Biological Tissue Types and Human Organ Functions

Epithelial Tissue and Glandular Functions

Epithelial tissue covers and protects surfaces from external or internal body cavities. Key types include:

• Mucous: Covers the oral cavity, the pharynx, and other internal passages.
• Endothelium: The inside lining of blood vessels.
• The epidermis: The outer layer of the skin.
• Glandular epithelium: Tissue forming glands, which has the function of secreting substances.

Classification of Glands

• Exocrine glands: Produce substances discharged to the outside or inside the body cavities.
• Endocrine glands: Produce hormones that are discharged into the blood.
• Mixed glands: Act as both exocrine and endocrine glands at the same time.

Connective Tissue and Its Specialized Forms

Connective tissue is formed by cells immersed in a very specialized intercellular substance that contains fibers (collagen and others). There are different types:

• Connective tissue: Found in other tissues and organs, holding them together.
• Adipose tissue: Characterized by cells called adipocytes, which are full of fat reserves for the protection of certain organs and lipid insulation.
• Cartilage: Formed by chondrocytes, which produce the intercellular substance.
• Bone tissue: Formed by osteocytes; the intercellular substance produces a solid cellular matrix composed of mineral salts, calcium, and phosphorus.

Muscle Tissue Types and Contraction

Muscle tissue is formed by elongated cells (muscle fibers) containing protein fibrils (actin and myosin). These proteins cause the muscles to contract and relax. There are three types of muscle tissue:

• Smooth muscle: Formed by elongated cells with one nucleus; characterized by involuntary contraction.
• Striated muscle tissue: Composed of cells with many nuclei; it is called so because of the alternating light and dark bands that look like stretch marks; characterized by voluntary contraction.
• Cardiac muscle tissue: Cells with a striated aspect that together form a single core network; characterized by involuntary contraction.

Nervous Tissue and Sensory Transmission

Nervous tissue detects variations in the external and internal environment and transmits commands. It consists of two primary cell types:

• Neurons: Formed by the cell body, dendrites, and axons; their function is to transmit nerve impulses.
• Glia cells: Cells that accompany neurons; they protect and feed the neurons.

Organs, Organography, and Physiology

Organs are structures formed by different tissues that are associated to perform a specific function.

• Organography: The science that studies the structure and morphology of organs.
• Physiology: The science that studies the functions of the organs.