Glands Flashcards
Define gland
An epithelial cell or aggregation of cells specialised for secretion
What is an exocrine gland?
One with ducts which secretes onto an epithelial surface
What is an endocrine gland?
A gland without ducts which secretes directly into the blood stream or lymphatic system
Describe merocrine secretion
Occurs by exocytosis
Membrane bound vesicle approaches and fuses with plasma membrane so that contents are released into the extracellular space. Membrane temporarily larger.
Describe apocrine secretion.
Non-membrane bound structure approaches membrane and pushes up apical membrane. Apical cytoplasm drapes droplet which then pinches off surrounding membrane from cell. Membrane temporarily smaller.
Describe holocrine secretion.
Disintegration of whole cell, release of contents, discharge of whole cell.
Describe endocytosis
Engulfing material initially outside cell
Opposite of exocytosis.
Describe trans epithelial transport.
Materials endocytosed at one surface
Transported across cytoplasm using transport vesicles
Materials exocytosed at opposite surface
Explain the mechanism of glycosylation of newly synthesised proteins in the Golgi apparatus.
Glycosylation occurs in the cisternae of the Golgi apparatus
Sugars are added to proteins and lipids
What happens to Golgi products?
Exported in secretory vesicles
Retained for use in the cell e.g. Lysosomes
Added to plasma membrane e.g. Glycocalyx
Why is glycosylation important?
Confers additional specificity
Sugars offer complex shapes for specific interactions in the glycocalyx
What specificity based properties are present in cells?
Adhesion to other cells/substrates
Mobility of cells
Communication with neighbouring cells
Contact inhibition of movement and division
How is secretion controlled?
Negative feedback chemical mechanism e.g. T3/T4 in thyroid
Nervous e.g. Adrenal gland secretion of adrenaline
Endocrine e.g. ACTH affect on adrenal cortex (cortisol)
Neuroendocrine e.g. Nervous stimulation of secretion of ACTH from pituitary
Where are glands derived from?
Epithelial tissues
What is the difference between simple and compound glands?
The ducts of simple glands do not branch where as compound ones do.
