The large intestine

The large intestine ( intestinum crassum ) is the last part of the digestive tract that receives a mushy to fluid content from the small intestine - chymus. Water and electrolytes are absorbed from chyme in the large intestine. The contents of the large intestine are formed in the stool. The length of the large intestine is 1.2–1.5 m and the width of the large intestine is approximately 4–7.5 cm

Construction colon wall
It consists of 4 layers (histologické preparáty):


 * Mucosa of the large intestine
 * Screenshot 2021-12-29 at 20.47.55.png mucosa of the large intestine is pale and does not have villi. It is covered by a single layer of cylindrical epithelium. It is permeated by numerous glands and long Lieberkühn crypts . Paneth's cells are missing . The mucosal ligament contains folliculi lymphatici solitarii (mostly in the appendix). Lymphatic tissue accumulates in the appendix. The lamina muscularis mucosae, which contains both longitudinal and circular bundles, is well formed.


 * Submucosal ligament
 * The colonic ligament of the large intestine is sparse. Contains vascular and nerve plexus. Clusters of lymphocytes (nodules) from the mucosa penetrate it.
 * Large intestinal muscle
 * The colonic ligament of the large intestine is sparse. Contains vascular and nerve plexus. Clusters of lymphocytes (nodules) from the mucosa penetrate it.

Colon serosis

 * There is a peritoneal coating on the surface, which is the same as in the small intestine. Creates appendices epiploicae - surface protrusions.

Breakdown
We distinguish the following sections of the large intestine
 * 1) caecum ( intestinum caecum, appendix ) - the widest part, placed in the right pit of the hip and ileocaecal orifice on the left side of the appendix, appendix vermiformis ( worm-like protrusion ) - attached to the blind end of the cecum;
 * 2) colon ( colon ) - the main part of the large intestine which comprises:
 * 3) ascending colon ( colon upward ) - from appendicitis upward on the right side below the liver ;
 * 4) colon transversum (right colon ) - from right to left under the liver and stomach to the spleen ;
 * 5) descending colon ( colon downward ) - the left side of the abdominal cavity from the spleen to the left hypogastrium;
 * 6) colon sigmoideum ( esophageal loop ) - from the end of the colon descendens to the center of the small pelvis;
 * 7) rectum ( rectum ) - the last sections of the intestine in a small pan, opens outwardly opening called the anus ( anus ).  Among the sections of the colon we find typical bends:
 * 8) flexura coli dextra - under the liver (hepatic flexure - flexura hepatica), between the colon ascendens and the transversum;
 * 9) flexura coli sinistra - below the spleen (splenic flexion - flexura lienalis), between the colon transversum and the descendens, higher than the right flexion;  Taeniae coli are 3 whitish longitudinal stripes 8–10 mm wide on the surface of the large intestine, it is a thickening of the longitudinal muscle, according to the position on the transverse colon we distinguish:
 * 10) * taenia mesocolica - at the back, at the point of attachment to the mesocolon transversum;
 * 11) * taenia omentalis - anterior upper, at the junction and fusion of the omentum majus;
 * 12) * taenia libera - front bottom, freely accessible. Haustra coli are externally arched places on the intestine, they are a manifestation of the function of the muscle longitudinal (shrinking) and transverse (throttling). By aggregation we denote the action and the immediate appearance of the intestine. On the large intestine, we also find plicae semilunares ( crescent-shaped algae) and appendices epiploicae, which are protrusions of the serous peritoneal coating of the large intestine, filled with fatty ligament, an unclear function.

Cecum
It forms a sac in the right hip socket, caudally from the ileocaecal orifice (ileum orifice from the left). The length is 6-8 cm, the width is 6-7.5 cm. It rests on the back of the iliacus muscle and the psoas major muscle. The caecum is separated from the fascia muscles by a wall peritoneum, under which the cutaneus femoris lateralis nerve runs


 * recessus rectocaecalis - the area behind the caecum, between the intestine and the peritoneum parietale
 * ostium ileale Bauhini (formerly valva ileacaecalis) = ileum into the appendix lined with algae - labium superius et inferius The junction of the labium superius et inferius in front and behind is called the frenula . The estuary allows flow in only one direction - from the ileum to the caeca. This prevents the contents from refluxing.

Appendix vermiformis
This is a blind caecum. The length of the appendix is ​​5-10 cm. The peritoneal duplication, the mesoappendix, which comes to the appendix from the caudal side of the mesentery of the end of the ileum, serves as a hinge. The appendicular artery passes through the mesoappendix. Ostium appendicis vermiformis is where the appendix opens into the caecum.

McBurney's point


 * Screenshot 2021-12-29 at 20.49.29.png point = projection of a part of the appendix on the surface of the abdomen, lies on the linea bispinalis - at the interface of its right and middle third
 * McBurney's point = the place where the beginning of the appendix is ​​projected lies on the junction of the spina iliaca anterior superior with the navel (linea Monroi), about 6 cm from the spina.


 * Appendix positions
 * Appendix positions relative to the caecum:
 * positio pelvina - appendix medially from the caecum, through the linea terminalis extends into the small pelvis (40% of cases);
 * positio retrocaecalis - appendix behind the caecum, heading free end cranially (33%);
 * positio ileocaecalis - medially from the caecum, parallel to the lower end of the ileum (15%);
 * positio laterocaecalis - appendix outside the caecum, cranially free end (2–16%);
 * positio subcaecalis - appendix from caeca ventrocaudally (2–12%);
 * positio praecaecalis - appendix ventrally from the caecum, free end cranially (5%).
 * According to another classification, we recognize:
 * anterior position - pelvina and ileocaecal position;
 * posterior position - retrocaecal and subcaecal position.

During pregnancy, the appendix is ​​gradually pushed out cranially.

The ligamentum appendiculoovaricum is a non-constant peritoneal fold extending from the appendix (in the pelvic or subcaecal position) to the suspension of the right ovary, over the edge of the small pelvis. It is given importance in the spread of disease processes between the two organs, because algae are the joints of the lymphatic vessels.


 * Appendix wall
 * It resembles the wall of the large intestine. The mucosa and submucosal ligament are permeated with lymphatic tissue. Therefore, the appendix is ​​often referred to as the so-called "tonsilla abdominalis". The muscle forms a continuous mantle of longitudinal bundles. Three taenias emerge at the caecum from the appendix. There is a serosis on the surface that coats the entire appendix.

Colon
It continues from the cecum and wraps around the loops of the small intestine. It passes into a small pelvis in the rectum.

Ascending colon [ modify | edit source ]
Follows the caecum. On the right side of the abdomen, it points cranially below the liver. It is 12–16 cm long, ie. narrower than the caecum. The transition of the colon ascendens into the colon transversum is called flexura coli dextra and lies beneath the liver. Colon ascendens urges: the liver cranially, the right kidney dorsally, the pars descendens duodeni medially and the gallbladder ventromedially. It can be connected to the liver by the hepatocolicum ligament or to the gallbladder by the cystocolicum ligament. It urges the endoabdominal fascia (covering the iliacus muscle, the quadratus lumborum muscle), the aponeurosis of the transverse abdominis muscle and the lower pole of the right kidney. Behind him, the iliohypogastric nerve and thelateral femoral nerve.

Transverse colon [ modify | edit source ]
Colon transversum is about 50-60 cm long. It is caudally curved. Flexura coli sinistra is the transition of colon transversum into colon descendens. Stored under the spleen, higher than flexura coli dextra. It is sharper than the dextra flexure and urges the lower half of the right kidney. It comes into contact with the liver and gallbladder cranially, the stomach and spleen caudally, the loops of the small intestine dorsally, the anterior abdominal wall ventrally, the duodenum and pancreas dorsally and with both kidneys (during flexures). Mesocolon transversumis a curtain, shorter on the right (3 cm), longer on the left (10 cm). Left section of the colon transversum more mobile, attachment to the posterior abdominal wall: center of the anterior kidney area → crosses pars descendens duodeni and caput pancreatis → at the lower edge of the corpus pancreatis → above flexor duodenojejunalis → anterior renal area (here flexura coli sinistra).


 * ligamentum phrenicocolicum - peritoneal, from the left edge of the diaphragm to the flexura coli sinistra, the lower pole of the spleen rests on it (from above)
 * ligamentum gastrocolicum - part of the omentum majus, between the curvatura major of the stomach and the colon transversum - here it joins ventrocranially at the site of taenia omentalis

Descending colon [ modify | edit source ]
Colon descendens is narrower than the colon transversum (approx. 4 cm), it gradually narrows. The length is 22-30 cm. It descends caudally at the left edge of the abdominal cavity to the left hip pit - here it passes into the sigmoid colon. It dorsally associates with symmetrical formations such as the colon ascendens (right). It does not have a mesocolon, fused with the back of the body.

Sigmoid colon [ modify | edit source ]
It comes from the left hip pit in front of the sacrum. At the level of the vertebrae S2 and S3, it passes into the rectum. It has the shape of the letter "N". It passes from the colon descendens caudally → cranially and medially over the edge of the small pelvis. The crosses behind the peritoneum parietale running through the left a. Et. Iliaca communis, a. Spermatica (ovarica) and the left ureter → caudally passes into the rectum. The total length is 30-40 cm. This is the narrowest section of the large intestine 3.7 cm. Mesocolon sigmoideum (mesosigmoideum) is a hinge of an S-shaped loop, running in the shape of the letter "N" like a loop. Recessus intersigmoidus is a deeper, cranially directed depression between the peritoneum parietale and mesosigmoid at the border of the ascending and last descending part of the mesosigmoid attachment.

Rectum
Rectum has two main parts:


 * 1) ampulla recti (rectum in the narrower sense) - cranial part, length 10–12 cm, in the range of flexura sacralis, perineal flexure passes into:
 * 2) canalis analis - length 2.5–3.8 cm, narrower, differs in the longitudinal orientation of the mucous membranes.

The construction of the wall of the rectum [ modify | edit source ]

 * Mucous membrane
 * It has the same color and appearance as the colon . We find typical mucosal algae and other formations on it.
 * In the ampulla recti we find the plicae transversales recti (in the middle of the length of the ampoule), usually three: the upper and lower lashes - rising from the left wall, the Kohlrausch lashing - middle, starting from the right wall.
 * Linea anorectalis - the border of the ampular part of the rectum and anal canal, it crosses the rectum at the tip of the coccyx.
 * In the anal canal we find:
 * columnae anales - longitudinal lashes, 6-10 pieces around the perimeter of the canal;
 * sinus anales - depressions between the lower ends of the columnae anales ;
 * valvulae anales - mucous membranes in the shape of transverse arches, caudally terminating the sinus anales ;
 * zona haemorrhoidalis - a band of mucosa at the level of the columnae et sinus anales, the underlyed plexus venosus rectalis and the sphincter or internus muscle;
 * rectal epithelium in ampoule monolayer cylindrical, ability to absorb (suppositories);
 * numerous Lieberkühn crypts - a number of goblet cells ;
 * glandulae anales - mucous glands at the site of sinus anales, each of six tubules, opening into the anal crypts, secreting mucus;
 * mucosal ligament - contains folliculi lymphatici solitarii ;
 * lamina muscularis mucosae - strong;
 * epithelial change during canalis analis - single-layered cylindrical epithelium → multilayered squamous non-horned ;
 * pecten analis - a lighter band of the mucosa following the valvulae anales, a multilayered squamous epithelium that does not corrode, a submucosal ligament denser and stronger.


 * Submucosal rectal ligament
 * Submucosal connective tissue is high and sparse. The mucosa can move caudally with its weight and with the movement of the contents until it emerges from the anus - the prolapse of the mucosa.


 * Rectal muscle
 * The outer longitudinal layer is continuous and forms the so-called rectal mantle . All three taenie expanded and intensified into the mantle. The circular layer of smooth muscle is reinforced in the upper three quarters of the anal canal, in the range of the zona haemorrhoidalis, valvulae anales , pecten analis . It forms the musculus sphincter or internus , which ends just above the linea anocutanea . The sphincter muscle or externus , which is formed by transversely striated muscle , is attached to the rectal muscle from the dam.


 * The surface layer of the rectum
 * The peritoneum coats the rectum at the transition from the esophageal loop. Sometimes they form a short mesorectum . Next, the rectum sinks under the peritoneum of the small pelvis. The connection of the peritoneum to the wall of the rectum extends most caudally on the front of the rectum - in a woman to the height of the Kohlrausch algae, in a man a little higher. From there, the peritoneum passes to the vesica urinaria in men and to uterus in women.
 * This creates deeper hollows of the peritoneum:
 * excavatio rectovesivalis - in man;
 * excavatio rectouterina - in a woman (deeper);
 * recessus pararectales - slight depressions of the peritoneal wall on the sides of the rectum.
 * From the immersion below the peritoneum, the surface of the rectum is covered with a fibrous adventitia (fascia recti).

Syntopie rekta
Above the level of the diaphragm of the pelvis, the rectum meets:


 * posterior : with vertebrae S 3 –S 5 + coccyx through sparse ligament - is connected with smooth muscle musculus rectococcygeus and ligamentum anococcygeum ;
 * anterior u ♂ : with the posterior wall of the bladder and with the vesiculae seminales via the septum rectovesicale ;
 * anterior u ♀ : with the posterior wall of the vagina through the septum rectovaginale - strengthens the perineal wedge;
 * lateral surfaces of the rectum - turned against the levator ani muscle.

Below and at the level of the diaphargma pelvis, the rectum meets:


 * at the back - with the ligament in front of the coccyx and under the tip of the coccyx, in place of the ligamentum anococcygeum ;
 * in front - with the muscles of the dam, in front of the rectum - between it and the vagina - in a woman's perineal wedge ;
 * on the sides of the sphincter muscle or externus - fat-filled pits - fossa ischiorectalis dextra et sinistra.

Anus - anus [ edit | edit source ]
This is the external end of the anal canalis. The anus is lined with leather. The skin is more pigmented, tightened and folded in the radial algae by the activities of the sphincters. There is no crest in the area of ​​the anus. It is covered by the edges of the buttocks, there are thicker hairs in the immediate vicinity. Glandulae circumanales is an apocrine sweat gland forming a ring around the anus. The rigid fibrous plate that connects the wall of the anal canal to the coccyx in the median plane is called the ligamentum anococcygeum. The mechanism of the anal closure is caused by the sphincters and the pelvic floor muscles.

M. sphincter nor internus - enhanced smooth circular muscle of the anal canal, the ring from the linea anocutanea cranially to the columnae anales.

M. sphincter ani externus - sphincter made of transversely striated muscle, encloses the sphincter ani internus from the outside , attached to the levator ani muscle frombelow, has three parts:


 * Deep part
 * The deep component of the muscle that is stored most cranially. It lies just below the rectal passage through the pelvis diaphragm . The posterior and lateral is in contact with the puborectalis muscle . It is part of the pelvic floor ( levator ani muscle ). The medial muscle fibers are circular, the lateral muscle fibers forming a forward open fork. They are fixed to the hiatus urogenitalis . Together with the puborectalis muscle, it forms the most important component of the rectal closure mechanism - the functional designation of the compressor recti muscle.


 * Superb part
 * It consists mainly of circularly arranged fibers anchored at the front to the center of the tendineum perinei and at the back to the ligamentum anococcygeum . Shrinks the anal canal.


 * Pars subcutanea
 * It has a subcutaneous ring of muscle fibers. It is fixed by strips of ligament and smooth muscle to the skin around the anus, which it shrinks and creases. Its functional component is the corrugator or.

M. puborectalis - part of the pelvic floor muscles, recedes on both sides of the symphysis, walks along the hiatus urogenitalis outside the levator prostatae (puboprostaticus) of a man or pubovaginalis of a woman, surrounds the anal canal at the level of the pars profunda sphincter or externus, creates a musculus compressor recti.

Muscle innervation : pudendus nerve, components from the levator musculus or - directly from the sacral plexus (S 3 –S 4 ).

Arteries and veins
Intestinum crassum is supplied by:


 * Superior mesenteric artery - caecum, ascending colon + trans transverse colon.
 * Screenshot 2021-12-29 at 20.52.29.pngior mesenteric artery - transverse colon, descending colon, sigmoid colon, upper rectum.
 * Arteria iliaca interna - lower part of the rectum.


 * veins of the same name, vena portae + vena cava inferior (anastomosis).


 * Caecum
 * superior mesenteric artery → ileocolic artery → caecal artery
 * appendicular artery
 * ileocolic vein
 * superior mesenteric vein → vena portae


 * Colon
 * Colon ascendens : superior mesenteric artery → dextra colonic artery
 * Transverse colon : inferior + superior mesenteric artery → media and sinus artery
 * Colon descendens : inferior mesenteric artery → sinus colonic artery
 * superior and inferior mesenteric vein → vena portae

Arteria marginalis coli Drummondi connects the final branches of the ileocolic artery, the dextra colonia, the media, the sinusra and the sigmoideae. The association of the a. Colica media with the a. Colica sinistra is referred to as the Halleri anastomosis (also the Riolani arcus ).


 * Rectum
 * a. inferior mesenteric
 * internal pudding artery
 * superior rectal, media and inferior arteries
 * sigmoid artery
 * superior, medial and inferior rectal vein



Lymphatic vessels [ modify | edit source ]

 * from the ileum, cecum, appendix and the beginning of the colon ascendant to: ileocolic lymphoid nodes
 * z colon ascendens do: lymph nodes colici dextri
 * z pravých 2/3 colon transversum do: nodi lymphatici colici medii
 * from the rectum in several directions, to: inferior mesenteric nodes or lymphatic nodi internal iliac
 * from the area of ​​the anal orifice to: superficial inguinal lymph nodes - from them to external iliac lymph nodes

Nerves colon

 * Parasympathetic fibers
 * They come from the vagus nerve (the beginning of the large intestine to the middle and left thirds of the colon transversum - Cannon-Böhme point), the splanchnic pelvic nerves and the inferior mesenteric plexus (below).
 * Sympathetic fibers
 * They come from ganglia celiac, ganglion mesentericum through the superior , ganglion mesentericum Inferius.

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