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HISTOLOGY OF ENDOCRINE ORGANS

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Differentiate between :

1. Protein hormones
2. Steroid hormones
1. Protein hormones bind to cell surface receptor proteins, which activate cells via a number of second messengers. Pathways involve activation of adenylate cyclase, receptor tyrosine kinases, etc.

2. Steroid hormones somehow pass through the cell membrane and eventually bind to receptor proteins within the cell nucleus. Activated steroid receptor proteins attach to specific DNA sequences and activate transcription of these sequences. The precise biological effects of a steroid hormone in a cell can be modulated by proteins called Co-activators, which influence the binding of a steroid hormone receptor to DNA.
What are the 7 hormone secreting cells?
1. Thyroid gland
2. Parathyroid gland
3. Adrenal glands
4. Adrenal cortex
5. Adrenal medulla
6. Pancreas
7. Pituitary gland (hypophysis)
A. Describe the 2 types of cells in the Thyroid gland and their functions?

B. What are some thyroid gland disorders?
1. Thyroid follicle cells
a. Ultrastructure – microvilli, Golgi, Lysosomes, endocytic vesicles
b. Synthesis and secretion of thyroglobulin: rER  Golgi  Secretion
granules  exocytosis
c. Iodination of thyroglobulin
Transport of iodine to follicular lumen
Iodination of thyroglobulin tyrosine residues by peroxidase at apical cell surface
Release and secretion of thyroxine (T4)
d. Effects of thyroxine (T4)

2. 3. Parafollicular cells
a. Location, ultrastructure
b. Staining reactions – formaldehyde-induced fluorescence; APUD cells
(amine precursor uptake and decarboxylation), these cells can manufacture
biogenic amines like norepinephrine
c. Function – calcitonin secretion, effects on bone and kidney

B. Some thyroid gland disorders are:
1. What are the 2 cell types in parathyroid glands?

2. What is the function of of parathyroid hormones and describe the consequences of parathyroid removal?

3. Describe Parathyroid (PTH) -related protein (PTHrP)?
1. Cell types
a. Chief cells
b. Oxyphil cells – abundant mitochondria

2. Function of parathyroid hormones
a. Action on bone
b. Fatal consequences of parathyroid removal
tetany – excessive neuromuscular excitability, probably arises from effects of low blood calcium upon calcium-sensitive potassium channels in axons

3. Parathyroid (PTH) -related protein (PTHrP)
A similar molecule produced in small amounts by many types of normal epithelial and immune cells. When these cells become cancerous, excessive secretion of PTHrP can cause hypercalcemia and skeletal damage.
Describe the Adrenal Glands (Suprarenal Glands)by mentioning:

1. Position of the Adrenal Glands
2. The 4 Gross structure of the Adrenals

3. Developmental origin of the cortex and medulla

4. Ectopic cortical and medul
C. The Adrenal Glands (Suprarenal Glands)

1. Position of the Adrenal Glands
2. Gross structure of the Adrenals
a. Embedded in fat
b. Encapsulated
c. Cortex
d. Medulla
3. Developmental origin of the cortex and medulla
4. Ectopic cortical and medullary tissues
Regarding the adrenal cortex,

1. Histological zonation – Capsule (dense C.T.) surrounds what 3 zones?

2. What are the 3 vascular supply of the adrenal cortex?

3. Describe the ultrastructure of cell types of the adrenal
1. Histological zonation – Capsule (dense C.T.) surrounding three zones:
a. Zona glomerulosa
b. Zona fasciculata - spongiocytes
c. Zona reticularis

2. Vascular supply
a. Capsular arterioles
b. Fenestrated capillaries
c. Arterioles penetrating cortex to supply medulla directly


3. Ultrastructure of cell types: mitochondria with tubular cristae, abundant SER, lipid droplets, all related to steroid synthesis
a. Fasciculata cells have more lipid than in other zones
b. Reticularis cells – lipofuscin granules

4. Endocrine products
a. Mineralocorticoids (aldosterone, essential for life) – Z. glomerulosa
b. Glucocorticoids (cortisol or corticosterone) – Z. fasciculata
c. Androgens and estrogens (dehydroepiandrosterone, DHEA) – Z. Reticularis
Differentiate between:

1.Hypoadrenocorticism

2.Hyperadrenocorticism
1. Hypoadrenocorticism (Addison’s Disease)

2. Hyperadrenocorticism (Cushing’s and Conn’s Syndromes, Adrenogenital
syndrome)
1. What are the 2 cell types of the adrenal medulla?

2. What are Enkephalins?

3. What are Chromogranin proteins ?

4. The blood supply of adrenal medulla is rich in what?
1. Cell types
a. Chromaffin cells, undergo “chromaffin reaction” after perfusion with dichromate; secrete catecholamines: epinephrine (adrenalin), norepinephrine (noradrenalin)

Because these neurotransmitters can be made to fluoresce, these cells show a formaldehyde-induced fluorescence.
After glutaraldehyde fixation, it may be possible to distinguish between
these 2 type of chromaffin cells (norepinephrine stains darker).

b. Ganglion cells

2. Enkephalins – peptides (5 amino acids) secreted from chromaffin cells
simultaneously with norepinephrine. Have an opioid-like activity like
pituitary β-endorphin, but are cleaved from an entirely different precursor
molecule.

3. Chromogranin proteins – first identified in chromaffin cells; secreted
along with peptide hormones of the adrenal medulla and also of many other endocrine cells.

4. The medulla receives a blood supply rich in glucocorticoids; glucocorticoids
stimulate synthesis of catecholamines.
Describe cancers of the adrenal gland?
later
1. Describe the glands in the pancreas and state the 2 types?
1.The pancreas has elongated gland, which lies in the bed of the stomach. The 2 types are:
a. mixed exocrine (pancreatic enzymes)

b. endocrine (insulin etc.) gland
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