E2: Endocrine Flashcards
What kind of tissue is this?
Anterior Pituitary; Pars Distalis
Pars Distalis is 75% of AP
Nests of: ABC’s surrounded by Sinusoids (S)
•Acidophils (A)
- •Somatotrophs: Secrete Somatotropin
- •Lactotrophs: Secretes Prolactin
•Basophils (B):
- •Corticotrophs: Secretes ACTH & B-LPH
- •Gonadotrophs: Secretes LH & FSH
- •Thyrotrophs
•Chromophobes (C)
Describe the Pars Tuberalis
Pars Tuberalis:
- Small funnel-shaped region surrounding the infundibulum of the neurohypophysis
- Most PT cells are Gonadotrophs
Describe the Pars intermedia
Pars Intermedia:
- Narrow zone lying between the PD & PN
- Contains:
- •Basophils (corticotrophs)
- •Chromophobes
- •Small, colloid-filled cysts derived from lumen of embryonic hypophyseal pouch
Which organs are exclusively Endocrine? (5)
- Pituitary (A&P) Gland
- Adrenal Gland
- Thyroid Gland
- Parathyroid Gland
- Pineal Gland
Which organs are mixed Endocrine & non-endocrine?
- Pancreas
- Testis
- Ovary
Describe the condition of Acromegaly
Acromegaly:
•Condition of excess pituitary GH (95% due to benign pituitary adenomas)
Manifestations:
- Adults: Acromegaly
- Excessive growth of soft tissues and appositional bone growth (particularly jaw and skull, leading to disfiguring facial changes)
- Children: Gigantism
- Tumor growth leads to headaches, vision loss
Treatment:
- Surgery, drugs to lower GH
- Rate of change is slow: few patients seek care until they experience discomfort
Describe how the Pituitary gland forms
•Pituitary forms via invaginations from (2) separate embryonic structures:
- •Base of the brain (Floor of the diencephalon) forms the Neurohypophysis (posterior) pituitary
- •Roof of the mouth forms the Adenohypophysis (anterior) pituitary
“Rathke’s Pouch”; Remnants of the roof of the mouht in adults appear as cystic spaces filled with Colloid*
Describe the structure of the Pituitary Gland
Protrudes from the base of the brain (hypothalamus)
- Sits in a bony cavity (Sella Turcica)
2 Major Regions: Anterior & Posterior
Anterior (Adenohypophysis)
- Pars Distalis (PD)
- Pars Intermedia (PI)
- Pars Tuberalis (wraps around infundibulum) (PT)
Posterior (Neurohypophysis)
- Infundibulum (stalk) (IS)
- Pars Nervosa (PN)
What are the sections of the Anterior Pituitary?
Overall, which hormones are released here?
Pars Distalis (75%)
Pars Intermedia
Pars Tuberalis (Wraps around Infundibulum)
Hormones: FLAT-PEG
- FSH
- LH
- ACTH
- TSH
- Prolactin
- Endorphins
- GH
What are the components of the Posterior Pituitary?
What is the primary hormone released here?
Pars Nervosa
Infundibulum
Hormone: Oxytocin
What are the ABC’s of the Pars Distalis?
Pars Distalis: 75% of AP
- Nests of: ABC’s surrounded by Sinusoids (S)
•Acidophils (A)
- Somatotrophs: Secrete Somatotropin
- Lactotrophs: Secretes Prolactin
•Basophils (B):
- Corticotrophs: Secretes ACTH & B-LPH
- Gonadotrophs: Secretes LH & FSH
- Thyrotrophs
•Chromophobes (C)
What Tissue is this?
What type of cell could A represent?
Acidophils:
Somatotrophs: (Somatotropin)
Lactotrophs: (Prolactin)
What Tissue is this?
What type of cell could B represent?
- Basophils (B):
- Corticotrophs: (ACTH & B-LPH)
- Gonadotrophs: (LH & FSH)
- Thyrotrophs
What Tissue is this?
What type of cell could C represent?
•Chromophobes (C)
What type of tissue is this?
What does C represent?
C: Small Colloid-filled cysts derived from the lumen of the embryonic hypophyseal pouch
“Rathke’s Pouch”
What factors stimulate ADH (Vasopressin) release from the Hypothalamus?
What are the actions of ADH?
Factors stimulating Hypothalamic release of ADH (Vasopressin):
- Hyperosmolarity
- Decreased atrial receptor firing
- Angiotensin II
- Sympathetic Stimulation
ADH (Vasopressin) Actions:
1.Vasoconstriction (V1)
•Increased Systemic Vascular Resistance
2.Renal Fluid reabsorption (V2)
•Increased Blood Volume
Net Result: Increased Arterial Pressure
What are the components of the Adrenal gland?
- Capsule
- Adrenal Cortex:
- Zona Glomerulosa (15%)
- Zona Fasciculata (65-80%)
- Zona Reticularis (10%)
- Adrenal Medulla
Generally describe the appearance of the Adrenal Cortex
ZG: tightly packed cells; round/circular arrangement; w/ many capillaries
ZF: More loosely packed cells (compared to ZG & ZR); linear arrangement, w/ capillaries
ZR: Tightly packed cells; Darker than the rest of cortex; Irregular arrangement; borders Medulla
Describe the Zona Glomerulosa
Clusters of cells surrounded by capillaries
Produce Aldosterone (Mineralocorticoid) which influences
- Salt balance
- Promotes renal tubular absorption of Na+
- Indirect effects on volume & bp
Describe the Zona Fasciculata
Straight columns of cells surrounded by capillaries
Produces Cortisol (Glucocorticoid) in response to ACTH
- Stress hormone (GCR on all cells)
- Increases blood sugar via stimulation of Gluconeogenesis/glycogenolysis
- Promotes muscle breakdown
- Downregulates the immune system
Regulation of Cortisol:
- Major determinant is ACTH
- Healthy individuals: pulsatile and circadian secretion of ACTH/cortisol
- Emotional or physical stress: large amounts of ACTH/cortisol
Describe Zona Reticularis
Smaller cells in irregular cords interspersed w/ capillaries. Typically stained darker than the rest of the cortex
Produces DHEA (Weak androgen) which is converted to Test in Men & Women
Describe the Adrenal Medulla
Adrenal medulla:
Nests of chromaffin cells surrounded by capillaries
Cells are modified neurons which lost their axons & became secretory cells
Produces:
- Epinephrine (80%)
- Norepinephrine (20%)
Controlled by sympathetic NS
Thyroid: General
- Structure:
- Location:
- Products:
Two lobes united by an isthmus, situated over the Larynx
Products:
- Thyroxine (T4) & TriIodothyronine (T3): Regulates basal metabolic rate
- Calcitonin: Lowers plasma Ca2+
Appearance:
- Millions of spheres (follicles)
- Simple cuboidal epithelium
- Synthesize a gelatinous eosinophilic colloid (thyroglobulin)
Thyroid hormones (T3 & T4)
How are they synthesized?
How do they regulate Metabolic rate?
Synthesis:
- Thyroglobulin protein is delivered across the apical membrane into the lumen of the follicle by the secretory pathway.
- Iodine is absorbed from the blood at the cell base and concentrated into the colloid by the apical I-/Cl- transporter pendrin.
- Membrane enzyme thyroid peroxidase iodinates thyroglobulin on tyrosines: MIT, DIT
- Two iodinated tyrosines, still part of thyroglobulin are conjugated together to make pre-T3 and pre-T4
- The pre-T3 and pre-T4 are endocytosed fused with lysosomes, and the thyroglobulin is degraded. T3 and T4 is released into the blood
Metabolic Rate:
- Increase number/size of mitochondria
- Increase lipid metabolism
- Increase carbohydrate metabolism
- Promotes growth and development in children
Describe the regulation of Thyroid Hormones
Calcitonin
Where is it synthesized?
Describe it’s actions.
Produced by parafollicular cells (C cells)
Action: Lowers Ca2+ by inhibiting bone resorption by osteoclasts
Secretion triggered by increased plasma Ca2+
Parathyroid:
What are the components?
Central function & products?
Structure:
- •Four small glands behind thyroid (usually embedded within its capsule)
- •One hormone: PTH
PTH Function: Raises blood Ca2+
- •Stimulates osteoclasts to produce osteoclast-stimulating factor
- •Increases the number/activity of osteoclasts
- •Stimulates Ca2+ reabsorption by the kidney
- •Indirectly increases Ca2+ absorption by the gut
- •Increases the activity of an enzyme that converts the major circulating form of inactive vitamin D into its active form in the kidney
Parathyroid:
Describe the cells & appearance
Chief cells: secrete PTH
Oxyphils: Function unknown (if any)
Adipose tissue: Increases with age
Explain calcium homeostasis
Pineal gland
Describe it’s function & appearance
Mice:
- •Regulates circadian rhythmns
- •Sexual development, hibernation, seasonal breeding, sleep cycles
Humans:
- •Produces melatonin in response to the dark
- •Function not well understood
- •Has been used to treat insomnia, jet-lag, but efficacy is controversial
