Abdomen-Visible Human

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Module Name: a_vm1640
Module Title: Abdomen-Visible Human
Image Info: Transverse section through the abdomen
Created by: Lynn Bry
Contact Email:bryl@medicine.wustl.edu
Date: Feb 2nd, 1997 introduction=This transverse sectiion lies approximately 5cm above the umbilicus (belly button). Note the posterior location of the kidneys, and their encasement in the perirenal fat. Segments of small intestine and colon may also be seen. Small bowel can be distinguished from the colon by it's narrower bore, and smaller lumen. This particular section cuts through the ascending colon, seen on the right, the transverse colon, located in the middle, and the descending colon shown posteriorly on the left side of the body. Click on 'colon' in the key points listed below to have these features outlined in the image.

Muscles of interest include the psoas major and quadratus lumborum muscles, the erector spinae muscles of the back, and the muscles of the anterior abdominal wall: external and internal obliques, transversus abdominus, and rectus abdominus muscles.


Key points: kidney | colon | small intestine | erector spinae | psoas major | quadratus lumborum | oblique muscles | rectus abdominus |



colon: This section nicely shows the ascending, transverse, and descending colon. The ascending colon lies on the right side of the body. Of the three segments, it is the closest to the ileum, the distal region of the small intestine. The ascending colons plays an important function in retrieving solutes and water from the material entering from the ileum.

The transverse colon lies in the anterior region of the section, while the descending colon lies more laterally on the left side of the body.

descending_aorta: The aorta is the largest vessel of the body. The abdominal aorta gives rise to branches supplying blood to the abdominal organs. These branches include the celiac trunk which supplies blood to the stomach, liver, spleen, and pancreas, the superior mesenteric artery, which supplies the small intestine and part of the colon, and the inferior mesenteric artery which supplies blood to the left side of the colon.

erector_spinae: The erector spinae muscles run the length of the vertebral column. They allow the bending and rotation of the spine. They are also the most common cause of muscle spasms and lower back pain.

fashia: Note the subcutaneous fatty tissue beneath the skin. This layer of fat and connective tissue helps insulate the body. It is also metabolized for energy during periods of starvation.

inferior_vena_cava: The inferior vena cava transports blood from the lower extremitites to the right atrium of the heart.

intercostal_muscle: The intercostal muscles lie between the ribs. They elevate the ribs during inspiration. This action allows the lungs to expand within the thoracic cavity.

kidney: This section shows both kidneys. These organs filter the blood, removing toxins and wastes. Approximately 20-25% of the blood pumped to the body goes to the kidneys. They filter an average of 180L of plasma each day. The kidney play an important role in regulating blood pressure, and also secrete erythropoetin, a hormone which stimulates the bone marrow to produce more red blood cells.

latissimus_dorsi: The latissimus dorsi muscle is one of the primary muscle of the back. It extends in a large traingle from the 6th thoracic vertebra (a point roughly between the shoulder blades) to the sacrum, and laterally to its attachment on the humerus of the arm. The muscle adducts the shoulders, done by military recruits standing at attention, and also extends the shoulder joint, an action used to raise the arm in front of the body.

oblique_muscles: The external and internal oblique muscles, in addition to the innermost transversus abdominus muscle, form the three layers of the anterior abdominal wall. The rectus abdominus muscle forms the central region of the anterior abdomen.

The muscle fiblers of the oblique muscles run perpendicular to one another, at a 45 degree angle to the transverse plane. They compress the abdomen when straining, and are heavily used for sit-ups.

perirenal_fat: A layer of fat surrounds the kidney. The fats helps protect the kidneys.

psoas_major: The psoas major muscle flexes the hip joint, as happens when bringing the knees into the chest. Lower in the pelvis is joins with fibers of the iliacus to form the iliopsoas muscle.

quadratus_lumborum: This quadratus lumborum muscle originates on the 12th floating rib, and from the transverse arms of the lumbar vertebrae. The muscle inserts on the iliac crest of the hip. Its contraction is used to bend the body from side to side.

rectus_abdominus: The rectus abdominus muscle comprises the central region of the anterior abdominal wall. (It receives heavy usage during sit-ups.) The muscle has many segments, which produces the 'tortise shell' abdomen in body builders. A tendinous sheath covers the rectus abdominus. This sheath is made of the aponeuroses of the three adjacent muscles on either side of the antierior abodomen - the external oblique, internal oblique, and transversus abdominus muscles.

retroperitoneal_fat: This layer of body fat lies outside of the peritoneal cavity.

rib: The 10-12th false ribs may be seen in this section. These ribs do not articulate (attach) anteriorly to the sternum. The 10th rib articulates with the cartilage of the 7th rib, while the 11th and 12th ribs have no anterior attachments (floating ribs).

small_intestine: The inner surface of the small intestine contains many convoluted into finger-like projections called villi. The increased surface area helps the body absorb and process digested foods. The small intestine is divided into three regions, the duodenum which follows the stomach, jejunum, and ileum. Each segment has specific functions regarding digestion.

Most of the carbohydrates from a meal are absorbed in the duodenum. This segment of intestine also plays an important role in the absorption of minerals such as iron and calcium, and vitamins such as vitamin D. Brunner's glands in the duodenum secrete bicarbonate ion which help neutralize the acid of the stomach. Also with the duodenum, the common bile duct and the pancreatic duct release digestive enzymes and bile into the lumen of the small intestine.

Bile is a thick green fluid secreted by the liver and stored in the gall bladder. It contains bile acids which help the gut absorb fats. Bilirubin - a breakdown product of heme (associated with hemoglobin in red blood cells) gives bile its color.

The jejunum follows the duodenum and continues absorbing sugars and amino acids from digested protein.

The ileum is the most distal segemnt of the gut. This region plays an important role in abosrbing fats and fat-soluble vitamins such as vitamins A, E, and K.

spinal_cord: The spinal cord can be seen within the vertebral column - note it's size relative to the surrounding vertebral column. The spinal cord is part of the central nervous system - CNS. Nerves in the skin, muscles and organs communicate with nerves in the spinal cord to send messages to the brain.

transversus_abdominus: The transversus abdominus is the innermost of the three overlapping muscles comprising the anterior abdominal wall (see oblique muscles and rectus abdominus). Its fibers run parallel to the transverse axis of the body. Note how the anterior origin of the muscle inserts on the interior of the rib cage.

vertebra: The vertebral column runs from the neck to the pelvis (hips). It includes the 7 cervical vertebrae of the neck, 12 thoracic vertebrae which articulate posteriorly with the ribs, 5 lumbar vertebrae of the lower back, the sacrum which consists of 5 fused bones, and is responsible for transmitting the weight of the body to the hips, and the coccyx - 2-4 fused bones which form the vestigal remains of a tail. The column protects the spinal cord, the small greyish oval present within the bone.

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