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