In Sir Gawain and the Green Knight, what do the "five wits," "five fingers," and "five joys of Mary" mean in the pentangle on Sir Gawain's shield?

Sir Gawain and the Green Knight is a
late 14th century Middle English alliterative romance recounting an adventure of Gawain,
an Arthurian knight. The anonymous author goes out of his way - taking 46 lines of the
poem - to explicate the symbolism of the pentangle embossed on the knight's shield: "And
why the pentangle is proper to that peerless prince / I intend now to tell, though
detain me it must.'' The poet does this for a reason that supplies the key to
understanding the entire work: The pentangle as a whole and in its
details betokens the truth; the reader is lead throughout the rest
of the poem to ascertain how well or how poorly Gawain cleaves to this standard of
truth. But it is also important to understand that Gawain himself assesses his chivalric
conduct by the standard of the pentangle. He strives to attain perfect virtue or
as shown by the symbol of perfection - the five-pointed, five-fold pentangle. Three
details suffice to illustrate this: He is perpetually vigilant,
that is "faultless in his five senses [wits]"; dexterous, that is
never failing "in his five fingers"; and recollected, that is "all
his force was founded on the five joys [the mysteries of Christ] / That the high Queen
of heaven had in her child.'