Endocrine System Flashcards
What does the endocrine system produce?
various secretions:
- hormones
- hormonally active substances
Where do hormones and hormonally active substances go?
- enter the circulatory system
- transport to target cells
What classes are hormones and hormonally active substances divided into?
Peptides:
- insulin
- GH
- ACTH
Steroids:
- gonadal
- adrenocortical steroids
Amino Acids / Arachidonic Acid Analogs:
- catecholamines
- prostaglandins
What is the function of the endocrine system?
- coordinates cell activities (organelles and tissues)
- maintains homeostasis
What are endocrine glands?
Glands whose major function is to secrete hormones.
State the endocrine part of the pancreas.
endocrine
exocrine- digestion (duct –> enzyme secretion)
What is the difference between endocrine and exocrine glands?
endocrine glands: no ducts! (secrete is always hormones!) released into circulatory system!
exocrine glands: has a duct system!
What is a different name used to describe the pituitary gland?
hypophysis
What two parts is the pituitary gland composed of?
1) Anterior Lobe (adenohypophysis):
- glandular epithelial tissues consisting of 3 parts: pars distalis, intermedia and tuberalis.
2) Posterior Lobe (neurohypophysis):
- neural secretory tissue
- developed from the neuroectoderm of the CNS
What is the anterior lobe of the pituitary gland made up of? Other name?
anterior lobe = adenohypophysis
GLANDULAR EPITHELIAL TISSUES
- pars distalis
- pars intermedia
- pars tuberalis
What is the posterior lobe of the pituitary gland made up of? Other name?
posterior lobe = neurohypophysis
NEURAL SECRETORY TISSUE
- developed from the neuroectoderm of the CNS
State the overall key points about the pituitary gland.
- small gland
- attached to the inferior surface of the brain
What similarities do the two pituitary lobes share?
rich capillary network (necessary for picking up secreting hormones)
Which part of the anterior lobe glandular epithelial cells is most histologically important? Why?
pars distalis: produces most hormones
State the histological composition of the pituitary gland.
- connective tissue stroma (supporting parenchymal cells) (between secretory cells)
- secretory cells
- secretory granules in pars distalis are identified as basophils (10%), acidophils (40%) and chromophobes (50%)
How are cells in the pars distalis of the pituitary gland identified? Into what?
- based on staining reactions
endocrine cell secretory granules:
- basophils (10%), (blue - hematoxylin)
- acidophils (40%) (dark red - eosin dye)
- chromophobes (50%) (orange/clear - (dye)phobia)
impossible to depict which cell produces which hormone!
What makes up most of the posterior lobe of the pituitary gland? Other name?
Pituitary gland = hypophysis
- extention of the CNS
Axons (projecting from the neuron cell bodies in the supraoptic and paraventricular nuclei of the hypothalamus) make up most of the posterior lobe.
What is the function of the pituitary gland?
releases hormones
produced in the supraoptic nuclei of the hypothalamus:
- antidiuretichormone [ADH]
- vasopressin
paraventricular nuclei of the hypothalamus:
- oxytocin
Where are hormones produced for the pituitary gland?
in the hypothalAmus
What is the greatest difference between the anterior and posterior lobes of the hypophysis?
anterior lobe: produces hormones (secratory epithelial cells);
posterior lobe: stores hormones and releases them at specific times.
What is another name used for the Epiphysis Cerebri?
pinneal gland
What is the epiphysis surrounded by?
pia mater capsule
State the composition of the epiphysis cerebri.
Pinealocytes:
- primary cells
- large
- basophilic cells
- round nuclei
- secrete melatonin (association with circadian rhythms)
Astrocytes:
- interdigitate between the pinealocytes and capillaries
- astocyte like neuroglial cells (metabolism associated)
What is the stroma of the epiphysis cerebri based on?
pia mater
What is a special structural component found in the epiphysis cerebri? What is its function? What is it composed of?
Corpora Arenacea:
- intercellular calcium deposits
- associated with aging (accumulate with age)
- do not seem to affect glandular function.
-
light-sensitive endocrine organ is
responsible for the production of
melatonin and serotonin. - histological importance: helps indicate the specific location of the epiphysis cerebri
known as “brain sand”
What is the thyroid gland surrounded by?
connective tissue capsule:
- fine septa between the
follicles
State the arrangement of the parenchyma of the thyroid gland.
- spherical follicles
- surrounded by a dense capillary
network
State the histological composition of the thyroid gland.
(1) surrounded by a connective tissue capsule (fine septa b/w follicles).
(2) parenchyma arranged in spherical follicles (size varies with activity)
- size of follicles varies with
activity
- epithelium of follicles consists of
follicular lining cells ** (squamous - columnar)
- acidophilic lining with
numerous cytoplasmic secretory
vesicles, a basal nucleus and microvilli (apical surface).
(3)surrounded by a dense capillary
network.
squamous- no hormone production
columnar- hormone producting
What is a specific feature of the thyroid gland?
Usually glands are made up of a homogenous mass, yet the thyroid gland has follicles (spherical structure compartments).
What is the function of follicular cells? Where does this process take place?
produce thyroid hormones T4 and T3.
synthesis takes place in:
- follicular cells
- lumen of the follicle.
What is the function of parafollicular cells?
produce calcitonin (calcium level regulation).
State the composition of the follicle lumen.
Lumen is filled with a gellike mass called colloid, which contains
thyroglobulin, an inactive storage form of thyroid hormones.
State the location of the parafollicular cells. How can they be depicted? Other name?
Parafollicular cells = C cells
Location:
- outside the follicular lining epithelium
- do not extend to the lumen of the
follicle.
Depiction:
- lighter staining
- larger
- oval in shape
What is an additional structure surrounding all glands?
rich network of blood vessels!
What are the two cells present in the thyroid gland?
- follicular cells (in the follicle)
- parafollicular cells (near follicles)
State the location of the parathyroid gland. Birds?
External parathyroid glands:
- cranial pole of the thyroid
- ABSENT in birds and pigs
Internal parathyroid glands:
- caudal pole
- (embedded within the thyroid tissue)
What surrounds the parathyroid gland? What does it blend with?
thin connective tissue capsule
- blends with the thyroid connective tissue
thin connective tissue = stroma
What extends from the capsule of the parathyroid gland into the parenchyma? What does it contain?
Fine septa extend from the capsule into
the parenchyma and contain the rich
endocrine blood supply.
Is it possible to depics two glands in one histological slide?
yes! the thyroid and parathyroid gland!
What is the parenchymal part of the parathyroid gland composed of?
Principal cells = Chief Cells:
- polygonal cells
- round nucleus
- clear cytoplasm
- actively produce parathyroid
hormone (PTH) (increases
blood calcium levels).
Oxyphil cells:
- inactive (function is unknown)
- larger
- more intensive colour (pink)
- prominent cell membranes
- cytoplasm contains glycogen or lipofuscin.
What is the function of the parathyroid hormone?
Parathyroid Hormone (PTH):
- increases blood calcium levels
- increases mobilization of calcium from bone
- increases calcium absorption in the intestines,
- reduces calcium loss in the urine
State the positioning of the two cells of the parathyroid gland.
no specific location!
chief cells and oxyphil cells are mixed together.
What are suprarenal glands? Where are they located? What do they represent?
Suprarenal Glands = Adrenal Glands
- adjacent to the cranial medial border
of the kidneys
- represent two distinct endocrine tissues.
State the major functions of the suprarenal glands. How is it regulated?
Outer cortex secretes steroid hormones.
Medulla produces catecholamines.
- Hormone production is regulated
independently.
What is the suprarenal gland surrounded with? How does this connect with the parenchyma? What is its function?
surrounded by: dense fibrous connective tissue capsule.
- Connective tissue trabecula extend into the parenchyma from the capsule and a fine
stroma supports the glandular cells.
Why is the name of the gland called “suprarenal” instead of “adrenal”?
Adrenal= humans, gland positioned ON-TOP of the kidney
Suprarenal= (kidneys are horizontal), gland is INFRONT of the kidney
What does the ‘suprarenal’ organ qualify as?
double origin organ:
- cortex
- inner medulla
completely different parts, origin and cells –> produce different hormones
What is the function of the suprarenal gland medulla and cortex? (simply)
medulla: similar to the autonomic nervous system
cortex: hormone producing glands
What are the different zones of the supranatal cortex?
CAPSULE
1) zona glomerulosa
2) zona fasciculata
3) zona reticularis
ADRENAL MEDULLA
State the arrangement of cells in the suprarenal cortex.
- arranged in cords or glomerular
structures - cells: cuboidal/columnar or polygonal
- 3 zones
- 4 zones in horses and carnivores
State the composition of the zona glomerulosa.
- suprarenal cortex
- outermost layer
- outer zone adjacent to the capsule
- cells arranged in glomeruli or curved
cords - small cells! large nucleus! –> cells look darker!
What is the special zone of carnivores and horses? Where is it located? What is it composed of?
Zona Intermedia
- small undifferentiated cells
- present between the zona
glomerulosa and zona fasiculata
- in horses and carnivores.
State the composition of the zona fasciculata.
- characteristic foamy cytoplasm
–> large amount of lipid. - widest zones
- larger cells
- arranged in columns –> linear pattern arrangement
State the composition of the zona reticularis.
- smaller cells
-
no specific arrangement
–> 3D network - cytoplasm may have brown pigment–> darker appearance
- adjacent to the suprarenal medulla
- innermost zone of the cortex
What hormones are produced in the zona glomerulosa? What produces them?
Zona glomerulosa cells form ovoid clusters and produce mineralocorticoids (aldosterone).
What hormones are produced in the zona fasciculata? What produces them?
Zona fasciculata cells are arranged in long straight cords and produce glucocorticoids (cortisol).
stress hormone!
What hormones are produced in the zona reticularis? What produces them?
Zona reticularis cells are arranged in anastomosing cords produce weak androgens.
State the composition of the suprarenal medulla. What is it composed of? What cell populations are present in animals? What do they contain?
Medullary Endocrine Cells = Chromaffin Cells
- clear cytoplasm
- modified postganglionic sympathetic neurons
- In animals, two populations of endocrine cells are recognized based on the
catecholamines present in cytoplasmic
membrane-bounded dense granules.
contain one of the catecholamines: - adrenalin (epinephrine)
-
noradrenalin (norepinephrine),
+ chromogranins (binding proteins for the catecholamines)
What is the function of chromogranins? Where are they found?
- in cytoplasmic membrane-bounded dense granules.
- binding proteins for the catecholamines
What surrounds chromaffin cells? How are they arranged?
- arranged in clumps
- surrounded by sinusoidal capillaries
How do chromaffin cells look like?
- clear cytoplasm
- may appear brown due to the oxidation process
What cells are present in the suprarenal gland? How do they look? What are they composed of?
Epinephrine cells:
- light chromaffin stains
- majority of medullary cells
Norepinephrine cells:
- dark chromaffin stains
- minority of medullary cells
State the structure of pancreatic islets. Other name?
Endocrine pancreatic islets = islets of Langerhans:
- scattered among exocrine secretory units.
- clusters of endocrine cells.
- connected by gap junctions (facilitate intercellular communication)
Explain Type A pancreatic islets.
- dense cytoplasmic granules.
- secretes glucagon, cholecystokinin, gastric inhibitory protein and ACTH-endorphin.
State the function of type A pancreatic cell secretions.
-
Glucagon stimulates glycogen breakdown which increases blood glucose
levels. -
Cholecystokinin stimulates contraction of the gallbladder and release of
pancreatic enzymes. -
Gastric inihibitory protein inhibits the secretion of gastric acid and pepsin
and stimulates the release of insulin in the pancreas.
Explain Type B pancreatic islets.
- most numerous cell in the islet.
- produce proinsulin
State the function of type B pancreatic cell secretions.
During transport from the Golgi apparatus to the cell surface, the proinsulin is converted to insulin.
- The secretory vesicles fuse with the cell membrane, insulin is released, and the hormone enters nearby capillaries.
Explain Type D pancreatic islets.
- large
- pale cytoplasmic granules.
- secrete: somatostatin and vasoactive intestinal peptide (VIP)
State the function of type D pancreatic cell secretions.
- Somatostatin inhibits insulin and glucagon secretion in a local paracrine fashion.
- VIP induces glycogen break down and stimulates gastrointestinal fluid secretion.
State the names of other pancreatic islets. What are their functions?
Pancreatic polypeptide cells (PP
cells or F cells):
- increases glycogenolysis and regulates gastrointestinal activity.
G cells.
- stimulates production of gastric
acid by parietal cells in the stomach.
State the composition of testis. What cells? What is secreted?
Leydig cells = interstitial cells
- found near the seminiferous
tubules in the testicle.
- round/polyhedral
- large nucleus.
- produce testosterone.
Is it possible to distinguish between the different pacreatic islet cells?
NO!
- but its possible to depict the pancreatic islet themselves
State the composition of ovaries. What cells? What is secreted?
- granulosa cells
-
thecal cells
produce ovarian hormones.
(Other places where estrogens are produced: liver, pancreas, adrenal glands, skin,
brain, adipose tissue etc.)
State the composition of the corpus luteum. What cells? What is secreted?
The granulosa cells and thecal cells enlarge and transforms to endocrinous cell
populations of the corpus luteum.
Two different types of endocrinous cells:
- Granulated luteocytes (develop from granulosa cells)
- Thecaluteocytes (develop from theca cells)
Produces hormone progesterone
State the composition of the adipose tissue. What cells? What is secreted?
Produces leptin, adiponectic and resistin
- regulates energy metabolism
