Info

Substance

Source

Function

Vitamin Bi2 (requires intrinsic factor for absorption via small intestine)

Absorbed from small intestine

DNA synthesis

Iron

Absorbed from small intestine; conserved during red blood cell destruction and made available for reuse

Hemoglobin synthesis

Folic acid

Absorbed from small intestine

DNA synthesis

Neutrophils (nu'tro-filz) have fine cytoplasmic granules that appear light purple with a combination of acid and base stains. The nucleus of an older neutrophil is lobed and consists of two to five sections (segments, so these cells are sometimes called segs) connected by thin strands of chromatin. For this reason, they are also called polymorphonuclear leukocytes. Younger neutrophils are also called bands because their nuclei are C-shaped.

Neutrophils are the first white blood cells to arrive at an infection site. These cells phagocytize bacteria, fungi, and some viruses. Neutrophils account for 54% to 62% of the leukocytes in a typical blood sample from an adult (fig. 14.9).

Eosinophils (e"o-sin'o-filz) contain coarse, uniformly sized cytoplasmic granules that stain deep red in acid stain. The nucleus usually has only two lobes

Shier-Butler-Lewis: I IV. Transport I 14. Blood I I © The McGraw-Hill

Human Anatomy and Companies, 2001

Physiology, Ninth Edition

King George III and Porphyria Variegata

Some historians blame the American Revolution on a blood disease— an abnormality of hemoglobin that afflicted King George III, who ruled England at the time. So puzzling were his symptoms that not until this century did medical researchers discover the underlying disorder, called porphyria variegata.

At age fifty, the king first experienced abdominal pain and constipation, followed by weak limbs, fever, a rapid pulse, hoarseness, and dark red urine. Next, nervous system symptoms began, including insomnia, headaches, visual problems, restlessness, delirium, convulsions, and stupor. His confused and racing thoughts, combined with his ripping off his wig and running about naked while at the peak of a fever, convinced court observers that the king was mad. Just as Parliament was debating his ability to rule, he mysteriously recovered.

But George III's plight was far from over. He suffered a relapse thirteen years later, then again three years after that. Always the symptoms appeared in the same order, beginning with abdominal pain, fever, and weakness and progressing to the nervous system symptoms. Finally, an attack in 1811 placed him in an apparently permanent stupor, and he was dethroned by the Prince of Wales. He lived for several more years, experiencing further episodes of his odd affliction.

In George III's time, physicians were permitted to do very little to the royal body, basing diagnoses on what the patient told them. Twentieth-century researchers found that George III's red urine was caused by an inborn error of metabolism. In porphyria variegata, because of the absence of an enzyme, part of the blood pigment hemoglobin, called a porphyrin ring, is routed into the urine instead of being broken down and metabolized by cells. Porphyrin builds up and attacks the nervous system, causing many of the other symptoms. Examination of the medical records of King George III's descendants reveals several of them also had symptoms of porphyria varie-gata. The underlying defect in red blood cell recycling had appeared in its various guises as different problems. ■

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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