Case Press 104
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Transcript of Case Press 104
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Anatomy and Physiology
In humans, the trachea divides into the two main bronchi that enter the roots of the
lungs. The bronchi continue to divide within the lung, and after multiple divisions, giverise to bronchioles. The bronchial tree continues branching until it reaches the level of
terminal bronchioles, which lead to alveolar sacs. Alveolar sacs are made up of clusters
of alveoli, like individual grapes within a bunch. The individual alveoli are tightly
wrapped in blood vessels and it is here that gas exchange actually occurs.
Deoxygenated blood from the heart is pumped through the pulmonary artery to the
lungs, where oxygen diffuses into blood and is exchanged for carbon dioxide in the
hemoglobin of the erythrocytes. The oxygen-rich blood returns to the heart via the
pulmonary veins to be pumped back into systemic circulation
Human lungs are located in two cavities on either side of the heart. Though similar
in appearance, the two are not identical. Both are separated into lobes by fissures, with
three lobes on the right and two on the left. The lobes are further divided into segments
and then into lobules, hexagonal divisions of the lungs that are the smallest subdivision
visible to the naked eye. The connective tissue that divides lobules is often blackened in
smokers. The medial border of the right lung is nearly vertical, while the left lung
contains a cardiac notch . The cardiac notch is a concave impression molded to
accommodate the shape of the heart. Lungs are to a certain extent 'overbuilt' and have
a tremendous reserve volume as compared to the oxygen exchange requirements when
at rest. Such excess capacity is one of the reasons that individuals can smoke for years
without having a noticeable decrease in lung function while still or moving slowly; in
situations like these only a small portion of the lungs are actually perfused with blood for
gas exchange. As oxygen requirements increase due to exercise, a greater volume of
the lungs is perfused, allowing the body to match its CO2/O2 exchange requirements.
Additionally, due to the excess capacity, it is possible for humans to live with only one
lung, with the other compensating for its loss.
The environment of the lung is very moist, which makes it hospitable for bacteria.
Many respiratory illnesses are the result of bacterial or viral infection of the lungs.
Inflammation of the lungs is known as pneumonia; inflammation of the
pleura surrounding the lungs is known as pleurisy.
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In addition to their function in respiration, the lungs also:
Alter the pH of blood by facilitating alterations in the partial pressure of Carbon
dioxide Filter out small blood clots formed in veins Filter out gas micro-bubbles occurring in
the venous blood stream such as those created after scuba diving during
decompression
Influence the concentration of some biologic substances and drugs used in medicine
in blood
Convert angiotensin I to angiotensin II by the action of angiotensin-converting
enzyme
May serve as a layer of soft, shock-absorbent protection for the heart, which thelungs flank and nearly enclose.
Immunoglobulin-A is secreted in the bronchial secretion and protects against
respiratory infections.
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Anatomy and physiology
In humans, the kidneys are located in the abdominal cavity, and lie in
a retroperitoneal position. There are two, one on each side of the spine. The asymmetry
within the abdominal cavity caused by the liver typically results in the right kidney being
slightly lower than the left, and left kidney being located slightly more medial than theright. The left kidney is approximately at the vertebral level T12 to L3, and the right
slightly lower. The right kidney sits just below the diaphragm and posterior to the liver,
the left below the diaphragm and posterior to the spleen. Resting on top of each kidney
is an adrenal gland. The upper (cranial) parts of the kidneys are partially protected by
the eleventh and twelfth ribs, and each whole kidney and adrenal gland are surrounded
by two layers of fat (the perirenal and pararenal fat) and the renal fascia. Each adult
kidney weighs between 125 and 170 grams in males and between 115 and 155 grams
in females. The left kidney is typically slightly larger than the right.
The kidney has a bean-shaped structure, each kidney has concave and
convex surfaces. The concave surface, the renal helium, is the point at which the renal
artery enters the organ, and the renal vein and ureter leave. The kidney is surrounded
by tough fibrous tissue, the renal capsule, which is itself surrounded by perinephric fat,
renal fascia (of Gerota) and paranephric. The anterior (front) border of these tissues is
the peritoneum, while the posterior (rear) border is the transversalis fascia.
The superior border of the right kidney is adjacent to the liver; and the spleen, for the
left border. Therefore, both move down on inhalation.
The kidney is approximately 1114 cm in length, 6 cm wide and 4 cm thick.
The substance, or parenchyma, of the kidney is divided into two major
structures: superficial is the renal cortex and deep is the renal medulla. Grossly, these
structures take the shape of 8 to 18 cone-shaped renal lobes, each containing renal
cortex surrounding a portion of medulla called a renal pyramid. Between the renal
pyramids are projections of cortex called renal columns. Nephrons, the urine-producing
functional structures of the kidney, span the cortex and medulla. The initial filtering
portion of a nephron is the renal corpuscle, located in the cortex, which is followed by
a renal tubule that passes from the cortex deep into the medullary pyramids. Part of the
renal cortex, a medullary ray is a collection of renal tubules that drain into a
single collecting duct. The tip, or papilla, of each pyramid empties urine into a minor
calyx, minor calyces empty into major calyx, and major calyces empty into the renal
pelvis, which becomes the ureter.