Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Structure of the Human Body
Tissues, Organs, Organ Systems, and Apparatuses
Organs, Organ Systems, and Apparatuses

Organs are composed of tissues. An organ is a distinct part of the body that occupies a specific position, has a characteristic shape and Structure, and performs a dedicated function. While all four types of tissue contribute to The formation of every organ, only one serves as its primary functional tissue. For instance, Nervous Tissue is the main component of the Brain, Epithelial Tissue forms the Liver, and Muscle tissue makes up Muscles. These organs also contain other tissues that perform auxiliary Functions. Epithelial tissue lines the mucous membranes of the digestive, respiratory, and urinary systems; Connective Tissue provides protective, supportive, and trophic functions; and muscle tissue helps form the walls of hollow Internal Organs, Blood and Lymphatic vessels, and glandular ducts.

Organs that share a common origin, a unified structural plan, and a collective function form an organ system. Major systems include the digestive, respiratory, urinary, reproductive, cardiovascular, and nervous systems. For example, the Digestive System develops from the primitive gut, appears as a tube with specific expansions and strictures, and carries out Digestion. The liver, Pancreas, and major Salivary Glands are outgrowths of this digestive tube and are closely connected to it. The Human Body also comprises organ apparatuses. In an apparatus, organs are grouped by a shared overall function, though they may differ in origin and structure. A prime example is The Musculoskeletal System, formed by bones and muscles of diverse origin and structure, which work together to provide support and movement. The endocrine apparatus consists of Endocrine glands (such as the pituitary, Adrenal Glands, and Thyroid Gland) of varied origin and structure that secrete BIOLOGICALLY ACTIVE SUBSTANCES, or Hormones, which regulate vital bodily functions.

Organ Systems and apparatuses together constitute a unified, integrated human Organism.

Review and Self-Assessment Questions:

1. What are the Tissues of the human body? Provide a definition and outline the tissue classifications.

2. What types of epithelial tissue do you know? List the various kinds of epithelium and provide morphological and functional descriptions for each.

3. Describe the STRUCTURE AND FUNCTIONS of blood, and state the standard numerical values that characterize blood composition.

4. List the types of muscle tissue and provide their morphological and functional characteristics.

5. What is The structure of a nerve Cell? Name its components and their respective functions.

6. What is an organ, an organ system, and an organ apparatus? Define each term and give Examples.