Endocrine System
1
Objectives
• 1. Identify organs belonging to the
endocrine system.
• 2. Describe the categories of hormones
and the probable mechanism of
operation of each type.
2
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.
3
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.
4
Endocrine System
5
Hormone Types
• Amino acid
• Steroid
6
Amino Acid
• Includes amines, catecholamines,
peptides and proteins
• Receptors on cell membrane
7
Amino Acid
• Superficial hormone-receptor molecule
stimulates intracellular enzyme activity
influencing cellular metabolism
• Examples
– thyroid, all pituitary hormones,
norepinephrine, calcitonin, parathormone,
insulin, glucagon
8
Steroid
• Receptors in cytoplasm
• Structurally related to cholesterol
9
10
Steroid
• Cytoplasmic or nuclear hormonereceptor complex interacts with DNA
stimulating mRNA activity and protein
synthesis within the cytoplasm
• Examples
– estrogen, testosterone, progesterone,
gonadocorticoids, cortisol, aldosterone
11
Endocrine Organs
•
•
•
•
•
•
•
•
Pituitary (see unit 10)
Pineal (see unit 10)
Pancreas (see unit 7)
Gonads (see unit 13)
Adrenal
Thyroid
Parathyroid
Other
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Adrenal
•
•
•
•
4-5 grams
4cm x 2.5 cm x 1 cm
Surrounded by fibrous capsule
Two regions
– Medulla
– Cortex
13
Adrenal Gland
14
Adrenal Medulla
• Derived from
ectoderm.
• Contains chromaffin
cells
(pheochromocytes)
15
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.
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Pheochromocytoma
17
Adrenal Cortex
• Derived from mesoderm
• 80% of adrenal gland
• Three subdivisions (deep to superficial)
– Zona reticularis
– Zona fasciculata
– Zona glomerulosa
18
Adrenal Histology
19
Zona Reticularis
• Produces gonadocorticoids/androgens
20
Zona Fasiculata
• Thickest region
• Specific target of ACTH
• Produces glucocorticoids- cortisone,
cortisol, corticosterone
• Stimulates gluconeogenesis, mobilizing
fats, liver glycogen and increasing blood
glucose
21
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
22
Adrenal Cortical
Pathologies
• Addison’s 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
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Addison’s Disease
24
Adrenal Cortical
Pathologies
• Cushing’s 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
25
Cushing’s Syndrome
26
27
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
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Thyroid
• ~25 g, size and shape variable
• Two lobes connected via isthmus
• Located anterior to thyroid cartilage of
larynx
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Thyroid Gland
30
Thyroid
• Two types of cells
• Follicular
• Parafollicular
31
Thyroid
Histology
32
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
33
Follicular &
Parafollicular Cells
34
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
35
Thyroid Pathology
• Hypothyroidism
• Adult
– myxedema
• Child
– cretinism
36
Myxedema
• Symptoms/signs
– facial swelling,
– fatigue,
– sensitivity to cold,
– skin dehydration,
– hair loss,
– lethargy,
&& more frequently affected than %%
37
Cretinism
• Symptoms/signs
–
–
–
–
poor CNS development
retardation
poor skeletal development
delayed puberty
38
Cretinism
39
Thyroid Pathology
• Goiter - enlargement of thyroid
gland.
– simple due to low iodine, enlargement
an attempt to increase thyroxine
output.
40
Goiter
41
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
%%.
42
Parathyroids
• 4 small spherical masses embedded in
posterior thyroid gland
• Chief cells produce
PTH/parathormone/parathyroid
hormone
43
Parathyroids
44
Parathyroids
• Works in conjunction with thyroid gland
parafollicular cells - thyrocalcitonin to
regulate blood calcium
45
Parathyroid/Thyroid
• Calcitonin (from parafollicular thyroid)
– blood calcium decrease
– bone reabsorption decrease
• PTH
– blood calcium increase,
– bone reabsorption increase,
– blood phosphate decrease
46
Parathyroid Pathology
• Hypoparathyroidism
– low blood Ca+ concentrations
– hypocalcemic tetany
– convulsions
– hyperexcitable CNS
47
Parathyroid Pathology
• Hyperparathyroidism
–
–
–
–
–
increased bone reabsorption
elevated blood calcium
calcification of soft tissues
kidney stones
pathological fractures
48
Other Endocrine Tissues
• Gut (see unit 7)
– gastrin, cholecystokinin, secretin,
enterocrinin
• Kidneys
– erythropoietin - stimulates RBC production
– renin - regulates blood pressure
• Placenta
– estrogen and progesterone
49