4. Endocrine organs are ductless glands
Contain rich network of
blood sinusoidal fenestrated capillaries
lymphatic capillaries
Release hormones into
the blood, lymph, and intracellular spaces
Hormone chemistry:
steroids
proteins
glycoproteins
amino acid derivatives
5. Endocrine system is regulating and controlling body system
Hormones
act on specific target cells
interact with cell receptors (surface or nuclear)
alter the target cell biological activity
Control
mechanisms:
(a) endocrine
(b) paracrine
(c) autocrine
6. Hypothalamus
Contains nuclei of neurosecretory cells
Nuclei with large cells:
Paraventricular nuclei
Supraoptic nuclei
Nuclei with small cells:
Dorsomedial nuclei
Ventromedial nuclei
Arcuate or Infundibular nuclei
⇒
7. Neurosecretory cells secrete hormones
Neurosecretory cell axons
leave the hypothalamus
terminate on blood capillaries
form the axovasal synapses in
the neurohemal organs
⇔
9. Hypothalamus nuclei with large neurosecretory cells
Paraventricular nuclei ⇒ oxytocin
Supraoptic nuclei ⇒ ADH
Neurosecretory cell axons
pass through the pituitary stalk
(hypothalamohypophysial tract)
enter the pars nervosa
form axovasal synapses
10. Hypothalamus nuclei with small neurosecretory cell
Secrete adenohypophyseal tropic hormones:
releasing (liberins)
inhibiting (statins)
Neurosecretory cell axons:
form axovasal synapses in the median eminence
on capillaries of the primary capillary network
11. Hypophysis (pituitary gland)
lies beneath the brain
is connected with the hypothalamus
hypothalamohypophysial
neuroendocrine system
12. Hypophysis anatomical subdivision
Neurohypophysis (nerves tissue)
Pars nervosa (posterior lobe)
Infundibulum
Adenohypophysis (epithelial tissue)
Pars distalis (anterior lobe)
Pars intermedia
Pars tuberalis
16. Pars nervosa nerve fibers
are axons of the neurosecretory cells
from supraoptic and paraventricular nuclei
of the hypothalamus
form hypothalamohypophyseal tract
convey hormones to the pars nervosa
form axovasal synapses on capillaries
17. Herring bodies
are dilated axon terminals
accumulate secretory granules
release hormones to the bloodstream
27. Portal system transports hypothalamic hormones
neurosecretory cells release
liberins
statins
in primary capillary network
⇓
portal veins
⇓
secondary capillary network
of the adenohypophysis
28. Adenohypophysis is regulated by hypothalamic hormones
Liberins and statins
leave the secondary capillaries
stimulate or inhibit adenohypophysis cells
⇔
29. Thyroid gland
is located
in anterior portion of the neck
on the thyroid cartilage and upper trachea
consists of
two lateral lobes
isthmus
pyramidal lobe (may or may not be)
31. Follicles are the thyroid morpho-functional units
are spherical cyst-like compartments
consist of
basal lamina
epithelial cells - thyrocytes
colloid
32. Thyroid follicles are surrounded by rich capillary network
capillaries are
fenestrated sinusoidal
⇔
33. Thyrocytes or follicular cells
are epithelial cells
arise from the endoderm
are cuboidal in shape
rest on the basal membrane
are in contact with the colloid
34. Thyrocytes secrete protein hormones
Thyroxine (tetraiodothyronine) – T4
Triiodothyronine – T3
Hormones regulate
cell and tissue basal metabolism
cell growth and cell differentiation
35. Colloid takes part in hormone synthesis
Colloid contains
thyroglobulin - iodinated glycoprotein
several enzymes
Thyroglobulin is inactive storage form
of the thyroid hormones
36. synthesis and secretion of thyroglobulin
concentration of iodide, oxidation to iodine,
and release to the colloid
formation of T3 and T4 hormones by iodination
resorption of colloid by endocytosis
release of hormones from cells into circulation
resorption vacuoles ⇒
⇐
37. Hyperfunction and hypofunction of the thyroid gland
Hyperfunction Hypofunction
Follicular cell shape Columnar Flat
Follicle diameter Smaller Larger
Colloid volume Decreases Increases
Resorption vacuoles More in number Less in number
38. Thyrocytes are the adenohypophysis-dependent cells
are stimulated by TSH from the pars distalis
release of T3 and T4 is regulated by
a simple feed-back system ⇒
39. Parafollicular cells or C-cells
arise from the neural crest
occur in follicle wall or interfollicular spaces
contain numerous secretory granules
40. Parafollicular cells secrete protein hormone calcitonin
lowers the blood calcium level
⇓
suppresses bone resorption
stimulates bone calcification
are the adenohypiphysis-independent cells
are regulated by the blood calcium level
43. Endocrine cells are arranged in cords
Principal or chief cells ⇒ parathyroid hormone (PTH)
Oxyphil cells (unknown function)
44. Parathyroid hormone is antagonist to calcitonin
increases the blood calcium level
⇓
stimulates bone resorption
reduces the kidney calcium excretion
activates the intestine calcium absorption
45. Parathyroid gland is the adenohypophysis-independent
is directly regulated by the blood calcium level
Simple feedback system:
low calcium levels
⇓
stimulate PTH secretion
high calcium levels
⇓
inhibit PTH secretion
46. Adrenal (suprarenal) glands
are paired glands
are located at the kidney superior poles
are subdivided in cortex and medulla
51. Zona glomerulosa
cells are arranged in ovoid clusters
secretes mineralocorticoids (aldosterone)
is regulated by renin-angiotensin system
and ACTH
54. Zona fasciculata cell ultrastructure
is characteristics of steroid-secreting cells:
well-developed SER
numerous mitochondria with tubular
and vesicular cristae
well-developed Golgi complex
numerous lipid droplets
55. Zona fasciculata secretion
secretes glucocorticoids (cortisol, corticosterone)
hormone effects:
regulate gluconeogenesis and glycogenesis
depress immune and inflammatory response
59. Adrenal medulla
arises from the neural crest
consists of modified neural cells
secretes catecholamine hormones
is adenohypophysis-independent
⇔
60. Adrenal medulla cells
are called chromaffin cells
secrete norepinephrine and epinephrine
are regulated by preganglionic sympathetic nerve fibers
glucocorticoids induce norepinephrine to epinephrin
conversation
61. Adrenal medulla hormone effects
rise in blood pressure
dilation of the coronary vessels
increase in the heart rate
⇔