Chapter 5 (4)

• Glands are cells or organs that secrete substances for use elsewhere in the body or release them for elimination from the body. They are usually composed of epithelial tissue in a connective tissue framework and capsule.
• Secretion: product useful to the body. Excretion: waste product.
• Exocrine glands: They maintain their contact with the surface of epithelium by way of a duct. These surfaces can be external (e.g., sweat, tear glands) or internal (e.g., pancreas, salivary glands)
• Endocrine glands: They have no ducts; and secrete hormones directly into the blood.
• Hormones are chemical messengers that stimulate cells elsewhere in the body. Examples: thyroid, adrenal, and pituitary glands.
• Some organs have both endocrine and exocrine functions. Examples: liver, gonads, pancreas.
• Unicellular glands are found in an epithelium that is predominantly non-secretory and they can be exocrine or endocrine. Examples: mucus-secreting goblet cells in the trachea or endocrine cells of the stomach.
• In the Exocrine Gland Structure theres the Capsule(the connective tissue covering of exocrine gland), the Stroma(connective tissue framework of the gland), and the Parenchyma(cells that perform the tasks of synthesis and secretion).
• Classification of glands in the Exocrine Gland Structure: Duct shape and Gland shape.
• Duct shape gland structure has two types: Simple (unbranched) and Compound (branched)
• Gland shape gland structure has 3 types: Tubular: narrow secretory portion. Acinar: secretory cells form dilated sac (acinus or alveolus). Tubuloacinar (tubuloalveolar): both tubular and acinar portions.
• There are 3 types of secretions: 1. Serous glands that produce thin, watery secretions e.g. Perspiration, milk, tears, and digestive juices. 2. Mucous glands that produce glycoprotein, mucin, which absorbs water to form mucus i.e. Goblet cells are unicellular mucous glands. 3. Mixed glands that contain both serous and mucous cell types and produce a mixture of the two types of secretions.
• Tissue growth means increasing the number of cells or the size of existing cells. i.e. Hyperplasia—growth through cell multiplication, Hypertrophy—enlargement of preexisting cells(this happens during exercise), and Neoplasia—development of a tumor that can be benign or malignant because its abnormal and nonfunctional tissue (neoplasm).
• Tissues can change types within certain limits through Differentiation(the development of more specialized form and function by unspecialized tissue) or Metaplasia(the changing from one type of mature tissue to another)
• Stem cells are undifferentiated cells that do not have a specific function yet. However, they possess the potential to evolve into one or more types of specialized functional cells.
• Developmental plasticity is the ability of a stem cell to give rise to a diversity of mature cell types.
• Damaged tissues can be repaired in two ways: Regeneration(the replacement of dead or damaged cells by the same type of cell as before) and Fibrosis: the replacement of damaged cells with scar tissue.
• Tissue Degeneration and Death include Atrophy(the shrinkage of tissue due to loss of cell size or number), Necrosis(pathological tissue death due to trauma, toxins, or infections), and Apoptosis(programmed cell death).
• Infarction(sudden death of tissue when blood supply is cut off) and Gangrene(tissue necrosis due to insufficient blood supply and usually involves infection) are types of necrosis.