Endocrine System Flashcards
Endocrine System Overview
- Ductless glands and endocrine tissues within other organs
- Secrete chemicals = hormones into blood
~Transported via circulation and act on target cells
~ Target cell = cell with receptor specific for that hormone
Hormone Classes
1) Steroids
2) Hormones derived from amino acids
3) Peptides and Proteins Hormone
Steroids
- Synthesized from cholesterol (lipid soluble)
- E.g. tester one, estrogen, vitamin D
Hormones derived from amino acids
- e.g. derived from tyrosine
a) Thyroxine/ T4 - a thyroid hormone
- lipid soluble
- controls cellular metabolism, growth, development
b) Epinephrine + Norepinephrine (catecholamines) - adrenal medulla hormones
- water soluble
- short term stress - part of fight-or-flight response
Peptides and Proteins Hormones
- Chain of amino acids held together by peptide bonds
- Water soluble
- E.g. oxytocin, antidiuretic hormone (ADH), growth hormone (GH), insulin
Endocrine Glands
- Glands with NO OTHER FUNCTION
1) Pituitary Gland
2) Thyroid Gland
3) Parathyroid Glands
4) Adrenal Glands
Pituitary Gland
- Suspended from hypothalamus
- Lies in sella turcica of sphenoid bone
- 2 lobes:
1) Anterior Pituitary
2) Posterior Pituitary
Anterior Pituitary
- Epithelial tissue
- Anterior pituitary hormone secretion regulated by hormones released from the hypothalamus
Metabolism Hormones (Anterior Pituitary)
1) Growth Hormone - promotes growth + metabolism
2) Thyroid Stimulating Hormone (TSH)
- Stimulates activity of thyroid gland
3) Adrenocorticotropic Hormone (ACTH)
- Stimulates secretion of adrenal steroids (adrenal cortex)
Reproductive Hormones (Anterior Pituitary)
1) Luteinizing Hormone (LH)
2) Follicle Stimulating Hormone (FSH)
3) Prolactin (PRL)
- Stimulates milk formation
Posterior Pituitary
- Nervous tissue
- Extension of hypothalamus, stored and secreted from post pituitary:
1) Oxytocin - Stimulates uterine contraction and milk ejection
2) Antidiuretic Hormone (ADH) - Water reabsorption in the kidney
Thyroid Gland
- On anterior surface of superior part of trachea
- Butterfly shaped
1) Follicles - Walls = epithelial (follicular) cells
- Produce mainly T4 - activated in other tissues to T3
2) Parafollicular Cells - Between follicles
- Secrete calcitonin - increases Ca++ uptake into bone (bone formation), which lowers blood Ca++
Parathyroid Glands
- 4 (usually) glands embedded in posterior thyroid
- Secrete parathyroid hormone (PTH)
Which increases blood Ca++ by:
a) increases Ca++ release from bone (=bone resorption) - activates osteoclasts
b) Decreases Ca++ loss in urine (kidney)
c) Increases vitamin D activation (kidney) - Vitamin D then more Ca++ absorption at the small intestine
Adrenal Glands
- Superior surface of each kidney
- 2 parts:
1) Adrenal Cortex (outer)
2) Adrenal Medulla (inner)
Adrenal Cortex
- Epithelial steroids only
- 3 layers:
1) Zona glomerulosa - Secretes mineralocorticoids (mainly aldosterone)
- Salt balance
2) Zona Fasciculata - Secretes glucocorticoids (mainly cortisol)
- Long-term stress hormone
- Carbohydrate metabolism
3) Zona Reticularis - Secretes androgens (a small amount of testosterone)
- Women - sex drive
- Some converted in other tissues (e.g. fat) to estrogens
Adrenal Medulla
- Nervous tissue
- 2 hormones:
1) Epinephrine (80%)
2) Norepinephrine (20%)
Endocrine Tissues
- Endocrine function in organs that have other functions as well:
1) Pancreatic Islets of Langerhans
2) Hypothalamus
3) Gonads
4) Others
Pancreatic Islets of Langerhans
- 4 cell types (we will cover 2):
a) _ cells - Produce glucagon
which increases blood glucose
b) B-Cells - Produce insulin
which decreases blood glucose
Hypothalamus
- Regulates anterior pituitary via e.g.:
a) GHRH = growth hormone releasing hormone
b) GHIH = growth hormone release -inhibiting hormone
c) GnRH = gonadotropin releasing hormone (for LH, FSH) - Synthesizes posterior pituitary hormones
Gonads
Testes
- Lydia cells = testosterone
Ovaries
- Cells of secondary and vesicular follicle (estrogen)
- Corpus lute = estrogen + progesterone
Others
Duodenum = secretion Kidney = Renin Skin = Vitamin D Heart =Atrial natriuretic peptide (ANP) -ETC..
