Tissues and Organization: Chapter 2 & 4

• Tissues and the respiratory system are covered in Chapter 2, pages 43-48, and Chapter 4 of the textbook.

Intro & Epithelial Tissue

• The four levels of structural organization are cell, tissue, organ, and system.
• There are four types of tissue which need to be defined.
• Epithelial tissue's structure, function, and location needs to be described.
• Epithelial tissue can be covering or glandular and must be characterized.
• Epithelial tissues are categorized as simple, stratified, squamous, cuboidal, columnar, pseudostratified, and/or transitional.

Levels of Organization

• The smallest unit of life is a cell.
• A tissue is an association of cells with the same general structure and function.
• An organ is an association of several tissue types that carry out a specific function.
• An organ system is two or more organs working together to perform a general function like digestion or movement.

4 Types of Tissue

• Epithelial tissue covers/lines exterior surfaces and internal cavities/tubes, such as skin, blood vessels, stomach lining, and intestines.
• Muscular tissue provides movement through contraction and relaxation.
• Nervous tissue is made of neurons (specialized cells) that send electrical signals along their membranes.
• Connective tissue supports and holds things together, including bone, cartilage, blood, fat, ligaments, tendons, and loose connective tissue.

Epithelial Tissue (Lining)

• Covers the body's external and internal surfaces.
• Makes up the outer surface of the skin.
• Lines most internal cavities like the stomach, throat, blood vessels, and digestive tract.
• Major functions include protection (e.g., skin and organ coverings), secretion (e.g., producing fluids/mucus in the respiratory tract), absorption of substances (e.g., stomach lining, alveoli in lungs, and blood vessels), and filtration (e.g., kidney).

General Characteristics of Epithelium

• Epithelium is a lining tissue with a free or unattached apical surface open to the outside or an internal cavity, and is fixed to a basal section attached to connective tissue.
• Lacks blood vessels, so cells absorb nutrients from the layer below.
• Cells are tightly held for protection.
• Has the ability to regenerate quickly, which is good for tissues like skin.

Categories of Epithelial Tissue

• Epithelial tissue is categorized by the number of cell layers and the shape of the cells.
• Simple epithelium has a single layer.
• Stratified epithelium has multiple layers.
• Squamous cells are flat and thin.
• Cuboidal cells are round or square.
• Columnar cells are tall.

Simple Epithelium

• Simple squamous epithelium allows for rapid absorption/diffusion and secretes lubricating substances; it is found in air sacs (alveoli) of lungs and lining of blood vessels.
• Simple cuboidal epithelium's location is the lining of kidney tubules, and its function is absorption and secretion of substances.
• Simple columnar epithelium's location is ciliated in lining bronchi and uterine tubes and smooth in the digestive tract, which allows for absorption of substances, secretes mucus and enzymes, and moves substances across the cell surface.
• Pseudostratified columnar epithelium lines the trachea and upper respiratory tract, secreting mucus and moving mucus across the surface.

Stratified Epithelium

• Stratified squamous epithelium functions to protect against abrasion; found in skin and lines the esophagus, mouth, and vagina.
• Stratified cuboidal epithelium provides protective tissue, and is found in sweat glands, salivary glands, and mammary glands.
• Stratified columnar epithelium secretes substances and provides protection, and is found in the male urethra and ducts of some glands.
• Transitional epithelium, found in the bladder, urethra, and ureters, allows urinary organs to expand and stretch.

Connective Tissue

• Connective tissue is abundant and widespread, basically anything that isn't muscle/nerve/lining tissue.
• Supports the body and helps to hold/connect body parts.
• Examples are bone for support, blood to transport nutrients, tendons and ligaments for attaching/connecting, fat for cushion/nutrient storage, cartilage for protection/support, and loose connective tissue to hold organs in place.

Characteristics of Connective Tissue

• Cells are not held closely together but spread out.
• Non-cellular material (matrix) separates the cells.
• The matrix can be solid (bone), liquid (blood), or a mesh of fibers and fluid (other connective tissue types).
• Fibers (protein chains) hold pieces together for expansion, contraction, and elasticity.

Areolar (Loose) Connective Tissue

• Lots of criss-crossing fibers.
• Lots of space/matrix/fluid.
• Has few cells (fibroblasts).
• It holds organs together.
• Strong enough to bind tissues, soft enough to provide flexibility and cushioning.

Adipose Tissue

• A special type of loose connective tissue, commonly known as fat tissue.
• Cells contain a large fat store, with the cytoplasm and organelles squashed in a corner.
• Stores fat for insulation and nutrient storage.
• Found in fat deposits around the body.

Dense (Regular) Connective Tissue

• Has tightly packed parallel fibers, sometimes in a wavy pattern.
• Located in tendons and ligaments that hold bones together and attach muscles to bones.
• Regularly arranged, long bundles of fibers make it very strong.

Cartilage

• Smooth, elastic tissue in joints.
• Contains fluid/matrix between cells to provide a smooth sliding surface.
• Elastic cartilage is found in the ears.
• Hyaline cartilage is found at the ends of bones (smooth sliding surface).
• Fibrocartilage is located between vertebrae.
• Cartilage is identified by a "cell in a bubble" (chondrocyte in a lacuna).

Bone

• Bone cells are surrounded by mineral deposits (matrix) to make the tissue hard.
• Cells are arranged in rings (looks like tree rings).
• Provides major structure and support.
• Located in bones.

Blood

• Blood is a special type of connective tissue.
• Has small and some large cells floating in a liquid.
• Made of plasma/liquid matrix.
• Transports nutrients and provides immunity.