Rectum

The rectum is the final division of the digestive tube. It is a continuation of the colon, but for its anatomical and physiological characteristics significantly different from it.
The length of the entire rectum is 13-15 cm, of which perineal Department and the anal canal (the final division of the colon, which opens on skin by hole anus - anus) accounts for up to 3 cm, on podbroshennye Department - 7-8 cm, and intraperitoneal part - 3-4 see
Rectum consists of mucous membrane, submucosal layer and muscle membrane. Outside it is covered quite a powerful fascia, which is separated from the muscle membrane thin layer of fatty tissue. This fascia surrounds not only the rectum, but men also and the prostate gland with seed bubbles, and in women, the cervix.
Mucous rectal covered cylindrical epithelium with a large number bokalovidnykh cells. It contains in addition a lot of so-called Oberkovych glands, consisting almost entirely of mucous cells. That is why in pathological processes from the rectum stands out copious amounts of mucus.
2 cm above the anus mucous membrane forms a series of vertically parallel elevations. This so-called columns winking. Their number varies (from 6 to 14), they have the form of longitudinal ridges rising above the level of the mucous 2-4 mm Bars Morgagni is formed by a fold of mucous membrane. Between each two columns obtained deepening in the form of a groove that ends in a blind pocket (the crypt). Pockets play a big role in international practice. Often linger foreign bodies or particles of feces, which may cause inflammation and lead to the development of paraproctitis.
A disorder of the intestines, diarrhea, constipation), various inflammatory processes (the proctitis, colitis), contributing to long-term irritation of mucous membrane, cause grounds crypts of papillae, which sometimes greatly increased. Hypertrophic papillae mistaken for polyps, while they represent only a simple elevation normal mucosa.
The blood supply of the rectum is top, middle and bottom of hemorrhoidal arteries. Of them the first artery unpaired, and the other two pairs, suited to the intestine from the sides. Veins of the rectum come with the arteries. The outflow of venous blood is carried out in two ways - through the system of portal vein and the Vena cava. In the wall of the lower part of the intestine are thick venous plexus - submucosal and related subfascial and subcutaneous located in the area of the sphincter and the anal canal.
Before proceeding to the physiology of the rectum, stop briefly on the mechanism of formation of feces. It is known that a person per day from thin intestines in thick goes on average about 4 litres of edible pulp (chyme). In the colon (in the right Department in the blind and ascending colon), due to the tonic contractions, and peristaltic antiperistaltic movements thickening, mixing intestinal contents and the formation of feces. 4 l chyme in the colon only 140-200 g formed Kala, which usually consists of residues digestible food (fiber tissue, muscle and tendon fibers, grain, covered with fiber, etc.), waste products ulcer (mucus, luxuries mucosal cells, cholesterol, cholic acid and other), as well as of the living and the dead bacteria.
The left half of the colon does evaquatornuu, aided by the so-called big and small movement. Small movements continuously occur small reduction, mixing the contents of the intestine, large - intensive rapid reduction of whole departments helps promote intestinal contents. They occur 3-4 times a day.
Food from the stomach was evacuated after an average of 2 to 2.5 hours After 6 h of liquid intestinal contents, having 5-6 m of the small intestine, moved into the large intestine where it goes 12-18 hours As already mentioned, for a day from the small intestine into the large moves approximately 4 liters semi chyme. More than 3,7 litres during this time absorbed just in the colon. Together with the liquid entry occurs in the blood of toxic substances - products of decomposition of food and intestinal fermentation.
Venous blood with these products, flowing through the system of portal vein to the liver, where they delay, neutralization and discarding with jelchew. Thus, the colon still belongs and absorption feature.
Bowel movements - defecation - is the result of a complex interaction of a number of physiological mechanisms. Peristaltic movements fecal gradually moving in the sigmoid colon. The accumulation and retention of feces is mainly due to reductions circular muscle layer of the colon.
When lowering of feces in the ampulla of the rectum are set in motion new mechanisms - reflex tonic contraction striated muscles of the external sphincter anus. The defecation is composed of the following stages: filling ampoules feces, evacuation peristalsis of the rectum and Sigma in reflex relaxation of the sphincter, the simultaneous operation of the auxiliary muscle groups (abdominals and others). Anus after defecation remains for a long time empty.
It should be noted that different intensity action by the subsidiary muscle group aims to accelerate and strengthen the evacuation of stool, especially in cases of hard its consistency or any pathological conditions (constipation, atony, cramps).
The anus and rectum have a wealth of receptive field here during stimulation impulses transmitted to the stomach and influence on his work, salivation, and bile secretion.
Bowel movements is due to the influence not only of unconditional (tensile ampoules), but also with the action of conditional stimuli that create the rhythm stool at certain times of the day. For defecation affects the cerebral cortex, which is confirmed by the following fact: a sudden mental or physical irritation can be completely removed already familiar time-chair, and for a long time to delay gastric emptying.
As you can see, the basic physiological function of the rectum - defecation - is a complex process involving a variety of mechanisms. Any violation of them leads to the breakdown of the specified function.

Anus (rectum) is the final section of the intestines.

Anatomy
Rectum starts at level II-III sacral vertebrae and falls ahead of the sacrum, with S-shaped with the expansion in the middle part (printing. Fig. 1). The upper curve of the rectum and sacral (flexura sacralis) - corresponds to the concavity of the sacrum, the lower - perineal (flexura perinealis)backwards. Accordingly, the bends on the inside of the intestine are formed transverse folds plicae transversales recti) - two more to the left, one on the right.
In the middle part of the rectum widened, forming the ampoule (ampulla recti). The final division of the rectum - anal canal (canalis analis)is sent back and down and ends anal hole (anus). The length of the colon 13-16 cm, of which 10-13 cm occur in the pelvic Department, and 2.5 - 3 cm - perineal. The circle ampullar cancer equal 8-16 cm (overflow, or atony - 30 - 40 cm).
Clinicians there are 5 departments of the rectum: adampulawy (or recto-sigmoid), verkhneangarsky, sredneimportnye, nizhneamudarya and perineal.
Rectal wall consists of 3 layers: the slimy, submucosal and muscle. The upper part of the rectum covered front and sides of the serous membrane, which in the upper part of the intestine surrounds her and back, passing in short mesentery (mesorectum). The mucous membrane has a large number of longitudinal easily deal folds.

rectum anatomy
Vessels and nerves of the rectum.
Fig. 1. Blood and lymphatic vessels of the rectum (front-cut male pelvis; the belly is partially removed, the mucous membrane of the rectum is in the lower part of it is removed).
Fig. 2. Blood vessels and nerves of the rectum (sagittal cut male pelvis).
1 - nodi lymphatici mesenterici inf.; 2 - a. et v. rectales sup.; 3 - colon sigraoldeum; 4 - plexus venosus rectalis; 5 - a. et v. rectales raedil sin.; 6 - plica transversa; 7 - nodus lymphaticus iliacus int.; 8 - ra. levator ani; 9 - tunica muscularis (stratum circulare); 10 - muscle bundles in the field columnae anales; 11 - m. sphincter ani ext.; 12 - m. sphincter ani int.; 13 - anus; 14 - a. et v. rectales inf.; 15 - zona haemorrhoidalis (venous plexus); 16 - a. et v. rectales medii dext.; 17 - tunica mucosa recti; 18 - rectum; 19 - a. iliaca int.; 20 - v. iliaca int.; 21 - nodus lymphaticus sacralis; 22 - a. sacralis med.; 23 - plexus rectalis sup.; 24 - plexus sacralis; 25 - plexus rectalis med.; 26 - columnae anales; 27 - prostata; 28 - vesica urinaria; 29 - plexus hypogastricus int.; 30 - mesorectum.
rectum structure

In the anal canal has 8-10 constant longitudinal folds - columns (columnae anales) with grooves between them - anal sinuses (sinus anales)that end, another folds - butterfly (valvulae anales). Slightly acting zigzag line of anal flap is called rectal, gear, or Grebeshkova, and is the border between glandular epithelium ampoules and flat epithelium, anus rectum. The annular space between anal sinuses and anal hole is called the hemorrhoid area (zona hemorrhoidalis).
Submucosal layer consists of loose connective tissue that facilitates easy offset and stretch a mucous membrane. Muscular wall has two layers: the inner circular and outer longitudinal. First thickens in the upper part of the perineal Department of 5-6 mm, forming an internal sphincter (m. sphincter ani int.). In the field of perineal part of the intestine longitudinal muscle fibers are woven with the fibers of the muscles that raise the anus (m. levator ani), and partly with outer pulp. The outer pulp (m. sphincter ani ext.) unlike internal consists of arbitrary muscles covering the perineal Department and closing the rectum. It has a height of about 2 cm and a thickness up to 8 mm
The pelvic floor is formed by the muscles that raise the anus, and the PC muscle (m. coccygeus), as well as covering their fascia. Pair muscles, raising your anus, is composed mainly of iliac PC (m. iliococcygeus), pubic PC (m. pubococcygeus) and pubic-pryamokishechnye (m. puborectalis) of the muscles and form a kind of funnel, descended to the pelvis. The edges of her attached to the top departments of internal wall of the pelvis, and down in the center a funnel like studded with rectum associated with the fibers of the muscles that raise the anus. The latter shared the cavity and small pelvis into two sections: the upper-internal (pelvic-pryamokishechnye) and bottom-outer (sciatic-pryamokishechnye). Upper inner surface of the muscle, raising the anus, covered fascia pelvic diaphragm (fascia diaphragmatis pelvis sup.), which connects to own the fascia of the rectum.
The peritoneal cover applies only to the top-peretii Department of the rectum, descending from the front to the red space and lifting from the sides to the level III sacral vertebra, where both serous piece together in the initial part of the mesentery.
To the edges of that stretched down oval abdominal cover attached own fascia rectum, more dense back and relatively less pronounced from the sides and front overhang in dense prostate-abdominal aponeurosis (men) or premonicion-vaginal aponeurosis (women). This aponeurosis easily divided into two plates, one of which puts the prostate, seed bubbles, and the other front wall of the rectum; it facilitates the separation of the two bodies during surgery. Univerzalne destruction of the rectum, together with the discharge of the lymphatic vessels without compromising their integrity is the most important condition for radical surgery.
The blood supply of the rectum (printing. table, Fig. 1 and 2) through unpaired top pryamokishechnye (a. rectalis sup.) and after two pair - middle and lower - pryamokishechnye artery (AA. rectales med. et inf.). Top pryamokishechnye artery is the final and most important branch of the inferior mesenteric artery. Good vascular network sigmoid colon enables you to maintain good blood circulation under condition of leaving intact the regional vessel even after high crossing the upper pryamokishechnye and one of the three lower sigmoid arteries. Security of intersection of the artery above the critical point of sudaca" can only be achieved while maintaining the territorial integrity of the vessel. The blood supply of the entire rectum before anal parts is carried out mainly at the expense of the top pryamokishechnye artery, which is divided into two, and sometimes more branches at level III-IV sacral vertebrae.
Average pryamokishechnye artery coming from the branches of the internal iliac artery, not always equally developed and often non-existent. However, in some cases, they play an important role in the circulation of the rectum.
Lower pryamokishechnye artery coming from the internal private parts of the arteries that feed mainly outer sphincter and skin anal area. There are good communications between branches of the systems of the upper, middle and lower pryamokishechnye arteries, and crossing the upper pryamokishechnye artery at different levels while maintaining the integrity of the middle and lower pryamokishechnye arteries and their numerous nameless twigs in front and lateral parts of the rectum does not deprive the power lower part of the colon.
Venous plexus rectum (plexus venosi rectales) are located in different layers of the intestinal wall; distinguish the submucosa, the subfascial and subcutaneous plexus. Submucosal or internal plexus is located in a ring of the extended venous trunks and cavities in the submucosa of the. It is connected with the subfascial and subcutaneous entanglements. Venous blood flowing into the system of portal vein through the top pryamokishechnye Vienna (v. rectalis sup.) and in the system of the inferior Vena cava through the middle and lower pryamokishechnye Vienna (vv. rectales med. et inf.). Between these systems much anastomoses. The absence of valves at the top pryamokishechnye Vienna, as in the entire portal system, plays an important role in the development of venous congestion and dilatation of the distal segment of the rectum.

The lymphatic system. The lymphatic vessels of the rectum are important, because they can spread of tumors and infection.
In the mucous membrane of the rectum is single-layered network of lymphatic capillaries connected to such a network submucosal layer, which also formed plexus lymphatic vessels of the first, second and third orders. In the muscle membrane of the rectum develop a network of lymphatic capillaries, compiled by capillaries circular and longitudinal layer of the rectum. In serous membrane of the rectum are superficial (macapella) and deep (syrokomlia) network of lymphatic capillaries and lymph vessels.
Discharge lymphatic vessels mostly follow in the course of the blood vessels. There are three groups extramurally lymphatic vessels: the upper, middle and lower. Top lymphatic vessels, collecting lymph from the walls of the rectum, go along the branches of the upper pryamokishechnye artery and fall into the so-called lymph nodes Gerety. Average pryamokishechnye lymphatic vessels coming from the side walls of the colon under the fascia covering the muscle that raises the anus, in the direction of lymph nodes located on the wall of the pelvis. Lower pryamokishechnye lymphatic vessels originate in the skin of the anus and are associated with the lymphatic vessels of the mucous membrane of the anal canal and capsules. They go in the thickness of the subcutaneous fat of the inguinal lymph nodes.
Lymph outflow, and consequently, the migration of tumor cells can go in many directions (see below).
Innervation recto-sigmoid and anularea parts of the rectum is mainly sympathetic and parasympathetic systems, perineal - mainly branches of spinal nerves (printing. Fig. 2). This explains the relatively low sensitivity of the rectal ampulla to pain and high sensitivity to pain of anal canal. The internal sphincter innerviruetsya sympathetic fibres outer branches of the private parts of the nerves (nn. pudendi), accompanying the bottom pryamokishechnye artery. The muscle lifting the anus, innerviruetsya branches, coming mainly from III and IV of the sacral nerves, and sometimes from the rectum. This is important when resection of the lower sacral vertebrae to access the rectum, as it indicates the necessity of crossing the sacrum lower third of the sacral holes to prevent serious violations of the functions of not only the muscles that raise the back passage and external sphincter, but other pelvic organs.