Endocrine and Exocrine Flashcards
What are glands and what types are there?
Epithelial cells that produce secretions. Endocrine and Exocrine
What do endocrine glands do?
produce hormonal secretions into interstitial tissue then into capillaries. they have no ducts
How can endocrine glands exist?
these can be either part of an epithelial surface such as the lining of the GIT (gastrointestinal tract) or separate organs such as the thyroid or pituitary gland.
What do hormones produced do?
The hormones produced regulate bodily functions and maintain homeostasis.
What are the patterns of hormone secretion and what are some hormone examples of them?
Chronic - thyroxine (tetraiodothyronine)
Acute - adrenaline, cortisol
Episodic - insulin
What are the mechanisms that regulate hormone secretion
humoral (blood borne molecules such as high glucose in blood)
neural (neurons stimulate hormone production)
hormonal (hormone secretion stimulates another hormone to be secreted)
What are the classes of hormones and where are they stored?
proteins and polypeptides secreted by the pancreas and parathyroid can stored in cell
steroids secreted by ovaries, placenta, adrenal cortex, synthesised by cholesterol are released immediately and cannot be stored
derivatives of amino acid tyrosine secreted by the adrenal medulla and the thyroid
Where is the thyroid gland found?
The thyroid gland is located in the midline of the neck in front of the trachea.
Describe how the thyroid gland secretes hormones
Inactive hormones are stored in colliod surrounded by secretory cells, which make up a ‘follicle’.
These follicles are lined by a single layer of cuboidal epithelium that is known as follicular epithelium.
When this epithelium is active, the shape can change to a columnar epithelium.The follicular cells contain thyroxine T4 and tri-iodothyronine T3 which are the active hormone.
When the follicular epithelium of the thyroid gland is active, what is the shape change?
simple cuboidal to simple columnar
What other secretory cells are present in the thyroid gland and what do they secret?
c cells (parafollicular) secrete calcitonin which helps keep calcium levels in our body normal
How many parathyroid glands are there and where are they situated?
4 and in the corners of the thyroid glands
What does the parathyroid gland do?
It secretes hormones called the parathyroid hormone (PTH) which has effect on the osteoclasts which are responsible for bone resorption (breakdown)
What happens when calcium levels decrease?
When calcium and other minerals levels decrease, the parathyroid glands secrete the hormone and this activates the osteoclasts to break down bone. The minerals are then released into the body, bringing up the levels to within the normal range. Once normal level is reached, the hormone secretion stops.
What happens in the case of hyperparathyroidism and how is it caused?
caused by a benign tumour or hyperplasia of the gland. this results in increases hormone secretion, increased bone resorption and increased calcium level. eventual wear and lesion of jaw
What are the main hormones responsible for calcium metabolism?
calcitonin
PTH (parathyroid hormone)
vitamin D
What are the cells in the parathyroid gland?
chief cells (synthesise PTH), oxyphil cells
How do secretions of exocrine glands work?
secretions are released through ducts that open onto the epithelial surface
How are exocrine glands classified?
by structure or method of secretion
What are the exocrine, structure classifications?
Unicellular (goblet)
Multicellular -arranged in pockets or sheets
What are the types of multicellular structure?
duct system may be branched (compound gland) or unbranched (simple gland)
secretory component may be tubular or acinar
both types of secretory components may be coiled or branched
What are the exocrine methods of secretion and how do they function?
Merocrine gland produces substances stored in little bubbles (vesicles) in the cytoplasm. They are released into the duct and carried out to secrete. Mostly protein secretion
Apocrine produces substances that are carried with parts of the cells and leaves through the apical part –mammary glands
Holocrine produces substances that are carried with entire dying cells that secrete. Cells are replaced –sebum
What are the different types of multicellular glands and where are they found?
simple tubular - stomach, colon (large intestine)
simple branched tubular - lower portion of stomach
simple coiled tubular -lower portion of stomach and small intestine, sweat glands
simple acinar - sebaceous glands of skin
compound tubular - mucous glands of duodenum
compound acinar - mammary glands
compound tubiloacinar - pancreas
What are the types of secretions?
Serous –behind ears very protein rich (watery)
Mucous –contain glycoproteins, secrete mucins which hydrate to form mucus (thick)
Mixed glands –have both
What are the major salivary glands?
Parotid. Submandibular. Sublingual
What is specific about the pancreas?
it has both endocrine and exocrine glands
What are islets of langerhans and what cells do they secrete?
they are endocrine cells that secrete
insulin (beta cells)
glucagon (alpha cells)
somastatin and gastrin (nuclei of delta cells)
f cells (pancreatic polypeptide)
How does type one diabetes occur?
destruction of beta cells therefore no insulin secretion
What are the oral effects of diabetes?
dry mouth, periodontitis
What are the disorders of the endocrine systems (endocrinopathies)?
hypofunction (reduced hormone release)
hyperfunction (increased hormone release)
hormone resistance (diabetes mellitus)
What type of secretion is produced by blue-coloured acini in alcian blue and H&E stains?
mucous
What type of secretion is produced by pink-coloured acini in alcian blue and H&E stains?
serous, they have not taken up the blue stain
What do the parotid glands secrete?
parotid glands consist almost exclusively of serous cells and produce a thin watery secretion rich in enzymes and antibodies.
What type of secretion is produced by the magenta-stained cells in a PAS stain?
mucous
What kind of secretion do the submandibular glands secrete?
both serous and mucous secretory cells and produce a secretion of intermediate consistency.
What increases in the sublingual gland with age?
the proportion of adipose tissue (fat) in the gland generally increases with increasing age.
What type of secretion stains poorly with H&E?
mucous
Which salivary gland has similar histological features to the lacrimal gland
parotid gland
What are both mucous and serous acini surrounded by?
serous and mucous acini are surrounded by contractile cells called myoepithelial cells
Which halogen is essential for the endocrine function of the thyroid?
iodine
Why is the thyroid gland unique compared to other endocrine glands?
stores large amounts of hormone in an inactive form within extracellular compartments in the centre of follicles;
Which thyroid hormones are partially composed of iodine?
T3 (Triiodothyronine) and T4 (Tetraiodothyronine, also known as thyroxine) are iodine-containing hormones.
Which cells are responsible for the conversion of thyroglobulin, stored in the follicle, into T3 and T4?
Thyroid epithelial (follicular) cells
Which cells are responsible for the secretion of calcitonin?
C or parafollicular cells
The parathyroid hormone is produced by which cells?
chief cells
What best describes the function of the parathyroid hormone?
Stimulate osteoclast activity
What are the two components of the adrenal gland?
adrenal cortex, adrenal medulla
In the histological zone of the adrenal cortex, zona glomerulosa, describe the arrangement
lies beneath the capsule and contains
secretory cells arranged in rounded clusters.
In the histological zone of the adrenal cortex, zona fasciculata, describe the arrangement
the intermediate zona fasciculate consists of parallel cords of secretory cells disposed at right angles to the capsule.
In the histological zone of the adrenal cortex, zona reticularis, describe the arrangement
the zona reticularis lies close to the medulla and consists of small closely packed cells arranged in irregular cords. often the borders of the zones are less regular and less easily recognised than for the other zones.
Name the hormone produced within the zona glomerulosa?
aldosterone
Name the hormone produced within the zona fasciculata?
cortisol
Name the groups of hormones produced exclusively within the zona reticularis?
androgens
Why is rich vascularisation of the medulla required?
get important hormones such as adrenaline and noradrenaline around the body fast
Which type of cells do you find in the Islet of Langerhans?
alpha cells, beta cells, delta cells, pancreatic polypeptide (PP) cells
What is the function of insulin?
Promotes glucose uptake by most cells, Inhibits gluconeogenesis in the liver
What is the medical term for dry mouth?
xerostomia
Why do serous and mucous glands stain differently?
Mucous cells produce mucus, which doesn’t stain very darkly, so the mucous cells look almost clear on these images and on slides.
Serous cells produce a watery secretion that contains a lot of proteins. Serous cells stain fairly dark.
What does the liver secret?
bile
What kind of secretion does the sublingual gland have?
mostly mucous
What is the function of the thyroid hormone?
regulates the basal metabolic rate and has an important influence on growth and maturation, particularly of nerve tissue
What does calcitonin do?
Calcitonin lowers blood calcium levels by inhibiting the rate of decalcification of bone by osteoclastic resorption and by stimulating osteoblastic activity
Where is TSH secreted from?
pituitary gland
What hormones are example of tyrosine derivatives?
adrenaline
T3, T4
What is the embryological origin of glands?
ectoderm
