Tissues and Histology - Key Terms
Cell Division, Cancer, and Tissue Basics
- Cytokinesis — division of the cytosol and organelles equally between two new daughter cells.
- Apoptosis — programmed cell death.
- Mutations — changes in DNA due to mistakes in copying DNA.
- Cancer — uncontrolled cell division resulting in a tumor.
- Metastasis — cancer cells' ability to move throughout the body.
- Histology — the study of tissues.
- 4 types of tissue — Epithelial, connective, muscle and nervous.
- Epithelial tissue — covers and lines body surfaces and cavities. Cells are tightly packed together, have an apical and basal surface, are avascular, are innervated, and are highly regenerative.
- Connective tissues — connect structures, bind, support and protect other tissues and allow for transportation of substances throughout the body.
- Muscle tissue — allow for contraction.
- Nervous tissues — generate, send, and receive messages.
- Extracellular matrix (ECM) — composed of substances in a liquid, thick gel, or solid that surround the cells of a tissue. Consists of ground substance and fibers.
- Epithelial tissues — have a free surface called the apical surface and a basal surface to which they are bound.
- Naming epithelial tissue — based on the number of cell layers and the shape of the cells. (for example, simple squamous would be one cell layer thick and the cells would be flattened.)
- Simple epithelia — one cell layer thick.
- Stratified epithelia — more than one cell layer thick.
- Squamous — flat.
- Cuboidal — cube shaped.
- Columnar — tall and elongated.
- Goblet cell — a specialized type of columnar cell that secretes mucous.
- Simple squamous epithelium — one cell layer thick, flattened cells. One location would be the alveoli (air sacs) of the lungs.
Epithelial Tissue Types, Structure, and Locations (continued)
- Stratified squamous epithelium — found in areas of abrasion/friction. Keratinized stratified squamous epithelium is found on the outside layer of the skin.
- Simple columnar epithelium — one cell layer thick of column shaped cells. One location would be the small intestine.
- Pseudostratified ciliated columnar epithelium — found in the trachea.
- Transitional epithelium — several layers of epithelial cells and the underlying basal lamina found in the organs of the urinary system; cells can change shape from dome shaped to squamous when the bladder is stretched.
- Endocrine glands — secrete their products (usually hormones) directly into the bloodstream.
- Exocrine glands — secrete their products (ex: sweat) through an epithelium-lined duct.
- Merocrine secretion — products are packaged in secretory vesicles for release by exocytosis.
- Holocrine secretion — product accumulates in cytosol and is released when cell ruptures and dies (ex: oil.)
- Connective tissue proper — also known as general connective tissue. It is widely distributed in the body. Types include loose, dense, reticular and adipose. Cells found in this tissue include fibroblasts, adipocytes, mast cells and phagocytes.
- Phagocytes — cells that ingest foreign cells, dead cells, and other cellular debris by phagocytosis.
- Adipose tissue — fat tissue — consists of fat-storing adipocytes that are the major energy reserve in the body. This tissue also provides insulation, warmth, shock absorption, and protection.
- Cartilage — the three types are hyaline cartilage, fibrocartilage and elastic cartilage. The embryonic skeleton is composed of hyaline cartilage, the vertebral discs are fibrocartilage, and the tissue found the external ear is elastic cartilage (very stretchy.)
- Bone tissue — provides protection and support. The extracellular matrix is inorganic calcium phosphate crystals, making bone one of the hardest substances in the body.
Blood, Muscle, and Skeletal Tissues
- Erythrocytes — red blood cells — these cells transport oxygen through the body.
- Skeletal muscle tissue — found attached to the skeleton. It is voluntary muscle and allows for movement.
- Cardiac muscle tissue — is found only in the heart and is involuntary.
- Smooth muscle tissue — found in digestive organs, uterus, etc. Involuntary, uninucleate, and non-striated.
Nervous Tissue and Support Cells
- Neurons — cells capable of sending and receiving electrical messages.
- Neuroglial cells — support cells of the nervous tissue that are capable of mitosis (unlike the neurons.)
- True membranes — serous and synovial.
- Serous membranes — fold over themselves giving the appearance of two layers; the outer parietal layer is in contact with the body wall, while the inner visceral layer covers the organ within the body cavity.
- Synovial membranes — line the cavities surrounding freely moveable joints such as the knee or shoulder.
- Membrane-like structures — mucous and cutaneous membranes.
- Mucous membranes — also called mucosae — line all body passages as components of the walls of hollow organs that open to the outside of the body.
- Cutaneous membrane — refers to the skin.
- Stem cells — immature cells capable of replacing worn epithelial cells of the skin and digestive tract.
- Gap junctions — small pores formed by protein channels between adjacent cells that allow small substances to flow freely between each cell’s cytoplasm.
- Tight junctions — also known as occluding junctions, hold cells closely together such that space between is impermeable to movement of macromolecules.
- Tissue repair — process of wound healing; dead and damaged cells are removed and replaced with new cells or tissues.
- Membrane — thin sheets of one or more tissues that line a body surface or cavity.