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

BIOLOGY

CHAPTER 1. BIOLOGICAL FOUNDATIONS OF HUMAN VITAL ACTIVITY

1.4. ONTOGENETIC LEVEL OF LIFE ORGANIZATION

1.4.3. Biology of Individual Development

Tumor Growth

Cells of various Tissues and Organs constantly multiply, a process associated with growth, development, and regeneration, which is strictly controlled by regulatory systems (neurohumoral and immune). However, under certain pathological conditions, intensive Cell multiplication (proliferation) begins in a particular organ, leading to tissue overgrowth and tumor formation. A tumor is also referred to as a blastoma. Both malignant and benign tumors are distinguished.

Benign tumors generally grow slowly, do not destroy surrounding tissues or invade them, but merely push them aside (expansive growth), and they do not metastasize. Their margins are clearly defined, and they are sometimes enclosed externally by a capsule. The cells of benign tissues differ very little from healthy cells. A benign tumor originating from Connective Tissue is called a fibroma, while one originating from Muscle tissue is called a myoma.

Malignant tumors lack clear borders, grow rapidly, invade surrounding tissues, and destroy them (infiltrative growth), and are capable of metastasis. The Essence of metastasis is that malignant tumor cells can be carried by the bloodstream and Lymph to other organs. By multiplying at the new site, they can give rise to secondary tumor nodules. Malignant tumors originating from Epithelial Tissues are called Cancer or carcinoma, while those from connective tissue are called Sarcoma. The process of normal cell transformation into a cancerous cell (malignization) is not yet fully understood. Cancer cells differ from normal cells by a complex of traits; the primary one among them is the capacity for unrestricted, uncontrolled division, leading to uninhibited tumor growth.

Factors that cause tumor formation are called blastomogenic or carcinogenic. There are three groups of Carcinogenic Factors: physical, chemical, and biological. Physical factors include ionizing radiation (gamma and X-rays, electrons, protons, etc.) and ultraviolet rays; Chemical factors include coal and petroleum Processing products, exhaust gases, and tars; biological factors include Oncogenic Viruses. Oncogenic viruses are Introduction/7.html">RNA-containing Viruses belonging to the retrovirus family. A characteristic feature of Retroviruses is the presence of the enzyme Reverse Transcriptase (revertase), which ensures the METABOLISM/31.html">Transcription of Genetic information from RNA to DNA. Oncogenic viruses cause oncogenic diseases in animals, particularly in birds. In humans, oncogenic viruses cause adult T-cell leukemia. From a genetic perspective, The Emergence of malignant tumors is associated with somatic Mutations. Tumor cells possess specific Antigens that are alien to the given Organism, which is why The Immune System perceives them as genetically foreign and destroys them. When immune responses are weakened, the organism fails to destroy them.