MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedonyuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 6. THE PROCESS OF RESPIRATION AND ITS PATHOLOGY

DISEASES OF THE RESPIRATORY SYSTEM

HYPOXIA

Hypoxia, or oxygen starvation, is a typical pathological process that occurs As a result of inadequate tissue oxygen supply or impaired oxygen utilization by tissues.

Like any other pathological process, hypoxia goes through two Selection/3.html">Stages of development: compensation and decompensation. Initially, thanks to compensatory and adaptive reactions, a normal supply of oxygen to the tissues is maintained, despite impaired oxygen intake. Upon exhaustion of these adaptive mechanisms, the stage of decompensation, or actual oxygen starvation, develops.

During hypoxia, the following compensatory and adaptive reactions develop:

1. Increased pulmonary ventilation, which occurs reflexively in response to changes in Blood chemical composition: the accumulation of CO2 and hydrogen ions.

2. Enhanced Blood Circulation, aimed at improving Blood supply to tissues. Under conditions of hypoxia, there is also a redistribution of blood favoring the primary blood supply to vital Organs (the Brain, The Heart) at the expense of reduced Blood Supply to the Skin, Muscles, and intestines.

3. An increase in the number of red Blood Cells and Hemoglobin, initially due to the release of blood from blood depots, and subsequently through enhanced erythropoiesis in the Bone Marrow.

4. Enhanced ability of hemoglobin molecules to bind oxygen in the Lungs and release it to tissues.

Oxygen deficiency causes tissue energy starvation, which underlies all changes in hypoxia. METABOLISM is disrupted and products of incomplete oxidation accumulate, a significant number of which are toxic. In The Liver and muscles, for example, The amount of Glycogen decreases, and glucose is not completely oxidized. The resulting lactic acid shifts the acid-base balance toward acidosis.

Synthetic processes are reduced. Intermediate products of Protein metabolism accumulate, and a negative nitrogen balance is established.

The Nervous system is the most sensitive to the effects of hypoxia. Euphoria occurs even before the onset of symptoms of oxygen starvation. This state is characterized by emotional and motor excitation, a feeling of personal strength, behavioral inadequacy, or, conversely, a loss of interest in the surroundings. Severe symptoms of oxygen starvation include convulsions and loss of consciousness.

In terms of sensitivity to oxygen deficiency, the heart Muscle ranks second after Nervous Tissue. Myocardial excitability, conductivity, and contractility are impaired, which clinically manifests as tachycardia and arrhythmia. Heart failure, as well as decreased vascular tone, leads to hypotension and general Circulatory Disorders. The breathing rhythm changes, often acquiring the character of Cheyne-Stokes Respiration (see "DISORDERS OF EXTERNAL Respiration"), and congestive phenomena develop in the lungs. The MOTOR FUNCTION OF the digestive tract is suppressed, and the secretion of The Stomach, intestines, and Pancreas is reduced.

Primary polyuria is replaced by impaired filtration capacity of the Kidneys.

In severe cases of hypoxia, body Temperature drops, which is explained by decreased metabolism and thermoregulation disorders.