Surface Anatomy Assignment 8th November 2012 Lungs The lungs extend from the diaphragm to just slightly superior to the clavicles and lie against the ribs anteriorly and posteriorly. The base of the lung is concave and fits over the convex area of the diaphragm. The narrow superior portion of the lung is called the apex. The apices of the lungs extend about three centimetres above the medial third of the clavicles. The medial surface of the lung is called the hilum. The hilus of the lungs is through which the bronchi, pulmonary blood vessels and nerves enter and exit.
Anteriorly, they lie at the level of the costal cartilages 3-4, which is at the level of T5-7. The inferior margins of the lungs are: T-6 mid-clavicular line, T-8 at the mid-axilla, and T-10 posteriorly. Each lung is contained and protected within a double-layered membrane called the pleural membrane. The superficial layer, known as the parietal pleura affects the anterior margins of the lungs on either side. On the right, it is deep to the right side of the sternum between the second and fourth costal cartilages inferiolaterally to the level of the deep surface of the sixth right intercostal cartilage.
On the left, deep to the sternum near the midline, inferiorly between the levels of costal cartilages 2 and 4, displaced laterally and more obliquely than left side to a point about 3 centimetres lateral to the left sternal edge at the upper margin of the sixth costal cartilage. The space created by the lateral deviation of pleura and lung on the left side is termed the cardiac notch. Heart The heart rests on the diaphragm, near the midline of the thoracic cavity in the mediastinum. An important and readily palpable landmark for the heart is the sternal angle.
The sternal angle is the junction between the manubrium and the body of the sternum, and corresponds to the second costal cartilage. The apex of the heart, which is formed by the tip of the left ventricle, rests on the diaphragm at the 5th intercostal space in the midclavicular line, or 8-9 centimetres from the midsternal line. It is important to note that the apex is not the most superior part of of the heart. The lower right corner of the heart is to is found on the right 6th or 7th sternocostal junction.
The base of the heart is the most superior portion of the heart and is predominantly retrosternal, located between the 2nd and 3rd costal spaces. Other margins of the heart include the anterior surface, which is deep to the sternum and the ribs, and the interior surface between the apex and and the right border which rests on the diaphragm. Liver The liver is almost completely covered by visceral peritoneum. The greater part of the liver lies under cover of the lower ribs and their cartilages, but in the epigastric fossa it comes in contact with the abdominal wall.
The liver resides in the upper right quadrant of the abdominal cavity. The exact position of the liver varies according to the posture of the body. In the erect posture of the adult male, the edge of the liver projects about 1 centimetre below the lower margin of the right costal cartilages, and its inferior margin can often be felt in this situation if the abdominal wall is thin. In the supine position the liver recedes above the margin of the ribs and cannot then be detected by the finger; in the prone position it falls forward and is then generally palpable in a patient with loose and lax abdominal walls.
Its position varies with the respiratory movements; during a deep inspiration it descends below the ribs; in expiration it is raised. Pressure from without, as in tight lacing, by compressing the lower part of the chest, displaces the liver considerably, its anterior edge frequently extending as low as the crest of the ilium. Again its position varies greatly with the state of the stomach and intestines; when these are empty the liver descends, when they are distended it is pushed upward. Stomach The stomach is found in the left upper part of the abdominal cavity.
The shape of the stomach is constantly undergoing alteration; it is affected by the particular phase of the process of gastric digestion, by the state of the surrounding viscera, and by the amount and character of its contents. Its position also varies with that of the body so that it is difficult to indicate it on the surface with any degree of accuracy. The anterior surface of stomach is related to the left lobe of the liver, the anterior abdominal wall, and the distal transverse colon. The posterior surface of the stomach is related to the left side of the diaphragm, the spleen, the left kidney, and the pancreas.
The greater curvature of the stomach starts at the left of the heart and runs from the opening along the left border of the body and the inferior border of the pylorus. The lesser curvature starts at the right of the heart and runs a short distance along the right border of the body and the superior border of the pylorus. (Note: Pylorus is the sphincter through which the stomach communicates with the duodenum. ) Spleen The spleen is located in the left hypochondrium and lies between the 9th and 11th ribs.
The superior surface of the spleen is smooth and convex. It conforms to the concave surface of the diaphragm. Small and Large Intestines The coils of the small intestine lie mainly in the umbilical and hypogastric regions. The ascending colon passes upward through the right lumbar region, lateral to the right lateral line. The transverse colon crosses the abdomen on the confines of the umbilical and epigastric regions, its lower border being on a level slightly above the umbilicus, its upper border just below the greater curvature of the stomach.
The descending colon courses down through the left lumbar region, lateral to the left lateral line, as far as the iliac crest. Kidneys The paired kidneys are located just above the waist between the peritoneum and the posterior wall of the abdomen. The kidneys sit between the lower levels of the thoracic spine and the upper regions of the lumbar spine. Specifically, the right kidney has its upper edge opposite the 11th thoracic spine and the lower edge of the 11th rib.
Its lower edge is opposite the upper edges of L-3 spine and vertebral body and about 4 centimetres above the highest point of the crest of the ileum. The left kidney is usually 1. 25 centimetres higher, but being a little longer than the right, its lower limit may not be quite that much higher. The kidney is slightly lower in women and children than in men. Generally speaking, the left kidney is higher (highest border T-11 lowest border L-2) whereas the right kidney is lower (highest border T-12 lowest border L-3).
The right kidney is also less enclosed by the rib cage, because of the presence of right lobe of liver above it, therefore pushing it down. Urinary Bladder The urinary bladder is a hollow organ that is situated in the pelvic cavity posterior to the pubis. It sits in the musculature of the pelvic floor when empty. When full, or distended, it rises toward the umbilicus, carrying the peritoneal fold with it so as to leave a space of 2. 5 to 5 centimetres between it and the top of the pubis. In males it is directly anterior to the rectum; in females it is anterior to the vagina and inferior to the uterus.