7 In the human nature united to Himself the Son of God, by overcoming death through His own death and resurrection, redeemed man and re-molded him into a new creation. By communicating His Spirit, Christ made His brothers, called together from all nations, mystically the components of His own Body. In that Body the life of Christ is poured into the believers who, through the sacraments, are united in a hidden and real way to Christ who suffered and was glorified. Through Baptism we are formed in the likeness of Christ: "For in one Spirit we were all baptized into one body". In this sacred rite a oneness with Christ's death and resurrection is both symbolized and brought about: "For we were buried with Him by means of Baptism into death"; and if "we have been united with Him in the likeness of His death, we shall be so in the likeness of His resurrection also". Really partaking of the body of the Lord in the breaking of the Eucharistic bread, we are taken up into communion with Him and with one another. "Because the bread is one, we though many, are one body, all of us who partake of the one bread". In this way all of us are made members of His Body, "but severally members one of another". As all the members of the human body, though they are many, form one body, so also are the faithful in Christ. Also, in the building up of Christ's Body various members and functions have their part to play. There is only one Spirit who, according to His own richness and the needs of the ministries, gives His different gifts for the welfare of the Church. What has a special place among these gifts is the grace of the apostles to whose authority the Spirit Himself subjected even those who were endowed with charisms. Giving the body unity through Himself and through His power and inner joining of the members, this same Spirit produces and urges love among the believers. From all this it follows that if one member endures anything, all the members co-endure it, and if one member is honored, all the members together rejoice. The Head of this Body is Christ. He is the image of the invisible God and in Him all things came into being. He is before all creatures and in Him all things hold together. He is the head of the Body which is the Church. He is the beginning, the firstborn from the dead, that in all things He might have the first place. By the greatness of His power He rules the things in heaven and the things on earth, and with His all-surpassing perfection and way of acting He fills the whole body with the riches of His glory. All the members ought to be molded in the likeness of Him, until Christ be formed in them. For this reason we, who have been made to conform with Him, who have died with Him and risen with Him, are taken up into the mysteries of His life, until we will reign together with Him. On earth, still as pilgrims in a strange land, tracing in trial and in oppression the paths He trod, we are made one with His sufferings like the body is one with the Head, suffering with Him, that with Him we may be glorified. From Him "the whole body, supplied and built up by joints and ligaments, attains a growth that is of God". He continually distributes in His body, that is, in the Church, gifts of ministries in which, by His own power, we serve each other unto salvation so that, carrying out the truth in love, we might through all things grow unto Him who is our Head. In order that we might be unceasingly renewed in Him, He has shared with us His Spirit who, existing as one and the same being in the Head and in the members, gives life to, unifies and moves through the whole body. This He does in such a way that His work could be compared by the holy Fathers with the function which the principle of life, that is, the soul, fulfills in the human body. Christ loves the Church as His bride, having become the model of a man loving his wife as his body; the Church, indeed, is subject to its Head. "Because in Him dwells all the fullness of the Godhead bodily", He fills the Church, which is His body and His fullness, with His divine gifts so that it may expand and reach all the fullness of God.
Source: Lumen Gentium (Vatican.va)