The abdomen (commonly called the belly) is the body space between the thorax (chest) and pelvis. The diaphragm forms the upper surface of the abdomen. At the level of the pelvic bones, the abdomen ends and the pelvis begins.

The abdomen contains all the digestive organs, including the stomach, small and large intestines, pancreas, liver, and gallbladder. These organs are held together loosely by connecting tissues (mesentery) that allow them to expand and to slide against each other. The abdomen also contains the kidneys and spleen.


  • A dermatome is the area of the skin of the human anatomy that is mainly supplied by branches of a single spinal sensory nerve root. These spinal sensory nerves enter the nerve root at the spinal cord, and their branches reach to the periphery of the body.

Sensory Distribution

  • Series of transverse bands
  • Important to help localize the origin of pain coming from an internal organ

External Oblique

  • The external oblique muscles are located on the outer surface of the sides of the abdomen, on each side of the rectus abdominis. The muscles extend from the lower ribs to the pelvis. The external oblique muscles are responsible for the twisting of the trunk.

Rectus Abdominis

  • The rectus abdominis muscle, also known as the “abdominal muscle” or “abs”, is a paired muscle running vertically on each side of the anterior wall of the human abdomen, as well as that of some other mammals.

Internal Oblique

  • This muscle originates at the lumbar fascia (a connective tissue that covers the lower back), the outer portion of the inguinal ligament (a ligament located on the bottom-outer edge of the pelvis), and back of the iliac crest (the upper-outside portion of the pelvis). The internal abdominal oblique muscle ends at the bottom edge of the rib cage, the rectus sheath (fibrous tissue that covers the abdominal muscles), and the pubic crest (an area in the lower-front of the pelvis).

Transversus Abdominis

  • The transversus abdominis muscle is the deepest of the abdominal muscles, lying internally to the internal abdominal obliques. It is a thin sheet of muscle whose fibres run horizontally anteriorly.

Rectus Sheath

  • The rectus sheath, also called the rectus fascia, is formed by the aponeuroses of the transverse abdominal and the external and internal oblique muscles. It contains the rectus abdominis and pyramidalis muscles. It can be divided into anterior and posterior laminae.

Rectus Sheath I

  • Aponeurosis of three anterolateral muscles form rectus sheath
  • Fibrous compartment containing rectus abdominis, epigastric arteries and dorsal tips of thoracoabdominal nerves
  • It is incomplete- different arrangement above and below the umbilicus

Anterolateral Abdominal Wall

  • There are two vertical muscles located in the midline of the anterolateral abdominal wall – the rectus abdominis and pyramidalis. The rectus abdominis is long, paired muscle, found either side of the midline in the abdominal wall.

Superior Epigastric

  • In human anatomy, superior epigastric artery refers to a blood vessel that carries oxygenated blood and arises from the internal thoracic artery
  • Direct continuation of internal thoracic artery from chest wall.

Inferior Epigastric

  • inferior epigastric artery refers to the artery that arises from the external iliac artery and anastomoses with the superior epigastric artery. Along its course, it is accompanied by a similarly named vein, the inferior epigastric vein.
  • Branch from the external iliac artery

Thoracoabdominal Nerves

  • Major nerves to the anterolateral abdominal wall include the thoracoabdominal, lateral cutaneous, subcostal nerve, iliohypogastric, and ilioinguinal nerves. The thoracoabdominal nerves are derived from T7-T11 and form the inferior intercostal nerves.

Subcostal Nerves

  • The anterior division of the twelfth thoracic nerve (subcostal nerve) is larger than the others; it runs along the lower border of the twelfth rib, often gives a communicating branch to the first lumbar nerve, and passes under the lateral lumbocostal arch.

Iliohypogastric Nerve

  • The iliohypogastric nerve is a nerve that originates from the lumbar plexus that supplies sensation to skin over the lateral gluteal region and motor to the internal oblique and transverse abdominal muscles.

Ilioinguinal Nerve

  • The ilioinguinal nerve is a branch of the anterior rami of the L1 spinal nerve that originates in the lumbar plexus. Additionally, the iliohypogastric nerve is a branch of L1 that travels with the ilioinguinal nerve for a distance before branching off to a different destination and innervation.

Inguinal Canal

  • The inguinal canals are the two passages in the anterior abdominal wall which in males convey the spermatic cords and in females the round ligament of the uterus. The inguinal canals are larger and more prominent in males.
  • It has four regions: anterior wall, posterior wall, roof and floor.


  • A hernia occurs when an organ or fatty tissue squeezes through a weak spot in a surrounding muscle or connective tissue called fascia. The most common types of hernia are inguinal (inner groin), incisional (resulting from an incision), femoral (outer groin), umbilical (belly button), and hiatal (upper stomach)
  • The protsrusion of an organ through the wall of the compartment that contains it

Inguinal Region

  • The inguinal region is an area of the abdominal wall that extends from the ASIS to the pubic tubercle. The inguinal canal is found here, which contains the spermatic cord in the male and the round ligament of the uterus in the female.

Spermatic cord-coverings

  • These coverings result from the testes descending from the posterior abdominal wall to the scrotum during embryological development
  • The spermatic cord is the cord-like structure in males formed by the vas deferens (ductus deferens) and surrounding tissue that runs from the deep inguinal ring down to each testicle.

External Spermatic Fascia

  • The spermatic fascia is a bilayered fascia covering the testis; both layers are derived from abdominal muscle or fascia.

Cremasteric Fascia

  • The cremasteric fascia is a fascia in the scrotum. As the cremaster descends, it forms a series of loops which differ in thickness and length in different subjects.

Internal Spermatic Fascia

  • The deeper internal spermatic fascia is deep to the cremaster muscle, directly surrounds the spermatic cord and its contents, and is a continuation of the abdominal transversalis fascia.


  • The esophagus is a muscular tube connecting the throat (pharynx) with the stomach. The esophagus is about 8 inches long, and is lined by moist pink tissue called mucosa. The esophagus runs behind the windpipe (trachea) and heart, and in front of the spine.
  • Hollow mascular tube
  • Responsible for carrying food from the pharynx to the stomach
  • Runs posterior to the trachea and the heart


  • The stomach is a muscular organ located on the left side of the upper abdomen. The stomach receives food from the esophagus. As food reaches the end of the esophagus, it enters the stomach through a muscular valve called the lower esophageal sphincter. The stomach secretes acid and enzymes that digest food
  • Structure- muscle layers, regions, curvatures
  • Gastric ulcers


  • Peptic ulcers are open sores that develop on the inside lining of your stomach and the upper portion of your small intestine. The most common symptom of a peptic ulcer is stomach pain. Peptic ulcers include: Gastric ulcers that occur on the inside of the stomach

Esophageal Hiatus

  • is an opening in the diaphragm through which the esophagus and the vagus nerve pass. It is located in the right crus, one of the two tendinous structures that connect the diaphragm to the spine. Fibers of the right crus cross one another below the hiatus.

Surface Anatomy

  • Location of the esophagus and stomach within the thoracic and abdominal activities

Small Intestine

  • The small intestine (small bowel) is about 20 feet long and about an inch in diameter. Its job is to absorb most of the nutrients from what we eat and drink. Velvety tissue lines the small intestine, which is divided into the duodenum, jejunum, and ileum.
  • Main site for the chemical digestion
  • Receives bile from liver to break down (emulsify) fats
  • Receives digestive enzymes from the pancreas


  • The second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialized for the absorption by enterocytes of small nutrient molecules which have been previously digested by enzymes in the duodenum.


  • 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 be used instead of ileum.


  • The duodenum is the first part of the small intestine. It is located between the stomach and the middle part of the small intestine, or jejunum. After foods mix with stomach acid, they move into the duodenum, where they mix with bile from the gallbladder and digestive juices from the pancreas.

Large Intestine

  • The large intestine is the portion of the digestive system most responsible for absorption of water from the indigestible residue of food. The ileocecal valve of the ileum (small intestine) passes material into the large intestine at the cecum.
  • Absorption of vitamins
  • Compaction and storage of feces


  • The cecum or caecum is an pouch within the peritoneum that is considered to be the beginning of the large intestine. 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 cecum is located in the right inguinal region and is continues with the ileum at the ileal orifice.


  • The appendix is a small, pouch-like sac of tissue that is located in the first part of the colon (cecum) in the lower- right abdomen.
  • The official name of the appendix is veriform appendix, which means “worm-like appendage.” The appendix harbors bacteria.


  • Painful swelling of the appendix
  • Appendicitis is an inflammation of the appendix, a finger-shaped pouch that projects from your colon on the lower right side of your abdomen. Appendicitis causes pain in your lower right abdomen. However, in most people, pain begins around the navel and then moves.


  • Diverticulosis is when pockets called diverticula form in the walls of your digestive tract. The inner layer of your intestine pushes through weak spots in the outer lining. This pressure makes them bulge out, making little pouches. Most often it happens in your colon, the lower part of your large intestine.
  • Outpouching form along the wall of the colon, usually in the sigmoid colon
  • Due to changes in pressure with defecation


  • Diverticulitis is inflammation or infection of small pouches called diverticula that develop along the walls of the intestines. The formation of the pouches themselves is a relatively benign condition known as diverticulosis.


  • 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 mesothelium supported by a thin layer of connective tissue.
  • Allows the organ to move freely and smoothly
  • Suspends and support organs within the abdominal cavity

Visceral Peritoneum

  • Tightly adhere to a viscus

Parietal Peritoneum

  • Adhered to the inside of the abdominopelvic body wall.

Intraperitoneal Organ

  • A viscus that is completely surrounded (stomach or spleen)

Retroperitoneal Organ

  • A viscus that is positioned between body wall and peritoneum (kidneys)

Peritoneal Cavity

  • The peritoneal cavity is a potential space between the parietal peritoneum (the peritoneum that surrounds the abdominal wall) and visceral peritoneum (the peritoneum that surrounds the internal organs).

Greater Sac

  • also known as the general cavity (of the abdomen) or peritoneum of the peritoneal cavity proper, is the cavity in the abdomen that is inside the peritoneum but outside the lesser sac.

Abdominal Cavity

  • The abdominal cavity is hardly an empty space. It contains a number of crucial organs including the lower part of the esophagus, the stomach, small intestine, colon, rectum, liver, gallbladder, pancreas, spleen, kidneys, and bladder.

Lesser Sac

  • also known as the omental bursa, is the cavity in the abdomen that is formed by the lesser and greater omentum. Usually found in mammals, it is connected with the greater sac via the omental foramen (previously known as the Foramen of Winslow).

Lesser Omentum

  • The lesser omentum (small omentum or gastrohepatic omentum) is the double layer of peritoneum that extends from the liver to the lesser curvature of the stomach (hepatogastric ligament) and the first part of the duodenum (hepatoduodenal ligament).

Greater Omentum

  • The greater omentum (also the great omentum, omentum majus, gastrocolic omentum, epiploon, or, especially in animals, caul) is a large apron-like fold of visceral peritoneum that hangs down from the stomach.
  • Apron like structure that hangs down from the stomach
  • Fat laden and prevents the visceral peritoneum from adhering to the parietal peritoneum of the abdominal wall
  • Highly mobile
  • Surrounds an inflamed organ, sealing it from the other organs


  • The liver is the largest gland in the body and is vital maintaining the internal environment.
  • The liver is a large, meaty organ that sits on the right side of the belly. … The liver also detoxifies chemicals and metabolizes drugs. As it does so, the liver secretes bile that ends up back in the intestines. The liver also makes proteins important for blood clotting and other functions.

Gall bladder

  • The gallbladder is a small pouch that sits just under the liver. The gallbladder stores bile produced by the liver. After meals, the gallbladder is empty and flat, like a deflated balloon. Before a meal, the gallbladder may be full of bile and about the size of a small pear.

Biliary Tree

  • The biliary tree is a system of vessels that directs these secretions from the liver, gallbladder and pancreas through a series of ducts into the duodenum.


  • The pancreas is a leaf shaped accessory digestive gland that is positioned transversely across the posterior abdominal wall. It is involved in producing pancreatic juice, glucagon and insulin
  • The pancreas is a gland organ. It is located in the abdomen.
  • The pancreas has an endocrine function because it releases juices directly into the bloodstream, and it has an exocrine function because it releases juices into ducts. Enzymes, or digestive juices, are secreted by the pancreas into the small intestine.


  • The spleen is an organ in the upper far left part of the abdomen, to the left of the stomach.
  • The spleen plays multiple supporting roles in the body. It acts as a filter for blood as part of the immune system. Old red blood cells are recycled in the spleen, and platelets and white blood cells are stored there.


  • The foregut is the anterior part of the alimentary canal, from the mouth to the duodenum at the entrance of the bile duct. Beyond the stomach, the foregut is attached to the abdominal walls by mesentery.


  • The midgut is the portion of the embryo from which most of the intestines develop. After it bends around the superior mesenteric artery, it is called the “midgut loop”.


  • The hindgut (or epigaster) is the posterior (caudal) part of the alimentary canal. In mammals, it includes the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon and rectum. In zoology, the term hindgut refers also to the cecum and ascending colon.

Gastrointestinal Tract

  • The gastrointestinal tract is an organ system within humans and other animals which takes in food, digests it to extract and absorb energy and nutrients, and expels the remaining waste as feces. The mouth, esophagus, stomach and intestines are part of the gastrointestinal tract.

Celiac Trunk

  • Responsible for supplying oxygen-rich blood to the stomach, spleen, liver, esophagus, and also parts of the pancreas and duodenum.

Superior Mesenteric Artery

  • arises from the anterior surface of the abdominal aorta, just inferior to the origin of the celiac trunk, and supplies the intestine from the lower part of the duodenum through two-thirds of the transverse colon, as well as the pancreas.

Inferior Mesenteric Artery

  • In human anatomy, the inferior mesenteric artery, often abbreviated as IMA, is the third main branch of the abdominal aorta and arises at the level of L3, supplying the large intestine from the left colic (or splenic) flexure to the upper part of the rectum, which includes the descending colon, the sigmoid colon, and part of the rectum. Proximally, its territory of distribution overlaps (forms a watershed) with the middle colic artery, and therefore the superior mesenteric artery. The SMA and IMA anastomose via the marginal artery of the colon (artery of Drummond) and via Riolan’s arcade (also called the “meandering artery”, an arterial connection between the left colic artery and the medial colic artery). The territory of distribution of the IMA is more or less equivalent to the embryonic hindgut.

Venous Drainage

  • The systemic venous system brings deoxygenated blood from tissues and organs back to the right atrium of the heart, whereas the pulmonary venous system brings oxygenated blood from the pulmonary circulation back to the left atrium of the heart. Venous drainage, anterior view.

Portal Venous System

  • a portal venous system occurs when a capillary bed pools into another capillary bed through veins, without first going through the heart. Both capillary beds and the blood vessels that connect them are considered part of the portal venous system.
  • A portal venous system is where a capillary bed runs into another capillary bed before returning to the systemic circulation and passing through the heart.

Hepatic Portal Vein

  • is formed by the union of the superior mesenteric and the splenic veins behind the neck of the pancreas.

Portal- Systemic Anastomoses

  • Connections between the venous portal system and systemic circulation. Typically, these are very narrow quiescent connections that do not conduct significant volumes of blood.


  • Pass along the round ligament of the liver to join with superficial epigastric veins which drain into the external iliac

Posterior Abdominal Wall

  • is a complex region of anatomy. It is formed by the lumbar vertebrae, pelvic girdle, posterior abdominal muscles and their associated fascia. Major vessels, nerves and organs are located on the inner surface of the posterior abdominal wall.
  • Supports the retroperitoneal organs like he kidneys, pancreas and duodenum and also contains important neurovascular structures.

Abdominal Aorta

  • The abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta (of the thorax).

Inferior Vena Cava

  • a large vein carrying deoxygenated blood into the heart. There are two in humans, the inferior vena cava (carrying blood from the lower body) and the superior vena cava (carrying blood from the head, arms, and upper body).
  • Receives venous blood from lower limbs, abdominopelvic organs and posterior body wall.

Somatic Nerves

  • Contains sensory and motor fibers that supply the skeletal musculature and skin of the abdomen


  • The kidneys are two bean-shaped organs, each about the size of a fist. They are located just below the rib cage, one on each side of your spine.
  • Your kidneys, ureters, and bladder are part of your urinary tract. You have two kidneys that filter your blood, removing wastes and extra water to make urine.
  • They are vitally important in removing excess water, salts and waste products from body while maintaining the correct balance of nutrients and chemicals

Renal Capsule

  • The renal capsule is a tough fibrous layer surrounding the kidney and covered in a layer of perirenal fat known as the adipose capsule of kidney. The adipose capsule is sometimes included in the structure of the renal capsule. It provides some protection from trauma and damage.


  • The ureter is a tube that carries urine from the kidney to the urinary bladder. There are two ureters, one attached to each kidney. The upper half of the ureter is located in the abdomen and the lower half is located in the pelvic area. The ureter is about 10 to 12 inches long in the average adult.

Suprarenal Glands

  • are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex which produces steroid hormones and an inner medulla.