ZOOLOGY STUDY GUIDE - Ye. O. Nevedomska - 2013

LECTURE 5. TISSUE LEVEL OF ORGANIZATION OF LIVING MATTER. ANIMAL TISSUES

1. Characteristics of animal tissues

1.2. Tissues of the internal environment

Tissues of the Internal Environment make up various Organs and form the body's internal environment. A common feature of this group of tissues is the presence of a well-developed Extracellular matrix and a high capacity for continuous renewal and regeneration after injury.

Tissues of the internal environment include:

✵ fluid tissues — Blood, Lymph;

✵ Connective Tissues — loose, dense fibrous, adipose, bone, Cartilage, etc.

Let us consider the structural features and Functions of the various types of tissues of the internal environment:

✵ Blood consists of Cells (formed elements) — erythrocytes, leukocytes, platelets (40-45%) and a liquid extracellular matrix — plasma (55-60%). Erythrocytes provide gas transport, leukocytes and platelets are responsible for the body's protective reactions, and plasma transports nutrients (trophic function) and Metabolic waste products.

✵ Lymph consists of cells — leukocytes (lymphocytes) and a liquid extracellular matrix — plasma. Lymph is a clear, yellowish fluid formed from interstitial fluid that collects in blind-ended lymphatic capillaries originating in very narrow intercellular spaces. Leukocytes (lymphocytes) play an important role in protecting the body against infection and developing Immunity, while plasma transports nutrients, typically Lipids (trophic function).

✵ Loose fibrous tissue consists of sparsely distributed cells and extracellular matrix in the form of ground substance and fibers. The fibers can be: thin, straight, arranged in bundles (Collagen fibers), which determine the strength of the Connective Tissue, and thick (elastic fibers), which give the tissue elasticity; the star-shaped cells of loose connective tissue are called fibroblasts; those capable of amoeboid movement are called histiocytes, or macrophages (capable of phagocytosis). It is found in all organs, accompanies Blood and Lymphatic vessels, and fills the spaces between Internal Organs.

✵ Dense fibrous tissue contains A large number of closely packed collagen fibers. Tendons and ligaments are made of this tissue. It performs a supportive function.

✵ Adipose tissue is located under the dermis and around some organs, protecting them from mechanical damage. It stores reserve nutrients (lipid droplets), making adipose tissue the body's energy depot. Subcutaneous adipose tissue acts as a thermal insulating layer. It can also produce metabolic Water, which is crucial for desert-dwelling animals (e.g., camels).

✵ Cartilage tissue consists of rounded cells (chondrocytes) and a dense extracellular matrix rich in organic substances, making it elastic and resilient. It performs a supportive function.

There are Three types of cartilage:

1) hyaline cartilage covers the articular surfaces of bones and forms the cartilage of the Larynx (except the epiglottis), Trachea, Bronchi, and Ribs (Fig. 8);

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Fig. 8. Hyaline cartilage:

1 — chondrocytes with nuclei; 2 — extracellular matrix.

2) fibrocartilage, which is found in intervertebral discs and articular surfaces;

3) elastic cartilage, located in the epiglottis and auricle.

✵ Bone tissue consists of cells and a hard extracellular matrix. Star-shaped cells — osteocytes — are interconnected by a large number of protoplasmic processes.

The extracellular matrix contains:

- organic substances (mainly the protein ossein) that provide elasticity to the bone tissue;

The vertebrate Skeleton is composed of bone tissue.

Thus, tissues of the internal environment perform a variety of functions: protective, trophic (transport of nutrients), transport (transport of gases and metabolic waste), supportive, and storage; they maintain the relative constancy of the internal environment — Homeostasis (from the Greek homoios — same, stasis — position).

Tissues of the internal environment are capable of continuous renewal and recovery after injury, possessing the highest capacity for regeneration. With age, the extracellular matrix of connective tissues contains less and less water and becomes coarser.