Endocrine and exocrine glands Flashcards
What cells make up glands?
Epithelial cells that produce secretions - ectodermal origin
What are endocrine glands?
Glands that produce secretions that are released into surrounding interstitial fluid which then enter the bloodstream via fenestrated capillaries.
Example of endocrine gland being part of an epithelial surface
lining of digestive tract contains G cells that produce gastrin
Examples of endocrine glands being separate organs
Pituitary gland, thyroid gland, pancreas
3 patterns of hormone secretion
chronic, acute, episodic
What is chronic hormone secretion?
Same amount of hormone secreted at regular intervals e.g. growth hormones like thyroxine
What is acute hormone secretion?
Large amount of hormone secreted at a particular time according to stimulus e.g. adrenaline/epinephrine
What is episodic hormone secretion?
Hormone secretion follows particular episode e.g. insulin secretion after meals
3 ways in which hormone secretion is regulated
humoral (blood-borne molecules e.g. blood glucose), neural, hormonal
What is an example of humoral regulation of hormone secretions?
High blood glucose levels stimulate insulin secretion
What is an example of neural regulation of hormonal secretion?
Sympathetic NS stimulates adrenaline release
What is n example of hormonal regulation of hormone secretion?
Hormones from the pituitary gland stimulate testes to make testosterone
3 classes of hormones
Protein/polypeptides, steroids, tyrosine derivatives
What class of hormones are secreted from the pancreas and parathyroid glands?
protein and polypeptide
what class of hormone is released from the adrenal cortex, ovaries, placenta?
steroids
what molecule are steroid hormones derived from?
cholesterol
What class of hormone is released from adrenal medulla and thyroid?
tyrosine
Structure of the thyroid
Made of 2 lobes joined by isthmus. 4 parathyroid glands sit in each corner of the thyroid gland and are separated from the thyroid by fibrous tissue capsule.
What components make up the thyroid gland (histology)?
Follicles containing colloid which is lined by follicular epithelium. C cells (parafollicular cells). Blood vessels
Function of endocrine glands
regulate bodily functions and maintain homeostasis
What epithelium type is the follicular epithelium in the thyroid gland?
Simple cuboidal (when active they come columnar and larger).
Function of C cells (Clear/parafollicular)
Produce calcitonin
Function of calcitonin
regulates Ca levels in the body. Calcitonin is released to reduce the Ca level when it is too high in the blood.
What proportion of the thyroid gland is made up of C cells?
10%
What is colloid?
A fluid containing the prehormone thyroglobulin
Which hormones is thyroglobulin used to synthesis?
Thyroxine T4 and Tri-iodothyronine T£
Which hormone is secreted by the parathyroid gland?
Parathyroid hormone
What is the function the parathyroid hormone?
Calcium regulation. When Ca level is low, parathyroid hormone is released which activates osteoclasts. Rate of bone breakdown increases so Ca level in the blood increases.
In which way are calcitonin and parathyroid hormone antagonistic?
Calcitonin decreases Ca levels in the blood while parathyroid hormone increases Ca levels. Work together to keep Ca concentration within the normal range.
What is the function of osteoclasts?
breakdown/recycle bone to increase minerals in the blood
What is the term given when more parathyroid hormone is produced than needed?
Hyperparathyroidism
What is a consequence of hyperthyroidism?
Bone loss, weakened bone, bone lesions
Possible causes of hyperthyroidism
Benign tumour (more cells = more secretions), chronic kidney disease
What is the effect of oestrogen on osteoclasts?
Oestrogen inhibits osteoclasts therefore in post-menopausal women, osteoclasts are more active leading to an increased risk of osteoporosis
Which 3 substances affect calcium metabolism?
Calcitonin (decrease Ca conc), parathyroid hormone (increase Ca conc), vitamin D
Which cell types are found in the parathyroid gland?
Chief cells, oxyphil cells, adipocytes
Which cell type forms the majority of the parathyroid gland?
Chief cells (granular appearance)
Function of chief cells
synthesise and secrete PTH (granular appearance probably due to organelles)
What are oxyphil cells?
Found in clusters in parathyroid gland. They are a transitional form of chief cells containing numerous mitochondria. Unclear function
What are exocrine glands?
Secretions released by secretory cells into ducts which open up onto an epithelial surface
How can exocrine glands be classified?
By structure or by secretion method
What are the categories for classifying exocrine glands by structure?
Unicellular or multicellular glands (secretory sheet or pockets with ducts)
What is a simple exocrine gland?
A multicellular gland with a single duct - the secretory portion can vary.
What are the different possible simple exocrine glands?
simple - tubular, branched tubular, coiled tubular, acinar, branched acinar.
What is a compound exocrine gland?
A multicellular gland where the main duct branches into multiple secondary ducts. Each secretary portion can be different e.g. compound tubuloacinar.
What are the possible compound exocrine glands?
Compound - tubular, acinar, tubuloacinar (all are branched - otherwise would just be simple branched –)
What does an acinar secretory portion resemble?
Grape
What surrounds branched exocrine glands?
Fibrous tissue capsule
alternative name for glandular tissue
parenchyma
Septa definition
bundles of fibres that extend from the fibrous tissue capsule into the gland to divide it
How is glandular tissue divided?
glandular tissue divided into lobes by interlobar septa. Lobes further divided into lobules by intralobular septa
Which structures do exocrine ducts extend along?
Interlobar and intralobular ducts
Which epithelium lines interlobar ducts?
Stratified columnar epithelium
Which epithelium lines intralobular ducts?
pseudostratified columnar epithelium.
Which epithelium lines striated ducts?
Simple cuboidal/columnar epithelium
Which epithelium lines intercalated ducts?
Simple cuboidal epithelium
Which cells lie between the secretory cells and the basal lamina?
myoepithelial cells
function of myoepithelial cells
contract and squeeze the secretions from the acini along the duct
What are the 3 categories used to classify exocrine glands by secretions?
Merocrine gland
Apocrine gland
Holocrine gland
How are secretions released in a merocrine gland?
Vesicles containing secretory product move towards the gland surface and release product into the duct by exocytosis
How are secretions released in an apocrine gland?
The apical part of the cell containing the secretory product breaks off into the duct
How are secretions released in a holocrine gland?
The entire cell sheds into the duct and dies to release the secretory product.
What are the 3 types of secretions?
Serous, mucous, seromucous (mixed)
What are serous secretions?
Watery secretions containing enzymes
What are mucous secretions?
Mucins are secreted which hydrate to form mucous
What are the 3 major pairs of salivary glands?
Parotid, submandibular, sublingual
What conditions can both major and minor salivary glands be affected by?
Disease, medication side effects - xerostomia, tumours
How do the colour of mucous acini and serous acini differ in H&E staining?
Mucous acini is paler due to mucous.
Why do serous acini have a granular cytoplasm?
Lots of organelles due to high enzyme production
How does the shape and arrangement of the nuclei in mucous acini differ compared to serous acini?
In mucous acini, the nuclei are flattened and peripherally arranged, pressing close to the basal lamina. Serous acini have rounder nuclei.
Example of a gland that is both exocrine and endocrine
pancreas
What is the structure of the exocrine pancreatic gland?
Branched tubuloacinar gland
What are the 4 components the pancreas is divided up into?
Head, neck, body, tail
What is the functional unit of the pancreatic exocrine gland?
Acinus
Does the pancreas contain myoepithelial cells or striated ducts?
no
Examples of enzymes secreted by the exocrine pancreas
proteases and amylases
What portion of the pancreas has an endocrine function?
2% (exo is bulk)
What is the name of the endocrine portion of the pancreas?
islets of Langerhans
Which hormone is produced by Beta cells in the islets of Langerhans?
Insulin
Which hormone is produced by alpha cells in the islets of Langerhans?
Glucagon
Which 2 peptide hormones are produced by delta cells in the islets of Langerhans?
Somatostatin and gastrin
Which cell type in the islets of Langerhans produced pancreatic polypeptide (hormone)?
F cells (PP/gamma)
What are some diseases of the pancreas?
Pancreatic cancer, Cystic Fibrosis, Diabetes mellitus
Which portion of the pancreas can pancreatic cancer affect?
Endocrine or exocrine portion
Which portion of the pancreas does cystic fibrosis affect?
Exocrine - secretions become very thick and stagnate in ducts.
Which portion of the pancreas does diabetes mellitus affect?
Endocrine
What results in type 1 diabetes?
Autoimmune disease that destroys beta cells. The patient is insulin dependent. (5-10% of diabetics)
What results in type 2 diabetes?
Tissues become insulin resistant
What are some oral effects of diabetes
Periodontitis, dry mouth, susceptibility to infections (e.g. thrush/ oral fungal infection)
endocrinopathies definition
disorders of the endocrine system
Hypofunction of endocrine gland definition
reduced hormone release
Hyperfunction of endocrine gland definition
excessive hormone release
Hormone resistance causes
cells resistant e.g. diabetes mellitus 2, hormone action blocked by autoimmune response, hormone receptor blocked
Causes of hypofunction of endocrine gland
smaller gland than normal, tumour/infection/autoimmune process has compromised the gland structure
what are the 3 main endocrinopathies
hypofunction, hyperfunction, hormone resistance
Possible health conditions that may cause endocrine changes
pregnancy, stress, obesity, menopause
