The cecum ( caecum, ; plural ceca or caeca, ) is a pouch within the

peritoneum The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesotheli ...

that is considered to be the beginning of the

large intestine The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the Digestion, digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces befor ...

. It is typically located on the right side of the body (the same side of the body as the appendix, to which it is joined). The term stems from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

'' caecus'', meaning " blind". It receives

chyme Chyme or chymus (; ) is the semi-fluid mass of partly digested food that is expelled by the stomach, through the pyloric valve, into the duodenum (the beginning of the small intestine). Chyme results from the mechanical and chemical breakdown ...

from the

ileum The ileum () is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may ...

, and connects to the

ascending colon In the anatomy of humans and homologous primates, the ascending colon is the part of the colon located between the cecum and the transverse colon. Characteristics and structure The ascending colon is smaller in calibre than the cecum from wh ...

of the

. It is separated from the ileum by the

ileocecal valve In many Animalia, including humans, an ileocolic structure or problem is something that concerns the region of the gastrointestinal tract from the ileum to the large intestine, colon. In Animalia that have cecum, ceca, the ileocecal region is a sub ...

(ICV), also called Bauhin's valve. It is also separated from the colon by the cecocolic junction. While the cecum is usually intraperitoneal, the ascending colon is

retroperitoneal The retroperitoneal space (retroperitoneum) is the anatomical space (sometimes a potential space) behind (''retro'') the peritoneum. It has no specific delineating anatomical structures. Organs are retroperitoneal if they have peritoneum on thei ...

. In

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

s, the cecum stores food material where bacteria are able to break down the

cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...

. In humans, the cecum is involved in absorption of

salts In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions ( cations) and negatively charged ions (anions), which results in a compound with no net electric charge (electrically neutral). ...

and

electrolytes An electrolyte is a substance that conducts electricity through the movement of ions, but not through the movement of electrons. This includes most soluble salts, acids, and bases, dissolved in a polar solvent like water. Upon dissolving, t ...

and lubricates the solid waste that passes into the large intestine.

Structure

Development

The cecum and appendix are derived from the bud of cecum that forms during week six in the midgut next to the apex of the umbilical herniation. Specifically, the cecum and appendix are formed by the enlargement of the postarterial segment of the midgut loop. The proximal part of the bud grows rapidly to form the cecum. The lateral wall of the cecum grows much more rapidly than the medial wall, with the result that the point of attachment of the appendix comes to lie on the medial side. The cecum's position changes after the midgut rotates and the ascending colon elongates, and the accumulation of meconium inside the cecum may result in the latter's increased diameter.

History

Etymology

The term ''cecum'' comes from Latin ''(intestinum) caecum'', literally 'blind intestine', in the sense 'blind gut' or ' cul de sac'. It is a direct translation from Ancient Greek () (). Thus the inflammation of the cecum is called typhlitis. In

dissection Dissection (from Latin ' "to cut to pieces"; also called anatomization) is the dismembering of the body of a deceased animal or plant to study its anatomical structure. Autopsy is used in pathology and forensic medicine to determine the cause of ...

s by the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

philosophers Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, value, mind, and language. It is a rational and critical inquiry that reflects on ...

, the connection between the

of the

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

and the cecum was not fully understood. Most of the studies of the

digestive tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...

were done on animals and the results were compared to human structures. The junction between the small intestine and the colon, called the

, is so small in some animals that it was not considered to be a connection between the small and large intestines. During a dissection, the colon could be traced from the

rectum The rectum (: rectums or recta) is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. Before expulsion through the anus or cloaca, the rectum stores the feces temporarily. The adult ...

, to the

sigmoid colon The sigmoid colon (or pelvic colon) is the part of the large intestine that is closest to the rectum and anus. It forms a loop that averages about in length. The loop is typically shaped like a Greek letter sigma (ς) or Latin letter S (thus ''s ...

, through the descending, transverse, and ascending sections. The cecum is an end point for the colon with a dead-end portion terminating with the appendix. The connection between the end of the small intestine (ileum) and the start (as viewed from the perspective of food being processed) of the colon (cecum) is now clearly understood, and is called the ileocecal orifice. The connection between the end of the cecum and the beginning of the ascending colon is called the cecocolic orifice.

Clinical significance

A cecal carcinoid tumor is a carcinoid tumor of the cecum. An appendiceal carcinoid tumor (a carcinoid tumor of the appendix) is sometimes found next to a cecal carcinoid. Neutropenic enterocolitis (typhlitis) is the condition of inflammation of the cecum, primarily caused by bacterial infections. Over 99% of the bacteria in the gut are

anaerobe An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenat ...

s,University of Glasgow. 2005.
The normal gut flora.
Available through web archive. Accessed May 22, 2008 but in the cecum, aerobic bacteria reach high densities.

Other animals

A cecum is present in most

amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...

species, and also in

lungfish Lungfish are freshwater vertebrates belonging to the class Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, inc ...

, but not in any living species of

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

. In

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s, it is usually a single median structure, arising from the dorsal side of the large intestine.

Bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s typically have two paired ceca, as do, unlike other mammals, hyraxes. Parrots do not have ceca. Most mammalian

s have a relatively large cecum. In many species, it is considerably wider than the colon. For some herbivores such as lagomorphs (rabbits, hares, pikas), easily digestible food is processed in the gastrointestinal tract and expelled as regular feces. But in order to get nutrients out of hard to digest fiber, lagomorphs ferment fiber in the cecum and then expel the contents as

cecotrope Cecotropes (also caecotropes, cecotrophs, caecotrophs, cecal pellets, soft feces, or night feces) are a nutrient-filled package created in the gastrointestinal (GI) tract that is expelled and eaten by many animals (such as rabbits, guinea pigs, ...

s, which are reingested (cecotrophy). The cecotropes are then absorbed in the small intestine to utilize the nutrients. In contrast, obligate

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they ar ...

s, whose diets contain little or no plant matter, have a reduced cecum, which is often partially or wholly replaced by the appendix. Mammalian species which do not develop a cecum include

raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from Procyonina, other species of raccoon, is a mammal native to North America. It is the largest ...

bear Bears are carnivoran mammals of the family (biology), family Ursidae (). They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats ...

s, and the

red panda The red panda (''Ailurus fulgens''), also known as the lesser panda, is a small mammal native to the eastern Himalayas and southwestern China. It has dense reddish-brown fur with a black belly and legs, white-lined ears, a mostly white muzz ...

. Many fish have a number of small outpockets, called ''pyloric ceca'', along their intestine; despite the name, they are not homologous with the cecum of amniotes – their purpose is to increase the overall area of the digestive epithelium. Some invertebrates, such as squid, may also have structures with the same name, but these have no relationship with those of vertebrates.

Gallery

File:Blausen 0604 LargeIntestine2.png, Illustration of the large intestine File:Cecum and ileum.JPG, Cecum and ileum File:Ileo-cecal valve.JPG, Ileo-cecal valve File:Cecum and ileocecal valve.JPG, Cecum File:Gray536.png, Arteries of cecum and vermiform process File:Gray1044.png, Inferior ileocecal fossa File:Ileocecal valve.jpg,

Endoscopic An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are insert ...

image of cecum with arrow pointing to

in foreground

References

External links

* —"Abdominal organs in situ." * —"The larger intestine." * —"The cecum with the distal portion of the ileum." * —"Incisions of the Cecum" *
Photo at mgccc.cc.ms.us

Video clip of worms in the Cecum
() {{Authority control Digestive system Latin words and phrases