Gland Structure and Function Flashcards
Define gland.
An epithelial cell or an aggregate (usually and aggregate) of epithelial cells that are specialised for the secretion of a substance.
What are the main differences between endocrine glands and exocrine?
Endocrine are ductless and secrete its product into the blood system to let the secreting function at a distant part of the body. (hormones) ALL EPITHELIAL CELLS SECRETE THE HORMONES IN THE GLAND.
Exocrine are ducted and secrete its product into a duct, they are more generally more local and its product is generally enzymes or lubricants. ONLY THE CELLS AT THE APEX OF THE DUCT SECRETE THE PRODUCT.
What are some examples of endocrine glands and what are their hormones?
Anterior pituitary gland (ACTH, LH, FSH and TSH)
Posterior pituitary gland (ADH and oxytocin)
Thyroid gland (T3, T4 and calcitonin)
Parathyroid gland (PTH)
What are some examples of exocrine glands and what are their products?
Salivary glands (amylase e.g.) Pancreas (amylase, trypsin, lipase) (also endocrine) Sweat glands (sweat) Sebaceous gland (secrete sebum (oil))
Give the steps of the generation of a gland.
- Growth signal received
- Proliferation of cells.
- Epithelial cells invade the space created
- In exocrine glands the central cells die off to produce a duct
- in endocrine glands angiogenic factors produce blood vessels around the epithelial cells.
What are the two main shapes of gland ducts?
Simple duct structure and compound duct structure.
What are the subtypes of simple duct structure? Give examples of each.
Simple tubular (intestinal glands)
Simple branched tubular (gastric glands)
Simple alveolar (none important in humans)
Simple branched alveolar (sebaceous glands)
What are the subtypes of compound duct structure?
Compound tubular (duodenal glands and small intestinal) Compound alveolar (mammary glands) Compound tubuloalveolar (salivary glands)
What are myoepithelial cells?
Cells that have features of both an epithelial cell and a smooth muscle cell. This means they help ejecting secretions from the duct.
What are the different mode of secretions?
Merocrine
Apocrine
Holocrine
Cytocrine
Explain merocrine and give an example.
Fusion of vesicles with the apical membrane and the product is then released. It is a form of exocytosis. An example is insulin release of endocrine glands of the pancreas.
Explain apocrine and give an example.
A part of the gland is ‘pinched’ off. A partial loss of cytoplasm.
E.g. mammary glands and sweat glands.
Explain holocrine and give an example.
Complete loss of cytoplasm or cell.
E.g. sebaceous gland in skin and tarsal glands in eyelid.
Explain cytocrine and give an example.
The entire cell is released as a secretion.
E.g. spermatid.
What is the main difference between regulated secretion and constitutive secretion?
Regulated happens due to a trigger like calcium ions.
Constitutive happens all the time without any trigger.
Give an example of regulated secretion.
Eating a breakfast leading to insulin secretion.
Glucose is broken down to ATP
ATP closes K+ channels means K+ can’t leave. Membrane depolarisation occurs and calcium channels open so Ca2+ enters cell.
Ca2+ helps with the regulated secretion and insulin is released.
Outline the steps of holocrine secretion.
- Secretory cell fills up with secretory granules
- Cell organelles degenerate
- Cell dies
- Plasma membrane breaks and the contents empty
- Dead cells are replaced by mitotic division of basal cells.
What is the main function of the Golgi in secretion?
Glycosylation of proteins
What is glycosylation of proteins?
The covalent attachment of sugars by enzymes to proteins and lipids to form glycoproteins and glycolipids.
Why is glycosylation important?
It aids protein folding Prevents protein digestion intracellularly Prevents lipid digestion intracellularly Cell recognition Role on cell to ECM attachment
What is phagocytosis?
Where cells (phagocytes) engulf other cells or particles Mainly used by the immune system.
What is pinocytosis?
Where cells ingest liquid droplets. (used by all cells)
What is transcytosis?
When a particle move from lumen to interstitium via or between epithelia.
What are the 4 examples of transcytosis?
- Through aqueous channels in the intercellular junction
- Lipid cell membranes (diffusion across)
- Transport via carrier proteins
- Endocytosis and then exocytosis
What are the 3 controls of gland secretion and what are they primarily regulated by?
Hormonal, Neural and Humoral.
Controlled by negative feedback
How does hormonal control of gland secretion work?
Hypothalamus secrete hormone that tells anterior pituitary gland to secrete a hormone. The hormone secreted the anterior pituitary then tells a peripheral endocrine gland to secrete its hormone. This hormone then arrives to its target cell and an action is performed.
How does neural control of gland secretion work?
Nervous system tells an endocrine gland to release a hormone. Hormone arrives to target cell and an action is performed.
How does humoral control of gland secretion work?
A changed level of a substance in the plasma activates an endocrine gland. Endocrine gland secretes hormone and it targets a cell. Cell produces a response.
