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 hormones are synthesized & secreted from the Hypothalamus into the Posterior (NH) pituitary?
Oxytocin & ADH (Vasopressin)
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 hormones are released from the Hypothalamus in the regulation of the Anterior (AH) pituitary?
Stimulatory:
- Thyrotropin-RH
- Gonadotropin-RH
- Growth Hormone-RH
- Corticotropin-RH
- Prolactin-RH
Inhibitory:
- Prolactin-IH
- GH-IH (Somatostatin); Inhibits GH & TSH release
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
Describe the characteristics of Hyperthyroidism
Hypermetabolic state (weight loss, nervousness, sweating, eye bulging
- Autoimmune (stimulatory antibodies to TSH receptor)
Describe the characteristics of Hypothyroidism
Cold intolerance, fatigue, weight gain, concentration deficits
- Iodine insufficiency (goiter – thyroid hyperplasia)
- Autoimmune disease (Hashimoto’s thyroiditis)
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
