Henry Gray (18251861). Anatomy of the Human Body. 1918.
empty condition it presents the appearance of an antero-posterior longitudinal slit. Behind it is a mass of muscular and fibrous tissue, the anococcygeal body (Symington); in front of it, in the male, but separated by connective tissue from it, are the membranous portion and bulb of the urethra, and the fascia of the urogenital diaphragm; and in the female it is separated from the lower end of the vagina by a mass of muscular and fibrous tissue, named the perineal body.
FIG. 1081 Inner wall of the lower end of the rectum and anus. On the right the mucous membrane has been removed to show the dilatation of the veins and how they pass through the muscular wall to anastomose with the external hemorrhoidal plexus. (Luschka.) (See enlarged image)
The lumen of the anal canal presents, in its upper half, a number of vertical folds, produced by an infolding of the mucous membrane and some of the muscular tissue. They are known as the rectal columns [Morgagni] (Fig. 1078), and are separated from one another by furrows (rectal sinuses), which end below in small valve-like folds, termed anal valves, which join together the lower ends of the rectal columns.
FIG. 1082 Section of mucous membrane of human rectum. (Sobotta.) X 60. (See enlarged image)
Structure of the Colon.The large intestine has four coats: serous, muscular, areolar, and mucous.