Visible Human, Coronal Section/Anterior Thorax

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Module Name: a_vmY1649
Module Title: Visible Human, Coronal Section/Anterior Thorax
Image Info: Computer generated from gross transverse sections.
Created by: Lynn Bry
Date: Feb 7th, 1997


Key points: lung | left ventricle | right ventricle | diaphragm | stomach | liver | pectoralis major |

Introduction: This coronal section illustrates the anterior region of the thorax and abdomen. The pectoralis major muscles are evident at the top of the image. Within the thoracic cavity lie the heart and lungs. The heart lies within the mediastinum, and is surrounded by a thick fibrous membrane, the pericardium. This section cuts primarily through the right ventricle.

Abdomenal organs include the liver, stomach, and parts of the ascending and descending colon. Note the location of the ascending colon beneath the liver. The diaphragm, the primary muscle of inspriation, separates the thoracic cavity from the abdomen.


colon: Parts of the ascending and descending colon may be seen in this section. The ascending colon lies on the right side of the body. Of the three segments, it is the closest to the ileum or distal region of the small intestine. The ascending colons plays an important function in retrieving solutes and water from the fecal material passed from the small intestine.

costal_cartilage: The costal cartilages join the seven true ribs to the sternum, and the first three false ribs to the 7th true rib. The cartilagenous connections enhance the mobility and elasticity of the thoracic cage. This mobility allows the lungs to expand within the thorax during inspiration.

diaphragm: The diaphragm is the primary muscle of inspiration. It forms a dome which separates the thoracic cavity from the abdomen. The muscle attaches to the base of the pleural membranes which surround the lungs. When it contracts it pulls the lungs "down" allowing them to fill with air.

The muscle is innervated by the phrenic nerve which originates from the 3-5th cervical ganglia of the spinal cord ("C3-4-5 keeps the diaphargm alive"). The muscles is under both voluntary and involuntary control.

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.

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

left_ventricle: A small region of the apex of the heart's left ventricle lies adjacent to the right ventricle. The left ventricle pumps oxygenated blood from the lungs to the rest of the body. Blood enters via the left atrium and exits through the aortic value to the aorta, the largest artery in the body. You can feel the left ventricle in action by taking the pulse, or by placing a hand on the rib cage, just beneath the breast on the L. side. The site with the beating heart can best be felt is called the point of maximal impulse (PMI).

liver: The liver plays many important roles in the body. Nutrient rich blood returning from the gastrointestinal tract enters the liver via the portal circulation. The liver processes absorbed compounds, fats and cholesterol in particular, and detoxifies many substances that could be harmful to the body. In addition, the organ secretes bile, a thick greenish fluid important for the proper absorption of fats and fat-soluble vitamins such as vitamins A, E, and K.

lung: The section shows the anterior aspect of the right and left lungs. Note their location with respect to the mediastinum which contains the heart. The red color of the lungs comes from the great amount of blood in the pulmonary vasculature. In the lungs red blood cells exchange carbon dioxide for oxygen.

mesentary: The mesentaries connect the intestines and internal organs of the abdomen. In addition, these structures contain the blood vessels and lymphatics that enter the intestines to receive nutrients absorbed by the gut. The mesentaries eries are made of fatty and connective tissue, and result from a complex folding of the lining of the abodomen (the peritoneum) during development.

pectoralis_major: The pectoralis major muscles cover the anterior wall of the chest. These muscles help adduct, extend and medially rotate the arm (bring the arm to your side, raise it in front of you, and rotate it towards the body).

pericardium: The heart is surrounded by a thick fibrous membrane - the pericardium. A small amount of fluid exists in the space between the beating heart and this membrane. Should the amount of fluid increase, due to infections (pericarditis) or rupture of the heart muscle as can happen with serious damage to the heart muscle, a life-threatening condition called cardiac tamponade can occur. Due to the limited space, the increased fluid prevents the heart from filling with blood and pumping it to the body.

rib: The rib bones form the protective cage surrounding the lungs and the heart. Note that the ribs do not lie in a plane parallel to the ground. This transverse section cuts through many ribs.

All 12 ribs articulate posteriorly with the 12 thoracic vertebrae of the spinal column. Anteriorly the 7 true ribs articulate with the sternum or breast bone via attachments referred to as costal cartilages. The cartilagenous connections allow some mobility in the rib cage, necessary for the lungs to exapand properly during inspriation. Beneath the 7 true ribs lie 5 false ribs. The first three false ribs articulate with the 7th true rib. They do not directly attach to the sternum. The lasttwo false ribs ribs - floating ribs do not have any anterior connections.

right_ventricle: The right ventricle pumps venous/deoxygenated blood to the lungs. The right ventricle is more anteriorly placed. It thus occupies more space in this section than the adjacent left ventricle.

sternum: The sternum is the 'breast bone.' The seven true ribs of the rib cage articulate with the sternum (thus they are 'true'). The 8th, 9th, and 10th false ribs join only with the seventh true rib. The last two false ribs 11 & 12 are floating ribs. They do not articulate anteriorly with any elements of the rib cage.

stomach: The stomach has three layers of smooth muscle which mechanically grind ingested food as hydrochloric acid (HCl) and enzymes such as pepsin break complex carbohydrates (sugars), fats and proteins into their componenets. Note the convoluted interior surface of the stomach. These ridges are reffered to as rugae.

An epithlielium lines the interior of the stomach (gastric epithelium). This epithelium contains many cell types, and is organized into units called gastric pits. Parietal cells secrete HCl while neck and surface mucus cells secrete mucus to protect the stomach from its own acid. Chief cells, located at the bottom of the gastric pits, secrete enzymes important in the breakdown of foodstuffs.

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