Overview
This lecture covers the structure, functions, locations, and types of epithelial and connective tissues in animals, focusing on their key characteristics and examples.
Epithelial Tissue
- Epithelial tissue forms the inner and outer linings of organs, cavities, and the outer layer of skin.
- It lines organ lumens and covers the surface of organs.
- Epithelial tissue also makes up glands, including exocrine (direct secretion) and endocrine (hormone into bloodstream) glands.
- There are two main forms: simple (one layer thick) and stratified (multiple layers).
- Simple epithelium is found where diffusion needs to occur, e.g., alveoli of lungs.
- Stratified epithelium is found where protection from chemical or mechanical stress is needed, e.g., esophagus.
- Epithelial cells rest on a basement membrane, a layer of fibers (like collagen) that is semipermeable.
- Epithelial tissue is avascular (no blood vessels) and receives nutrients by diffusion from underlying tissue.
- Common locations include: outer skin, lining of mouth, esophagus, GI tract, kidney tubules, blood and lymphatic vessels.
- The specific term for epithelial tissue lining blood/lymphatic vessels is endothelium.
Connective Tissue
- Connective tissue supports, connects, and separates different tissue types in the body.
- Major examples: bone, cartilage, blood, lymph, adipose (fat), membranes covering brain/spinal cord.
- Connective tissue is composed of cells, ground substance (viscous fluid), and fibers; ground substance + fibers = matrix.
- Areolar tissue binds tissues together and provides flexibility and cushioning.
- Adipose tissue (fat) cushions and stores energy but lacks fibers.
- Fibrous connective tissue has strong fibers for support and shock absorption; found in dermis, tendons, and ligaments.
- Blood is a connective tissue with a liquid matrix (plasma) and no fibers.
- Bone (osseous tissue) cells are osteocytes; matrix is hydroxyapatite (collagen + minerals).
- Hyaline cartilage cells are chondrocytes; found on joint surfaces.
Key Terms & Definitions
- Epithelial tissue — tissue forming linings and coverings throughout the body.
- Simple epithelium — one cell layer thick, for diffusion.
- Stratified epithelium — multiple cell layers, for protection.
- Basement membrane — fibrous, non-cellular support layer under epithelial cells.
- Endothelium — epithelial lining of blood and lymph vessels.
- Connective tissue — tissue providing support, connection, and separation for other tissues.
- Matrix — combination of ground substance and fibers in connective tissue.
- Areolar tissue — loose connective tissue, binds and cushions.
- Adipose tissue — fat storage connective tissue, energy and cushioning.
- Fibrous connective tissue — strong, supportive tissue with many fibers.
- Osteocyte — bone cell.
- Chondrocyte — cartilage cell.
Action Items / Next Steps
- Review locations and functions of epithelial and connective tissues.
- Memorize key terms and their definitions for upcoming assessments.