Abdomen

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Abdomen

In vertebrate

Vertebrate

Vertebrates are members of the subphylum Vertebrata, chordates with Vertebras or Vertebral columns. The grouping sometimes includes the hagfish, which have no vertebrae, but are genetically quite closely related to lampreys, which do have vertebrae....
s such as mammal

Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s the abdomen (belly) constitutes the part of the body between the thorax

Thorax

The thorax is a division of an animal's body that lies between the head and the abdomen.In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae and the ribs....
(chest) and pelvis

Pelvis

The pelvis or pelvic girdle is the irregular bone structure located at the base of the spine . In the adult human, it is formed by the sacrum and the coccyx, the caudal part of the axial skeleton, and a pair of hip bones, part of the appendicular skeleton or human leg....
. The region enclosed by the abdomen is termed the abdominal cavity

Abdominal cavity

The abdominal cavity is the body cavity of the human body that holds the bulk of the viscus and which is located below the thoracic cavity, and above the pelvic cavity....
. In arthropod

Arthropod

Arthropods are animals belonging to the Scientific classification Arthropoda , and include the insects, arachnids, crustaceans, and others....
s it is the most distal section of the body which lies behind the thorax or cephalothorax

Cephalothorax

The cephalothorax is an Anatomy term used in arachnids and malacostracan crustaceans for the first major body section. The remainder of the body is the abdomen , which may also bear lateral appendages as well as the tail, if present....
.

ertebrates, the abdomen is a large cavity enclosed by the abdominal muscles, ventraly and lateral

Lateral

Lateral may prefer a :*Lateral, an anatomical direction - see Human anatomical terms#Anatomical directions*Lateral pass, type of pass in American and Canadian football...
y, and by the vertebral column

Vertebral column

In human anatomy, the vertebral column is a column of 24 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsum aspect of the torso, separated by spinal discs....
dorsally. Lower ribs can also enclose ventral and lateral walls.

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Encyclopedia

In vertebrate

Vertebrate

Mammal

Thorax

Pelvis

Abdominal cavity

The abdominal cavity is the body cavity of the human body that holds the bulk of the viscus and which is located below the thoracic cavity, and above the pelvic cavity....
. In arthropod

Arthropod

Cephalothorax

Vertebrates

In vertebrates, the abdomen is a large cavity enclosed by the abdominal muscles, ventraly and lateral

Lateral

Vertebral column

Thoracic cavity

The thoracic cavity is the body cavity of the human body that is protected by the thoracic wall ....
by the diaphragm

Diaphragm

Diaphragm may refer to any of the following:Anatomy* Thoracic diaphragm, a tissue of muscle separating the thorax and abdomen of mammals...
. Structures such as the aorta

Aorta

The aorta is the largest artery in the human body, originating from the left ventricle of the heart and bringing oxygenated blood to all parts of the body in the systemic circulation....
, inferior vena cava a esophagus

Esophagus

The esophagus or oesophagus , sometimes known as the gullet, is an Organ in vertebrates which consists of a Muscle tube through which food passes from the pharynx to the stomach....
pass through the diaphragm. Both the abdominal and pelvic cavities are lined by a serous membrane known as the parietal peritoneum. This membrane is continuous with the visceral peritoneum lining the organs. The abdomen in vertebrates contains a number of organs

Organ (anatomy)

In biology, an organ is a biological tissue that performs a specific function or group of functions. Usually there is a main tissue and sporadic tissues....
belonging, for instance, to the digestive tract and urinary system

Urinary system

The urinary system is the organ system that produces, stores, and eliminates urine. In humans it includes two kidneys, two ureters, the urinary bladder, and the urethra....
.

Abdominal organs

Digestive tract: Stomach
Stomach

In most mammals, the stomach is a hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication....
, small intestine
Small intestine

In vertebrates, including mammals, reptiles, birds, and bony fish, the small intestine is the part of the gastrointestinal tract following the stomach, and is where the vast majority of digestion takes place....
, large intestine
Large intestine

The large intestine is the last part of the digestive system?the final stage of the alimentary canal?in vertebrate animals. Its function is to absorb water from the remaining indigestible food matter, and then to pass this useless feces from the body....
with cecum
Cecum

The cecum or caecum is a pouch connected to the ascending colon of the large intestine and the ileum. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine....
and appendix
Accessory organs of the digestive tract: Liver
Liver

The liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, a few of which are detoxification, protein synthesis, and production of biochemicals necessary for digestion....
, gallbladder
Gallbladder

The gallbladder is a small non-vital Organ which aids in the digestive process and concentrates bile produced in the liver....
and pancreas
Pancreas

The pancreas is a gland Organ in the digestive system and endocrine system of vertebrates. It is both an endocrine gland , as well as an exocrine gland, secreting pancreatic juice containing Digestion enzymes that pass to the small intestine....
Urinary system: Kidney
Kidney

The kidneys are Organ that have numerous biological roles. Their primary role is to maintain the homeostasis balance of bodily fluids by filtering and secreting Metabolomics#Metabolitess and minerals from the blood and excreting them, along with water , as urine....
s and ureters
Other organs: Spleen
Spleen

The spleen is an organ found in all vertebrate animals. In humans, the spleen is located in the abdomen of the body, where it functions in the destruction of redundant red blood cells, and holds a reservoir of blood....

Abdominal organs can be highly specialized in some animals. For example the stomach of ruminant

Ruminant

Physiologically, a ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first stomach, known as the rumen, then regurgitating the semi-digested mass, now known as cud, and chewing it again....
s (a suborder of mammals) is divided into four chambers - rumen

Rumen

The rumen, also known as a paunch, forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals....
, reticulum

Reticulum

Reticulum is a small, faint constellation in the southern sky. Its name is Latin for the reticle, an instrument used to measure star positions....
, omasum

Omasum

The omasum, also known as the bible, the fardel, the manyplies and the psalterium, is the third compartment of the stomach in ruminants....
and abomasum

Abomasum

The abomasum, also known as the maw, and the rennet-bag, is the fourth and final stomach compartment in ruminants. The normal anatomical location is along ventral midline....
.

Invertebrates

The invertebrate abdomen is built up of a series of concave upper plates known as tergites and convex lower plates known as sternites, the whole being held together by a tough yet stretchable membrane.

The abdomen contains the insect's digestive tract and reproductive organs, it consists of eleven segments in most orders of insects though the eleventh segment is absent in the adult of most higher orders. The number of these segments does vary from species to species with the number of segments visible reduced to only seven in the common honeybee. In the Collembola (Springtails) the abdomen has only six segments.

The abdomen is sometimes highly modified. In ant

Ant

Ants are Eusociality insects of the family Formicidae, and along with the related wasps and bees, they belong to the order Hymenoptera. Ants evolution from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and Evolutionary radiation after the rise of flowering plants....
s, the first segment of the abdomen is fused to the thorax

Thorax

Propodeum

The propodeum is the first abdomen segment in Apocrita Hymenoptera . It is fused with the thorax to form the mesosoma. It is a single large sclerite, not subdivided, and bears a pair of spiracles....
. The second segment forms the narrow petiole

Petiole (insect)

In entomology, the term petiole is most commonly used to refer to the constricted first metasomal segment of members of the Hymenopteran suborder Apocrita; it may be used to refer to other insects with similar body shapes, where the metasomal base is constricted....
. Some ants have an additional postpetiole segment, and the remaining segments form the bulbous gaster

Gaster

The gaster is the bulbous posterior portion of the metasoma found in Apocrita Hymenoptera . This begins with abdomen segment III on most ants, but some make a postpetiole out of segment III, so the gaster begins with abdominal segment IV....
. The petiole and gaster (abdominal segments 2 and onward) are collectively called the metasoma

Metasoma

The metasoma is the posterior part of the body, or tagma , of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma....
.

Unlike other Arthropods, insects possess no legs on the abdomen in adult form, though the Protura do have rudimentary leg-like appendages on the first three abdominal segments, and Archaeognatha

Archaeognatha

Archaeognatha is an order of wingless insects, also known as jumping bristletails. They are among the least evolutionarily changed insects, appearing in the Devonian period along with the arachnids....
possess small, articulated "styli" which are sometimes considered to be rudimentary appendages. Many larval insects including the Lepidoptera

Lepidoptera

Lepidoptera is an order of insect that includes moths and butterfly. It is one of the most speciose orders in the class Insecta, encompassing moths and the three superfamilies of butterfly, skipper , and Hedylidae....
and the Symphyta (Sawflies) have fleshy appendages called proleg

Proleg

Prolegs are the fleshy, stubby little structures found on the ventral surface of the abdomen of most larvae forms of insects of the Order Lepidoptera, though they can also be found on other larval insects such as symphyta and a few types of Diptera....
s on their abdominal segments (as well as their more familiar thoracic legs), which allow them to grip onto the edges of plant leaves as they walk around.

Abdomen

Vertebrates

Abdominal organs

Invertebrates

See also