endocrine and exocrine glands Flashcards
what are glands?
epithelial cells which produce secretion
what is the origin of glands?
ectodermal
name the two types of glands
endocrine and exocrine
which glands produce hormones?
endocrine
which glands have ducts?
exocrine
where do endocrine glands secrete their hormones?
out of the cell, into the interstitial tissue then into the capillaries scattered within the endocrine gland tissues- the horomones enter the bloodstream
where do exocrine glands secrete their many different substances?
into the lumen or organ surface through ducts
where can endocrine glands be found?
- as part of the epithelial surface (eg lining of GIT)
- or as separate organs (eg thyroid gland)
what is the function of the secretions produced by the endocrine gland?
(hormones) function to regulate bodily functions and maintain homeostasis
what is homeostasis?
the body’s steady state of equilibrium
what are the possible patterns of hormone secretion?
- chronic
- acute
- episodic
describe chronic pattern of hormone secretion
hormones secreted at regular intervals
what is an example of a hormone with a chronic pattern of secretion?
thyroxine
describe acute pattern of hormone secretion
the amount of hormone secreted depends on the stimulus (some stimuli cause large secretions some cause smaller secretions)
what are examples of hormones which have an acute secretion pattern?
adrenaline and cortisol
describe an episodic pattern of hormone secretion?
increased secretion following eating
what is an example of a hormone which has an episodic pattern of secretion?
insulin
what are the three mechanisms that can regulate hormone secretion?
- humoral
- neural
- hormonal
how does humoral hormone secretion regulation occur?
by the presence of certain blood borne molecules
what is an example of humoral hormone secretion regulation?
high glucose levels stimulates insulin secretion
how does neural hormone secretion regulation occur?
neurons stimulate hormone production
what is an example of neural hormone regulation?
sympathetic nervous system (fight or flight) stimulates epinephrine release
how does hormonal hormone regulation occur?
hormone secretion stimulates another hormone to be secreted
what is an example of hormonal hormone regulation?
hormones from pituitary glands stimulate testes to make testosterone
what are the three classes of hormones?
- proteins and polypeptides secreted by the pancreas and parathyroid gland (stored in the cell and released when needed)
- steroids are synthesised in the adrenal cortex, ovaries and placenta (synthesised from cholesterol and released directly into the circulation and cannot be stored
- derivates of amino acid tyrosine (adrenal medulla and thyroid)
what is the function of the hypothalamus?
it makes hormones that control the pituitary gland and makes hormones that are stored in the pituitary gland
what is the function of the pituitary gland?
produces hormones that regulate many of the other endocrine glands
what is the function of the parathyroid glands (there’s four)?
release parathyroid hormone which regulates the level of calcium in the blood
what is the function of the thymus?
during childhood, it releases thymosin which stimulates Tcell development
what is the function of the adrenal glands?
release epinephrine and nonepinephrine which help the body deal with stress
what is the function of the testes?
produces testosterone which is responsible for sperm production and the development of male secondary sex characteristics
what is the function of the ovaries?
produce estrogen which is required for the development of secondary sex characteristics and development of eggs- propesterone prepares the uterus for a fertilised egg
what is the function of the pancreas?
produces insulin and glucagon which regulate glucose levels in the blood
what is the function of the thyroid?
produces thyroxine which regulated the metabolism
what is the function of the pineal gland?
it releases melatonin which is involved in rhythmic activities eg daily sleep-wake cycles
where is the thyroid gland located?
it is an endocrine gland located in the midline of the neck in front of the trachea
what is the thyroid gland formed up of>
two parts joined by the central isthmus
what is the main bulk of the thyroid gland made up of?
follicles- lined by a single layer of cuboidal epithelium (follicular epithelium)- these follicles secrete and store colliod (contains thyroxine T3 and tri-iodothyroxine T3- the active hormone)- the shape of the epithelium can change to columnar when it is active
what is the the rest of the thyroid made up of (not follicles)?
C cell- parafollicular cell- clear cytoplasm and present in the interstitial tissue surrounding the follicles- produce calcitonin (a hormone which helps keep the calcium level in the body within a normal range)- c cells are physiological antagonists to parathyroid hormones and therefore lower blood calcium levels by suppressing the osteoclastic resorption of bone
where do the 4 parathyroid glands sit?
in the 4 corners of the thyroid gland
what hormone do the parathyroid glands produce and what is the hormones function?
parathyroid- important in calcium metabolism in the body- acts on osteoclasts so when calcium and other minerals levels decrease, the parathyroid glands secrete the hormone and this activates the osteoclasts to breakdown bone where these minerals are released and bring the levels back up to a normal range, when hormone secretion stops
what happens in some conditions where there is increased activity or size of parathyroid glands (eg benign tumours or hyperplasia)?
this results in increases hormone secretion, increased bone resorption and increased calcium level. The bone shows soft tissue lesions developing within the mineralised tissue. The jaw bones in addition to bones of the skull may also be affected by the hyperparathyroidism along with the rest of the skeletal system
what are the 3 most important hormones in calcium metabolism?
- calcitonin
- parathyroid hormone
- vitamin D
what are the two cell populations within the parathyroid glands?
- chief cells
- oxyphil cells
what is the function of the chief cell population in the parathyroid glands?
form the majority of the gland and synthesise and secrete parathyroid hormone
what is the function of the oxyphil cell population in the parathyroid glands?
present in clusters, less numerous than chief cells and larger, ‘transitional form’ of chief cells, granular cytoplasm due to large no. of mitochondria
how are exocrine glands classified?
by structure or method of secretion
describe classification of exocrine glands by structure
- unicellular
- or multicellular (secretory sheet or pockets of gland cells set back from epithelium surface)
what is an acini?
a small sack-like cavity in a gland surrounded by secretory glands
what are the names and locations of simple structures of exocrine glands?
- simple tubular (stomach and colon)
- simple branched tubular (lower stomach)
- simple coiled tubular (lower stomach and small intestine)
- simple acinar (sebaceous glands of skin)
- simple branched acinar (sebaceous glands of skin)
what are the names and locations of compound structures of exocrine glands?
- compound tubular (mucous glands of the duodenum)
- compound acinar (mammary glands)
- compound tubuloacinar (pancreas)
what are different methods of secretion?
- into duct
- pinched off cell storage
- cell shedding into duct after death
how does the merocrine gland secrete?
vesicles release contents into the duct eg saliva
how does the apocrine gland secrete?
product produced is stored in the cell then the top part of the cell separates containing the secretion eg mammary glands
how does the holocrine gland secrete?
the cells shed into the duct and the dying cell releases secretory products and a replacement cell forms
what are the different types of secretions?
- serous
- mucous
-seromucous
describe serous gland secretion
watery, containing enzymes
describe mucous gland secretion
secrete mucins which hydrate to form mucous- also contain glycoproteins
how do serous glands appear under a microscope?
- darker
- round shaped
- larger-produced by pink coloured acini
- stain pink with H&E
- nuclei in centre of cells
how do mucous glands appear under a microscope?
-paler
- flat
- foamy cytoplasm
- flat nuclei in outer aspect of the cells
what’s an example of a gland which produced both serous and mucous saliva?
submandibular gland
what’s an example of a gland which produced both serous and mucous saliva?
submandibular gland
what are the major salivary glands (pairs)?
- parotid- serous
- submandibular- mixed
- sublingual- mucous
where are the minor salivary glands located?
scattered all over the oral cavity
where are the major salivary glands located?
parotid- largest- just infront of ears
submandibular- smaller- just below jaw
sublingual- smallest- below floor of mouth and sides of tongue
what is xerostomia?
dry mouth
what type of gland is the pancreas?
mixed (endo 2% and exo 98%)
what does the pancreas secrete?
islets of langerhans contain 4 types of cells
- beta cells- secrete insulin
- alpha cells- secrete glucagon
- delta cells- secrete somastatin and gastrin
- f cells- secrete pancreatic polypeptide
what are diseases of the pancreas?
- pancreatic cancer
- diabetes mellitus (most common endocrine disorder)
describe the different types of diabetes
- Type 1. Insulin dependent. Destruction of beta cells. 5-10% of all diabetic patients.
- Type 2. Insulin resistant. Tissues lose their sensitivity to insulin so becomes ineffective
- Both have effects on most systems in the body.
what is the function of insulin?
promotes uptake of glucose by most cells, particularly those of the liver, skeletal muscle and adipose tissue, thus lowering plasma glucose concentration. It opposes the actions of glucagon, which promotes gluconeogenesis in the liver.
what is the function of insulin?
promotes uptake of glucose by most cells, particularly those of the liver, skeletal muscle and adipose tissue, thus lowering plasma glucose concentration. It opposes the actions of glucagon, which promotes gluconeogenesis in the liver.
what is the medical term for high blood sugar?
hyperglyceamia
what are the oral effects of diabetes?
- Periodontitis- inflammation of tissue that supports the tooth- leads to early loss of teeth
- xerostomia- gives difficulty eating, swallowing etc making them more susceptible to periodontitis etc and fungal infections eg thrush as less saliva
- susceptibility to infections
what are disorders of the endocrine system (endocrinopathies)?
- Reduced hormone release (hypofunction)
- Excessive hormone release (hyperfunction)
- Hormone resistance. (Diabetes mellitus) cannot carry out function- nothing wrong
- Endocrine changes may be seen in pregnancy, menopause, stress, obesity etc.
