1. Chapter 18 Part 2 Thyroid Gland Parathyroid Gland Adrenal Gland
Synthesis and function of Thyroid hormone Calcitonin and Calcium regulation
Parathyroid Gland
PTH and Calcium regulation
Adrenal Gland
The corticosteroids
Pancreas
Regulation of blood glucose

2. Thyroid Gland Covers anterior surface of trachea 2 lobes with isthmus
Hyoid Bone
lobe of thyroid
lobe of thyroid
Covers anterior surface of trachea
2 lobes with isthmus
Isthmus
Trachea

3. Thyroid gland Tissue consists of follicles
Follicles are hollow spheres lined with epithelial cells (follicle cells)
Follicular cells take up Iodine from circulation and produce thryoglobulin (the precursor to thyroid hormone)
Thyroglobulin is stored in the colloid of follicle
C cells produce calcitonin (CT)

4. Thyroid Gland Here thyroglobulin, a glycoprotein, is stained hot pink
An elusive C-cell is indicated
Here thyroglobulin, a glycoprotein, is stained hot pink

5. Synthesis of thyroid hormone

6. Synthesis of thyroid hormone
A funky, multistep process
Iodine selectively pumped into the membrane of follicular cells
Iodine bound to tyrosine molecules, forming thyroid hormone, incorporated into thyroglobulin
Thyroglobulin is stored in follicle
Upon TSH stimulation, thyroglobulin is endocytosed back into follicle cell, diffuses across cell, and released into bloodstream

7. T4 versus T3 What is the difference?
The thyroid releases 90% T4, 10% T3
T3 is the active form!

8. Functions of Thyroid Hormone
Actively transported into all cells of body
Binds mitochondria, increases rate of mitochondrial ATP production
Binds nuclear receptors and increases transcription of Na+/K+ ATPase
Also activates genes that code for enzymes involved in glycolysis and ATP production
PUNCHLINE: Thyroid hormone increases basal metabolic rate

9. Thyroid Hormone Regulation

10. Misregulation and Goiters
TSH causes thyroid hormone release AND growth of thyroid tissue

11. C cells and Calcitonin
C cells respond directly to high levels of Ca2+ in body fluids
Release Calcitonin (CT), works to reduce Ca2+ concentration in body fluids
How??

12. Calcitonin and Ca2+ regulation
Inhibition of osteoclasts (the bone breaker-downer cells)
Stimulation of Ca2+ excretion at kidneys CT
osteoclast

13. Parathyroid Glands
Located on the posterior aspect of the thyroid gland
Chief cells produce and release parathyroid hormone (PTH) directly in response to low circulating Ca2+ levels
PTH works to increase Ca2+ levels

14. Parathyroid Glands PTH Stimulates osteoclasts
Inhibit osteoblasts (decreases rate of Ca2+ deposition)
Increases Ca2+ resorption at kidnes
Stimulates formation of calcitriol at kidneys (works at gut)
Chomp, chomp!
PTH
osteoclast

15. PTH and Calcitonin regulate Ca2+ levels

16. Adrenal Gland
cortex
medulla
The cortex has three cellular regions (zones), each that makes specific hormones
Zona glomerulosa (outermost)
Zona fasciculata (middle)
Zona reticularis (innermost)

17. Adrenal Gland
medulla G F R
250uM

18. Adrenal Cortex
Endocrine tissue that produces a variety of corticosteroids (general term for steroids from the cortex)
All affect gene transcription
This collection of steroids are vital to life
The cortex has three cellular regions (zones), each that makes specific hormones
Zona glomerulosa: Mineralocorticoids
Zona fasciculata: Glucocorticoids
Zona reticularis: Androgens

19. Adrenal Cortex Zona glomerulosa -Mineralocorticoids
Aldosterone, the “Na+ saver”
Its release is triggered by a drop in blood Na+, blood volume or blood pressure
Aldosterone works at: kidneys, sweat glands, salivary glands and pancreas to decrease Na+ secretion/release
Effect: water follows Na+, so water is saved, as well

20. Adrenal Cortex Zona fasciculata Glucocorticoids
When stimulated by ACTH, cortisol and corticosterone secreted (and cortisone is converted from cortisol by the liver)
Glucocorticoids exhibit negative feedback at both the hypothalamus and anterior pituitary

21. Effects of Glucocorticoids
Accelerate rates of glucose synthesis and glycogen formation, especially at liver
Adipose breaks down TG into Fas
Anti-inflammatory effects
Inhibit WBC and other immune system fuction
Slow migration of phagocytic cells into injury site, and decrease activity
Negative effects on wound healing

22. Adrenal cortex
Zona Reticularis
Produces androgens

23. Adrenal Medulla What is the composition of this part of the gland?
What triggers the release?
What hormones are produced?

24. Adrenal Medulla
Sympathetic division
Parasympathetic division

25. Effects of Adrenal Medulla Stimulation
@ skeletal muscles: mobilize glycogen reserves, increase beakdown of glucose into ATP
@ adipose tissue: stored fats are broken down, fatty acids into circulation
@ liver: glycogen breakdown (the brain needs glucose!)
@ heart, 1 receptors stimulated, increase in cardiac force and rate

26. Pancreas A unique gland with both exocrine and endocrine functions
Exocrine: produces enzymes for digestion
Endocrine: produces hormones for blood glucose regulation

27. Histology of the Pancreas
A single islet containing  and  cells
Endocrine Islets in a sea of exocrine cells (acinar cells)

28. Regulation of Blood Glucose
 cells release glucagon
 cells release insulin
Nutshell version:
Normal blood glucose levels = mg/dL --When blood glucose is low, glucagon stimulates glycogen breakdown and glucose release from liver
--When glucose levels are elevated, insulin encourages the uptake use, and storage of glucose

29. Regulation of blood glucose
gluconeogenesis

30. One example in detail
How does insulin actually increase glucose uptake by cells?
This process is not totally understood and is an area of intensive research.
Glucose transporter discovered in mid 1980’s

31. Diabetes
17 million Americans have Type 2 (adult-onset) diabetes, a disorder in which cells lose their ability to absorb glucose from the blood stream.
This is different from Type 1 (juvenile onset) diabetes, in which the immune system attacks insulin-producing,  cells.
What tissues, organs suffer in diabetic state? Why?