Oophorectomy

Oophorectomy is the surgical removal of the ovaries of a female animal. In the case of non-human animals, this is also called spaying. It is a form of sterilization.

The removal of the ovaries together with the Fallopian tubes is called salpingo-oophorectomy. Oophorectomy and salpingo-oophorectomy are not common forms of birth control in humans; more usual is tubal ligation, in which the Fallopian tubes are blocked but the ovaries remain intact.

In humans, oophorectomy is most usually performed together with a hysterectomy - the removal of the uterus. Its use in a hysterectomy when there are no other health problems is somewhat controversial.

In animals, spaying involves an invasive removal of the ovaries, but rarely has major complications; the superstition that it causes weight gain is not based on fact. Spaying is especially important for certain animals that require the ovum to be released at a certain interval (called estrus or "heat"), such as cats and dogs. If the cell is not released during these animal's heat, it can cause severe medical problems that can be averted by spaying or partnering the animal with a male.

Oophorectomy is sometimes referred to as castration, but that term is most often used to mean the removal of a male animal's testicles.

See also


Rook (chess)

Chess
pieces
King
Queen
Rook
Bishop
Knight
Pawn


A rook may move horizontally or vertically through any number of unoccupied squares.
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A rook may move horizontally or vertically through any number of unoccupied squares.

A rook (borrowed from Persian رخ rokh) is a piece in the strategy board game of chess. Each player starts with two rooks, one in each of the corners nearest their own side. In algebraic notation, white's rooks start on a1 and h1, while black's rooks start on a8 and h8.

The rook moves horizontally or vertically, forward or back, through any number of unoccupied squares, as shown in the diagram at left. Like most pieces, it captures by occupying the square on which an enemy piece stands. The rook also participates, along with the king, in a special move called castling.

Rooks represent siege towers, and get their name from elephant-mounted versions once used in India. They are usually made to look like little castles, and as a result, a rook is sometimes called a "castle". This usage was common in the past ("The Rook, or Castle, is next in power to the Queen" -- Howard Staunton, 1847) but today it is rarely, if ever, used in the literature or among players, except in reference to castling. (Here, "castle" is a verb referring to a move, not a noun referring to a piece.)

In general, rooks are stronger than bishops or knights and are consequently considered about two pawns greater in value. Winning a rook for a bishop or knight is referred to as winning the exchange. Two rooks are generally considered to be worth slightly more than a queen. Rooks and queens are called heavy pieces or major pieces, as opposed to bishops and knights, which are called minor pieces.

In the opening, the rooks are undefended by other pieces, so it is usually desirable to unite one's rooks on the first rank by castling and clearing all pieces except the king and rooks from the first rank. In that position, the rooks protect each other, and can easily move to threaten the most favorable files.

A common goal with a rook is to place it on the first rank of an "open" file, i.e. one unobstructed by pawns of either player, or a "half-open" file, i.e. one unobstructed by friendly pawns. From this position, the rook is relatively unexposed to risk but can control every square on the file. If one file is particularly important, a player may advance one rook on it, and move the other behind, doubling the rooks.

A rook on the seventh rank (the opponent's second rank) is usually very powerful, as it threatens the opponent's unadvanced pawns and hems in the enemy king. Two rooks on the seventh rank are often enough to force victory, or at least a draw by perpetual check. These rooks are sometimes colloquially referred to as "pigs on the seventh", because they often threaten to "eat" the opponent's pieces or pawns.

Rooks are most powerful towards the end of a game, where they can move unobstructed by pawns and control large numbers of squares. They are somewhat clumsy at restraining enemy pawns from advancing towards promotion, unless they can occupy the file behind the advancing pawn. By the same token, a rook best supports a friendly pawn towards promotion from behind it in the same file.

Rooks in heraldry

In heraldry, chess rooks are often used as charges. Unlike a real chess rook, they are conventionally shown with two outward-curving horns. This is because they would otherwise appear to be castle towers, since there is no proportion on a coat of arms. This charge is always blazoned "chess rook" so as not to be confused with the bird of that name; it is also not to be confused with the zule , a similar-looking object with two outward-curving horns at both top and bottom.

In Canadian heraldry, the chess rook is the brisure of the fifth daughter.