Endocrine system
Hormonal regulation
Endocrine glands
• Glands w/o ducts
• Secretory cells release their products,
hormones, into the extracellular space
and blood stream
• Alternatively, the hormones may affect
neighbor cells (paracrine)
• Structure:
• c.t. – capsule + septs
• irregular clumps or cords of the cells
• network of capillaries
• fenestrated capillaries
• sinusoids
Hypophysis – pituitary gland
Pituitary gland – anterior pituitary
 Chromophilic cells
- Acidophilic cells (produce proteins)
somatotrophs
mammotrophs (or lactotrophs)
- Basophilic cells (produce glycoproteins)
 thyrotrophs produce thyroid
stimulating hormone (TSH or
thyrotropin).
 gonadotrophs produce follicle
stimulating hormone (FSH) and
luteinizing hormone (LH)
 corticotrophs (or adrenocorticolipotrophs)
 Chromophobic cells
Pituitary gland – anterior pituitary
Adenohypophysis
Adenohypophysis
orange G + PAS
Neurohypophysis x Adenohypophysis
Neurohypophysis - structure
 Structure
 unmyelinated nerve fibres derived from neurosecretory cells of the supraoptic
and paraventricular hypothalamic nuclei
 pituicytes /neuroglia/
 Function
 Two hormones are oxytocin, which stimulates the contraction of smooth muscle
cell in the uterus and participates in the milk ejection reflex, and antidiuretic
hormone (ADH or vasopressin), which facilitates the concentration of urine in the
kidneys and, thereby, the retention of water.
 Usually only the oval or round nuclei of the pituicytes are visible. Hypothalamic nerve
fibres typically terminate close to capillaries. Scattered, large masses represent
dilations of these nerve fibres - Herring bodies - are filled by small vesicles which
contain the neurosecretory products of the hypothalamic cells.
Neurohypophysis
Neurohypophysis
Herring bodies
Pineal body (epiphysis cerebri)
Pineal body
 is surrounded by pia mater, which
functions as its capsule and which
sends c.t. septa into the pineal body,
subdividing it into lobules
 two cell types and unmyelinated nerve
fibers
 pinealocytes (about 95% of the cells;
large, light and round nuclei)
 astrocytes (glial cells; dark,
elongated nuclei)
 both pinealocytes and astrocytes
have long processes which give the
tissue between the nuclei its "stringy"
appearance
 the most prominent secretory product of
the pineal body is melatonin - decrease
secretory activity in most other
endocrine glands and may "delay"
puberty through antigonadotrophic
effects.
 secretory activity in the pineal gland is
stimulated by darkness and inhibited by
light
Pineal body
brain sand (or acervulus cerebri or corpora arenacea) - calcium-containing
concretions which increase in size and number with age /are radioopaque/
Thyroid gland
 Thyroid hormones (T3, T4)
increase metabolic activity in almost
all tissues and organs. Many of the
other effects of the hormones are
secondary to an increased oxygen
consumption of the affected cells.
 C cells produce the hormone
calcitonin, which decreases blood
calcium concentration
lobes→lobules - follicles
20 g
Thyroid gland
Follicles /50 µm to about 1 mm/, which are separated by scant interfollicular c.t. It consists of a
simple cuboidal epithelium which surrounds a lumen filled with a viscous substance, colloid.
Thyroid gland - follicles
C cells (or parafollicular cells) are only few of them, typically situated basally in the
epithelium, without direct contact with the follicular lumen. They are always situated within the
basement membrane, which surrounds the entire follicle.
thyroglobulin, consists
of triiodothyronine T3
and
tetraiodothyronine
(thyroxine) T4
C-cells
Glandula thyreoidea
Parathyroid gland
c.t. /capsule+septs/
network of the capillaries
cords or clumps of the cells
6 mm, 130 mg
/total weight/
Parathyroid gland
 Chief cells are the most
numerous type. They are small
cells /7-10 µm/ with round, big and
centrally placed nucleus and a
small amounts of cytoplasm /very
weakly acidophilic/.
 Oxyphilic cells
less frequent (occurring first in
children 6-7 years old and
increasing with age), larger their
cytoplasm is strongly
acidophilic, the nucleus is round.
They contain large amounts of
mitochondria and glycogen.
 Fat cells (adipocytes)
Glandula parathyreoidea
Parathyroid gland
Synthesise parathyroid hormone (PTH or
parathormone) which is of pivotal
importance for normal calcium
concentrations in the fluids and tissues of
the body. The effect is mediated by a
stimulation of osteoclastic bone resorption,
intestinal calcium uptake and calcium
resorption in the kidneys
Suprarenal gland
c.t. : capsule+septs network of capillaries
cords of the cells
Suprarenal gland - cortex
Zona glomerulosa (1/10)
Zona fasciculata (6/10)
Zona reticularis (3/10)
Glandula suprarenalis
Suprarenal gland - function
 Hormones produced in the cortex are all steroids - cortical cells contain
large amounts of AER, lipid droplets and mitochondria with tubules. Since
the hormones are synthesised in the cortex they are more termed
corticosteroids.
mineralocorticoids
glucocorticoids
 The most important mineralocorticoid is aldosterone, which regulates the
resorption of sodium and excretion of potassium in the tubules of the kidney
– zona glomerulosa.
 The most important glucocorticoids is cortisol, which has a wide range of
effects on most cells of the body. Cortisol effects protein catabolism in
almost all cells aside from liver cells, gluconeogenesis, glycogen storage,
mobilisation of fat from adipocytes, anti-inflammatory effects, inhibition of
allergic reactions – zona fasciculata.
 Small amounts of androgens, oestrogens and progesterone are also
produced – zona reticularis.
 Both the zona fasciculata and zona reticularis depend on ACTH.
Suprarenal gland - medulla
 Cells are arranged in strands or small
clusters in reticular c.t. chromaffin
cells because the granules
of these cells can be stained with
potassium bichromate and also some
ganglion cells.
 Chromaffin cells correspond to the
adrenaline - (80%) and noradrenaline producing
cells of the medulla. The
two groups cannot be distinguished
using routine histology.
 Chromaffin cells are innervated by
preganglionic sympathetic fibres and
correspond functionally to
postganglionic neurones. The
correspondence is not only functional chromaffin
cells are, like ganglion cells
of the PNS, derived from neural crest
cells.
Islets of Langerhans
 Groups of pale cells
 cca 1,5  106
 Thin c.t. capsula
 Epithelial-like cords of cells
 Sinusoids
 Cell types: A, B, D, PP
A cells: 20%, glukagon
B cells: 60-70%, insulin
D cells: minor, somatostatin
PP cells: minor, pancreatic polypeptide
Islets of Langerhans
List of slides
 52. Hypophysis cerebri
 53. Epiphysis
 54. Glandula thyreoidea
 55. Glandula
parathyroidea
 56. Corpus suprarenale
 23. Pancreas – islets of
Langerhans