Development of the Rectum
The gut is the primitive digestive tract which develops from invaginted yolk sac, forms the whole of the intestine from the esophagus down to upper part of the anal canal. This gut has 3 parts: the fore gut, mid gut and the hind gut whose fate are esophagus-stomach-duodenum, Small intestine and large intestine respectively .
The rectum develops from the lowest portion of the hind gut which is a blind sac known as the endodermal cloaca which over the lowest boarder of the fetus called cloaca membrane.Tissue around the upper part of the hind gut grow downwards to attach with the cloaca membrane separating the endodermal cloaca into anterior and posterior. Anterior portion becomes urinary bladder and reproductive system except the gonads while the posterior portion becomes the rectum and upper part of anal canal. Cloaca membrane will rapture forming the anal and urogenital opens.
The rectum develops from the lowest portion of the hind gut which is a blind sac known as the endodermal cloaca which over the lowest boarder of the fetus called cloaca membrane.Tissue around the upper part of the hind gut grow downwards to attach with the cloaca membrane separating the endodermal cloaca into anterior and posterior. Anterior portion becomes urinary bladder and reproductive system except the gonads while the posterior portion becomes the rectum and upper part of anal canal. Cloaca membrane will rapture forming the anal and urogenital opens.
Anatomy of the rectum
The rectum is a tubular structure continuous with the sigmoid colon as seen both in fig1.0 and 2.0 with a lenght is ranges between 13-20 cm. It varies according to height, width of hip, body status, and local pelvic anatomy, such as the specific curve of the sacral hollow. Normally lies anterior to the sacral bone/ lower back bone, from the the level of 3rd Sacral down to thee tip of the coccyx bone thus assuming a C-shape curvature of the sacral bone in almost all individuals. It gose downwards piecing the fat in the hip region to continue with the anal canal at the anorectal junction where a sling like muscle, Puborectal muscle pulls it forward to form an angle between it and the beginning of the anal canal. In fig 2.1B, one can see the end of rectum and the beginning of the anal canal from the mucosa surface.
A sheet like tissue called peritoneum covers the whole rectum except surface lying on sacrum and its lowest third which is covered by fat called adipose tissue. Base on this covering, the rectum has been sub divided into 3 parts: Intra peritoneum, Retro peritoneum and infra peritoneum or simply upper, middle and lower third.
A sheet like tissue called peritoneum covers the whole rectum except surface lying on sacrum and its lowest third which is covered by fat called adipose tissue. Base on this covering, the rectum has been sub divided into 3 parts: Intra peritoneum, Retro peritoneum and infra peritoneum or simply upper, middle and lower third.
Functions
The main function of the rectum is to act as a temporary storage site for fecal matter before it is eliminated from the body through the anal canal
Note:The lower third of the rectum is contractile due to extension of the external anal splinter over it, a muscle that controls the anal opening and closing of anal canal.
Note:The lower third of the rectum is contractile due to extension of the external anal splinter over it, a muscle that controls the anal opening and closing of anal canal.