Tissues Dr. Gerald Brasington

Tissues Histology: The study of microscopic structure of tissues. Integumentary System: The skin and its appendages. Every tissue of the body falls into one of 4 main categories: ◦ Epithelial ◦ Connective ◦ Muscle ◦ Nervous

Epithelial Tissue Distinguished by its close association of cells  epithelial cells are packed close together with little material between them. Epithelium is avascular. Epithelial tissue covers body surfaces, lines inside of body cavities and organs, and forms glands.

Epithelial tissue (continued) 3 main functions: ◦ 1. Protection ◦ 2. Control of permeability ◦ 3. Secretion of needed substances from glands

Epithelial tissue (continued) Arrangement of cells results in clumps or sheets ◦ Sheet- like: covering or lining epithelium- Covers the body and organ surfaces. ◦ Lines all hollow structures.  Often protective  form a barrier  regulates movement of substances

Epithelial tissue (continued) Clump- like  Glandular epithelium ◦ Form glands Glands- 2 types ◦ Exocrine: Secrete products into body cavities and surfaces by way of tubular ducts. ◦ Endocrine: Secretions diffuse into bloodstream for transport throughout body.  Hormones

Epithelial tissue (continued) Epithelial tissue usually has connection tissue under it. Often borders a hollow space (cavity or lumen) The side exposed to a body space  apical (free) surface. The side exposed to connective tissue is the basal surface. Basement membrane- layer of protein fibers anchor epithelial sheet to connective tissue.

Classification of epithelial tissue Cell shape ◦ Squamous- Flat with a thin nucleus ◦ Cuboidal- Cube-shaped with round nucleus near the center of the cell ◦ Columnar- Tall with an oval nucleus near the basal surface ◦ Transitional- Shape changing from round when tissue is relaxed to flat when tissue is stretched. organization (layers) ◦ Simple- One layer ◦ Stratified- Multiple layered.

Connective Tissue Arises from Mesenchyme Embryological Mesenchyme 5 types of connective tissue: ◦ Loose Connective Tissue ◦ Dense Connective Tissue ◦ Cartilage ◦ Bone ◦ Blood

Connective Tissue (Continued) General function is to connect and support the tissues and organs of the body.

Muscle Tissue Specialized cells containing molecular filaments of protein (Myosin and Actin) arranged in parallel bundles. The filaments enable the cells to shorten in length (contract). Contraction of many cells in a coordinated manner cause body movements. Also aids in temperature regulation.

Muscle Tissue (Continued) 3 types of muscle ◦ Skeletal: attached to bones; Main type; Voluntary; cells and very long & cylindrical. Striped appearance  striations. ◦ Smooth: Sheets that contribute to the walls of hollow organs  blood vessels, Stomach, Small intestines. Cells are spindle shaped, lack striations, involuntary control. ◦ Cardiac: Forms the wall of the heart. Branched, contain striations. Intercalated Discs.

Nervous Tissue Neural tissue is specialized cells that “communicate” with each other through electrochemical signals (conductivity). The cells are called Neurons. Found in brain, spinal cord, and nerves. Contain a large axon  conducts signal to other cells. Numerous, smaller dendrites  receive signals from other cells. Neuroglia: small non-conductive support cells.

The End