Lecture 5 - Glands 1 Flashcards
What is a gland?
a epithelial cell/cells specialised for secretion of a substance
define Exocrine gland
give examples
Exocrine - Secretion into the external environment, may be via a duct
Salivary gland - saliva
Pancreas - enzymes amylase, lipase, trypsin
Sweat Glands - sweat
define Endocrine gland
give exapmles
Endocrine - Secretion of hormone into the bloodstream for it to bind to a receptor on a distant target cell
Pituitary gland
Thyroid gland - secrets T3 and T4 (controls metabolism)
what are the three modes of secretion?
Merocrine
Apocrine
Holocrine
Define Holocrine
example
Disintegration of the cell, releasing all of the cells contents into the external enviroment
Skin , tarsal glands of eyelid
Define Merocrine
example
Vesicles approaches surface
Vesicles fuse with the plasma membrane, releasing contents extracellulary, via exocytosis
this causes the plasma membrane to grow in size (sometimes the purpose of merocrine secretion)
there are ways to re reduce membrane size ie Apocrine secretion
acinar and endocrine gland of the pancreas
Define Apocrine
example
Secretory product pushes against plasma membrane and pinches off to form a vesicle which is released
this reduces the size of the membrane
membrane can be added by merocrine
lactating mammary gland, sweat glands of axilla (armptis)
what are the 4 ways in which secretion is controlled?
Nervous - input from autonomic fibres
Endocrine control - hormonal - on hypothalamus
Neuro-Endocrine control - between hypothalamus to pituitary. neuron - blood capillary bed (portal system) - target cell
Negative Feedback - Secretory product inhibits its own secretion indirectly or directly
Give a brief summary of how glands develop in utero
1) Growth signals
2) cell proliferation occurs and epithlial cells invade space
3) Exocrine glands - the central cells apoptose to produce a duct, cells differentiates to secret
4) Endocrine glands - cells apoptose to produce a gland, while factors stimulate growth of blood vessels around the cells
how does branching occur?
FGF10 released by mesenchymal stem cells epithelial cells move towards this singal GF1 active - elongation GF2 active - branching Ssh stops growth
what are the shapes of gland ducts, give examples and locations.
there are two parts of glands, the cells that line ducts and the cells in base that secret products
tubular - alveolar
Simple- branched- compound (multiple branched sections joined together)
makes Simple tubular simple alveolar - grape shape simple branched tubular simple branched alveolar compound tubular compound alveolar compound tuboalveolar - salivary glands
the salivary glands have myoepithilial cells , what are they ?
myoepitheilial cells are at the end of ducts, and have epithelial cells and smooth muscle, th emuscle aids in pushing the secretions out of the ducts
the salivalry glands produce mucus, serous or a combination of both.
if both they have a mucus acinus and a serous demilune (think moon on berry) attached. topped by myoeipthelial cells.
describe the example of insulin release
It is a merocrine release of insulin from beta cells in the pancreas
glucose enters the cell via transport proteins
it is metabolised producing ATP
ATP pushes K+ put of cell through ATP K+ channels
Causes a depolarisation of the membrane
allows calcium to enter through a calcium channel
the excess calcium causes the vesicle to move to membrane and fuse with it
insulin then secreted via exocytosis
Define endocytosis
the engulfing of material outside the cell
what is the role of the golgi apparatus in secretion?
1) protein from rough ER are transported in vesicles the the CIS face for the golgi
2) Golgi modifies the proteins
3) Proteins are passed through out of the TRANS face of the gogli, and secreted by merocrine secretion, ie exocytosis
4) can be secreted by unregulated or regulated membrane fusion
