Histology II: endocrine organs Flashcards
The endocrine- and nervous system do what together?
regulate metabolic activity of the different organs and tissues of the body so as to maintain homeostasis.
Endocrine glands secrete the hormones where?
directly into the blood or lymph
Name 10 endocrine glands.
adrenal glands
hypophysis (pituitary)
hypothalamus
pancreas (islets in the pancreas)
parathyroid glands
pineal gland
placenta
testes and ovaries
thymus
thyroid gland
Another name for the hypophysis.
pituitary gland
Which endocrine glands can be found in the brain?
hypothalamus
pineal gland
pituitary gland (hypophysis)
Name the “central” endocrine organs.
hypophysis
hypothalamus
Name the peripheral endocrine organs.
adrenal glands
parathyroid glands
pineal gland
thyroid gland
Name the endocrine organs that have functions in addition to hormone production and secretion.
pancreas
placenta
testes and ovaries
thymus
Where is the pituitary gland located?
centrally located at the base of the brain
The hypophysis has what two functional components?
Adenohypophysis
Neurohypophysis
What is the adenohypophysis?
the anterior lobe of the pituitary gland, the glandular epithelial tissue part
What is the neurohypophysis?
the posterior lobe of the pituitary gland, the neural secretory tissue part
The neurohypophysis produces what two hormones?
Oxytocin
Vasopressin/ADH
What is the function of oxytocin?
stimulates activity of mammary glands
stimulates contractions of the uterus
promotes maternal behavior
What is the function of vasopressin?
maintains osmolality
decreases urine volume
increases blood pressure
Another name for vasopressin.
antidiuretic hormone (ADH)
The adenohypophysis produces what 6 hormones?
Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Growth hormone (GH) Luteinizing hormone (LH) Prolactin (PRL) Thyroid stimulating hormone or thyrotropin (TSH)
Function of PRL?
promotes mammary gland development and milk production
Function of LH?
regulates final maturation of ovarian follicle, androgen secretion in testis
Function of TSH?
regulates growth of thyroid epithelial cells and regulate the production of hormones by the thyroid gland
Function of GH?
stimulates body growth
Function of ACTH?
stimulates secretion of cortisol in adrenal cortex
Function of FSH?
stimulates follicular development of the ovary and spermatogenesis in testis
Where is the hypothalamus located?
Located in the middle at the base of the brain.
Function of the hypothalamus?
Regulates activity of the hypophysis.
What is the diencephalon?
The diencephalon connects the midbrain to the forebrain.
It is located deep within the brain and comprises the epithalamus, thalamus, subthalamus and hypothalamus.
Where is the pineal gland located?
deep in the brain in an area called the epithalamus, where the two halves of the brain join.
The epithalamus is a part of the diencephalon.
Function of the pineal gland?
receive information about the state of the light-dark cycle from the environment and convey this information to produce and secrete the hormone melatonin
Describe the location of the pineal gland in reptiles and lower vertebrates.
the pineal lies at or near the skin surface where it functions as a photoreceptor organ
(“third or parietal eye”)
Describe the function of the pineal gland in reptiles and lower vertebrates.
functions as a photoreceptor organ secreting the hormone melatonin which lightens skin color by its action on melanophores, pigmented cell analogues to melanocytes in mammals
Where is the thyroid gland located?
Located in the anterior neck region, just caudal to the larynx, adjacent to the lateral surface of the trachea.
Main parts of the thyroid?
2 lobes that are separated from each other by fibrous connective tissue trabeculae
Thyroid follicles filled with?
colloid
The parenchyma of the thyroid consists of?
follicles, lined with simple epithelium
The epithelial cells between thyroid follicles form what?
parafollicular islets
What part of the thyroid is responsible for production of thyroxine?
Follicular cells
What part of the thyroid is responsible for production of calcitonin?
Parafollicular islets
Calcitonin function?
main actions of calcitonin are to increase bone calcium content and decrease the blood calcium level when it rises above normal.
also lowers blood phosphorus levels when they rise above normal
Where are the parathyroid glands located?
lie just behind the thyroid gland closely associated with it
Parathyroid function?
produces parathyroid hormone, which plays a key role in the regulation of calcium levels in the blood
Main diff. between the function of parathyroid hormone and calcitonin?
Parathyroid hormone acts to increase blood calcium levels, while calcitonin acts to decrease blood calcium levels.
Where are the adrenal glands located?
on the upper poles of the kidneys embedded in the perirenal fat
How many parathyroids are there generally?
4
Describe the morphology of the adrenals.
covered by thick connective tissue capsule;
the secretory parenchymal tissue is organized in cortical and medullary regions
Where is cortisol produced?
the adrenal cortex
What zones are the adrenal cortex divided into based on what?
zona glomerulosa
zona fasciculata
zona reticularis
based on location and structure of the epithelial cells and sinusoids
Describe zona glomerulosa
thin subcapsular zone;
synthesizes mineralocorticoids, mainly aldosterone and deoxycorticosterone
Describe zona fasciculata
occupies most of the adrenal cortex;
secretes glucocorticoids, mainly cortisol and corticosterone
Describe zona reticularis
composed of cells arranged in an anastomosing network of clumps and columns with a capillary network;
produces androgenic steroids and in small amounts, glucocorticoids
What is the adrenal medulla composed of?
a parenchyma called chromaffin cells (are modified neurons which have a secretory function) connective tissue, numerous sinusoidal blood capillaries, and nerves.
Function of chromaffin cells?
in effect, modified neurons which have a secretory function, produce norepinephrine and epinephrine.
What is the endocrine component of the pancreas?
Islets of Langerhans
Where can you find Islets of Langerhans more specifically?
scattered throughout the pancreas but are more numerous in tail region
Histological appearance of islets of langerhans?
appear as clusters of pale-stained cells surrounded by more intensely staining pancreatic acini.
What are the cell types in Islets of Langerhans?
B (beta) cells (approx. 70%)
A (alpha) cells (20%)
D (delta) cells (5-10%)
PP cells (1-2%)
What do beta islet cells secrete?
insulin
What do alpha islet cells secrete?
glucagon
What do delta islet cells secrete?
somatostatin
Somatostatin function?
inhibits glucagon and insulin release
What do PP islet cells secrete?
pancreatic polypeptides
Pancreatic polypeptide function?
It can inhibit gallbladder contraction and pancreatic exocrine secretion, but its role in the metabolism of nutrients is uncertain.
