This washing of the feet showed Christ's humility and the priest makes reference to this in the special dismissal appointed for this service.
The matins of Great Thursday is quite short and there are no kathismas appointed. Apart from Psalm 118 (kathisma 17) which is read in its entirety in the service of matins for Great Friday, there are no more kathisma readings until the vespers of Thomas Sunday.
The Liturgy of St. Basil the Great on Great Thursday is combined with Vespers which can be confusing if you're not familiar with the typicon. At the beginning of the Vespers, the priest exclaims 'Blessed is the Kingdom of the Father, and of the Son, and of the Holy Spirit'. This blessing is the one that starts every Liturgy, but today the first part of the Liturgy is actually vespers. We sing the 'Lord I have cried' with the appointed verses and there is an entrance just as there would be a the Liturgy with the deacon or priest holding the Gospel and not the censer.
We then hear the appointed reading from the Old Testament, and after a small litany the choir sings the Trisagion (Holy God, Holy Mighty, Holy Immortal have mercy on us' as in a normal Liturgy. The Liturgy then continues in the familiar way except that the Cherubic Hymn and 'In thee O full of grace' are replaced with special hymns for Great Thursday.
The icon of the Mystical Supper is available from Holy Transfiguration Monastery