Lecture 3: Connective and Epithelial Tissues PDF

Lecture 3 Connective (& epithelial) tissues Epithelial Cells & Tissues Structure: one or more layers of cells that are located at the surfaces that cover the body or individual organs, and they line the inner surfaces of the tubular and hollow structures within the body. Function: sp...

Lecture 3 Connective (& epithelial) tissues Epithelial Cells & Tissues Structure: one or more layers of cells that are located at the surfaces that cover the body or individual organs, and they line the inner surfaces of the tubular and hollow structures within the body. Function: specialized for the selective secretion and absorption of ions and organic molecules, and for protection. Types of epithelium: cell organization (structure) different sizes and it shapes so makes it look thicker Types of epithelium: tissue function (1) exchange (2) transportation Types of epithelium: tissue function (3) Ciliatedd (4) Secretory (3) protection  Connective Tissue Cells Function: specialized to connect, anchor, Blood and support the structures of the body. Areolar Bone Skin Adipose Cartilage Tendons & ligaments Connective tissue components Ef elastin  Ground substance Protein core Glycosaminoglycans Proteins Proteoglycans ↓ ↳ type of glycoprotein large polysaccharide Carbohydrates Oxygen/ Nitrogen Water Glycoproteins Protein General connect tissue cells Macrophages engulfs and - digests invaders Fibroblasts part of connective matrix · Protein fibers Collagen · elastic fiber ·  Elastic fibers cross uf linked · lysol oxidase fibrillin elastin - scaffold for elastin ? helps w/elasticity -  Marfan's syndrome - L · can expand 1 3 times.  Collagen hierarchical structure tropocollagen Lysyl oxidase (LOX) crosslinks fibrillar collagen What surrounds the cells? The immediate environment that surrounds each individual cell in the body is the extracellular fluid and extracellular matrix (ECM). ECM consists of a mixture of proteins, polysaccharides, and in some cases, minerals. The proteins of the extracellular matrix consist of fibers—ropelike collagen fibers and rubberband-like elastin fibers—and a mixture of nonfibrous proteins that contain carbohydrate. The matrix serves two general functions: 1. It provides a scaffold for cellular attachments 2. Transmits information, in the form of chemical messengers, to the cells to help regulate their activity, migration, growth, and differentiation.  Blood Areolar Bone Skin Adipose Cartilage Tendons & ligaments Connective tissue types Erector pili muscles Skin as an organ (muscle tissue) Epidermis (epithelium) Dermis (loose irregular connective tissue) Sweat gland – exocrine glands Sensory nerve endings (nervous tissue) Adipose tissue (weird connective tissue)  Cartilage - space that houses the site Mostly avascular Chondrocytes - secreting collagen cells? Dense network of very fine collagen II fibrils and fibres (60% dry mass) Cartilage Types: ↓ Cartilage Hyaline cartilage found on most joint surfaces - high tension ~ blood supply ~ no nerves or surrounded by perichondrium Fibrocartilage - more collagen · Elastic cartilage · firm but flexible · more elastic fibers Tendons & ligaments Dense regular connective tissue Connect muscle to bone (tendons) and bones to bones (ligaments) · cells that make it up are fibroblasts Tendons & ligaments Hierarchical organization of collage into larger and larger fiber bundles Collagen is crimped provides physical separation in case of damage · CT (tendon)remodeling responds to mechanical stimulus · fibroblast CT (tendon)remodeling CT (tendon)remodeling Chemical stimuli Mechanical stimuli - growth factor (ligand) exercise  force Upregulate collagen gene expression Produces & secretes collagen Mechanical properties of CT directions opposite & twisting in The mechanical properties of tissues can be determined by applying a force to the tissue and measuring how much it deforms. Mechanical properties of CT Mechanical properties of CT increase length = force exerting more Mechanical properties of CT Mechanical properties of CT  Mechanical properties of CT material high stiffness : strong Yield strength – force at which it permanently deforms low stiffness : weak material Absolute strength absolute strength – force at which it breaks - Stiffness Stifness (k) (k) – gradient of the force (F) vs extension curve (x) K (N/m) = F (N)/x (m) Change in length or extension (m) Stress (N/m2) Strain stress = force/area strain = extension/length modulus = stress/ strain  Mechanical properties of CT Yield strength – force at which it permanently deforms Stress (N/m2 or Pa) Absolute↑ strength – force at which it breaks unitless Modulus (Pa) Modulus (Pa)– normalized stiffness - Strain Change in length or extension (m)  Collagen mechanical properties tropocollagen very strong quite stiff Lysyl oxidase (LOX) crosslinks good in tension fibrillar collagen  Cartilage mechanical properties and shear good in compression · Dense network of very fine collagen II fibrils and fibres (60% dry mass) Collagen orientation reflects resistance to compression or shear Lots of proteoglycans and water (strong in compression) Tendons mechanics I giga pascal Tendons are extensible Store and return elastic strain energy