Endocrinology Flashcards
Glandular epithelium describes specialized cells that _______, _______ and ________ chemical substances.
- synthesize
- store
- secrete
2 types of glandular tissue
- exocrine
- endocrine
The secretory cells of exocrine glands are found _________ in relation to the epithelium.
Secretory cells are found in line with the epithelium (exocrine gland). This creates a duct (small divot) in the tissue.
Secretory cells of endocrine glands are found ________ in relation to the epithelium.
Secretory cells are found BELOW epithelium, within connective tissue. A bundle of secretory cells are fed via sinusoid.
Examples of exocrine glands.
release secretions into ducts, carried to body surface
- sweat
- mammary
- salivary
Endocrine secretion process.
secretory cells > sinusoids > capillaries > systemic vasculature > target site/ entire body
Examples of endocrine glands.
- thyroid
- pituitary
- adrenal (suprarenal)
The endocrine system works to secrete chemical messengers into the body’s _______ and ________.
- blood
- interstitial fluid
The nervous and endocrine systems function together to _______ ________.
maintain homeostasis.
What is the function of neuroendocrinology?
Brain regulates secretion from endocrine glands. Hormones modify CNS function.
How are nerve and gland cells similar (4)?
- secrete chemical messengers acting on target cell
- electrical activity
- secrete hormones enter vascular system
- similar secretions (neurotransmitters, hormones)
What responses are generated by neurons in the nervous system?
- chemical messengers conduct impulse [released into cleft] b/n neurons > post-synaptic membrane > electrical impulse conducted along axons > next neuron in chain
Target sites and duration for nervous system responses.
- high specific target
- short term (milliseconds to mins)
What responses are generated by hormones in the endocrine system?
endocrine glands > chemical substances > circulate in bloodstream
Target sites and duration for endocrine system responses.
- may affect diff tissues + organs simultaneously
- longer duration (mins to days)
What is a hormone?
- chemical messenger
- produced/ secreted by endocrine cell, tissue
- travels thru circulatory system
- acts upon specific target cells within tissue (binds to receptor)
How do you increase the sensitivity to a specific hormone?
Increase number of receptors in target cell. Presence/ absence of receptor determines cell’s response to hormone
The pituitary gland is also known as the _________.
hypophysis
How well protected is the pituitary gland?
VERY well protected - anchored into floor of cranium, infundibulum leads towards the gland within a depression of the bone. Protected by dura mater.
What is the infundibulum?
Pituitary stalk - leads down to pituitary gland from hypothalamus (nestled in bone).
What is the anterior lobe of the pituitary gland called?
Adenohypophysis
What is the posterior lobe of the pituitary gland called?
Neurohypophysis
What is a sinusoid?
large, extracellular spaces - endocrine glands release secretions into - passed to capillaries
6 anterior pituitary hormones
- human growth hormone (hGH)
- thyroid stimulating h. (TSH)
- follicle stimulating h. (LSH)/ luteinizing h. (LH)
- prolactin (Prl)
- adrenocorticotropic h. (ACTH)
- melanocyte stimulating h. (MSH)
2 posterior pituitary hormones
- vasopressin aka antidiuretic hormone (ADH)
- oxytocin
Where does the production of regulatory hormones secreted by the anterior/ posterior pituitary occur?
In hypothalamus –> travels downwards through pituitary to influence cells (hypothalamic-hypophyseal portal system)
What is the hypophyseal portal system?
System of blood vessels connecting hypothalamus w/ adenohypophyseal -
transport + exchange of hormones to allow fast communication b/n glands
What does the posterior lobe (neurohypophyseal) develop from?
brain tissue (fuses together w/ anterior lobe to form pituitary gland)
The anterior lobe of the pituitary develops from the hypophyseal pouch, also known as _______.
Rathke’s pouch (by oral cavity)
During development, the neurohypophyseal maintains connection to brain tissue, specifically the _________.
- hypothalamus
- axons sent from hypothalamus thru infundibulum, synapse in posterior lobe
Where is vasopressin (ADH) produced in the hypothalamus?
supraoptic nucleus
stored in posterior pituitary
Where is oxytocin produced in the hypothalamus?
paraventricular nucleus
stored in posterior pituitary
The thyroid gland is stimulated by thyroid releasing hormone from the hypothalamus, which releases TSH from the pituitary. What hormones are released from the thyroid gland itself and what are its functions?
TSH causes thyroid follicles to release T3 and T4 aka thyroxine (stimulates metabolic rate within body) - released in capillaries to systemic vasculature
What is the isthmus?
Band of tissue joining R/L lobes of thyroid (butterfly shape)
What is the function of thyroglobulin?
Follicle cells in thyroid secrete hormone precursor [thyroglobulin] into follicle activity –>add iodine –> stimulated by TSH, thyroglobulin converted into T3 + T4 –> follicle cells secreted into connective tissue –> picked up by capillaries
What is the function of parafollicular cells?
- found between follicle cells in thyroid
- aka C-cells
- produce hormone: calcitonin
- regulates calcium levels in body
Where are parathyroid glands located?
Posterior side of thyroid gland - 4 glands; 2 on each lobe (superior/ inferior)
The parathyroid is composed of what types of cells?
- parathyroid (principal) cells – secrete parathyroid hormone (promotes reintake of Ca2+)
- oxyphil cells (immature/ inactive)
What is the difference b/n calcitonin and parathyroid hormone?
Calcitonin: - decreases Ca2+ in body fluids - increases Ca2+ deposition in bone (lower Ca2+ in body) PTH: - opposite (increase Ca2+)
A mid-sagittal cross-section of an adrenal gland would show 2 parts:
- cortex (outer; 3 layers)
- medulla (inner; consistent)
What is the main hormone of the outermost layer of the adrenal cortex?
Mineralocorticoids
- increases renal Na+ and H2O
- decreases renal K+
What is the main hormone of the middle layer of the adrenal cortex?
Glucocorticoids
- stimulates protein, lipid, carb metabolism.
- anti-inflammatory
What is the main hormone of the innermost layer of the adrenal cortex?
Androgens (testosterone/ male hormones)
- stimulates growth of axillary/ pubic hair
- stimulates libido
What is the one type of cell found within the adrenal medulla?
Chromaffin cells
What is the adrenal gland innervated by?
Autonomic nervous system - preganglionic sympathetic fibres causes release of [nor]epinephrine directly into vasculature
T/F
The pancreas serves exocrine and endocrine functions.
True.
99% exocrine, 1% endocrine (islets of Langerhans)
What are acinus cells in the pancreas?
Exocrine cells - synthesizes, stores, secretes digestive enzymes
Where are alpha cells found and what hormone do they secrete?
- periphery of pancreatic islet
- secretes glucagon (body consumption of glucose: elevates blood glucose, stimulates glucose synthesis)
Where are beta cells found and what hormone do they secrete?
- most abundant within islet
- secretes insulin (glycogen synthesis + storage; decrease blood glucose levels)
Where are delta cells found and what hormone do they secrete?
- least abundant within islet
- secretes somatostatin (growth hormone- inhibiting hormone; inhibits secretion of glucagon + insulin)
Define diabetes mellitus.
Inability to produce/ use insulin.
- elevation of blood glucose levels (hyperglycemia)
- excretion of glucose in urine
- results in cardiovascular, vision problems
Define Type I diabetes.
- “insulin-dependent” diabetes (10%)
- autoimmune disease that DESTROYS INSULIN-SECRETING CELLS of islets (beta cells)
- will respond to insulin injection
Define Type II diabetes.
- “non-insulin-dependent” diabetes
- insulin-resistance&insulin-secretory defects
- target cells less sensitive to insulin (down-regulation of receptors)
- correlates w/ age, obesity (management by diet, exercise, weight loss)
Where is the pineal gland found and what is its function?
- inferior to corpus callosum
- secretes melatonin (regulates biological clock)
Where is the thymus gland found and what is its function?
- in superior mediastinum
- produces T-lymphocytes (cell-mediated immunity)
- secretes thymic hormones (proliferation+maturation of T-cells)
Where does the leptin hormone originate from? What is its function?
- adipose tissue (connected to an individual’s amount of body fat)
- helps inhibit hunger + regulate energy balance so body does not trigger hunger response when energy isn’t needed (appetite suppressant)