18-1 thyroid gland on each side of trachea is lobe of thyroid weighs 1 oz & has rich blood...
TRANSCRIPT
18-1
Thyroid Gland
On each side of trachea is lobe of thyroid Weighs 1 oz & has rich blood supply
18-2
Photomicrograph of Thyroid Gland
Copyright 2009, John Wiley & Sons, Inc.
Copyright 2009, John Wiley & Sons, Inc.
Thyroid Gland
Located inferior to larynx 2 lobes connected by isthmus Thyroid follicles produce thyroid hormones
Thyroxine or tetraiodothyronine (T4) Triiodothyronine (T3)
Both increase BMR, stimulate protein synthesis, increase use of glucose and fatty acids for ATP production ,and growth
increases sympathetic activity
Parafollicular cells or C cells produce calcitonin Lowers blood Ca2+ by inhibiting bone resorption
18-5
Actions of Thyroid Hormones
T3 & T4 = thyroid hormones responsible for our metabolic rate, synthesis of protein, breakdown of fats, use of glucose for ATP production
Copyright 2009, John Wiley & Sons, Inc.
Control of thyroid hormone secretion
Thyrotropin-releasing hormone (TRH) from hypothalamus
Thyroid-stimulating hormone (TSH) from anterior pituitary
Situations that increase ATP demand also increase secretion of thyroid hormones
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
HypothalamusTRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
Anteriorpituitary
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
Anteriorpituitary
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
TSH released intoblood stimulatesthyroid follicular cells
Thyroidfollicle
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
Anteriorpituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
3
T3 and T4
released intoblood byfollicular cells
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
TSH released intoblood stimulatesthyroid follicular cells
Thyroidfollicle
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
Anteriorpituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
3
4 T3 and T4
released intoblood byfollicular cells
ElevatedT3inhibitsrelease ofTRH andTSH(negativefeedback)
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
TSH released intoblood stimulatesthyroid follicular cells
Thyroidfollicle
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
Anteriorpituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
3
5
4
Copyright 2009, John Wiley & Sons, Inc.
Thyroid Gland
Located inferior to larynx 2 lobes connected by isthmus Thyroid follicles produce thyroid hormones
Thyroxine or tetraiodothyronine (T4) Triiodothyronine (T3)
Both increase BMR, stimulate protein synthesis, increase use of glucose and fatty acids for ATP production
increases sympathetic activity
Parafollicular cells or C cells produce calcitonin Lowers blood Ca2+ by inhibiting bone resorption
18-9
Actions of Thyroid Hormones
T3 & T4 = thyroid hormones responsible for our metabolic rate, synthesis of protein, breakdown of fats, use of glucose for ATP production
Calcitonin = responsible for building of bone & stops reabsorption of bone (lower blood levels of Calcium)
18-10
Parathyroid Glands
4 pea-sized glands found on back of thyroid gland
Copyright 2009, John Wiley & Sons, Inc.
Parathyroid Glands
Embedded in lobes of thyroid gland Usually 4 Parathyroid hormone (PTH) or parathormone
Major regulator of calcium, magnesium, and phosphate ions in the blood
Increases number and activity of osteoclasts Elevates bone resorption
Blood calcium level directly controls secretion of both calcitonin and PTH via negative feedback
18-12
Parathyroid Hormone
Raise blood calcium and Mg levels (decrease HPO4) -2 ) increase activity of osteoclasts increases reabsorption of Ca+2 by kidney increase loss of phosphate (HPO4) -2 in urine promote formation of calcitriol (vitamin D3) by
kidney which increases absorption of Ca+2, HPO4 and Mg+2 by intestinal tract
Opposite function of calcitonin
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
2
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
3
2
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+ in urine, thus increasing bloodCa2+ level.
3
4 2
1
PTH also stimulatesthe kidneys to releaseCALCITRIOL.
High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+ in urine, thus increasing bloodCa2+ level.
3
4 25
1
CALCITRIOL stimulatesincreased absorption ofCa2+ from foods, whichincreases blood Ca2+ level.
PTH also stimulatesthe kidneys to releaseCALCITRIOL.
High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+ in urine, thus increasing bloodCa2+ level.
3
4 25
6
18-14
Adrenal Glands
One on top of each kidney 3 x 3 x 1 cm in size and weighs 5 grams Cortex produces 3 different types of hormones
from 3 zones of cortex Medulla produces epinephrine & norepinephrine
18-15
Structure of Adrenal Gland
Cortex derived from mesoderm Medulla derived from ectoderm
Copyright 2009, John Wiley & Sons, Inc.
Adrenal Glands
2 structurally and functionally distinct regions Adrenal cortex
Mineralocorticoids affect mineral homeostasis Glucocorticoids affect glucose homeostasis
Cortisol “hydrocortisone”, corticosterone and cortisone Androgens have masculinzing effects
Dehydroepiandrosterone (DHEA) only important in females Adrenal medulla
Modified sympathetic ganglion of autonomic nervous system
Intensifies sympathetic responses Epinephrine and norepinephrine
18-17
Mineralocorticoids
95% of hormonal activity due to aldosterone Functions
increase reabsorption of Na+ with Cl- , bicarbonate and water following it
promotes excretion of K+ and H+ Hypersecretion = tumor producing
aldosteronism high blood pressure caused by retention of Na+ and
water in blood
18-18
Regulation of Aldosterone
18-19
Glucocorticoids 95% of hormonal activity is due to cortisol Functions = help regulate metabolism
increase rate of protein catabolism & lipolysis conversion of amino acids to glucose stimulate lipolysis provide resistance to stress by making
nutrients available for ATP production raise BP by vasoconstriction anti-inflammatory effects reduced
reduce release of histamine from mast cells decrease capillary permeability depress phagocytosis Decrease tissue repair
18-20
Adrenal Medulla
Chromaffin cells receive direct innervation from sympathetic nervous system develop from same tissue as postganglionic
neurons Produce epinephrine & norepinephrine Hormones are sympathomimetic
effects mimic those of sympathetic NS cause fight-flight behavior
Acetylcholine increase hormone secretion by adrenal medulla