Hinterdarm

Hinterdarm, in anatomy and embryology, refers to the posterior portion of the primitive gut tube. In humans it extends from the distal one-third of the transverse colon to the upper anal canal, and includes the distal colon (descending and sigmoid), rectum, and the upper part of the anal canal up to the pectinate line. The hindgut is distinct from the foregut and midgut and forms the latter part of the digestive tract.

During embryonic development, the hindgut originates from endoderm. At around weeks 4–7, the cloaca—a common chamber for digestive, urinary, and reproductive tracts—is divided by the urorectal septum into the anterior urogenital sinus and the posterior anorectal canal. The boundary between hindgut and proctodeum is classically marked by the pectinate line; above this line, the lining of the anal canal is endodermal, derived from the hindgut, while below it is ectodermal in origin.

The hindgut receives arterial blood from the inferior mesenteric artery, and venous drainage flows via the inferior mesenteric vein into the portal system. Innervation involves sympathetic fibers from the inferior mesenteric plexus and parasympathetic fibers from the pelvic splanchnic nerves, which reach the hindgut through the inferior hypogastric plexus.

Functionally, the hindgut regions participate in absorption of water and electrolytes, formation and storage of feces, and coordination of peristaltic movements in the distal colon and rectum. Clinically relevant conditions include Hirschsprung disease, caused by absence of enteric neurons in the distal hindgut, leading to impaired motility and megacolon, and various anorectal malformations affecting development of the anal canal. See also foregut and midgut for comparative context.