Endocrine System

1
Endocrine System
2
Objectives

• 1. Identify organs belonging to the endocrine
  system.
• 2. Describe the categories of hormones and the
  probable mechanism of operation of each type.

3
Objectives

• 3. Identify hormones, their organ of secretion,
  the type of molecule their structure represents,
  their primary target organ, the effect of the
  hormone on the body, and any pathologies
  associated with the deficiency or excess of the
  hormone.

4
Objectives

• 4. Describe the location, histology and products
  associated with the pituitary (review), pancreas
  (review), adrenal, thyroid, parathyroid, pineal
  and thymus.
• 5. Define and use the correct terminology
  associated with the endocrine system.

5
Endocrine System
6
Hormone Types

• Amino acid
• Steroid

7
Amino Acid

• Includes amines, catecholamines, peptides and
  proteins
• Receptors on cell membrane

8
Amino Acid

• Superficial hormone-receptor molecule stimulates
  intracellular enzyme activity influencing
  cellular metabolism
• Examples
• thyroid, all pituitary hormones, norepinephrine,
  calcitonin, parathormone, insulin, glucagon

9
Steroid

• Receptors in cytoplasm
• Structurally related to cholesterol

10
(No Transcript)
11
Steroid

• Cytoplasmic or nuclear hormone-receptor complex
  interacts with DNA stimulating mRNA activity and
  protein synthesis within the cytoplasm
• Examples
• estrogen, testosterone, progesterone,
  gonadocorticoids, cortisol, aldosterone

12
Endocrine Organs

• Pituitary (see unit 10)
• Pineal (see unit 10)
• Pancreas (see unit 7)
• Gonads (see unit 13)
• Adrenal
• Thyroid
• Parathyroid
• Other

13
Adrenal

• 4-5 grams
• 4cm x 2.5 cm x 1 cm
• Surrounded by fibrous capsule
• Two regions
• Medulla
• Cortex

14
Adrenal Gland
15
Adrenal Medulla

• Derived from ectoderm.
• Contains chromaffin cells (pheochromocytes)

16
Adrenal Medulla

• Innervated by sympathetic n.s.
• Produces epinephrine norepinephrine
  (catecholamines).
• Pathology.
• pheochromocytoma - 8 blood pressure, BMR,
  sympathetic response.
• neuroblastoma - malignant tumor metastasizing to
  bone.

17
Pheochromocytoma
18
Adrenal Cortex

• Derived from mesoderm
• 80 of adrenal gland
• Three subdivisions (deep to superficial)
• Zona reticularis
• Zona fasciculata
• Zona glomerulosa

19
Adrenal Histology
20
Zona Reticularis

• Produces gonadocorticoids/androgens

21
Zona Fasiculata

• Thickest region
• Specific target of ACTH
• Produces glucocorticoids- cortisone, cortisol,
  corticosterone
• Stimulates gluconeogenesis, mobilizing fats,
  liver glycogen and increasing blood glucose

22
Zona Glomerulosa

• Outermost
• Produces mineralcorticoids aldosterone
• Stimulates Na reabsorption, K secretion by
  kidney affecting urine concentration and volume
• 8Aldosterone 8Na secretion 8 H2O reabsorption9
  urine volume

23
Adrenal Cortical Pathologies

• Addisons disease - hyposecretion of
  glucocorticoids due to lack of response to ACTH
  symptoms include weight loss, weakness,
  hypoglycemia, skin bronzing due to increased
  activity of melanocytes

24
Addisons Disease
25
Adrenal Cortical Pathologies

• Cushings syndrome - hypersecretion of
  glucocorticoids, suppressed glucose metabolism
  caused by hypersecretion of ACTH or tumor,
  immunosuppressive drugs in transplant symptoms
  include fat redistribution (pendulous abdomen,
  puffy face, humpback), reduced muscle mass,
  strength

26
Cushings Syndrome
27
(No Transcript)
28
Adrenal Cortical Pathologies

• Aldosteronism - Na retention, K depletion
  symptoms include edema, abnormal cardiac, kidney
  and neural function due to ion imbalance
• Hypoaldosteronism - excessive Na and H2O loss
  symptoms include low BP, abnormal neural and
  muscular functions
• Adrenogenital syndrome- hypersecretion of
  gonadocorticoids symptoms include virilism in
  females children, gynecomastia in males

29
Thyroid

• 25 g, size and shape variable
• Two lobes connected via isthmus
• Located anterior to thyroid cartilage of larynx

30
Thyroid Gland
31
Thyroid

• Two types of cells
• Follicular
• Parafollicular

32
Thyroid Histology
33
Thyroid Follicular Cells

• Follicular - forming follicles
• Produce thyroglobin protein suspended in colloid
  of follicles
• Thyroglobin converted into thyroid hormones
• thyroxine /TX/T4/tetraiodothyronine
• T3/triiodothyronine

34
Follicular Parafollicular Cells
35
Thyroid

• Parafollicular cells/C cells
• Outside of follicles
• Produce thyrocalcitonin
• Regulates Ca concentration by 9 bone
  reabsorption of Ca, stimulating osteoblasts, 9
  Ca reabsorption by gut and 8 Ca excretion by
  kidney

36
Thyroid Pathology

• Hypothyroidism
• Adult
• myxedema
• Child
• cretinism

37
Myxedema

• Symptoms/signs
• facial swelling,
• fatigue,
• sensitivity to cold,
• skin dehydration,
• hair loss,
• lethargy,
• more frequently affected than

38
Cretinism

• Symptoms/signs
• poor CNS development
• retardation
• poor skeletal development
• delayed puberty

39
Cretinism
40
Thyroid Pathology

• Goiter - enlargement of thyroid gland.
• simple due to low iodine, enlargement an attempt
  to increase thyroxine output.

41
Goiter
42
Thyroid Pathology

• Hyperthyroidism/thyrotoxicosis.
• BMR BP and heart rate increase,
• Flushing.
• fatigue.
• Graves disease includes above plus.
• Goiter.
• bulging eyes (exophthalmos).
• more frequently affected than .

43
Parathyroids

• 4 small spherical masses embedded in posterior
  thyroid gland
• Chief cells produce PTH/parathormone/parathyroid
  hormone

44
Parathyroids
45
Parathyroids

• Works in conjunction with thyroid gland
  parafollicular cells - thyrocalcitonin to
  regulate blood calcium

46
Parathyroid/Thyroid

• Calcitonin (from parafollicular thyroid)
• blood calcium decrease
• bone reabsorption decrease
• PTH
• blood calcium increase,
• bone reabsorption increase,
• blood phosphate decrease

47
Parathyroid Pathology

• Hypoparathyroidism
• low blood Ca concentrations
• hypocalcemic tetany
• convulsions
• hyperexcitable CNS

48
Parathyroid Pathology

• Hyperparathyroidism
• increased bone reabsorption
• elevated blood calcium
• calcification of soft tissues
• kidney stones
• pathological fractures

49
Other Endocrine Tissues

• Gut (see unit 7)
• gastrin, cholecystokinin, secretin, enterocrinin
• Kidneys
• erythropoietin - stimulates RBC production
• renin - regulates blood pressure
• Placenta
• estrogen and progesterone