  2. Glucocorticoids from the Zona Fasciculata, specifically Cortisol
  3. Gonadocorticoids from the Zona Reticularis, specifically androgens and testosterone

 

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#2

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Zona glomerulosa of adrenal cortex

- round arrangements of cells

- make mineralocorticoids, ex: aldosterone

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#3

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Zona Fasciculata

- middle, largest layer of adrenal cortex

- parallel cords of lipid-rich cells

- appear "bubbly" and usually stain lighter than other layers

- creates glucocorticoids, ex: cortisol

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#4

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zona reticularis

- innermost cortical layer next to adrenal medulla

- narrow band of small, branching cells

- produce gonadocorticoids, ex: androgens/testosterone

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yellow-white structure extending rightward from the duodenum:

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Pancreas

- just inferior to stomach in posterior wall of ab. cavity

- mixed exocrine/endocrine gland

- exocrine cells produce digestive enzymes

- endocrine cells grouped into Islets of Langerhans, which secrete hormones including:

  • Glucagon
  • Insulin
  • Somatostatin
  • Pancreatic polypeptide

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Glucagon

- secreted by alpha cells of pancreatic islets

- signals the liver to break down glycogen into glucose

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Insulin

- secreted by beta cells of pancreatic islets

- signals cells to take up glucose, controls blood sugar levels

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Somatostatin

- released by delta cells of pancreatic islets

- decreases insulin & glucagon release

- decreases growth hormone release

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Pancreatic Polypeptide

- secreted by F cells (AKA PP cells) of pancreatic islets

- decreases pancreatic exocrine activity

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cluster of lighter cells in the middle

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Pancreatic Islet (AKA Islet of Langerhans)

- groupings of endocrine cells within the pancreas

- five kinds of cells:

  • alpha cells (glucagon)
  • beta cells (insulin)
  • delta cells (somatotropin)
  • F cells (pancreatic polypeptide)
  • epsilon cells (ghrelin)

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leftmost dark pink area

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anterior pituitary

- densely packed cells

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middle lighter pink area marked PN

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posterior pituitary (pars nervosa)

- unmyelinated axons + neuroglia

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#4

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Thymus

- produces hormones thymopoietin and thymosins which regulate development and maintenance of immune function

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paired almond-shaped organs on either side of uterus

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Ovaries

- primary female sex organ

- located retroperitoneally in abdomen, lateral to uterus at proximal end of fallopian tubes

- produce female sex hormones estrogen and progesterone and contain ova

 

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Testes

- male sex organ located in scrotum

- secrete androgens (testosterone) and inhibin 

- produces sperm cells

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Female gametes surrounded by estrogen-producing cells

Follicles

- eggs surrounded by granulosa cells

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smaller cells surrounding large central cell

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Granulosa Cells

- cells within ovaries that produce estrogen

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