Endocrinology Flashcards
What are three characteristics of glands? (3)
All glandular tissue is derived embryologically from epithelium
Glandular epithelium describes specialized cells that synthesize, store and secrete chemical substances
Two types: exocrine and endocrine
How are both endocrine and exocrine glands made?
Epithelium lines the surface of cavities and then it invaginates into the connective tissue.
It then forms a duct with deep secretory cells collected at the base and secretes fluid to the surface which is exocrine
The other form is it detaches from the epithelium and develop around a sinusoid with a blood vessel and then secrete into the blood vessels
What are the characteristics of exocrine glands? (2)
Release their secretions into ducts that carry the secretions to the body surface
Eg. sweat, mammary, salivary
What are characteristics of endocrine glands? (4)
Release their secretions into sinusoids (large extracellular spaces)
Sinusoids pass secretions to the capillaries
Circulatory system then carries the secretions to the intended target site (as well as to the rest of the body)
Eg. thyroid, pituitary, adrenal (suprarenal)
What is the endocrine system? (3)
The collection of glands and tissues of the body that secrete chemical messengers into the blood and interstitial fluid
Integrates the activities of the organs and organ systems throughout the body
The nervous and endocrine systems function together to maintain homeostasis
What is neuroendocrinology? (3ish)
Close association between endocrine and nervous system
Brain regulates secretion from endocrine glands and hormones modify CNS function
Nerve cells and gland cells are similar: secrete chemical messengers that act on target cells, electrical activity, secrete hormones that enter vascular system, release similar substances (dopamine, NE, somatostatin) and can act as neurotransmitter, neural hormone, classic hormone
What are the characteristics of the nervous system? (what are the responses, 2 types of responses)
Produces responses that are: highly specific, act over the short term (ms to minutes)
Responses generated by neurons: signals are electrical impulses along axons, chemical messengers conduct the impulse between neurons
What are the characteristics of the endocrine system? (what are responses, responses produced by)
Produces responses that: mkay affect different tissues and organs simultaneously, act over long duration (min to day)
Responses produced by hormones: signals are chemical substances, released by endocrine glands, circulate in bloodstream throughout the body
What is a hormone? (4)
A hormone is a chemical messenger
Is produced and secreted by endocrine cell or tissue
Travels through the circulatory system to reach other tissues
ACts upon specific target cells within the tissue
What are hormone actions (3)?
Bind to specific cellular receptors
Presence/absence of a receptor determines the cells response to a hormone
Changing the number of receptors changes the cells sensitivity to the hormone
What are the endocrine glands and tissues? (9 glands, 4 tissues)
Hypothalamus (controls pituitary)
Pituitary gland (master gland, outside brain)
Pineal gland
Parathyroid glands
Thyroid gland
Thymus
Adrenal gland
Pancreas
Gonads
Tissues: digestive tract, kidneys, heart, adipose tissue)
Where is the pituitary and what are the parts of it?
Sits below the hypothalamus and third ventricle
Infundibulum is the pituitary stalk that feeds into it
Anterior lobe: adenohypophysis, glandular tissue
Posterior lobe: neurohypophysis, axon bundle
Turkish saddle: bony depression protected by dura
How did the pituitary develop?
Neurohypophyseal bud and the Hypophyseal pouch (Rathke) grow and wrap around each other, oral cavity epithelium invaginates into hypophyseal pouch
Infundibulum comes from the NHP
What are the hormones that come from the anterior pituitary and what do they each do? (6)
Human growth hormone (hGH): stimulates body growth and metabolism
Thyroid stimulating hormone (TSH): controls thyroid fxn
FSH/LH: control secretion of sex hormones and production of gametes
Prolactin (Prl): stimulates milk production
Adrenocorticotropic hormone (ACTH): controls hormone secretion by adrenal cortex
Melanocyte stimulating hormone (MSH): stimulates melanin release
What are the hormones coming from the posterior pituitary? (2) What are their functions?
Vasopressin (antidiuretic hormone, ADH): regulates concentration of urine, regulation of BP
Oxytocin: stimulates uterine muscle contraction during childbirth and release of milk from mammary glands
What does the hypothalamus do in relation to the anterior and posterior pituitary?
Anterior: secretion of regulatory hormones to control activity of anterior pituitary, and hormones secreted from AP control other endocrine organs
Posterior: production of oxytocin and ADH in the hypothalamus and then release from PP
What is the hypothalamic-hypophyseal portal system?
Superior hypophyseal artery: comes into primary capillary bed in the infundibulum
Primary capillary plexus: carries regulatory hormones from hypothalamus to secondary plexus to exert release of hormones in anterior pituitary
Portal veins: connect primary and secondary plexus in AP
Hypophyseal veins: carry all hormones from AP and PP to body
Inferior hypophyseal artery: goes to posterior pituitary to the synapse of axons to give oxytocin and ADH
Paraventricular nucleus/ supraoptic nucleus: produce the PP hormones, oxytocin and vasopressin respectively
What are the objective of the hypothalamus?
Secretes releasing (hypophysiotropic) factors that act on cell of the AP
Hormones of the PP produced in supraoptic nucleus (ADH) and paraventricular nucleus (oxytocin) and these neurons extend inferiorly to end at PP where they release ADH/Oxy
Feedback loops: positive and negative
What are the positive and negative feedback loops of the endocrine tissue?
Positive: releasing hormone (TRH) from hypothalamus then stimulating hormone from the pituitary (TSH) to the target organ/ tissue (thyroid gland- thyroxine)
Then the hormone from the target organ/tissue feedback to the pituitary and hypothalamus to inhibit their release
Where is the thyroid gland and what is the structure?
Sits under cricoid cartilage of larynx and thyroid cartilage, has right and left lobe, sits in the front of the neck in front of trachea
Has thyroid follicles, and thyroglobulin is stores in the colloid of the follicle, and used to make T3 and T4
TSH acts on thyroglobulin to make T3/4 by adding iodine
How are thyroid hormones produced? (6)
Follicle cells secrete hormone precursor called thyroglobulin into follicle cavity
Iodine is added to thyroglobulin in the cavity
When stimulated by TSH, follicle cells convert thyroglobulin to thyroid hormones T4 and T3
Follicle cells secrete T3/4 into connective tissue between follicles
Hormones picked up by capillaries
Thyroid hormones regulate metabolism
What do the parafollicular cells do? (3)
Follicles contain parafollicular cells (C-cells)
Produce the hormone calcitonin
Function in calcium regulation
Where is the parathyroid gland?
Within the thyroid, 4 small glands 2 on each wing, 2 superior and 2 inferior
What is the role of the parathyroid glands? (2)
Secrete parathyroid hormone from principle cells
Function in calcium regulation
What are the thyroid and parathyroid hormones? What do they do? (3)
Thyroid hormones T3 and T4: stimulate O2 use, basal metabolic rate, cellular metabolism, growth and development
Calcitonin: decreases Ca+ in body fluids, increase Ca+ deposition in the bones
Parathyroid hormone: increases Ca+ in body fluids and decreases Ca+ deposition in bones
What are the suprarenal (adrenal gland)?
Glands that sit on top of the kidneys, lots of arteries feed into it and one vein leaves, has the cortex and the medulla
What are the hormones of the adrenal cortex? (3)
Mineralocorticoids: increase renal absorption of Na+ and H2O, decrease renal absorption of K+ (aldosterone)
Glucocorticoids: stimulates protein, lipid and carb metabolism and anti-inflammatory (cortisol)
Androgens: stimulates growth of axillary and pubic hair, stimulates libico
How does the sympathetic nervous system communicate with the adrenal glands?
From spinal cord, THROUGH the sympathetic ganglion without synapse, then go to the adrenal gland via splanchnic nerves and synapse on the chromaffin cells for a fast sympathetic response
What are the hormones of the adrenal medulla? What do they do?
Epi and NE: fight or flight, increase cardiac output, increase BP, increase blood glucose, effect release of lipids from adipose tissue
What is the structure of the pancreas? (2)
Has endocrine and exocrine functions
Against the small intestine and pancreatic duct sends hormones made here to the SI via accessory pancreatic duct
What are the internal structures of the pancreas? (2)
Exocrine pancreas
Islet: endocrine, cell groupings with capillaries that carry endocrine hormones to vasculature
What is contained within a pancreatic islet? (5)
Blood capillaries
Exocrine acinus
Alpha cell: release glucagon
Beta cell: release insulin
Delta cell: release somatostatin
What are the pancreatic hormones and what do they do? (3)
Glucagon: stimulates glucose synthesis, elevates blood glucose, mobilizes lipid reserves
Insulin: stimulates lipid and glycogen synthesis/ storage, stimulates glucose uptake by cells, decrease blood sugar
Somatostatin: inhibits secretion of glucagon and insulin
What is diabetes mellitus? (3)
Inability to produce or use insulin, elevation of blood glucose levels and excretion of glucose in urine
Results in: cardiovascular problems, vision problems
Two types: Type I (10%), Type II (90%)
What are some characteristics of Type I diabetes? (4)
Autoimmune disease that destroys insulin secreting cells of islets
Marked reduction in insulin levels
Called insulin dependent diabetes
Can occur at any age but is more common between ages of 5-20
What is Type II diabetes?
Combination of insulin resistance and insulin secretory defects
Target cell become less sensitive to insulin (due to down regulation of receptors)
Called non-insulin-dependent diabetes
Correlates with age and obesity
Initial management by diet, exercise, and weight loss
What are the three other endocrine glands?
Gonads (testes, ovaries), Pineal gland, Thymus gland
What is the role of the pineal gland? (2)
Physiological role unclear
Secretes melatonin and regulates biological clock
What is the structure/role of the thymus gland?
STructure: looks like oatmeal early in life and fat later
Produced T-lymphocytes: function in cell mediated immunity
Secretes thymic hormones: promote proliferation and maturation of T lymphocytes
What are hormones of other organs/ tissues?
GI tract: >20 different hormones, regulate activity of GI tract and digestive glands
Kidneys: erythropoietin increases RBC production, renin increases BP
Heart: atrial natriuretic peptide decreases BP
Adipose tissue: leptins are appetite suppressant
