The Endocrine System

Question 1

The endocrine system: Definition and Organization

Answer 1

1. Definition:
   - endocrine gland: ductless gland secreting a chemical product (hormone) directly into the blood for action on particular “target organ(s)”
2. Organization:
   - hypophysis (pituitary gland);located in the sella turcica
   - adenohophysis (anterior lobe): composed of glandular epithelium
   - neurohypophysis (posterior lobe): composed of neuroendocrine cells

Question 2

Neurohypophysis

Answer 2

1. Oxytocin and Antidiuretic hormones stored, produced in hypothalamus:
   - Oxytocin: smooth muscle stimulant, especially affecting the uterus and ducts of the breasts
   - Antidiuretic Hormone: systemic arteriole constriction (^BP), plus increased water reabsorption along the collecting tubules of the nephron.

Question 3

Adenohophysis

Answer 3

1. Growth hormone:
   - stimulates skeletal and muscular development and raises blood sugar levels.
2. adenocorticotropin hormone:
   - influences production of most adrenal cortical homrones
3. thyroid stimulating hormone:
   - influences secretion of the thyroid horomones
4. prolactin:
   - initiates and maintains milk production (lactation)
5. melanocyte stimulating hormone:
   - increased melanin synthesis in skin may suppress appetite–>weight loss (?)
6. follicle stimulating hormone:
   - develops follicle cells in the ovaries–> ova
   - develops seminiferous tubules in the testes–> sperm
7. luteinizing hormone:
   - stimulates the corpus luteum in ovary—> progesterone and estrogen
8. interstitial cell stimulating hormone:
   - stimulates interstitial cells of testes–> testosterone

Question 4

Adrenal (suprarenal glands):

Answer 4

1. gross anatomy and location:
   - medulla/cortex: situated on top of kidneys
   - pyramid shaped

Question 5

Adrenal Medulla

Answer 5

1. two synthesized hormones:
   
   • epinephrine and norepinephrine
   • helps maintain heart rate, blood pressure, and blood sugar levels.
   • innervated and controlled by sympathetic neurons
2. Medullary dysfunctions:
   - hypersecretion (pheochromocytoma)–> hypertension, ^HR, and hyperglycemia
   - hyposecretion –> usually nonproblematic

Question 6

Adrenal Cortex

Answer 6

1. three functional zones:
   a) . zona glomerulosa (outer):
   
   • produces aldosterone, a mineralocorticoid
   • increased sodium and water retention by the kidney
     b) . zona fasciculata (middle):
   • produces cortisol, a glucocorticoid
   • promotes glucose production from fat and protein
   • anti-inflammatory action
     c) . zona reticularis (innermost):
   • produces testosterone, an androgen
   • helps maintain gonads/libido
2. Cortical dysfunctions:
   
   • hypersecretion (cushing syndrome or adrenogenital syndrome)—> fluid retention, weight gain or poor infection resistance and masculinization
   • hyposecretion (Addison disease)—> fluid and mineral depletion,hypoglycemia

Question 7

Thyroid gland:

Answer 7

1. gross anatomy and location:
   
   • two lobes connecting by isthmus
   • bilateral along trachea, inferior to larynx
2. Microanatomy:
   a) . thyroid follicles:
   
   • follicle cells (acini)–> thyroxin
   • increases general metabolism
     b) parafollicle cells (C cells)–> calcitonin
   • promotes calcium deposition in bones
   • increases osteoblast activity
3. thyroid dysfunctions
   
   • hyperfunction–> elevated metabolism
   • hypofunction–> lowered metabolism
   • any thyroid enlargement–> goiter

Question 8

Parathyroid glands:

Answer 8

1. gross anatomy and location:
   - 4 to 6 flattened spheres
   - posterior aspect of thyroid lobes
2. microanatomy:
   a) . principal cells–> parathyroid hormone
   
   • releases calcium from bone
   • increases blood calcium: lowers phosphate
   • increases osteoclast activity
     b) . oxyphils–> supported principal cells
3. parathyroid dysfunctions
   a) hyperfunction–> ^blood calcium
   
   • kidney stones, pliable bones
     b) . hypofunction–> v blood calcium
   • ^ phosphate, neuromuscular excitability.

Question 9

pancreas

Answer 9

1. gross anatomy and location:
   
   • elongated, hammer-shaped
   • retroperitoneal, along inner curve of duodenum
2. microanatomy
   a) . pancreatic acini/ducts (exocrine)—> digestive enzymes into the duodenum
   b) . islets of langerd endocrine
   
   • alpha cells—> glucagon, increases blood sugar
   • beta cells—> insulin, lowers blood sugar.
3. pancreatic (beta cell) dysfunctions:
   - hyperfunction—> hypoglycemia, collapse
   - hypofunction (diabetes mellitus)–> hyperglycemia, coma, death

Question 10

Ovaries

Answer 10

1. Gross anatomy and location:
   - ovoid, 1-2” in length
   - in pelvic cavity, secured to the uterus
2. microanatomy:
   a) . follicle cells–> estrogen/egg
   b) . corpus luteum (follicular remnant)–> estrogen and progesterone
   
   • helps maintain female reproductive tract

Question 11

Testes:

Answer 11

1. gross anatomy and location:
   
   • ovoid, 1-2” in length
   • outside pelvic cavity within scrotum
2. Microanatomy:
   
   • semineferous tubules—> sperm
   • interstitial cells—> testosterone, helps maintain male reproductive tract and libido.

Question 12

Pineal gland

Answer 12

1. gross anatomy and location:
   
   • conical, pea size, 0.1 gram
   • attached to posterior wall of the third ventricle
2. microanatomy:
   
   • neuroendocrine cells—> melatonin
   • inhibits release of pituitary gonadotropins, may regulate sleep/wake cycles
3. pineal dysfunctions:
   - hyperfunction—>delayed puberty
   - hypofunction—>premature puberty